Same source screen corruption resubmit [bug 829]

[Tony Lambregts <tony_lambregts@telusplanet.net>]

Change log:  Fix screen corruption when source and destination are the 
same surface,  both areas are the same size, and no flags are set. Added 
FIXME to warn user when flags are set and a  new comment explaing the 
problem.

Tony Lambregts  tony_lambregts@telusplanet.net

Index: dib.c
===================================================================
RCS file: /home/wine/wine/dlls/ddraw/dsurface/dib.c,v
retrieving revision 1.11
diff -u -r1.11 dib.c
--- dib.c	28 Jun 2002 17:32:25 -0000	1.11
+++ dib.c	4 Jul 2002 19:50:50 -0000
@@ -351,6 +351,7 @@
     int bpp, srcheight, srcwidth, dstheight, dstwidth, width;
     int x, y;
     LPBYTE dbuf, sbuf;
+    BOOL SameSurfaceOK = TRUE;
 
     TRACE("(%p)->(%p,%p,%p,%08lx,%p)\n", This,rdst,src,rsrc,dwFlags,lpbltfx);
 
@@ -474,6 +475,16 @@
 	sbase = (BYTE*)sdesc.lpSurface+(xsrc.top*sdesc.u1.lPitch)+xsrc.left*bpp;
 	xinc = (srcwidth << 16) / dstwidth;
 	yinc = (srcheight << 16) / dstheight;
+        SameSurfaceOK = (!((src == iface)&&(sbase < dbuf)&&(xdst.top < xsrc.bottom)&&(xdst.left < xsrc.right)));
+
+        /* 
+           A little explination: Screen coruption can occure if the following set of cercumstances is true 
+
+           1.) Both the source and destination are the same surface. -->(src == iface) 
+           2.) The start of the source is less than the destination .  -->(sbase < dbuf) 
+           3.) There is overlap.  -->(xdst.top < xsrc.bottom)&&(xdst.left < xsrc.right)
+           This is fixed in the case where no flags are set and the areas are the same size. 
+        */
 
 	if (!dwFlags) {
 	    /* No effects, we can cheat here */
@@ -482,11 +493,23 @@
 		    /* No stretching in either direction. This needs to be as
 		     * fast as possible */
 		    sbuf = sbase;
-		    for (y = 0; y < dstheight; y++) {
-			memcpy(dbuf, sbuf, width);
-			sbuf += sdesc.u1.lPitch;
-			dbuf += ddesc.u1.lPitch;
-		    }
+                    if (SameSurfaceOK) {
+                       for (y = 0; y < dstheight; y++) {
+                          memcpy(dbuf, sbuf, width);
+                          sbuf += sdesc.u1.lPitch;
+                          dbuf += ddesc.u1.lPitch;
+                       }
+                    } else {
+                       sbuf += (sdesc.u1.lPitch*dstheight);
+                       dbuf += (ddesc.u1.lPitch*dstheight);
+
+                       for (y = 0; y < dstheight; y++) {
+                          sbuf -= sdesc.u1.lPitch;
+                          dbuf -= ddesc.u1.lPitch;
+                          memmove(dbuf, sbuf, width);
+                       }
+                    }
+
 		} else {
 		    /* Stretching in Y direction only */
 		    for (y = sy = 0; y < dstheight; y++, sy += yinc) {
@@ -544,6 +567,10 @@
 	    }
 	} else if (dwFlags & (DDBLT_KEYSRC | DDBLT_KEYDEST | DDBLT_KEYSRCOVERRIDE | DDBLT_KEYDESTOVERRIDE)) {
 	    DWORD keylow, keyhigh;
+
+            if (!SameSurfaceOK) {
+               FIXME("\tSoure and destination surfaces are the same and could cause display problems\n");
+            }
 
 	    if (dwFlags & DDBLT_KEYSRC) {
 		keylow  = sdesc.ddckCKSrcBlt.dwColorSpaceLowValue;