[cairo] glyph extents

[Bill Spitzak]

Jonathan Kew wrote:

> Note that such clipping occurs internally within Cairo, this is not  
> just an issue for Cairo clients that may wish to clip to the glyph  
> extents. The screenshot at https://bug445087.bugzilla.mozilla.org/attachment.cgi?id=359258 
>   shows the results of a Cairo test program (also attached to that  
> bug). The clipping seen in this screenshot is happening entirely  
> within cairo_show_glyphs() and the internal Cairo functions this uses.

This is entirely inside Cairo? Then yes Cairo needs to be fixed.

If Cairo is messing with the clip region before drawing every glyph, it 
is obviously wasting a huge amount of time. It seems that is what needs 
to be addressed, not whether the clip is right, but the fact that it is 
being used at all sounds like a big problem.