[cairo] [PATCH] gl: Do operator conversion and judgement in beginning of composite_boxes.

[Chuanbo Weng]

The main purpose is to convert CLEAR to DEST_OUT when there's a mask.
This fix zero-mask case in cairo-test-suite.
---
 src/cairo-gl-spans-compositor.c |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/src/cairo-gl-spans-compositor.c b/src/cairo-gl-spans-compositor.c
index 0c2134f..e1fc966 100644
--- a/src/cairo-gl-spans-compositor.c
+++ b/src/cairo-gl-spans-compositor.c
@@ -362,6 +362,25 @@ composite_boxes (void			*_dst,
 
     TRACE ((stderr, "%s mask=(%d,%d), dst=(%d, %d)\n", __FUNCTION__,
 	    mask_x, mask_y, dst_x, dst_y));
+
+    if (((cairo_surface_t *)_dst)->is_clear &&
+        (op == CAIRO_OPERATOR_SOURCE ||
+         op == CAIRO_OPERATOR_OVER ||
+         op == CAIRO_OPERATOR_ADD)) {
+        op = CAIRO_OPERATOR_SOURCE;
+    } else if (abstract_mask) {
+        if (op == CAIRO_OPERATOR_CLEAR) {
+            _cairo_gl_solid_operand_init (source_to_operand (abstract_src), CAIRO_COLOR_WHITE);
+            op = CAIRO_OPERATOR_DEST_OUT;
+        } else if (op == CAIRO_OPERATOR_SOURCE) {
+            return CAIRO_INT_STATUS_UNSUPPORTED;
+        } else if(! _cairo_gl_operator_is_supported (op)){
+            return CAIRO_INT_STATUS_UNSUPPORTED;
+        }        
+    } else if (! _cairo_gl_operator_is_supported (op)){
+            return CAIRO_INT_STATUS_UNSUPPORTED;
+    }
+
     status = _cairo_gl_composite_init (&setup, op, _dst, FALSE);
     if (unlikely (status))
         goto FAIL;
-- 
1.7.5.4