mix-blend-mode implementation for accelerated layers

cc/output/gl_renderer.cc

 // Copyright 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/output/gl_renderer.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 #include <string>
@@ skipping 585 matching lines @@
   // Flush the GL context so rendering results from this context are
   // visible in the compositor's context.
   offscreen_contexts->Context3d()->flush();
 
   // Use the compositor's GL context again.
   renderer->Context()->makeContextCurrent();
 
   return device.accessBitmap(false);
 }
 
-scoped_ptr<ScopedResource> GLRenderer::DrawBackgroundFilters(
+static SkBitmap ApplyBlendModeWithBackdrop(GLRenderer* renderer,
+    ContextProvider* offscreen_contexts,
+    SkBitmap source_bitmap_with_filters,
+    ScopedResource* source_texture_resource,
+    ScopedResource* background_texture_resource,
+    SkXfermode::Mode blendMode) {
+  if (!offscreen_contexts || !offscreen_contexts->GrContext())
+      return source_bitmap_with_filters;
+
+  DCHECK(background_texture_resource);
+  DCHECK(source_texture_resource);
+
+  gfx::Size source_size = source_texture_resource->size();
+  gfx::Size background_size = background_texture_resource->size();
+
+  DCHECK_LE(background_size.width(), source_size.width());
+  DCHECK_LE(background_size.height(), source_size.height());
+
+  int source_texture_with_filters_id;
+  scoped_ptr<ResourceProvider::ScopedReadLockGL> lock;
+  if (source_bitmap_with_filters.getTexture()) {
+      DCHECK(source_size.width() == source_bitmap_with_filters.width());
+      DCHECK(source_size.height() == source_bitmap_with_filters.height());
+      GrTexture* texture =
+          reinterpret_cast<GrTexture*>(source_bitmap_with_filters.getTexture());
+      source_texture_with_filters_id = texture->getTextureHandle();
+  } else {
+      lock.reset(
+          new ResourceProvider::ScopedReadLockGL(renderer->resource_provider(),
+          source_texture_resource->id()));
+      source_texture_with_filters_id = lock->texture_id();
+  }
+
+  ResourceProvider::ScopedReadLockGL lock_background(
+      renderer->resource_provider(), background_texture_resource->id());
+
+  // Flush the compositor context to ensure that textures there are available
+  // in the shared context.  Do this after locking/creating the compositor
+  // texture.
+  renderer->resource_provider()->Flush();
+
+  // Make sure skia uses the correct GL context.
+  offscreen_contexts->Context3d()->makeContextCurrent();
+
+  // Wrap the source texture in a Ganesh platform texture.
+  GrBackendTextureDesc backend_texture_description;
+  backend_texture_description.fConfig = kSkia8888_GrPixelConfig;
+  backend_texture_description.fOrigin = kBottomLeft_GrSurfaceOrigin;
+
+  backend_texture_description.fWidth = source_size.width();
+  backend_texture_description.fHeight = source_size.height();
+  backend_texture_description.fTextureHandle = source_texture_with_filters_id;
+  skia::RefPtr<GrTexture> source_texture =
+      skia::AdoptRef(offscreen_contexts->GrContext()->wrapBackendTexture(
+          backend_texture_description));
+
+  backend_texture_description.fWidth = background_size.width();
+  backend_texture_description.fHeight = background_size.height();
+  backend_texture_description.fTextureHandle = lock_background.texture_id();
+  skia::RefPtr<GrTexture> background_texture =
+      skia::AdoptRef(offscreen_contexts->GrContext()->wrapBackendTexture(
+          backend_texture_description));
+
+  // Place the platform texture inside an SkBitmap.
+  SkBitmap source;
+  source.setConfig(SkBitmap::kARGB_8888_Config,
+      source_size.width(), source_size.height());
+  skia::RefPtr<SkGrPixelRef> source_pixel_ref =
+      skia::AdoptRef(new SkGrPixelRef(source_texture.get()));
+  source.setPixelRef(source_pixel_ref.get());
+
+  SkBitmap background;
+  background.setConfig(SkBitmap::kARGB_8888_Config,
+      background_size.width(), background_size.height());
+  skia::RefPtr<SkGrPixelRef> background_pixel_ref =
+      skia::AdoptRef(new SkGrPixelRef(background_texture.get()));
+  background.setPixelRef(background_pixel_ref.get());
+
+  // Create a scratch texture for backing store.
+  GrTextureDesc desc;
+  desc.fFlags = kRenderTarget_GrTextureFlagBit | kNoStencil_GrTextureFlagBit;
+  desc.fSampleCnt = 0;
+  desc.fWidth = source.width();
+  desc.fHeight = source.height();
+  desc.fConfig = kSkia8888_GrPixelConfig;
+  desc.fOrigin = kBottomLeft_GrSurfaceOrigin;
+  GrAutoScratchTexture scratch_texture(
+      offscreen_contexts->GrContext(), desc, GrContext::kExact_ScratchTexMatch);
+  skia::RefPtr<GrTexture> backing_store =
+      skia::AdoptRef(scratch_texture.detach());
+
+  // Create a device and canvas using that backing store.
+  SkGpuDevice device(offscreen_contexts->GrContext(), backing_store.get());
+  SkCanvas canvas(&device);
+
+  // Draw the source bitmap through the filter to the canvas.
+  canvas.clear(SK_ColorTRANSPARENT);
+  canvas.drawSprite(background, 0, 0);
+  SkPaint paint;
+  paint.setXfermodeMode(blendMode);
+  canvas.drawSprite(source, 0, 0, &paint);
+
+  // Flush skia context so that all the rendered stuff appears on the
+  // texture.
+  offscreen_contexts->GrContext()->flush();
+
+  // Flush the GL context so rendering results from this context are
+  // visible in the compositor's context.
+  offscreen_contexts->Context3d()->flush();
+
+  // Use the compositor's GL context again.
+  renderer->Context()->makeContextCurrent();
+
+  return device.accessBitmap(false);
+}
+
+scoped_ptr<ScopedResource> GLRenderer::CreateBackgroundTextureWithFilters(
     DrawingFrame* frame,
     const RenderPassDrawQuad* quad,
     const gfx::Transform& contents_device_transform,
-    const gfx::Transform& contents_device_transform_inverse) {
+    const gfx::Transform& contents_device_transform_inverse,
+    bool& background_changed) {
   // This method draws a background filter, which applies a filter to any pixels
   // behind the quad and seen through its background.  The algorithm works as
   // follows:
   // 1. Compute a bounding box around the pixels that will be visible through
   // the quad.
   // 2. Read the pixels in the bounding box into a buffer R.
   // 3. Apply the background filter to R, so that it is applied in the pixels'
   // coordinate space.
   // 4. Apply the quad's inverse transform to map the pixels in R into the
   // quad's content space. This implicitly clips R by the content bounds of the
   // quad since the destination texture has bounds matching the quad's content.
   // 5. Draw the background texture for the contents using the same transform as
   // used to draw the contents itself. This is done without blending to replace
   // the current background pixels with the new filtered background.
   // 6. Draw the contents of the quad over drop of the new background with
   // blending, as per usual. The filtered background pixels will show through
   // any non-opaque pixels in this draws.
   //
   // Pixel copies in this algorithm occur at steps 2, 3, 4, and 5.
 
   // TODO(danakj): When this algorithm changes, update
   // LayerTreeHost::PrioritizeTextures() accordingly.
 
   FilterOperations filters =
       RenderSurfaceFilters::Optimize(quad->background_filters);
-  DCHECK(!filters.IsEmpty());
+  DCHECK(!filters.IsEmpty() || quad->blend_mode != SkXfermode::kSrcOver_Mode);
 
   // TODO(danakj): We only allow background filters on an opaque render surface
   // because other surfaces may contain translucent pixels, and the contents
   // behind those translucent pixels wouldn't have the filter applied.
-  if (frame->current_render_pass->has_transparent_background)
-    return scoped_ptr<ScopedResource>();
+  bool apply_background_filters = !filters.IsEmpty() &&
+      !frame->current_render_pass->has_transparent_background;
   DCHECK(!frame->current_texture);
 
   // TODO(danakj): Do a single readback for both the surface and replica and
   // cache the filtered results (once filter textures are not reused).
   gfx::Rect window_rect = gfx::ToEnclosingRect(MathUtil::MapClippedRect(
       contents_device_transform, SharedGeometryQuad().BoundingBox()));
 
   int top, right, bottom, left;
   filters.GetOutsets(&top, &right, &bottom, &left);
   window_rect.Inset(-left, -top, -right, -bottom);
 
   window_rect.Intersect(
       MoveFromDrawToWindowSpace(frame->current_render_pass->output_rect));
 
   scoped_ptr<ScopedResource> device_background_texture =
       ScopedResource::create(resource_provider_);
   if (!device_background_texture->Allocate(window_rect.size(),
                                            ResourceProvider::TextureUsageAny,
                                            RGBA_8888)) {
     return scoped_ptr<ScopedResource>();
   } else {
     ResourceProvider::ScopedWriteLockGL lock(resource_provider_,
                                              device_background_texture->id());
-    GetFramebufferTexture(lock.texture_id(),
-                          device_background_texture->format(),
-                          window_rect);
+    GetFramebufferTextureSubImage(lock.texture_id(),
+                                  gfx::Point(),
+                                  window_rect);
   }
 
-  SkBitmap filtered_device_background =
-      ApplyFilters(this,
-                   frame->offscreen_context_provider,
-                   filters,
-                   device_background_texture.get());
-  if (!filtered_device_background.getTexture())
-    return scoped_ptr<ScopedResource>();
+  int filtered_device_background_texture_id = 0;
 
-  GrTexture* texture =
-      reinterpret_cast<GrTexture*>(filtered_device_background.getTexture());
-  int filtered_device_background_texture_id = texture->getTextureHandle();
+  SkBitmap filtered_device_background;
+  if (apply_background_filters)
+      filtered_device_background = ApplyFilters(this,
+          frame->offscreen_context_provider, filters,
+          device_background_texture.get());
+
+  scoped_ptr<ResourceProvider::ScopedReadLockGL> lock;
+  if (filtered_device_background.getTexture()) {
+      GrTexture* texture =
+          reinterpret_cast<GrTexture*>(filtered_device_background.getTexture());
+      filtered_device_background_texture_id = texture->getTextureHandle();
+      background_changed = true;
+  } else {
+      lock.reset(new ResourceProvider::ScopedReadLockGL(resource_provider_,
+          device_background_texture->id()));
+      filtered_device_background_texture_id = lock->texture_id();
+      background_changed = false;
+  }
 
   scoped_ptr<ScopedResource> background_texture =
       ScopedResource::create(resource_provider_);
   if (!background_texture->Allocate(quad->rect.size(),
                                     ResourceProvider::TextureUsageFramebuffer,
                                     RGBA_8888))
     return scoped_ptr<ScopedResource>();
 
   const RenderPass* target_render_pass = frame->current_render_pass;
   bool using_background_texture =
@@ skipping 50 matching lines @@
   gfx::Transform contents_device_transform =
       frame->window_matrix * frame->projection_matrix * quad_rect_matrix;
   contents_device_transform.FlattenTo2d();
 
   // Can only draw surface if device matrix is invertible.
   gfx::Transform contents_device_transform_inverse(
       gfx::Transform::kSkipInitialization);
   if (!contents_device_transform.GetInverse(&contents_device_transform_inverse))
     return;
 
+  bool applyBlendMode = quad->blend_mode != SkXfermode::kSrcOver_Mode;
+  bool backgroundChanged = false;
   scoped_ptr<ScopedResource> background_texture;
-  if (!quad->background_filters.IsEmpty()) {
+  if (!quad->background_filters.IsEmpty() || applyBlendMode) {
     // The pixels from the filtered background should completely replace the
     // current pixel values.
     bool disable_blending = blend_enabled();
     if (disable_blending)
       SetBlendEnabled(false);
 
-    background_texture = DrawBackgroundFilters(
+    background_texture = CreateBackgroundTextureWithFilters(
         frame,
         quad,
         contents_device_transform,
-        contents_device_transform_inverse);
+        contents_device_transform_inverse,
+        backgroundChanged);
 
     if (disable_blending)
       SetBlendEnabled(true);
   }
 
   // TODO(senorblanco): Cache this value so that we don't have to do it for both
   // the surface and its replica.  Apply filters to the contents texture.
   SkBitmap filter_bitmap;
   SkScalar color_matrix[20];
   bool use_color_matrix = false;
@@ skipping 27 matching lines @@
           color_matrix, optimized_filters.at(0).matrix(), sizeof(color_matrix));
       use_color_matrix = true;
     } else {
       filter_bitmap = ApplyFilters(this,
                                    frame->offscreen_context_provider,
                                    optimized_filters,
                                    contents_texture);
     }
   }
 
+  if (background_texture && applyBlendMode) {
+    filter_bitmap = ApplyBlendModeWithBackdrop(this,
+        frame->offscreen_context_provider, filter_bitmap,
+        contents_texture, background_texture.get(), quad->blend_mode);
+  }
+
   // Draw the background texture if there is one.
-  if (background_texture) {
+  if (background_texture && backgroundChanged) {
     DCHECK(background_texture->size() == quad->rect.size());
     ResourceProvider::ScopedReadLockGL lock(resource_provider_,
                                             background_texture->id());
 
     // The background_texture is oriented the same as the frame buffer. The
     // transform we are copying with has a vertical flip, so flip the contents
     // in the shader to maintain orientation
     bool flip_vertically = true;
 
     CopyTextureToFramebuffer(frame,
@@ skipping 1629 matching lines @@
     scoped_ptr<SkAutoLockPixels> lock,
     scoped_ptr<CopyOutputRequest> request,
     bool success) {
   DCHECK(request->force_bitmap_result());
 
   lock.reset();
   if (success)
     request->SendBitmapResult(bitmap.Pass());
 }
 
+void GLRenderer::GetFramebufferTextureSubImage(unsigned texture_id,
+                                               gfx::Point offset,
+                                               gfx::Rect window_rect) {
+  DCHECK(texture_id);
+  DCHECK_GE(window_rect.x(), 0);
+  DCHECK_GE(window_rect.y(), 0);
+  DCHECK_LE(window_rect.right(), current_surface_size_.width());
+  DCHECK_LE(window_rect.bottom(), current_surface_size_.height());
+
+  GLC(context_, context_->bindTexture(GL_TEXTURE_2D, texture_id));
+  GLC(context_,
+      context_->copyTexSubImage2D(GL_TEXTURE_2D,

[shawnsingh, 2013/09/25 05:33:53]

Will this be certainly fast on all drivers/hardware?  If not, this could be a
deal breaker since this part of the rendering code needs to be predictable and
fast as much as possible.

[rosca, 2013/09/25 18:00:00]

Are you referring to the copyTexSubImage2D function or to copying pixels from
one texture to another in general?
Afaik there are performance concerns regarding copyTexSubImage2D on some mobile
GPUs (https://bugs.webkit.org/show_bug.cgi?id=80870). I should dig into how this
has been worked around and implement GetFramebufferTexture in another, more
reliable way.

+      0,
+      offset.x(),
+      offset.y(),
+      window_rect.x(),
+      window_rect.y(),
+      window_rect.width(),
+      window_rect.height()));
+  GLC(context_, context_->bindTexture(GL_TEXTURE_2D, 0));
+}
+
 void GLRenderer::GetFramebufferTexture(
     unsigned texture_id, ResourceFormat texture_format, gfx::Rect window_rect) {
   DCHECK(texture_id);
   DCHECK_GE(window_rect.x(), 0);
   DCHECK_GE(window_rect.y(), 0);
   DCHECK_LE(window_rect.right(), current_surface_size_.width());
   DCHECK_LE(window_rect.bottom(), current_surface_size_.height());
 
   GLC(context_, context_->bindTexture(GL_TEXTURE_2D, texture_id));
   GLC(context_,
@@ skipping 659 matching lines @@
   // The Skia GPU backend requires a stencil buffer.  See ReinitializeGrCanvas
   // implementation.
   return gr_context_ && context_->getContextAttributes().stencil;
 }
 
 bool GLRenderer::IsContextLost() {
   return (context_->getGraphicsResetStatusARB() != GL_NO_ERROR);
 }
 
 }  // namespace cc