xref: /freebsd/lib/libvgl/simple.c (revision 38f0b757fd84d17d0fc24739a7cda160c4516d81)
1 /*-
2  * Copyright (c) 1991-1997 Søren Schmidt
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer
10  *    in this position and unchanged.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. The name of the author may not be used to endorse or promote products
15  *    derived from this software without specific prior written permission
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27  */
28 
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
31 
32 #include <signal.h>
33 #include <sys/fbio.h>
34 #include "vgl.h"
35 
36 static byte VGLSavePaletteRed[256];
37 static byte VGLSavePaletteGreen[256];
38 static byte VGLSavePaletteBlue[256];
39 
40 #define ABS(a)		(((a)<0) ? -(a) : (a))
41 #define SGN(a)		(((a)<0) ? -1 : 1)
42 #define min(x, y)	(((x) < (y)) ? (x) : (y))
43 #define max(x, y)	(((x) > (y)) ? (x) : (y))
44 
45 static void
46 color2mem(u_long color, byte *b, int len)
47 {
48   switch (len) {
49   case 4:
50     b[3] = (color >> 24) & 0xff;
51     /* fallthrough */
52   case 3:
53     b[2] = (color >> 16) & 0xff;
54     /* fallthrough */
55   case 2:
56     b[1] = (color >> 8) & 0xff;
57     /* fallthrough */
58   case 1:
59   default:
60     b[0] = color & 0xff;
61     break;
62   }
63 
64   return;
65 }
66 
67 static u_long
68 mem2color(byte *b, int len)
69 {
70   u_long color = 0;
71 
72   switch (len) {
73   case 4:
74     color |= (b[3] & 0xff) << 24;
75     /* fallthrough */
76   case 3:
77     color |= (b[2] & 0xff) << 16;
78     /* fallthrough */
79   case 2:
80     color |= (b[1] & 0xff) << 8;
81     /* fallthrough */
82   case 1:
83   default:
84     color |= (b[0] & 0xff);
85     break;
86   }
87 
88   return color;
89 }
90 
91 void
92 VGLSetXY(VGLBitmap *object, int x, int y, u_long color)
93 {
94   int offset;
95   byte b[4];
96 
97   VGLCheckSwitch();
98   if (x>=0 && x<object->VXsize && y>=0 && y<object->VYsize) {
99     if (!VGLMouseFreeze(x, y, 1, 1, color)) {
100       switch (object->Type) {
101       case MEMBUF:
102       case VIDBUF8:
103         object->Bitmap[y*object->VXsize+x]=((byte)color);
104         break;
105       case VIDBUF8S:
106 	object->Bitmap[VGLSetSegment(y*object->VXsize+x)]=((byte)color);
107 	break;
108       case VIDBUF16:
109       case VIDBUF24:
110       case VIDBUF32:
111 	color2mem(color, b, object->PixelBytes);
112         bcopy(b, &object->Bitmap[(y*object->VXsize+x) * object->PixelBytes],
113 		object->PixelBytes);
114         break;
115       case VIDBUF16S:
116       case VIDBUF24S:
117       case VIDBUF32S:
118 	color2mem(color, b, object->PixelBytes);
119 	offset = VGLSetSegment((y*object->VXsize+x) * object->PixelBytes);
120 	bcopy(b, &object->Bitmap[offset], object->PixelBytes);
121 	break;
122       case VIDBUF8X:
123         outb(0x3c4, 0x02);
124         outb(0x3c5, 0x01 << (x&0x3));
125 	object->Bitmap[(unsigned)(VGLAdpInfo.va_line_width*y)+(x/4)] = ((byte)color);
126 	break;
127       case VIDBUF4S:
128 	offset = VGLSetSegment(y*VGLAdpInfo.va_line_width + x/8);
129 	goto set_planar;
130       case VIDBUF4:
131 	offset = y*VGLAdpInfo.va_line_width + x/8;
132 set_planar:
133         outb(0x3c4, 0x02); outb(0x3c5, 0x0f);
134         outb(0x3ce, 0x00); outb(0x3cf, (byte)color & 0x0f);	/* set/reset */
135         outb(0x3ce, 0x01); outb(0x3cf, 0x0f);		/* set/reset enable */
136         outb(0x3ce, 0x08); outb(0x3cf, 0x80 >> (x%8));	/* bit mask */
137 	object->Bitmap[offset] |= (byte)color;
138       }
139     }
140     VGLMouseUnFreeze();
141   }
142 }
143 
144 u_long
145 VGLGetXY(VGLBitmap *object, int x, int y)
146 {
147   int offset;
148   byte b[4];
149 #if 0
150   int i;
151   u_long color;
152   byte mask;
153 #endif
154 
155   VGLCheckSwitch();
156   if (x<0 || x>=object->VXsize || y<0 || y>=object->VYsize)
157     return 0;
158   switch (object->Type) {
159     case MEMBUF:
160     case VIDBUF8:
161       return object->Bitmap[((y*object->VXsize)+x)];
162     case VIDBUF8S:
163       return object->Bitmap[VGLSetSegment(y*object->VXsize+x)];
164     case VIDBUF16:
165     case VIDBUF24:
166     case VIDBUF32:
167       bcopy(&object->Bitmap[(y*object->VXsize+x) * object->PixelBytes],
168 		b, object->PixelBytes);
169       return (mem2color(b, object->PixelBytes));
170     case VIDBUF16S:
171     case VIDBUF24S:
172     case VIDBUF32S:
173 	offset = VGLSetSegment((y*object->VXsize+x) * object->PixelBytes);
174 	bcopy(&object->Bitmap[offset], b, object->PixelBytes);
175 
176       return (mem2color(b, object->PixelBytes));
177     case VIDBUF8X:
178       outb(0x3ce, 0x04); outb(0x3cf, x & 0x3);
179       return object->Bitmap[(unsigned)(VGLAdpInfo.va_line_width*y)+(x/4)];
180     case VIDBUF4S:
181       offset = VGLSetSegment(y*VGLAdpInfo.va_line_width + x/8);
182       goto get_planar;
183     case VIDBUF4:
184       offset = y*VGLAdpInfo.va_line_width + x/8;
185 get_planar:
186 #if 1
187       return (object->Bitmap[offset]&(0x80>>(x%8))) ? 1 : 0;	/* XXX */
188 #else
189       color = 0;
190       mask = 0x80 >> (x%8);
191       for (i = 0; i < VGLModeInfo.vi_planes; i++) {
192 	outb(0x3ce, 0x04); outb(0x3cf, i);
193 	color |= (object->Bitmap[offset] & mask) ? (1 << i) : 0;
194       }
195       return color;
196 #endif
197   }
198   return 0;		/* XXX black? */
199 }
200 
201  /*
202   * Symmetric Double Step Line Algorithm by Brian Wyvill from
203   * "Graphics Gems", Academic Press, 1990.
204   */
205 
206 #define SL_SWAP(a,b)           {a^=b; b^=a; a^=b;}
207 #define SL_ABSOLUTE(i,j,k)     ( (i-j)*(k = ( (i-j)<0 ? -1 : 1)))
208 
209 void
210 plot(VGLBitmap * object, int x, int y, int flag, byte color)
211 {
212   /* non-zero flag indicates the pixels need swapping back. */
213   if (flag)
214     VGLSetXY(object, y, x, color);
215   else
216     VGLSetXY(object, x, y, color);
217 }
218 
219 
220 void
221 VGLLine(VGLBitmap *object, int x1, int y1, int x2, int y2, u_long color)
222 {
223   int dx, dy, incr1, incr2, D, x, y, xend, c, pixels_left;
224   int sign_x, sign_y, step, reverse, i;
225 
226   dx = SL_ABSOLUTE(x2, x1, sign_x);
227   dy = SL_ABSOLUTE(y2, y1, sign_y);
228   /* decide increment sign by the slope sign */
229   if (sign_x == sign_y)
230     step = 1;
231   else
232     step = -1;
233 
234   if (dy > dx) {	/* chooses axis of greatest movement (make dx) */
235     SL_SWAP(x1, y1);
236     SL_SWAP(x2, y2);
237     SL_SWAP(dx, dy);
238     reverse = 1;
239   } else
240     reverse = 0;
241   /* note error check for dx==0 should be included here */
242   if (x1 > x2) {      /* start from the smaller coordinate */
243     x = x2;
244     y = y2;
245 /*  x1 = x1;
246     y1 = y1; */
247   } else {
248     x = x1;
249     y = y1;
250     x1 = x2;
251     y1 = y2;
252   }
253 
254 
255   /* Note dx=n implies 0 - n or (dx+1) pixels to be set */
256   /* Go round loop dx/4 times then plot last 0,1,2 or 3 pixels */
257   /* In fact (dx-1)/4 as 2 pixels are already plotted */
258   xend = (dx - 1) / 4;
259   pixels_left = (dx - 1) % 4;  /* number of pixels left over at the
260            * end */
261   plot(object, x, y, reverse, color);
262   if (pixels_left < 0)
263     return;      /* plot only one pixel for zero length
264            * vectors */
265   plot(object, x1, y1, reverse, color);  /* plot first two points */
266   incr2 = 4 * dy - 2 * dx;
267   if (incr2 < 0) {    /* slope less than 1/2 */
268     c = 2 * dy;
269     incr1 = 2 * c;
270     D = incr1 - dx;
271 
272     for (i = 0; i < xend; i++) {  /* plotting loop */
273       ++x;
274       --x1;
275       if (D < 0) {
276         /* pattern 1 forwards */
277         plot(object, x, y, reverse, color);
278         plot(object, ++x, y, reverse, color);
279         /* pattern 1 backwards */
280         plot(object, x1, y1, reverse, color);
281         plot(object, --x1, y1, reverse, color);
282         D += incr1;
283       } else {
284         if (D < c) {
285           /* pattern 2 forwards */
286           plot(object, x, y, reverse, color);
287           plot(object, ++x, y += step, reverse,
288               color);
289           /* pattern 2 backwards */
290           plot(object, x1, y1, reverse, color);
291           plot(object, --x1, y1 -= step, reverse,
292               color);
293         } else {
294           /* pattern 3 forwards */
295           plot(object, x, y += step, reverse, color);
296           plot(object, ++x, y, reverse, color);
297           /* pattern 3 backwards */
298           plot(object, x1, y1 -= step, reverse,
299               color);
300           plot(object, --x1, y1, reverse, color);
301         }
302         D += incr2;
303       }
304     }      /* end for */
305 
306     /* plot last pattern */
307     if (pixels_left) {
308       if (D < 0) {
309         plot(object, ++x, y, reverse, color);  /* pattern 1 */
310         if (pixels_left > 1)
311           plot(object, ++x, y, reverse, color);
312         if (pixels_left > 2)
313           plot(object, --x1, y1, reverse, color);
314       } else {
315         if (D < c) {
316           plot(object, ++x, y, reverse, color);  /* pattern 2  */
317           if (pixels_left > 1)
318             plot(object, ++x, y += step, reverse, color);
319           if (pixels_left > 2)
320             plot(object, --x1, y1, reverse, color);
321         } else {
322           /* pattern 3 */
323           plot(object, ++x, y += step, reverse, color);
324           if (pixels_left > 1)
325             plot(object, ++x, y, reverse, color);
326           if (pixels_left > 2)
327             plot(object, --x1, y1 -= step, reverse, color);
328         }
329       }
330     }      /* end if pixels_left */
331   }
332   /* end slope < 1/2 */
333   else {        /* slope greater than 1/2 */
334     c = 2 * (dy - dx);
335     incr1 = 2 * c;
336     D = incr1 + dx;
337     for (i = 0; i < xend; i++) {
338       ++x;
339       --x1;
340       if (D > 0) {
341         /* pattern 4 forwards */
342         plot(object, x, y += step, reverse, color);
343         plot(object, ++x, y += step, reverse, color);
344         /* pattern 4 backwards */
345         plot(object, x1, y1 -= step, reverse, color);
346         plot(object, --x1, y1 -= step, reverse, color);
347         D += incr1;
348       } else {
349         if (D < c) {
350           /* pattern 2 forwards */
351           plot(object, x, y, reverse, color);
352           plot(object, ++x, y += step, reverse,
353               color);
354 
355           /* pattern 2 backwards */
356           plot(object, x1, y1, reverse, color);
357           plot(object, --x1, y1 -= step, reverse,
358               color);
359         } else {
360           /* pattern 3 forwards */
361           plot(object, x, y += step, reverse, color);
362           plot(object, ++x, y, reverse, color);
363           /* pattern 3 backwards */
364           plot(object, x1, y1 -= step, reverse, color);
365           plot(object, --x1, y1, reverse, color);
366         }
367         D += incr2;
368       }
369     }      /* end for */
370     /* plot last pattern */
371     if (pixels_left) {
372       if (D > 0) {
373         plot(object, ++x, y += step, reverse, color);  /* pattern 4 */
374         if (pixels_left > 1)
375           plot(object, ++x, y += step, reverse,
376               color);
377         if (pixels_left > 2)
378           plot(object, --x1, y1 -= step, reverse,
379               color);
380       } else {
381         if (D < c) {
382           plot(object, ++x, y, reverse, color);  /* pattern 2  */
383           if (pixels_left > 1)
384             plot(object, ++x, y += step, reverse, color);
385           if (pixels_left > 2)
386             plot(object, --x1, y1, reverse, color);
387         } else {
388           /* pattern 3 */
389           plot(object, ++x, y += step, reverse, color);
390           if (pixels_left > 1)
391             plot(object, ++x, y, reverse, color);
392           if (pixels_left > 2) {
393             if (D > c)  /* step 3 */
394               plot(object, --x1, y1 -= step, reverse, color);
395             else  /* step 2 */
396               plot(object, --x1, y1, reverse, color);
397           }
398         }
399       }
400     }
401   }
402 }
403 
404 void
405 VGLBox(VGLBitmap *object, int x1, int y1, int x2, int y2, u_long color)
406 {
407   VGLLine(object, x1, y1, x2, y1, color);
408   VGLLine(object, x2, y1, x2, y2, color);
409   VGLLine(object, x2, y2, x1, y2, color);
410   VGLLine(object, x1, y2, x1, y1, color);
411 }
412 
413 void
414 VGLFilledBox(VGLBitmap *object, int x1, int y1, int x2, int y2, u_long color)
415 {
416   int y;
417 
418   for (y=y1; y<=y2; y++) VGLLine(object, x1, y, x2, y, color);
419 }
420 
421 static inline void
422 set4pixels(VGLBitmap *object, int x, int y, int xc, int yc, u_long color)
423 {
424   if (x!=0) {
425     VGLSetXY(object, xc+x, yc+y, color);
426     VGLSetXY(object, xc-x, yc+y, color);
427     if (y!=0) {
428       VGLSetXY(object, xc+x, yc-y, color);
429       VGLSetXY(object, xc-x, yc-y, color);
430     }
431   }
432   else {
433     VGLSetXY(object, xc, yc+y, color);
434     if (y!=0)
435       VGLSetXY(object, xc, yc-y, color);
436   }
437 }
438 
439 void
440 VGLEllipse(VGLBitmap *object, int xc, int yc, int a, int b, u_long color)
441 {
442   int x = 0, y = b, asq = a*a, asq2 = a*a*2, bsq = b*b;
443   int bsq2 = b*b*2, d = bsq-asq*b+asq/4, dx = 0, dy = asq2*b;
444 
445   while (dx<dy) {
446     set4pixels(object, x, y, xc, yc, color);
447     if (d>0) {
448       y--; dy-=asq2; d-=dy;
449     }
450     x++; dx+=bsq2; d+=bsq+dx;
451   }
452   d+=(3*(asq-bsq)/2-(dx+dy))/2;
453   while (y>=0) {
454     set4pixels(object, x, y, xc, yc, color);
455     if (d<0) {
456       x++; dx+=bsq2; d+=dx;
457     }
458     y--; dy-=asq2; d+=asq-dy;
459   }
460 }
461 
462 static inline void
463 set2lines(VGLBitmap *object, int x, int y, int xc, int yc, u_long color)
464 {
465   if (x!=0) {
466     VGLLine(object, xc+x, yc+y, xc-x, yc+y, color);
467     if (y!=0)
468       VGLLine(object, xc+x, yc-y, xc-x, yc-y, color);
469   }
470   else {
471     VGLLine(object, xc, yc+y, xc, yc-y, color);
472   }
473 }
474 
475 void
476 VGLFilledEllipse(VGLBitmap *object, int xc, int yc, int a, int b, u_long color)
477 {
478   int x = 0, y = b, asq = a*a, asq2 = a*a*2, bsq = b*b;
479   int bsq2 = b*b*2, d = bsq-asq*b+asq/4, dx = 0, dy = asq2*b;
480 
481   while (dx<dy) {
482     set2lines(object, x, y, xc, yc, color);
483     if (d>0) {
484       y--; dy-=asq2; d-=dy;
485     }
486     x++; dx+=bsq2; d+=bsq+dx;
487   }
488   d+=(3*(asq-bsq)/2-(dx+dy))/2;
489   while (y>=0) {
490     set2lines(object, x, y, xc, yc, color);
491     if (d<0) {
492       x++; dx+=bsq2; d+=dx;
493     }
494     y--; dy-=asq2; d+=asq-dy;
495   }
496 }
497 
498 void
499 VGLClear(VGLBitmap *object, u_long color)
500 {
501   int offset;
502   int len;
503   int i, total = 0;
504   byte b[4];
505 
506   VGLCheckSwitch();
507   VGLMouseFreeze(0, 0, object->Xsize, object->Ysize, color); /* XXX */
508   switch (object->Type) {
509   case MEMBUF:
510   case VIDBUF8:
511     memset(object->Bitmap, (byte)color, object->VXsize*object->VYsize);
512     break;
513 
514   case VIDBUF8S:
515     for (offset = 0; offset < object->VXsize*object->VYsize; ) {
516       VGLSetSegment(offset);
517       len = min(object->VXsize*object->VYsize - offset,
518 		VGLAdpInfo.va_window_size);
519       memset(object->Bitmap, (byte)color, len);
520       offset += len;
521     }
522     break;
523   case VIDBUF16:
524   case VIDBUF24:
525   case VIDBUF32:
526     color2mem(color, b, object->PixelBytes);
527     total = object->VXsize*object->VYsize*object->PixelBytes;
528     for (i = 0; i < total; i += object->PixelBytes)
529       bcopy(b, object->Bitmap + i, object->PixelBytes);
530     break;
531 
532   case VIDBUF16S:
533   case VIDBUF24S:
534   case VIDBUF32S:
535     color2mem(color, b, object->PixelBytes);
536     total = object->VXsize*object->VYsize*object->PixelBytes;
537     for (offset = 0; offset < total; ) {
538       VGLSetSegment(offset);
539       len = min(total - offset, VGLAdpInfo.va_window_size);
540       for (i = 0; i < len; i += object->PixelBytes)
541 	bcopy(b, object->Bitmap + offset + i, object->PixelBytes);
542       offset += len;
543     }
544     break;
545 
546   case VIDBUF8X:
547     /* XXX works only for Xsize % 4 = 0 */
548     outb(0x3c6, 0xff);
549     outb(0x3c4, 0x02); outb(0x3c5, 0x0f);
550     memset(object->Bitmap, (byte)color, VGLAdpInfo.va_line_width*object->VYsize);
551     break;
552 
553   case VIDBUF4:
554   case VIDBUF4S:
555     /* XXX works only for Xsize % 8 = 0 */
556     outb(0x3c4, 0x02); outb(0x3c5, 0x0f);
557     outb(0x3ce, 0x05); outb(0x3cf, 0x02);		/* mode 2 */
558     outb(0x3ce, 0x01); outb(0x3cf, 0x00);		/* set/reset enable */
559     outb(0x3ce, 0x08); outb(0x3cf, 0xff);		/* bit mask */
560     for (offset = 0; offset < VGLAdpInfo.va_line_width*object->VYsize; ) {
561       VGLSetSegment(offset);
562       len = min(object->VXsize*object->VYsize - offset,
563 		VGLAdpInfo.va_window_size);
564       memset(object->Bitmap, (byte)color, len);
565       offset += len;
566     }
567     outb(0x3ce, 0x05); outb(0x3cf, 0x00);
568     break;
569   }
570   VGLMouseUnFreeze();
571 }
572 
573 void
574 VGLRestorePalette()
575 {
576   int i;
577 
578   outb(0x3C6, 0xFF);
579   inb(0x3DA);
580   outb(0x3C8, 0x00);
581   for (i=0; i<256; i++) {
582     outb(0x3C9, VGLSavePaletteRed[i]);
583     inb(0x84);
584     outb(0x3C9, VGLSavePaletteGreen[i]);
585     inb(0x84);
586     outb(0x3C9, VGLSavePaletteBlue[i]);
587     inb(0x84);
588   }
589   inb(0x3DA);
590   outb(0x3C0, 0x20);
591 }
592 
593 void
594 VGLSavePalette()
595 {
596   int i;
597 
598   outb(0x3C6, 0xFF);
599   inb(0x3DA);
600   outb(0x3C7, 0x00);
601   for (i=0; i<256; i++) {
602     VGLSavePaletteRed[i] = inb(0x3C9);
603     inb(0x84);
604     VGLSavePaletteGreen[i] = inb(0x3C9);
605     inb(0x84);
606     VGLSavePaletteBlue[i] = inb(0x3C9);
607     inb(0x84);
608   }
609   inb(0x3DA);
610   outb(0x3C0, 0x20);
611 }
612 
613 void
614 VGLSetPalette(byte *red, byte *green, byte *blue)
615 {
616   int i;
617 
618   for (i=0; i<256; i++) {
619     VGLSavePaletteRed[i] = red[i];
620     VGLSavePaletteGreen[i] = green[i];
621     VGLSavePaletteBlue[i] = blue[i];
622   }
623   VGLCheckSwitch();
624   outb(0x3C6, 0xFF);
625   inb(0x3DA);
626   outb(0x3C8, 0x00);
627   for (i=0; i<256; i++) {
628     outb(0x3C9, VGLSavePaletteRed[i]);
629     inb(0x84);
630     outb(0x3C9, VGLSavePaletteGreen[i]);
631     inb(0x84);
632     outb(0x3C9, VGLSavePaletteBlue[i]);
633     inb(0x84);
634   }
635   inb(0x3DA);
636   outb(0x3C0, 0x20);
637 }
638 
639 void
640 VGLSetPaletteIndex(byte color, byte red, byte green, byte blue)
641 {
642   VGLSavePaletteRed[color] = red;
643   VGLSavePaletteGreen[color] = green;
644   VGLSavePaletteBlue[color] = blue;
645   VGLCheckSwitch();
646   outb(0x3C6, 0xFF);
647   inb(0x3DA);
648   outb(0x3C8, color);
649   outb(0x3C9, red); outb(0x3C9, green); outb(0x3C9, blue);
650   inb(0x3DA);
651   outb(0x3C0, 0x20);
652 }
653 
654 void
655 VGLSetBorder(byte color)
656 {
657   VGLCheckSwitch();
658   inb(0x3DA);
659   outb(0x3C0,0x11); outb(0x3C0, color);
660   inb(0x3DA);
661   outb(0x3C0, 0x20);
662 }
663 
664 void
665 VGLBlankDisplay(int blank)
666 {
667   byte val;
668 
669   VGLCheckSwitch();
670   outb(0x3C4, 0x01); val = inb(0x3C5); outb(0x3C4, 0x01);
671   outb(0x3C5, ((blank) ? (val |= 0x20) : (val &= 0xDF)));
672 }
673