Bug 863889. nsWindow::Move should compare the same type of pixels when determining if we are moving the window at all. r=jfkthame

widget/windows/nsWindow.cpp

@@ -1299,6 +1299,13 @@ NS_METHOD nsWindow::Move(double aX, double aY)
       mWindowType == eWindowType_dialog) {
     SetSizeMode(nsSizeMode_Normal);
   }
+
+  // for top-level windows only, convert coordinates from global display pixels
+  // (the "parent" coordinate space) to the window's device pixel space
+  double scale = BoundsUseDisplayPixels() ? GetDefaultScale() : 1.0;
+  int32_t x = NSToIntRound(aX * scale);
+  int32_t y = NSToIntRound(aY * scale);
+
   // Check to see if window needs to be moved first
   // to avoid a costly call to SetWindowPos. This check
   // can not be moved to the calling code in nsView, because
@@ -1307,18 +1314,12 @@ NS_METHOD nsWindow::Move(double aX, double aY)
   // Only perform this check for non-popup windows, since the positioning can
   // in fact change even when the x/y do not.  We always need to perform the
   // check. See bug #97805 for details.
-  if (mWindowType != eWindowType_popup && (mBounds.x == aX) && (mBounds.y == aY))
+  if (mWindowType != eWindowType_popup && (mBounds.x == x) && (mBounds.y == y))
   {
     // Nothing to do, since it is already positioned correctly.
     return NS_OK;
   }
 
-  // for top-level windows only, convert coordinates from global display pixels
-  // (the "parent" coordinate space) to the window's device pixel space
-  double scale = BoundsUseDisplayPixels() ? GetDefaultScale() : 1.0;
-  int32_t x = NSToIntRound(aX * scale);
-  int32_t y = NSToIntRound(aY * scale);
-
   mBounds.x = x;
   mBounds.y = y;