Re: [matplotlib-devel] Backends status on transforms branch

[Michael D. <md...@st...>]

Christopher Barker wrote:
> Michael Droettboom wrote:
>> Wx supports polycurves in its new wxGraphicsContext API (but not the 
>> wxDC API that mpl uses now).  This means a fairly complete rewrite of 
>> the wx backend,
> 
> not necessarily. You can create a GraphicsContext from a wx.DC, you may 
> be able to just add that step for drawing polycurves.
>
>> since you 
>> can no longer draw to an in-memory buffer, but only a true wxClientDC). 
> 
> you can create a GraphicsContext from a wxMemeoryDC, so yes, you can 
> draw to a buffer.

I'm having trouble just getting a wxPython to compile with 
wxGraphicsContext support (perhaps another argument against using it...)

I was basing this determination on the wx documentation which clearly 
states one can only create a wxGraphicsContext from a wxWindowDC. 
wxMemoryDC inherits from wxDC, not wxWindowDC. I'd be certainly happy to 
find out that the documentation is incorrect on this point, as it would 
certainly make the implementation easier.

> I haev no idea what the impact on performance would be, but in general, 
> GraphicsContext is slower than DC.

Particularly, if it works as it appears to by rendering to a Cairo 
buffer first.

>> So, we need to look at the pros/cons of continuing to support these 
>> legacy APIs going forward.
> 
> yup. I know I never need a non-agg wx, but then I can see why folks 
> running remote X severs would want it.
> 
> I wonder if there is another way to speed that up with Agg -- can you 
> compress the bitmap data to pass it to the Xserver? is that happening 
> already?

You can compress the ssh connection over which X11 tunnels with the -C
commandline flag.  But whether that makes things faster or slower 
depends on the compressability of the data itself, and the relative 
speeds of the processor vs. network link, of course.

Cheers,
Mike

-- 
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA