Bug 3456

In xc/programs/Xserver/dix/window.c, this code exists in MakeRootTile():

    unsigned char back[128];
    ...
    register unsigned char *from, *to;
   ...
   from = (screenInfo.bitmapBitOrder == LSBFirst) ? _back_lsb : _back_msb;
   to = back;

   for (i = 4; i > 0; i--, from++)
	for (j = len; j > 0; j--)
	    *to++ = *from;

   if (blackRoot)
       bzero(back, sizeof(back));

I'm no X developer, but this looks screwy to me.  The if (blackRoot) statement
is something I do understand--for the benefit of distro makers who want their X
to start up nicely, it does away with the head-splitting hatch pattern tile. 
But it's obviously a nasty hack; it reeks of ad-hockery.  The for loop shouldn't
even be necessary with blackRoot on, so that would show up in an else (or an
#else, given a couple of changes--blackRoot originates in globals.c as a const
set to FALSE) of if (blackRoot).

But this sort of change shouldn't even require a recompile; it should be a
matter of individual taste, even if the individual doesn't feel like recompiling
X.  This is more of an environment variable sort of thing, I think, and it
should do more than just the hatch or the black.  Again, I've never developed
for X, but I offer this code for somebody who does to translate into X's
internal parlance (or at least to a more compatible C idiom) and hopefully
commit to the public codebase.


    ...
    ValidateGC((DrawablePtr)pWin->background.pixmap, pGC);
    {
        /* Process XROOTTILE env variable
            No variable:  Use default (hatch).
            Empty string: Use black.
            String:       Path to data. Hatch on failure.
        */
    
        /* see where we need to find a tile */
        char* tileloc;
        FILE* file;
    
        tileloc = getenv("XROOTTILE");

        if( tileloc != NULL ) {
            if( strcmp(tileloc,"") == 0 ) {
                /* on empty string use black root */
                memset(back, 0, sizeof(back));
            }
            else {
                /* try to load from the file */
                file = fopen(tileloc,"rb");
                if(file) {
                    /* this might fail; maybe add error checks. */
                    fread(back, sizeof(back[0]), sizeof(back), file);
                    fclose(file);
                }
                else {
                    /* default to hatch */
                    tileloc = NULL;
                }
            }
        }
    
        /* if env wasn't set or turned out to be bogus */
        if( tileloc == NULL ) {
            /* use normal hatch pattern */
            from = (screenInfo.bitmapBitOrder == LSBFirst) ? _back_lsb : _back_msb;
            to = back;
    
            for (i = 4; i > 0; i--, from++)
                for (j = len; j > 0; j--)
                    *to++ = *from;
        }
    }
    (*pGC->ops->PutImage)((DrawablePtr)pWin->background.pixmap, pGC, 1,
                0, 0, len, 4, 0, XYBitmap, (char *)back);
    ...

-- PSM