Bug 1882358 Part 2: Make WebRenderLayerManager track widget size to d…

…etect resizes. r=nical

This changes the resize check to an objective standard of whether or not
the widget has resized, rather than asking the widget if it is in the
process of resizing.

Differential Revision: https://phabricator.services.mozilla.com/D202869

gfx/layers/wr/WebRenderLayerManager.cpp

@@ -96,6 +96,7 @@ bool WebRenderLayerManager::Initialize(
  }
 
  mWrChild = static_cast<WebRenderBridgeChild*>(bridge);
+ mHasFlushedThisChild = false;
 
  TextureFactoryIdentifier textureFactoryIdentifier;
  wr::MaybeIdNamespace idNamespace;
@@ -694,24 +695,30 @@ void WebRenderLayerManager::FlushRendering(wr::RenderReasons aReasons) {
  }
  MOZ_ASSERT(mWidget);
 
- // If value of IsResizingNativeWidget() is nothing, we assume that resizing
- // might happen.
- bool resizing = mWidget && mWidget->IsResizingNativeWidget().valueOr(true);
+ // If widget bounds size is different from the last flush, consider
+ // this to be a resize. It's important to use GetClientSize here,
+ // because that has extra plumbing to support initial display cases
+ // where the widget doesn't yet have real bounds.
+ LayoutDeviceIntSize widgetSize = mWidget->GetClientSize();
+ bool resizing = widgetSize != mFlushWidgetSize;
+ mFlushWidgetSize = widgetSize;
 
  if (resizing) {
  aReasons = aReasons | wr::RenderReasons::RESIZE;
  }
 
- // Limit async FlushRendering to !resizing and Win DComp.
- // XXX relax the limitation
- if (WrBridge()->GetCompositorUseDComp() && !resizing) {
-  cBridge->SendFlushRenderingAsync(aReasons);
- } else if (mWidget->SynchronouslyRepaintOnResize() ||
- StaticPrefs::layers_force_synchronous_resize()) {
+ // Check for the conditions where we we force a sync flush. The first
+ // flush for this child should always be sync. Resizes should be
+ // sometimes be sync. Everything else can be async.
+ if (!mHasFlushedThisChild ||
+  (resizing && (mWidget->SynchronouslyRepaintOnResize() ||
+  StaticPrefs::layers_force_synchronous_resize()))) {
  cBridge->SendFlushRendering(aReasons);
  } else {
  cBridge->SendFlushRenderingAsync(aReasons);
  }
+
+ mHasFlushedThisChild = true;
 }
 
 void WebRenderLayerManager::WaitOnTransactionProcessed() {

gfx/layers/wr/WebRenderLayerManager.h

@@ -226,6 +226,7 @@ class WebRenderLayerManager final : public WindowRenderer {
  nsIWidget* MOZ_NON_OWNING_REF mWidget;
 
  RefPtr<WebRenderBridgeChild> mWrChild;
+ bool mHasFlushedThisChild;
 
  RefPtr<TransactionIdAllocator> mTransactionIdAllocator;
  TransactionId mLatestTransactionId;
@@ -273,6 +274,8 @@ class WebRenderLayerManager final : public WindowRenderer {
  UniquePtr<wr::DisplayListBuilder> mDLBuilder;
 
  ScrollUpdatesMap mPendingScrollUpdates;
+
+ LayoutDeviceIntSize mFlushWidgetSize;
 };
 
 } // namespace layers