summaryrefslogtreecommitdiff
path: root/Build/source/libs/libpng/libpng-1.5.10/contrib/gregbook/rpng-win.c
blob: f53ddc8ece6a5b1545738234c7330f7edc5e4c5e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
/*---------------------------------------------------------------------------

   rpng - simple PNG display program                             rpng-win.c

   This program decodes and displays PNG images, with gamma correction and
   optionally with a user-specified background color (in case the image has
   transparency).  It is very nearly the most basic PNG viewer possible.
   This version is for 32-bit Windows; it may compile under 16-bit Windows
   with a little tweaking (or maybe not).

   to do:
    - handle quoted command-line args (especially filenames with spaces)
    - have minimum window width:  oh well
    - use %.1023s to simplify truncation of title-bar string?

  ---------------------------------------------------------------------------

   Changelog:
    - 1.00:  initial public release
    - 1.01:  modified to allow abbreviated options; fixed long/ulong mis-
              match; switched to png_jmpbuf() macro
    - 1.02:  added extra set of parentheses to png_jmpbuf() macro; fixed
              command-line parsing bug
    - 1.10:  enabled "message window"/console (thanks to David Geldreich)
    - 2.00:  dual-licensed (added GNU GPL)
    - 2.01:  fixed improper display of usage screen on PNG error(s)

  ---------------------------------------------------------------------------

      Copyright (c) 1998-2008 Greg Roelofs.  All rights reserved.

      This software is provided "as is," without warranty of any kind,
      express or implied.  In no event shall the author or contributors
      be held liable for any damages arising in any way from the use of
      this software.

      The contents of this file are DUAL-LICENSED.  You may modify and/or
      redistribute this software according to the terms of one of the
      following two licenses (at your option):


      LICENSE 1 ("BSD-like with advertising clause"):

      Permission is granted to anyone to use this software for any purpose,
      including commercial applications, and to alter it and redistribute
      it freely, subject to the following restrictions:

      1. Redistributions of source code must retain the above copyright
         notice, disclaimer, and this list of conditions.
      2. Redistributions in binary form must reproduce the above copyright
         notice, disclaimer, and this list of conditions in the documenta-
         tion and/or other materials provided with the distribution.
      3. All advertising materials mentioning features or use of this
         software must display the following acknowledgment:

            This product includes software developed by Greg Roelofs
            and contributors for the book, "PNG: The Definitive Guide,"
            published by O'Reilly and Associates.


      LICENSE 2 (GNU GPL v2 or later):

      This program is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published by
      the Free Software Foundation; either version 2 of the License, or
      (at your option) any later version.

      This program is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      GNU General Public License for more details.

      You should have received a copy of the GNU General Public License
      along with this program; if not, write to the Free Software Foundation,
      Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

  ---------------------------------------------------------------------------*/

#define PROGNAME  "rpng-win"
#define LONGNAME  "Simple PNG Viewer for Windows"
#define VERSION   "2.01 of 16 March 2008"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <windows.h>
#ifdef __CYGWIN__
/* getch replacement. Turns out, we don't really need this,
 * but leave it here if we ever enable any of the uses of
 * _getch in the main code
 */
#include <unistd.h>
#include <termio.h>
#include <sys/ioctl.h>
int repl_getch( void )
{
  char ch;
  int fd = fileno(stdin);
  struct termio old_tty, new_tty;

  ioctl(fd, TCGETA, &old_tty);
  new_tty = old_tty;
  new_tty.c_lflag &= ~(ICANON | ECHO | ISIG);
  ioctl(fd, TCSETA, &new_tty);
  fread(&ch, 1, sizeof(ch), stdin);
  ioctl(fd, TCSETA, &old_tty);

  return ch;
}
#define _getch repl_getch
#else
#include <conio.h>      /* only for _getch() */
#endif

/* #define DEBUG  :  this enables the Trace() macros */

#include "readpng.h"    /* typedefs, common macros, readpng prototypes */


/* could just include png.h, but this macro is the only thing we need
 * (name and typedefs changed to local versions); note that side effects
 * only happen with alpha (which could easily be avoided with
 * "ush acopy = (alpha);") */

#define alpha_composite(composite, fg, alpha, bg) {               \
    ush temp = ((ush)(fg)*(ush)(alpha) +                          \
                (ush)(bg)*(ush)(255 - (ush)(alpha)) + (ush)128);  \
    (composite) = (uch)((temp + (temp >> 8)) >> 8);               \
}


/* local prototypes */
static int        rpng_win_create_window(HINSTANCE hInst, int showmode);
static int        rpng_win_display_image(void);
static void       rpng_win_cleanup(void);
LRESULT CALLBACK  rpng_win_wndproc(HWND, UINT, WPARAM, LPARAM);


static char titlebar[1024];
static char *progname = PROGNAME;
static char *appname = LONGNAME;
static char *filename;
static FILE *infile;

static char *bgstr;
static uch bg_red=0, bg_green=0, bg_blue=0;

static double display_exponent;

static ulg image_width, image_height, image_rowbytes;
static int image_channels;
static uch *image_data;

/* Windows-specific variables */
static ulg wimage_rowbytes;
static uch *dib;
static uch *wimage_data;
static BITMAPINFOHEADER *bmih;

static HWND global_hwnd;




int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrevInst, PSTR cmd, int showmode)
{
    char *args[1024];                 /* arbitrary limit, but should suffice */
    char *p, *q, **argv = args;
    int argc = 0;
    int rc, alen, flen;
    int error = 0;
    int have_bg = FALSE;
    double LUT_exponent;              /* just the lookup table */
    double CRT_exponent = 2.2;        /* just the monitor */
    double default_display_exponent;  /* whole display system */
    MSG msg;


    filename = (char *)NULL;

#ifndef __CYGWIN__
    /* First reenable console output, which normally goes to the bit bucket
     * for windowed apps.  Closing the console window will terminate the
     * app.  Thanks to David.Geldreich@realviz.com for supplying the magical
     * incantation. */

    AllocConsole();
    freopen("CONOUT$", "a", stderr);
    freopen("CONOUT$", "a", stdout);
#endif


    /* Next set the default value for our display-system exponent, i.e.,
     * the product of the CRT exponent and the exponent corresponding to
     * the frame-buffer's lookup table (LUT), if any.  This is not an
     * exhaustive list of LUT values (e.g., OpenStep has a lot of weird
     * ones), but it should cover 99% of the current possibilities.  And
     * yes, these ifdefs are completely wasted in a Windows program... */

#if defined(NeXT)
    LUT_exponent = 1.0 / 2.2;
    /*
    if (some_next_function_that_returns_gamma(&next_gamma))
        LUT_exponent = 1.0 / next_gamma;
     */
#elif defined(sgi)
    LUT_exponent = 1.0 / 1.7;
    /* there doesn't seem to be any documented function to get the
     * "gamma" value, so we do it the hard way */
    infile = fopen("/etc/config/system.glGammaVal", "r");
    if (infile) {
        double sgi_gamma;

        fgets(tmpline, 80, infile);
        fclose(infile);
        sgi_gamma = atof(tmpline);
        if (sgi_gamma > 0.0)
            LUT_exponent = 1.0 / sgi_gamma;
    }
#elif defined(Macintosh)
    LUT_exponent = 1.8 / 2.61;
    /*
    if (some_mac_function_that_returns_gamma(&mac_gamma))
        LUT_exponent = mac_gamma / 2.61;
     */
#else
    LUT_exponent = 1.0;   /* assume no LUT:  most PCs */
#endif

    /* the defaults above give 1.0, 1.3, 1.5 and 2.2, respectively: */
    default_display_exponent = LUT_exponent * CRT_exponent;


    /* If the user has set the SCREEN_GAMMA environment variable as suggested
     * (somewhat imprecisely) in the libpng documentation, use that; otherwise
     * use the default value we just calculated.  Either way, the user may
     * override this via a command-line option. */

    if ((p = getenv("SCREEN_GAMMA")) != NULL)
        display_exponent = atof(p);
    else
        display_exponent = default_display_exponent;


    /* Windows really hates command lines, so we have to set up our own argv.
     * Note that we do NOT bother with quoted arguments here, so don't use
     * filenames with spaces in 'em! */

    argv[argc++] = PROGNAME;
    p = cmd;
    for (;;) {
        if (*p == ' ')
            while (*++p == ' ')
                ;
        /* now p points at the first non-space after some spaces */
        if (*p == '\0')
            break;    /* nothing after the spaces:  done */
        argv[argc++] = q = p;
        while (*q && *q != ' ')
            ++q;
        /* now q points at a space or the end of the string */
        if (*q == '\0')
            break;    /* last argv already terminated; quit */
        *q = '\0';    /* change space to terminator */
        p = q + 1;
    }
    argv[argc] = NULL;   /* terminate the argv array itself */


    /* Now parse the command line for options and the PNG filename. */

    while (*++argv && !error) {
        if (!strncmp(*argv, "-gamma", 2)) {
            if (!*++argv)
                ++error;
            else {
                display_exponent = atof(*argv);
                if (display_exponent <= 0.0)
                    ++error;
            }
        } else if (!strncmp(*argv, "-bgcolor", 2)) {
            if (!*++argv)
                ++error;
            else {
                bgstr = *argv;
                if (strlen(bgstr) != 7 || bgstr[0] != '#')
                    ++error;
                else
                    have_bg = TRUE;
            }
        } else {
            if (**argv != '-') {
                filename = *argv;
                if (argv[1])   /* shouldn't be any more args after filename */
                    ++error;
            } else
                ++error;   /* not expecting any other options */
        }
    }

    if (!filename)
        ++error;


    /* print usage screen if any errors up to this point */

    if (error) {
#ifndef __CYGWIN__
        int ch;
#endif

        fprintf(stderr, "\n%s %s:  %s\n\n", PROGNAME, VERSION, appname);
        readpng_version_info();
        fprintf(stderr, "\n"
          "Usage:  %s [-gamma exp] [-bgcolor bg] file.png\n"
          "    exp \ttransfer-function exponent (``gamma'') of the display\n"
          "\t\t  system in floating-point format (e.g., ``%.1f''); equal\n"
          "\t\t  to the product of the lookup-table exponent (varies)\n"
          "\t\t  and the CRT exponent (usually 2.2); must be positive\n"
          "    bg  \tdesired background color in 7-character hex RGB format\n"
          "\t\t  (e.g., ``#ff7700'' for orange:  same as HTML colors);\n"
          "\t\t  used with transparent images\n"
          "\nPress Q, Esc or mouse button 1 after image is displayed to quit.\n"
#ifndef __CYGWIN__
          "Press Q or Esc to quit this usage screen.\n"
#endif
          "\n", PROGNAME, default_display_exponent);
#ifndef __CYGWIN__
        do
            ch = _getch();
        while (ch != 'q' && ch != 'Q' && ch != 0x1B);
#endif
        exit(1);
    }


    if (!(infile = fopen(filename, "rb"))) {
        fprintf(stderr, PROGNAME ":  can't open PNG file [%s]\n", filename);
        ++error;
    } else {
        if ((rc = readpng_init(infile, &image_width, &image_height)) != 0) {
            switch (rc) {
                case 1:
                    fprintf(stderr, PROGNAME
                      ":  [%s] is not a PNG file: incorrect signature\n",
                      filename);
                    break;
                case 2:
                    fprintf(stderr, PROGNAME
                      ":  [%s] has bad IHDR (libpng longjmp)\n", filename);
                    break;
                case 4:
                    fprintf(stderr, PROGNAME ":  insufficient memory\n");
                    break;
                default:
                    fprintf(stderr, PROGNAME
                      ":  unknown readpng_init() error\n");
                    break;
            }
            ++error;
        }
        if (error)
            fclose(infile);
    }


    if (error) {
#ifndef __CYGWIN__
        int ch;
#endif

        fprintf(stderr, PROGNAME ":  aborting.\n");
#ifndef __CYGWIN__
        do
            ch = _getch();
        while (ch != 'q' && ch != 'Q' && ch != 0x1B);
#endif
        exit(2);
    } else {
        fprintf(stderr, "\n%s %s:  %s\n", PROGNAME, VERSION, appname);
#ifndef __CYGWIN__
        fprintf(stderr,
          "\n   [console window:  closing this window will terminate %s]\n\n",
          PROGNAME);
#endif
    }


    /* set the title-bar string, but make sure buffer doesn't overflow */

    alen = strlen(appname);
    flen = strlen(filename);
    if (alen + flen + 3 > 1023)
        sprintf(titlebar, "%s:  ...%s", appname, filename+(alen+flen+6-1023));
    else
        sprintf(titlebar, "%s:  %s", appname, filename);


    /* if the user didn't specify a background color on the command line,
     * check for one in the PNG file--if not, the initialized values of 0
     * (black) will be used */

    if (have_bg) {
        unsigned r, g, b;   /* this approach quiets compiler warnings */

        sscanf(bgstr+1, "%2x%2x%2x", &r, &g, &b);
        bg_red   = (uch)r;
        bg_green = (uch)g;
        bg_blue  = (uch)b;
    } else if (readpng_get_bgcolor(&bg_red, &bg_green, &bg_blue) > 1) {
        readpng_cleanup(TRUE);
        fprintf(stderr, PROGNAME
          ":  libpng error while checking for background color\n");
        exit(2);
    }


    /* do the basic Windows initialization stuff, make the window and fill it
     * with the background color */

    if (rpng_win_create_window(hInst, showmode))
        exit(2);


    /* decode the image, all at once */

    Trace((stderr, "calling readpng_get_image()\n"))
    image_data = readpng_get_image(display_exponent, &image_channels,
      &image_rowbytes);
    Trace((stderr, "done with readpng_get_image()\n"))


    /* done with PNG file, so clean up to minimize memory usage (but do NOT
     * nuke image_data!) */

    readpng_cleanup(FALSE);
    fclose(infile);

    if (!image_data) {
        fprintf(stderr, PROGNAME ":  unable to decode PNG image\n");
        exit(3);
    }


    /* display image (composite with background if requested) */

    Trace((stderr, "calling rpng_win_display_image()\n"))
    if (rpng_win_display_image()) {
        free(image_data);
        exit(4);
    }
    Trace((stderr, "done with rpng_win_display_image()\n"))


    /* wait for the user to tell us when to quit */

    printf(
#ifndef __CYGWIN__
      "Done.  Press Q, Esc or mouse button 1 (within image window) to quit.\n"
#else
      "Done.  Press mouse button 1 (within image window) to quit.\n"
#endif
    );
    fflush(stdout);

    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }


    /* OK, we're done:  clean up all image and Windows resources and go away */

    rpng_win_cleanup();

    return msg.wParam;
}





static int rpng_win_create_window(HINSTANCE hInst, int showmode)
{
    uch *dest;
    int extra_width, extra_height;
    ulg i, j;
    WNDCLASSEX wndclass;


/*---------------------------------------------------------------------------
    Allocate memory for the display-specific version of the image (round up
    to multiple of 4 for Windows DIB).
  ---------------------------------------------------------------------------*/

    wimage_rowbytes = ((3*image_width + 3L) >> 2) << 2;

    if (!(dib = (uch *)malloc(sizeof(BITMAPINFOHEADER) +
                              wimage_rowbytes*image_height)))
    {
        return 4;   /* fail */
    }

/*---------------------------------------------------------------------------
    Initialize the DIB.  Negative height means to use top-down BMP ordering
    (must be uncompressed, but that's what we want).  Bit count of 1, 4 or 8
    implies a colormap of RGBX quads, but 24-bit BMPs just use B,G,R values
    directly => wimage_data begins immediately after BMP header.
  ---------------------------------------------------------------------------*/

    memset(dib, 0, sizeof(BITMAPINFOHEADER));
    bmih = (BITMAPINFOHEADER *)dib;
    bmih->biSize = sizeof(BITMAPINFOHEADER);
    bmih->biWidth = image_width;
    bmih->biHeight = -((long)image_height);
    bmih->biPlanes = 1;
    bmih->biBitCount = 24;
    bmih->biCompression = 0;
    wimage_data = dib + sizeof(BITMAPINFOHEADER);

/*---------------------------------------------------------------------------
    Fill in background color (black by default); data are in BGR order.
  ---------------------------------------------------------------------------*/

    for (j = 0;  j < image_height;  ++j) {
        dest = wimage_data + j*wimage_rowbytes;
        for (i = image_width;  i > 0;  --i) {
            *dest++ = bg_blue;
            *dest++ = bg_green;
            *dest++ = bg_red;
        }
    }

/*---------------------------------------------------------------------------
    Set the window parameters.
  ---------------------------------------------------------------------------*/

    memset(&wndclass, 0, sizeof(wndclass));

    wndclass.cbSize = sizeof(wndclass);
    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = rpng_win_wndproc;
    wndclass.hInstance = hInst;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)GetStockObject(DKGRAY_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = progname;
    wndclass.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

    RegisterClassEx(&wndclass);

/*---------------------------------------------------------------------------
    Finally, create the window.
  ---------------------------------------------------------------------------*/

    extra_width  = 2*(GetSystemMetrics(SM_CXBORDER) +
                      GetSystemMetrics(SM_CXDLGFRAME));
    extra_height = 2*(GetSystemMetrics(SM_CYBORDER) +
                      GetSystemMetrics(SM_CYDLGFRAME)) +
                      GetSystemMetrics(SM_CYCAPTION);

    global_hwnd = CreateWindow(progname, titlebar, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, CW_USEDEFAULT, image_width+extra_width,
      image_height+extra_height, NULL, NULL, hInst, NULL);

    ShowWindow(global_hwnd, showmode);
    UpdateWindow(global_hwnd);

    return 0;

} /* end function rpng_win_create_window() */





static int rpng_win_display_image()
{
    uch *src, *dest;
    uch r, g, b, a;
    ulg i, row, lastrow;
    RECT rect;


    Trace((stderr, "beginning display loop (image_channels == %d)\n",
      image_channels))
    Trace((stderr, "(width = %ld, rowbytes = %ld, wimage_rowbytes = %d)\n",
      image_width, image_rowbytes, wimage_rowbytes))


/*---------------------------------------------------------------------------
    Blast image data to buffer.  This whole routine takes place before the
    message loop begins, so there's no real point in any pseudo-progressive
    display...
  ---------------------------------------------------------------------------*/

    for (lastrow = row = 0;  row < image_height;  ++row) {
        src = image_data + row*image_rowbytes;
        dest = wimage_data + row*wimage_rowbytes;
        if (image_channels == 3) {
            for (i = image_width;  i > 0;  --i) {
                r = *src++;
                g = *src++;
                b = *src++;
                *dest++ = b;
                *dest++ = g;   /* note reverse order */
                *dest++ = r;
            }
        } else /* if (image_channels == 4) */ {
            for (i = image_width;  i > 0;  --i) {
                r = *src++;
                g = *src++;
                b = *src++;
                a = *src++;
                if (a == 255) {
                    *dest++ = b;
                    *dest++ = g;
                    *dest++ = r;
                } else if (a == 0) {
                    *dest++ = bg_blue;
                    *dest++ = bg_green;
                    *dest++ = bg_red;
                } else {
                    /* this macro (copied from png.h) composites the
                     * foreground and background values and puts the
                     * result into the first argument; there are no
                     * side effects with the first argument */
                    alpha_composite(*dest++, b, a, bg_blue);
                    alpha_composite(*dest++, g, a, bg_green);
                    alpha_composite(*dest++, r, a, bg_red);
                }
            }
        }
        /* display after every 16 lines */
        if (((row+1) & 0xf) == 0) {
            rect.left = 0L;
            rect.top = (LONG)lastrow;
            rect.right = (LONG)image_width;      /* possibly off by one? */
            rect.bottom = (LONG)lastrow + 16L;   /* possibly off by one? */
            InvalidateRect(global_hwnd, &rect, FALSE);
            UpdateWindow(global_hwnd);     /* similar to XFlush() */
            lastrow = row + 1;
        }
    }

    Trace((stderr, "calling final image-flush routine\n"))
    if (lastrow < image_height) {
        rect.left = 0L;
        rect.top = (LONG)lastrow;
        rect.right = (LONG)image_width;      /* possibly off by one? */
        rect.bottom = (LONG)image_height;    /* possibly off by one? */
        InvalidateRect(global_hwnd, &rect, FALSE);
        UpdateWindow(global_hwnd);     /* similar to XFlush() */
    }

/*
    last param determines whether or not background is wiped before paint
    InvalidateRect(global_hwnd, NULL, TRUE);
    UpdateWindow(global_hwnd);
 */

    return 0;
}





static void rpng_win_cleanup()
{
    if (image_data) {
        free(image_data);
        image_data = NULL;
    }

    if (dib) {
        free(dib);
        dib = NULL;
    }
}





LRESULT CALLBACK rpng_win_wndproc(HWND hwnd, UINT iMsg, WPARAM wP, LPARAM lP)
{
    HDC         hdc;
    PAINTSTRUCT ps;
    int rc;

    switch (iMsg) {
        case WM_CREATE:
            /* one-time processing here, if any */
            return 0;

        case WM_PAINT:
            hdc = BeginPaint(hwnd, &ps);
                    /*                    dest                          */
            rc = StretchDIBits(hdc, 0, 0, image_width, image_height,
                    /*                    source                        */
                                    0, 0, image_width, image_height,
                                    wimage_data, (BITMAPINFO *)bmih,
                    /*              iUsage: no clue                     */
                                    0, SRCCOPY);
            EndPaint(hwnd, &ps);
            return 0;

        /* wait for the user to tell us when to quit */
        case WM_CHAR:
            switch (wP) {      /* only need one, so ignore repeat count */
                case 'q':
                case 'Q':
                case 0x1B:     /* Esc key */
                    PostQuitMessage(0);
            }
            return 0;

        case WM_LBUTTONDOWN:   /* another way of quitting */
        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
    }

    return DefWindowProc(hwnd, iMsg, wP, lP);
}