[gtk/wip/baedert/transforms6] widget: Only push a transform if we need to

[Timm Bäder <baedert src gnome org>]

commit e403d399d7a6de606ff11951b471e7d0ab830b84
Author: Timm Bäder <mail baedert org>
Date:   Thu Nov 29 09:49:16 2018 +0100

    widget: Only push a transform if we need to

 gtk/gtkwidget.c        | 15 ++++++++++++---
 gtk/gtkwidgetprivate.h |  1 +
 2 files changed, 13 insertions(+), 3 deletions(-)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 609b549fd0..817f6ea632 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -2888,6 +2888,7 @@ gtk_widget_init (GTypeInstance *instance, gpointer g_class)
     }
 
   graphene_matrix_init_identity (&priv->transform);
+  priv->has_transform = FALSE;
 
   /* this will be set to TRUE if the widget gets a child or if the
    * expand flag is set on the widget, but until one of those happen
@@ -4299,6 +4300,7 @@ gtk_widget_size_allocate_transformed (GtkWidget               *widget,
   priv->allocated_offset_y = allocated_offset_y;
   priv->allocated_baseline = baseline;
   priv->transform = final_transform;
+  priv->has_transform = !graphene_matrix_is_identity (&final_transform);
 
   if (!alloc_needed && !size_changed && !baseline_changed)
     {
@@ -13542,9 +13544,13 @@ gtk_widget_snapshot_child (GtkWidget   *widget,
   g_return_if_fail (_gtk_widget_get_parent (child) == widget);
   g_return_if_fail (snapshot != NULL);
 
-  gtk_snapshot_push_transform (snapshot, &priv->transform);
+  if (priv->has_transform)
+    gtk_snapshot_push_transform (snapshot, &priv->transform);
+
   gtk_widget_snapshot (child, snapshot);
-  gtk_snapshot_pop (snapshot);
+
+  if (priv->has_transform)
+    gtk_snapshot_pop (snapshot);
 }
 
 /**
@@ -13784,7 +13790,10 @@ gtk_widget_set_transform (GtkWidget               *widget,
 {
   GtkWidgetPrivate *priv = gtk_widget_get_instance_private (widget);
 
-  graphene_matrix_init_from_matrix (&priv->transform, transform);
+  priv->has_transform = !graphene_matrix_is_identity (transform);
+
+  if (priv->has_transform)
+    graphene_matrix_init_from_matrix (&priv->transform, transform);
 }
 
 void
diff --git a/gtk/gtkwidgetprivate.h b/gtk/gtkwidgetprivate.h
index 847c66672a..43c1eebb46 100644
--- a/gtk/gtkwidgetprivate.h
+++ b/gtk/gtkwidgetprivate.h
@@ -151,6 +151,7 @@ struct _GtkWidgetPrivate
   int allocated_offset_x;
   int allocated_offset_y;
   graphene_matrix_t transform;
+  guint has_transform : 1;
 
   /* The widget's requested sizes */
   SizeRequestCache requests;