[Impeller] read from framebuffer for advanced blends on iOS.

impeller/compiler/compiler.cc

@@ -35,6 +35,7 @@ static CompilerBackend CreateMSLCompiler(const spirv_cross::ParsedIR& ir,
   // Metal to AIR must be updated as well.
   sl_options.msl_version =
       spirv_cross::CompilerMSL::Options::make_msl_version(1, 2);
+  sl_options.use_framebuffer_fetch_subpasses = true;
   sl_compiler->set_msl_options(sl_options);
 
   // Sort the float and sampler uniforms according to their declared/decorated

impeller/entity/BUILD.gn

@@ -76,6 +76,22 @@ impeller_shaders("modern_entity_shaders") {
     "shaders/linear_gradient_ssbo_fill.frag",
     "shaders/radial_gradient_ssbo_fill.frag",
     "shaders/sweep_gradient_ssbo_fill.frag",
+    "shaders/blending/ios/framebuffer_blend.vert",
+    "shaders/blending/ios/framebuffer_blend_color.frag",
+    "shaders/blending/ios/framebuffer_blend_colorburn.frag",
+    "shaders/blending/ios/framebuffer_blend_colordodge.frag",
+    "shaders/blending/ios/framebuffer_blend_darken.frag",
+    "shaders/blending/ios/framebuffer_blend_difference.frag",
+    "shaders/blending/ios/framebuffer_blend_exclusion.frag",
+    "shaders/blending/ios/framebuffer_blend_hardlight.frag",
+    "shaders/blending/ios/framebuffer_blend_hue.frag",
+    "shaders/blending/ios/framebuffer_blend_lighten.frag",
+    "shaders/blending/ios/framebuffer_blend_luminosity.frag",
+    "shaders/blending/ios/framebuffer_blend_multiply.frag",
+    "shaders/blending/ios/framebuffer_blend_overlay.frag",
+    "shaders/blending/ios/framebuffer_blend_saturation.frag",
+    "shaders/blending/ios/framebuffer_blend_screen.frag",
+    "shaders/blending/ios/framebuffer_blend_softlight.frag",
   ]
 }
 
@@ -123,6 +139,8 @@ impeller_component("entity") {
     "contents/filters/srgb_to_linear_filter_contents.h",
     "contents/filters/yuv_to_rgb_filter_contents.cc",
     "contents/filters/yuv_to_rgb_filter_contents.h",
+    "contents/framebuffer_blend_contents.cc",
+    "contents/framebuffer_blend_contents.h",
     "contents/gradient_generator.cc",
     "contents/gradient_generator.h",
     "contents/linear_gradient_contents.cc",

impeller/entity/contents/content_context.cc

@@ -172,12 +172,7 @@ ContentContext::ContentContext(std::shared_ptr<Context> context)
     sweep_gradient_ssbo_fill_pipelines_[{}] =
         CreateDefaultPipeline<SweepGradientSSBOFillPipeline>(*context_);
   }
-  sweep_gradient_fill_pipelines_[{}] =
-      CreateDefaultPipeline<SweepGradientFillPipeline>(*context_);
-  rrect_blur_pipelines_[{}] =
-      CreateDefaultPipeline<RRectBlurPipeline>(*context_);
-  texture_blend_pipelines_[{}] =
-      CreateDefaultPipeline<BlendPipeline>(*context_);
+
   blend_color_pipelines_[{}] =
       CreateDefaultPipeline<BlendColorPipeline>(*context_);
   blend_colorburn_pipelines_[{}] =
@@ -207,6 +202,45 @@ ContentContext::ContentContext(std::shared_ptr<Context> context)
       CreateDefaultPipeline<BlendScreenPipeline>(*context_);
   blend_softlight_pipelines_[{}] =
       CreateDefaultPipeline<BlendSoftLightPipeline>(*context_);
+#if FML_OS_IOS
+  framebuffer_blend_color_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendColorPipeline>(*context_);
+  framebuffer_blend_colorburn_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendColorBurnPipeline>(*context_);
+  framebuffer_blend_colordodge_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendColorDodgePipeline>(*context_);
+  framebuffer_blend_darken_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendDarkenPipeline>(*context_);
+  framebuffer_blend_difference_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendDifferencePipeline>(*context_);
+  framebuffer_blend_exclusion_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendExclusionPipeline>(*context_);
+  framebuffer_blend_hardlight_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendHardLightPipeline>(*context_);
+  framebuffer_blend_hue_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendHuePipeline>(*context_);
+  framebuffer_blend_lighten_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendLightenPipeline>(*context_);
+  framebuffer_blend_luminosity_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendLuminosityPipeline>(*context_);
+  framebuffer_blend_multiply_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendMultiplyPipeline>(*context_);
+  framebuffer_blend_overlay_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendOverlayPipeline>(*context_);
+  framebuffer_blend_saturation_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendSaturationPipeline>(*context_);
+  framebuffer_blend_screen_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendScreenPipeline>(*context_);
+  framebuffer_blend_softlight_pipelines_[{}] =
+      CreateDefaultPipeline<FramebufferBlendSoftLightPipeline>(*context_);
+#endif  // FML_OS_IOS
+
+  sweep_gradient_fill_pipelines_[{}] =
+      CreateDefaultPipeline<SweepGradientFillPipeline>(*context_);
+  rrect_blur_pipelines_[{}] =
+      CreateDefaultPipeline<RRectBlurPipeline>(*context_);
+  texture_blend_pipelines_[{}] =
+      CreateDefaultPipeline<BlendPipeline>(*context_);
   texture_pipelines_[{}] = CreateDefaultPipeline<TexturePipeline>(*context_);
   tiled_texture_pipelines_[{}] =
       CreateDefaultPipeline<TiledTexturePipeline>(*context_);