Re: [win32gui] RE: [perl-win32-gui-hackers] -background option and windows

[Robert M. <rm...@po...>]

Jeremy White wrote:
>> (1) It appears that the '-background' option was never intended to 
>> work with  windows (Win32::GUI::Window, Win32::GUI::Dialog) and that 
>> the only way to change the background colour of a window is using the 
>> -class option with a coloured brush.   It might be possible to extend 
>> the WM_PAINT and/or WM_ERASEBKGND handlers to cope with this - is it 
>> work exploring?
> 
> I've just had a look at the Visual .Net environment and you can specify 
> the backcolor of a window (and the background image)

It would be possible to allow the -background option to take a 
Win32::GUI::Brush as a value.  This would allow bitmaps as patterns for 
the background;  but it would start to be very confusing for controls, 
where -background also specifies the text background colour.  I don't 
propose to do this - if you really want it use a class.

> The 
> problem with using a class to set the background is that you can't 
> change it during runtime.

I hadn't spotted this.

> Setting the background of a window does seem to crop up now and again - 
> and I've been stung with it several times - so a solution would be nice 
> - but how much work would be involved with the fiddling of 
> WM_PAINT/WM_ERASEBKGND? Is there a risk of it breaking other things? 
> Performance?

 From what I've seen I don't think it would be hard, but I would be 
concerned about regression testing, as I don't yet have enough 
experience in this area to be confident of understanding the behaviour 
of everything.

Performance - you'd only take a hit if you had the -background option 
set, and the background needs erasing anyway - it's just a question of 
whether Win32::GUI does it of it's done by DefWindowProc.

I'll have a look at implementing this.

BTW I've got the fix for class backgrounds not working in perl's 5.8 and 
higher.

Regards,
Rob.