Re: [Gtk2hs-users] [Gtk2hs-devel] instances of WindowClass

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

Adde,

On Jul 16, 2007, at 1:10, Adde wrote:

> Hi again.
> Speaking of segfaults, just got an exception
> ('gtk2hs_store_iter_n_children_impl: uncaught exception') for calling
> 'treeModelIterNChildren store Nothing' on an empty (no items)  
> TreeStore.
> The code runs if I add items to the store before showing the window.
> Any ideas?

Not really. Do you:

- use ListStore
   - if yes, which ghc version are you using?
- use TreeStore

Thanks,
Axel.

P.S.: please reply to the mailing list, so other people we can keep  
track of things (and so we people can google for problems).

> /Adde
>
> On Fri, 2007-07-13 at 15:41 +0100, Axel Simon wrote:
>> 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.
>>>>
>>>
>>
>