diff --git a/src/configure.ml b/src/configure.ml
index eb2f2698..f188c8b9 100644
--- a/src/configure.ml
+++ b/src/configure.ml
@@ -24,11 +24,16 @@ let () =
  (foreign_stubs
   (language c)
   (names config util unicode point rect list hashtable event
-         gdi_keyboard gdi_backend gdi_target gdi_window gdi_context
-         qtz_keyboard qtz_backend qtz_target qtz_window qtz_context
-         x11_keysym x11_keyboard x11_backend x11_target x11_window x11_context
-         wl_backend wl_target wl_window wl_context
-         window pixmap image_interpolation filters context transform draw_instr
+         gdi_keyboard gdi_backend gdi_target gdi_window
+         gdi_sw_context gdi_hw_context
+         qtz_keyboard qtz_backend qtz_target qtz_window
+         qtz_sw_context qtz_hw_context
+         x11_keysym x11_keyboard x11_backend x11_target x11_window
+         x11_sw_context x11_hw_context
+         wl_backend wl_target wl_window
+         wl_sw_context wl_hw_context
+         window pixmap image_interpolation filters transform draw_instr
+         sw_context hw_context context
          font_desc gdi_font qtz_font unx_font font
          gdi_impexp qtz_impexp unx_impexp impexp
          path arc path2d polygon polygonize
diff --git a/src/dune.inc b/src/dune.inc
index 52bfefba..927d083b 100644
--- a/src/dune.inc
+++ b/src/dune.inc
@@ -9,11 +9,16 @@
  (foreign_stubs
   (language c)
   (names config util unicode point rect list hashtable event
-         gdi_keyboard gdi_backend gdi_target gdi_window gdi_context
-         qtz_keyboard qtz_backend qtz_target qtz_window qtz_context
-         x11_keysym x11_keyboard x11_backend x11_target x11_window x11_context
-         wl_backend wl_target wl_window wl_context
-         window pixmap image_interpolation filters context transform draw_instr
+         gdi_keyboard gdi_backend gdi_target gdi_window
+         gdi_sw_context gdi_hw_context
+         qtz_keyboard qtz_backend qtz_target qtz_window
+         qtz_sw_context qtz_hw_context
+         x11_keysym x11_keyboard x11_backend x11_target x11_window
+         x11_sw_context x11_hw_context
+         wl_backend wl_target wl_window
+         wl_sw_context wl_hw_context
+         window pixmap image_interpolation filters transform draw_instr
+         sw_context hw_context context
          font_desc gdi_font qtz_font unx_font font
          gdi_impexp qtz_impexp unx_impexp impexp
          path arc path2d polygon polygonize
diff --git a/src/implem/config.c b/src/implem/config.c
index 0fcbd89d..adc347e2 100644
--- a/src/implem/config.c
+++ b/src/implem/config.c
@@ -8,17 +8,18 @@
 /*                                                                        */
 /**************************************************************************/
 
+#include <stdbool.h>
 #include <assert.h>
 
 #include "config.h"
 
-static impl_type_t impl_type = IMPL_NONE;
+static impl_type_t
+_impl_type = IMPL_NONE;
 
 void
 set_impl_type(
   impl_type_t it)
 {
-  assert(it != IMPL_CANVAS);
 #ifndef HAS_GDI
   assert(it != IMPL_GDI);
 #endif
@@ -31,17 +32,26 @@ set_impl_type(
 #ifndef HAS_WAYLAND
   assert(it != IMPL_WAYLAND);
 #endif
-  impl_type = it;
+  _impl_type = it;
 }
 
 impl_type_t
-get_impl_type()
+get_impl_type(
+  void)
 {
-  return impl_type;
+  return _impl_type;
+}
+
+bool
+has_hardware_accel(
+  void)
+{
+  return false;
 }
 
 os_type_t
-get_os_type()
+get_os_type(
+  void)
 {
 #if defined(_WIN32) || defined(_WIN64)
   return OS_WIN32;
diff --git a/src/implem/config.h b/src/implem/config.h
index aa0e80cb..06100200 100644
--- a/src/implem/config.h
+++ b/src/implem/config.h
@@ -23,11 +23,10 @@ typedef enum os_type_t {
 
 typedef enum impl_type_t {
   IMPL_NONE    = 0,
-  IMPL_CANVAS  = 1,
-  IMPL_GDI     = 2,
-  IMPL_QUARTZ  = 3,
-  IMPL_X11     = 4,
-  IMPL_WAYLAND = 5
+  IMPL_GDI     = 1,
+  IMPL_QUARTZ  = 2,
+  IMPL_X11     = 3,
+  IMPL_WAYLAND = 4
 } impl_type_t;
 
 #define switch_IMPL() switch (get_impl_type())
@@ -59,9 +58,30 @@ typedef enum impl_type_t {
 #define default_fail() default: assert(!"Missing implementation"); break
 #define default_ignore() default: break
 
-void set_impl_type(impl_type_t it);
-impl_type_t get_impl_type();
+#ifdef HAS_ACCEL
+#define switch_ACCEL() switch (has_hardware_accel())
+#define case_HW(s) case true: { s; } break
+#define case_SW(s) case false: { s; } break
+#else
+#define switch_ACCEL()
+#define case_HW(s)
+#define case_SW(s) s
+#endif
+
+void
+set_impl_type(
+  impl_type_t it);
+
+impl_type_t
+get_impl_type(
+  void);
+
+bool
+has_hardware_accel(
+  void);
 
-os_type_t get_os_type();
+os_type_t
+get_os_type(
+  void);
 
 #endif /* __CONFIG_H */
diff --git a/src/implem/context.c b/src/implem/context.c
index c7373414..6a50e7dd 100644
--- a/src/implem/context.c
+++ b/src/implem/context.c
@@ -17,31 +17,19 @@
 #include "target.h"
 #include "pixmap.h"
 #include "color.h"
-#include "context.h"
-#include "context_internal.h"
 
-#include "list.h"
 #include "rect.h"
 #include "polygon.h"
-#include "state.h" // for shadow_t
 #include "transform.h"
 #include "draw_style.h"
-#include "draw_instr.h"
-#include "poly_render.h"
-#include "impexp.h"
+#include "list.h"
+#include "state.h" // for shadow_t
 
-#ifdef HAS_GDI
-#include "gdi/gdi_context.h"
-#endif
-#ifdef HAS_QUARTZ
-#include "quartz/qtz_context.h"
-#endif
-#ifdef HAS_X11
-#include "x11/x11_context.h"
-#endif
-#ifdef HAS_WAYLAND
-#include "wayland/wl_context.h"
+#ifdef HAS_ACCEL
+#include "hw_context.h"
 #endif
+#include "sw_context.h"
+#include "context_internal.h"
 
 context_t *
 context_create(
@@ -51,25 +39,10 @@ context_create(
   assert(width > 0);
   assert(height > 0);
 
-  color_t_ *data = (color_t_ *)calloc(width * height, sizeof(color_t_));
-  if (data == NULL) {
-    return NULL;
+  switch_ACCEL() {
+    case_HW(return (context_t *)hw_context_create(width, height));
+    case_SW(return (context_t *)sw_context_create(width, height));
   }
-
-  context_t *c = (context_t *)calloc(1, sizeof(context_t));
-  if (c == NULL) {
-    free(data);
-    return NULL;
-  }
-
-  c->offscreen = true;
-  c->data = data;
-  c->width = width;
-  c->height = height;
-
-  c->clip_region = pixmap_null();
-
-  return c;
 }
 
 context_t *
@@ -79,23 +52,10 @@ context_create_from_pixmap(
   assert(pixmap != NULL);
   assert(pixmap_valid(*pixmap) == true);
 
-  context_t *c = (context_t *)calloc(1, sizeof(context_t));
-  if (c == NULL) {
-    return NULL;
+  switch_ACCEL() {
+    case_HW(return (context_t *)hw_context_create_from_pixmap(pixmap));
+    case_SW(return (context_t *)sw_context_create_from_pixmap(pixmap));
   }
-
-  c->offscreen = true;
-  c->data = pixmap->data;
-  c->width = pixmap->width;
-  c->height = pixmap->height;
-
-  c->clip_region = pixmap_null();
-
-  pixmap->data = NULL;
-  pixmap->width = 0;
-  pixmap->height = 0;
-
-  return c;
 }
 
 context_t *
@@ -108,26 +68,12 @@ context_create_onscreen(
   assert(width > 0);
   assert(height > 0);
 
-  context_t *c = NULL;
-  switch_IMPL() {
-    case_GDI(c = (context_t *)gdi_context_create((gdi_target_t *)target,
-                                                 width, height));
-    case_QUARTZ(c = (context_t *)qtz_context_create((qtz_target_t *)target,
-                                                    width, height));
-    case_X11(c = (context_t *)x11_context_create((x11_target_t *)target,
-                                                 width, height));
-    case_WAYLAND(c = (context_t *)wl_context_create((wl_target_t *)target,
-                                                    width, height));
-    default_fail();
+  switch_ACCEL() {
+    case_HW(
+      return (context_t *)hw_context_create_onscreen(target, width, height));
+    case_SW(
+      return (context_t *)sw_context_create_onscreen(target, width, height));
   }
-  if (c == NULL) {
-    return NULL;
-  }
-  c->offscreen = false;
-
-  c->clip_region = pixmap_null();
-
-  return c;
 }
 
 void
@@ -135,47 +81,12 @@ context_destroy(
   context_t *c)
 {
   assert(c != NULL);
-  assert(c->data != NULL);
-
-  if (pixmap_valid(c->clip_region) == true) {
-    pixmap_destroy(c->clip_region);
-  }
-
-  if (c->offscreen == true) {
-    free(c->data);
-    free(c);
-  } else {
-    switch_IMPL() {
-      case_GDI(gdi_context_destroy((gdi_context_t *)c));
-      case_QUARTZ(qtz_context_destroy((qtz_context_t *)c));
-      case_X11(x11_context_destroy((x11_context_t *)c));
-      case_WAYLAND(wl_context_destroy((wl_context_t *)c));
-      default_fail();
-    }
-  }
-}
-
-void
-_context_copy_to_buffer(
-  context_t *c,
-  color_t_ *data,
-  int32_t width,
-  int32_t height)
-{
-  assert(c != NULL);
-  assert(c->data != NULL);
   assert(c->width > 0);
   assert(c->height > 0);
-  assert(data != NULL);
-  assert(width > 0);
-  assert(height > 0);
 
-  uint32_t min_width = width < c->width ? width : c->width;
-  uint32_t min_height = height < c->height ? height : c->height;
-  for (size_t i = 0; i < min_height; ++i) {
-    for (size_t j = 0; j < min_width; ++j) {
-      data[i * width + j] = c->data[i * c->width + j];
-    }
+  switch_ACCEL() {
+    case_HW(hw_context_destroy((hw_context_t *)c));
+    case_SW(sw_context_destroy((sw_context_t *)c));
   }
 }
 
@@ -186,58 +97,12 @@ context_resize(
   int32_t height)
 {
   assert(c != NULL);
-  assert(c->data != NULL);
   assert(c->width > 0);
   assert(c->height > 0);
 
-  if ((width <= 0) || (height <= 0)) {
-    return false;
-  }
-
-  if ((width == c->width) && (height == c->height)) {
-    return true;
-  }
-
-  if (pixmap_valid(c->clip_region)) {
-    pixmap_destroy(c->clip_region);
-  }
-
-// TODO: fill extra data with background color
-
-  if (c->offscreen == true) {
-
-    color_t_ *data = (color_t_ *)calloc(width * height, sizeof(color_t_));
-    if (data == NULL) {
-      return false;
-    }
-
-    _context_copy_to_buffer(c, data, width, height);
-
-    free(c->data);
-
-    c->data = data;
-    c->width = width;
-    c->height = height;
-
-    return true;
-
-  } else {
-
-    bool result = false;
-
-    switch_IMPL() {
-      case_GDI(result =
-               gdi_context_resize((gdi_context_t *)c, width, height));
-      case_QUARTZ(result =
-                  qtz_context_resize((qtz_context_t *)c, width, height));
-      case_X11(result =
-               x11_context_resize((x11_context_t *)c, width, height));
-      case_WAYLAND(result =
-                   wl_context_resize((wl_context_t *)c, width, height));
-      default_fail();
-    }
-
-    return result;
+  switch_ACCEL() {
+    case_HW(return hw_context_resize((hw_context_t *)c, width, height));
+    case_SW(return sw_context_resize((sw_context_t *)c, width, height));
   }
 }
 
@@ -247,61 +112,15 @@ context_present(
 {
   assert(c != NULL);
   assert(c->offscreen == false);
-  assert(c->data != NULL);
   assert(c->width > 0);
   assert(c->height > 0);
 
-  switch_IMPL() {
-    case_GDI(gdi_context_present((gdi_context_t *)c));
-    case_QUARTZ(qtz_context_present((qtz_context_t *)c));
-    case_X11(x11_context_present((x11_context_t *)c));
-    case_WAYLAND(wl_context_present((wl_context_t *)c));
-    default_fail();
+  switch_ACCEL() {
+    case_HW(hw_context_present((hw_context_t *)c));
+    case_SW(sw_context_present((sw_context_t *)c));
   }
 }
 
-// Direct access to the context pixels
-// Do NOT free the data pointer !
-static pixmap_t
-_context_get_raw_pixmap(
-  context_t *c)
-{
-  assert(c != NULL);
-  assert(c->data != NULL);
-  assert(c->width > 0);
-  assert(c->height > 0);
-
-  return pixmap(c->width, c->height, c->data);
-}
-
-
-
-static void
-_context_clip_fill_instr(
-  context_t *c,
-  const path_fill_instr_t *instr,
-  const transform_t *transform)
-{
-  assert(c != NULL);
-  assert(pixmap_valid(c->clip_region) == true);
-  assert(instr != NULL);
-  assert(instr->poly != NULL);
-  assert(transform != NULL);
-
-  draw_style_t white = (draw_style_t){ .type = DRAW_STYLE_COLOR,
-                                       .content.color = color_white };
-  shadow_t noshadow = (shadow_t){
-    .offset_x = 0, .offset_y = 0, .blur = 0,
-    .color = color_transparent_black };
-
-// TODO: could store bounding box with polygon
-  rect_t bbox = rect(point(0.0, 0.0),
-                     point((double)c->width, (double)c->height));
-
-  poly_render(&(c->clip_region), instr->poly, &bbox, white, 1.0, &noshadow,
-              ONE_MINUS_SRC, NULL, instr->non_zero, transform);
-}
-
 bool
 context_clip(
   context_t *c,
@@ -312,34 +131,10 @@ context_clip(
   assert(clip_path != NULL);
   assert(transform != NULL);
 
-  if ((pixmap_valid(c->clip_region) == true) &&
-      ((c->clip_region.width != c->width) ||
-       (c->clip_region.height != c->height))) {
-    pixmap_destroy(c->clip_region);
-  }
-
-  if (pixmap_valid(c->clip_region) == false) {
-    c->clip_region = pixmap(c->width, c->height, NULL);
-    if (pixmap_valid(c->clip_region) == false) {
-      return false;
-    }
-  }
-
-  pixmap_clear(c->clip_region);
-
-  list_iterator_t *it = list_get_iterator(clip_path);
-  if (it == NULL) {
-    return false;
-  }
-
-  path_fill_instr_t *instr = NULL;
-  while ((instr = (path_fill_instr_t *)list_iterator_next(it)) != NULL) {
-    _context_clip_fill_instr(c, instr, transform);
+  switch_ACCEL() {
+    case_HW(return hw_context_clip((hw_context_t *)c, clip_path, transform));
+    case_SW(return sw_context_clip((sw_context_t *)c, clip_path, transform));
   }
-
-  list_free_iterator(it);
-
-  return true;
 }
 
 void
@@ -348,13 +143,12 @@ context_clear_clip(
 {
   assert(c != NULL);
 
-  if (pixmap_valid(c->clip_region) == true) {
-    pixmap_destroy(c->clip_region);
+  switch_ACCEL() {
+    case_HW(hw_context_clear_clip((hw_context_t *)c));
+    case_SW(sw_context_clear_clip((sw_context_t *)c));
   }
 }
 
-
-
 void
 context_render_polygon(
   context_t *c,
@@ -367,12 +161,21 @@ context_render_polygon(
   bool non_zero,
   const transform_t *transform)
 {
-  pixmap_t pm = pixmap(c->width, c->height, c->data);
-  poly_render(&pm, p, bbox, draw_style, global_alpha, shadow, compose_op,
-              &(c->clip_region), non_zero, transform);
-}
-
+  assert(c != NULL);
+  assert(p != NULL);
+  assert(bbox != NULL);
+  assert(shadow != NULL);
+  assert(transform != NULL);
 
+  switch_ACCEL() {
+    case_HW(hw_context_render_polygon((hw_context_t *)c, p, bbox,
+                                      draw_style, global_alpha, shadow,
+                                      compose_op, non_zero, transform));
+    case_SW(sw_context_render_polygon((sw_context_t *)c, p, bbox,
+                                      draw_style, global_alpha, shadow,
+                                      compose_op, non_zero, transform));
+  }
+}
 
 void
 context_blit(
@@ -384,7 +187,6 @@ context_blit(
   int32_t sy,
   int32_t width,
   int32_t height,
-
   double global_alpha,
   const shadow_t *shadow,
   composite_operation_t compose_op,
@@ -392,96 +194,19 @@ context_blit(
 {
   assert(dc != NULL);
   assert(sc != NULL);
+  assert(shadow != NULL);
+  assert(transform != NULL);
 
-  bool draw_shadows =
-    (shadow->blur > 0.0 ||
-     shadow->offset_x != 0.0 || shadow->offset_y != 0.0) &&
-    compose_op != COPY && shadow->color.a != 0;
-
-  const pixmap_t sp = _context_get_raw_pixmap((context_t *)sc);
-  pixmap_t dp = _context_get_raw_pixmap(dc);
-
-// TODO: global_alpha ?
-  if ((transform_is_pure_translation(transform) == true) &&
-      (draw_shadows == false)) {
-
-    double tx = 0.0, ty = 0.0;
-    transform_extract_translation(transform, &tx, &ty);
-
-    int32_t lo_x = max(dx + (int32_t)tx, 0);
-    int32_t hi_x = min(dx + (int32_t)tx + width, dc->width); // canvas wd
-    int32_t lo_y = max(dy + (int32_t)ty, 0);
-    int32_t hi_y = min(dy + (int32_t)ty + height, dc->height); //canvas ht
-
-    for (int32_t i = lo_x; i < hi_x; i++) {
-      for (int32_t j = lo_y; j < hi_y; j++) {
-
-        int32_t uvx = i + sx - dx - (int32_t)tx;
-        int32_t uvy = j + sy - dy - (int32_t)ty;
-        if (uvx < 0 || uvx >= sc->width || // canvas wd
-            uvy < 0 || uvy >= sc->height) { // canvas ht
-          continue;
-        }
-
-        color_t_ fill_color = pixmap_at(sp, uvy, uvx);
-        int draw_alpha = fill_color.a;
-        if (pixmap_valid(dc->clip_region) == true) {
-          draw_alpha *= 255 - pixmap_at(dc->clip_region, j, i).a;
-          draw_alpha /= 255;
-        }
-
-        pixmap_at(dp, j, i) =
-          comp_compose(fill_color, pixmap_at(dp, j, i),
-                       draw_alpha, compose_op);
-      }
-    }
-
-  } else {
-
-    draw_style_t draw_style =
-      (draw_style_t){ .type = DRAW_STYLE_PIXMAP, .content.pixmap = &sp };
-
-    polygon_t *p = polygon_create(8, 1);
-    if (p == NULL) {
-      return;
-    }
-
-    point_t p1 = point((double)dx, (double)dy);
-    point_t p2 = point((double)(dx + width), (double)dy);
-    point_t p3 = point((double)(dx + width), (double)(dy + height));
-    point_t p4 = point((double)dx, (double)(dy + height));
-
-    transform_apply(transform, &p1);
-    transform_apply(transform, &p2);
-    transform_apply(transform, &p3);
-    transform_apply(transform, &p4);
-
-    polygon_add_point(p, p1);
-    polygon_add_point(p, p2);
-    polygon_add_point(p, p3);
-    polygon_add_point(p, p4);
-    polygon_end_subpoly(p, true);
-
-    rect_t bbox = rect(point(min4(p1.x, p2.x, p3.x, p4.x),
-                             min4(p1.y, p2.y, p3.y, p4.y)),
-                       point(max4(p1.x, p2.x, p3.x, p4.x),
-                             max4(p1.y, p2.y, p3.y, p4.y)));
-
-    transform_t *temp_transform = transform_copy(transform);
-    transform_translate(temp_transform, dx - sx, dy - sy);
-
-    pixmap_t pm = _context_get_raw_pixmap(dc);
-    poly_render(&pm, p, &bbox, draw_style, global_alpha, shadow, compose_op,
-                &(dc->clip_region), false, temp_transform);
-
-    transform_destroy(temp_transform);
-
-    polygon_destroy(p);
+  switch_ACCEL() {
+    case_HW(hw_context_blit((hw_context_t *)dc, dx, dy,
+                            (hw_context_t *)sc, sx, sy, width, height,
+                            global_alpha, shadow, compose_op, transform));
+    case_SW(sw_context_blit((sw_context_t *)dc, dx, dy,
+                            (sw_context_t *)sc, sx, sy, width, height,
+                            global_alpha, shadow, compose_op, transform));
   }
 }
 
-
-
 color_t_
 context_get_pixel(
   const context_t *c,
@@ -490,16 +215,10 @@ context_get_pixel(
 {
   assert(c != NULL);
 
-  color_t_ color = color_black;
-
-  const pixmap_t pm = _context_get_raw_pixmap((context_t *)c);
-  if (pixmap_valid(pm) == true) {
-    if ((x >= 0) && (x < pm.width) && (y >= 0) && (y < pm.height)) {
-      color = pixmap_at(pm, y, x);
-    }
+  switch_ACCEL() {
+    case_HW(return hw_context_get_pixel((hw_context_t *)c, x, y));
+    case_SW(return sw_context_get_pixel((sw_context_t *)c, x, y));
   }
-
-  return color;
 }
 
 void
@@ -511,11 +230,9 @@ context_put_pixel(
 {
   assert(c != NULL);
 
-  pixmap_t pm = _context_get_raw_pixmap((context_t *)c);
-  if (pixmap_valid(pm) == true) {
-    if ((x >= 0) && (x < pm.width) && (y >= 0) && (y < pm.height)) {
-      pixmap_at(pm, y, x) = color;
-    }
+  switch_ACCEL() {
+    case_HW(hw_context_put_pixel((hw_context_t *)c, x, y, color));
+    case_SW(sw_context_put_pixel((sw_context_t *)c, x, y, color));
   }
 }
 
@@ -527,17 +244,14 @@ context_get_pixmap(
   int32_t width,
   int32_t height)
 {
-  assert(context != NULL);
-
-  pixmap_t dp = pixmap_null();
-  const pixmap_t sp = _context_get_raw_pixmap((context_t *)c);
-  if (pixmap_valid(sp) == true) {
-    dp = pixmap(width, height, NULL);
-    if (pixmap_valid(dp) == true) {
-      pixmap_blit(&dp, 0, 0, &sp, sx, sy, width, height);
-    }
+  assert(c != NULL);
+
+  switch_ACCEL() {
+    case_HW(return hw_context_get_pixmap((hw_context_t *)c,
+                                         sx, sy, width, height));
+    case_SW(return sw_context_get_pixmap((sw_context_t *)c,
+                                         sx, sy, width, height));
   }
-  return dp;
 }
 
 void
@@ -555,9 +269,11 @@ context_put_pixmap(
   assert(sp != NULL);
   assert(pixmap_valid(*sp) == true);
 
-  pixmap_t dp = _context_get_raw_pixmap(c);
-  if (pixmap_valid(dp) == true) {
-    pixmap_blit(&dp, dx, dy, sp, sx, sy, width, height);
+  switch_ACCEL() {
+    case_HW(hw_context_put_pixmap((hw_context_t *)c, dx, dy,
+                                  sp, sx, sy, width, height));
+    case_SW(sw_context_put_pixmap((sw_context_t *)c, dx, dy,
+                                  sp, sx, sy, width, height));
   }
 }
 
@@ -569,11 +285,10 @@ context_export_png(
   assert(c != NULL);
   assert(filename != NULL);
 
-  const pixmap_t pm = _context_get_raw_pixmap((context_t *)c);
-  if (pixmap_valid(pm) == false) {
-    return false;
+  switch_ACCEL() {
+    case_HW(return hw_context_export_png((hw_context_t *)c, filename));
+    case_SW(return sw_context_export_png((sw_context_t *)c, filename));
   }
-  return impexp_export_png(&pm, filename);
 }
 
 bool
@@ -586,9 +301,8 @@ context_import_png(
   assert(c != NULL);
   assert(filename != NULL);
 
-  pixmap_t pm = _context_get_raw_pixmap(c);
-  if (pixmap_valid(pm) == false) {
-    return false;
+  switch_ACCEL() {
+    case_HW(return hw_context_import_png((hw_context_t *)c, x, y, filename));
+    case_SW(return sw_context_import_png((sw_context_t *)c, x, y, filename));
   }
-  return impexp_import_png(&pm, x, y, filename);
 }
diff --git a/src/implem/context.h b/src/implem/context.h
index cc79c524..875bd975 100644
--- a/src/implem/context.h
+++ b/src/implem/context.h
@@ -17,12 +17,12 @@
 #include "target.h"
 #include "pixmap.h"
 
-//#include "list.h"
-//#include "rect.h"
+#include "rect.h"
 #include "polygon.h"
-#include "state.h"
 #include "transform.h"
 #include "draw_style.h"
+#include "list.h"
+#include "state.h" // for shadow_t
 
 typedef struct context_t context_t;
 
@@ -59,8 +59,6 @@ void
 context_present(
   context_t *c);
 
-
-
 bool
 context_clip(
   context_t *c,
@@ -83,8 +81,6 @@ context_render_polygon(
   bool non_zero,
   const transform_t *transform);
 
-
-
 void
 context_blit(
   context_t *dc,
@@ -95,14 +91,11 @@ context_blit(
   int32_t sy,
   int32_t width,
   int32_t height,
-
   double global_alpha,
   const shadow_t *shadow,
   composite_operation_t compose_op,
   const transform_t *transform);
 
-
-
 color_t_
 context_get_pixel(
   const context_t *c,
diff --git a/src/implem/context_internal.h b/src/implem/context_internal.h
index 0ed2c80c..dd7b7119 100644
--- a/src/implem/context_internal.h
+++ b/src/implem/context_internal.h
@@ -14,23 +14,10 @@
 #include <stdint.h>
 #include <stdbool.h>
 
-#include "color.h"
-#include "pixmap.h"
-
 typedef struct context_t {
   bool offscreen;
-  color_t_ *data;
   int32_t width;
   int32_t height;
-
-  pixmap_t clip_region; // temporary
 } context_t;
 
-void
-_context_copy_to_buffer(
-  context_t *c,
-  color_t_ *data,
-  int32_t width,
-  int32_t height);
-
 #endif /* __CONTEXT_INTERNAL_H */
diff --git a/src/implem/gdi/gdi_hw_context.c b/src/implem/gdi/gdi_hw_context.c
new file mode 100644
index 00000000..de5d6fcc
--- /dev/null
+++ b/src/implem/gdi/gdi_hw_context.c
@@ -0,0 +1,95 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifdef HAS_GDI
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <assert.h>
+
+#include <windows.h>
+
+#include "../config.h"
+#include "../color.h"
+#include "../context_internal.h"
+#include "../hw_context_internal.h"
+#include "gdi_target.h"
+
+typedef struct gdi_hw_context_t {
+  hw_context_t base;
+} gdi_hw_context_t;
+
+gdi_hw_context_t *
+gdi_hw_context_create(
+  gdi_target_t *target,
+  int32_t width,
+  int32_t height)
+{
+  assert(target != NULL);
+  assert(target->hwnd != NULL);
+  assert(width > 0);
+  assert(height > 0);
+
+  gdi_hw_context_t *context =
+    (gdi_hw_context_t *)calloc(1, sizeof(gdi_hw_context_t));
+  if (context == NULL) {
+    return NULL;
+  }
+
+  context->base.base.width = width;
+  context->base.base.height = height;
+
+  return context;
+}
+
+void
+gdi_hw_context_destroy(
+  gdi_hw_context_t *context)
+{
+  assert(context != NULL);
+
+  free(context);
+}
+
+bool
+gdi_hw_context_resize(
+  gdi_hw_context_t *context,
+  int32_t width,
+  int32_t height)
+{
+  assert(context != NULL);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
+  assert(width > 0);
+  assert(height > 0);
+
+  context->base.base.width = width;
+  context->base.base.height = height;
+
+  return true;
+}
+
+void
+gdi_hw_context_present(
+  gdi_hw_context_t *context)
+{
+  assert(context != NULL);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
+
+}
+
+#else
+
+const int gdi_hw_context = 0;
+
+#endif /* HAS_GDI */
diff --git a/src/implem/gdi/gdi_context.h b/src/implem/gdi/gdi_hw_context.h
similarity index 72%
rename from src/implem/gdi/gdi_context.h
rename to src/implem/gdi/gdi_hw_context.h
index 6bf4da6e..c1c3b42e 100644
--- a/src/implem/gdi/gdi_context.h
+++ b/src/implem/gdi/gdi_hw_context.h
@@ -8,35 +8,34 @@
 /*                                                                        */
 /**************************************************************************/
 
-#ifndef __GDI_CONTEXT_H
-#define __GDI_CONTEXT_H
+#ifndef __GDI_HW_CONTEXT_H
+#define __GDI_HW_CONTEXT_H
 
 #include <stdint.h>
 #include <stdbool.h>
 
-#include "../color.h"
 #include "gdi_target.h"
 
-typedef struct gdi_context_t gdi_context_t;
+typedef struct gdi_hw_context_t gdi_hw_context_t;
 
-gdi_context_t *
-gdi_context_create(
+gdi_hw_context_t *
+gdi_hw_context_create(
   gdi_target_t *target,
   int32_t width,
   int32_t height);
 
 void
-gdi_context_destroy(
-  gdi_context_t *context);
+gdi_hw_context_destroy(
+  gdi_hw_context_t *context);
 
 bool
-gdi_context_resize(
-  gdi_context_t *context,
+gdi_hw_context_resize(
+  gdi_hw_context_t *context,
   int32_t width,
   int32_t height);
 
 void
-gdi_context_present(
-  gdi_context_t *context);
+gdi_hw_context_present(
+  gdi_hw_context_t *context);
 
-#endif /* __GDI_CONTEXT_H */
+#endif /* __GDI_HW_CONTEXT_H */
diff --git a/src/implem/gdi/gdi_context.c b/src/implem/gdi/gdi_sw_context.c
similarity index 77%
rename from src/implem/gdi/gdi_context.c
rename to src/implem/gdi/gdi_sw_context.c
index edbe4e1e..a4e67353 100644
--- a/src/implem/gdi/gdi_context.c
+++ b/src/implem/gdi/gdi_sw_context.c
@@ -21,17 +21,18 @@
 #include "../config.h"
 #include "../color.h"
 #include "../context_internal.h"
+#include "../sw_context_internal.h"
 #include "gdi_target.h"
 
-typedef struct gdi_context_t {
-  context_t base;
+typedef struct gdi_sw_context_t {
+  sw_context_t base;
   HBITMAP bmp;
   HDC hdc;
   HWND hwnd;
-} gdi_context_t;
+} gdi_sw_context_t;
 
 static HBITMAP
-_context_create_gdi_bitmap(
+_gdi_sw_context_create_bitmap(
   HDC hdc,
   int32_t width,
   int32_t height,
@@ -72,8 +73,8 @@ _context_create_gdi_bitmap(
   return bmp;
 }
 
-gdi_context_t *
-gdi_context_create(
+gdi_sw_context_t *
+gdi_sw_context_create(
   gdi_target_t *target,
   int32_t width,
   int32_t height)
@@ -83,8 +84,8 @@ gdi_context_create(
   assert(width > 0);
   assert(height > 0);
 
-  gdi_context_t *context =
-    (gdi_context_t *)calloc(1, sizeof(gdi_context_t));
+  gdi_sw_context_t *context =
+    (gdi_sw_context_t *)calloc(1, sizeof(gdi_sw_context_t));
   if (context == NULL) {
     return NULL;
   }
@@ -103,7 +104,7 @@ gdi_context_create(
   }
 
   color_t_ *data = NULL;
-  HBITMAP bmp = _context_create_gdi_bitmap(hdc, width, height, &data);
+  HBITMAP bmp = _gdi_sw_context_create_bitmap(hdc, width, height, &data);
   if (bmp == NULL) {
     assert(data == NULL);
     DeleteDC(hdc);
@@ -112,9 +113,9 @@ gdi_context_create(
   }
   assert(data != NULL);
 
+  context->base.base.width = width;
+  context->base.base.height = height;
   context->base.data = data;
-  context->base.width = width;
-  context->base.height = height;
   context->bmp = bmp;
   context->hdc = hdc;
   context->hwnd = target->hwnd;
@@ -123,8 +124,8 @@ gdi_context_create(
 }
 
 void
-gdi_context_destroy(
-  gdi_context_t *context)
+gdi_sw_context_destroy(
+  gdi_sw_context_t *context)
 {
   assert(context != NULL);
 
@@ -140,15 +141,15 @@ gdi_context_destroy(
 }
 
 bool
-gdi_context_resize(
-  gdi_context_t *context,
+gdi_sw_context_resize(
+  gdi_sw_context_t *context,
   int32_t width,
   int32_t height)
 {
   assert(context != NULL);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
   assert(context->base.data != NULL);
-  assert(context->base.width > 0);
-  assert(context->base.height > 0);
   assert(context->bmp != NULL);
   assert(context->hdc != NULL);
   assert(width > 0);
@@ -156,38 +157,40 @@ gdi_context_resize(
 
   color_t_ *data = NULL;
   HBITMAP bmp =
-    _context_create_gdi_bitmap(context->hdc, width, height, &data);
+    _gdi_sw_context_create_bitmap(context->hdc, width, height, &data);
   if (bmp == NULL) {
     assert(data == NULL);
     return false;
   }
   assert(data != NULL);
 
-  _context_copy_to_buffer(&context->base, data, width, height);
+  _sw_context_copy_to_buffer(&context->base, data, width, height);
 
   DeleteObject(context->bmp);
 
+  context->base.base.width = width;
+  context->base.base.height = height;
   context->base.data = data;
-  context->base.width = width;
-  context->base.height = height;
   context->bmp = bmp;
 
   return true;
 }
 
 void
-gdi_context_present(
-  gdi_context_t *context)
+gdi_sw_context_present(
+  gdi_sw_context_t *context)
 {
   assert(context != NULL);
-  assert(context->base.width > 0);
-  assert(context->base.height > 0);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
   assert(context->bmp != NULL);
   assert(context->hdc != NULL);
   assert(context->hwnd != NULL);
 
   HDC hdc = GetDC(context->hwnd);
-  BitBlt(hdc, 0, 0, context->base.width, context->base.height,
+  BitBlt(hdc, 0, 0,
+         context->base.base.width,
+         context->base.base.height,
          context->hdc, 0, 0, SRCCOPY);
   ReleaseDC(context->hwnd, hdc);
   GdiFlush();
@@ -196,6 +199,6 @@ gdi_context_present(
 
 #else
 
-const int gdi_context = 0;
+const int gdi_sw_context = 0;
 
 #endif /* HAS_GDI */
diff --git a/src/implem/gdi/gdi_sw_context.h b/src/implem/gdi/gdi_sw_context.h
new file mode 100644
index 00000000..a20358ba
--- /dev/null
+++ b/src/implem/gdi/gdi_sw_context.h
@@ -0,0 +1,41 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifndef __GDI_SW_CONTEXT_H
+#define __GDI_SW_CONTEXT_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "gdi_target.h"
+
+typedef struct gdi_sw_context_t gdi_sw_context_t;
+
+gdi_sw_context_t *
+gdi_sw_context_create(
+  gdi_target_t *target,
+  int32_t width,
+  int32_t height);
+
+void
+gdi_sw_context_destroy(
+  gdi_sw_context_t *context);
+
+bool
+gdi_sw_context_resize(
+  gdi_sw_context_t *context,
+  int32_t width,
+  int32_t height);
+
+void
+gdi_sw_context_present(
+  gdi_sw_context_t *context);
+
+#endif /* __GDI_SW_CONTEXT_H */
diff --git a/src/implem/hw_context.c b/src/implem/hw_context.c
new file mode 100644
index 00000000..8fbb8e49
--- /dev/null
+++ b/src/implem/hw_context.c
@@ -0,0 +1,389 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifdef HAS_ACCEL
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <assert.h>
+
+#include "config.h"
+#include "target.h"
+#include "pixmap.h"
+#include "color.h"
+
+#include "rect.h"
+#include "polygon.h"
+#include "transform.h"
+#include "draw_style.h"
+#include "list.h"
+#include "state.h" // for shadow_t
+
+#include "draw_instr.h"
+#include "poly_render.h"
+#include "impexp.h"
+
+#ifdef HAS_GDI
+#include "gdi/gdi_hw_context.h"
+#endif
+#ifdef HAS_QUARTZ
+#include "quartz/qtz_hw_context.h"
+#endif
+#ifdef HAS_X11
+#include "x11/x11_hw_context.h"
+#endif
+#ifdef HAS_WAYLAND
+#include "wayland/wl_hw_context.h"
+#endif
+
+#include "context_internal.h"
+#include "hw_context_internal.h"
+
+hw_context_t *
+hw_context_create(
+  int32_t width,
+  int32_t height)
+{
+  assert(width > 0);
+  assert(height > 0);
+
+  hw_context_t *c = (hw_context_t *)calloc(1, sizeof(hw_context_t));
+  if (c == NULL) {
+    return NULL;
+  }
+
+  c->base.offscreen = true;
+  c->base.width = width;
+  c->base.height = height;
+
+  return c;
+}
+
+hw_context_t *
+hw_context_create_from_pixmap(
+  pixmap_t *pixmap)
+{
+  assert(pixmap != NULL);
+  assert(pixmap_valid(*pixmap) == true);
+
+  hw_context_t *c = (hw_context_t *)calloc(1, sizeof(hw_context_t));
+  if (c == NULL) {
+    return NULL;
+  }
+
+  c->base.offscreen = true;
+  c->base.width = pixmap->width;
+  c->base.height = pixmap->height;
+
+  free(pixmap->data);
+  pixmap->data = NULL;
+  pixmap->width = 0;
+  pixmap->height = 0;
+
+  return c;
+}
+
+hw_context_t *
+hw_context_create_onscreen(
+  target_t *target,
+  int32_t width,
+  int32_t height)
+{
+  assert(target != NULL);
+  assert(width > 0);
+  assert(height > 0);
+
+  hw_context_t *c = NULL;
+  switch_IMPL() {
+    case_GDI(
+      c = (hw_context_t *)gdi_hw_context_create((gdi_target_t *)target,
+                                                width, height));
+    case_QUARTZ(
+      c = (hw_context_t *)qtz_hw_context_create((qtz_target_t *)target,
+                                                width, height));
+    case_X11(
+      c = (hw_context_t *)x11_hw_context_create((x11_target_t *)target,
+                                                width, height));
+    case_WAYLAND(
+      c = (hw_context_t *)wl_hw_context_create((wl_target_t *)target,
+                                               width, height));
+    default_fail();
+  }
+  if (c == NULL) {
+    return NULL;
+  }
+
+  c->base.offscreen = false;
+
+  return c;
+}
+
+void
+hw_context_destroy(
+  hw_context_t *c)
+{
+  assert(c != NULL);
+  assert(c->data != NULL);
+
+  if (c->base.offscreen == true) {
+    free(c);
+  } else {
+    switch_IMPL() {
+      case_GDI(gdi_hw_context_destroy((gdi_hw_context_t *)c));
+      case_QUARTZ(qtz_hw_context_destroy((qtz_hw_context_t *)c));
+      case_X11(x11_hw_context_destroy((x11_hw_context_t *)c));
+      case_WAYLAND(wl_hw_context_destroy((wl_hw_context_t *)c));
+      default_fail();
+    }
+  }
+}
+
+bool
+hw_context_resize(
+  hw_context_t *c,
+  int32_t width,
+  int32_t height)
+{
+  assert(c != NULL);
+  assert(c->base.width > 0);
+  assert(c->base.height > 0);
+
+  if ((width <= 0) || (height <= 0)) {
+    return false;
+  }
+
+  if ((width == c->base.width) && (height == c->base.height)) {
+    return true;
+  }
+
+// TODO: fill extra data with background color
+
+  if (c->base.offscreen == true) {
+
+    c->base.width = width;
+    c->base.height = height;
+
+    return true;
+
+  } else {
+    bool result = false;
+    switch_IMPL() {
+      case_GDI(result =
+               gdi_hw_context_resize((gdi_hw_context_t *)c, width, height));
+      case_QUARTZ(result =
+                  qtz_hw_context_resize((qtz_hw_context_t *)c, width, height));
+      case_X11(result =
+               x11_hw_context_resize((x11_hw_context_t *)c, width, height));
+      case_WAYLAND(result =
+                   wl_hw_context_resize((wl_hw_context_t *)c, width, height));
+      default_fail();
+    }
+
+    return result;
+  }
+}
+
+void
+hw_context_present(
+  hw_context_t *c)
+{
+  assert(c != NULL);
+  assert(c->base.offscreen == false);
+  assert(c->base.width > 0);
+  assert(c->base.height > 0);
+
+  switch_IMPL() {
+    case_GDI(gdi_hw_context_present((gdi_hw_context_t *)c));
+    case_QUARTZ(qtz_hw_context_present((qtz_hw_context_t *)c));
+    case_X11(x11_hw_context_present((x11_hw_context_t *)c));
+    case_WAYLAND(wl_hw_context_present((wl_hw_context_t *)c));
+    default_fail();
+  }
+}
+
+static void
+_hw_context_clip_fill_instr(
+  hw_context_t *c,
+  const path_fill_instr_t *instr,
+  const transform_t *transform)
+{
+  assert(c != NULL);
+  assert(instr != NULL);
+  assert(instr->poly != NULL);
+  assert(transform != NULL);
+
+}
+
+bool
+hw_context_clip(
+  hw_context_t *c,
+  list_t *clip_path,
+  const transform_t *transform)
+{
+  assert(c != NULL);
+  assert(clip_path != NULL);
+  assert(transform != NULL);
+
+  list_iterator_t *it = list_get_iterator(clip_path);
+  if (it == NULL) {
+    return false;
+  }
+
+  path_fill_instr_t *instr = NULL;
+  while ((instr = (path_fill_instr_t *)list_iterator_next(it)) != NULL) {
+    _hw_context_clip_fill_instr(c, instr, transform);
+  }
+
+  list_free_iterator(it);
+
+  return true;
+}
+
+void
+hw_context_clear_clip(
+  hw_context_t *c)
+{
+  assert(c != NULL);
+
+}
+
+void
+hw_context_render_polygon(
+  hw_context_t *c,
+  const polygon_t *p,
+  const rect_t *bbox,
+  draw_style_t draw_style,
+  double global_alpha,
+  const shadow_t *shadow,
+  composite_operation_t compose_op,
+  bool non_zero,
+  const transform_t *transform)
+{
+  assert(c != NULL);
+  assert(p != NULL);
+  assert(bbox != NULL);
+  assert(shadow != NULL);
+  assert(transform != NULL);
+
+}
+
+void
+hw_context_blit(
+  hw_context_t *dc,
+  int32_t dx,
+  int32_t dy,
+  const hw_context_t *sc,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height,
+
+  double global_alpha,
+  const shadow_t *shadow,
+  composite_operation_t compose_op,
+  const transform_t *transform)
+{
+  assert(dc != NULL);
+  assert(sc != NULL);
+  assert(shadow != NULL);
+  assert(transform != NULL);
+
+}
+
+color_t_
+hw_context_get_pixel(
+  const hw_context_t *c,
+  int32_t x,
+  int32_t y)
+{
+  assert(c != NULL);
+
+  color_t_ color = color_black;
+
+  return color;
+}
+
+void
+hw_context_put_pixel(
+  hw_context_t *c,
+  int32_t x,
+  int32_t y,
+  color_t_ color)
+{
+  assert(c != NULL);
+
+}
+
+pixmap_t
+hw_context_get_pixmap(
+  const hw_context_t *c,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height)
+{
+  assert(c != NULL);
+
+  pixmap_t dp = pixmap_null();
+
+  return dp;
+}
+
+void
+hw_context_put_pixmap(
+  hw_context_t *c,
+  int32_t dx,
+  int32_t dy,
+  const pixmap_t *sp,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height)
+{
+  assert(c != NULL);
+  assert(sp != NULL);
+  assert(pixmap_valid(*sp) == true);
+
+}
+
+bool
+hw_context_export_png(
+  const hw_context_t *c,
+  const char *filename) // as UTF-8
+{
+  assert(c != NULL);
+  assert(filename != NULL);
+
+  const pixmap_t pm = pixmap_null();
+
+  return impexp_export_png(&pm, filename);
+}
+
+bool
+hw_context_import_png(
+  hw_context_t *c,
+  int32_t x,
+  int32_t y,
+  const char *filename) // as UTF-8
+{
+  assert(c != NULL);
+  assert(filename != NULL);
+
+  pixmap_t pm = pixmap_null();
+
+  return impexp_import_png(&pm, x, y, filename);
+}
+
+#else
+
+const int hw_context = 0;
+
+#endif /* HAS_ACCEL */
diff --git a/src/implem/hw_context.h b/src/implem/hw_context.h
new file mode 100644
index 00000000..8d4b58f1
--- /dev/null
+++ b/src/implem/hw_context.h
@@ -0,0 +1,143 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifndef __HW_CONTEXT_H
+#define __HW_CONTEXT_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "target.h"
+#include "pixmap.h"
+
+#include "rect.h"
+#include "polygon.h"
+#include "transform.h"
+#include "draw_style.h"
+#include "list.h"
+#include "state.h" // for shadow_t
+
+typedef struct hw_context_t hw_context_t;
+
+hw_context_t *
+hw_context_create(
+  int32_t width,
+  int32_t height);
+
+// Creates a context from a pixmap
+// The data pointer is transfered to the context
+// (thus removed from the pixmap); if you kept
+// a copy, do NOT free it !
+hw_context_t *
+hw_context_create_from_pixmap(
+  pixmap_t *pixmap);
+
+hw_context_t *
+hw_context_create_onscreen(
+  target_t *target,
+  int32_t width,
+  int32_t height);
+
+void
+hw_context_destroy(
+  hw_context_t *c);
+
+bool
+hw_context_resize(
+  hw_context_t *c,
+  int32_t width,
+  int32_t height);
+
+void
+hw_context_present(
+  hw_context_t *c);
+
+bool
+hw_context_clip(
+  hw_context_t *c,
+  list_t *clip_path,
+  const transform_t *transform);
+
+void
+hw_context_clear_clip(
+  hw_context_t *c);
+
+void
+hw_context_render_polygon(
+  hw_context_t *c,
+  const polygon_t *p,
+  const rect_t *bbox,
+  draw_style_t draw_style,
+  double global_alpha,
+  const shadow_t *shadow,
+  composite_operation_t compose_op,
+  bool non_zero,
+  const transform_t *transform);
+
+void
+hw_context_blit(
+  hw_context_t *dc,
+  int32_t dx,
+  int32_t dy,
+  const hw_context_t *sc,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height,
+  double global_alpha,
+  const shadow_t *shadow,
+  composite_operation_t compose_op,
+  const transform_t *transform);
+
+color_t_
+hw_context_get_pixel(
+  const hw_context_t *c,
+  int32_t x,
+  int32_t y);
+
+void
+hw_context_put_pixel(
+  hw_context_t *c,
+  int32_t x,
+  int32_t y,
+  color_t_ color);
+
+pixmap_t
+hw_context_get_pixmap(
+  const hw_context_t *c,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height);
+
+void
+hw_context_put_pixmap(
+  hw_context_t *c,
+  int32_t dx,
+  int32_t dy,
+  const pixmap_t *sp,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height);
+
+bool
+hw_context_export_png(
+  const hw_context_t *c,
+  const char *filename); // as UTF-8
+
+bool
+hw_context_import_png(
+  hw_context_t *c,
+  int32_t x,
+  int32_t y,
+  const char *filename); // as UTF-8
+
+#endif /* __HW_CONTEXT_H */
diff --git a/src/implem/hw_context_internal.h b/src/implem/hw_context_internal.h
new file mode 100644
index 00000000..aaa8aaff
--- /dev/null
+++ b/src/implem/hw_context_internal.h
@@ -0,0 +1,20 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifndef __HW_CONTEXT_INTERNAL_H
+#define __HW_CONTEXT_INTERNAL_H
+
+#include "context_internal.h"
+
+typedef struct hw_context_t {
+  context_t base;
+} hw_context_t;
+
+#endif /* __HW_CONTEXT_INTERNAL_H */
diff --git a/src/implem/quartz/qtz_hw_context.c b/src/implem/quartz/qtz_hw_context.c
new file mode 100644
index 00000000..d7a97f44
--- /dev/null
+++ b/src/implem/quartz/qtz_hw_context.c
@@ -0,0 +1,153 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifdef HAS_QUARTZ
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <assert.h>
+
+#include <Cocoa/Cocoa.h>
+
+#include "../config.h"
+#include "../color.h"
+#include "../context_internal.h"
+#include "../hw_context_internal.h"
+#include "qtz_hw_context.h"
+#include "qtz_target.h"
+#include "qtz_util.h"
+
+@class CanvasHWView;
+
+typedef struct qtz_hw_context_t {
+  hw_context_t base;
+  CanvasHWView *nsview;
+} qtz_hw_context_t;
+
+@interface CanvasHWView : NSView
+{
+  @public qtz_hw_context_t *context;
+}
+@end
+
+@implementation CanvasHWView { }
+
+- (BOOL)isFlipped
+{
+  return FALSE;
+}
+
+- (BOOL)preservesContentDuringLiveResize
+{
+  return TRUE;
+}
+
+- (void)drawRect:(NSRect)rect // called after setNeedsDisplay:YES
+{
+/*
+  qtz_window_t *w = qtz_backend_get_window([self window]);
+  if (w != NULL) {
+    event_t evt;
+    evt.type = EVENT_PRESENT; // not needed
+    evt.time = qtz_get_time();
+    evt.target = (void *)w;
+    event_notify(qtz_back->listener, &evt);
+  }
+*/
+
+  qtz_hw_context_present(self->context);
+
+}
+
+@end
+
+qtz_hw_context_t *
+qtz_hw_context_create(
+  qtz_target_t *target,
+  int32_t width,
+  int32_t height)
+{
+  assert(target != NULL);
+  assert(target->nhwin != NULL);
+  assert(width > 0);
+  assert(height > 0);
+
+  qtz_hw_context_t *context =
+    (qtz_hw_context_t *)calloc(1, sizeof(qtz_hw_context_t));
+  if (context == NULL) {
+    return NULL;
+  }
+
+  ALLOC_POOL; // don't know if necessary here
+
+  CanvasHWView *nsview =
+    [[CanvasHWView alloc] initWithFrame:[target->nswin frame]];
+  [nsview setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
+  [target->nswin setContentView:nsview];
+  nsview->context = context;
+
+  RELEASE_POOL;
+
+  context->base.base.width = width;
+  context->base.base.height = height;
+  context->nsview = nsview;
+
+  return context;
+}
+
+void
+qtz_hw_context_destroy(
+  qtz_hw_context_t *context)
+{
+  assert(context != NULL);
+
+  if (context->nsview != NULL) {
+//    [[context->nsview window] setContentView:nil];
+    [context->nsview release];
+  }
+
+}
+
+bool
+qtz_hw_context_resize(
+  qtz_hw_context_t *context,
+  int32_t width,
+  int32_t height)
+{
+  assert(context != NULL);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
+  assert(width > 0);
+  assert(height > 0);
+
+  context->base.base.width = width;
+  context->base.base.height = height;
+
+  return true;
+}
+
+void
+qtz_hw_context_present(
+  qtz_hw_context_t *context)
+{
+  assert(context != NULL);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
+  assert(context->nsview != NULL);
+
+}
+
+#else
+
+const int qtz_hw_context = 0;
+
+#endif /* HAS_QUARTZ */
diff --git a/src/implem/quartz/qtz_context.h b/src/implem/quartz/qtz_hw_context.h
similarity index 71%
rename from src/implem/quartz/qtz_context.h
rename to src/implem/quartz/qtz_hw_context.h
index 2143fc59..af901b55 100644
--- a/src/implem/quartz/qtz_context.h
+++ b/src/implem/quartz/qtz_hw_context.h
@@ -8,36 +8,34 @@
 /*                                                                        */
 /**************************************************************************/
 
-#ifndef __QTZ_CONTEXT_H
-#define __QTZ_CONTEXT_H
+#ifndef __QTZ_HW_CONTEXT_H
+#define __QTZ_HW_CONTEXT_H
 
 #include <stdint.h>
 #include <stdbool.h>
 
-#include "../color.h"
-#include "../context_internal.h"
 #include "qtz_target.h"
 
-typedef struct qtz_context_t qtz_context_t;
+typedef struct qtz_hw_context_t qtz_hw_context_t;
 
-qtz_context_t *
-qtz_context_create(
+qtz_hw_context_t *
+qtz_hw_context_create(
   qtz_target_t *target,
   int32_t width,
   int32_t height);
 
 void
-qtz_context_destroy(
-  qtz_context_t *context);
+qtz_hw_context_destroy(
+  qtz_hw_context_t *context);
 
 bool
-qtz_context_resize(
-  qtz_context_t *context,
+qtz_hw_context_resize(
+  qtz_hw_context_t *context,
   int32_t width,
   int32_t height);
 
 void
-qtz_context_present(
-  qtz_context_t *context);
+qtz_hw_context_present(
+  qtz_hw_context_t *context);
 
-#endif /* __QTZ_CONTEXT_H */
+#endif /* __QTZ_HW_CONTEXT_H */
diff --git a/src/implem/quartz/qtz_context.c b/src/implem/quartz/qtz_sw_context.c
similarity index 79%
rename from src/implem/quartz/qtz_context.c
rename to src/implem/quartz/qtz_sw_context.c
index 71e18e8d..91cda941 100644
--- a/src/implem/quartz/qtz_context.c
+++ b/src/implem/quartz/qtz_sw_context.c
@@ -21,23 +21,25 @@
 #include "../config.h"
 #include "../color.h"
 #include "../context_internal.h"
-#include "qtz_util.h"
-//#include "qtz_backend.h"
+#include "../sw_context_internal.h"
+#include "qtz_sw_context.h"
 #include "qtz_target.h"
-#include "qtz_context.h"
+#include "qtz_util.h"
+
+@class CanvasView;
+
+typedef struct qtz_sw_context_t {
+  sw_context_t base;
+  CGContextRef ctxt;
+  CanvasView *nsview;
+} qtz_sw_context_t;
 
 @interface CanvasView : NSView
 {
-  @public qtz_context_t *context;
+  @public qtz_sw_context_t *context;
 }
 @end
 
-typedef struct qtz_context_t {
-  context_t base;
-  CGContextRef ctxt;
-  CanvasView *nsview;
-} qtz_context_t;
-
 @implementation CanvasView { }
 
 - (BOOL)isFlipped
@@ -63,14 +65,14 @@ typedef struct qtz_context_t {
   }
 */
 
-  qtz_context_present(self->context);
+  qtz_sw_context_present(self->context);
 
 }
 
 @end
 
 static CGContextRef
-_qtz_context_create_bitmap_context(
+_qtz_sw_context_create_bitmap_context(
   int32_t width,
   int32_t height,
   color_t_ **data)
@@ -107,8 +109,8 @@ _qtz_context_create_bitmap_context(
   return ctxt;
 }
 
-qtz_context_t *
-qtz_context_create(
+qtz_sw_context_t *
+qtz_sw_context_create(
   qtz_target_t *target,
   int32_t width,
   int32_t height)
@@ -118,15 +120,15 @@ qtz_context_create(
   assert(width > 0);
   assert(height > 0);
 
-  qtz_context_t *context =
-    (qtz_context_t *)calloc(1, sizeof(qtz_context_t));
+  qtz_sw_context_t *context =
+    (qtz_sw_context_t *)calloc(1, sizeof(qtz_sw_context_t));
   if (context == NULL) {
     return NULL;
   }
 
   color_t_ *data = NULL;
   CGContextRef ctxt =
-    _qtz_context_create_bitmap_context(width, height, &data);
+    _qtz_sw_context_create_bitmap_context(width, height, &data);
   if (ctxt == NULL) {
     assert(data == NULL);
     free(context);
@@ -144,9 +146,9 @@ qtz_context_create(
 
   RELEASE_POOL;
 
+  context->base.base.width = width;
+  context->base.base.height = height;
   context->base.data = data;
-  context->base.width = width;
-  context->base.height = height;
   context->ctxt = ctxt;
   context->nsview = nsview;
 
@@ -154,8 +156,8 @@ qtz_context_create(
 }
 
 void
-qtz_context_destroy(
-  qtz_context_t *context)
+qtz_sw_context_destroy(
+  qtz_sw_context_t *context)
 {
   assert(context != NULL);
 
@@ -172,47 +174,47 @@ qtz_context_destroy(
 }
 
 bool
-qtz_context_resize(
-  qtz_context_t *context,
+qtz_sw_context_resize(
+  qtz_sw_context_t *context,
   int32_t width,
   int32_t height)
 {
   assert(context != NULL);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
   assert(context->base.data != NULL);
-  assert(context->base.width > 0);
-  assert(context->base.height > 0);
   assert(context->ctxt != NULL);
   assert(width > 0);
   assert(height > 0);
 
   color_t_ *data = NULL;
   CGContextRef ctxt =
-    _qtz_context_create_bitmap_context(width, height, &data);
+    _qtz_sw_context_create_bitmap_context(width, height, &data);
   if (ctxt == NULL) {
     assert(data == NULL);
     return false;
   }
   assert(data != NULL);
 
-  _context_copy_to_buffer(&context->base, data, width, height);
+  _sw_context_copy_to_buffer(&context->base, data, width, height);
 
   CGContextRelease(context->ctxt);
 
+  context->base.base.width = width;
+  context->base.base.height = height;
   context->base.data = data;
-  context->base.width = width;
-  context->base.height = height;
   context->ctxt = ctxt;
 
   return true;
 }
 
 void
-qtz_context_present(
-  qtz_context_t *context)
+qtz_sw_context_present(
+  qtz_sw_context_t *context)
 {
   assert(context != NULL);
-  assert(context->base.width > 0);
-  assert(context->base.height > 0);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
   assert(context->ctxt != NULL);
   assert(context->nsview != NULL);
 
@@ -229,8 +231,8 @@ qtz_context_present(
   CGImageRef img = CGBitmapContextCreateImage(context->ctxt);
 
   CGRect rect =
-    CGRectMake(0, context->nsview.frame.size.height - context->base.height,
-               context->base.width, context->base.height);
+    CGRectMake(0, context->nsview.frame.size.height - context->base.base.height,
+               context->base.base.width, context->base.base.height);
   CGContextDrawImage(ctxt, rect, img);
 
   [[NSGraphicsContext currentContext] flushGraphics];
@@ -242,6 +244,6 @@ qtz_context_present(
 
 #else
 
-const int qtz_context = 0;
+const int qtz_sw_context = 0;
 
 #endif /* HAS_QUARTZ */
diff --git a/src/implem/quartz/qtz_sw_context.h b/src/implem/quartz/qtz_sw_context.h
new file mode 100644
index 00000000..c77d5536
--- /dev/null
+++ b/src/implem/quartz/qtz_sw_context.h
@@ -0,0 +1,41 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifndef __QTZ_SW_CONTEXT_H
+#define __QTZ_SW_CONTEXT_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "qtz_target.h"
+
+typedef struct qtz_sw_context_t qtz_sw_context_t;
+
+qtz_sw_context_t *
+qtz_sw_context_create(
+  qtz_target_t *target,
+  int32_t width,
+  int32_t height);
+
+void
+qtz_sw_context_destroy(
+  qtz_sw_context_t *context);
+
+bool
+qtz_sw_context_resize(
+  qtz_sw_context_t *context,
+  int32_t width,
+  int32_t height);
+
+void
+qtz_sw_context_present(
+  qtz_sw_context_t *context);
+
+#endif /* __QTZ_SW_CONTEXT_H */
diff --git a/src/implem/sw_context.c b/src/implem/sw_context.c
new file mode 100644
index 00000000..b6a13340
--- /dev/null
+++ b/src/implem/sw_context.c
@@ -0,0 +1,597 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <assert.h>
+
+#include "config.h"
+#include "target.h"
+#include "pixmap.h"
+#include "color.h"
+
+#include "rect.h"
+#include "polygon.h"
+#include "transform.h"
+#include "draw_style.h"
+#include "list.h"
+#include "state.h" // for shadow_t
+
+#include "draw_instr.h"
+#include "poly_render.h"
+#include "impexp.h"
+
+#ifdef HAS_GDI
+#include "gdi/gdi_sw_context.h"
+#endif
+#ifdef HAS_QUARTZ
+#include "quartz/qtz_sw_context.h"
+#endif
+#ifdef HAS_X11
+#include "x11/x11_sw_context.h"
+#endif
+#ifdef HAS_WAYLAND
+#include "wayland/wl_sw_context.h"
+#endif
+
+#include "context_internal.h"
+#include "sw_context_internal.h"
+
+sw_context_t *
+sw_context_create(
+  int32_t width,
+  int32_t height)
+{
+  assert(width > 0);
+  assert(height > 0);
+
+  color_t_ *data = (color_t_ *)calloc(width * height, sizeof(color_t_));
+  if (data == NULL) {
+    return NULL;
+  }
+
+  sw_context_t *c = (sw_context_t *)calloc(1, sizeof(sw_context_t));
+  if (c == NULL) {
+    free(data);
+    return NULL;
+  }
+
+  c->base.offscreen = true;
+  c->base.width = width;
+  c->base.height = height;
+  c->data = data;
+  c->clip_region = pixmap_null();
+
+  return c;
+}
+
+sw_context_t *
+sw_context_create_from_pixmap(
+  pixmap_t *pixmap)
+{
+  assert(pixmap != NULL);
+  assert(pixmap_valid(*pixmap) == true);
+
+  sw_context_t *c = (sw_context_t *)calloc(1, sizeof(sw_context_t));
+  if (c == NULL) {
+    return NULL;
+  }
+
+  c->base.offscreen = true;
+  c->base.width = pixmap->width;
+  c->base.height = pixmap->height;
+  c->data = pixmap->data;
+  c->clip_region = pixmap_null();
+
+  pixmap->data = NULL;
+  pixmap->width = 0;
+  pixmap->height = 0;
+
+  return c;
+}
+
+sw_context_t *
+sw_context_create_onscreen(
+  target_t *target,
+  int32_t width,
+  int32_t height)
+{
+  assert(target != NULL);
+  assert(width > 0);
+  assert(height > 0);
+
+  sw_context_t *c = NULL;
+  switch_IMPL() {
+    case_GDI(
+      c = (sw_context_t *)gdi_sw_context_create((gdi_target_t *)target,
+                                                width, height));
+    case_QUARTZ(
+      c = (sw_context_t *)qtz_sw_context_create((qtz_target_t *)target,
+                                                width, height));
+    case_X11(
+      c = (sw_context_t *)x11_sw_context_create((x11_target_t *)target,
+                                                width, height));
+    case_WAYLAND(
+      c = (sw_context_t *)wl_sw_context_create((wl_target_t *)target,
+                                               width, height));
+    default_fail();
+  }
+  if (c == NULL) {
+    return NULL;
+  }
+
+  c->base.offscreen = false;
+  c->clip_region = pixmap_null();
+
+  return c;
+}
+
+void
+sw_context_destroy(
+  sw_context_t *c)
+{
+  assert(c != NULL);
+  assert(c->data != NULL);
+
+  if (pixmap_valid(c->clip_region) == true) {
+    pixmap_destroy(c->clip_region);
+  }
+
+  if (c->base.offscreen == true) {
+    free(c->data);
+    free(c);
+  } else {
+    switch_IMPL() {
+      case_GDI(gdi_sw_context_destroy((gdi_sw_context_t *)c));
+      case_QUARTZ(qtz_sw_context_destroy((qtz_sw_context_t *)c));
+      case_X11(x11_sw_context_destroy((x11_sw_context_t *)c));
+      case_WAYLAND(wl_sw_context_destroy((wl_sw_context_t *)c));
+      default_fail();
+    }
+  }
+}
+
+void
+_sw_context_copy_to_buffer(
+  sw_context_t *c,
+  color_t_ *data,
+  int32_t width,
+  int32_t height)
+{
+  assert(c != NULL);
+  assert(c->base.width > 0);
+  assert(c->base.height > 0);
+  assert(c->data != NULL);
+  assert(data != NULL);
+  assert(width > 0);
+  assert(height > 0);
+
+  uint32_t min_width = width < c->base.width ? width : c->base.width;
+  uint32_t min_height = height < c->base.height ? height : c->base.height;
+  for (size_t i = 0; i < min_height; ++i) {
+    for (size_t j = 0; j < min_width; ++j) {
+      data[i * width + j] = c->data[i * c->base.width + j];
+    }
+  }
+}
+
+bool
+sw_context_resize(
+  sw_context_t *c,
+  int32_t width,
+  int32_t height)
+{
+  assert(c != NULL);
+  assert(c->base.width > 0);
+  assert(c->base.height > 0);
+  assert(c->data != NULL);
+
+  if ((width <= 0) || (height <= 0)) {
+    return false;
+  }
+
+  if ((width == c->base.width) && (height == c->base.height)) {
+    return true;
+  }
+
+  if (pixmap_valid(c->clip_region)) {
+    pixmap_destroy(c->clip_region);
+  }
+
+// TODO: fill extra data with background color
+
+  if (c->base.offscreen == true) {
+
+    color_t_ *data = (color_t_ *)calloc(width * height, sizeof(color_t_));
+    if (data == NULL) {
+      return false;
+    }
+
+    _sw_context_copy_to_buffer(c, data, width, height);
+
+    free(c->data);
+
+    c->base.width = width;
+    c->base.height = height;
+    c->data = data;
+
+    return true;
+
+  } else {
+    bool result = false;
+    switch_IMPL() {
+      case_GDI(result =
+               gdi_sw_context_resize((gdi_sw_context_t *)c, width, height));
+      case_QUARTZ(result =
+                  qtz_sw_context_resize((qtz_sw_context_t *)c, width, height));
+      case_X11(result =
+               x11_sw_context_resize((x11_sw_context_t *)c, width, height));
+      case_WAYLAND(result =
+                   wl_sw_context_resize((wl_sw_context_t *)c, width, height));
+      default_fail();
+    }
+
+    return result;
+  }
+}
+
+void
+sw_context_present(
+  sw_context_t *c)
+{
+  assert(c != NULL);
+  assert(c->base.offscreen == false);
+  assert(c->base.width > 0);
+  assert(c->base.height > 0);
+  assert(c->data != NULL);
+
+  switch_IMPL() {
+    case_GDI(gdi_sw_context_present((gdi_sw_context_t *)c));
+    case_QUARTZ(qtz_sw_context_present((qtz_sw_context_t *)c));
+    case_X11(x11_sw_context_present((x11_sw_context_t *)c));
+    case_WAYLAND(wl_sw_context_present((wl_sw_context_t *)c));
+    default_fail();
+  }
+}
+
+// Direct access to the context pixels
+// Do NOT free the data pointer !
+static pixmap_t
+_sw_context_get_raw_pixmap(
+  sw_context_t *c)
+{
+  assert(c != NULL);
+  assert(c->base.width > 0);
+  assert(c->base.height > 0);
+  assert(c->data != NULL);
+
+  return pixmap(c->base.width, c->base.height, c->data);
+}
+
+static void
+_sw_context_clip_fill_instr(
+  sw_context_t *c,
+  const path_fill_instr_t *instr,
+  const transform_t *transform)
+{
+  assert(c != NULL);
+  assert(pixmap_valid(c->clip_region) == true);
+  assert(instr != NULL);
+  assert(instr->poly != NULL);
+  assert(transform != NULL);
+
+  draw_style_t white = (draw_style_t){ .type = DRAW_STYLE_COLOR,
+                                       .content.color = color_white };
+  shadow_t noshadow = (shadow_t){
+    .offset_x = 0, .offset_y = 0, .blur = 0,
+    .color = color_transparent_black };
+
+// TODO: could store bounding box with polygon
+  rect_t bbox = rect(point(0.0, 0.0),
+                     point((double)c->base.width,
+                           (double)c->base.height));
+
+  poly_render(&(c->clip_region), instr->poly, &bbox, white, 1.0, &noshadow,
+              ONE_MINUS_SRC, NULL, instr->non_zero, transform);
+}
+
+bool
+sw_context_clip(
+  sw_context_t *c,
+  list_t *clip_path,
+  const transform_t *transform)
+{
+  assert(c != NULL);
+  assert(clip_path != NULL);
+  assert(transform != NULL);
+
+  if ((pixmap_valid(c->clip_region) == true) &&
+      ((c->clip_region.width != c->base.width) ||
+       (c->clip_region.height != c->base.height))) {
+    pixmap_destroy(c->clip_region);
+  }
+
+  if (pixmap_valid(c->clip_region) == false) {
+    c->clip_region = pixmap(c->base.width, c->base.height, NULL);
+    if (pixmap_valid(c->clip_region) == false) {
+      return false;
+    }
+  }
+
+  pixmap_clear(c->clip_region);
+
+  list_iterator_t *it = list_get_iterator(clip_path);
+  if (it == NULL) {
+    return false;
+  }
+
+  path_fill_instr_t *instr = NULL;
+  while ((instr = (path_fill_instr_t *)list_iterator_next(it)) != NULL) {
+    _sw_context_clip_fill_instr(c, instr, transform);
+  }
+
+  list_free_iterator(it);
+
+  return true;
+}
+
+void
+sw_context_clear_clip(
+  sw_context_t *c)
+{
+  assert(c != NULL);
+
+  if (pixmap_valid(c->clip_region) == true) {
+    pixmap_destroy(c->clip_region);
+  }
+}
+
+void
+sw_context_render_polygon(
+  sw_context_t *c,
+  const polygon_t *p,
+  const rect_t *bbox,
+  draw_style_t draw_style,
+  double global_alpha,
+  const shadow_t *shadow,
+  composite_operation_t compose_op,
+  bool non_zero,
+  const transform_t *transform)
+{
+  assert(c != NULL);
+  assert(p != NULL);
+  assert(bbox != NULL);
+  assert(shadow != NULL);
+  assert(transform != NULL);
+
+  pixmap_t pm = pixmap(c->base.width, c->base.height, c->data);
+  poly_render(&pm, p, bbox, draw_style, global_alpha, shadow, compose_op,
+              &(c->clip_region), non_zero, transform);
+}
+
+void
+sw_context_blit(
+  sw_context_t *dc,
+  int32_t dx,
+  int32_t dy,
+  const sw_context_t *sc,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height,
+
+  double global_alpha,
+  const shadow_t *shadow,
+  composite_operation_t compose_op,
+  const transform_t *transform)
+{
+  assert(dc != NULL);
+  assert(sc != NULL);
+  assert(shadow != NULL);
+  assert(transform != NULL);
+
+  bool draw_shadows =
+    (shadow->blur > 0.0 ||
+     shadow->offset_x != 0.0 || shadow->offset_y != 0.0) &&
+    compose_op != COPY && shadow->color.a != 0;
+
+  const pixmap_t sp = _sw_context_get_raw_pixmap((sw_context_t *)sc);
+  pixmap_t dp = _sw_context_get_raw_pixmap(dc);
+
+// TODO: global_alpha ?
+  if ((transform_is_pure_translation(transform) == true) &&
+      (draw_shadows == false)) {
+
+    double tx = 0.0, ty = 0.0;
+    transform_extract_translation(transform, &tx, &ty);
+
+    int32_t lo_x = max(dx + (int32_t)tx, 0);
+    int32_t hi_x = min(dx + (int32_t)tx + width, dc->base.width); // canvas wd
+    int32_t lo_y = max(dy + (int32_t)ty, 0);
+    int32_t hi_y = min(dy + (int32_t)ty + height, dc->base.height); //canvas ht
+
+    for (int32_t i = lo_x; i < hi_x; i++) {
+      for (int32_t j = lo_y; j < hi_y; j++) {
+
+        int32_t uvx = i + sx - dx - (int32_t)tx;
+        int32_t uvy = j + sy - dy - (int32_t)ty;
+        if (uvx < 0 || uvx >= sc->base.width || // canvas wd
+            uvy < 0 || uvy >= sc->base.height) { // canvas ht
+          continue;
+        }
+
+        color_t_ fill_color = pixmap_at(sp, uvy, uvx);
+        int draw_alpha = fill_color.a;
+        if (pixmap_valid(dc->clip_region) == true) {
+          draw_alpha *= 255 - pixmap_at(dc->clip_region, j, i).a;
+          draw_alpha /= 255;
+        }
+
+        pixmap_at(dp, j, i) =
+          comp_compose(fill_color, pixmap_at(dp, j, i),
+                       draw_alpha, compose_op);
+      }
+    }
+
+  } else {
+
+    draw_style_t draw_style =
+      (draw_style_t){ .type = DRAW_STYLE_PIXMAP, .content.pixmap = &sp };
+
+    polygon_t *p = polygon_create(8, 1);
+    if (p == NULL) {
+      return;
+    }
+
+    point_t p1 = point((double)dx, (double)dy);
+    point_t p2 = point((double)(dx + width), (double)dy);
+    point_t p3 = point((double)(dx + width), (double)(dy + height));
+    point_t p4 = point((double)dx, (double)(dy + height));
+
+    transform_apply(transform, &p1);
+    transform_apply(transform, &p2);
+    transform_apply(transform, &p3);
+    transform_apply(transform, &p4);
+
+    polygon_add_point(p, p1);
+    polygon_add_point(p, p2);
+    polygon_add_point(p, p3);
+    polygon_add_point(p, p4);
+    polygon_end_subpoly(p, true);
+
+    rect_t bbox = rect(point(min4(p1.x, p2.x, p3.x, p4.x),
+                             min4(p1.y, p2.y, p3.y, p4.y)),
+                       point(max4(p1.x, p2.x, p3.x, p4.x),
+                             max4(p1.y, p2.y, p3.y, p4.y)));
+
+    transform_t *temp_transform = transform_copy(transform);
+    transform_translate(temp_transform, dx - sx, dy - sy);
+
+    pixmap_t pm = _sw_context_get_raw_pixmap(dc);
+    poly_render(&pm, p, &bbox, draw_style, global_alpha, shadow, compose_op,
+                &(dc->clip_region), false, temp_transform);
+
+    transform_destroy(temp_transform);
+
+    polygon_destroy(p);
+  }
+}
+
+color_t_
+sw_context_get_pixel(
+  const sw_context_t *c,
+  int32_t x,
+  int32_t y)
+{
+  assert(c != NULL);
+
+  color_t_ color = color_black;
+
+  const pixmap_t pm = _sw_context_get_raw_pixmap((sw_context_t *)c);
+  if (pixmap_valid(pm) == true) {
+    if ((x >= 0) && (x < pm.width) && (y >= 0) && (y < pm.height)) {
+      color = pixmap_at(pm, y, x);
+    }
+  }
+
+  return color;
+}
+
+void
+sw_context_put_pixel(
+  sw_context_t *c,
+  int32_t x,
+  int32_t y,
+  color_t_ color)
+{
+  assert(c != NULL);
+
+  pixmap_t pm = _sw_context_get_raw_pixmap((sw_context_t *)c);
+  if (pixmap_valid(pm) == true) {
+    if ((x >= 0) && (x < pm.width) && (y >= 0) && (y < pm.height)) {
+      pixmap_at(pm, y, x) = color;
+    }
+  }
+}
+
+pixmap_t
+sw_context_get_pixmap(
+  const sw_context_t *c,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height)
+{
+  assert(c != NULL);
+
+  pixmap_t dp = pixmap_null();
+  const pixmap_t sp = _sw_context_get_raw_pixmap((sw_context_t *)c);
+  if (pixmap_valid(sp) == true) {
+    dp = pixmap(width, height, NULL);
+    if (pixmap_valid(dp) == true) {
+      pixmap_blit(&dp, 0, 0, &sp, sx, sy, width, height);
+    }
+  }
+  return dp;
+}
+
+void
+sw_context_put_pixmap(
+  sw_context_t *c,
+  int32_t dx,
+  int32_t dy,
+  const pixmap_t *sp,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height)
+{
+  assert(c != NULL);
+  assert(sp != NULL);
+  assert(pixmap_valid(*sp) == true);
+
+  pixmap_t dp = _sw_context_get_raw_pixmap(c);
+  if (pixmap_valid(dp) == true) {
+    pixmap_blit(&dp, dx, dy, sp, sx, sy, width, height);
+  }
+}
+
+bool
+sw_context_export_png(
+  const sw_context_t *c,
+  const char *filename) // as UTF-8
+{
+  assert(c != NULL);
+  assert(filename != NULL);
+
+  const pixmap_t pm = _sw_context_get_raw_pixmap((sw_context_t *)c);
+  if (pixmap_valid(pm) == false) {
+    return false;
+  }
+  return impexp_export_png(&pm, filename);
+}
+
+bool
+sw_context_import_png(
+  sw_context_t *c,
+  int32_t x,
+  int32_t y,
+  const char *filename) // as UTF-8
+{
+  assert(c != NULL);
+  assert(filename != NULL);
+
+  pixmap_t pm = _sw_context_get_raw_pixmap(c);
+  if (pixmap_valid(pm) == false) {
+    return false;
+  }
+  return impexp_import_png(&pm, x, y, filename);
+}
diff --git a/src/implem/sw_context.h b/src/implem/sw_context.h
new file mode 100644
index 00000000..349119fa
--- /dev/null
+++ b/src/implem/sw_context.h
@@ -0,0 +1,143 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifndef __SW_CONTEXT_H
+#define __SW_CONTEXT_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "target.h"
+#include "pixmap.h"
+
+#include "rect.h"
+#include "polygon.h"
+#include "transform.h"
+#include "draw_style.h"
+#include "list.h"
+#include "state.h" // for shadow_t
+
+typedef struct sw_context_t sw_context_t;
+
+sw_context_t *
+sw_context_create(
+  int32_t width,
+  int32_t height);
+
+// Creates a context from a pixmap
+// The data pointer is transfered to the context
+// (thus removed from the pixmap); if you kept
+// a copy, do NOT free it !
+sw_context_t *
+sw_context_create_from_pixmap(
+  pixmap_t *pixmap);
+
+sw_context_t *
+sw_context_create_onscreen(
+  target_t *target,
+  int32_t width,
+  int32_t height);
+
+void
+sw_context_destroy(
+  sw_context_t *c);
+
+bool
+sw_context_resize(
+  sw_context_t *c,
+  int32_t width,
+  int32_t height);
+
+void
+sw_context_present(
+  sw_context_t *c);
+
+bool
+sw_context_clip(
+  sw_context_t *c,
+  list_t *clip_path,
+  const transform_t *transform);
+
+void
+sw_context_clear_clip(
+  sw_context_t *c);
+
+void
+sw_context_render_polygon(
+  sw_context_t *c,
+  const polygon_t *p,
+  const rect_t *bbox,
+  draw_style_t draw_style,
+  double global_alpha,
+  const shadow_t *shadow,
+  composite_operation_t compose_op,
+  bool non_zero,
+  const transform_t *transform);
+
+void
+sw_context_blit(
+  sw_context_t *dc,
+  int32_t dx,
+  int32_t dy,
+  const sw_context_t *sc,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height,
+  double global_alpha,
+  const shadow_t *shadow,
+  composite_operation_t compose_op,
+  const transform_t *transform);
+
+color_t_
+sw_context_get_pixel(
+  const sw_context_t *c,
+  int32_t x,
+  int32_t y);
+
+void
+sw_context_put_pixel(
+  sw_context_t *c,
+  int32_t x,
+  int32_t y,
+  color_t_ color);
+
+pixmap_t
+sw_context_get_pixmap(
+  const sw_context_t *c,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height);
+
+void
+sw_context_put_pixmap(
+  sw_context_t *c,
+  int32_t dx,
+  int32_t dy,
+  const pixmap_t *sp,
+  int32_t sx,
+  int32_t sy,
+  int32_t width,
+  int32_t height);
+
+bool
+sw_context_export_png(
+  const sw_context_t *c,
+  const char *filename); // as UTF-8
+
+bool
+sw_context_import_png(
+  sw_context_t *c,
+  int32_t x,
+  int32_t y,
+  const char *filename); // as UTF-8
+
+#endif /* __SW_CONTEXT_H */
diff --git a/src/implem/sw_context_internal.h b/src/implem/sw_context_internal.h
new file mode 100644
index 00000000..52f31591
--- /dev/null
+++ b/src/implem/sw_context_internal.h
@@ -0,0 +1,33 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifndef __SW_CONTEXT_INTERNAL_H
+#define __SW_CONTEXT_INTERNAL_H
+
+#include <stdint.h>
+
+#include "color.h"
+#include "pixmap.h"
+#include "context_internal.h"
+
+typedef struct sw_context_t {
+  context_t base;
+  color_t_ *data;
+  pixmap_t clip_region; // temporary
+} sw_context_t;
+
+void
+_sw_context_copy_to_buffer(
+  sw_context_t *c,
+  color_t_ *data,
+  int32_t width,
+  int32_t height);
+
+#endif /* __SW_CONTEXT_INTERNAL_H */
diff --git a/src/implem/wayland/wl_context.c b/src/implem/wayland/wl_hw_context.c
similarity index 76%
rename from src/implem/wayland/wl_context.c
rename to src/implem/wayland/wl_hw_context.c
index b7486d6d..578c5adc 100644
--- a/src/implem/wayland/wl_context.c
+++ b/src/implem/wayland/wl_hw_context.c
@@ -16,14 +16,15 @@
 
 #include "../config.h"
 #include "../context_internal.h"
+#include "../hw_context_internal.h"
 #include "wl_target.h"
 
-typedef struct wl_context_t {
-  context_t base;
-} wl_context_t;
+typedef struct wl_hw_context_t {
+  hw_context_t base;
+} wl_hw_context_t;
 
-wl_context_t *
-wl_context_create(
+wl_hw_context_t *
+wl_hw_context_create(
   wl_target_t *target,
   int32_t width,
   int32_t height)
@@ -32,14 +33,14 @@ wl_context_create(
 }
 
 void
-wl_context_destroy(
-  wl_context_t *context)
+wl_hw_context_destroy(
+  wl_hw_context_t *context)
 {
 }
 
 bool
-wl_context_resize(
-  wl_context_t *context,
+wl_hw_context_resize(
+  wl_hw_context_t *context,
   int32_t width,
   int32_t height)
 {
@@ -47,13 +48,13 @@ wl_context_resize(
 }
 
 void
-wl_context_present(
-  wl_context_t *context)
+wl_hw_context_present(
+  wl_hw_context_t *context)
 {
 }
 
 #else
 
-const int wl_context = 0;
+const int wl_hw_context = 0;
 
 #endif /* HAS_WAYLAND */
diff --git a/src/implem/wayland/wl_context.h b/src/implem/wayland/wl_hw_context.h
similarity index 72%
rename from src/implem/wayland/wl_context.h
rename to src/implem/wayland/wl_hw_context.h
index af2723e5..93ab90af 100644
--- a/src/implem/wayland/wl_context.h
+++ b/src/implem/wayland/wl_hw_context.h
@@ -8,35 +8,34 @@
 /*                                                                        */
 /**************************************************************************/
 
-#ifndef __WL_CONTEXT_H
-#define __WL_CONTEXT_H
+#ifndef __WL_HW_CONTEXT_H
+#define __WL_HW_CONTEXT_H
 
 #include <stdint.h>
 #include <stdbool.h>
 
-#include "../color.h"
 #include "wl_target.h"
 
-typedef struct wl_context_t wl_context_t;
+typedef struct wl_hw_context_t wl_hw_context_t;
 
-wl_context_t *
-wl_context_create(
+wl_hw_context_t *
+wl_hw_context_create(
   wl_target_t *target,
   int32_t width,
   int32_t height);
 
 void
-wl_context_destroy(
-  wl_context_t *context);
+wl_hw_context_destroy(
+  wl_hw_context_t *context);
 
 bool
-wl_context_resize(
-  wl_context_t *context,
+wl_hw_context_resize(
+  wl_hw_context_t *context,
   int32_t width,
   int32_t height);
 
 void
-wl_context_present(
-  wl_context_t *context);
+wl_hw_context_present(
+  wl_hw_context_t *context);
 
-#endif /* __WL_CONTEXT_H */
+#endif /* __WL_HW_CONTEXT_H */
diff --git a/src/implem/wayland/wl_sw_context.c b/src/implem/wayland/wl_sw_context.c
new file mode 100644
index 00000000..8eefe361
--- /dev/null
+++ b/src/implem/wayland/wl_sw_context.c
@@ -0,0 +1,60 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifdef HAS_WAYLAND
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "../config.h"
+#include "../context_internal.h"
+#include "../sw_context_internal.h"
+#include "wl_target.h"
+
+typedef struct wl_sw_context_t {
+  sw_context_t base;
+} wl_sw_context_t;
+
+wl_sw_context_t *
+wl_sw_context_create(
+  wl_target_t *target,
+  int32_t width,
+  int32_t height)
+{
+  return NULL;
+}
+
+void
+wl_sw_context_destroy(
+  wl_sw_context_t *context)
+{
+}
+
+bool
+wl_sw_context_resize(
+  wl_sw_context_t *context,
+  int32_t width,
+  int32_t height)
+{
+  return false;
+}
+
+void
+wl_sw_context_present(
+  wl_sw_context_t *context)
+{
+}
+
+#else
+
+const int wl_sw_context = 0;
+
+#endif /* HAS_WAYLAND */
diff --git a/src/implem/wayland/wl_sw_context.h b/src/implem/wayland/wl_sw_context.h
new file mode 100644
index 00000000..5672cc69
--- /dev/null
+++ b/src/implem/wayland/wl_sw_context.h
@@ -0,0 +1,41 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifndef __WL_SW_CONTEXT_H
+#define __WL_SW_CONTEXT_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "wl_target.h"
+
+typedef struct wl_sw_context_t wl_sw_context_t;
+
+wl_sw_context_t *
+wl_sw_context_create(
+  wl_target_t *target,
+  int32_t width,
+  int32_t height);
+
+void
+wl_sw_context_destroy(
+  wl_sw_context_t *context);
+
+bool
+wl_sw_context_resize(
+  wl_sw_context_t *context,
+  int32_t width,
+  int32_t height);
+
+void
+wl_sw_context_present(
+  wl_sw_context_t *context);
+
+#endif /* __WL_SW_CONTEXT_H */
diff --git a/src/implem/x11/x11_hw_context.c b/src/implem/x11/x11_hw_context.c
new file mode 100644
index 00000000..d8e47fe1
--- /dev/null
+++ b/src/implem/x11/x11_hw_context.c
@@ -0,0 +1,99 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifdef HAS_X11
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <assert.h>
+
+#include <xcb/xcb.h>
+
+#include "../config.h"
+#include "../color.h"
+#include "../context_internal.h"
+#include "../hw_context_internal.h"
+#include "x11_backend_internal.h"
+#include "x11_target.h"
+
+typedef struct x11_hw_context_t {
+  hw_context_t base;
+  xcb_window_t wid;
+} x11_hw_context_t;
+
+x11_hw_context_t *
+x11_hw_context_create(
+  x11_target_t *target,
+  int32_t width,
+  int32_t height)
+{
+  assert(target != NULL);
+  assert(target->wid != XCB_WINDOW_NONE);
+  assert(width > 0);
+  assert(height > 0);
+
+  x11_hw_context_t *context =
+    (x11_hw_context_t *)calloc(1, sizeof(x11_hw_context_t));
+  if (context == NULL) {
+    return NULL;
+  }
+
+  context->base.base.width = width;
+  context->base.base.height = height;
+  context->wid = target->wid;
+
+  return context;
+}
+
+void
+x11_hw_context_destroy(
+  x11_hw_context_t *context)
+{
+  assert(context != NULL);
+
+  free(context);
+}
+
+bool
+x11_hw_context_resize(
+  x11_hw_context_t *context,
+  int32_t width,
+  int32_t height)
+{
+  assert(context != NULL);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
+  assert(width > 0);
+  assert(height > 0);
+
+  context->base.base.width = width;
+  context->base.base.height = height;
+
+  return true;
+}
+
+void
+x11_hw_context_present(
+  x11_hw_context_t *context)
+{
+  assert(context != NULL);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
+  assert(context->wid != XCB_WINDOW_NONE);
+
+}
+
+#else
+
+const int x11_hw_context = 0;
+
+#endif /* HAS_X11 */
diff --git a/src/implem/x11/x11_context.h b/src/implem/x11/x11_hw_context.h
similarity index 72%
rename from src/implem/x11/x11_context.h
rename to src/implem/x11/x11_hw_context.h
index 3d0c4bfb..b53d4a7a 100644
--- a/src/implem/x11/x11_context.h
+++ b/src/implem/x11/x11_hw_context.h
@@ -8,35 +8,34 @@
 /*                                                                        */
 /**************************************************************************/
 
-#ifndef __X11_CONTEXT_H
-#define __X11_CONTEXT_H
+#ifndef __X11_HW_CONTEXT_H
+#define __X11_HW_CONTEXT_H
 
 #include <stdint.h>
 #include <stdbool.h>
 
-#include "../color.h"
 #include "x11_target.h"
 
-typedef struct x11_context_t x11_context_t;
+typedef struct x11_hw_context_t x11_hw_context_t;
 
-x11_context_t *
-x11_context_create(
+x11_hw_context_t *
+x11_hw_context_create(
   x11_target_t *target,
   int32_t width,
   int32_t height);
 
 void
-x11_context_destroy(
-  x11_context_t *context);
+x11_hw_context_destroy(
+  x11_hw_context_t *context);
 
 bool
-x11_context_resize(
-  x11_context_t *context,
+x11_hw_context_resize(
+  x11_hw_context_t *context,
   int32_t width,
   int32_t height);
 
 void
-x11_context_present(
-  x11_context_t *context);
+x11_hw_context_present(
+  x11_hw_context_t *context);
 
-#endif /* __X11_CONTEXT_H */
+#endif /* __X11_HW_CONTEXT_H */
diff --git a/src/implem/x11/x11_context.c b/src/implem/x11/x11_sw_context.c
similarity index 76%
rename from src/implem/x11/x11_context.c
rename to src/implem/x11/x11_sw_context.c
index 077fecdb..aa9a2f2a 100644
--- a/src/implem/x11/x11_context.c
+++ b/src/implem/x11/x11_sw_context.c
@@ -22,18 +22,19 @@
 #include "../config.h"
 #include "../color.h"
 #include "../context_internal.h"
+#include "../sw_context_internal.h"
 #include "x11_backend_internal.h"
 #include "x11_target.h"
 
-typedef struct x11_context_t {
-  context_t base;
+typedef struct x11_sw_context_t {
+  sw_context_t base;
   xcb_image_t *img;
   xcb_window_t wid;
   xcb_gcontext_t cid;
-} x11_context_t;
+} x11_sw_context_t;
 
 static xcb_image_t *
-_x11_context_create_image(
+_x11_sw_context_create_image(
   xcb_connection_t *c,
   uint8_t depth,
   int32_t width,
@@ -64,8 +65,8 @@ _x11_context_create_image(
   return img;
 }
 
-x11_context_t *
-x11_context_create(
+x11_sw_context_t *
+x11_sw_context_create(
   x11_target_t *target,
   int32_t width,
   int32_t height)
@@ -75,8 +76,8 @@ x11_context_create(
   assert(width > 0);
   assert(height > 0);
 
-  x11_context_t *context =
-    (x11_context_t *)calloc(1, sizeof(x11_context_t));
+  x11_sw_context_t *context =
+    (x11_sw_context_t *)calloc(1, sizeof(x11_sw_context_t));
   if (context == NULL) {
     return NULL;
   }
@@ -84,7 +85,7 @@ x11_context_create(
   // TODO: allow xcb / SHM
   color_t_ *data = NULL;
   xcb_image_t *img =
-    _x11_context_create_image(x11_back->c, x11_back->screen->root_depth,
+    _x11_sw_context_create_image(x11_back->c, x11_back->screen->root_depth,
                               width, height, &data);
   if (img == NULL) {
     assert(data == NULL);
@@ -97,9 +98,9 @@ x11_context_create(
   xcb_create_gc(x11_back->c, cid, target->wid,
                 XCB_GC_GRAPHICS_EXPOSURES, (uint32_t[]){ 1 });
 
+  context->base.base.width = width;
+  context->base.base.height = height;
   context->base.data = data;
-  context->base.width = width;
-  context->base.height = height;
   context->img = img;
   context->wid = target->wid;
   context->cid = cid;
@@ -108,8 +109,8 @@ x11_context_create(
 }
 
 void
-x11_context_destroy(
-  x11_context_t *context)
+x11_sw_context_destroy(
+  x11_sw_context_t *context)
 {
   assert(context != NULL);
 
@@ -126,48 +127,48 @@ x11_context_destroy(
 }
 
 bool
-x11_context_resize(
-  x11_context_t *context,
+x11_sw_context_resize(
+  x11_sw_context_t *context,
   int32_t width,
   int32_t height)
 {
   assert(context != NULL);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
   assert(context->base.data != NULL);
-  assert(context->base.width > 0);
-  assert(context->base.height > 0);
   assert(context->img != NULL);
   assert(width > 0);
   assert(height > 0);
 
   color_t_ *data = NULL;
   xcb_image_t *img =
-    _x11_context_create_image(x11_back->c, x11_back->screen->root_depth,
-                              width, height, &data);
+    _x11_sw_context_create_image(x11_back->c, x11_back->screen->root_depth,
+                                 width, height, &data);
   if (img == NULL) {
     assert(data == NULL);
     return false;
   }
   assert(data != NULL);
 
-  _context_copy_to_buffer(&context->base, data, width, height);
+  _sw_context_copy_to_buffer(&context->base, data, width, height);
 
   xcb_image_destroy(context->img);
 
+  context->base.base.width = width;
+  context->base.base.height = height;
   context->base.data = data;
-  context->base.width = width;
-  context->base.height = height;
   context->img = img;
 
   return true;
 }
 
 void
-x11_context_present(
-  x11_context_t *context)
+x11_sw_context_present(
+  x11_sw_context_t *context)
 {
   assert(context != NULL);
-  assert(context->base.width > 0);
-  assert(context->base.height > 0);
+  assert(context->base.base.width > 0);
+  assert(context->base.base.height > 0);
   assert(context->img != NULL);
   assert(context->wid != XCB_WINDOW_NONE);
   assert(context->cid != XCB_NONE);
@@ -179,6 +180,6 @@ x11_context_present(
 
 #else
 
-const int x11_context = 0;
+const int x11_sw_context = 0;
 
 #endif /* HAS_X11 */
diff --git a/src/implem/x11/x11_sw_context.h b/src/implem/x11/x11_sw_context.h
new file mode 100644
index 00000000..ead42101
--- /dev/null
+++ b/src/implem/x11/x11_sw_context.h
@@ -0,0 +1,41 @@
+/**************************************************************************/
+/*                                                                        */
+/*    Copyright 2022 OCamlPro                                             */
+/*                                                                        */
+/*  All rights reserved. This file is distributed under the terms of the  */
+/*  GNU Lesser General Public License version 2.1, with the special       */
+/*  exception on linking described in the file LICENSE.                   */
+/*                                                                        */
+/**************************************************************************/
+
+#ifndef __X11_SW_CONTEXT_H
+#define __X11_SW_CONTEXT_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "x11_target.h"
+
+typedef struct x11_sw_context_t x11_sw_context_t;
+
+x11_sw_context_t *
+x11_sw_context_create(
+  x11_target_t *target,
+  int32_t width,
+  int32_t height);
+
+void
+x11_sw_context_destroy(
+  x11_sw_context_t *context);
+
+bool
+x11_sw_context_resize(
+  x11_sw_context_t *context,
+  int32_t width,
+  int32_t height);
+
+void
+x11_sw_context_present(
+  x11_sw_context_t *context);
+
+#endif /* __X11_SW_CONTEXT_H */
diff --git a/src/stubs/ml_tags.h b/src/stubs/ml_tags.h
index ae28d6f9..729b954c 100644
--- a/src/stubs/ml_tags.h
+++ b/src/stubs/ml_tags.h
@@ -260,12 +260,4 @@ typedef enum comp_op_tag_t {
   TAG_OP_LUMINOSITY       = 25
 } comp_op_tag_t;
 
-typedef enum backend_tag_t {
-  TAG_CANVAS  = 0,
-  TAG_GDI     = 1,
-  TAG_QUARTZ  = 2,
-  TAG_X11     = 3,
-  TAG_WAYLAND = 4
-} backend_tag_t;
-
 #endif /* __ML_TAGS_H */