doc/example-smob/image-type.c

   1 /* image-type.c
   2  *
   3  *      Copyright (C) 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2, or (at your option)
   8  * any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this software; see the file COPYING.  If not, write to
  17  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  18  * Boston, MA 02110-1301 USA
  19  */
  20
  21 #include <stdlib.h>
  22 #include <libguile.h>
  23
  24 static scm_t_bits image_tag;
  25
  26 struct image {
  27   int width, height;
  28   char *pixels;
  29
  30   /* The name of this image */
  31   SCM name;
  32
  33   /* A function to call when this image is
  34      modified, e.g., to update the screen,
  35      or SCM_BOOL_F if no action necessary */
  36   SCM update_func;
  37 };
  38
  39 static SCM
  40 make_image (SCM name, SCM s_width, SCM s_height)
  41 {
  42   SCM smob;
  43   struct image *image;
  44   int width = scm_to_int (s_width);
  45   int height = scm_to_int (s_height);
  46
  47   /* Step 1: Allocate the memory block.
  48    */
  49   image = (struct image *) scm_gc_malloc (sizeof (struct image), "image");
  50
  51   /* Step 2: Initialize it with straight code.
  52    */
  53   image->width = width;
  54   image->height = height;
  55   image->pixels = NULL;
  56   image->name = SCM_BOOL_F;
  57   image->update_func = SCM_BOOL_F;
  58
  59   /* Step 3: Create the smob.
  60    */
  61   SCM_NEWSMOB (smob, image_tag, image);
  62
  63   /* Step 4: Finish the initialization.
  64    */
  65   image->name = name;
  66   image->pixels = scm_gc_malloc (width * height, "image pixels");
  67
  68   return smob;
  69 }
  70
  71 SCM
  72 clear_image (SCM image_smob)
  73 {
  74   int area;
  75   struct image *image;
  76
  77   scm_assert_smob_type (image_tag, image_smob);
  78
  79   image = (struct image *) SCM_SMOB_DATA (image_smob);
  80   area = image->width * image->height;
  81   memset (image->pixels, 0, area);
  82
  83   /* Invoke the image's update function.
  84    */
  85   if (scm_is_true (image->update_func))
  86     scm_call_0 (image->update_func);
  87
  88   scm_remember_upto_here_1 (image_smob);
  89
  90   return SCM_UNSPECIFIED;
  91 }
  92
  93 static SCM
  94 mark_image (SCM image_smob)
  95 {
  96   /* Mark the image's name and update function.  */
  97   struct image *image = (struct image *) SCM_SMOB_DATA (image_smob);
  98
  99   scm_gc_mark (image->name);
 100   return image->update_func;
 101 }
 102
 103 static size_t
 104 free_image (SCM image_smob)
 105 {
 106   struct image *image = (struct image *) SCM_SMOB_DATA (image_smob);
 107
 108   scm_gc_free (image->pixels, image->width * image->height, "image pixels");
 109   scm_gc_free (image, sizeof (struct image), "image");
 110
 111   return 0;
 112 }
 113
 114 static int
 115 print_image (SCM image_smob, SCM port, scm_print_state *pstate)
 116 {
 117   struct image *image = (struct image *) SCM_SMOB_DATA (image_smob);
 118
 119   scm_puts ("#<image ", port);
 120   scm_display (image->name, port);
 121   scm_puts (">", port);
 122
 123   /* non-zero means success */
 124   return 1;
 125 }
 126
 127 void
 128 init_image_type (void)
 129 {
 130   image_tag = scm_make_smob_type ("image", sizeof (struct image));
 131   scm_set_smob_mark (image_tag, mark_image);
 132   scm_set_smob_free (image_tag, free_image);
 133   scm_set_smob_print (image_tag, print_image);
 134
 135   scm_c_define_gsubr ("clear-image", 1, 0, 0, clear_image);
 136   scm_c_define_gsubr ("make-image", 3, 0, 0, make_image);
 137 }