Friday, March 13, 2009

OOP YaST GUI: event handling

OOP in YaST GUI: Event handling

Hello, here I am again ...

I played with idea of event handling, but if possible better way than we do in ycp now.
Also using inheritance: when you define some behavior, you can inherit class and override handling method or just use objects and handling will be done automatically (using composition).
So the basic idea is that event loop is done automatically and it executes handle function of object that is responsible for such event or which is listening.

Event loop is implemented in parent object (root object in hierarchy - CDialog). Because of this, all inherited objects (MainDialog, PopupDialog) will have this functionality automatically.

class CDialog:
def __init__(self):
self.factory = yui.YUI.widgetFactory()

def listen(self, newList):
self.listeners = newList
while etype!=5:
event = self.dialog.waitForEvent()
etype = event.eventType()
for item in self.listeners:
if (item.getInstance()==event.widget()): item.handle(event)

class CButton:
def __init__(self, factory, parent, label):
self.button = factory.createPushButton( parent, label )
def getInstance(self):
return self.button

self.pbAdd = CButton(self.f, hbox2, "&Add")
self.pbEdit = CButton(self.f, hbox2, "&Edit")
self.pbDel = CButton(self.f, hbox2, "&Delete")
d.listen([self.pbAdd, self.pbEdit, self.pbDel])

When you want to handle something (button click for example), you need to:
- define function that will executed
- connect function to the object
- start event loop with list of "listeners" (objects with connected functions)

There are 3 kinds of functons:
1 - function without any connection to object

self.pbAdd.handle = self.handleAdd

2 - function with connection just to object

self.pbAdd.handle = new.instancemethod(mujhandler, self.pbAdd, self.pbAdd.__class__)

3 - function with visibility outside of the object (example: function can see whole dialog)

self.pbAdd.handle = new.instancemethod(self.handleAdd.im_func, self.pbAdd, self.pbAdd.__class__)

Code is submitted into subversion

How to test this code:
- svn checkout
- make sure you have installed packages: python-yui, yast2-libyui, yast2-qt, yast2-ncurses
- run "./" to see Qt version, "unset DISPLAY;./" for ncurses version (unfortunately,in ncurses only way how to terminate application is to kill it, TODO)