[cairo] Implementing cairo_read_func_t/cairo_write_func_t properly

[Behdad Esfahbod]

On 15-12-30 08:54 PM, Lawrence D'Oliveiro wrote:
> On Wed, 30 Dec 2015 15:27:13 +0100, Bernhard Fischer wrote:
> 
>> when I would return STATUS_READ_ERROR, then the calling function
>> cannot detect how many bytes then actually have been read except in
>> the case that I read 1 byte after the other.
> 
> Does it matter? In any case, the file is clearly corrupted and the
> image decoding has failed.
> 
> At least, that is my conclusion...

Agreed.  The error will be propagated into the surface so the surface won't be
usable anyway.

b