Don't create shader-clear program on GLES if it's not needed

CHANGELOG.md

@@ -160,6 +160,7 @@ By @cwfitzgerald in [#5325](https://github.com/gfx-rs/wgpu/pull/5325).
 #### GLES
 
 - Fixes for being able to use an OpenGL 4.1 core context provided by macOS with wgpu. By @bes in [#5331](https://github.com/gfx-rs/wgpu/pull/5331).
+- Don't create a program for shader-clearing if that workaround isn't required. By @Dinnerbone in [#5348](https://github.com/gfx-rs/wgpu/pull/5348).
 
 ## v0.19.0 (2024-01-17)
 

wgpu-hal/src/gles/adapter.rs

@@ -4,6 +4,7 @@ use std::sync::{atomic::AtomicU8, Arc};
 use wgt::AstcChannel;
 
 use crate::auxil::db;
+use crate::gles::ShaderClearProgram;
 
 // https://webgl2fundamentals.org/webgl/lessons/webgl-data-textures.html
 
@@ -875,7 +876,7 @@ impl super::Adapter {
  unsafe fn create_shader_clear_program(
  gl: &glow::Context,
  es: bool,
- ) -> Option<(glow::Program, glow::UniformLocation)> {
+ ) -> Option<ShaderClearProgram> {
  let program = unsafe { gl.create_program() }.expect("Could not create shader program");
  let vertex = unsafe {
  Self::compile_shader(
@@ -911,7 +912,10 @@ impl super::Adapter {
  unsafe { gl.delete_shader(vertex) };
  unsafe { gl.delete_shader(fragment) };
 
- Some((program, color_uniform_location))
+ Some(ShaderClearProgram {
+ program,
+ color_uniform_location,
+ })
  }
 }
 
@@ -937,9 +941,18 @@ impl crate::Adapter<super::Api> for super::Adapter {
  // Compile the shader program we use for doing manual clears to work around Mesa fastclear
  // bug.
 
- let (shader_clear_program, shader_clear_program_color_uniform_location) = unsafe {
- Self::create_shader_clear_program(gl, self.shared.es)
- .ok_or(crate::DeviceError::ResourceCreationFailed)?
+ let shader_clear_program = if self
+ .shared
+ .workarounds
+ .contains(super::Workarounds::MESA_I915_SRGB_SHADER_CLEAR)
+ {
+ Some(unsafe {
+ Self::create_shader_clear_program(gl, self.shared.es)
+ .ok_or(crate::DeviceError::ResourceCreationFailed)?
+ })
+ } else {
+ // If we don't need the workaround, don't waste time and resources compiling the clear program
+ None
  };
 
  Ok(crate::OpenDevice {
@@ -957,7 +970,6 @@ impl crate::Adapter<super::Api> for super::Adapter {
  copy_fbo: unsafe { gl.create_framebuffer() }
  .map_err(|_| crate::DeviceError::OutOfMemory)?,
  shader_clear_program,
- shader_clear_program_color_uniform_location,
  zero_buffer,
  temp_query_results: Mutex::new(Vec::new()),
  draw_buffer_count: AtomicU8::new(1),

wgpu-hal/src/gles/mod.rs

@@ -264,16 +264,19 @@ pub struct Device {
  render_doc: crate::auxil::renderdoc::RenderDoc,
 }
 
+pub struct ShaderClearProgram {
+ pub program: glow::Program,
+ pub color_uniform_location: glow::UniformLocation,
+}
+
 pub struct Queue {
  shared: Arc<AdapterShared>,
  features: wgt::Features,
  draw_fbo: glow::Framebuffer,
  copy_fbo: glow::Framebuffer,
  /// Shader program used to clear the screen for [`Workarounds::MESA_I915_SRGB_SHADER_CLEAR`]
  /// devices.
- shader_clear_program: glow::Program,
- /// The uniform location of the color uniform in the shader clear program
- shader_clear_program_color_uniform_location: glow::UniformLocation,
+ shader_clear_program: Option<ShaderClearProgram>,
  /// Keep a reasonably large buffer filled with zeroes, so that we can implement `ClearBuffer` of
  /// zeroes by copying from it.
  zero_buffer: glow::Buffer,

wgpu-hal/src/gles/queue.rs

@@ -40,10 +40,14 @@ fn get_z_offset(target: u32, base: &crate::TextureCopyBase) -> u32 {
 impl super::Queue {
  /// Performs a manual shader clear, used as a workaround for a clearing bug on mesa
  unsafe fn perform_shader_clear(&self, gl: &glow::Context, draw_buffer: u32, color: [f32; 4]) {
- unsafe { gl.use_program(Some(self.shader_clear_program)) };
+ let shader_clear = self
+ .shader_clear_program
+ .as_ref()
+ .expect("shader_clear_program should always be set if the workaround is enabled");
+ unsafe { gl.use_program(Some(shader_clear.program)) };
  unsafe {
  gl.uniform_4_f32(
- Some(&self.shader_clear_program_color_uniform_location),
+ Some(&shader_clear.color_uniform_location),
  color[0],
  color[1],
  color[2],