fill: Convert rectilinear paths to boxes.

A quick and efficient method for extracting the set of boxes that
represent the path when filled.

src/cairo-path-fill.c

@@ -35,6 +35,7 @@
  */
 
 #include "cairoint.h"
+#include "cairo-boxes-private.h"
 #include "cairo-error-private.h"
 #include "cairo-path-fixed-private.h"
 #include "cairo-region-private.h"
@@ -142,7 +143,8 @@ _cairo_path_fixed_fill_to_traps (const cairo_path_fixed_t *path,
 	return CAIRO_STATUS_SUCCESS;
 
     _cairo_polygon_init (&polygon);
-    _cairo_polygon_limit (&polygon, traps->limits, traps->num_limits);
+    if (traps->num_limits)
+	_cairo_polygon_limit (&polygon, traps->limits, traps->num_limits);
 
     status = _cairo_path_fixed_fill_to_polygon (path,
 						tolerance,
@@ -392,3 +394,75 @@ _cairo_path_fixed_fill_rectilinear_to_traps (const cairo_path_fixed_t *path,
 	return CAIRO_INT_STATUS_UNSUPPORTED;
     }
 }
+
+static cairo_status_t
+_cairo_path_fixed_fill_rectilinear_tessellate_to_boxes (const cairo_path_fixed_t *path,
+							cairo_fill_rule_t fill_rule,
+							cairo_boxes_t *boxes)
+{
+    cairo_polygon_t polygon;
+    cairo_status_t status;
+
+    _cairo_polygon_init (&polygon);
+    if (boxes->num_limits) {
+	_cairo_polygon_limit (&polygon, boxes->limits, boxes->num_limits);
+	boxes->num_limits = 0;
+    }
+
+    /* tolerance will be ignored as the path is rectilinear */
+    status = _cairo_path_fixed_fill_to_polygon (path, 0., &polygon);
+    if (likely (status == CAIRO_STATUS_SUCCESS)) {
+	status =
+	    _cairo_bentley_ottmann_tessellate_rectilinear_polygon_to_boxes (&polygon,
+									    fill_rule,
+									    boxes);
+    }
+
+    _cairo_polygon_fini (&polygon);
+
+    return status;
+}
+
+cairo_status_t
+_cairo_path_fixed_fill_rectilinear_to_boxes (const cairo_path_fixed_t *path,
+					     cairo_fill_rule_t fill_rule,
+					     cairo_boxes_t *boxes)
+{
+    cairo_path_fixed_iter_t iter;
+    cairo_status_t status;
+    cairo_box_t box;
+
+    if (_cairo_path_fixed_is_box (path, &box))
+	return _cairo_boxes_add (boxes, &box);
+
+    _cairo_path_fixed_iter_init (&iter, path);
+    while (_cairo_path_fixed_iter_is_fill_box (&iter, &box)) {
+	if (box.p1.y == box.p2.y || box.p1.x == box.p2.x)
+	    continue;
+
+	if (box.p1.y > box.p2.y) {
+	    cairo_fixed_t t;
+
+	    t = box.p1.y;
+	    box.p1.y = box.p2.y;
+	    box.p2.y = t;
+
+	    t = box.p1.x;
+	    box.p1.x = box.p2.x;
+	    box.p2.x = t;
+	}
+
+	status = _cairo_boxes_add (boxes, &box);
+	if (unlikely (status))
+	    return status;
+    }
+
+    if (_cairo_path_fixed_iter_at_end (&iter))
+	return _cairo_bentley_ottmann_tessellate_boxes (boxes, fill_rule, boxes);
+
+    /* path is not rectangular, try extracting clipped rectilinear edges */
+    _cairo_boxes_clear (boxes);
+    return _cairo_path_fixed_fill_rectilinear_tessellate_to_boxes (path,
+								   fill_rule,
+								   boxes);
+}

src/cairoint.h

@@ -1561,6 +1561,11 @@ _cairo_path_fixed_fill_rectilinear_to_traps (const cairo_path_fixed_t *path,
 					     cairo_fill_rule_t fill_rule,
 					     cairo_traps_t *traps);
 
+cairo_private cairo_status_t
+_cairo_path_fixed_fill_rectilinear_to_boxes (const cairo_path_fixed_t *path,
+					     cairo_fill_rule_t fill_rule,
+					     cairo_boxes_t *boxes);
+
 cairo_private cairo_region_t *
 _cairo_path_fixed_fill_rectilinear_to_region (const cairo_path_fixed_t	*path,
 					      cairo_fill_rule_t	 fill_rule,