Bug 1561326 - Lazily constrain window size on Windows. r=mattwoodrow

Avoids IPC to get the max texture size until the layer manager is created.

Differential Revision: https://phabricator.services.mozilla.com/D42385

--HG--
extra : moz-landing-system : lando

widget/windows/nsWindow.cpp

@@ -656,6 +656,7 @@ nsWindow::nsWindow(bool aIsChildWindow)
   mIdleService = nullptr;
 
   mSizeConstraintsScale = GetDefaultScale().scale;
+  mMaxTextureSize = -1;  // Will be calculated when layer manager is created.
 
   mRequestFxrOutputPending = false;
 
@@ -1697,14 +1698,13 @@ void nsWindow::SetSizeConstraints(const SizeConstraints& aConstraints) {
     c.mMinSize.height =
         std::max(int32_t(::GetSystemMetrics(SM_CYMINTRACK)), c.mMinSize.height);
   }
-  KnowsCompositor* knowsCompositor = GetLayerManager()->AsKnowsCompositor();
-  if (knowsCompositor) {
-    int32_t maxSize = knowsCompositor->GetMaxTextureSize();
+
+  if (mMaxTextureSize > 0) {
     // We can't make ThebesLayers bigger than this anyway.. no point it letting
     // a window grow bigger as we won't be able to draw content there in
     // general.
-    c.mMaxSize.width = std::min(c.mMaxSize.width, maxSize);
-    c.mMaxSize.height = std::min(c.mMaxSize.height, maxSize);
+    c.mMaxSize.width = std::min(c.mMaxSize.width, mMaxTextureSize);
+    c.mMaxSize.height = std::min(c.mMaxSize.height, mMaxTextureSize);
   }
 
   mSizeConstraintsScale = GetDefaultScale().scale;
@@ -3715,6 +3715,10 @@ bool nsWindow::HasPendingInputEvent() {
 LayerManager* nsWindow::GetLayerManager(PLayerTransactionChild* aShadowManager,
                                         LayersBackend aBackendHint,
                                         LayerManagerPersistence aPersistence) {
+  if (mLayerManager) {
+    return mLayerManager;
+  }
+
   RECT windowRect;
   ::GetClientRect(mWnd, &windowRect);
 
@@ -3750,6 +3754,19 @@ LayerManager* nsWindow::GetLayerManager(PLayerTransactionChild* aShadowManager,
 
   NS_ASSERTION(mLayerManager, "Couldn't provide a valid layer manager.");
 
+  if (mLayerManager) {
+    // Update the size constraints now that the layer manager has been
+    // created.
+    KnowsCompositor* knowsCompositor = mLayerManager->AsKnowsCompositor();
+    if (knowsCompositor) {
+      SizeConstraints c = mSizeConstraints;
+      mMaxTextureSize = knowsCompositor->GetMaxTextureSize();
+      c.mMaxSize.width = std::min(c.mMaxSize.width, mMaxTextureSize);
+      c.mMaxSize.height = std::min(c.mMaxSize.height, mMaxTextureSize);
+      nsBaseWidget::SetSizeConstraints(c);
+    }
+  }
+
   return mLayerManager;
 }
 

widget/windows/nsWindow.h

@@ -690,6 +690,7 @@ class nsWindow final : public nsWindowBase {
   static void InitMouseWheelScrollData();
 
   double mSizeConstraintsScale;  // scale in effect when setting constraints
+  int32_t mMaxTextureSize;
 
   // Pointer events processing and management
   WinPointerEvents mPointerEvents;