On Oct 14, 2011, at 5:19 AM, Chris G wrote:
> self.bindEvent(dabo.dEvents.Hit, self.handleHit) - I can't get my
> mind round "but in Dabo we've simplified it so that these actions
> all raise the Hit event". Surely different events need to do
> different things don't they? You can't have every event for a
> control (ButtonRightClick, ButtonLeftClick, KeyDown, etc.) calling
> the same callback method can you? Or does one have a switch/case
> statement in the callback to see what caused the event?
Sorry if that isn't clear. What was meant was that the *primary* event
from a user interacting with a control will raise the Hit event. So for a text
box, the Hit event is raised when text is entered; for a menu item, the Hit
event is raised when the menu is selected; for a button, the Hit event is
raised when it is clicked; for a timer, the Hit event is raised when the timer
fires.
For all other events, the different events are raised, and yes, you
need to code for their handlers separately. The advantage of the Hit event is
that 90% of the time when you want to handle an interaction with a control,
that's the one that you'll need.
> Later it says "Event handlers need to be written to accept a single
> event object parameter. This event object will have an attribute
> named 'EventData' that will contain relevant information about the
> event. For example, mouse events will include the x and y coordinate
> of the mouse, whether any modifier keys were pressed at the time,
> and, if relevant, mouse scroll wheel information. Keyboard events
> will contain the value of the key that was pressed, and also any
> modifier keys. Menu events will contain the menu prompt of the
> selected menu; tree events will contain info about the selected
> node; grid events will contain row/column values. " but my event
> handler needed two parameters:
> def handleKey(self, p2):
> Presumably my p2 parameter is the event object parameter, however I
> can't find documentation that describes that.
Yes, it would be. In much the same way that Python will automatically
supply an instance reference as the first parameter when an instance method is
called, Dabo will supply an event object parameter to handlers as the second.
> All I can
> find is lots of places that say "...which will exist in the
> event.EventData dictionary property" so I know that EventData is a
> dictionary but I can't really find out anything more about 'event'
> nor what keys to use to get data out of EventData.
One way to do this is to write something like this as your first pass
at an event handler:
def onSomeEvent(self, evt):
print evt.EventData
That will show what's available; it will change depending on the
control and the event (e.g., it wouldn't make sense for a keypress event to
have mouseX/mouseY info).
> KeyDown (and other keyboard) events - from what my code does it
> seems that there is already a key handler which deals with some keys
> (i.e. data entry into a field, all non-control keys simply get
> entered as data) and it's only keys that *aren't* handled already
> that get passed on to my key handler.
Actually that's not correct. Every keypress will raise an event; for
controls such as a textbox, there is a default behavior that is built into the
control: add the character at the current insertion point, for example. If you
have a handler for the KeyChar event, you can prevent the default behavior by
adding the line:
evt.stop()
to the code.
> This is OK but is it
> documented somewhere? One *might* want to do something special with
> some non-control keys, e.g. switch all to lower case or use some
> upper case letters to do something special, how would one do this?
Here's one that will prevent the letters x, y and z from being entered
into a textbox:
def myHandler(self, evt):
char = evt.EventData.keyChar.lower()
if char in ("x", "y", "z"):
evt.stop()
If you want to ensure that the characters in a textbox are all upper or
lower case, Dabo already has a property named 'ForceCase' that you can set to
"lower", "upper", or "title", and as you type, the content of the textbox will
be adjusted after each keypress.
> Sorry for all the questions and thank you all very much for the help so
> far. I'll do my best to be constructive and I'm very willing to try and
> help improve the documentation. I'm sure much of my problem is (as I
> know I tend to) trying to run before I can walk! :-)
Don't apologize for asking questions - that's exactly what this list is
for!
-- Ed Leafe
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