[Matplotlib-users] Cocoa backend for embedding in Cocoa application

[Barry W. <bar...@gm...>]

I've written the start of a Cocoa-native backend for matplotlib and
would like to submit feedback on the code and on the possibility of
including it in the standard matplotlib distribution. The backend
implementation is not complete (image rendering and mathtext rendering
are currently no implemented, nor are the print_* methods of the
FigureCanvas). Image rendering is trivial once I figure out how to get
the pixel data out of a matplotlib image (I just haven't investigated
the API yet). The print_* methods are also trivial (see point 1
below). I'm not sure how to handle mathtext yet. This backend has two
major feature differences from CocoaAgg:

1. All drawing is done via native Quartz drawing calls. This has the
advantage of making all of the native rendering functionality
(including native font rendering and output formats (all those
supported by Cocoa-eps,pdf,tiff,etc.) available to matplotlib. It has
the disadvantage that the translation from matplotlib paths to Cocoa
NSBezierPaths is done in python and is much slower than the compiled
version of this operation in the Agg backend (this is a solvable
problem, of course).

2. The reason I wrote the backend was so that matplotlib could be used
seemlesslly from within a Cocoa application. Thus this backend *will
not work* without an existing NSRunLoop. It won't work from the
terminal or an IPython session. It will work from the in-progress
Cocoa frontend for IPython or from any other Cocoa application. Again
there are tradeoffs. On the positive side, figure windows are treated
like any other application window, selectable from the Window menu
etc. and matplotlib becomes a seemless part of the application.
Existing backends designed to create their own runloop (e.g. CocoaAgg
or TkAgg) cause menubar and run loop problems when used from within an
existing application. It would be possible to merge the CocoaAgg and
Cocoa backends in this regard to use the existing run loop if present.

I've attached the backend_cocoa.py.

cheers,
Barry