doc/example-smob/image-type.c

   1 /* image-type.c
   2  *
   3  * Copyright (C) 1998, 2000, 2004, 2006, 2011 Free Software Foundation, Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public License
   7  * as published by the Free Software Foundation; either version 3, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this software; see the file COPYING.LESSER.  If
  17  * not, write to the Free Software Foundation, Inc., 51 Franklin
  18  * Street, Fifth Floor, 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 {
  28   int width, height;
  29   char *pixels;
  30
  31   /* The name of this image */
  32   SCM name;
  33
  34   /* A function to call when this image is
  35      modified, e.g., to update the screen,
  36      or SCM_BOOL_F if no action necessary */
  37   SCM update_func;
  38 };
  39
  40 static SCM
  41 make_image (SCM name, SCM s_width, SCM s_height)
  42 {
  43   SCM smob;
  44   struct image *image;
  45   int width = scm_to_int (s_width);
  46   int height = scm_to_int (s_height);
  47
  48   /* Step 1: Allocate the memory block.
  49    */
  50   image = (struct image *) scm_gc_malloc (sizeof (struct image), "image");
  51
  52   /* Step 2: Initialize it with straight code.
  53    */
  54   image->width = width;
  55   image->height = height;
  56   image->pixels = NULL;
  57   image->name = SCM_BOOL_F;
  58   image->update_func = SCM_BOOL_F;
  59
  60   /* Step 3: Create the smob.
  61    */
  62   SCM_NEWSMOB (smob, image_tag, image);
  63
  64   /* Step 4: Finish the initialization.
  65    */
  66   image->name = name;
  67   image->pixels = scm_gc_malloc_pointerless (width * height, "image pixels");
  68
  69   return smob;
  70 }
  71
  72 SCM
  73 clear_image (SCM image_smob)
  74 {
  75   int area;
  76   struct image *image;
  77
  78   scm_assert_smob_type (image_tag, image_smob);
  79
  80   image = (struct image *) SCM_SMOB_DATA (image_smob);
  81   area = image->width * image->height;
  82   memset (image->pixels, 0, area);
  83
  84   /* Invoke the image's update function.
  85    */
  86   if (scm_is_true (image->update_func))
  87     scm_call_0 (image->update_func);
  88
  89   scm_remember_upto_here_1 (image_smob);
  90
  91   return SCM_UNSPECIFIED;
  92 }
  93
  94 static int
  95 print_image (SCM image_smob, SCM port, scm_print_state *pstate)
  96 {
  97   struct image *image = (struct image *) SCM_SMOB_DATA (image_smob);
  98
  99   scm_puts ("#<image ", port);
 100   scm_display (image->name, port);
 101   scm_puts (">", port);
 102
 103   /* non-zero means success */
 104   return 1;
 105 }
 106
 107 void
 108 init_image_type (void)
 109 {
 110   image_tag = scm_make_smob_type ("image", sizeof (struct image));
 111   scm_set_smob_print (image_tag, print_image);
 112
 113   scm_c_define_gsubr ("clear-image", 1, 0, 0, clear_image);
 114   scm_c_define_gsubr ("make-image", 3, 0, 0, make_image);
 115 }