API: add gdk_cairo_get_clip_rectangle() convenience API

1 files changed, 39 insertions, 0 deletions

diff --git a/gdk/gdkcairo.c b/gdk/gdkcairo.c
index 7a7fc839cf..3ef1ce2b34 100644
--- a/gdk/gdkcairo.c
+++ b/gdk/gdkcairo.c
@@ -90,6 +90,45 @@ gdk_cairo_reset_clip (cairo_t            *cr,
 }
 
 /**
+ * gdk_cairo_get_clip_rectangle:
+ * @cr: a cairo context
+ * @rect: (out) (allow-none): return location for the clip, or %NULL
+ *
+ * This is a convenience function around cairo_clip_extents(). It rounds
+ * the clip extents to integer coordinates and returns a boolean
+ * indicating if a clip area exists.
+ *
+ * Returns: %TRUE if a clip rectangle exists, %FALSE if all of @cr is
+ * clipped and all drawing can be skipped.
+ **/
+gboolean
+gdk_cairo_get_clip_rectangle (cairo_t      *cr,
+                              GdkRectangle *rect)
+{
+  double x1, y1, x2, y2;
+  gboolean clip_exists;
+
+  cairo_clip_extents (cr, &x1, &y1, &x2, &y2);
+
+  clip_exists = x1 < x2 && y1 < y2;
+
+  if (rect)
+    {
+      x1 = floor (x1);
+      y1 = floor (y1);
+      x2 = ceil (x2);
+      y2 = ceil (y2);
+
+      rect->x      = CLAMP (x1,      G_MININT, G_MAXINT);
+      rect->y      = CLAMP (y1,      G_MININT, G_MAXINT);
+      rect->width  = CLAMP (x2 - x1, G_MININT, G_MAXINT);
+      rect->height = CLAMP (y2 - y1, G_MININT, G_MAXINT);
+    }
+
+  return clip_exists;
+}
+
+/**
  * gdk_cairo_set_source_color:
  * @cr: a #cairo_t
  * @color: a #GdkColor