[cairo] Implementing cairo_read_func_t/cairo_write_func_t properly

[Bernhard Fischer]

On Sunday 03 January 2016 14:29:57 Behdad Esfahbod wrote:
> On 16-01-02 09:34 PM, Bill Spitzak wrote:
> > On 01/02/2016 01:27 PM, Bernhard Fischer wrote:
> >> On Saturday 02 January 2016 13:01:39 Bill Spitzak wrote:
> >>> I think the api has to be changed to return number of bytes read, and a
> >>> negative number for eof.
> >> 
> >> The return value should be the number of bytes read and on eof it is
> >> something between 0 and length. If it is called again at/after eof it
> >> returns 0 again. A negative value (-1) is only returned in case of error
> >> (but not EOF). This is exactly like read(3) behaves.
> > 
> > Yes you are correct, I made a typo, I meant to say "error" where I wrote
> > "eof". I fully agree with your description.
> 
> Given that we cannot change the signature now, I suggest we hack it up to
> interpret negative numbers returned from the callback to be interpreted as a
> short read; the absolute value of the returned negative number is the
> number of bytes read.
> 
> Cairo itself won't need to be updated, but clients should be encouraged to
> implement the new behaviour.
> 
> b


I agree, that is a backwards compatible solution. 

Bernhard