[Cairo] Text APIs round 2

[Keith Packard]

Around 20 o'clock on Aug 14, Kai Wetzel wrote:

> Why not drop the explicite font from the glyph struct and use the current
> font ? In most cases the number of fonts in use is significantly smaller then
> the number of glyphs in a given piece of text.

Because it's easier for applications to just explicitly set the font for
every glyph -- otherwise, the application has to check if the font is the 
same or set it before every rendering call.  It's only temporary storage 
for each string, so memory usage isn't a serious concern.

Experience with Xft has demonstrated that of the vast number of interfaces 
provided for applications, only the unified position/glyph/font structure 
has seen any significant use.  If other applications find this so painful 
as to be a problem, we can add new interfaces in the future.  But, I'd 
rather not add interfaces that aren't going to be used.

> This also makes it a little bit more suitable for display-list construction
> because the font references don't have to be dereferenced at the time the
> list is constructed.

I can't see how this makes any difference.

-keith