Introduce a new compositor architecture

Having spent the last dev cycle looking at how we could specialize the
compositors for various backends, we once again look for the
commonalities in order to reduce the duplication. In part this is
motivated by the idea that spans is a good interface for both the
existent GL backend and pixman, and so they deserve a dedicated
compositor. xcb/xlib target an identical rendering system and so they
should be using the same compositor, and it should be possible to run
that same compositor locally against pixman to generate reference tests.

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

P.S. This brings massive upheaval (read breakage) I've tried delaying in
order to fix as many things as possible but now this one patch does far,
far, far too much. Apologies in advance for breaking your favourite
backend, but trust me in that the end result will be much better. :)

1 files changed, 1007 insertions, 0 deletions

diff --git a/src/cairo-spans-compositor.c b/src/cairo-spans-compositor.c
new file mode 100644
index 000000000..4320a3ecc
--- /dev/null
+++ b/src/cairo-spans-compositor.c
@@ -0,0 +1,1007 @@
+/* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */
+/* cairo - a vector graphics library with display and print output
+ *
+ * Copyright © 2002 University of Southern California
+ * Copyright © 2005 Red Hat, Inc.
+ * Copyright © 2011 Intel Corporation
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it either under the terms of the GNU Lesser General Public
+ * License version 2.1 as published by the Free Software Foundation
+ * (the "LGPL") or, at your option, under the terms of the Mozilla
+ * Public License Version 1.1 (the "MPL"). If you do not alter this
+ * notice, a recipient may use your version of this file under either
+ * the MPL or the LGPL.
+ *
+ * You should have received a copy of the LGPL along with this library
+ * in the file COPYING-LGPL-2.1; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
+ * You should have received a copy of the MPL along with this library
+ * in the file COPYING-MPL-1.1
+ *
+ * The contents of this file are subject to the Mozilla Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
+ * OF ANY KIND, either express or implied. See the LGPL or the MPL for
+ * the specific language governing rights and limitations.
+ *
+ * The Original Code is the cairo graphics library.
+ *
+ * The Initial Developer of the Original Code is University of Southern
+ * California.
+ *
+ * Contributor(s):
+ *	Carl D. Worth <cworth@cworth.org>
+ *      Joonas Pihlaja <jpihlaja@cc.helsinki.fi>
+ *	Chris Wilson <chris@chris-wilson.co.uk>
+ */
+
+#include "cairoint.h"
+
+#include "cairo-compositor-private.h"
+#include "cairo-clip-private.h"
+#include "cairo-image-surface-private.h"
+#include "cairo-paginated-private.h"
+#include "cairo-pattern-private.h"
+#include "cairo-region-private.h"
+#include "cairo-recording-surface-private.h"
+#include "cairo-spans-compositor-private.h"
+#include "cairo-surface-subsurface-private.h"
+#include "cairo-surface-snapshot-private.h"
+#include "cairo-surface-observer-private.h"
+
+typedef struct {
+    cairo_polygon_t	*polygon;
+    cairo_fill_rule_t	 fill_rule;
+    cairo_antialias_t	 antialias;
+} composite_spans_info_t;
+
+static cairo_int_status_t
+composite_polygon (const cairo_spans_compositor_t	*compositor,
+		   cairo_composite_rectangles_t		 *extents,
+		   cairo_polygon_t			*polygon,
+		   cairo_fill_rule_t			 fill_rule,
+		   cairo_antialias_t			 antialias);
+
+static cairo_int_status_t
+composite_boxes (const cairo_spans_compositor_t *compositor,
+		 cairo_composite_rectangles_t *extents,
+		 cairo_boxes_t		*boxes);
+
+static cairo_int_status_t
+clip_and_composite_polygon (const cairo_spans_compositor_t	*compositor,
+			    cairo_composite_rectangles_t	 *extents,
+			    cairo_polygon_t			*polygon,
+			    cairo_fill_rule_t			 fill_rule,
+			    cairo_antialias_t			 antialias);
+static cairo_surface_t *
+get_clip_surface (const cairo_spans_compositor_t *compositor,
+		  cairo_surface_t *dst,
+		  const cairo_clip_t *clip,
+		  const cairo_rectangle_int_t *extents)
+{
+    cairo_composite_rectangles_t composite;
+    cairo_surface_t *surface;
+    cairo_box_t box;
+    cairo_polygon_t polygon;
+    const cairo_clip_path_t *clip_path;
+    cairo_antialias_t antialias;
+    cairo_fill_rule_t fill_rule;
+    cairo_int_status_t status;
+
+    assert (clip->path);
+
+    surface = _cairo_surface_create_similar_solid (dst,
+						   CAIRO_CONTENT_ALPHA,
+						   extents->width,
+						   extents->height,
+						   CAIRO_COLOR_TRANSPARENT);
+
+    _cairo_box_from_rectangle (&box, extents);
+    _cairo_polygon_init (&polygon, &box, 1);
+
+    clip_path = clip->path;
+    status = _cairo_path_fixed_fill_to_polygon (&clip_path->path,
+						clip_path->tolerance,
+						&polygon);
+    if (unlikely (status))
+	goto cleanup_polygon;
+
+    polygon.limits = NULL;
+    polygon.num_limits = 0;
+
+    antialias = clip_path->antialias;
+    fill_rule = clip_path->fill_rule;
+    clip_path = clip_path->prev;
+    while (clip_path) {
+	if (clip_path->antialias == antialias) {
+	    cairo_polygon_t next;
+
+	    _cairo_polygon_init (&next, NULL, 0);
+	    status = _cairo_path_fixed_fill_to_polygon (&clip_path->path,
+							clip_path->tolerance,
+							&next);
+	    if (likely (status == CAIRO_INT_STATUS_SUCCESS))
+		status = _cairo_polygon_intersect (&polygon, fill_rule,
+						   &next, clip_path->fill_rule);
+	    _cairo_polygon_fini (&next);
+	    if (unlikely (status))
+		goto cleanup_polygon;
+
+	    fill_rule = CAIRO_FILL_RULE_WINDING;
+	}
+
+	clip_path = clip_path->prev;
+    }
+
+    _cairo_polygon_translate (&polygon, -extents->x, -extents->y);
+    status = _cairo_composite_rectangles_init_for_polygon (&composite, surface,
+							   CAIRO_OPERATOR_ADD,
+							   &_cairo_pattern_white.base,
+							   &polygon,
+							   NULL);
+    if (unlikely (status))
+	goto cleanup_polygon;
+
+    status = composite_polygon (compositor, &composite,
+				&polygon, fill_rule, antialias);
+    _cairo_composite_rectangles_fini (&composite);
+    _cairo_polygon_fini (&polygon);
+    if (unlikely (status))
+	goto error;
+
+    _cairo_polygon_init (&polygon, &box, 1);
+
+    clip_path = clip->path;
+    antialias = clip_path->antialias == CAIRO_ANTIALIAS_DEFAULT ? CAIRO_ANTIALIAS_NONE : CAIRO_ANTIALIAS_DEFAULT;
+    clip_path = clip_path->prev;
+    while (clip_path) {
+	if (clip_path->antialias == antialias) {
+	    if (polygon.num_edges == 0) {
+		status = _cairo_path_fixed_fill_to_polygon (&clip_path->path,
+							    clip_path->tolerance,
+							    &polygon);
+
+		fill_rule = clip_path->fill_rule;
+		polygon.limits = NULL;
+		polygon.num_limits = 0;
+	    } else {
+		cairo_polygon_t next;
+
+		_cairo_polygon_init (&next, NULL, 0);
+		status = _cairo_path_fixed_fill_to_polygon (&clip_path->path,
+							    clip_path->tolerance,
+							    &next);
+		if (likely (status == CAIRO_INT_STATUS_SUCCESS))
+		    status = _cairo_polygon_intersect (&polygon, fill_rule,
+						       &next, clip_path->fill_rule);
+		_cairo_polygon_fini (&next);
+		fill_rule = CAIRO_FILL_RULE_WINDING;
+	    }
+	    if (unlikely (status))
+		goto error;
+	}
+
+	clip_path = clip_path->prev;
+    }
+
+    if (polygon.num_edges) {
+	_cairo_polygon_translate (&polygon, -extents->x, -extents->y);
+	status = _cairo_composite_rectangles_init_for_polygon (&composite, surface,
+							       CAIRO_OPERATOR_IN,
+							       &_cairo_pattern_white.base,
+							       &polygon,
+							       NULL);
+	if (unlikely (status))
+	    goto cleanup_polygon;
+
+	status = composite_polygon (compositor, &composite,
+				    &polygon, fill_rule, antialias);
+	_cairo_composite_rectangles_fini (&composite);
+	_cairo_polygon_fini (&polygon);
+	if (unlikely (status))
+	    goto error;
+    }
+
+    return surface;
+
+cleanup_polygon:
+    _cairo_polygon_fini (&polygon);
+error:
+    cairo_surface_destroy (surface);
+    return _cairo_surface_create_in_error (status);
+}
+
+static cairo_int_status_t
+fixup_unbounded_mask (const cairo_spans_compositor_t *compositor,
+		      const cairo_composite_rectangles_t *extents,
+		      cairo_boxes_t *boxes)
+{
+    cairo_composite_rectangles_t composite;
+    cairo_surface_t *clip;
+    cairo_int_status_t status;
+
+    clip = get_clip_surface (compositor, extents->surface, extents->clip,
+			     &extents->unbounded);
+    if (unlikely (clip->status))
+	return clip->status;
+
+    status = _cairo_composite_rectangles_init_for_boxes (&composite,
+							 extents->surface,
+							 CAIRO_OPERATOR_DEST_OUT,
+							 &_cairo_pattern_white.base,
+							 boxes,
+							 NULL);
+    if (unlikely (status))
+	goto cleanup_clip;
+
+    _cairo_pattern_init_for_surface (&composite.mask_pattern.surface, clip);
+    composite.mask_pattern.base.filter = CAIRO_FILTER_NEAREST;
+    composite.mask_pattern.base.extend = CAIRO_EXTEND_NONE;
+
+    status = composite_boxes (compositor, &composite, boxes);
+
+    _cairo_pattern_fini (&composite.mask_pattern.base);
+    _cairo_composite_rectangles_fini (&composite);
+
+cleanup_clip:
+    cairo_surface_destroy (clip);
+    return status;
+}
+
+static cairo_int_status_t
+fixup_unbounded_polygon (const cairo_spans_compositor_t *compositor,
+			 const cairo_composite_rectangles_t *extents,
+			 cairo_boxes_t *boxes)
+{
+    cairo_polygon_t polygon, intersect;
+    cairo_composite_rectangles_t composite;
+    cairo_fill_rule_t fill_rule;
+    cairo_antialias_t antialias;
+    cairo_int_status_t status;
+
+    /* Can we treat the clip as a regular clear-polygon and use it to fill? */
+    status = _cairo_clip_get_polygon (extents->clip, &polygon,
+				      &fill_rule, &antialias);
+    if (status == CAIRO_INT_STATUS_UNSUPPORTED)
+	return status;
+
+    status= _cairo_polygon_init_boxes (&intersect, boxes);
+    if (unlikely (status))
+	goto cleanup_polygon;
+
+    status = _cairo_polygon_intersect (&polygon, fill_rule,
+				       &intersect, CAIRO_FILL_RULE_WINDING);
+    _cairo_polygon_fini (&intersect);
+
+    if (unlikely (status))
+	goto cleanup_polygon;
+
+    status = _cairo_composite_rectangles_init_for_polygon (&composite,
+							   extents->surface,
+							   CAIRO_OPERATOR_DEST_OUT,
+							   &_cairo_pattern_white.base,
+							   &polygon,
+							   NULL);
+    if (unlikely (status))
+	goto cleanup_polygon;
+
+    status = composite_polygon (compositor, &composite,
+				&polygon, fill_rule, antialias);
+
+    _cairo_composite_rectangles_fini (&composite);
+cleanup_polygon:
+    _cairo_polygon_fini (&polygon);
+
+    return status;
+}
+
+static cairo_int_status_t
+fixup_unbounded_boxes (const cairo_spans_compositor_t *compositor,
+		       const cairo_composite_rectangles_t *extents,
+		       cairo_boxes_t *boxes)
+{
+    cairo_boxes_t tmp, clear;
+    cairo_box_t box;
+    cairo_int_status_t status;
+
+    assert (boxes->is_pixel_aligned);
+
+    if (extents->bounded.width  == extents->unbounded.width &&
+	extents->bounded.height == extents->unbounded.height)
+    {
+	return CAIRO_STATUS_SUCCESS;
+    }
+
+    /* subtract the drawn boxes from the unbounded area */
+    _cairo_boxes_init (&clear);
+
+    box.p1.x = _cairo_fixed_from_int (extents->unbounded.x + extents->unbounded.width);
+    box.p1.y = _cairo_fixed_from_int (extents->unbounded.y);
+    box.p2.x = _cairo_fixed_from_int (extents->unbounded.x);
+    box.p2.y = _cairo_fixed_from_int (extents->unbounded.y + extents->unbounded.height);
+
+    if (boxes->num_boxes) {
+	_cairo_boxes_init (&tmp);
+
+	status = _cairo_boxes_add (&tmp, CAIRO_ANTIALIAS_DEFAULT, &box);
+	assert (status == CAIRO_INT_STATUS_SUCCESS);
+
+	tmp.chunks.next = &boxes->chunks;
+	tmp.num_boxes += boxes->num_boxes;
+
+	status = _cairo_bentley_ottmann_tessellate_boxes (&tmp,
+							  CAIRO_FILL_RULE_WINDING,
+							  &clear);
+	tmp.chunks.next = NULL;
+	if (unlikely (status))
+	    goto error;
+    } else {
+	box.p1.x = _cairo_fixed_from_int (extents->unbounded.x);
+	box.p2.x = _cairo_fixed_from_int (extents->unbounded.x + extents->unbounded.width);
+
+	status = _cairo_boxes_add (&clear, CAIRO_ANTIALIAS_DEFAULT, &box);
+	assert (status == CAIRO_INT_STATUS_SUCCESS);
+    }
+
+    /* Now intersect with the clip boxes */
+    if (extents->clip->num_boxes) {
+	_cairo_boxes_init_for_array (&tmp,
+				     extents->clip->boxes,
+				     extents->clip->num_boxes);
+	status = _cairo_boxes_intersect (&clear, &tmp, &clear);
+	if (unlikely (status))
+	    goto error;
+    }
+
+    /* If we have a clip polygon, we need to intersect with that as well */
+    if (extents->clip->path) {
+	status = fixup_unbounded_polygon (compositor, extents, &clear);
+	if (status == CAIRO_INT_STATUS_UNSUPPORTED)
+	    status = fixup_unbounded_mask (compositor, extents, &clear);
+    } else {
+	status = compositor->fill_boxes (extents->surface,
+					 CAIRO_OPERATOR_CLEAR,
+					 CAIRO_COLOR_TRANSPARENT,
+					 &clear);
+    }
+
+error:
+    _cairo_boxes_fini (&clear);
+    return status;
+}
+
+static cairo_surface_t *
+unwrap_surface (const cairo_pattern_t *pattern)
+{
+    cairo_surface_t *surface;
+
+    surface = ((const cairo_surface_pattern_t *) pattern)->surface;
+    if (_cairo_surface_is_paginated (surface))
+	surface = _cairo_paginated_surface_get_recording (surface);
+    if (_cairo_surface_is_snapshot (surface))
+	surface = _cairo_surface_snapshot_get_target (surface);
+    if (_cairo_surface_is_observer (surface))
+	surface = _cairo_surface_observer_get_target (surface);
+    return surface;
+}
+
+static cairo_bool_t
+is_recording_pattern (const cairo_pattern_t *pattern)
+{
+    cairo_surface_t *surface;
+
+    if (pattern->type != CAIRO_PATTERN_TYPE_SURFACE)
+	return FALSE;
+
+    surface = ((const cairo_surface_pattern_t *) pattern)->surface;
+    return _cairo_surface_is_recording (surface);
+}
+
+static cairo_bool_t
+recording_pattern_contains_sample (const cairo_pattern_t *pattern,
+				   const cairo_rectangle_int_t *sample)
+{
+    cairo_recording_surface_t *surface;
+
+    if (! is_recording_pattern (pattern))
+	return FALSE;
+
+    if (pattern->extend == CAIRO_EXTEND_NONE)
+	return TRUE;
+
+    surface = (cairo_recording_surface_t *) unwrap_surface (pattern);
+    if (surface->unbounded)
+	return TRUE;
+
+    if (sample->x >= surface->extents.x &&
+	sample->y >= surface->extents.y &&
+	sample->x + sample->width <= surface->extents.x + surface->extents.width &&
+	sample->y + sample->height <= surface->extents.y + surface->extents.height)
+    {
+	return TRUE;
+    }
+
+    return FALSE;
+}
+
+static cairo_bool_t
+op_reduces_to_source (const cairo_composite_rectangles_t *extents)
+{
+    if (extents->op == CAIRO_OPERATOR_SOURCE)
+	return TRUE;
+
+    if (extents->surface->is_clear)
+	return extents->op == CAIRO_OPERATOR_OVER || extents->op == CAIRO_OPERATOR_ADD;
+
+    return FALSE;
+}
+
+static cairo_int_status_t
+composite_aligned_boxes (const cairo_spans_compositor_t		*compositor,
+			 const cairo_composite_rectangles_t	*extents,
+			 cairo_boxes_t				*boxes)
+{
+    cairo_surface_t *dst = extents->surface;
+    cairo_operator_t op = extents->op;
+    const cairo_pattern_t *source = &extents->source_pattern.base;
+    cairo_int_status_t status;
+    cairo_bool_t need_clip_mask = extents->clip->path != NULL;
+    cairo_bool_t op_is_source;
+    cairo_bool_t no_mask;
+    cairo_bool_t inplace;
+
+    if (need_clip_mask && ! extents->is_bounded)
+	return CAIRO_INT_STATUS_UNSUPPORTED;
+
+    op_is_source = op_reduces_to_source (extents);
+    no_mask = extents->mask_pattern.base.type == CAIRO_PATTERN_TYPE_SOLID &&
+	CAIRO_ALPHA_IS_OPAQUE (extents->mask_pattern.solid.color.alpha);
+    inplace = ! need_clip_mask && op_is_source && no_mask;
+
+    if (op == CAIRO_OPERATOR_SOURCE && (need_clip_mask || ! no_mask)) {
+	/* SOURCE with a mask is actually a LERP in cairo semantics */
+	/* XXX push this choice down to the backend */
+	return CAIRO_INT_STATUS_UNSUPPORTED;
+    }
+
+    /* Are we just copying a recording surface? */
+    if (inplace &&
+	recording_pattern_contains_sample (&extents->source_pattern.base,
+					   &extents->source_sample_area))
+    {
+	cairo_clip_t *recording_clip;
+	const cairo_pattern_t *source = &extents->source_pattern.base;
+
+	/* XXX could also do tiling repeat modes... */
+
+	/* first clear the area about to be overwritten */
+	if (! dst->is_clear)
+	    status = compositor->fill_boxes (dst,
+					     CAIRO_OPERATOR_CLEAR,
+					     CAIRO_COLOR_TRANSPARENT,
+					     boxes);
+
+	recording_clip = _cairo_clip_from_boxes (boxes);
+	status = _cairo_recording_surface_replay_with_clip (unwrap_surface (source),
+							    &source->matrix,
+							    dst, recording_clip);
+	_cairo_clip_destroy (recording_clip);
+
+	return status;
+    }
+
+    if (! need_clip_mask && no_mask && source->type == CAIRO_PATTERN_TYPE_SOLID) {
+	const cairo_color_t *color;
+
+	color = &((cairo_solid_pattern_t *) source)->color;
+	if (op_is_source)
+	    op = CAIRO_OPERATOR_SOURCE;
+	status = compositor->fill_boxes (dst, op, color, boxes);
+#if 0
+    } else if (inplace && source->type == CAIRO_PATTERN_TYPE_SURFACE) {
+	status = upload_inplace (compositor, extents, boxes);
+#endif
+    } else {
+	cairo_surface_t *src;
+	cairo_surface_t *mask = NULL;
+	int src_x, src_y;
+	int mask_x = 0, mask_y = 0;
+
+	/* All typical cases will have been resolved before now... */
+	if (need_clip_mask) {
+	    mask = get_clip_surface (compositor, dst, extents->clip,
+				     &extents->bounded);
+	    if (unlikely (mask->status))
+		return mask->status;
+
+	    mask_x = -extents->bounded.x;
+	    mask_y = -extents->bounded.y;
+	}
+
+	/* XXX but this is still ugly */
+	if (! no_mask) {
+	    src = compositor->pattern_to_surface (dst,
+						  &extents->mask_pattern.base,
+						  TRUE,
+						  &extents->bounded,
+						  &extents->mask_sample_area,
+						  &src_x, &src_y);
+	    if (unlikely (src->status)) {
+		cairo_surface_destroy (mask);
+		return src->status;
+	    }
+
+	    if (mask != NULL) {
+		status = compositor->composite_boxes (mask, CAIRO_OPERATOR_IN,
+						      src, NULL,
+						      src_x, src_y,
+						      0, 0,
+						      mask_x, mask_y,
+						      boxes, &extents->bounded);
+
+		cairo_surface_destroy (src);
+	    } else {
+		mask = src;
+		mask_x = src_x;
+		mask_y = src_y;
+	    }
+	}
+
+	if (mask && op == CAIRO_OPERATOR_CLEAR) {
+	    source = &_cairo_pattern_white.base;
+	    op = CAIRO_OPERATOR_DEST_OUT;
+	}
+
+	src = compositor->pattern_to_surface (dst, source, FALSE,
+					      &extents->bounded,
+					      &extents->source_sample_area,
+					      &src_x, &src_y);
+	if (likely (src->status == CAIRO_STATUS_SUCCESS)) {
+	    status = compositor->composite_boxes (dst, op, src, mask,
+						  src_x, src_y,
+						  mask_x, mask_y,
+						  0, 0,
+						  boxes, &extents->bounded);
+	    cairo_surface_destroy (src);
+	} else
+	    status = src->status;
+
+	cairo_surface_destroy (mask);
+    }
+
+    if (status == CAIRO_INT_STATUS_SUCCESS && ! extents->is_bounded)
+	status = fixup_unbounded_boxes (compositor, extents, boxes);
+
+    return status;
+}
+
+static cairo_bool_t
+composite_needs_clip (const cairo_composite_rectangles_t *composit,
+		      const cairo_box_t *extents)
+{
+    cairo_bool_t needs_clip;
+
+    needs_clip = ! composit->is_bounded;
+    if (needs_clip)
+	needs_clip = ! _cairo_clip_contains_box (composit->clip, extents);
+
+    return needs_clip;
+}
+
+static cairo_int_status_t
+composite_boxes (const cairo_spans_compositor_t *compositor,
+		 cairo_composite_rectangles_t *extents,
+		 cairo_boxes_t		*boxes)
+{
+    cairo_abstract_span_renderer_t renderer;
+    cairo_rectangular_scan_converter_t converter;
+    const struct _cairo_boxes_chunk *chunk;
+    cairo_int_status_t status;
+    cairo_box_t box;
+
+    _cairo_box_from_rectangle (&box, &extents->bounded);
+    if (composite_needs_clip (extents, &box))
+	return CAIRO_INT_STATUS_UNSUPPORTED;
+
+    _cairo_rectangular_scan_converter_init (&converter, &extents->bounded);
+    for (chunk = &boxes->chunks; chunk != NULL; chunk = chunk->next) {
+	const cairo_box_t *box = chunk->base;
+	int i;
+
+	for (i = 0; i < chunk->count; i++) {
+	    status = _cairo_rectangular_scan_converter_add_box (&converter, &box[i], 1);
+	    if (unlikely (status))
+		goto cleanup_converter;
+	}
+    }
+
+    status = compositor->renderer_init (&renderer, extents, FALSE);
+    if (likely (status == CAIRO_INT_STATUS_SUCCESS))
+	status = converter.base.generate (&converter.base, &renderer.base);
+    compositor->renderer_fini (&renderer, status);
+
+cleanup_converter:
+    converter.base.destroy (&converter.base);
+    return status;
+}
+
+static cairo_int_status_t
+composite_polygon (const cairo_spans_compositor_t	*compositor,
+		   cairo_composite_rectangles_t		 *extents,
+		   cairo_polygon_t			*polygon,
+		   cairo_fill_rule_t			 fill_rule,
+		   cairo_antialias_t			 antialias)
+{
+    cairo_abstract_span_renderer_t renderer;
+    cairo_scan_converter_t *converter;
+    cairo_bool_t needs_clip;
+    cairo_int_status_t status;
+
+    needs_clip = composite_needs_clip (extents, &polygon->extents);
+    if (needs_clip) {
+	return CAIRO_INT_STATUS_UNSUPPORTED;
+	converter = _cairo_clip_tor_scan_converter_create (extents->clip,
+							   polygon,
+							   fill_rule, antialias);
+    } else {
+	const cairo_rectangle_int_t *r = &extents->bounded;
+
+	if (antialias == CAIRO_ANTIALIAS_FAST) {
+	    converter = _cairo_tor22_scan_converter_create (r->x, r->y,
+							    r->x + r->width,
+							    r->y + r->height,
+							    fill_rule, antialias);
+	    status = _cairo_tor22_scan_converter_add_polygon (converter, polygon);
+	} else if (antialias == CAIRO_ANTIALIAS_NONE) {
+	    converter = _cairo_mono_scan_converter_create (r->x, r->y,
+							   r->x + r->width,
+							   r->y + r->height,
+							   fill_rule);
+	    status = _cairo_mono_scan_converter_add_polygon (converter, polygon);
+	} else {
+	    converter = _cairo_tor_scan_converter_create (r->x, r->y,
+							  r->x + r->width,
+							  r->y + r->height,
+							  fill_rule, antialias);
+	    status = _cairo_tor_scan_converter_add_polygon (converter, polygon);
+	}
+    }
+    if (unlikely (status))
+	goto cleanup_converter;
+
+    status = compositor->renderer_init (&renderer, extents, needs_clip);
+    if (likely (status == CAIRO_INT_STATUS_SUCCESS))
+	status = converter->generate (converter, &renderer.base);
+    compositor->renderer_fini (&renderer, status);
+
+cleanup_converter:
+    converter->destroy (converter);
+    return status;
+}
+
+static cairo_int_status_t
+trim_extents_to_boxes (cairo_composite_rectangles_t *extents,
+		       cairo_boxes_t *boxes)
+{
+    cairo_box_t box;
+
+    _cairo_boxes_extents (boxes, &box);
+    return _cairo_composite_rectangles_intersect_mask_extents (extents, &box);
+}
+
+static cairo_int_status_t
+trim_extents_to_polygon (cairo_composite_rectangles_t *extents,
+			 cairo_polygon_t *polygon)
+{
+    return _cairo_composite_rectangles_intersect_mask_extents (extents,
+							       &polygon->extents);
+}
+
+static cairo_int_status_t
+clip_and_composite_boxes (const cairo_spans_compositor_t	*compositor,
+			  cairo_composite_rectangles_t		*extents,
+			  cairo_boxes_t				*boxes)
+{
+    cairo_int_status_t status;
+    cairo_polygon_t polygon;
+
+    status = trim_extents_to_boxes (extents, boxes);
+    if (unlikely (status))
+	return status;
+
+    if (boxes->num_boxes == 0) {
+	if (extents->is_bounded)
+	    return CAIRO_STATUS_SUCCESS;
+
+	return fixup_unbounded_boxes (compositor, extents, boxes);
+    }
+
+    /* Can we reduce drawing through a clip-mask to simply drawing the clip? */
+    if (extents->clip->path != NULL && extents->is_bounded) {
+	cairo_polygon_t polygon;
+	cairo_fill_rule_t fill_rule;
+	cairo_antialias_t antialias;
+	cairo_clip_t *clip;
+
+	clip = _cairo_clip_copy (extents->clip);
+	clip = _cairo_clip_intersect_boxes (clip, boxes);
+	status = _cairo_clip_get_polygon (clip, &polygon,
+					  &fill_rule, &antialias);
+	_cairo_clip_path_destroy (clip->path);
+	clip->path = NULL;
+	if (likely (status == CAIRO_INT_STATUS_SUCCESS)) {
+	    cairo_clip_t *saved_clip = extents->clip;
+	    extents->clip = clip;
+
+	    status = clip_and_composite_polygon (compositor, extents, &polygon,
+						 fill_rule, antialias);
+
+	    clip = extents->clip;
+	    extents->clip = saved_clip;
+
+	    _cairo_polygon_fini (&polygon);
+	}
+	_cairo_clip_destroy (clip);
+
+	if (status != CAIRO_INT_STATUS_UNSUPPORTED)
+	    return status;
+    }
+
+    if (boxes->is_pixel_aligned) {
+	status = composite_aligned_boxes (compositor, extents, boxes);
+	if (status != CAIRO_INT_STATUS_UNSUPPORTED)
+	    return status;
+    }
+
+    status = composite_boxes (compositor, extents, boxes);
+    if (status != CAIRO_INT_STATUS_UNSUPPORTED)
+	return status;
+
+    status = _cairo_polygon_init_boxes (&polygon, boxes);
+    if (unlikely (status))
+	return status;
+
+    status = composite_polygon (compositor, extents, &polygon,
+				CAIRO_FILL_RULE_WINDING,
+				CAIRO_ANTIALIAS_DEFAULT);
+    _cairo_polygon_fini (&polygon);
+
+    return status;
+}
+
+static cairo_int_status_t
+clip_and_composite_polygon (const cairo_spans_compositor_t	*compositor,
+			    cairo_composite_rectangles_t	 *extents,
+			    cairo_polygon_t			*polygon,
+			    cairo_fill_rule_t			 fill_rule,
+			    cairo_antialias_t			 antialias)
+{
+    cairo_int_status_t status;
+
+    if (_cairo_polygon_is_empty (polygon)) {
+	cairo_boxes_t boxes;
+
+	if (extents->is_bounded)
+	    return CAIRO_STATUS_SUCCESS;
+
+	_cairo_boxes_init (&boxes);
+	return fixup_unbounded_boxes (compositor, extents, &boxes);
+    }
+
+#if 0 /* XXX not accurate currently... */
+    if (antialias == CAIRO_ANTIALIAS_NONE)
+	return CAIRO_INT_STATUS_UNSUPPORTED;
+#endif
+
+    if (extents->is_bounded && extents->clip->path) {
+	cairo_polygon_t clipper;
+	cairo_antialias_t clip_antialias;
+	cairo_fill_rule_t clip_fill_rule;
+
+	status = _cairo_clip_get_polygon (extents->clip,
+					  &clipper,
+					  &clip_fill_rule,
+					  &clip_antialias);
+	if (likely (status == CAIRO_INT_STATUS_SUCCESS)) {
+	    cairo_clip_t *old_clip;
+
+	    if (clip_antialias == antialias) {
+		status = _cairo_polygon_intersect (polygon, fill_rule,
+						   &clipper, clip_fill_rule);
+		_cairo_polygon_fini (&clipper);
+		if (unlikely (status))
+		    return status;
+
+		old_clip = extents->clip;
+		extents->clip = _cairo_clip_copy_region (extents->clip);
+		_cairo_clip_destroy (old_clip);
+	    } else {
+		_cairo_polygon_fini (&clipper);
+	    }
+	}
+    }
+
+    status = trim_extents_to_polygon (extents, polygon);
+    if (unlikely (status))
+	return status;
+
+    return composite_polygon (compositor, extents,
+			      polygon, fill_rule, antialias);
+}
+
+/* high-level compositor interface */
+
+static cairo_int_status_t
+_cairo_spans_compositor_paint (const cairo_compositor_t		*_compositor,
+			       cairo_composite_rectangles_t	*extents)
+{
+    const cairo_spans_compositor_t *compositor = (cairo_spans_compositor_t*)_compositor;
+    cairo_boxes_t boxes;
+    cairo_int_status_t status;
+
+    _cairo_clip_steal_boxes (extents->clip, &boxes);
+    status = clip_and_composite_boxes (compositor, extents, &boxes);
+    _cairo_clip_unsteal_boxes (extents->clip, &boxes);
+
+    return status;
+}
+
+static cairo_int_status_t
+_cairo_spans_compositor_mask (const cairo_compositor_t		*_compositor,
+			      cairo_composite_rectangles_t	*extents)
+{
+    const cairo_spans_compositor_t *compositor = (cairo_spans_compositor_t*)_compositor;
+    cairo_int_status_t status;
+    cairo_boxes_t boxes;
+
+    _cairo_clip_steal_boxes (extents->clip, &boxes);
+    status = clip_and_composite_boxes (compositor, extents, &boxes);
+    _cairo_clip_unsteal_boxes (extents->clip, &boxes);
+
+    return status;
+}
+
+static cairo_int_status_t
+_cairo_spans_compositor_stroke (const cairo_compositor_t	*_compositor,
+				cairo_composite_rectangles_t	 *extents,
+				const cairo_path_fixed_t	*path,
+				const cairo_stroke_style_t	*style,
+				const cairo_matrix_t		*ctm,
+				const cairo_matrix_t		*ctm_inverse,
+				double				 tolerance,
+				cairo_antialias_t		 antialias)
+{
+    const cairo_spans_compositor_t *compositor = (cairo_spans_compositor_t*)_compositor;
+    cairo_int_status_t status;
+
+    status = CAIRO_INT_STATUS_UNSUPPORTED;
+    if (_cairo_path_fixed_stroke_is_rectilinear (path)) {
+	cairo_boxes_t boxes;
+
+	_cairo_boxes_init (&boxes);
+	if (! _cairo_clip_contains_rectangle (extents->clip, &extents->mask))
+	    _cairo_boxes_limit (&boxes,
+				extents->clip->boxes,
+				extents->clip->num_boxes);
+
+	status = _cairo_path_fixed_stroke_rectilinear_to_boxes (path,
+								style,
+								ctm,
+								antialias,
+								&boxes);
+	if (likely (status == CAIRO_INT_STATUS_SUCCESS))
+	    status = clip_and_composite_boxes (compositor, extents, &boxes);
+	_cairo_boxes_fini (&boxes);
+    }
+
+    if (status == CAIRO_INT_STATUS_UNSUPPORTED) {
+	cairo_polygon_t polygon;
+
+	if (extents->mask.width  > extents->unbounded.width ||
+	    extents->mask.height > extents->unbounded.height)
+	{
+	    _cairo_polygon_init_with_clip (&polygon, extents->clip);
+	}
+	else
+	{
+	    _cairo_polygon_init_with_clip (&polygon, NULL);
+	}
+	status = _cairo_path_fixed_stroke_to_polygon (path,
+						      style,
+						      ctm, ctm_inverse,
+						      tolerance,
+						      &polygon);
+	if (likely (status == CAIRO_INT_STATUS_SUCCESS)) {
+	    status = clip_and_composite_polygon (compositor, extents, &polygon,
+						 CAIRO_FILL_RULE_WINDING,
+						 antialias);
+	}
+	_cairo_polygon_fini (&polygon);
+    }
+
+    return status;
+}
+
+static cairo_int_status_t
+_cairo_spans_compositor_fill (const cairo_compositor_t		*_compositor,
+			      cairo_composite_rectangles_t	 *extents,
+			      const cairo_path_fixed_t		*path,
+			      cairo_fill_rule_t			 fill_rule,
+			      double				 tolerance,
+			      cairo_antialias_t			 antialias)
+{
+    const cairo_spans_compositor_t *compositor = (cairo_spans_compositor_t*)_compositor;
+    cairo_int_status_t status;
+
+    status = CAIRO_INT_STATUS_UNSUPPORTED;
+    if (_cairo_path_fixed_fill_is_rectilinear (path)) {
+	cairo_boxes_t boxes;
+
+	_cairo_boxes_init (&boxes);
+	if (! _cairo_clip_contains_rectangle (extents->clip, &extents->mask))
+	    _cairo_boxes_limit (&boxes,
+				extents->clip->boxes,
+				extents->clip->num_boxes);
+	status = _cairo_path_fixed_fill_rectilinear_to_boxes (path,
+							      fill_rule,
+							      antialias,
+							      &boxes);
+	if (likely (status == CAIRO_INT_STATUS_SUCCESS))
+	    status = clip_and_composite_boxes (compositor, extents, &boxes);
+	_cairo_boxes_fini (&boxes);
+    }
+    if (status == CAIRO_INT_STATUS_UNSUPPORTED) {
+	cairo_polygon_t polygon;
+
+	if (extents->mask.width  > extents->unbounded.width ||
+	    extents->mask.height > extents->unbounded.height)
+	{
+	    cairo_box_t limits;
+	    _cairo_box_from_rectangle (&limits, &extents->unbounded);
+	    _cairo_polygon_init (&polygon, &limits, 1);
+	}
+	else
+	{
+	    _cairo_polygon_init (&polygon, NULL, 0);
+	}
+
+	status = _cairo_path_fixed_fill_to_polygon (path, tolerance, &polygon);
+	if (likely (status == CAIRO_INT_STATUS_SUCCESS)) {
+	    status = _cairo_polygon_intersect_with_boxes (&polygon, &fill_rule,
+							  extents->clip->boxes,
+							  extents->clip->num_boxes);
+	}
+	if (likely (status == CAIRO_INT_STATUS_SUCCESS)) {
+	    if (extents->is_bounded) {
+		if (extents->clip->boxes != &extents->clip->embedded_box)
+		    free (extents->clip->boxes);
+
+		extents->clip->num_boxes = 1;
+		extents->clip->boxes = &extents->clip->embedded_box;
+		extents->clip->boxes[0] = polygon.extents;
+	    }
+	    status = clip_and_composite_polygon (compositor, extents, &polygon,
+						 fill_rule, antialias);
+	}
+	_cairo_polygon_fini (&polygon);
+    }
+
+    return status;
+}
+
+void
+_cairo_spans_compositor_init (cairo_spans_compositor_t *compositor,
+			      const cairo_compositor_t  *delegate)
+{
+    compositor->base.delegate = delegate;
+
+    compositor->base.paint  = _cairo_spans_compositor_paint;
+    compositor->base.mask   = _cairo_spans_compositor_mask;
+    compositor->base.fill   = _cairo_spans_compositor_fill;
+    compositor->base.stroke = _cairo_spans_compositor_stroke;
+    compositor->base.glyphs = NULL;
+}