PDF backend (was: backends)

John Hunter <jdhunter@...5...> writes:

As you may know, we have a prototype of a PDF backend, though it is
missing many features.

I've been offline for a while (and will be for at least a week more),
but I hacked a bit more on the PDF backend and just did a commit. Now
it tries to support images and mathtext, but both are incomplete.
Here's what I think is currently missing:

* the alpha channel of images is not used (I think this is easy to do)
* image compression could be improved (PDF supports png-like compression)
* there are encoding problems in text, especially in mathtext
   (e.g. \alpha doesn't show up)
* mathtext positioning seems a bit off
* no unicode support in text (or mathtext)
* no Type 1 or Base-14 font support (i.e., "pdf.use_afm")
* TTF support has lots of small TODOs, e.g. how do you know if a font
   is serif/sans-serif, or symbolic/non-symbolic?
* draw_markers, draw_line_collection, etc.
* use_tex

Perhaps now would be a good time for anyone interested to give the PDF
backend a spin around the block and tell me about any other bugs or
missing features, so when I next do a bout of backend_pdf hacking,
I'll know what people's priorities are.