[cairo] Images with stride == width?

[Soeren Sandmann]

Behdad Esfahbod <behdad at behdad.org> writes:

> > diff --git a/src/cairo-image-surface.c b/src/cairo-image-surface.c
> > index 234a6f9..ae9cc75 100644
> > --- a/src/cairo-image-surface.c
> > +++ b/src/cairo-image-surface.c
> > @@ -408,7 +408,7 @@ _cairo_image_surface_create_with_content (cairo_content_t	content,
> >   *						  stride);
> >   * </programlisting></informalexample>
> >   *
> > - * Return value: the appropriate stride to use given the desired
> > + * Return value: an appropriate stride to use given the desired
> 
> How about, "the smallest appropriate stride..."?

Makes sense.

> >   * format and width, or -1 if either the format is invalid or the width
> >   * too large.
> >   *
> > @@ -442,9 +442,7 @@ slim_hidden_def (cairo_format_stride_for_width);
> >   * @width: the width of the image to be stored in the buffer
> >   * @height: the height of the image to be stored in the buffer
> >   * @stride: the number of bytes between the start of rows in the
> > - *     buffer as allocated. This value should always be computed by
> > - *     cairo_format_stride_for_width() before allocating the data
> > - *     buffer.
> > + *     buffer as allocated. This value must always be a multiple of 4.
> 
> Well, the whole point of introducing new API for stride handling was to not
> have to put the actual requirements in the API contract.  How about
> documenting that multiples of sizeof(int) are always valid strides?

It would probably have been better then to have a 

        cairo_stride_is_valid()

but ultimately, applications will want to know ahead of time whether
their existing stride is guaranteed to work or not.

The restriction to multiples of 4 ultimately comes from pixman which
currently only deals with strides in numbers of uint32, and I don't
have any plans to change that to sizeof(int).

But sizeof(int) is fine with me too, as long as we don't ever expect
to support 16 bit computers.


Soren