[gtk/for-master: 1/3] transform: Treat 0 perspective transforms as identity

[Benjamin Otte <otte src gnome org>]

commit 69629ebb1a3d33376aaa3bfcf6fcd385ffa6377b
Author: Benjamin Otte <otte redhat com>
Date:   Sun Jun 2 15:06:50 2019 +0200

    transform: Treat 0 perspective transforms as identity
    
    This happens if you apply a perspective transform and its inverse, which
    is the negative version of the perspective.

 gsk/gsktransform.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gsk/gsktransform.c b/gsk/gsktransform.c
index ac81fe055b..3baf8bb061 100644
--- a/gsk/gsktransform.c
+++ b/gsk/gsktransform.c
@@ -1118,7 +1118,7 @@ gsk_perspective_transform_to_matrix (GskTransform      *transform,
   GskPerspectiveTransform *self = (GskPerspectiveTransform *) transform;
   float f[16] = { 1.f, 0.f, 0.f,  0.f,
                   0.f, 1.f, 0.f,  0.f,
-                  0.f, 0.f, 1.f, -1.f / self->depth,
+                  0.f, 0.f, 1.f, self->depth ? -1.f / self->depth : 0.f,
                   0.f, 0.f, 0.f,  1.f };
 
   graphene_matrix_init_from_float (out_matrix, f);