observer: further classify general clips

A clip with only a single path or can be reduced to a single polygon are
easier to handle than a clip containing a mixture of paths (typically
ANTIALIAS_NONE vs ANTIALIAS_DEFAULT).

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 17 insertions, 0 deletions

diff --git a/src/cairo-clip-polygon.c b/src/cairo-clip-polygon.c
index 19da15dc5..0e1968d05 100644
--- a/src/cairo-clip-polygon.c
+++ b/src/cairo-clip-polygon.c
@@ -125,3 +125,20 @@ _cairo_clip_get_polygon (const cairo_clip_t *clip,
 
     return CAIRO_STATUS_SUCCESS;
 }
+
+cairo_bool_t
+_cairo_clip_is_polygon (const cairo_clip_t *clip)
+{
+    if (_cairo_clip_is_all_clipped (clip))
+	return TRUE;
+
+    /* If there is no clip, we need an infinite polygon */
+    if (clip == NULL)
+	return FALSE;
+
+    if (clip->path == NULL)
+	return TRUE;
+
+    /* check that residual is all of the same type/tolerance */
+    return can_convert_to_polygon (clip);
+}