cairo/src/cairo-cogl-utils.c
Robert Bragg 571a27b4fc backends: Adds a new Cogl based backend
This adds a new GPU accelerated backend for Cairo based on the Cogl 3D
graphics API.

This backend aims to support Cairo in a way that translates as naturally
as possible to using a GPU, it does not strive to compete with the
anti-aliasing quality of the image backend if it can't be done
efficiently using the GPU - raw performance isn't the only metric of
concern, so is power usage.

As an overview of how the backend works:
- fills are handled by tessellating paths into triangles
- the backend has an extra fill_rectangle drawing operation so we have
  a fast-path for drawing rectangles which are so common.
- strokes are also tessellated into triangles.
- stroke and fill tessellations are cached to avoid the cpu overhead
  of tessellation and cost of upload given that its common for apps to
  re-draw the same path multiple times. The tessellations can survive
  translations and rotations increasing the probability that they can be
  re-used.
- sources and masks are handled using multi-texturing.
- clipping is handled with a scissor and the stencil buffer which
  we're careful to only update when they really change.
- linear gradients are rendered to a 1d texture using a triangle
  strip + interpolating color attributes. All cairo extend modes
  are handled by corresponding texture sampler wrap modes without
  needing programmable fragment processing.
- antialiasing should be handled using Cogl's multisampling API

XXX: This is a work in progress!!
TODO:
- handle at least basic radial gradients (No need to handle full
  pdf semantics, since css, svg and canvas only allow radial gradients
  defined as one circle + a point that must lie within the first
  circle.) - currently we fall back to pixman for radial gradients.
- support glyph rendering with a decent glyph cache design. The
  current plan is a per scaled-font growable cache texture + a
  scratch cache for one-shot/short-lived glyphs.
- decide how to handle npot textures when lacking hardware support.
  Current plan is to add a transparent border to npot textures and use
  CLAMP_TO_EDGE for the default EXTEND_NONE semantics. For anything else
  we can allocate a shadow npot texture and scale the original to fit
  that so we can map extend modes to texture sampler modes.
2011-10-11 09:05:45 +01:00

126 lines
3.6 KiB
C

/* cairo - a vector graphics library with display and print output
*
* 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.og/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.
*
* Contributor(s):
* Robert Bragg <robert@linux.intel.com>
*/
#include "cairoint.h"
#include "cairo-cogl-utils-private.h"
#include <cogl/cogl.h>
#include <glib.h>
static cairo_status_t
_cogl_move_to (void *closure,
const cairo_point_t *point)
{
cogl_path_move_to (closure,
_cairo_cogl_util_fixed_to_float (point->x),
_cairo_cogl_util_fixed_to_float (point->y));
return CAIRO_STATUS_SUCCESS;
}
static cairo_status_t
_cogl_line_to (void *closure,
const cairo_point_t *point)
{
cogl_path_line_to (closure,
_cairo_cogl_util_fixed_to_float (point->x),
_cairo_cogl_util_fixed_to_float (point->y));
return CAIRO_STATUS_SUCCESS;
}
static cairo_status_t
_cogl_curve_to (void *closure,
const cairo_point_t *p0,
const cairo_point_t *p1,
const cairo_point_t *p2)
{
cogl_path_curve_to (closure,
_cairo_cogl_util_fixed_to_float (p0->x),
_cairo_cogl_util_fixed_to_float (p0->y),
_cairo_cogl_util_fixed_to_float (p1->x),
_cairo_cogl_util_fixed_to_float (p1->y),
_cairo_cogl_util_fixed_to_float (p2->x),
_cairo_cogl_util_fixed_to_float (p2->y));
return CAIRO_STATUS_SUCCESS;
}
static cairo_status_t
_cogl_close_path (void *closure)
{
cogl_path_close (closure);
return CAIRO_STATUS_SUCCESS;
}
CoglPath *
_cairo_cogl_util_path_from_cairo (const cairo_path_fixed_t *path,
cairo_fill_rule_t fill_rule,
float tolerance)
{
CoglPath *cogl_path = cogl_path_new ();
cairo_status_t status;
if (fill_rule == CAIRO_FILL_RULE_EVEN_ODD)
cogl_path_set_fill_rule (cogl_path, COGL_PATH_FILL_RULE_EVEN_ODD);
else
cogl_path_set_fill_rule (cogl_path, COGL_PATH_FILL_RULE_NON_ZERO);
#ifdef USE_CAIRO_PATH_FLATTENER
/* XXX: rely on cairo to do path flattening, since it seems Cogl's
* curve_to flattening is much slower */
status = _cairo_path_fixed_interpret_flat (path,
_cogl_move_to,
_cogl_line_to,
_cogl_close_path,
cogl_path,
tolerance);
#else
status = _cairo_path_fixed_interpret (path,
_cogl_move_to,
_cogl_line_to,
_cogl_curve_to,
_cogl_close_path,
cogl_path);
#endif
assert (status == CAIRO_STATUS_SUCCESS);
return cogl_path;
}
int
_cairo_cogl_util_next_p2 (int a)
{
int rval = 1;
while (rval < a)
rval <<= 1;
return rval;
}