Clean up texenv API a bit and add some docs

citro3d/examples/triangle.rs

@@ -6,7 +6,7 @@
 use citro3d::macros::include_shader;
 use citro3d::math::{AspectRatio, ClipPlanes, Matrix4, Projection, StereoDisplacement};
 use citro3d::render::ClearFlags;
-use citro3d::texenv::{self, CombineFunc, TexEnv};
+use citro3d::texenv;
 use citro3d::{attrib, buffer, render, shader};
 use ctru::prelude::*;
 use ctru::services::gfx::{RawFrameBuffer, Screen, TopScreen3D};
@@ -91,9 +91,10 @@ fn main() {
 
     // Configure the first fragment shading substage to just pass through the vertex color
     // See https://www.opengl.org/sdk/docs/man2/xhtml/glTexEnv.xml for more insight
-    TexEnv::get(&mut instance, texenv::Id(0))
+    instance
+        .texenv(texenv::Stage::new(0).unwrap())
         .src(texenv::Mode::BOTH, texenv::Source::PrimaryColor, None, None)
-        .func(texenv::Mode::BOTH, CombineFunc::Replace);
+        .func(texenv::Mode::BOTH, texenv::CombineFunc::Replace);
 
     let projection_uniform_idx = program.get_uniform("projection").unwrap();
 

citro3d/src/lib.rs

@@ -18,8 +18,12 @@ pub mod shader;
 pub mod texenv;
 pub mod uniform;
 
+use std::cell::OnceCell;
+use std::fmt;
+
 pub use error::{Error, Result};
 
+use self::texenv::TexEnv;
 use self::uniform::Uniform;
 
 pub mod macros {
@@ -31,8 +35,15 @@ pub mod macros {
 /// should instantiate to use this library.
 #[non_exhaustive]
 #[must_use]
-#[derive(Debug)]
-pub struct Instance;
+pub struct Instance {
+    texenvs: [OnceCell<TexEnv>; texenv::TEXENV_COUNT],
+}
+
+impl fmt::Debug for Instance {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Instance").finish_non_exhaustive()
+    }
+}
 
 impl Instance {
     /// Initialize the default `citro3d` instance.
@@ -51,7 +62,17 @@ impl Instance {
     /// Fails if `citro3d` cannot be initialized.
     pub fn with_cmdbuf_size(size: usize) -> Result<Self> {
         if unsafe { citro3d_sys::C3D_Init(size) } {
-            Ok(Self)
+            Ok(Self {
+                texenvs: [
+                    // thank goodness there's only six of them!
+                    OnceCell::new(),
+                    OnceCell::new(),
+                    OnceCell::new(),
+                    OnceCell::new(),
+                    OnceCell::new(),
+                    OnceCell::new(),
+                ],
+            })
         } else {
             Err(Error::FailedToInitialize)
         }
@@ -178,6 +199,27 @@ impl Instance {
     pub fn bind_geometry_uniform(&mut self, index: uniform::Index, uniform: impl Uniform) {
         uniform.bind(self, shader::Type::Geometry, index);
     }
+
+    /// Retrieve the [`TexEnv`] for the given stage, initializing it first if necessary.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use citro3d::texenv;
+    /// # let _runner = test_runner::GdbRunner::default();
+    /// # let mut instance = citro3d::Instance::new().unwrap();
+    /// let stage0 = texenv::Stage::new(0).unwrap();
+    /// let texenv0 = instance.texenv(stage0);
+    /// ```
+    #[doc(alias = "C3D_GetTexEnv")]
+    #[doc(alias = "C3D_TexEnvInit")]
+    pub fn texenv(&mut self, stage: texenv::Stage) -> &mut texenv::TexEnv {
+        let texenv = &mut self.texenvs[stage.0];
+        texenv.get_or_init(|| TexEnv::new(stage));
+        // We have to do this weird unwrap to get a mutable reference,
+        // since there is no `get_mut_or_init` or equivalent
+        texenv.get_mut().unwrap()
+    }
 }
 
 impl Drop for Instance {

citro3d/src/texenv.rs

@@ -1,52 +1,70 @@
-//! Texture environment support. See `<c3d/texenv.h>` for more information.
+//! Texture combiner support. See <https://www.khronos.org/opengl/wiki/Texture_Combiners>
+//! for more details.
 
 use bitflags::bitflags;
 
-use crate::Instance;
-
+/// A texture combiner, also called a "texture environment" (hence the struct name).
+/// See also [`texenv.h` documentation](https://oreo639.github.io/citro3d/texenv_8h.html).
 #[doc(alias = "C3D_TexEnv")]
-pub struct TexEnv<'a> {
+pub struct TexEnv {
     raw: *mut citro3d_sys::C3D_TexEnv,
-    _instance: &'a mut Instance,
 }
 
-impl<'a> TexEnv<'a> {
-    #[doc(alias = "C3D_TexEnvInit")]
-    pub fn set(&self, _instance: &mut Instance, id: Id) {
-        unsafe {
-            // SAFETY: pointee is only copied from, not modified
-            citro3d_sys::C3D_SetTexEnv(id.0, self.raw);
-        }
-    }
+// https://oreo639.github.io/citro3d/texenv_8h.html#a9eda91f8e7252c91f873b1d43e3728b6
+pub(crate) const TEXENV_COUNT: usize = 6;
 
-    pub fn get(instance: &'a mut Instance, id: Id) -> Self {
-        unsafe {
+impl TexEnv {
+    pub(crate) fn new(stage: Stage) -> Self {
+        let mut result = unsafe {
             Self {
-                raw: citro3d_sys::C3D_GetTexEnv(id.0),
-                _instance: instance,
+                raw: citro3d_sys::C3D_GetTexEnv(stage.0 as _),
             }
+        };
+        result.reset();
+        result
+    }
+
+    /// Re-initialize the texture combiner to its default state.
+    pub fn reset(&mut self) {
+        unsafe {
+            citro3d_sys::C3D_TexEnvInit(self.raw);
         }
     }
 
+    /// Configure the source values of the texture combiner.
+    ///
+    /// # Parameters
+    ///
+    /// - `mode`: which [`Mode`]\(s) to set the sourc operand(s) for.
+    /// - `source0`: the first [`Source`] operand to the texture combiner
+    /// - `source1` and `source2`: optional additional [`Source`] operands to use
+    #[doc(alias = "C3D_TexEnvSrc")]
     pub fn src(
         &mut self,
         mode: Mode,
-        s1: Source,
-        s2: Option<Source>,
-        s3: Option<Source>,
+        source0: Source,
+        source1: Option<Source>,
+        source2: Option<Source>,
     ) -> &mut Self {
         unsafe {
             citro3d_sys::C3D_TexEnvSrc(
                 self.raw,
                 mode.bits(),
-                s1 as _,
-                s2.unwrap_or(Source::PrimaryColor) as _,
-                s3.unwrap_or(Source::PrimaryColor) as _,
-            )
+                source0 as _,
+                source1.unwrap_or(Source::PrimaryColor) as _,
+                source2.unwrap_or(Source::PrimaryColor) as _,
+            );
         }
         self
     }
 
+    /// Configure the texture combination function.
+    ///
+    /// # Parameters
+    ///
+    /// - `mode`: the [`Mode`]\(s) the combination function will apply to.
+    /// - `func`: the [`CombineFunc`] used to combine textures.
+    #[doc(alias = "C3D_TexEnvFunc")]
     pub fn func(&mut self, mode: Mode, func: CombineFunc) -> &mut Self {
         unsafe {
             citro3d_sys::C3D_TexEnvFunc(self.raw, mode.bits(), func as _);
@@ -57,17 +75,23 @@ impl<'a> TexEnv<'a> {
 }
 
 bitflags! {
+    /// Whether to operate on colors, alpha values, or both.
     #[doc(alias = "C3D_TexEnvMode")]
     pub struct Mode: citro3d_sys::C3D_TexEnvMode {
+        #[allow(missing_docs)]
         const RGB = citro3d_sys::C3D_RGB;
+        #[allow(missing_docs)]
         const ALPHA = citro3d_sys::C3D_Alpha;
+        #[allow(missing_docs)]
         const BOTH = citro3d_sys::C3D_Both;
     }
 }
 
+/// A source operand of a [`TexEnv`]'s texture combination.
 #[derive(Debug, Clone, Copy)]
 #[repr(u32)]
 #[doc(alias = "GPU_TEVSRC")]
+#[allow(missing_docs)]
 pub enum Source {
     PrimaryColor = ctru_sys::GPU_PRIMARY_COLOR,
     FragmentPrimaryColor = ctru_sys::GPU_FRAGMENT_PRIMARY_COLOR,
@@ -81,9 +105,11 @@ pub enum Source {
     Previous = ctru_sys::GPU_PREVIOUS,
 }
 
+/// The combination function to apply to the [`TexEnv`] operands.
 #[derive(Debug, Clone, Copy)]
 #[repr(u32)]
 #[doc(alias = "GPU_COMBINEFUNC")]
+#[allow(missing_docs)]
 pub enum CombineFunc {
     Replace = ctru_sys::GPU_REPLACE,
     Modulate = ctru_sys::GPU_MODULATE,
@@ -95,5 +121,15 @@ pub enum CombineFunc {
     Dot3Rgba = ctru_sys::GPU_DOT3_RGBA,
 }
 
+/// A texture combination stage identifier. This index doubles as the order
+/// in which texture combinations will be applied.
+// (I think?)
 #[derive(Copy, Clone, Debug)]
-pub struct Id(/* TODO maybe non pub? idk */ pub libc::c_int);
+pub struct Stage(pub(crate) usize);
+
+impl Stage {
+    /// Get a stage index. Valid indices range from 0 to 5.
+    pub fn new(index: usize) -> Option<Self> {
+        (index < 6).then_some(Self(index))
+    }
+}