Re: dib fixes

[Rein Klazes]

On 11 Apr 2005 17:48:58 +0200, you wrote:
> Rein Klazes  writes:
> > I tried to do this, you need to clip to the visible region as well. I
> > could not get it 100% full proof because of races between the clip
> > calculations and the actual positions on the screen.
> >
> > So I get the pixels now from the root window (clipped to the screen) and
> > everything is rock solid. The code is simpler too.
>
> That's ugly, and it will fail miserably if the drawable is a bitmap,
> you really have to use the specified drawable. Look at how the BitBlt
> code does it to determine the proper limits.

Hmm, I was looking at BitBlt for ideas. This was the straight forward
implementation but then discarded:

static void X11DRV_DIB_SetImageBits_GetSubImage(
         const X11DRV_DIB_IMAGEBITS_DESCR *descr, XImage *bmpImage)
 {
     /* compressed bitmaps may contain gaps in them. So make a copy
      * of the existing pixels first */
     RECT bmprc = { descr->xDest, descr->yDest,
         descr->xDest + descr->width , descr->yDest + descr->height};
     RECT rc;

GetRgnBox( descr->physDev->region, &rc );
     /* convert from dc to drawable origin */
     OffsetRect( &rc, descr->physDev->org.x, descr->physDev->org.y);

/* clip visible rect with bitmap */
     if( IntersectRect( &rc, &rc, &bmprc))
         XGetSubImage( gdi_display, descr->drawable, rc.left, rc.top,
                 rc.right - rc.left, rc.bottom - rc.top, AllPlanes,
                 ZPixmap, bmpImage,
                 descr->xSrc + rc.left - bmprc.left,
                 descr->ySrc + rc.top - bmprc.top);
 }

As soon as I move the window to which I am calling SetDIBitsToDevice
partly outside of the screen, the drawable lies partly outside the
screen rectangle and XGetSubImage fails -> crash. 
Clipping to the screen rectangle helps somewhat for very slow moves, but
with faster moves I still get those failures.

What am I doing wrong here?

Rein.