Bug 1512416 - [Wayland/OpenGL] Resize wl_elg_window when widget scale changes, r=jhorak"

Differential Revision: https://phabricator.services.mozilla.com/D14404

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

widget/gtk/mozcontainer.cpp

@@ -224,6 +224,33 @@ static gint moz_container_get_scale(MozContainer *container) {
 
   return 1;
 }
+
+void moz_container_scale_changed(MozContainer *container,
+                                 GtkAllocation *aAllocation) {
+  MOZ_ASSERT(!GDK_IS_X11_DISPLAY(gdk_display_get_default()),
+             "moz_container_scale_changed operates on Wayland display only.");
+
+  if (!container->surface) {
+    return;
+  }
+
+  // Set correct scaled/unscaled mozcontainer offset
+  // especially when wl_egl is used but we don't recreate it as Gtk+ does.
+  gint x, y;
+  gdk_window_get_position(gtk_widget_get_window(GTK_WIDGET(container)), &x,
+                          &y);
+  wl_subsurface_set_position(container->subsurface, x, y);
+
+  // Try to only resize wl_egl_window on scale factor change.
+  // It's a bit risky as Gtk+ recreates it at that event.
+  if (container->eglwindow) {
+    gint scale = moz_container_get_scale(container);
+    wl_surface_set_buffer_scale(container->surface,
+                                moz_container_get_scale(container));
+    wl_egl_window_resize(container->eglwindow, aAllocation->width * scale,
+                         aAllocation->height * scale, 0, 0);
+  }
+}
 #endif
 
 void moz_container_map(GtkWidget *widget) {
@@ -511,6 +538,7 @@ struct wl_egl_window *moz_container_get_wl_egl_window(MozContainer *container) {
     container->eglwindow =
         wl_egl_window_create(surface, gdk_window_get_width(window) * scale,
                              gdk_window_get_height(window) * scale);
+    wl_surface_set_buffer_scale(surface, scale);
   }
   return container->eglwindow;
 }

widget/gtk/mozcontainer.h

@@ -96,6 +96,8 @@ struct wl_egl_window *moz_container_get_wl_egl_window(MozContainer *container);
 
 gboolean moz_container_has_wl_egl_window(MozContainer *container);
 gboolean moz_container_surface_needs_clear(MozContainer *container);
+void moz_container_scale_changed(MozContainer *container,
+                                 GtkAllocation *aAllocation);
 #endif
 
 #endif /* __MOZ_CONTAINER_H__ */

widget/gtk/nsWindow.cpp

@@ -3190,6 +3190,22 @@ void nsWindow::OnCompositedChanged() {
   }
 }
 
+void nsWindow::OnScaleChanged(GtkAllocation *aAllocation) {
+#ifdef MOZ_WAYLAND
+  if (mContainer && moz_container_has_wl_egl_window(mContainer)) {
+    // We need to resize wl_egl_window when scale changes.
+    moz_container_scale_changed(mContainer, aAllocation);
+  }
+#endif
+
+  // This eventually propagate new scale to the PuppetWidgets
+  OnDPIChanged();
+
+  // configure_event is already fired before scale-factor signal,
+  // but size-allocate isn't fired by changing scale
+  OnSizeAllocate(aAllocation);
+}
+
 void nsWindow::DispatchDragEvent(EventMessage aMsg,
                                  const LayoutDeviceIntPoint &aRefPoint,
                                  guint aTime) {
@@ -5565,14 +5581,10 @@ static void scale_changed_cb(GtkWidget *widget, GParamSpec *aPSpec,
   if (!window) {
     return;
   }
-  // This eventually propagate new scale to the PuppetWidgets
-  window->OnDPIChanged();
 
-  // configure_event is already fired before scale-factor signal,
-  // but size-allocate isn't fired by changing scale
   GtkAllocation allocation;
   gtk_widget_get_allocation(widget, &allocation);
-  window->OnSizeAllocate(&allocation);
+  window->OnScaleChanged(&allocation);
 }
 
 #if GTK_CHECK_VERSION(3, 4, 0)

widget/gtk/nsWindow.h

@@ -258,6 +258,7 @@ class nsWindow final : public nsBaseWidget {
   void OnDPIChanged(void);
   void OnCheckResize(void);
   void OnCompositedChanged(void);
+  void OnScaleChanged(GtkAllocation* aAllocation);
 
 #ifdef MOZ_X11
   Window mOldFocusWindow;