gstate: Set an error status when restoring a push_group

cairo_push_group (cr) followed by cairo_restore (cr) should put cr in
an error status of CAIRO_STATUS_INVALID_RESTORE.

Fixes group-state.

1 files changed, 16 insertions, 0 deletions

diff --git a/src/cairo-gstate.c b/src/cairo-gstate.c
index efb826703..52d568c12 100644
--- a/src/cairo-gstate.c
+++ b/src/cairo-gstate.c
@@ -342,6 +342,22 @@ _cairo_gstate_redirect_target (cairo_gstate_t *gstate, cairo_surface_t *child)
 }
 
 /**
+ * _cairo_gstate_is_group
+ * @gstate: a #cairo_gstate_t
+ *
+ * Check if _cairo_gstate_redirect_target has been called on the head
+ * of the stack.
+ *
+ * Return value: %TRUE if @gstate is redirected to a target different
+ * than the previous state in the stack, %FALSE otherwise.
+ **/
+cairo_bool_t
+_cairo_gstate_is_group (cairo_gstate_t *gstate)
+{
+    return gstate->parent_target != NULL;
+}
+
+/**
  * _cairo_gstate_is_redirected
  * @gstate: a #cairo_gstate_t
  *