pygtk2 and its numpy dependency

[Jon Ciesla]

Adam Jackson wrote:
> On Tue, 2009-08-11 at 07:12 -0500, Jon Ciesla wrote:
>   
>> Adam Jackson wrote:
>>     
>>> On Mon, 2009-08-10 at 14:40 -0500, Jon Ciesla wrote:
>>>       
>>>> Since pygtk2 does actually use numpy, isn't d) the best (albeit most 
>>>> annoying) option?
>>>>         
>>> Internally?  Or just to implement that one entrypoint?  I believe it to
>>> be the latter.
>>>       
>
> Having double-checked: it's just to implement get_pixels_array().
>
>   
>> I'm not sure, but what practical difference would that make?
>>     
>
> Well, it's a soft dep...
>
> If built with numpy support, get_pixels_array() starts off with:
>
>     if (!have_numpy())
>         return NULL;
>
> The important bit of have_numpy() looks like:
>
>     static int import_done = 0;
>     if (!import_done()) {
>         import_done = 1;
>         import_array1(1);
>         if (PyErr_Occurred()) {
>             /* throw */
>         }
>     }
>
> import_array1() is a small wrapper around _import_array(), which starts
> off with:
>
>     PyObject *numpy = PyImport_ImportModule("numpy.core.multiarray");
>     if (numpy == NULL) return -1;
>
> And it turns out this is all static inlines that get built straight into
> pygtk2 itself.  In other words, if this bit of pygtk2 were written in
> python, it'd look like:
>
> class gdk:
>     def get_pixels_array(self):
>         import numpy.core.multiarray
>         # do a bunch of stuff
>
> and if that python module weren't available it'd just throw an
> exception.
>
> So: python apps that call get_pixels_array() can Requires: numpy
> themselves, and then that entrypoint will work.  Python apps that
> _don't_, need not, and then numpy and its deps go missing, but it
> doesn't matter because you never call get_pixels_array() so the
> exception never happens.
>
> So I think my b) suggestion (of replicating the ABI in pygtk2) is
> actually redundant, it's what's already happening.  pygtk2 already knows
> the object layout of numpy arrays thanks to #includes of doom, it just
> doesn't try to create them unless the rest of the numpy exists.
>
> The question is only whether to keep the 'Requires: numpy' in pygtk2 or
> to push it out to apps that use get_pixels_array().  And I think the
> latter sounds just fine to me.
>
> - ajax
>   
That's fine with me, assuming there's a way to determine that list.

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