source/libs/cairo/cairo-src/src/cairo-gl-gradient.c

   1 /* cairo - a vector graphics library with display and print output
   2  *
   3  * Copyright © 2009 Eric Anholt
   4  * Copyright © 2009 Chris Wilson
   5  * Copyright © 2005,2010 Red Hat, Inc
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it either under the terms of the GNU Lesser General Public
   9  * License version 2.1 as published by the Free Software Foundation
  10  * (the "LGPL") or, at your option, under the terms of the Mozilla
  11  * Public License Version 1.1 (the "MPL"). If you do not alter this
  12  * notice, a recipient may use your version of this file under either
  13  * the MPL or the LGPL.
  14  *
  15  * You should have received a copy of the LGPL along with this library
  16  * in the file COPYING-LGPL-2.1; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
  18  * You should have received a copy of the MPL along with this library
  19  * in the file COPYING-MPL-1.1
  20  *
  21  * The contents of this file are subject to the Mozilla Public License
  22  * Version 1.1 (the "License"); you may not use this file except in
  23  * compliance with the License. You may obtain a copy of the License at
  24  * http://www.mozilla.org/MPL/
  25  *
  26  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
  27  * OF ANY KIND, either express or implied. See the LGPL or the MPL for
  28  * the specific language governing rights and limitations.
  29  *
  30  * The Original Code is the cairo graphics library.
  31  *
  32  * The Initial Developer of the Original Code is Red Hat, Inc.
  33  *
  34  * Contributor(s):
  35  *      Benjamin Otte <otte@gnome.org>
  36  *      Carl Worth <cworth@cworth.org>
  37  *      Chris Wilson <chris@chris-wilson.co.uk>
  38  *      Eric Anholt <eric@anholt.net>
  39  */
  40
  41 #include "cairoint.h"
  42
  43 #include "cairo-error-private.h"
  44 #include "cairo-gl-gradient-private.h"
  45 #include "cairo-gl-private.h"
  46
  47
  48 static int
  49 _cairo_gl_gradient_sample_width (unsigned int                 n_stops,
  50                                  const cairo_gradient_stop_t *stops)
  51 {
  52     unsigned int n;
  53     int width;
  54
  55     width = 8;
  56     for (n = 1; n < n_stops; n++) {
  57         double dx = stops[n].offset - stops[n-1].offset;
  58         double delta, max;
  59         int ramp;
  60
  61         if (dx == 0)
  62             return 1024; /* we need to emulate an infinitely sharp step */
  63
  64         max = fabs (stops[n].color.red - stops[n-1].color.red);
  65
  66         delta = fabs (stops[n].color.green - stops[n-1].color.green);
  67         if (delta > max)
  68             max = delta;
  69
  70         delta = fabs (stops[n].color.blue - stops[n-1].color.blue);
  71         if (delta > max)
  72             max = delta;
  73
  74         delta = fabs (stops[n].color.alpha - stops[n-1].color.alpha);
  75         if (delta > max)
  76             max = delta;
  77
  78         ramp = 128 * max / dx;
  79         if (ramp > width)
  80             width = ramp;
  81     }
  82
  83     return (width + 7) & -8;
  84 }
  85
  86 static uint8_t premultiply(double c, double a)
  87 {
  88     int v = c * a * 256;
  89     return v - (v >> 8);
  90 }
  91
  92 static uint32_t color_stop_to_pixel(const cairo_gradient_stop_t *stop)
  93 {
  94     uint8_t a, r, g, b;
  95
  96     a = stop->color.alpha_short >> 8;
  97     r = premultiply(stop->color.red,   stop->color.alpha);
  98     g = premultiply(stop->color.green, stop->color.alpha);
  99     b = premultiply(stop->color.blue,  stop->color.alpha);
 100
 101     if (_cairo_is_little_endian ())
 102         return a << 24 | r << 16 | g << 8 | b << 0;
 103     else
 104         return a << 0 | r << 8 | g << 16 | b << 24;
 105 }
 106
 107 static cairo_status_t
 108 _cairo_gl_gradient_render (const cairo_gl_context_t    *ctx,
 109                            unsigned int                 n_stops,
 110                            const cairo_gradient_stop_t *stops,
 111                            void                        *bytes,
 112                            int                          width)
 113 {
 114     pixman_image_t *gradient, *image;
 115     pixman_gradient_stop_t pixman_stops_stack[32];
 116     pixman_gradient_stop_t *pixman_stops;
 117     pixman_point_fixed_t p1, p2;
 118     unsigned int i;
 119     pixman_format_code_t gradient_pixman_format;
 120
 121     /*
 122      * Ensure that the order of the gradient's components in memory is BGRA.
 123      * This is done so that the gradient's pixel data is always suitable for
 124      * texture upload using format=GL_BGRA and type=GL_UNSIGNED_BYTE.
 125      */
 126     if (_cairo_is_little_endian ())
 127         gradient_pixman_format = PIXMAN_a8r8g8b8;
 128     else
 129         gradient_pixman_format = PIXMAN_b8g8r8a8;
 130
 131     pixman_stops = pixman_stops_stack;
 132     if (unlikely (n_stops > ARRAY_LENGTH (pixman_stops_stack))) {
 133         pixman_stops = _cairo_malloc_ab (n_stops,
 134                                          sizeof (pixman_gradient_stop_t));
 135         if (unlikely (pixman_stops == NULL))
 136             return _cairo_error (CAIRO_STATUS_NO_MEMORY);
 137     }
 138
 139     for (i = 0; i < n_stops; i++) {
 140         pixman_stops[i].x = _cairo_fixed_16_16_from_double (stops[i].offset);
 141         pixman_stops[i].color.red   = stops[i].color.red_short;
 142         pixman_stops[i].color.green = stops[i].color.green_short;
 143         pixman_stops[i].color.blue  = stops[i].color.blue_short;
 144         pixman_stops[i].color.alpha = stops[i].color.alpha_short;
 145     }
 146
 147     p1.x = _cairo_fixed_16_16_from_double (0.5);
 148     p1.y = 0;
 149     p2.x = _cairo_fixed_16_16_from_double (width - 0.5);
 150     p2.y = 0;
 151
 152     gradient = pixman_image_create_linear_gradient (&p1, &p2,
 153                                                     pixman_stops,
 154                                                     n_stops);
 155     if (pixman_stops != pixman_stops_stack)
 156         free (pixman_stops);
 157
 158     if (unlikely (gradient == NULL))
 159         return _cairo_error (CAIRO_STATUS_NO_MEMORY);
 160
 161     pixman_image_set_filter (gradient, PIXMAN_FILTER_BILINEAR, NULL, 0);
 162     pixman_image_set_repeat (gradient, PIXMAN_REPEAT_PAD);
 163
 164     image = pixman_image_create_bits (gradient_pixman_format, width, 1,
 165                                       bytes, sizeof(uint32_t)*width);
 166     if (unlikely (image == NULL)) {
 167         pixman_image_unref (gradient);
 168         return _cairo_error (CAIRO_STATUS_NO_MEMORY);
 169     }
 170
 171     pixman_image_composite32 (PIXMAN_OP_SRC,
 172                               gradient, NULL, image,
 173                               0, 0,
 174                               0, 0,
 175                               0, 0,
 176                               width, 1);
 177
 178     pixman_image_unref (gradient);
 179     pixman_image_unref (image);
 180
 181     /* We need to fudge pixel 0 to hold the left-most color stop and not
 182      * the neareset stop to the zeroth pixel centre in order to correctly
 183      * populate the border color. For completeness, do both edges.
 184      */
 185     ((uint32_t*)bytes)[0] = color_stop_to_pixel(&stops[0]);
 186     ((uint32_t*)bytes)[width-1] = color_stop_to_pixel(&stops[n_stops-1]);
 187
 188     return CAIRO_STATUS_SUCCESS;
 189 }
 190
 191 static unsigned long
 192 _cairo_gl_gradient_hash (unsigned int                  n_stops,
 193                          const cairo_gradient_stop_t  *stops)
 194 {
 195     return _cairo_hash_bytes (n_stops,
 196                               stops,
 197                               sizeof (cairo_gradient_stop_t) * n_stops);
 198 }
 199
 200 static cairo_gl_gradient_t *
 201 _cairo_gl_gradient_lookup (cairo_gl_context_t           *ctx,
 202                            unsigned long                 hash,
 203                            unsigned int                  n_stops,
 204                            const cairo_gradient_stop_t  *stops)
 205 {
 206     cairo_gl_gradient_t lookup;
 207
 208     lookup.cache_entry.hash = hash,
 209     lookup.n_stops = n_stops;
 210     lookup.stops = stops;
 211
 212     return _cairo_cache_lookup (&ctx->gradients, &lookup.cache_entry);
 213 }
 214
 215 cairo_bool_t
 216 _cairo_gl_gradient_equal (const void *key_a, const void *key_b)
 217 {
 218     const cairo_gl_gradient_t *a = key_a;
 219     const cairo_gl_gradient_t *b = key_b;
 220
 221     if (a->n_stops != b->n_stops)
 222         return FALSE;
 223
 224     return memcmp (a->stops, b->stops, a->n_stops * sizeof (cairo_gradient_stop_t)) == 0;
 225 }
 226
 227 cairo_int_status_t
 228 _cairo_gl_gradient_create (cairo_gl_context_t           *ctx,
 229                            unsigned int                  n_stops,
 230                            const cairo_gradient_stop_t  *stops,
 231                            cairo_gl_gradient_t         **gradient_out)
 232 {
 233     unsigned long hash;
 234     cairo_gl_gradient_t *gradient;
 235     cairo_status_t status;
 236     int tex_width;
 237     GLint internal_format;
 238     void *data;
 239
 240     if ((unsigned int) ctx->max_texture_size / 2 <= n_stops)
 241         return CAIRO_INT_STATUS_UNSUPPORTED;
 242
 243     hash = _cairo_gl_gradient_hash (n_stops, stops);
 244
 245     gradient = _cairo_gl_gradient_lookup (ctx, hash, n_stops, stops);
 246     if (gradient) {
 247         *gradient_out = _cairo_gl_gradient_reference (gradient);
 248         return CAIRO_STATUS_SUCCESS;
 249     }
 250
 251     gradient = malloc (sizeof (cairo_gl_gradient_t) + sizeof (cairo_gradient_stop_t) * (n_stops - 1));
 252     if (gradient == NULL)
 253         return _cairo_error (CAIRO_STATUS_NO_MEMORY);
 254
 255     tex_width = _cairo_gl_gradient_sample_width (n_stops, stops);
 256     if (tex_width > ctx->max_texture_size)
 257         tex_width = ctx->max_texture_size;
 258
 259     CAIRO_REFERENCE_COUNT_INIT (&gradient->ref_count, 2);
 260     gradient->cache_entry.hash = hash;
 261     gradient->cache_entry.size = tex_width;
 262     gradient->device = &ctx->base;
 263     gradient->n_stops = n_stops;
 264     gradient->stops = gradient->stops_embedded;
 265     memcpy (gradient->stops_embedded, stops, n_stops * sizeof (cairo_gradient_stop_t));
 266
 267     glGenTextures (1, &gradient->tex);
 268     _cairo_gl_context_activate (ctx, CAIRO_GL_TEX_TEMP);
 269     glBindTexture (ctx->tex_target, gradient->tex);
 270
 271     data = _cairo_malloc_ab (tex_width, sizeof (uint32_t));
 272     if (unlikely (data == NULL)) {
 273         status = _cairo_error (CAIRO_STATUS_NO_MEMORY);
 274         goto cleanup_gradient;
 275     }
 276
 277     status = _cairo_gl_gradient_render (ctx, n_stops, stops, data, tex_width);
 278     if (unlikely (status))
 279         goto cleanup_data;
 280
 281     /*
 282      * In OpenGL ES 2.0 no format conversion is allowed i.e. 'internalFormat'
 283      * must match 'format' in glTexImage2D.
 284      */
 285     if (_cairo_gl_get_flavor () == CAIRO_GL_FLAVOR_ES)
 286         internal_format = GL_BGRA;
 287     else
 288         internal_format = GL_RGBA;
 289
 290     glTexImage2D (ctx->tex_target, 0, internal_format, tex_width, 1, 0,
 291                   GL_BGRA, GL_UNSIGNED_BYTE, data);
 292
 293     free (data);
 294
 295     /* we ignore errors here and just return an uncached gradient */
 296     if (unlikely (_cairo_cache_insert (&ctx->gradients, &gradient->cache_entry)))
 297         CAIRO_REFERENCE_COUNT_INIT (&gradient->ref_count, 1);
 298
 299     *gradient_out = gradient;
 300     return CAIRO_STATUS_SUCCESS;
 301
 302 cleanup_data:
 303     free (data);
 304 cleanup_gradient:
 305     free (gradient);
 306     return status;
 307 }
 308
 309 cairo_gl_gradient_t *
 310 _cairo_gl_gradient_reference (cairo_gl_gradient_t *gradient)
 311 {
 312     assert (CAIRO_REFERENCE_COUNT_HAS_REFERENCE (&gradient->ref_count));
 313
 314     _cairo_reference_count_inc (&gradient->ref_count);
 315
 316     return gradient;
 317 }
 318
 319 void
 320 _cairo_gl_gradient_destroy (cairo_gl_gradient_t *gradient)
 321 {
 322     cairo_gl_context_t *ctx;
 323     cairo_status_t ignore;
 324
 325     assert (CAIRO_REFERENCE_COUNT_HAS_REFERENCE (&gradient->ref_count));
 326
 327     if (! _cairo_reference_count_dec_and_test (&gradient->ref_count))
 328         return;
 329
 330     if (_cairo_gl_context_acquire (gradient->device, &ctx) == CAIRO_STATUS_SUCCESS) {
 331         /* The gradient my still be active in the last operation, so flush */
 332         _cairo_gl_composite_flush (ctx);
 333         glDeleteTextures (1, &gradient->tex);
 334         ignore = _cairo_gl_context_release (ctx, CAIRO_STATUS_SUCCESS);
 335     }
 336
 337     free (gradient);
 338 }