[mutter] boxes: Ensure we scale to a fully rounded rectangle

[Jonas Ådahl <jadahl src gnome org>]

commit 68fba458b33d423f45be936fd99b9f100c379c1f
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Fri Mar 1 20:47:07 2019 +0100

    boxes: Ensure we scale to a fully rounded rectangle
    
    In order to scale a rectangle by a double value, we can reuse a ClutterRect
    to do the scale computations in floating point math and then to convert it back
    using the proper strategy that will take in account the subpixel compensation.
    
    In this way we can be sure that the resulting rectangle can fully contain the
    original scaled one.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/469

 src/core/boxes.c | 24 +++++-------------------
 1 file changed, 5 insertions(+), 19 deletions(-)
---
diff --git a/src/core/boxes.c b/src/core/boxes.c
index 400febea1..0e9affec4 100644
--- a/src/core/boxes.c
+++ b/src/core/boxes.c
@@ -2051,25 +2051,11 @@ meta_rectangle_scale_double (const MetaRectangle  *rect,
                              MetaRoundingStrategy  rounding_strategy,
                              MetaRectangle        *dest)
 {
-  switch (rounding_strategy)
-    {
-    case META_ROUNDING_STRATEGY_SHRINK:
-      *dest = (MetaRectangle) {
-        .x = (int) ceil (rect->x * scale),
-        .y = (int) ceil (rect->y * scale),
-        .width = (int) floor (rect->width * scale),
-        .height = (int) floor (rect->height * scale),
-      };
-      break;
-    case META_ROUNDING_STRATEGY_GROW:
-      *dest = (MetaRectangle) {
-        .x = (int) floor (rect->x * scale),
-        .y = (int) floor (rect->y * scale),
-        .width = (int) ceil (rect->width * scale),
-        .height = (int) ceil (rect->height * scale),
-      };
-      break;
-    }
+  ClutterRect tmp = CLUTTER_RECT_INIT (rect->x, rect->y,
+                                       rect->width, rect->height);
+
+  clutter_rect_scale (&tmp, scale, scale);
+  meta_rectangle_from_clutter_rect (&tmp, rounding_strategy, dest);
 }
 
 void