Move fallback tick handling to compositor thread

android_webview/browser/browser_view_renderer.cc

 // Copyright 2014 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 "android_webview/browser/browser_view_renderer.h"
 
 #include <utility>
 
 #include "android_webview/browser/browser_view_renderer_client.h"
 #include "android_webview/browser/child_frame.h"
@@ skipping 14 matching lines @@
 #include "third_party/skia/include/core/SkPictureRecorder.h"
 #include "ui/gfx/geometry/scroll_offset.h"
 #include "ui/gfx/geometry/vector2d_conversions.h"
 
 namespace android_webview {
 
 namespace {
 
 const double kEpsilon = 1e-8;
 
-const int64_t kFallbackTickTimeoutInMilliseconds = 100;
-
 // Used to calculate memory allocation. Determined experimentally.
 const size_t kMemoryMultiplier = 20;
 const size_t kBytesPerPixel = 4;
 const size_t kMemoryAllocationStep = 5 * 1024 * 1024;
 uint64_t g_memory_override_in_bytes = 0u;
 
 const void* const kBrowserViewRendererUserDataKey =
     &kBrowserViewRendererUserDataKey;
 
 class BrowserViewRendererUserData : public base::SupportsUserData::Data {
@@ skipping 52 matching lines @@
       window_visible_(false),
       attached_to_window_(false),
       hardware_enabled_(false),
       dip_scale_(0.f),
       page_scale_factor_(1.f),
       min_page_scale_factor_(0.f),
       max_page_scale_factor_(0.f),
       on_new_picture_enable_(false),
       clear_view_(false),
       offscreen_pre_raster_(false),
-      fallback_tick_pending_(false),
       next_compositor_id_(1) {}
 
 BrowserViewRenderer::~BrowserViewRenderer() {
   DCHECK(compositor_map_.empty());
 }
 
 void BrowserViewRenderer::RegisterWithWebContents(
     content::WebContents* web_contents) {
   web_contents->SetUserData(kBrowserViewRendererUserDataKey,
                             new BrowserViewRendererUserData(this));
@@ skipping 105 matching lines @@
 
   shared_renderer_state_.InitializeHardwareDrawIfNeededOnUI();
 
   if (!CanOnDraw()) {
     return false;
   }
 
   shared_renderer_state_.SetScrollOffsetOnUI(last_on_draw_scroll_offset_);
   hardware_enabled_ = true;
 
-  return CompositeHw();
-}
-
-bool BrowserViewRenderer::CompositeHw() {
-  CancelFallbackTick();
-
   ReturnResourceFromParent();
   UpdateMemoryPolicy();
 
   ParentCompositorDrawConstraints parent_draw_constraints =
       shared_renderer_state_.GetParentDrawConstraintsOnUI();
   gfx::Size surface_size(size_);
   gfx::Rect viewport(surface_size);
   gfx::Rect clip = viewport;
   gfx::Transform transform_for_tile_priority =
       parent_draw_constraints.transform;
@@ skipping 19 matching lines @@
     TRACE_EVENT_INSTANT0("android_webview", "NoNewFrame",
                          TRACE_EVENT_SCOPE_THREAD);
     return shared_renderer_state_.HasFrameOnUI();
   }
 
   scoped_ptr<ChildFrame> child_frame = make_scoped_ptr(new ChildFrame(
       std::move(frame), GetCompositorID(compositor_),
       viewport_rect_for_tile_priority.IsEmpty(), transform_for_tile_priority,
       offscreen_pre_raster_, parent_draw_constraints.is_layer));
 
-  // Uncommitted frame can happen with consecutive fallback ticks.
   ReturnUnusedResource(shared_renderer_state_.PassUncommittedFrameOnUI());
   shared_renderer_state_.SetCompositorFrameOnUI(std::move(child_frame));
   return true;
 }
 
 void BrowserViewRenderer::UpdateParentDrawConstraints() {
-  PostInvalidateWithFallback();
+  PostInvalidate();
   ParentCompositorDrawConstraints parent_draw_constraints =
       shared_renderer_state_.GetParentDrawConstraintsOnUI();
   client_->ParentDrawConstraintsUpdated(parent_draw_constraints);
 }
 
 void BrowserViewRenderer::ReturnUnusedResource(
     scoped_ptr<ChildFrame> child_frame) {
   if (!child_frame.get() || !child_frame->frame.get())
     return;
 
@@ skipping 62 matching lines @@
 
 void BrowserViewRenderer::ClearView() {
   TRACE_EVENT_INSTANT0("android_webview",
                        "BrowserViewRenderer::ClearView",
                        TRACE_EVENT_SCOPE_THREAD);
   if (clear_view_)
     return;
 
   clear_view_ = true;
   // Always invalidate ignoring the compositor to actually clear the webview.
-  PostInvalidateWithFallback();
+  PostInvalidate();
 }
 
 void BrowserViewRenderer::SetOffscreenPreRaster(bool enable) {
   if (offscreen_pre_raster_ != enable && compositor_)
     UpdateMemoryPolicy();
 
   offscreen_pre_raster_ = enable;
 }
 
 void BrowserViewRenderer::SetIsPaused(bool paused) {
@@ skipping 312 matching lines @@
       scaled_overscroll_delta - rounded_overscroll_delta;
   gfx::Vector2dF fling_velocity_pixels =
       gfx::ScaleVector2d(current_fling_velocity, physical_pixel_scale);
 
   client_->DidOverscroll(rounded_overscroll_delta, fling_velocity_pixels);
 }
 
 void BrowserViewRenderer::PostInvalidate() {
   TRACE_EVENT_INSTANT0("android_webview", "BrowserViewRenderer::PostInvalidate",
                        TRACE_EVENT_SCOPE_THREAD);
-  PostInvalidateWithFallback();
-}
-
-void BrowserViewRenderer::PostInvalidateWithFallback() {
-  // Always call view invalidate. We rely the Android framework to ignore the
-  // invalidate when it's not needed such as when view is not visible.
   client_->PostInvalidate();
-
-  // Stop fallback ticks when one of these is true.
-  // 1) Webview is paused. Also need to check we are not in clear view since
-  // paused, offscreen still expect clear view to recover.
-  // 2) If we are attached to window and the window is not visible (eg when
-  // app is in the background). We are sure in this case the webview is used
-  // "on-screen" but that updates are not needed when in the background.
-  bool throttle_fallback_tick =
-      (is_paused_ && !clear_view_) || (attached_to_window_ && !window_visible_);

[boliu, 2016/03/11 17:43:09]

So, according to IsClientVisible, visible = !is_paused_ && (!attached_to_window_
|| window_visible_);

And compositor will commit or animate etc when invisible.

So, the first point is bogus after we enabled page visibility, and second point
is superceded by visibility. Cool :)

-
-  if (throttle_fallback_tick || fallback_tick_pending_)
-    return;
-
-  DCHECK(post_fallback_tick_.IsCancelled());
-  DCHECK(fallback_tick_fired_.IsCancelled());
-
-  post_fallback_tick_.Reset(base::Bind(&BrowserViewRenderer::PostFallbackTick,
-                                       base::Unretained(this)));
-  ui_task_runner_->PostTask(FROM_HERE, post_fallback_tick_.callback());
-  fallback_tick_pending_ = true;
-}
-
-void BrowserViewRenderer::CancelFallbackTick() {
-  post_fallback_tick_.Cancel();
-  fallback_tick_fired_.Cancel();
-  fallback_tick_pending_ = false;
-}
-
-void BrowserViewRenderer::PostFallbackTick() {
-  DCHECK(fallback_tick_fired_.IsCancelled());
-  TRACE_EVENT0("android_webview", "BrowserViewRenderer::PostFallbackTick");
-  post_fallback_tick_.Cancel();
-  fallback_tick_fired_.Reset(base::Bind(&BrowserViewRenderer::FallbackTickFired,
-                                        base::Unretained(this)));
-  ui_task_runner_->PostDelayedTask(
-      FROM_HERE, fallback_tick_fired_.callback(),
-      base::TimeDelta::FromMilliseconds(kFallbackTickTimeoutInMilliseconds));
-}
-
-void BrowserViewRenderer::FallbackTickFired() {
-  TRACE_EVENT0("android_webview", "BrowserViewRenderer::FallbackTickFired");
-  // This should only be called if OnDraw or DrawGL did not come in time, which
-  // means fallback_tick_pending_ must still be true.
-  DCHECK(fallback_tick_pending_);
-  fallback_tick_fired_.Cancel();
-  fallback_tick_pending_ = false;
-  if (compositor_) {
-    if (hardware_enabled_ && !size_.IsEmpty()) {
-      CompositeHw();
-    } else {
-      ForceFakeCompositeSW();
-    }
-  }
-}
-
-void BrowserViewRenderer::ForceFakeCompositeSW() {
-  DCHECK(compositor_);
-  SkBitmap bitmap;
-  bitmap.allocN32Pixels(1, 1);
-  bitmap.eraseColor(0);
-  SkCanvas canvas(bitmap);
-  CompositeSW(&canvas);
 }
 
 bool BrowserViewRenderer::CompositeSW(SkCanvas* canvas) {
   DCHECK(compositor_);
-  CancelFallbackTick();
   ReturnResourceFromParent();
   return compositor_->DemandDrawSw(canvas);
 }
 
 void BrowserViewRenderer::UpdateCompositorIsActive() {
   if (compositor_) {
     compositor_->SetIsActive(!is_paused_ &&
                              (!attached_to_window_ || window_visible_));
   }
 }
 
 std::string BrowserViewRenderer::ToString() const {
   std::string str;
   base::StringAppendF(&str, "is_paused: %d ", is_paused_);
   base::StringAppendF(&str, "view_visible: %d ", view_visible_);
   base::StringAppendF(&str, "window_visible: %d ", window_visible_);
   base::StringAppendF(&str, "dip_scale: %f ", dip_scale_);
   base::StringAppendF(&str, "page_scale_factor: %f ", page_scale_factor_);
-  base::StringAppendF(&str, "fallback_tick_pending: %d ",
-                      fallback_tick_pending_);
   base::StringAppendF(&str, "view size: %s ", size_.ToString().c_str());
   base::StringAppendF(&str, "attached_to_window: %d ", attached_to_window_);
   base::StringAppendF(&str,
                       "global visible rect: %s ",
                       last_on_draw_global_visible_rect_.ToString().c_str());
   base::StringAppendF(
       &str, "scroll_offset_dip: %s ", scroll_offset_dip_.ToString().c_str());
   base::StringAppendF(&str,
                       "overscroll_rounding_error_: %s ",
                       overscroll_rounding_error_.ToString().c_str());
   base::StringAppendF(
       &str, "on_new_picture_enable: %d ", on_new_picture_enable_);
   base::StringAppendF(&str, "clear_view: %d ", clear_view_);
   return str;
 }
 
 }  // namespace android_webview