svn commit: r346416 - head/lib/libvgl

[Bruce Evans]

Author: bde
Date: Fri Apr 19 20:29:49 2019
New Revision: 346416
URL: https://svnweb.freebsd.org/changeset/base/346416

Log:
  Fix copying of overlapping bitmaps.  The cases of copying within the
  screen bitmap and within a single MEMBUF were broken when first source
  line is before the first destination line and the sub-bitmaps overlap.
  
  The fix just copies horizontal lines in reverse order when the first
  source line is before the first destination line.  This switches
  directions unnecessarily in some cases, but the switch is about as
  fast as doing a precise detection of overlaps.  When the first lines
  are the same, there can be undetected overlap in the horizontal
  direction.  The old code already handles this mostly accidentally by
  using bcopy() for MEMBUFs and by copying through a temporary buffer
  for the screen bitmap although the latter is sub-optimal in direct
  modes.

Modified:
  head/lib/libvgl/bitmap.c

Modified: head/lib/libvgl/bitmap.c
==============================================================================
--- head/lib/libvgl/bitmap.c	Fri Apr 19 20:23:39 2019	(r346415)
+++ head/lib/libvgl/bitmap.c	Fri Apr 19 20:29:49 2019	(r346416)
@@ -269,7 +269,7 @@ int
 __VGLBitmapCopy(VGLBitmap *src, int srcx, int srcy,
 	      VGLBitmap *dst, int dstx, int dsty, int width, int hight)
 {
-  int srcline, dstline;
+  int srcline, dstline, yend, yextra, ystep;
 
   if (srcx>src->VXsize || srcy>src->VYsize
 	|| dstx>dst->VXsize || dsty>dst->VYsize)
@@ -296,8 +296,17 @@ __VGLBitmapCopy(VGLBitmap *src, int srcx, int srcy,
      hight=dst->VYsize-dsty;
   if (width < 0 || hight < 0)
      return -1;
+  yend = srcy + hight;
+  yextra = 0;
+  ystep = 1;
+  if (src->Bitmap == dst->Bitmap && srcy < dsty) {
+    yend = srcy;
+    yextra = hight - 1;
+    ystep = -1;
+  }
   if (src->Type == MEMBUF) {
-    for (srcline=srcy, dstline=dsty; srcline<srcy+hight; srcline++, dstline++) {
+    for (srcline = srcy + yextra, dstline = dsty + yextra; srcline != yend;
+         srcline += ystep, dstline += ystep) {
       WriteVerticalLine(dst, dstx, dstline, width, 
         src->Bitmap+(srcline*src->VXsize+srcx)*dst->PixelBytes);
     }
@@ -319,7 +328,8 @@ __VGLBitmapCopy(VGLBitmap *src, int srcx, int srcy,
     } else {
       p = buffer;
     }
-    for (srcline=srcy, dstline=dsty; srcline<srcy+hight; srcline++, dstline++) {
+    for (srcline = srcy + yextra, dstline = dsty + yextra; srcline != yend;
+         srcline += ystep, dstline += ystep) {
       ReadVerticalLine(src, srcx, srcline, width, p);
       WriteVerticalLine(dst, dstx, dstline, width, p);
     }