On 10/23/2010 06:05 PM, David Carmean wrote: > As I blurted on -users, I'm thinking lately about callbacks in the > non-GUI portions of the libraries--mostly Artist and subclasses. > I'm curious if anybody else has been thinking about them? > > Ideally, I'd like to see the following: > > All of the Artist subclasses, and anything else that might belong to > a Figure, would be updated to use/add cbook.CallbackRegistry callbacks > (weakref = good thing). > > In addition to emulating/replacing the simplistic 'pchanged' callback > with a signal of that same name, there would be a signal named after each > setter method, and said methods fire off their eponymous signal after they > modify the property. > > There should be some way to rate-limit or temporarily block individual > signals or callback connections. > > The various constructors, etc, would be modified to "subscribe" to > the 'pchanged' signal of all children, such that even if a particular > object in the "middle" of a figure heirarchy does nothing with the > signal, a sort of a global 'pchanged' signal propagates up to the top > object (FigureManager, Canvas, Figure, something). > > My current Use Case for these features is in experimenting with different > Artist styles (Text styles/fonts, marker styles/sizes, etc), and I'm tired > of calling canvas.draw() all the time :) But also, I'm working on a > GUI to do the same (traits UI), and want to tie both layers of the model > together with callbacks to speed up the experimenting. > > I've spent a few hours this weekend doing some meta-monkey-patching-- > using __getattribute__ to decorate the setters on-the-fly to invoke > callbacks.process(*args) after the changes. I have a few more quick > hacks to try before I'm ready to decide on a production-ready strategy. It's great to see someone working on this. Similar ideas have been thrown around since at least as long as I "joined the party" in 2007 (search the e-mail archives for "Traits"). I like your approach because it should allow for a tighter integration of Traits, while at the same time not adding Traits as a dependency. It just might be the elusive middle ground that prevented us from really going forward way back when. Mike