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 545 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_EQ(source_size.width(), source_bitmap_with_filters.width());
+    DCHECK_EQ(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::GetBackgroundWithFilters(
     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.
 
   // 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 =
+      !frame->current_render_pass->has_transparent_background;
   DCHECK(!frame->current_texture);
 
   // TODO(ajuma): Add support for reference filters once
   // FilterOperations::GetOutsets supports reference filters.
-  if (quad->background_filters.HasReferenceFilter())
-    return scoped_ptr<ScopedResource>();
+  if (apply_background_filters && quad->background_filters.HasReferenceFilter())
+    apply_background_filters = false;
 
   // 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;
   quad->background_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(), window_rect);
   }
 
+  int filtered_device_background_texture_id = 0;
   skia::RefPtr<SkImageFilter> filter = RenderSurfaceFilters::BuildImageFilter(
       quad->background_filters, device_background_texture->size());
 
-  SkBitmap filtered_device_background =
-      ApplyImageFilter(this,
-                       frame->offscreen_context_provider,
-                       quad->rect.origin(),
-                       filter.get(),
-                       device_background_texture.get());
-  if (!filtered_device_background.getTexture())
-    return scoped_ptr<ScopedResource>();
+  SkBitmap filtered_device_background;
+  if (apply_background_filters)
+    filtered_device_background =
+        ApplyImageFilter(this,
+                         frame->offscreen_context_provider,
+                         quad->rect.origin(),
+                         filter.get(),
+                         device_background_texture.get());
+  if (background_changed)
+    *background_changed = (filtered_device_background.getTexture() != NULL);
 
-  GrTexture* texture =
-      reinterpret_cast<GrTexture*>(filtered_device_background.getTexture());
-  int filtered_device_background_texture_id = texture->getTextureHandle();
+  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();
+  } else {
+    lock.reset(new ResourceProvider::ScopedReadLockGL(
+        resource_provider_, device_background_texture->id()));
+    filtered_device_background_texture_id = lock->texture_id();
+  }
 
   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 apply_blend_mode =
+      quad->shared_quad_state->blend_mode != SkXfermode::kSrcOver_Mode;
+  bool background_changed = false;
   scoped_ptr<ScopedResource> background_texture;
-  if (!quad->background_filters.IsEmpty()) {
+  if (!quad->background_filters.IsEmpty() || apply_blend_mode) {
     // 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(
-        frame,
-        quad,
-        contents_device_transform,
-        contents_device_transform_inverse);
+    background_texture =
+        GetBackgroundWithFilters(frame,
+                                 quad,
+                                 contents_device_transform,
+                                 contents_device_transform_inverse,
+                                 &background_changed);
 
     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 18 matching lines @@
       } else {
         filter_bitmap = ApplyImageFilter(this,
                                          frame->offscreen_context_provider,
                                          quad->rect.origin(),
                                          filter.get(),
                                          contents_texture);
       }
     }
   }
 
+  if (background_texture && apply_blend_mode) {
+    filter_bitmap =
+        ApplyBlendModeWithBackdrop(this,
+                                   frame->offscreen_context_provider,
+                                   filter_bitmap,
+                                   contents_texture,
+                                   background_texture.get(),
+                                   quad->shared_quad_state->blend_mode);
+  }
+
   // Draw the background texture if there is one.
-  if (background_texture) {
+  if (background_texture && background_changed) {
     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 1630 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,

[enne (OOO), 2013/11/01 18:49:02]

I still feel a little bit uneasy about this API.  It seems pretty non-obvious at
callsites why this function gets called vs the other one.

Is there some way to make this more clear? Is there any easy way to combine this
with GetFramebufferTexture and have it be more smart, picking the more efficient
copyTexImage2D version when possible and the other copyTexSubImage2D version
when needed?

[rosca, 2013/11/04 17:14:34]

I found a way to avoid using this API. Knaab has added support for RGBA_4444
textures (https://chromiumcodereview.appspot.com/21159007) which does support
alpha channel and RP preallocates it using texImage2D, so I can call
copyTexImage2D on it.
I use RGBA_4444 only when gl has support for texture storage (I tested windows
and mac: windows uses storage, but mac doesn't).

+                                               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,
+                                  0,
+                                  0,
+                                  0,
+                                  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