[cairo] BUG: Cairo reports CAIRO_STATUS_SUCCESS even if writing to disk failed (SVG and PS backend)

[Uli Schlachter]

Am 23.07.21 um 08:55 schrieb Knut Petersen:
> Hi erverybody!
> 
> I'm testing a cairo backend I wrote for the GNU Lilypond music engraver.
> 
> I generate several output formats in parallel and test for errors using
> this C++ code:
> 
>       for (auto &cr : Cairo_output.contexts) // loop over a set of crs
>         {
>           auto status = cairo_status (cr);
>           if (status != CAIRO_STATUS_SUCCESS)
>             error (_f ("Cairo status %s", cairo_status_to_string
> (status))); // display an error msg and abort
>         }
> 
> If writing to an output file fails because there is no more free disk
> space and the cr is connected to a pdf surface this works fine:
> 
>    Fitting music on 1 or 2 pages...
>    Drawing systems...
>    Generating test.cairo.pdf ...
>    fatal error: Cairo status reports 'error while writing to output stream'
> 
> Unfortunately this code fails for the cairo postscript backend and the
> cairo svg backend - cairo_status reports CAIRO_STATUS_SUCCESS even if
> writing to disk failed because there is no free disk space.

"Fail" here means "does not report an error, even though it should", right?

Are you calling something like
cairo_surface_finish(cairo_get_target(cr)) before the above? I think
that most of these file-output-backends only actually write the output
when the surface is finished. Before that, no errors could occur yet.

If this is not it, then I don't know. Sorry.

Cheers,
Uli
-- 
<alanc> I think someone had a Xprint version of glxgears at one point,
    but benchmarking how many GL pages you can print per second
    was deemed too silly to merge