[Impeller] remove varying interpolation for solid colors.

impeller/compiler/shader_lib/impeller/types.glsl

@@ -9,12 +9,6 @@
 #extension GL_AMD_gpu_shader_half_float_fetch : enable
 #extension GL_EXT_shader_explicit_arithmetic_types_float16 : enable
 
-#ifdef IMPELLER_TARGET_OPENGLES
-#define IMPELLER_MAYBE_FLAT
-#else
-#define IMPELLER_MAYBE_FLAT flat
-#endif
-
 #ifndef IMPELLER_TARGET_METAL_IOS
 
 precision mediump sampler2D;

impeller/entity/contents/solid_color_contents.cc

@@ -49,9 +49,12 @@ bool SolidColorContents::Render(const ContentContext& renderer,
                                 const Entity& entity,
                                 RenderPass& pass) const {
   using VS = SolidFillPipeline::VertexShader;
+  using FS = SolidFillPipeline::FragmentShader;
+  auto& host_buffer = renderer.GetTransientsBuffer();
 
   VS::FrameInfo frame_info;
-  frame_info.color =
+  FS::FragInfo frag_info;
+  frag_info.color =
       GetColor().Premultiply() * GetGeometry()->ComputeAlphaCoverage(entity);
 
   PipelineBuilderCallback pipeline_callback =
@@ -60,7 +63,8 @@ bool SolidColorContents::Render(const ContentContext& renderer,
       };
   return ColorSourceContents::DrawGeometry<VS>(
       renderer, entity, pass, pipeline_callback, frame_info,
-      [](RenderPass& pass) {
+      [&frag_info, &host_buffer](RenderPass& pass) {
+        FS::BindFragInfo(pass, host_buffer.EmplaceUniform(frag_info));
         pass.SetCommandLabel("Solid Fill");
         return true;
       });

impeller/entity/entity_unittests.cc

@@ -923,6 +923,7 @@ TEST_P(EntityTest, BlendingModeOptions) {
     auto draw_rect = [&context, &pass, &world_matrix](
                          Rect rect, Color color, BlendMode blend_mode) -> bool {
       using VS = SolidFillPipeline::VertexShader;
+      using FS = SolidFillPipeline::FragmentShader;
 
       VertexBufferBuilder<VS::PerVertexData> vtx_builder;
       {
@@ -947,10 +948,12 @@ TEST_P(EntityTest, BlendingModeOptions) {
 
       VS::FrameInfo frame_info;
       frame_info.mvp = pass.GetOrthographicTransform() * world_matrix;
-      frame_info.color = color.Premultiply();
       VS::BindFrameInfo(
           pass, context.GetTransientsBuffer().EmplaceUniform(frame_info));
-
+      FS::FragInfo frag_info;
+      frag_info.color = color.Premultiply();
+      FS::BindFragInfo(
+          pass, context.GetTransientsBuffer().EmplaceUniform(frame_info));
       return pass.Draw().ok();
     };
 

impeller/entity/shaders/solid_fill.frag

@@ -6,10 +6,13 @@ precision mediump float;
 
 #include <impeller/types.glsl>
 
-IMPELLER_MAYBE_FLAT in f16vec4 v_color;
+uniform FragInfo {
+  vec4 color;
+}
+frag_info;
 
-out f16vec4 frag_color;
+out vec4 frag_color;
 
 void main() {
-  frag_color = v_color;
+  frag_color = frag_info.color;
 }

impeller/entity/shaders/solid_fill.vert

@@ -6,15 +6,11 @@
 
 uniform FrameInfo {
   mat4 mvp;
-  f16vec4 color;
 }
 frame_info;
 
 in vec2 position;
 
-IMPELLER_MAYBE_FLAT out mediump f16vec4 v_color;
-
 void main() {
-  v_color = frame_info.color;
   gl_Position = frame_info.mvp * vec4(position, 0.0, 1.0);
 }

impeller/renderer/shader_stage_compatibility_checker.h

@@ -5,6 +5,10 @@
 #ifndef FLUTTER_IMPELLER_RENDERER_SHADER_STAGE_COMPATIBILITY_CHECKER_H_
 #define FLUTTER_IMPELLER_RENDERER_SHADER_STAGE_COMPATIBILITY_CHECKER_H_
 
+#include <cstddef>
+
+#include "impeller/core/shader_types.h"
+
 namespace impeller {
 /// This is a classed use to check that the input slots of fragment shaders
 /// match the output slots of the vertex shaders.
@@ -58,11 +62,17 @@ class ShaderStageCompatibilityChecker {
 // TODO(https://github.com/flutter/flutter/issues/146852): Make impellerc emit
 // an empty array for output slots.
 struct ClipVertexShader;
+struct SolidFillVertexShader;
 
 template <typename FragmentShaderT>
 class ShaderStageCompatibilityChecker<ClipVertexShader, FragmentShaderT> {
  public:
   static constexpr bool Check() { return true; }
 };
+template <typename FragmentShaderT>
+class ShaderStageCompatibilityChecker<SolidFillVertexShader, FragmentShaderT> {
+ public:
+  static constexpr bool Check() { return true; }
+};
 }  // namespace impeller
 #endif  // FLUTTER_IMPELLER_RENDERER_SHADER_STAGE_COMPATIBILITY_CHECKER_H_