[IronPython] Subclassing a Control

[Michael Foord]

Dino Viehland wrote:
> CreateParams is a property, so you'll need to construct a property to do this:
> 
> class TransLabel(Label):
>         def get_CreateParams(self):
>                 cp = super(TransLabel, self).CreateParams
>                 cp.ExStyle = cp.ExStyle | 20
>                 return cp
>         CreateParams = property(fget=get_CreateParams)
> 
> Unfortunately it looks like we don't get the correct dispatch to the base-class property in the super case here.  Instead we stack overflow.  A work around could be to either create CreateParams yourself, or get it from another label.
> 
> class TransLabel(Label):
>     def get_CreateParams(self):
>         cp = Label().CreateParams
>         cp.ExStyle = cp.ExStyle | 20
>         return cp
>     CreateParams = property(fget=get_CreateParams)
> 

The following syntax is equivalent and looks nicer :-p

class TransLabel(Label):

    @property
    def CreateParams(self):
        cp = Label().CreateParams
        cp.ExStyle = cp.ExStyle | 20
        return cp

(or at least it should be.)

Fuzzyman
http://www.voidspace.org.uk/python/index.shtml

> 
> 
> 
> -----Original Message-----
> From: users-bounces at lists.ironpython.com [mailto:users-bounces at lists.ironpython.com] On Behalf Of Davy Mitchell
> Sent: Monday, November 27, 2006 2:11 PM
> To: users at lists.ironpython.com
> Subject: [IronPython] Subclassing a Control
> 
> Hi Folks,
> 
> I was doing some IronPython for the first time in ages so forgive me
> if I am being dumb :-)
> 
> Anyway I am trying to make a transparent label WinForm control:
> 
> class TransLabel(Label):
> 
>     def CreateParams(self):
>         cp = super(TransLabel,self).CreateParams
>         cp.ExStyle = cp.ExStyle | 0x20
>         return cp
> 
>     def OnPaintBackground(self,e):
>         pass
> 
> The problem is the super call fails with:
> Traceback (most recent call last):
>   File K:\MyDev\PyLP\helloWorld1.py, line 69, in Initialize
>   File K:\MyDev\PyLP\helloWorld1.py, line 22, in __init__
>   File , line 0, in DefaultNew##12
>   File , line 0, in .ctor##26
>   File System.Windows.Forms, line unknown, in .ctor
>   File System.Windows.Forms, line unknown, in .ctor
> TypeError: issubclass: arg 1 must be a class
> 
> line22 is only self.label = TransLabel()
> 
> Thanks and take care,
> Davy Mitchell
> 
> --
> Davy Mitchell
> Blog - http://www.latedecember.com/sites/personal/davy/
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