svn commit: r345481 - head/lib/libvgl

[Bruce Evans]

Author: bde
Date: Sun Mar 24 19:27:03 2019
New Revision: 345481
URL: https://svnweb.freebsd.org/changeset/base/345481

Log:
  Fix reading of pixels in (4 and 8-plane) planar modes.
  
  There seems to be no alternative to reading each plane independently using
  3 slow i/o's per plane (this delivers 8 nearby pixels, but we don't buffer
  the results so run 8 times slower than necessary.
  
  All the code for this was there, but it was ifdefed out and replaced by
  simpler code that cannot work in planar modes.  The ifdefed out code
  was correct except it was missing a volatile declaration, so compilers
  optimized the multiple dummy reads in it to a single read.

Modified:
  head/lib/libvgl/simple.c

Modified: head/lib/libvgl/simple.c
==============================================================================
--- head/lib/libvgl/simple.c	Sun Mar 24 19:11:45 2019	(r345480)
+++ head/lib/libvgl/simple.c	Sun Mar 24 19:27:03 2019	(r345481)
@@ -148,11 +148,9 @@ VGLGetXY(VGLBitmap *object, int x, int y)
 {
   int offset;
   byte b[4];
-#if 0
   int i;
   u_long color;
   byte mask;
-#endif
 
   VGLCheckSwitch();
   if (x<0 || x>=object->VXsize || y<0 || y>=object->VYsize)
@@ -185,17 +183,14 @@ VGLGetXY(VGLBitmap *object, int x, int y)
     case VIDBUF4:
       offset = y*VGLAdpInfo.va_line_width + x/8;
 get_planar:
-#if 1
-      return (object->Bitmap[offset]&(0x80>>(x%8))) ? 1 : 0;	/* XXX */
-#else
       color = 0;
       mask = 0x80 >> (x%8);
       for (i = 0; i < VGLModeInfo.vi_planes; i++) {
 	outb(0x3ce, 0x04); outb(0x3cf, i);
-	color |= (object->Bitmap[offset] & mask) ? (1 << i) : 0;
+	color |= (((volatile VGLBitmap *)object)->Bitmap[offset] & mask) ?
+		 (1 << i) : 0;
       }
       return color;
-#endif
   }
   return 0;		/* XXX black? */
 }