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eframe/src/epi.rs

@@ -29,7 +29,7 @@ pub struct CreationContext<'s> {
     /// you might want to use later from a [`egui::PaintCallback`].
     #[cfg(feature = "glow")]
     pub gl: Option<std::sync::Arc<glow::Context>>,
-    
+
     /// Can be used to manage GPU resources for custom rendering with WGPU using
     /// [`egui::PaintCallback`]s.
     #[cfg(feature = "wgpu")]

egui-wgpu/src/renderer.rs

@@ -9,6 +9,27 @@ use wgpu::util::DeviceExt as _;
 
 /// A callback function that can be used to compose an [`egui::PaintCallback`] for custom WGPU
 /// rendering.
+///
+/// The callback is composed of two functions: `prepare` and `paint`.
+///
+/// `prepare` is called every frame before `paint`, and can use the passed-in [`wgpu::Device`] and
+/// [`wgpu::Buffer`] to allocate or modify GPU resources such as buffers.
+///
+/// `paint` is called after `prepare` and is given access to the the [`wgpu::RenderPass`] so that it
+/// can issue draw commands.
+///
+/// The final argument of both the `prepare` and `paint` callbacks is a the
+/// [`paint_callback_resources`][crate::renderer::RenderPass::paint_callback_resources].
+/// `paint_callback_resources` has the same lifetime as the Egui render pass, so it can be used to
+/// store buffers, pipelines, and other information that needs to be accessed during the render
+/// pass.
+///
+/// # Example
+///
+/// See the [custom3d_wgpu] demo source for a detailed usage example.
+///
+/// [custom3d_wgpu]:
+///     https://github.com/emilk/egui/blob/master/egui_demo_app/src/apps/custom3d_wgpu.rs
 pub struct CallbackFn {
     prepare: Box<PrepareCallback>,
     paint: Box<PaintCallback>,
@@ -32,6 +53,7 @@ impl CallbackFn {
         Self::default()
     }
 
+    /// Set the prepare callback
     pub fn prepare<F>(mut self, prepare: F) -> Self
     where
         F: Fn(&wgpu::Device, &wgpu::Queue, &mut TypeMap) + Sync + Send + 'static,
@@ -40,6 +62,7 @@ impl CallbackFn {
         self
     }
 
+    /// Set the paint callback
     pub fn paint<F>(mut self, paint: F) -> Self
     where
         F: for<'a, 'b> Fn(PaintCallbackInfo, &'a mut wgpu::RenderPass<'b>, &'b TypeMap)
@@ -375,6 +398,7 @@ impl RenderPass {
                     let cbfn = if let Some(c) = callback.callback.downcast_ref::<CallbackFn>() {
                         c
                     } else {
+                        // We already warned in the `prepare` callback
                         continue;
                     };
 
@@ -539,7 +563,6 @@ impl RenderPass {
         };
     }
 
-    /// Should be called before `execute()`.
     pub fn free_texture(&mut self, id: &egui::TextureId) {
         self.textures.remove(id);
     }
@@ -682,8 +705,7 @@ impl RenderPass {
                     let cbfn = if let Some(c) = callback.callback.downcast_ref::<CallbackFn>() {
                         c
                     } else {
-                        // TODO: Should we warn in the console about this, or provide some other way to
-                        // debug ignored paint callbacks?
+                        tracing::warn!("Unknown paint callback: expected `egui_gpu::CallbackFn`");
                         continue;
                     };
 

egui-wgpu/src/winit.rs

@@ -264,9 +264,6 @@ impl<'a> Painter<'a> {
             for (id, image_delta) in &textures_delta.set {
                 rpass.update_texture(&render_state.device, &render_state.queue, *id, image_delta);
             }
-            for id in &textures_delta.free {
-                rpass.free_texture(id);
-            }
 
             rpass.update_buffers(
                 &render_state.device,
@@ -290,6 +287,13 @@ impl<'a> Painter<'a> {
             }),
         );
 
+        {
+            let mut rpass = render_state.egui_rpass.write();
+            for id in &textures_delta.free {
+                rpass.free_texture(id);
+            }
+        }
+
         // Submit the commands.
         render_state.queue.submit(std::iter::once(encoder.finish()));
 

egui_demo_app/Cargo.toml

@@ -42,11 +42,10 @@ chrono = { version = "0.4", features = ["js-sys", "wasmbind"] }
 eframe = { version = "0.18.0", path = "../eframe", default-features = false }
 egui = { version = "0.18.0", path = "../egui", features = ["extra_debug_asserts"] }
 egui_demo_lib = { version = "0.18.0", path = "../egui_demo_lib", features = ["chrono"] }
-bytemuck = { version = "1.9.1", optional = true }
-pollster = { version = "0.2.5", optional = true }
 
 # Optional dependencies:
 
+bytemuck = { version = "1.9.1", optional = true }
 egui_extras = { version = "0.18.0", optional = true, path = "../egui_extras" }
 
 # feature "http":
@@ -56,6 +55,7 @@ image = { version = "0.24", optional = true, default-features = false, features
   "png",
 ] }
 poll-promise = { version = "0.1", optional = true, default-features = false }
+pollster = { version = "0.2.5", optional = true }
 
 # feature "persistence":
 serde = { version = "1", optional = true, features = ["derive"] }

egui_glow/src/painter.rs

@@ -68,7 +68,18 @@ pub struct Painter {
     destroyed: bool,
 }
 
-// TODO: Documentation
+/// A callback function that can be used to compose an [`egui::PaintCallback`] for custom rendering
+/// with [`glow`].
+///
+/// The callback is passed, the [`egui::PaintCallbackInfo`] and the [`Painter`] which can be used to
+/// access the OpenGL context.
+///
+/// # Example
+///
+/// See the [custom3d_glow] demo source for a detailed usage example.
+///
+/// [custom3d_glow]:
+///     https://github.com/emilk/egui/blob/master/egui_demo_app/src/apps/custom3d_wgpu.rs
 pub struct CallbackFn {
     f: Box<dyn Fn(PaintCallbackInfo, &Painter) + Sync + Send>,
 }