Hello,
I’ve had good luck so far with the wxWidgets/wxPython event handling framework. Most of the time I’m using it as intended and it’s really helpful compared to what I remember dealing with in Motiv during my previous run at GUI programming circa 1992. Custom events and their binding have been working just fine and doing what I intend.
In my current project, however, I need to send some command events in reverse. In other words I want a certain type of custom event to travel down the containment hierarchy rather than upward. Is there already a built-in ability to do this that I’m missing? Have others worked out a general way to do this?
In a way, one might think that asking for reverse event handling might perhaps be a sign of poor program organization or bad code factoring. I’ve definitely been examining that possibility, but my application is looking pretty clean from that perspective up until now.
Let’s say I have windows A, B, and C, with children A1, A2, and A3; B1…B3, etc… Let’s say each of these children have children A1a, A1b, A1c; B1a, B1b, B1c… etc.
Now some of these children happen to generate database inserts and, as a result of these inserts, some of the text fields (and, as it happens, TextCtrlAutoComplete controls) in children on another branch of this hierarchy need to re-query the database in order to present themselves in accordance with the UI i’m trying to present.
To be even more explicit, let’s say window B1c inserts data into a database table, and window A1a happens to depend on that table and is supposed to update its view whenever that table changes. So I can make B1c send a table-changed event, and that travels upward to B1, then assuming B1 skips it onward, it travels upward to B. But A and its children will never see that event since they’re downward in another branch of the containment hierarchy.
The way I’m handling this so far is that I do use a normal upward-propagating event to signal all the way up to A that one of its children changed a table (and event.GetValue() returns which table has changed, etc). Then I have a method on A that tells A1…A3 what’s happening, and they each have methods that tell their own children, and so on. Fortunately they are all instances of the same window subclass, so at least the code is reused and I didn’t have to copy that “tell the kids what I just heard” method in multiple places.
So I feel my current approach is messy, error-prone, and it’s not “real” signaling. I wish to straighten this out, and I suspect several persistent bugs in my updating and viewing code will thereafter become much easier to locate and fix. If there were an established way to propagate events downward, then rather than have A start telling its children to tell their children to…etc… I would just have A, upon receiving the upward-bound event from one of its branches, sent it downward along its other branches. Problem (potentially) solved, if that could be done.
Any advice greatly appreciated.
- Eric