Backed out 3 changesets (bug 1820066) for causing xpc failures in widget/headless/tests/test_headless.js CLOSED TREE

Backed out changeset 501d93d8c9eb (bug 1820066)
Backed out changeset ec623d25b138 (bug 1820066)
Backed out changeset c34dfd018abb (bug 1820066)

gfx/layers/ipc/CompositorBridgeParent.cpp

@@ -259,9 +259,6 @@ void CompositorBridgeParent::InitSameProcess(widget::CompositorWidget* aWidget,
 
   mWidget = aWidget;
   mRootLayerTreeID = aLayerTreeId;
-#if defined(XP_WIN)
-  mWidget->AsWindows()->SetRootLayerTreeID(mRootLayerTreeID);
-#endif
 
   Initialize();
 }

gfx/thebes/gfxPlatform.cpp

@@ -2807,19 +2807,11 @@ void gfxPlatform::InitWebRenderConfig() {
     gfxVars::SetReuseDecoderDevice(true);
   }
 
-  // SWAP_EFFECT_FLIP_SEQUENTIAL is strongly recommended on Win10+ machines --
-  // DXGI warnings are emitted by the Direct3D11 debug layer if it's not used.
-  //
-  // This avoids bug 1763981, which is only exhibited on Windows 11. (This may
-  // be due to some sort of raciness between the parent and GPU processes when
-  // no separate compositor-HWND is created. Alternatively, it may be a bug in
-  // Win11 DWM's handling of SWAP_EFFECT_SEQUENTIAL.)
-  if (Preferences::GetBool("gfx.webrender.flip-sequential", IsWin10OrLater())) {
+  if (Preferences::GetBool("gfx.webrender.flip-sequential", false)) {
     if (gfxVars::UseWebRenderANGLE()) {
       gfxVars::SetUseWebRenderFlipSequentialWin(true);
     }
   }
-
   if (Preferences::GetBool("gfx.webrender.triple-buffering.enabled", false)) {
     if (gfxVars::UseWebRenderDCompWin() ||
         gfxVars::UseWebRenderFlipSequentialWin()) {

gfx/webrender_bindings/RenderCompositorANGLE.cpp

@@ -263,12 +263,11 @@ bool RenderCompositorANGLE::CreateSwapChain(nsACString& aError) {
         desc.BufferCount = 2;
       }
       desc.SwapEffect = DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL;
-      desc.Scaling = DXGI_SCALING_NONE;
     } else {
       desc.BufferCount = 1;
       desc.SwapEffect = DXGI_SWAP_EFFECT_SEQUENTIAL;
-      desc.Scaling = DXGI_SCALING_STRETCH;
     }
+    desc.Scaling = DXGI_SCALING_NONE;
     desc.Flags = 0;
 
     hr = dxgiFactory2->CreateSwapChainForHwnd(

modules/libpref/init/all.js

@@ -460,7 +460,7 @@ pref("gfx.downloadable_fonts.disable_cache", false);
 pref("gfx.content.azure.backends", "skia");
 
 #ifdef XP_WIN
-  // pref("gfx.webrender.flip-sequential", false);  // no default
+  pref("gfx.webrender.flip-sequential", false);
   pref("gfx.webrender.dcomp-win.enabled", true);
   pref("gfx.webrender.triple-buffering.enabled", true);
 #endif

widget/windows/InProcessWinCompositorWidget.cpp

@@ -360,15 +360,4 @@ void InProcessWinCompositorWidget::ObserveVsync(VsyncObserver* aObserver) {
   }
 }
 
-void InProcessWinCompositorWidget::UpdateCompositorWnd(
-    const HWND aCompositorWnd, const HWND aParentWnd) {
-  MOZ_ASSERT(layers::CompositorThreadHolder::IsInCompositorThread());
-  MOZ_ASSERT(aCompositorWnd && aParentWnd);
-  MOZ_ASSERT(aParentWnd == mWnd);
-
-  // Since we're in the parent process anyway, we can just call SetParent
-  // directly.
-  ::SetParent(aCompositorWnd, aParentWnd);
-  mSetParentCompleted = true;
-}
 }  // namespace mozilla::widget

widget/windows/InProcessWinCompositorWidget.h

@@ -71,7 +71,7 @@ class InProcessWinCompositorWidget final
   nsIWidget* RealWidget() override;
 
   void UpdateCompositorWnd(const HWND aCompositorWnd,
-                           const HWND aParentWnd) override;
+                           const HWND aParentWnd) override {}
   void SetRootLayerTreeID(const layers::LayersId& aRootLayerTreeId) override {}
 
  private:

widget/windows/WinCompositorWidget.cpp

@@ -70,10 +70,10 @@ void WinCompositorWidget::UpdateCompositorWndSizeIfNecessary() {
     return;
   }
 
-  // This code is racing with the compositor, which needs to reparent the
-  // compositor surface to the actual window (mWnd). To avoid racing mutations,
-  // we refuse to proceed until ::SetParent() is called in the parent process.
-  // After the ::SetParent() call, composition is scheduled in
+  // This code is racing with the compositor, which needs to reparent
+  // the compositor surface to the actual window (mWnd). To avoid racing
+  // mutations, we refuse to proceed until ::SetParent() is called in parent
+  // process. After the ::SetParent() call, composition is scheduled in
   // CompositorWidgetParent::UpdateCompositorWnd().
   if (!mSetParentCompleted) {
     // ::SetParent() is not completed yet.