Accelerate the lighten blendmode if GL_EXT_blend_minmax is enabled.

cc/output/gl_renderer.cc

Index: cc/output/gl_renderer.cc
diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index 0a897f39432a1cb94c3c4bc02805ac02de71d010..67c8d518cbf4d13f5b8210789fb789c1724eb83f 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -338,6 +338,7 @@ GLRenderer::GLRenderer(RendererClient* client,
   capabilities_.allow_rasterize_on_demand = true;
 
   use_sync_query_ = context_caps.gpu.sync_query;
+  use_blend_minmax = context_caps.gpu.blend_minmax;
 
   InitializeSharedObjects();
 }
@@ -701,21 +702,32 @@ static skia::RefPtr<SkImage> ApplyImageFilter(
   return image;
 }
 
-bool GLRenderer::ShouldApplyBlendModeUsingBlendFunc(const DrawQuad* quad) {
-  SkXfermode::Mode blend_mode = quad->shared_quad_state->blend_mode;
-  return blend_mode == SkXfermode::kScreen_Mode ||
+bool GLRenderer::CanApplyBlendModeUsingBlendFunc(SkXfermode::Mode blend_mode) {
+  return (use_blend_minmax && blend_mode == SkXfermode::kLighten_Mode) ||
+         blend_mode == SkXfermode::kScreen_Mode ||
          blend_mode == SkXfermode::kSrcOver_Mode;
 }
 
-void GLRenderer::ApplyBlendModeUsingBlendFunc(const DrawQuad* quad) {
-  DCHECK(ShouldApplyBlendModeUsingBlendFunc(quad));
-  if (quad->shared_quad_state->blend_mode == SkXfermode::kScreen_Mode) {
+void GLRenderer::ApplyBlendModeUsingBlendFunc(SkXfermode::Mode blend_mode) {
+  DCHECK(CanApplyBlendModeUsingBlendFunc(blend_mode));
+
+  // Any modes set here must be reset in RestoreBlendFuncToDefault
+  if (blend_mode == SkXfermode::kScreen_Mode) {
     GLC(gl_, gl_->BlendFunc(GL_ONE_MINUS_DST_COLOR, GL_ONE));
+  } else if (blend_mode == SkXfermode::kLighten_Mode) {
+    GLC(gl_, gl_->BlendFunc(GL_ONE, GL_ONE));
+    GLC(gl_, gl_->BlendEquation(GL_MAX_EXT));
   }
 }
 
-void GLRenderer::RestoreBlendFuncToDefault() {
+void GLRenderer::RestoreBlendFuncToDefault(SkXfermode::Mode blend_mode) {
+  if (blend_mode == SkXfermode::kSrcOver_Mode)
+    return;
+
   GLC(gl_, gl_->BlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA));
+
+  if (blend_mode == SkXfermode::kLighten_Mode)
+    GLC(gl_, gl_->BlendEquation(GL_FUNC_ADD));
 }
 
 static skia::RefPtr<SkImage> ApplyBlendModeWithBackdrop(
@@ -991,8 +1003,10 @@ scoped_ptr<ScopedResource> GLRenderer::GetBackgroundWithFilters(
 
 void GLRenderer::DrawRenderPassQuad(DrawingFrame* frame,
                                     const RenderPassDrawQuad* quad) {
+  SkXfermode::Mode blend_mode = quad->shared_quad_state->blend_mode;
   SetBlendEnabled(quad->ShouldDrawWithBlending() ||
-                  ShouldApplyBlendModeUsingBlendFunc(quad));
+                  (!IsDefaultBlendMode(blend_mode) &&
+                   CanApplyBlendModeUsingBlendFunc(blend_mode)));
 
   ScopedResource* contents_texture =
       render_pass_textures_.get(quad->render_pass_id);
@@ -1011,7 +1025,7 @@ void GLRenderer::DrawRenderPassQuad(DrawingFrame* frame,
   if (!contents_device_transform.GetInverse(&contents_device_transform_inverse))
     return;
 
-  bool need_background_texture = !ShouldApplyBlendModeUsingBlendFunc(quad) ||
+  bool need_background_texture = !CanApplyBlendModeUsingBlendFunc(blend_mode) ||
                                  !quad->background_filters.IsEmpty();
   bool background_changed = false;
   scoped_ptr<ScopedResource> background_texture;
@@ -1066,7 +1080,7 @@ void GLRenderer::DrawRenderPassQuad(DrawingFrame* frame,
     }
   }
 
-  if (background_texture && !ShouldApplyBlendModeUsingBlendFunc(quad)) {
+  if (background_texture && !CanApplyBlendModeUsingBlendFunc(blend_mode)) {

[enne (OOO), 2014/10/07 17:51:17]

I think this CanApplyBlendModeUsingBlendFunc check is redundant here.  Maybe
just DCHECK it?

[Erik Dahlström (inactive), 2014/10/08 15:25:20]

No, I don't think it's redundant, have a look at the rebased version which
hopefully is a bit more clear.

     filter_bitmap =
         ApplyBlendModeWithBackdrop(ScopedUseGrContext::Create(this, frame),
                                    resource_provider_,
@@ -1134,8 +1148,8 @@ void GLRenderer::DrawRenderPassQuad(DrawingFrame* frame,
               contents_resource_lock->target());
   }
 
-  if (ShouldApplyBlendModeUsingBlendFunc(quad))
-    ApplyBlendModeUsingBlendFunc(quad);
+  if (CanApplyBlendModeUsingBlendFunc(blend_mode))
+    ApplyBlendModeUsingBlendFunc(blend_mode);
 
   TexCoordPrecision tex_coord_precision = TexCoordPrecisionRequired(
       gl_,
@@ -1384,8 +1398,8 @@ void GLRenderer::DrawRenderPassQuad(DrawingFrame* frame,
   if (filter_bitmap)
     GLC(gl_, gl_->Flush());
 
-  if (ShouldApplyBlendModeUsingBlendFunc(quad))
-    RestoreBlendFuncToDefault();
+  if (CanApplyBlendModeUsingBlendFunc(blend_mode))
+    RestoreBlendFuncToDefault(blend_mode);
 }
 
 struct SolidColorProgramUniforms {