[PATCH V2] xnest: Ignore GetImage() error in xnestGetImage()

[Daniel Stone]

Reviewed-by: Daniel Stone <daniel at fooishbar.org>

On 13 August 2013 07:45, Egbert Eich <eich at freedesktop.org> wrote:
> From: Radek Doulik <rodo at novell.com>
>
> When an Xnest instance is not viewable it will crash when a client in
> that instance calls GetImage. This is because the Xnest server will
> itself receives a BadMatch error.
> This patch ignores the error. The application which has requested the
> image will receive garbage - this however is fully legal according
> to the specs as obscured areas will always contain garbage if there
> isn't some sort of backing store as discussed in
> https://bugs.freedesktop.org/show_bug.cgi?id=9488
> The applied patch is a version from Dadek Doulik.
>
> v2: Call XSync() before changing error handlers as suggested by
>     Daniel Stone <daniel at fooishbar.org>.
>
> Signed-off-by: Egbert Eich <eich at freedesktop.org>
> ---
>  hw/xnest/GCOps.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/hw/xnest/GCOps.c b/hw/xnest/GCOps.c
> index e26a136..7b1956d 100644
> --- a/hw/xnest/GCOps.c
> +++ b/hw/xnest/GCOps.c
> @@ -94,15 +94,29 @@ xnestPutImage(DrawablePtr pDrawable, GCPtr pGC, int depth, int x, int y,
>      }
>  }
>
> +static int
> +xnestIgnoreErrorHandler (Display     *display,
> +                         XErrorEvent *event)
> +{
> +    return False; /* return value is ignored */
> +}
> +
>  void
>  xnestGetImage(DrawablePtr pDrawable, int x, int y, int w, int h,
>                unsigned int format, unsigned long planeMask, char *pImage)
>  {
>      XImage *ximage;
>      int length;
> +    int (*old_handler)(Display*, XErrorEvent*);
> +
> +    /* we may get BadMatch error when xnest window is minimized */
> +    XSync(xnestDisplay, False);
> +    old_handler = XSetErrorHandler (xnestIgnoreErrorHandler);
>
>      ximage = XGetImage(xnestDisplay, xnestDrawable(pDrawable),
>                         x, y, w, h, planeMask, format);
> +    XSync(xnestDisplay, False);
> +    XSetErrorHandler(old_handler);
>
>      if (ximage) {
>          length = ximage->bytes_per_line * ximage->height;
> --
> 1.8.1.4
>