Clickable Reports UI
Status: some information gathered, need input from someone more experienced :).
The graphical reports are nice, but they used to be clickable. It would be nice to make more stuff clickable again :)
The engine used for the graphs is "GnomeOffice Graph" (GOG for short, in libgoffice). It is mainly shared by Gnumeric and GnuCash, which both seem to keep copies of the tree in their own respective trees. So if changes need to be made there, we must make sure we submit them to upstream (wherever that is).
Handling piechart clicks is also done on the second page of the Graph "guru". Code for this can be found in goffice/graph/gog-guru.c, more specifically in the graph_guru_set_page and cb_canvas_select_item functions. This draws the piechart on a FooCanvas which supports button_press_event signals. GogPiePlot objects themselves don't support this signal, so we need to add the callback after rendering it to a pixmap.
When I connect the button_press_event signal to the widget in addPixbufGraphWidget like this:
g_signal_connect (G_OBJECT (widget), "button_press_event", G_CALLBACK (cb_graph_clicked), NULL);
I no longer get a "signal 'button_press_event' is invalid for instance" error at run-time, but the handler doesn't appear to be called either.