Issue SetDrawColorBuffers before clearing buffers in GLES, use clear_buffer_f32_slice instead of clear (gfx-rs#5666)

* Issue SetDrawColorBuffers commands before issuing ClearColor

This is necessary for glClearBuffer calls to work correctly on some machines (e.g. AMD Renoir graphics running on Linux). Without this, glClearBuffer calls are ignored.

* Use clear_buffer_f32_slice instead of gl.clear to suppress WebGL warnings

This fixes the following WebGL warning: "WebGL warning: drawBuffers: `buffers[i]` must be NONE or COLOR_ATTACHMENTi."

When using native OpenGL, it is acceptable to call glDrawBuffers with an array of buffers where i != COLOR_ATTACHMENTi. In WebGL, this is not allowed.

* Run cargo fmt

* Add changes for PR gfx-rsGH-5666 to the CHANGELOG

Author: nickguletskii

CHANGELOG.md

@@ -81,6 +81,8 @@ By @stefnotch in [#5410](https://github.com/gfx-rs/wgpu/pull/5410)
 #### GLES / OpenGL
 
 -  Fix regression on OpenGL (EGL) where non-sRGB still used sRGB [#5642](https://github.com/gfx-rs/wgpu/pull/5642)
+-  Fix `ClearColorF`, `ClearColorU` and `ClearColorI` commands being issued before `SetDrawColorBuffers` [#5666](https://github.com/gfx-rs/wgpu/pull/5666)
+-  Replace `glClear` with `glClearBufferF` because `glDrawBuffers` requires that the ith buffer must be `COLOR_ATTACHMENTi` or `NONE` [#5666](https://github.com/gfx-rs/wgpu/pull/5666)
 
 ## v0.20.0 (2024-04-28)
 

wgpu-hal/src/gles/command.rs

@@ -608,6 +608,13 @@ impl crate::CommandEncoder for super::CommandEncoder {
             depth: 0.0..1.0,
         });
 
+        if !rendering_to_external_framebuffer {
+            // set the draw buffers and states
+            self.cmd_buffer
+                .commands
+                .push(C::SetDrawColorBuffers(desc.color_attachments.len() as u8));
+        }
+
         // issue the clears
         for (i, cat) in desc
             .color_attachments
@@ -638,13 +645,6 @@ impl crate::CommandEncoder for super::CommandEncoder {
             }
         }
 
-        if !rendering_to_external_framebuffer {
-            // set the draw buffers and states
-            self.cmd_buffer
-                .commands
-                .push(C::SetDrawColorBuffers(desc.color_attachments.len() as u8));
-        }
-
         if let Some(ref dsat) = desc.depth_stencil_attachment {
             let clear_depth = !dsat.depth_ops.contains(crate::AttachmentOps::LOAD);
             let clear_stencil = !dsat.stencil_ops.contains(crate::AttachmentOps::LOAD);

wgpu-hal/src/gles/queue.rs

@@ -1075,13 +1075,7 @@ impl super::Queue {
                 {
                     unsafe { self.perform_shader_clear(gl, draw_buffer, *color) };
                 } else {
-                    // Prefer `clear` as `clear_buffer` functions have issues on Sandy Bridge
-                    // on Windows.
-                    unsafe {
-                        gl.draw_buffers(&[glow::COLOR_ATTACHMENT0 + draw_buffer]);
-                        gl.clear_color(color[0], color[1], color[2], color[3]);
-                        gl.clear(glow::COLOR_BUFFER_BIT);
-                    }
+                    unsafe { gl.clear_buffer_f32_slice(glow::COLOR, draw_buffer, color) };
                 }
             }
             C::ClearColorU(draw_buffer, ref color) => {