cc: Implement overdraw feedback debugging feature.

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 <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
 #include <limits>
 #include <memory>
 #include <set>
 #include <string>
 #include <vector>
 
+#include "base/barrier_closure.h"
 #include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
@@ skipping 454 matching lines @@
 }
 
 void GLRenderer::ClearFramebuffer(DrawingFrame* frame) {
   // On DEBUG builds, opaque render passes are cleared to blue to easily see
   // regions that were not drawn on the screen.
   if (frame->current_render_pass->has_transparent_background)
     gl_->ClearColor(0, 0, 0, 0);
   else
     gl_->ClearColor(0, 0, 1, 1);
 
-  bool always_clear = false;
+  gl_->ClearStencil(0);
+
+  bool always_clear = overdraw_feedback_;
 #ifndef NDEBUG
   always_clear = true;
 #endif
   if (always_clear || frame->current_render_pass->has_transparent_background) {
     GLbitfield clear_bits = GL_COLOR_BUFFER_BIT;
     if (always_clear)
       clear_bits |= GL_STENCIL_BUFFER_BIT;
     gl_->Clear(clear_bits);
   }
 }
@@ skipping 2077 matching lines @@
   }
 }
 
 void GLRenderer::FinishDrawingFrame(DrawingFrame* frame) {
   if (use_sync_query_) {
     DCHECK(current_sync_query_);
     current_sync_query_->End();
     pending_sync_queries_.push_back(std::move(current_sync_query_));
   }
 
+  swap_buffer_rect_.Union(frame->root_damage_rect);
+  if (overdraw_feedback_)
+    FlushOverdrawFeedback(frame, swap_buffer_rect_);
+
   current_framebuffer_lock_ = nullptr;
-  swap_buffer_rect_.Union(frame->root_damage_rect);
 
   gl_->Disable(GL_BLEND);
   blend_shadow_ = false;
 
   ScheduleCALayers(frame);
   ScheduleOverlays(frame);
 }
 
 void GLRenderer::FinishDrawingQuadList() {
   FlushTextureQuadCache(SHARED_BINDING);
@@ skipping 217 matching lines @@
 void GLRenderer::GetFramebufferPixelsAsync(
     const DrawingFrame* frame,
     const gfx::Rect& rect,
     std::unique_ptr<CopyOutputRequest> request) {
   DCHECK(!request->IsEmpty());
   if (request->IsEmpty())
     return;
   if (rect.IsEmpty())
     return;
 
+  if (overdraw_feedback_)
+    FlushOverdrawFeedback(frame, rect);
+
   gfx::Rect window_rect = MoveFromDrawToWindowSpace(frame, rect);
   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());
 
   if (!request->force_bitmap_result()) {
     bool own_mailbox = !request->has_texture_mailbox();
 
     GLuint texture_id = 0;
@@ skipping 171 matching lines @@
   gl_->CopyTexImage2D(GL_TEXTURE_2D, 0, format, window_rect.x(),
                       window_rect.y(), window_rect.width(),
                       window_rect.height(), 0);
   gl_->BindTexture(GL_TEXTURE_2D, 0);
 }
 
 void GLRenderer::BindFramebufferToOutputSurface(DrawingFrame* frame) {
   current_framebuffer_lock_ = nullptr;
   output_surface_->BindFramebuffer();
 
-  if (output_surface_->HasExternalStencilTest()) {
+  if (overdraw_feedback_) {
+    DCHECK(!output_surface_->HasExternalStencilTest());

[danakj, 2017/01/16 16:02:57]

Can you put in a comment that the output surface should not allow
overdraw_feedback_ by not saying |supports_stencil|.

[reveman, 2017/01/16 18:02:27]

Done.

+    SetupOverdrawFeedback();
+    SetStencilEnabled(true);
+  } else if (output_surface_->HasExternalStencilTest()) {
     output_surface_->ApplyExternalStencil();
     SetStencilEnabled(true);
   } else {
     SetStencilEnabled(false);
   }
 }
 
 bool GLRenderer::BindFramebufferToTexture(DrawingFrame* frame,
                                           const ScopedResource* texture) {
   DCHECK(texture->id());
 
   // Explicitly release lock, otherwise we can crash when try to lock
   // same texture again.
   current_framebuffer_lock_ = nullptr;
 
-  SetStencilEnabled(false);
   gl_->BindFramebuffer(GL_FRAMEBUFFER, offscreen_framebuffer_id_);
   current_framebuffer_lock_ =
       base::MakeUnique<ResourceProvider::ScopedWriteLockGL>(
           resource_provider_, texture->id(), false);
   current_framebuffer_format_ = texture->format();
   unsigned texture_id = current_framebuffer_lock_->texture_id();
   gl_->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
                             texture_id, 0);
+  if (overdraw_feedback_) {
+    if (!offscreen_stencil_renderbuffer_id_)
+      gl_->GenRenderbuffers(1, &offscreen_stencil_renderbuffer_id_);
+    if (texture->size() != offscreen_stencil_renderbuffer_size_) {
+      gl_->BindRenderbuffer(GL_RENDERBUFFER,
+                            offscreen_stencil_renderbuffer_id_);
+      gl_->RenderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX8,
+                               texture->size().width(),
+                               texture->size().height());
+      gl_->BindRenderbuffer(GL_RENDERBUFFER, 0);
+      offscreen_stencil_renderbuffer_size_ = texture->size();
+    }
+    gl_->FramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT,
+                                 GL_RENDERBUFFER,
+                                 offscreen_stencil_renderbuffer_id_);
+  }
 
   DCHECK(gl_->CheckFramebufferStatus(GL_FRAMEBUFFER) ==
              GL_FRAMEBUFFER_COMPLETE ||
          IsContextLost());
+
+  if (overdraw_feedback_) {
+    SetupOverdrawFeedback();
+    SetStencilEnabled(true);
+  } else {
+    SetStencilEnabled(false);
+  }
   return true;
 }
 
 void GLRenderer::SetScissorTestRect(const 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_)
     return;
@@ skipping 93 matching lines @@
       }
     }
   }
   for (auto& iter : program_cache_)
     iter.second->Cleanup(gl_);
   program_cache_.clear();
 
   if (offscreen_framebuffer_id_)
     gl_->DeleteFramebuffers(1, &offscreen_framebuffer_id_);
 
+  if (offscreen_stencil_renderbuffer_id_)
+    gl_->DeleteRenderbuffers(1, &offscreen_stencil_renderbuffer_id_);
+
   ReleaseRenderPassTextures();
 }
 
 void GLRenderer::ReinitializeGLState() {
   is_scissor_enabled_ = false;
   scissor_rect_ = gfx::Rect();
   stencil_shadow_ = false;
   blend_shadow_ = true;
   program_shadow_ = 0;
 
@@ skipping 312 matching lines @@
 
   // The alpha has already been applied when copying the RPDQ to an IOSurface.
   GLfloat alpha = 1;
   gl_->ScheduleCALayerSharedStateCHROMIUM(alpha, is_clipped, clip_rect,
                                           sorting_context_id, gl_transform);
   gl_->ScheduleCALayerCHROMIUM(
       texture_id, contents_rect, ca_layer_overlay->background_color,
       ca_layer_overlay->edge_aa_mask, bounds_rect, filter);
 }
 
+void GLRenderer::SetupOverdrawFeedback() {
+  gl_->StencilFunc(GL_ALWAYS, 1, 0xffffffff);
+  // First two values are ignored as test always passes.
+  gl_->StencilOp(GL_KEEP, GL_KEEP, GL_INCR);
+  gl_->StencilMask(0xff);
+}
+
+void GLRenderer::FlushOverdrawFeedback(const DrawingFrame* frame,
+                                       const gfx::Rect& output_rect) {
+  DCHECK(stencil_shadow_);
+
+  // Test only, keep everything.
+  gl_->StencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
+  gl_->StencilMask(0);
+
+  EnsureScissorTestDisabled();
+  SetBlendEnabled(true);
+
+  PrepareGeometry(SHARED_BINDING);
+
+  const Program* program = GetProgram(ProgramKey::DebugBorder());
+  DCHECK(program && (program->initialized() || IsContextLost()));
+  SetUseProgram(program->program());
+
+  gfx::Transform render_matrix;
+  render_matrix.Translate(0.5 * output_rect.width() + output_rect.x(),
+                          0.5 * output_rect.height() + output_rect.y());
+  render_matrix.Scale(output_rect.width(), output_rect.height());
+  static float gl_matrix[16];
+  GLRenderer::ToGLMatrix(&gl_matrix[0],
+                         frame->projection_matrix * render_matrix);
+  gl_->UniformMatrix4fv(program->matrix_location(), 1, false, &gl_matrix[0]);
+
+  // Produce hinting for the amount of overdraw on screen for each pixel by
+  // drawing hint colors to the framebuffer based on the current stencil value.
+  struct {
+    int category;
+    GLenum func;
+    GLint ref;
+    SkColor color;
+  } stencil_tests[] = {
+      {1, GL_EQUAL, 2, 0x2f0000ff},  // Blue: Overdrawn once.
+      {2, GL_EQUAL, 3, 0x2f00ff00},  // Green: Overdrawn twice.
+      {3, GL_EQUAL, 4, 0x3fff0000},  // Pink: Overdrawn three times.
+      {4, GL_LESS, 4, 0x7fff0000},   // Red: Overdrawn four or more times.
+  };
+
+  // Occlusion queries can be expensive, so only collect trace data if we select
+  // cc.debug.overdraw.
+  bool tracing_enabled;
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(
+      TRACE_DISABLED_BY_DEFAULT("cc.debug.overdraw"), &tracing_enabled);
+
+  // Trace only the root render pass.
+  if (frame->current_render_pass != frame->root_render_pass)
+    tracing_enabled = false;
+
+  auto overdraw = new OverdrawResult;
+  base::Closure barrier = base::BarrierClosure(
+      arraysize(stencil_tests),
+      base::Bind(&GLRenderer::UpdateOverdrawCounter, base::Owned(overdraw)));
+
+  for (const auto& test : stencil_tests) {
+    GLuint query = 0;
+    if (tracing_enabled) {
+      gl_->GenQueriesEXT(1, &query);
+      // TODO(reveman): Use SAMPLES_PASSED_ARB when available for exact amount
+      // of overdraw.
+      gl_->BeginQueryEXT(GL_ANY_SAMPLES_PASSED_EXT, query);
+    }
+
+    gl_->StencilFunc(test.func, test.ref, 0xffffffff);
+    // Transparent color unless color-coding of overdraw is enabled.
+    Float4 color =
+        PremultipliedColor(settings_->show_overdraw_feedback ? test.color : 0);
+    gl_->Uniform4fv(program->color_location(), 1, color.data);
+    gl_->DrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, 0);
+
+    if (query) {
+      gl_->EndQueryEXT(GL_ANY_SAMPLES_PASSED_EXT);
+      context_support_->SignalQuery(
+          query, base::Bind(&GLRenderer::ProcessOverdrawFeedback,
+                            weak_ptr_factory_.GetWeakPtr(), query,
+                            test.category, overdraw, barrier));
+    }
+  }
+}
+
+void GLRenderer::ProcessOverdrawFeedback(unsigned query,
+                                         int category,
+                                         OverdrawResult* overdraw,
+                                         const base::Closure& callback) {
+  if (query) {
+    unsigned result = 0;
+    gl_->GetQueryObjectuivEXT(query, GL_QUERY_RESULT_EXT, &result);
+    gl_->DeleteQueriesEXT(1, &query);
+    if (result)
+      overdraw->insert(category);
+  }
+
+  callback.Run();
+}
+
+// static
+void GLRenderer::UpdateOverdrawCounter(const OverdrawResult* overdraw) {
+  // Report overdraw as multiple of the screen size. ie. 1x for the whole
+  // screen is 1.0. Note: this will always report the worst overdraw on screen
+  // as the overdraw for the whole screen until SAMPLES_PASSED_ARB is supported.
+  TRACE_COUNTER1(TRACE_DISABLED_BY_DEFAULT("cc.debug.overdraw"), "GPU Overdraw",
+                 overdraw->empty() ? 0 : *overdraw->rbegin());
+}
+
 }  // namespace cc