traps-as-spans

Add an interface to spans that accepts trapezoids. This allows backends
that have an efficient span-line interface but lack efficient handling
of boxes (partly due to the current poor compositor interface) to
redirect composite_trapezoids() to composite_polygon() and the
span-renderer.

3 files changed, 127 insertions, 1 deletions

diff --git a/src/cairo-spans-private.h b/src/cairo-spans-private.h
index 9f6f1169..e29a567a 100644
--- a/src/cairo-spans-private.h
+++ b/src/cairo-spans-private.h
@@ -75,6 +75,13 @@ struct _cairo_scan_converter {
     /* Destroy this scan converter. */
     cairo_destroy_func_t	destroy;
 
+    /* Add a single edge to the converter. */
+    cairo_status_t (*add_edge) (void		    *abstract_converter,
+				const cairo_point_t *p1,
+				const cairo_point_t *p2,
+				int top, int bottom,
+				int dir);
+
     /* Add a polygon (set of edges) to the converter. */
     cairo_status_t (*add_polygon) (void		    *abstract_converter,
 				   const cairo_polygon_t  *polygon);
@@ -133,4 +140,16 @@ _cairo_surface_composite_polygon (cairo_surface_t	*surface,
 				  cairo_polygon_t	*polygon,
 				  cairo_region_t	*clip_region);
 
+cairo_private cairo_status_t
+_cairo_surface_composite_trapezoids_as_polygon (cairo_surface_t	*surface,
+						cairo_operator_t	 op,
+						const cairo_pattern_t	*pattern,
+						cairo_antialias_t	antialias,
+						int src_x, int src_y,
+						int dst_x, int dst_y,
+						int width, int height,
+						cairo_trapezoid_t	*traps,
+						int num_traps,
+						cairo_region_t	*clip_region);
+
 #endif /* CAIRO_SPANS_PRIVATE_H */
diff --git a/src/cairo-spans.c b/src/cairo-spans.c
index 369cd582..1a516347 100644
--- a/src/cairo-spans.c
+++ b/src/cairo-spans.c
@@ -83,6 +83,71 @@ _cairo_surface_composite_polygon (cairo_surface_t	*surface,
     return status;
 }
 
+cairo_status_t
+_cairo_surface_composite_trapezoids_as_polygon (cairo_surface_t	*surface,
+						cairo_operator_t	 op,
+						const cairo_pattern_t	*pattern,
+						cairo_antialias_t	antialias,
+						int src_x, int src_y,
+						int dst_x, int dst_y,
+						int width, int height,
+						cairo_trapezoid_t	*traps,
+						int num_traps,
+						cairo_region_t	*clip_region)
+{
+    cairo_span_renderer_t *renderer;
+    cairo_scan_converter_t *converter;
+    cairo_composite_rectangles_t rects;
+    cairo_status_t status;
+
+    rects.src.x = src_x;
+    rects.src.y = src_y;
+    rects.dst.x = 0;
+    rects.dst.y = 0;
+    rects.mask.x = dst_x;
+    rects.mask.y = dst_y;
+    rects.width  = width;
+    rects.height = height;
+
+    converter = _create_scan_converter (CAIRO_FILL_RULE_WINDING,
+					antialias,
+					&rects);
+    status = converter->status;
+    if (unlikely (status))
+	goto CLEANUP_CONVERTER;
+
+    while (num_traps--) {
+	status = converter->add_edge (converter,
+				      &traps->left.p1, &traps->left.p2,
+				      traps->top, traps->bottom, 1);
+	if (unlikely (status))
+	    goto CLEANUP_CONVERTER;
+
+	status = converter->add_edge (converter,
+				      &traps->right.p1, &traps->right.p2,
+				      traps->top, traps->bottom, -1);
+	if (unlikely (status))
+	    goto CLEANUP_CONVERTER;
+
+	traps++;
+    }
+
+    renderer = _cairo_surface_create_span_renderer (op, pattern, surface,
+						    antialias, &rects,
+						    clip_region);
+    status = converter->generate (converter, renderer);
+    if (unlikely (status))
+	goto CLEANUP_RENDERER;
+
+    status = renderer->finish (renderer);
+
+ CLEANUP_RENDERER:
+    renderer->destroy (renderer);
+ CLEANUP_CONVERTER:
+    converter->destroy (converter);
+    return status;
+}
+
 static void
 _cairo_nil_destroy (void *abstract)
 {
@@ -99,6 +164,22 @@ _cairo_nil_scan_converter_add_polygon (void *abstract_converter,
 }
 
 static cairo_status_t
+_cairo_nil_scan_converter_add_edge (void *abstract_converter,
+				    const cairo_point_t *p1,
+				    const cairo_point_t *p2,
+				    int top, int bottom,
+				    int dir)
+{
+    (void) abstract_converter;
+    (void) p1;
+    (void) p2;
+    (void) top;
+    (void) bottom;
+    (void) dir;
+    return _cairo_scan_converter_status (abstract_converter);
+}
+
+static cairo_status_t
 _cairo_nil_scan_converter_generate (void *abstract_converter,
 				    cairo_span_renderer_t *renderer)
 {
@@ -123,6 +204,7 @@ _cairo_scan_converter_set_error (void *abstract_converter,
 	ASSERT_NOT_REACHED;
     if (converter->status == CAIRO_STATUS_SUCCESS) {
 	converter->add_polygon = _cairo_nil_scan_converter_add_polygon;
+	converter->add_edge = _cairo_nil_scan_converter_add_edge;
 	converter->generate = _cairo_nil_scan_converter_generate;
 	converter->status = error;
     }
diff --git a/src/cairo-tor-scan-converter.c b/src/cairo-tor-scan-converter.c
index 75cda4fe..29262c2d 100644
--- a/src/cairo-tor-scan-converter.c
+++ b/src/cairo-tor-scan-converter.c
@@ -1685,7 +1685,7 @@ glitter_scan_converter_add_edge (glitter_scan_converter_t *converter,
 
     INPUT_TO_GRID_Y (edge->top, e.top);
     INPUT_TO_GRID_Y (edge->bottom, e.bottom);
-    if (e.top == e.bottom)
+    if (e.top >= e.bottom)
 	return GLITTER_STATUS_SUCCESS;
 
     /* XXX: possible overflows if GRID_X/Y > 2**GLITTER_INPUT_BITS */
@@ -1915,6 +1915,30 @@ _cairo_tor_scan_converter_destroy (void *converter)
 }
 
 static cairo_status_t
+_cairo_tor_scan_converter_add_edge (void		*converter,
+				    const cairo_point_t *p1,
+				    const cairo_point_t *p2,
+				    int top, int bottom,
+				    int dir)
+{
+    cairo_tor_scan_converter_t *self = converter;
+    cairo_status_t status;
+    cairo_edge_t edge;
+
+    edge.line.p1 = *p1;
+    edge.line.p2 = *p2;
+    edge.top = top;
+    edge.bottom = bottom;
+    edge.dir = dir;
+
+    status = glitter_scan_converter_add_edge (self->converter, &edge);
+    if (unlikely (status))
+	return _cairo_scan_converter_set_error (self, _cairo_error (status));
+
+    return CAIRO_STATUS_SUCCESS;
+}
+
+static cairo_status_t
 _cairo_tor_scan_converter_add_polygon (void		*converter,
 				       const cairo_polygon_t *polygon)
 {
@@ -1968,6 +1992,7 @@ _cairo_tor_scan_converter_create (int			xmin,
     }
 
     self->base.destroy = _cairo_tor_scan_converter_destroy;
+    self->base.add_edge = _cairo_tor_scan_converter_add_edge;
     self->base.add_polygon = _cairo_tor_scan_converter_add_polygon;
     self->base.generate = _cairo_tor_scan_converter_generate;