[gtk/wip/otte/canvas: 35/36] canvas: scale(-1) the widgets when allocation size is negative

[Benjamin Otte <otte src gnome org>]

commit 67cd4052e9586397ece5860d3057506dccb1b7ac
Author: Benjamin Otte <otte redhat com>
Date:   Tue Jul 5 07:30:51 2022 +0200

    canvas: scale(-1) the widgets when allocation size is negative
    
    Just flip the widgets, because hey, that makes planarity work!

 gtk/gtkcanvasitem.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)
---
diff --git a/gtk/gtkcanvasitem.c b/gtk/gtkcanvasitem.c
index 0ed91e7291..1d8484db45 100644
--- a/gtk/gtkcanvasitem.c
+++ b/gtk/gtkcanvasitem.c
@@ -308,6 +308,7 @@ gtk_canvas_item_allocate_widget (GtkCanvasItem *self,
                                  float          dy)
 {
   graphene_rect_t allocation;
+  GskTransform *transform;
 
   if (self->widget == NULL)
     return;
@@ -318,14 +319,14 @@ gtk_canvas_item_allocate_widget (GtkCanvasItem *self,
       g_assert_not_reached ();
     }
 
-  graphene_rect_normalize (&allocation);
-  gtk_widget_size_allocate (self->widget,
-                            &(GtkAllocation) {
-                              allocation.origin.x - dx,
-                              allocation.origin.y - dy,
-                              allocation.size.width,
-                              allocation.size.height
-                            }, -1);
+  transform = gsk_transform_translate (NULL, &allocation.origin);
+  transform = gsk_transform_scale (transform, signbit (allocation.size.width) ? -1 : 1, signbit 
(allocation.size.height) ? -1 : 1);
+
+  gtk_widget_allocate (self->widget,
+                       ABS (allocation.size.width),
+                       ABS (allocation.size.height),
+                       -1,
+                       transform);
 }
 
 gboolean