[gtk/wip/baedert/transforms6] widget: Apply CSS transform in size_allocate_transformed

[Timm Bäder <baedert src gnome org>]

commit a36860e9234d697499af8fb40adb854d90886398
Author: Timm Bäder <mail baedert org>
Date:   Sat Jan 19 09:01:02 2019 +0100

    widget: Apply CSS transform in size_allocate_transformed

 gtk/gtkwidget.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 21974053bb..cee22a65d1 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -35,6 +35,7 @@
 #include "gtkbuilderprivate.h"
 #include "gtkcontainerprivate.h"
 #include "gtkcssfiltervalueprivate.h"
+#include "gtkcsstransformvalueprivate.h"
 #include "gtkcssfontvariationsvalueprivate.h"
 #include "gtkcssnumbervalueprivate.h"
 #include "gtkcssshadowsvalueprivate.h"
@@ -4295,6 +4296,32 @@ gtk_widget_size_allocate_transformed (GtkWidget               *widget,
       real_allocation.height = MAX (1, real_allocation.height);
     }
 
+  /* Apply CSS transformation */
+  {
+    graphene_matrix_t css_transform;
+    GtkCssValue *transform_value = _gtk_style_context_peek_property (_gtk_widget_get_style_context (widget),
+                                                                     GTK_CSS_PROPERTY_TRANSFORM);
+
+
+    if (!gtk_css_transform_value_is_none (transform_value) &&
+        gtk_css_transform_value_get_matrix (transform_value, &css_transform))
+      {
+        graphene_matrix_translate (&final_transform,
+                                   &(graphene_point3d_t) {
+                                    - real_allocation.width / 2.0f,
+                                    - real_allocation.height / 2.0f,
+                                    0
+                                   });
+        graphene_matrix_multiply (&final_transform, &css_transform, &final_transform);
+        graphene_matrix_translate (&final_transform,
+                                   &(graphene_point3d_t) {
+                                    real_allocation.width / 2.0f,
+                                    real_allocation.height / 2.0f,
+                                    0
+                                   });
+      }
+  }
+
   baseline_changed = priv->allocated_baseline != baseline;
   size_changed = (priv->allocation.width != real_allocation.width ||
                   priv->allocation.height != real_allocation.height);