changeset:   468935:3b964face103
tag:         tip
user:        Martin Stransky <stransky@redhat.com>
date:        Wed Apr 10 15:14:32 2019 +0200
summary:     Bug 1508378 - Fix round error when damage rect size/position is odd number and scale factor is used, r=lsalzman

diff --git a/widget/gtk/WindowSurfaceWayland.cpp b/widget/gtk/WindowSurfaceWayland.cpp
--- a/widget/gtk/WindowSurfaceWayland.cpp
+++ b/widget/gtk/WindowSurfaceWayland.cpp
@@ -624,16 +624,33 @@ static void WaylandBufferDelayCommitHand
   } else {
     // Referenced WindowSurfaceWayland is already deleted.
     // Do nothing but just release the mDelayedCommitHandle allocated at
     // WindowSurfaceWayland::CommitWaylandBuffer().
     free(aSurface);
   }
 }
 
+void WindowSurfaceWayland::CalcRectScale(LayoutDeviceIntRect& aRect, int aScale) {
+  if (aRect.x & 0x1) {
+    aRect.width += 1;
+  }
+  aRect.x = aRect.x / aScale;
+
+  if (aRect.y & 0x1) {
+    aRect.height += 1;
+  }
+  aRect.y = aRect.y / aScale;
+
+  aRect.width = (aRect.width & 0x1) ? aRect.width / aScale + 1 :
+                                      aRect.width / aScale;
+  aRect.height = (aRect.height & 0x1) ? aRect.height / aScale + 1 :
+                                        aRect.height / aScale;
+}
+
 void WindowSurfaceWayland::CommitWaylandBuffer() {
   MOZ_ASSERT(mPendingCommit, "Committing empty surface!");
 
   if (mWaitToFullScreenUpdate) {
     return;
   }
 
   wl_surface* waylandSurface = mWindow->GetWaylandSurface();
@@ -679,21 +696,23 @@ void WindowSurfaceWayland::CommitWayland
     LayoutDeviceIntRect rect = mWindow->GetBounds();
     wl_surface_damage(waylandSurface, 0, 0, rect.width, rect.height);
     mWaylandBufferFullScreenDamage = false;
     mNeedScaleFactorUpdate = true;
   } else {
     gint scaleFactor = mWindow->GdkScaleFactor();
     for (auto iter = mWaylandBufferDamage.RectIter(); !iter.Done();
          iter.Next()) {
-      const mozilla::LayoutDeviceIntRect& r = iter.Get();
+      mozilla::LayoutDeviceIntRect r = iter.Get();
       // We need to remove the scale factor because the wl_surface_damage
       // also multiplies by current  scale factor.
-      wl_surface_damage(waylandSurface, r.x / scaleFactor, r.y / scaleFactor,
-                        r.width / scaleFactor, r.height / scaleFactor);
+      if (scaleFactor > 1) {
+        CalcRectScale(r, scaleFactor);
+      }
+      wl_surface_damage(waylandSurface, r.x, r.y, r.width, r.height);
     }
   }
 
   // Clear all back buffer damage as we're committing
   // all requested regions.
   mWaylandBufferDamage.SetEmpty();
 
   mFrameCallback = wl_surface_frame(waylandSurface);
diff --git a/widget/gtk/WindowSurfaceWayland.h b/widget/gtk/WindowSurfaceWayland.h
--- a/widget/gtk/WindowSurfaceWayland.h
+++ b/widget/gtk/WindowSurfaceWayland.h
@@ -96,16 +96,17 @@ class WindowSurfaceWayland : public Wind
   WindowBackBuffer* GetWaylandBufferToDraw(int aWidth, int aHeight);
 
   already_AddRefed<gfx::DrawTarget> LockWaylandBuffer(int aWidth, int aHeight,
                                                       bool aClearBuffer);
   already_AddRefed<gfx::DrawTarget> LockImageSurface(
       const gfx::IntSize& aLockSize);
   bool CommitImageSurfaceToWaylandBuffer(const LayoutDeviceIntRegion& aRegion);
   void CommitWaylandBuffer();
+  void CalcRectScale(LayoutDeviceIntRect& aRect, int scale);
 
   // TODO: Do we need to hold a reference to nsWindow object?
   nsWindow* mWindow;
   nsWaylandDisplay* mWaylandDisplay;
   WindowBackBuffer* mWaylandBuffer;
   LayoutDeviceIntRegion mWaylandBufferDamage;
   WindowBackBuffer* mBackupBuffer[BACK_BUFFER_NUM];
   RefPtr<gfxImageSurface> mImageSurface;