Implement mix-blend-mode in GL renderer using shaders.

cc/output/gl_renderer.h

Index: cc/output/gl_renderer.h
diff --git a/cc/output/gl_renderer.h b/cc/output/gl_renderer.h
index 055e0d6731285f7e27431b84c49fe89fab4d358b..a3bf599ddc19acc6ef8d7aafae0f226bcad3efb1 100644
--- a/cc/output/gl_renderer.h
+++ b/cc/output/gl_renderer.h
@@ -42,6 +42,21 @@ class TextureMailboxDeleter;
 class GeometryBinding;
 class ScopedEnsureFramebufferAllocation;
 
+static const SkXfermode::Mode kDefaultBlendMode = SkXfermode::kSrcOver_Mode;
+static const SkXfermode::Mode kFirstBlendMode = SkXfermode::kScreen_Mode;
+static const SkXfermode::Mode kLastBlendMode = SkXfermode::kLuminosity_Mode;

[Erik Dahlström (inactive), 2014/10/14 13:56:07]

why not use SkXfermode::kLastMode?

[rosca, 2014/10/15 15:33:55]

I thought kLastMode might not necessarily refer to a color blend mode. However,
I doubt they will ever change, so I can use it.

+static const int kNumBlendModes = kLastBlendMode - kFirstBlendMode + 2;

[Erik Dahlström (inactive), 2014/10/14 13:56:07]

Deserves a comment to explain the +2.

[rosca, 2014/10/15 15:33:55]

I will, thanks.

+static inline int index_for_blend_mode(SkXfermode::Mode blend_mode) {
+  return (blend_mode < kFirstBlendMode || blend_mode > kLastBlendMode)
+             ? 0
+             : blend_mode - kFirstBlendMode + 1;
+}
+
+static_assert(
+    kDefaultBlendMode < kFirstBlendMode && kFirstBlendMode < kLastBlendMode,
+    "The order should be: kSrcOver_Mode, kFirstBlendMode, kLastBlendMode");
+static_assert(kNumBlendModes == 16, "There are 16 blend modes.");
+
 // Class that handles drawing of composited render layers using GL.
 class CC_EXPORT GLRenderer : public DirectRenderer {
  public:
@@ -328,22 +343,29 @@ class CC_EXPORT GLRenderer : public DirectRenderer {
 
   const TileCheckerboardProgram* GetTileCheckerboardProgram();
 
-  const RenderPassProgram* GetRenderPassProgram(
-      TexCoordPrecision precision);
+  const RenderPassProgram* GetRenderPassProgram(TexCoordPrecision precision,
+                                                SkXfermode::Mode blend_mode);
   const RenderPassProgramAA* GetRenderPassProgramAA(
-      TexCoordPrecision precision);
+      TexCoordPrecision precision,
+      SkXfermode::Mode blend_mode);
   const RenderPassMaskProgram* GetRenderPassMaskProgram(
-      TexCoordPrecision precision);
+      TexCoordPrecision precision,
+      SkXfermode::Mode blend_mode);
   const RenderPassMaskProgramAA* GetRenderPassMaskProgramAA(
-      TexCoordPrecision precision);
+      TexCoordPrecision precision,
+      SkXfermode::Mode blend_mode);
   const RenderPassColorMatrixProgram* GetRenderPassColorMatrixProgram(
-      TexCoordPrecision precision);
+      TexCoordPrecision precision,
+      SkXfermode::Mode blend_mode);
   const RenderPassColorMatrixProgramAA* GetRenderPassColorMatrixProgramAA(
-      TexCoordPrecision precision);
+      TexCoordPrecision precision,
+      SkXfermode::Mode blend_mode);
   const RenderPassMaskColorMatrixProgram* GetRenderPassMaskColorMatrixProgram(
-      TexCoordPrecision precision);
+      TexCoordPrecision precision,
+      SkXfermode::Mode blend_mode);
   const RenderPassMaskColorMatrixProgramAA*
-      GetRenderPassMaskColorMatrixProgramAA(TexCoordPrecision precision);
+  GetRenderPassMaskColorMatrixProgramAA(TexCoordPrecision precision,
+                                        SkXfermode::Mode blend_mode);
 
   const TextureProgram* GetTextureProgram(
       TexCoordPrecision precision);
@@ -388,18 +410,21 @@ class CC_EXPORT GLRenderer : public DirectRenderer {
       nonpremultiplied_texture_background_program_[NumTexCoordPrecisions];
   TextureProgram texture_io_surface_program_[NumTexCoordPrecisions];
 
-  RenderPassProgram render_pass_program_[NumTexCoordPrecisions];
-  RenderPassProgramAA render_pass_program_aa_[NumTexCoordPrecisions];
-  RenderPassMaskProgram render_pass_mask_program_[NumTexCoordPrecisions];
-  RenderPassMaskProgramAA render_pass_mask_program_aa_[NumTexCoordPrecisions];
+  RenderPassProgram render_pass_program_[NumTexCoordPrecisions][kNumBlendModes];
+  RenderPassProgramAA
+      render_pass_program_aa_[NumTexCoordPrecisions][kNumBlendModes];
+  RenderPassMaskProgram
+      render_pass_mask_program_[NumTexCoordPrecisions][kNumBlendModes];
+  RenderPassMaskProgramAA
+      render_pass_mask_program_aa_[NumTexCoordPrecisions][kNumBlendModes];
   RenderPassColorMatrixProgram
-      render_pass_color_matrix_program_[NumTexCoordPrecisions];
-  RenderPassColorMatrixProgramAA
-      render_pass_color_matrix_program_aa_[NumTexCoordPrecisions];
-  RenderPassMaskColorMatrixProgram
-      render_pass_mask_color_matrix_program_[NumTexCoordPrecisions];
-  RenderPassMaskColorMatrixProgramAA
-      render_pass_mask_color_matrix_program_aa_[NumTexCoordPrecisions];
+      render_pass_color_matrix_program_[NumTexCoordPrecisions][kNumBlendModes];
+  RenderPassColorMatrixProgramAA render_pass_color_matrix_program_aa_
+      [NumTexCoordPrecisions][kNumBlendModes];
+  RenderPassMaskColorMatrixProgram render_pass_mask_color_matrix_program_
+      [NumTexCoordPrecisions][kNumBlendModes];
+  RenderPassMaskColorMatrixProgramAA render_pass_mask_color_matrix_program_aa_
+      [NumTexCoordPrecisions][kNumBlendModes];
 
   VideoYUVProgram video_yuv_program_[NumTexCoordPrecisions];
   VideoYUVAProgram video_yuva_program_[NumTexCoordPrecisions];