[Cairo] Re: [xsvg] cairo_text_extents ?
cworth at east.isi.edu
Tue Nov 25 12:07:58 PST 2003
On Nov 25, Bill Spitzak wrote:
> Aren't "ascent" and "descent" sometimes different values that are supplied
> for the whole font?
Yes, and those numbers are available via the cairo_font_extents_t
structure and the cairo_font_extents function.
> I think it may not be a good idea to use these numbers here.
We're not using those numbers. I'll grant you that the current names
may be confusing though.
> My preference is to make everything signed and in the identical coordinate
> system, where 0,0 is the current text position on the baseline. The names can
> then be:
> left, bottom : coordinate of lower-left of bounding box
> top, right : coordinate of top-right of bounding box
> dx, dy : recommended origin for the next character
My preference is to model the metrics after a well-accepted system,
(see my other mail on this issue).
> I'm also in favor of having a current text transfomation matrix that is used
> to position all text, so that dy is always zero. This idea is apparently
> either being ignored or unpopular, but I will try to describe it again in
> another email.
I'm not familiar with the idea, (maybe I missed it in that giant
flurry of text API discussion while I was on vacation some time
ago). So I'll look forward to your email.
In the meantime, the philosophy behind the current API is quite simple:
cairo_show_text starts at the current point and uses the font metrics
to position each subsequent glyph.
cairo_show_glyphs lets the user position each glyph directly at the
specified user space coordinates.
To me, this seems like a good way to hit both ends of the
simple-to-use <-> full-control spectrum without much API clutter.
But, I'm always open to other suggestions.
More information about the cairo