Re: [Gtk2hs-devel] instances of WindowClass

[Axel S. <A....@ke...>]

On Jul 13, 2007, at 15:28, Adde wrote:

> Ok, thanks!
> I'll just have to use my own function (myWindowShow) for now.
>
> The reason I tried is that I couldn't find anything in the WindowClass
> documentation about these tricks. Making something an instance of
> WindowClass works, but as you said, there are no methods to implement
> and it segfaults when you try to use your data as a Window.

Hm, maybe we need to do something so that we don't actually export  
the classes. One key feature Gtk2Hs should have is that you cannot  
make it segfault.

> Do you mind if I sneak by another question while we're at it?
> I'm trying to iterate through a TreeStore while modifying the  
> objects it
> contains. The ModelView documentation says I should use
> TreeRowReferences but I can't figure out how to call
> treeRowReferenceNew. It wants a NativeTreePath and all I've got is
> regular TreePaths (via treeModelGetPath).
> I got it to work by saving the TreePaths instead but as I  
> understand it
> they can't be used after inserting / deleting.

Ops. I guess that's unfinished. Which reminds me that I should push  
the changes that I have in my local repository. I can probably fix  
the row reference thing.

TreePaths are simple lists of integers. The problem is that if you  
have a reference like [0,1,2] and you insert a node at the same  
location, the previous node now will have the index [0,1,3]. In  
contrast, RowReferences continue to point to that row, no matter how  
many nodes are inserted or deleted.

> Thanks for a great library, I had almost given up hope on using  
> Haskell
> for serious desktop development.
>

I hope we iron out anything that stands in the way of good GUI  
programs written in Haskell!

Axel.
> On Fri, 2007-07-13 at 10:55 +0100, Axel Simon wrote:
>> Hi Adde,
>>
>> On Jul 12, 2007, at 21:54, Adde wrote:
>>
>>> Hi.
>>> I have a structure representing a special kind of window which among
>>> other things holds a Gtk Window.
>>>
>>> data MyWindow = data MyWindow {window :: Window, ...}
>>>
>>> Is there any way to make it behave like an ordinary Window so I can
>>> call
>>> windowPresent etc. on it? I tried making it an instance of  
>>> WindowClass
>>> hoping to be able to just override toWindow, but no luck.
>>
>> Duncan has pulled some nifty performance tricks such that the
>> WindowClass and friends are all empty. Hence, there is actually no
>> method you can override and everything is simply coerced. This
>> prevents you from creating a new piece of data and making it an
>> instance of WindowClass, I'm afraid.
>>
>> If you think your code would become much cleaner by keeping program
>> data with a window (or any other object) you could use the function
>> in System.Glib.GObject, look for "User-Defined Attributes". This may
>> still involve passing around the attribute in addition to the window,
>> though.
>>
>> Hope this helps,
>> Axel.
>>
>