[Spice-devel] [spice-html5] Check if streams array exists in handle_draw_jpeg_onload

[Jeremy White]

On 05/16/2018 05:17 AM, Christophe Fergeau wrote:
> From: Joel Purra <mig at joelpurra.se>
> 
> - It seems `SpiceDisplayConn` does not always have the array `this.o.sc.streams` set.
> - It also seems (stream?) images can be loaded before `streams` is set.
> - Without `streams`, or the specific stream matching `this.o.id`, `this.o.sc.streams[this.o.id].frames_loading` cannot be accessed.
> - The check for the specific stream woth `this.o.id` is already in place, this patch adds a check for `this.o.sc.streams` in `handle_draw_jpeg_onload`.
> - There might be a better place to ensure that `this.o.sc.streams` is initialized; this quick fix saved my bacon today though.
> 
> Might be related to, and perhaps fix:
> 
> - https://bugs.freedesktop.org/show_bug.cgi?id=94776
> - https://bugzilla.redhat.com/show_bug.cgi?id=1323144
> 
> Signed-off-by: Joel Purra <mig at joelpurra.se>
> ---
> 
> This is the patch attached in that pull request/added in that bug.
> 
> Christophe
> 
> 
>   display.js | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/display.js b/display.js
> index 7719b23..dbeffea 100644
> --- a/display.js
> +++ b/display.js
> @@ -883,7 +883,7 @@ function handle_draw_jpeg_onload()
>       var temp_canvas = null;
>       var context;
>   
> -    if (this.o.sc.streams[this.o.id])
> +    if ("streams" in this.o.sc && this.o.sc.streams[this.o.id])
>           this.o.sc.streams[this.o.id].frames_loading--;
>   
>       /*------------------------------------------------------------
> 

This fix is obviously correct, and a good change.  However, there is a 
similar check at the bottom of the function that would also be good to 
similarly protect.  (It's not as harmful because if the exception stops 
the async handler, there is nothing else lost as a result).

Cheers,

Jeremy