Bug 1642839 - Implement WebRenderLayerManager::SendInvalidRegion() r=jrmuizel

When DWM is disabled, each window does not have own back buffer. They would paint directly to a buffer that was to be displayed by the video card. WM_PAINT via SendInvalidRegion() requests necessary re-paint. With it, RenderCompositorANGLE does not need to disable partial present.

Differential Revision: https://phabricator.services.mozilla.com/D77989

gfx/layers/wr/WebRenderLayerManager.cpp

@@ -671,6 +671,18 @@ void WebRenderLayerManager::WaitOnTransactionProcessed() {
 
 void WebRenderLayerManager::SendInvalidRegion(const nsIntRegion& aRegion) {
   // XXX Webrender does not support invalid region yet.
+
+#ifdef XP_WIN
+  // When DWM is disabled, each window does not have own back buffer. They would
+  // paint directly to a buffer that was to be displayed by the video card.
+  // WM_PAINT via SendInvalidRegion() requests necessary re-paint.
+  const bool needsInvalidate = !gfx::gfxVars::DwmCompositionEnabled();
+#else
+  const bool needsInvalidate = true;
+#endif
+  if (needsInvalidate && WrBridge()) {
+    WrBridge()->SendInvalidateRenderedFrame();
+  }
 }
 
 void WebRenderLayerManager::ScheduleComposite() {

gfx/webrender_bindings/RenderCompositorANGLE.cpp

@@ -928,17 +928,7 @@ void RenderCompositorANGLE::InitializeUsePartialPresent() {
 
 bool RenderCompositorANGLE::UsePartialPresent() { return mUsePartialPresent; }
 
-bool RenderCompositorANGLE::RequestFullRender() {
-  if (!gfx::gfxVars::DwmCompositionEnabled()) {
-    // When DWM is disabled, background window needs to repaint its visible
-    // region with WM_PAINT. But invalid region is not supported yet by
-    // WebRenderLayerManager::SendInvalidRegion(). When partial present is
-    // enabled, there is a case that updated rectangle does not cover the
-    // invalid region. Then requests full render for now.
-    mFullRender = true;
-  }
-  return mFullRender;
-}
+bool RenderCompositorANGLE::RequestFullRender() { return mFullRender; }
 
 uint32_t RenderCompositorANGLE::GetMaxPartialPresentRects() {
   if (!mUsePartialPresent) {

widget/gtk/nsWindow.cpp

@@ -2657,12 +2657,6 @@ gboolean nsWindow::OnExposeEvent(cairo_t* cr) {
     // don't have a compositing window manager, our pixels could be stale.
     GetLayerManager()->SetNeedsComposite(true);
     GetLayerManager()->SendInvalidRegion(region.ToUnknownRegion());
-    if (WebRenderLayerManager* wrlm =
-            GetLayerManager()->AsWebRenderLayerManager()) {
-      if (WebRenderBridgeChild* bridge = wrlm->WrBridge()) {
-        bridge->SendInvalidateRenderedFrame();
-      }
-    }
   }
 
   RefPtr<nsWindow> strongThis(this);