render/wgpu: Switch to pipeline-overridable constant for bitmap saturation order toggle

Also call it `late_saturate` instead, to avoid the confusing negation
between the constant name and the (now removed) shader module name.

render/wgpu/shaders/bitmap.wgsl

@@ -10,6 +10,7 @@ struct VertexOutput {
 @group(2) @binding(0) var<uniform> textureTransforms: common__TextureTransforms;
 @group(2) @binding(1) var texture: texture_2d<f32>;
 @group(2) @binding(2) var texture_sampler: sampler;
+override late_saturate: bool = false;
 
 @vertex
 fn main_vertex(in: common__VertexInput) -> VertexOutput {
@@ -27,13 +28,11 @@ fn main_fragment(in: VertexOutput) -> @location(0) vec4<f32> {
     if( color.a > 0.0 ) {
         color = vec4<f32>(color.rgb / color.a, color.a);
         color = color * transforms.mult_color + transforms.add_color;
-        // NOTE: `#EARLY_SATURATE#` is replaced with a boolean value at compile time.
-        // TODO: Switch to pipeline constants once `wgpu` is updated to `0.20`.
-        if (#EARLY_SATURATE# == true) {
+        if (!late_saturate) {
             color = saturate(color);
         }
         color = vec4<f32>(color.rgb * color.a, color.a);
-        if (#EARLY_SATURATE# == false) {
+        if (late_saturate) {
             color = saturate(color);
         }
     }

render/wgpu/src/pipelines.rs

@@ -3,6 +3,7 @@ use crate::layouts::BindLayouts;
 use crate::shaders::Shaders;
 use crate::{MaskState, PosColorVertex, PosVertex};
 use enum_map::{enum_map, Enum, EnumMap};
+use std::collections::HashMap;
 use wgpu::{vertex_attr_array, BlendState};
 
 pub const VERTEX_BUFFERS_DESCRIPTION_POS: [wgpu::VertexBufferLayout; 1] =
@@ -175,8 +176,8 @@ impl Pipelines {
 
         let bitmap_opaque = device.create_render_pipeline(&create_pipeline_descriptor(
             create_debug_label!("Bitmap opaque copy").as_deref(),
-            &shaders.bitmap_late_saturate_shader,
-            &shaders.bitmap_late_saturate_shader,
+            &shaders.bitmap_shader,
+            &shaders.bitmap_shader,
             &bitmap_opaque_pipeline_layout,
             None,
             &[Some(wgpu::ColorTargetState {
@@ -186,6 +187,7 @@ impl Pipelines {
             })],
             &VERTEX_BUFFERS_DESCRIPTION_POS,
             msaa_sample_count,
+            &[("late_saturate".to_owned(), 1.0)].into(),
         ));
 
         let bitmap_opaque_dummy_depth = device.create_render_pipeline(&create_pipeline_descriptor(
@@ -212,6 +214,7 @@ impl Pipelines {
             })],
             &VERTEX_BUFFERS_DESCRIPTION_POS,
             msaa_sample_count,
+            &Default::default(),
         ));
 
         Self {
@@ -235,6 +238,7 @@ fn create_pipeline_descriptor<'a>(
     color_target_state: &'a [Option<wgpu::ColorTargetState>],
     vertex_buffer_layout: &'a [wgpu::VertexBufferLayout<'a>],
     msaa_sample_count: u32,
+    fragment_constants: &'a HashMap<String, f64>,
 ) -> wgpu::RenderPipelineDescriptor<'a> {
     wgpu::RenderPipelineDescriptor {
         label,
@@ -249,7 +253,10 @@ fn create_pipeline_descriptor<'a>(
             module: fragment_shader,
             entry_point: "main_fragment",
             targets: color_target_state,
-            compilation_options: Default::default(),
+            compilation_options: wgpu::PipelineCompilationOptions {
+                constants: fragment_constants,
+                ..Default::default()
+            },
         }),
         primitive: wgpu::PrimitiveState {
             topology: wgpu::PrimitiveTopology::TriangleList,
@@ -314,6 +321,7 @@ fn create_shape_pipeline(
             })],
             vertex_buffers_layout,
             msaa_sample_count,
+            &Default::default(),
         ))
     };
 
@@ -331,6 +339,7 @@ fn create_shape_pipeline(
             })],
             vertex_buffers_layout,
             msaa_sample_count,
+            &Default::default(),
         )),
         |mask_state| match mask_state {
             MaskState::NoMask => mask_render_state(

render/wgpu/src/shaders.rs

@@ -5,14 +5,13 @@ use ruffle_render::shader_source::SHADER_FILTER_COMMON;
 #[derive(Debug)]
 pub struct Shaders {
     pub color_shader: wgpu::ShaderModule,
+    /// This has a pipeline-overridable `bool` constant, `late_saturate`,
+    /// with a default of `false`. It switches to performing saturation
+    /// after re-multiplying the alpha, rather than before. This is used
+    /// for the Stage3D `bitmap_opaque` pipeline, which needs to be able to
+    /// avoid changing initially-in-range rgb values (regadless of whether
+    /// dividing by the alpha value would produce an out-of-range value).
     pub bitmap_shader: wgpu::ShaderModule,
-    /// Like `bitmap_shader` but performs saturation after we've
-    /// re-multiplied the alpha. This is used for the Stage3D
-    /// `bitmap_opaque` pipeline, which needs to able to
-    /// avoid changing initially-in-range rgb values (regadless
-    /// of whether dividing by the alpha value would produce
-    /// an out-of-range value).
-    pub bitmap_late_saturate_shader: wgpu::ShaderModule,
     pub gradient_shader: wgpu::ShaderModule,
     pub copy_srgb_shader: wgpu::ShaderModule,
     pub copy_shader: wgpu::ShaderModule,
@@ -27,16 +26,10 @@ pub struct Shaders {
 impl Shaders {
     pub fn new(device: &wgpu::Device) -> Self {
         let color_shader = make_shader(device, "color.wgsl", include_str!("../shaders/color.wgsl"));
-        let bitmap = include_str!("../shaders/bitmap.wgsl");
         let bitmap_shader = make_shader(
             device,
             "bitmap.wgsl",
-            &bitmap.replace("#EARLY_SATURATE#", "true"),
-        );
-        let bitmap_late_saturate_shader = make_shader(
-            device,
-            "bitmap.wgsl",
-            &bitmap.replace("#EARLY_SATURATE#", "false"),
+            include_str!("../shaders/bitmap.wgsl"),
         );
         let copy_srgb_shader = make_shader(
             device,
@@ -90,7 +83,6 @@ impl Shaders {
         Self {
             color_shader,
             bitmap_shader,
-            bitmap_late_saturate_shader,
             gradient_shader,
             copy_srgb_shader,
             copy_shader,