Serve viewport info (start, end, dimensions) rather than linemap

Indexing the viewport lines has a relatively high complexity
versus simply comparing line lengths to viewport width.

vis-lua.c

@@ -531,24 +531,6 @@ static void pushrange(lua_State *L, Filerange *r) {
 	lua_settable(L, -3);
 }
 
-static void pushlinemap(lua_State *L, Win *win) {
-	if (!win || !win->view) {
-		lua_pushnil(L);
-		return;
-	}
-	View *view = win->view;
-	Line *line = view_lines_first(view);
-	size_t lines = view_height_get(view);
-	lua_createtable(L, lines, 0);
-	for (lua_Integer l = 1; l <= lines; l++) {
-		if (!line)
-			break;
-		lua_pushunsigned(L, line->lineno);
-		lua_seti(L, -2, l);
-		line = line->next;
-	}
-}
-
 static Filerange getrange(lua_State *L, int index) {
 	Filerange range = text_range_empty();
 	if (lua_istable(L, index)) {
@@ -1852,8 +1834,16 @@ static const struct luaL_Reg registers_funcs[] = {
  * @tfield Range viewport
  */
 /***
- * A list mapping lines in the viewport to logical lines in the file.
- * @tfield list linemap
+ * The logical line numbers of the first and last visible lines.
+ * @tfield Range view_lines
+ */
+/***
+ * Viewport height, accounting for window decorations.
+ * @tfield int view_height
+ */
+/***
+ * Viewport width, accounting for window decorations.
+ * @tfield int view_width
  */
 /***
  * The window width.
@@ -1894,8 +1884,21 @@ static int window_index(lua_State *L) {
 			return 1;
 		}
 
-		if (strcmp(key, "linemap") == 0) {
-			pushlinemap(L, win);
+		if (strcmp(key, "view_lines") == 0) {
+			Filerange r;
+			r.start = view_lines_first(win->view)->lineno;
+			r.end = view_lines_last(win->view)->lineno;
+			pushrange(L, &r);
+			return 1;
+		}
+
+		if (strcmp(key, "view_width") == 0) {
+			lua_pushunsigned(L, view_width_get(win->view));
+			return 1;
+		}
+
+		if (strcmp(key, "view_height") == 0) {
+			lua_pushunsigned(L, view_height_get(win->view));
 			return 1;
 		}