Bug 1849162 - Clean-up scale management a bit. r=stransky

Always pull and track the scale from the topmost window. Keep that one
always up-to-date, which makes accessing it cheaper.

Differential Revision: https://phabricator.services.mozilla.com/D186465

widget/gtk/MozContainerWayland.cpp

@@ -592,7 +592,7 @@ static void fractional_scale_handle_preferred_scale(
   LOGWAYLAND("%s [%p] scale: %f\n", __func__, window.get(),
              wl_container->current_fractional_scale);
   MOZ_DIAGNOSTIC_ASSERT(window);
-  window->OnScaleChanged(/* aForce = */ true);
+  window->OnScaleChanged(/* aNotify = */ true);
 }
 
 static const struct wp_fractional_scale_v1_listener fractional_scale_listener =
@@ -827,12 +827,8 @@ double moz_container_wayland_get_fractional_scale(MozContainer* container) {
 }
 
 double moz_container_wayland_get_scale(MozContainer* container) {
-  double scale = moz_container_wayland_get_fractional_scale(container);
-  if (scale != 0.0) {
-    return scale;
-  }
   nsWindow* window = moz_container_get_nsWindow(container);
-  return window ? window->FractionalScaleFactor() : 1;
+  return window ? window->FractionalScaleFactor() : 1.0;
 }
 
 void moz_container_wayland_set_commit_to_parent(MozContainer* container) {

widget/gtk/nsWindow.cpp

@@ -399,7 +399,6 @@ nsWindow::nsWindow()
       mCreated(false),
       mHandleTouchEvent(false),
       mIsDragPopup(false),
-      mWindowScaleFactorChanged(true),
       mCompositedScreen(gdk_screen_is_composited(gdk_screen_get_default())),
       mIsAccelerated(false),
       mWindowShouldStartDragging(false),
@@ -4034,7 +4033,7 @@ gboolean nsWindow::OnConfigureEvent(GtkWidget* aWidget,
   // Don't fire configure event for scale changes, we handle that
   // OnScaleChanged event. Skip that for toplevel windows only.
   if (mGdkWindow && IsTopLevelWindowType()) {
-    if (mWindowScaleFactor != gdk_window_get_scale_factor(mGdkWindow)) {
+    if (mCeiledScaleFactor != gdk_window_get_scale_factor(mGdkWindow)) {
       LOG("  scale factor changed to %d,return early",
           gdk_window_get_scale_factor(mGdkWindow));
       return FALSE;
@@ -5285,30 +5284,39 @@ void nsWindow::OnCompositedChanged() {
   mCompositedScreen = gdk_screen_is_composited(gdk_screen_get_default());
 }
 
-void nsWindow::OnScaleChanged(bool aForce) {
-  // Force scale factor recalculation
-  if (!mGdkWindow) {
-    mWindowScaleFactorChanged = true;
+void nsWindow::OnScaleChanged(bool aNotify) {
+  if (!IsTopLevelWindowType()) {
     return;
   }
-  LOG("OnScaleChanged -> %d, frac=%f\n",
-      gdk_window_get_scale_factor(mGdkWindow), FractionalScaleFactor());
+  if (!mGdkWindow) {
+    return;  // We'll get there again when we configure the window.
+  }
+  gint newCeiled = gdk_window_get_scale_factor(mGdkWindow);
+  double newFractional =
+      GdkIsWaylandDisplay()
+          ? moz_container_wayland_get_fractional_scale(mContainer)
+          : 0.0;
+  LOG("OnScaleChanged %d, %f -> %d, %f\n", int(mCeiledScaleFactor),
+      FractionalScaleFactor(), newCeiled, newFractional);
 
-  // Gtk supply us sometimes with doubled events so stay calm in such case.
-  if (!aForce &&
-      gdk_window_get_scale_factor(mGdkWindow) == mWindowScaleFactor) {
+  if (mCeiledScaleFactor == newCeiled &&
+      mFractionalScaleFactor == newFractional) {
+    return;
+  }
+
+  mCeiledScaleFactor = newCeiled;
+  mFractionalScaleFactor = newFractional;
+
+  if (!aNotify) {
     return;
   }
 
   // We pause compositor to avoid rendering of obsoleted remote content which
   // produces flickering.
-  // Re-enable compositor again when remote content is updated or
-  // timeout happens.
+  // Re-enable compositor again when remote content is updated or timeout
+  // happens.
   PauseCompositorFlickering();
 
-  // Force scale factor recalculation
-  mWindowScaleFactorChanged = true;
-
   GtkAllocation allocation;
   gtk_widget_get_allocation(GTK_WIDGET(mContainer), &allocation);
   LayoutDeviceIntSize size = GdkRectToDevicePixels(allocation).Size();
@@ -5730,6 +5738,7 @@ void nsWindow::ConfigureGdkWindow() {
   LOG("nsWindow::ConfigureGdkWindow()");
 
   EnsureGdkWindow();
+  OnScaleChanged(/* aNotify = */ false);
 
 #ifdef MOZ_X11
   if (GdkIsX11Display()) {
@@ -8367,7 +8376,7 @@ static void scale_changed_cb(GtkWidget* widget, GParamSpec* aPSpec,
     return;
   }
 
-  window->OnScaleChanged(/* aForce = */ false);
+  window->OnScaleChanged(/* aNotify = */ true);
 }
 
 static gboolean touch_event_cb(GtkWidget* aWidget, GdkEventTouch* aEvent) {
@@ -8922,57 +8931,30 @@ GtkWindow* nsWindow::GetCurrentTopmostWindow() const {
   return topmostParentWindow;
 }
 
-// We're called from Renderer/Compositor thread where EGL Window size is set.
-// Just return what we have and keep scale update to main thread.
-gint nsWindow::GetCachedCeiledScaleFactor() const { return mWindowScaleFactor; }
-
 gint nsWindow::GdkCeiledScaleFactor() {
-  MOZ_ASSERT(NS_IsMainThread());
-
-  // We depend on notify::scale-factor callback which is reliable for toplevel
-  // windows only, so don't use scale cache for popup windows.
-  if (mWindowType == WindowType::TopLevel && !mWindowScaleFactorChanged) {
-    return mWindowScaleFactor;
+  if (IsTopLevelWindowType()) {
+    return mCeiledScaleFactor;
   }
-
-  GdkWindow* scaledGdkWindow = nullptr;
-  if (GdkIsWaylandDisplay()) {
-    // For popup windows/dialogs with parent window we need to get scale factor
-    // of the topmost window. Otherwise the scale factor of the popup is
-    // not updated during it's hidden.
-    if (mWindowType == WindowType::Popup || mWindowType == WindowType::Dialog) {
-      // Get toplevel window for scale factor:
-      GtkWindow* topmostParentWindow = GetCurrentTopmostWindow();
-      if (topmostParentWindow) {
-        scaledGdkWindow =
-            gtk_widget_get_window(GTK_WIDGET(topmostParentWindow));
-      } else {
-        NS_WARNING("Popup/Dialog has no parent.");
+  if (nsWindow* topmost = GetTopmostWindow()) {
+    return topmost->mCeiledScaleFactor;
   }
-    }
-  }
-  // Fallback for windows which parent has been unrealized.
-  if (!scaledGdkWindow) {
-    scaledGdkWindow = mGdkWindow;
-  }
-  if (scaledGdkWindow) {
-    mWindowScaleFactor = gdk_window_get_scale_factor(scaledGdkWindow);
-    mWindowScaleFactorChanged = false;
-  } else {
-    mWindowScaleFactor = ScreenHelperGTK::GetGTKMonitorScaleFactor();
-  }
-  return mWindowScaleFactor;
+  return ScreenHelperGTK::GetGTKMonitorScaleFactor();
 }
 
 double nsWindow::FractionalScaleFactor() {
 #ifdef MOZ_WAYLAND
-  if (mContainer) {
-    double fractional_scale =
-        moz_container_wayland_get_fractional_scale(mContainer);
+  double fractional_scale = [&] {
+    if (IsTopLevelWindowType()) {
+      return mFractionalScaleFactor;
+    }
+    if (nsWindow* topmost = GetTopmostWindow()) {
+      return topmost->mFractionalScaleFactor;
+    }
+    return 0.0;
+  }();
   if (fractional_scale != 0.0) {
     return fractional_scale;
   }
-  }
 #endif
   return GdkCeiledScaleFactor();
 }
@@ -9743,8 +9725,7 @@ void nsWindow::SetEGLNativeWindowSize(
 
   // SetEGLNativeWindowSize() may be called from Renderer/Compositor thread.
   // In such case use cached scale factor.
-  gint scale =
-      NS_IsMainThread() ? GdkCeiledScaleFactor() : GetCachedCeiledScaleFactor();
+  gint scale = GdkCeiledScaleFactor();
   LOG("nsWindow::SetEGLNativeWindowSize() %d x %d scale %d (unscaled %d x %d)",
       aEGLWindowSize.width, aEGLWindowSize.height, scale,
       aEGLWindowSize.width / scale, aEGLWindowSize.height / scale);

widget/gtk/nsWindow.h

@@ -271,7 +271,7 @@ class nsWindow final : public nsBaseWidget {
   void OnDPIChanged();
   void OnCheckResize();
   void OnCompositedChanged();
-  void OnScaleChanged(bool aForce);
+  void OnScaleChanged(bool aNotify);
   void DispatchResized();
 
   static guint32 sLastButtonPressTime;
@@ -374,7 +374,6 @@ class nsWindow final : public nsBaseWidget {
 
   // HiDPI scale conversion
   gint GdkCeiledScaleFactor();
-  gint GetCachedCeiledScaleFactor() const;
   double FractionalScaleFactor();
 
   // To GDK
@@ -475,7 +474,8 @@ class nsWindow final : public nsBaseWidget {
 
   nsCOMPtr<nsIWidget> mParent;
   PopupType mPopupHint{};
-  mozilla::Atomic<int, mozilla::Relaxed> mWindowScaleFactor{1};
+  mozilla::Atomic<int, mozilla::Relaxed> mCeiledScaleFactor{1};
+  double mFractionalScaleFactor = 0.0;
 
   void UpdateAlpha(mozilla::gfx::SourceSurface* aSourceSurface,
                    nsIntRect aBoundsRect);
@@ -647,7 +647,6 @@ class nsWindow final : public nsBaseWidget {
   bool mHandleTouchEvent : 1;
   // true if this is a drag and drop feedback popup
   bool mIsDragPopup : 1;
-  bool mWindowScaleFactorChanged : 1;
   bool mCompositedScreen : 1;
   bool mIsAccelerated : 1;
   bool mWindowShouldStartDragging : 1;