Bug 1373739 - Make headless widgets hidden by default, matching other…

… platforms. r=bdahl

It seems that my reworking of how the z-index events are sent in the patch
pertaining to active window tracking made it so that we can have headless
widgets default to being invisible again, which matches the behavior on all
other platforms. This then allows us to avoid applying size mode change side
effects while a window/widget is invisible, matching the behavior on Windows and
allowing the relevant web platform tests to pass despite the low screen
resolution with which we run Windows VMs in testing (eg.
open-features-non-integer-height.html).

MozReview-Commit-ID: 3xnaEn7RImP

widget/headless/HeadlessWidget.cpp

@@ -55,7 +55,7 @@ HeadlessWidget::Create(nsIWidget* aParent,
 
   mBounds = aRect;
   mRestoreBounds = aRect;
-  mVisible = true;
+  mVisible = false;
   mEnabled = true;
 
   if (aParent) {
@@ -131,6 +131,8 @@ HeadlessWidget::Show(bool aState)
   // Top-level windows are activated/raised when shown.
   if (aState && mTopLevel == this)
     RaiseWindow();
+
+  ApplySizeModeSideEffects();
 }
 
 bool
@@ -246,18 +248,29 @@ HeadlessWidget::SetSizeMode(nsSizeMode aMode)
   if (aMode == mSizeMode) {
     return;
   }
-  if (mSizeMode == nsSizeMode_Normal) {
-    // Store the last normal size bounds so it can be restored when entering
-    // normal mode again.
-    mRestoreBounds = mBounds;
-  }
 
   nsBaseWidget::SetSizeMode(aMode);
 
   // Normally in real widget backends a window event would be triggered that
   // would cause the window manager to handle resizing the window. In headless
   // the window must manually be resized.
-  switch(aMode) {
+  ApplySizeModeSideEffects();
+}
+
+void
+HeadlessWidget::ApplySizeModeSideEffects()
+{
+  if (!mVisible || mEffectiveSizeMode == mSizeMode) {
+    return;
+  }
+
+  if (mEffectiveSizeMode == nsSizeMode_Normal) {
+    // Store the last normal size bounds so it can be restored when entering
+    // normal mode again.
+    mRestoreBounds = mBounds;
+  }
+
+  switch(mSizeMode) {
   case nsSizeMode_Normal: {
     Resize(mRestoreBounds.x, mRestoreBounds.y, mRestoreBounds.width, mRestoreBounds.height, false);
     break;
@@ -281,6 +294,8 @@ HeadlessWidget::SetSizeMode(nsSizeMode aMode)
   default:
     break;
   }
+
+  mEffectiveSizeMode = mSizeMode;
 }
 
 nsresult

widget/headless/HeadlessWidget.h

@@ -16,7 +16,7 @@ namespace widget {
 class HeadlessWidget : public nsBaseWidget
 {
 public:
-  HeadlessWidget() {}
+  HeadlessWidget() : mEffectiveSizeMode(nsSizeMode_Normal) {}
 
   NS_DECL_ISUPPORTS_INHERITED
 
@@ -95,10 +95,13 @@ class HeadlessWidget : public nsBaseWidget
   nsIWidget* mTopLevel;
   // The size mode before entering fullscreen mode.
   nsSizeMode mLastSizeMode;
+  // The last size mode set while the window was visible.
+  nsSizeMode mEffectiveSizeMode;
   InputContext mInputContext;
   // In headless there is no window manager to track window bounds
   // across size mode changes, so we must track it to emulate.
   LayoutDeviceIntRect mRestoreBounds;
+  void ApplySizeModeSideEffects();
   // Similarly, we must track the active window ourselves in order
   // to dispatch (de)activation events properly.
   void RaiseWindow();