[mutter] clutter/paint-volume: Union paint volumes correctly using Graphene

[Marge Bot <marge-bot src gnome org>]

commit cc912614c78b042b3a704effcb0060d405217dc0
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Thu Apr 15 12:14:04 2021 +0200

    clutter/paint-volume: Union paint volumes correctly using Graphene
    
    Since commit d2f8a30625e we use Graphene to union paint volumes, it
    turns out a quite severe issue snuck in during review of that MR though:
    Unioned paint volumes (so paint volumes of any actors with children) now
    have negative heights. Once projected to 2d coordinates they luckily are
    correct again, which is why everything is still working.
    
    The problem is that obvious once looking closer: For the y coordinates
    of the unioned paint volume we confused the maximum and the minimum
    points and simply used the wrong coordinates to create the unioned paint
    volume.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1827>

 clutter/clutter/clutter-paint-volume.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/clutter/clutter/clutter-paint-volume.c b/clutter/clutter/clutter-paint-volume.c
index c18e661659..e30d804c07 100644
--- a/clutter/clutter/clutter-paint-volume.c
+++ b/clutter/clutter/clutter-paint-volume.c
@@ -585,10 +585,10 @@ clutter_paint_volume_union (ClutterPaintVolume *pv,
 
   graphene_box_get_min (&union_box, &min);
   graphene_box_get_max (&union_box, &max);
-  graphene_point3d_init (&pv->vertices[0], min.x, max.y, min.z);
-  graphene_point3d_init (&pv->vertices[1], max.x, max.y, min.z);
-  graphene_point3d_init (&pv->vertices[3], min.x, min.y, min.z);
-  graphene_point3d_init (&pv->vertices[4], min.x, max.y, max.z);
+  graphene_point3d_init (&pv->vertices[0], min.x, min.y, min.z);
+  graphene_point3d_init (&pv->vertices[1], max.x, min.y, min.z);
+  graphene_point3d_init (&pv->vertices[3], min.x, max.y, min.z);
+  graphene_point3d_init (&pv->vertices[4], min.x, min.y, max.z);
 
   if (pv->vertices[4].z == pv->vertices[0].z)
     pv->is_2d = TRUE;