[Impeller] Use specialization constant for blur pipelines decal feature. (#47617)

Minor specialization constant cleanup

Author: jonahwilliams

ci/licenses_golden/licenses_flutter

@@ -3153,10 +3153,8 @@ ORIGIN: ../../../flutter/impeller/entity/shaders/conical_gradient_fill.frag + ..
 ORIGIN: ../../../flutter/impeller/entity/shaders/conical_gradient_ssbo_fill.frag + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/debug/checkerboard.frag + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/debug/checkerboard.vert + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/impeller/entity/shaders/gaussian_blur/gaussian_blur.glsl + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/impeller/entity/shaders/gaussian_blur/gaussian_blur.frag + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/gaussian_blur/gaussian_blur.vert + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/impeller/entity/shaders/gaussian_blur/gaussian_blur_noalpha_decal.frag + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/impeller/entity/shaders/gaussian_blur/gaussian_blur_noalpha_nodecal.frag + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/geometry/points.comp + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/geometry/uv.comp + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/shaders/glyph_atlas.frag + ../../../flutter/LICENSE
@@ -5907,10 +5905,8 @@ FILE: ../../../flutter/impeller/entity/shaders/conical_gradient_fill.frag
 FILE: ../../../flutter/impeller/entity/shaders/conical_gradient_ssbo_fill.frag
 FILE: ../../../flutter/impeller/entity/shaders/debug/checkerboard.frag
 FILE: ../../../flutter/impeller/entity/shaders/debug/checkerboard.vert
-FILE: ../../../flutter/impeller/entity/shaders/gaussian_blur/gaussian_blur.glsl
+FILE: ../../../flutter/impeller/entity/shaders/gaussian_blur/gaussian_blur.frag
 FILE: ../../../flutter/impeller/entity/shaders/gaussian_blur/gaussian_blur.vert
-FILE: ../../../flutter/impeller/entity/shaders/gaussian_blur/gaussian_blur_noalpha_decal.frag
-FILE: ../../../flutter/impeller/entity/shaders/gaussian_blur/gaussian_blur_noalpha_nodecal.frag
 FILE: ../../../flutter/impeller/entity/shaders/geometry/points.comp
 FILE: ../../../flutter/impeller/entity/shaders/geometry/uv.comp
 FILE: ../../../flutter/impeller/entity/shaders/glyph_atlas.frag

impeller/entity/BUILD.gn

@@ -26,8 +26,7 @@ impeller_shaders("entity_shaders") {
     "shaders/color_matrix_color_filter.vert",
     "shaders/conical_gradient_fill.frag",
     "shaders/gaussian_blur/gaussian_blur.vert",
-    "shaders/gaussian_blur/gaussian_blur_noalpha_decal.frag",
-    "shaders/gaussian_blur/gaussian_blur_noalpha_nodecal.frag",
+    "shaders/gaussian_blur/gaussian_blur.frag",
     "shaders/glyph_atlas.frag",
     "shaders/glyph_atlas_color.frag",
     "shaders/glyph_atlas.vert",

impeller/entity/contents/content_context.cc

@@ -317,10 +317,10 @@ ContentContext::ContentContext(
   texture_pipelines_.CreateDefault(*context_, options);
   position_uv_pipelines_.CreateDefault(*context_, options);
   tiled_texture_pipelines_.CreateDefault(*context_, options);
-  gaussian_blur_noalpha_decal_pipelines_.CreateDefault(*context_,
-                                                       options_trianglestrip);
-  gaussian_blur_noalpha_nodecal_pipelines_.CreateDefault(*context_,
-                                                         options_trianglestrip);
+  gaussian_blur_noalpha_decal_pipelines_.CreateDefault(
+      *context_, options_trianglestrip, {/*decal_specialization=*/1});
+  gaussian_blur_noalpha_nodecal_pipelines_.CreateDefault(
+      *context_, options_trianglestrip, {/*decal_specialization=*/0});
   border_mask_blur_pipelines_.CreateDefault(*context_, options_trianglestrip);
   morphology_filter_pipelines_.CreateDefault(*context_, options_trianglestrip);
   color_matrix_color_filter_pipelines_.CreateDefault(*context_,

impeller/entity/contents/content_context.h

@@ -63,9 +63,8 @@
 #include "impeller/entity/yuv_to_rgb_filter.frag.h"
 #include "impeller/entity/yuv_to_rgb_filter.vert.h"
 
+#include "impeller/entity/gaussian_blur.frag.h"
 #include "impeller/entity/gaussian_blur.vert.h"
-#include "impeller/entity/gaussian_blur_noalpha_decal.frag.h"
-#include "impeller/entity/gaussian_blur_noalpha_nodecal.frag.h"
 
 #include "impeller/entity/position_color.vert.h"
 
@@ -130,11 +129,9 @@ using PositionUVPipeline =
 using TiledTexturePipeline =
     RenderPipelineT<TextureFillVertexShader, TiledTextureFillFragmentShader>;
 using GaussianBlurDecalPipeline =
-    RenderPipelineT<GaussianBlurVertexShader,
-                    GaussianBlurNoalphaDecalFragmentShader>;
+    RenderPipelineT<GaussianBlurVertexShader, GaussianBlurFragmentShader>;
 using GaussianBlurPipeline =
-    RenderPipelineT<GaussianBlurVertexShader,
-                    GaussianBlurNoalphaNodecalFragmentShader>;
+    RenderPipelineT<GaussianBlurVertexShader, GaussianBlurFragmentShader>;
 using BorderMaskBlurPipeline =
     RenderPipelineT<BorderMaskBlurVertexShader, BorderMaskBlurFragmentShader>;
 using MorphologyFilterPipeline =

impeller/entity/entity_unittests.cc

@@ -2556,6 +2556,19 @@ TEST_P(EntityTest, SpecializationConstantsAreAppliedToVariants) {
             expected_constants);
 }
 
+TEST_P(EntityTest, BlurSpecializationConstantValuesAreExpected) {
+  auto content_context =
+      ContentContext(GetContext(), TypographerContextSkia::Make());
+
+  auto decal_pipeline = content_context.GetGaussianBlurDecalPipeline({});
+  auto nodecal_pipeline = content_context.GetGaussianBlurPipeline({});
+
+  ASSERT_EQ(decal_pipeline->GetDescriptor().GetSpecializationConstants()[0],
+            /*decal_specialization*/ 1);
+  ASSERT_EQ(nodecal_pipeline->GetDescriptor().GetSpecializationConstants()[0],
+            /*decal_specialization*/ 0);
+}
+
 }  // namespace testing
 }  // namespace impeller
 

impeller/entity/shaders/gaussian_blur/gaussian_blur.glsl renamed to impeller/entity/shaders/gaussian_blur/gaussian_blur.frag

@@ -18,6 +18,8 @@
 #include <impeller/texture.glsl>
 #include <impeller/types.glsl>
 
+layout(constant_id = 0) const int decal_specialization = 0;
+
 uniform f16sampler2D texture_sampler;
 
 uniform BlurInfo {
@@ -33,11 +35,10 @@ uniform BlurInfo {
 blur_info;
 
 f16vec4 Sample(f16sampler2D tex, vec2 coords) {
-#if ENABLE_DECAL_SPECIALIZATION
-  return IPHalfSampleDecal(tex, coords);
-#else
+  if (decal_specialization == 1) {
+    return IPHalfSampleDecal(tex, coords);
+  }
   return texture(tex, coords);
-#endif
 }
 
 in vec2 v_texture_coords;