Re: Problem with gdk_image_get() failing

[Ramiro Estrugo <ramiro eazel com>]

Anyone care to comment on this fix ?

I'd be happy to make patches for both gtk 1.2 and 1.3.  Also the
indentation style in the patch is wrong wrt to that in gtk, i can fix
that.

??

thanks

-re

Ramiro Estrugo wrote:
> 
> I just ran into a problem with gdk_image_get().  The issue is that if
> XGetImage() fails and returns NULL, gdk_image_get () will segfault
> trying to dereference the NULL ximage result.
> 
> For example, if the dimensions passed to XGetImage() are bogus, a
> BadMatch x error is triggered and the application seg faults.
> 
> Now, of course I agree that the caller of XGetImage() should pass in
> good values and that's what my code does.  Im sure that the passed in
> values are valid...
> 
> Im using gdk_pixbuf_get_from_drawable().  It does some sanity checks on
> the passed in dimensions using gdk_window_get_size().  Unfortunately the
> cached values returned by gdk_window_get_size() are out of whack with
> reality thus producing the BadMatch x error.
> 
> I have a test program that I can post that shows the problem, but it
> seems harmless to make gdk_image_get() more robust - especially since
> the caller will still get an x protocol error.
> 
> The simple attatched patch does this by calling XGetImage() before
> allocating the private image struct and returning NULL if XGetImage()
> fails.
> 
> thanks
> 
> -re
> 
>   ------------------------------------------------------------------------
> Index: gdkimage.c
> ===================================================================
> RCS file: /cvs/gnome/gtk+/gdk/gdkimage.c,v
> retrieving revision 1.14.2.4
> diff -u -u -r1.14.2.4 gdkimage.c
> --- gdkimage.c  2000/11/18 16:59:39     1.14.2.4
> +++ gdkimage.c  2000/12/15 03:48:17
> @@ -342,6 +342,7 @@
>    GdkImage *image;
>    GdkImagePrivate *private;
>    GdkWindowPrivate *win_private;
> +  XImage *ximage;
> 
>    g_return_val_if_fail (window != NULL, NULL);
> 
> @@ -349,16 +350,20 @@
>    if (win_private->destroyed)
>      return NULL;
> 
> +  ximage = XGetImage (gdk_display,
> +                     win_private->xwindow,
> +                     x, y, width, height,
> +                     AllPlanes, ZPixmap);
> +
> +  if (ximage == NULL)
> +         return NULL;
> +
>    private = g_new (GdkImagePrivate, 1);
>    image = (GdkImage*) private;
> 
>    private->xdisplay = gdk_display;
>    private->image_put = gdk_image_put_normal;
> -  private->ximage = XGetImage (private->xdisplay,
> -                              win_private->xwindow,
> -                              x, y, width, height,
> -                              AllPlanes, ZPixmap);
> -
> +  private->ximage = ximage;
>    image->type = GDK_IMAGE_NORMAL;
>    image->visual = gdk_window_get_visual (window);
>    image->width = width;