The gnome-canvas looks like a good candidate for developing a simple
viewer for printed circuit board graphics. The Python API is missing
two important methods. It is possible to translate groups and nested
groups, but it is not possible to scale or to rotate the groups. The
code in the definitions file that is suppose to generate a scale and
rotate funtion were commented out. The underlying gnome code
had defined functions for rotate and scale, but they were not
implemented. The gnome-canvas authors sent the following response to
a query about what will be done with this code and what should be used
to rotate and scale objects:
Raph Levien writes:
> Michael McLay wrote:
> >
> > In gnome-canvas.h gnome_canvas_item_rotate and gnome_canvas_item_scale
> > are defined, but they are not implemented. It looks like the required
> > art_affine_scale and art_affine_rotate functions have been defined in
> > art_affine.c. Will they be implemented in a future release or is this
> > a deprecated feature?
> >
> > This is a key feature of the canvas which I need for my application.
>
> You want to do a gnome_canvas_item_affine_relative (or maybe absolute,
> depending on what you're trying to do), using the appropriate art_affine
> functions to generate the affine transform.
>
> The g_c_i_rotate and _scale methods shouldn't be in the .h file.
> Federico is planning to clean that stuff up soon.
>
> Good luck with your canvas app!
>
> Raph
It looks like it won't be possible to simply generate a wrapper for an
existing library call. Some additional code will be required to
implement the rotate and scale functions. Or, perhaps the affine
functions should be exposed in the Python API.
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