Added preliminary support for tile rasterization with Ganesh

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 150 matching lines @@
                        int highp_threshold_min)
     : DirectRenderer(client, settings, output_surface, resource_provider),
       offscreen_framebuffer_id_(0),
       shared_geometry_quad_(gfx::RectF(-0.5f, -0.5f, 1.0f, 1.0f)),
       context_(output_surface->context_provider()->Context3d()),
       context_support_(output_surface->context_provider()->ContextSupport()),
       texture_mailbox_deleter_(texture_mailbox_deleter),
       is_backbuffer_discarded_(false),
       visible_(true),
       is_scissor_enabled_(false),
+      scissor_rect_needs_reset_(true),
       stencil_shadow_(false),
       blend_shadow_(false),
       highp_threshold_min_(highp_threshold_min),
       highp_threshold_cache_(0),
       on_demand_tile_raster_resource_id_(0) {
   DCHECK(context_);
   DCHECK(context_support_);
 }
 
 bool GLRenderer::Initialize() {
@@ skipping 2298 matching lines @@
                      gfx::Rect(target_rect.size()),
                      target_rect.size());
   return true;
 }
 
 void GLRenderer::SetScissorTestRect(gfx::Rect scissor_rect) {
   EnsureScissorTestEnabled();
 
   // Don't unnecessarily ask the context to change the scissor, because it
   // may cause undesired GPU pipeline flushes.
-  if (scissor_rect == scissor_rect_)
+  if (scissor_rect == scissor_rect_ && !scissor_rect_needs_reset_)

[reveman, 2013/11/24 21:56:57]

can you explain why we need this now but not before?

[slavi, 2013/11/25 23:13:14]

Ganesh and the GlRendeder are sharing the GL state. Also, Ganesh assumes that
the state will be the same as it was last left. This fixes such a state bug
having to do which scissoring. I believe there's another bug lurking having to
do with GL blend state.

[enne (OOO), 2013/11/25 23:14:10]

Yeah, this looks like it should be a separate patch.  Could you just set the
scissor_rect_ to empty instead of adding a separate boolean?  Also, should
scissor_rect_ be renamed scissor_rect_shadow_ to match the other shadowing
variables and make it more clear?

[slavi, 2013/11/25 23:22:52]

Ok. I'll prepare it as a separate patch.

     return;
 
   scissor_rect_ = scissor_rect;
   FlushTextureQuadCache();
   GLC(context_,
       context_->scissor(scissor_rect.x(),
                         scissor_rect.y(),
                         scissor_rect.width(),
                         scissor_rect.height()));
+
+  scissor_rect_needs_reset_ = false;
 }
 
 void GLRenderer::SetDrawViewport(gfx::Rect window_space_viewport) {
   viewport_ = window_space_viewport;
   GLC(context_, context_->viewport(window_space_viewport.x(),
                                    window_space_viewport.y(),
                                    window_space_viewport.width(),
                                    window_space_viewport.height()));
 }
 
@@ skipping 430 matching lines @@
   stencil_shadow_ = false;
   GLC(context_, context_->enable(GL_BLEND));
   blend_shadow_ = true;
   GLC(context_, context_->blendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA));
   GLC(context_, context_->activeTexture(GL_TEXTURE0));
   program_shadow_ = 0;
 
   // Make sure scissoring starts as disabled.
   is_scissor_enabled_ = false;
   GLC(context_, context_->disable(GL_SCISSOR_TEST));
+  scissor_rect_needs_reset_ = true;
 }
 
 bool GLRenderer::CanUseSkiaGPUBackend() const {
   // The Skia GPU backend requires a stencil buffer.  See ReinitializeGrCanvas
   // implementation.
   return gr_context_ && context_->getContextAttributes().stencil;
 }
 
 bool GLRenderer::IsContextLost() {
   return output_surface_->context_provider()->IsContextLost();
 }
 
 }  // namespace cc