[wxPython-users] identify/track an item in a TreeCtrl

[Robin Dunn]

Andrea Gavana wrote:
> Hi Harry,
> 
> On Dec 3, 2007 10:59 AM, Pan Xingzhi wrote:
>>     Is there a way to identify/track an item in a TreeCtrl? This action
>> typically takes place in an event handler where the exact "source" of the
>> event is needed.
>>     I tried event.GetItem(), but the returned TreeItemId instance is not the
>> one returned by AppendItem. However their m_pItem property looks the same.
>> Can I use that?
>>     I read the source code in the wxPython demo. It just retrieves the text
>> of the item using GetItemText(event.GetItem()). Though the TreeItemId
>> instance is changed, we can still get the same information (text, color...)
>> of the item. There must be some magic behind scene but I'm just confused.
> 
> The TreeItemId generated by the C++ wxWidgets code is an
> evanescent/ghostly entity which may or may not change depending on
> what you do with the TreeCtrl.


Correct.  Essentially, the wx.TreeItemId class is intended as just a 
temporary handle for the item, which is created and destroyed as needed. 
  You can hold on to TreeItemId instances and use them later, but as 
you've seen a new instance is created whenever a new item is returned 
from wx.


> Using event.GetItem() will almost
> surely not returns the same TreeItemId as AppendItem. 

It *never* will.  A new handle will always be created for the GetItem 
return value.

> Depending on
> which are your needs, you might only use the item returned by
> event.GetItem(), or store some particular identifier into the item
> PyData (using SetPyData/GetPyData), 

That is what I would suggest.


> or maybe use the m_pIten property
> (but I never used it and I don't even know what it's for).

Although it is public, personally I would just consider it an 
implementation detail and would shy away from using it like this.  The 
C++ usage of it may not be very likely to change, but the way that SWIG 
is creating access wrappers to that type of value may.


-- 
Robin Dunn
Software Craftsman
http://wxPython.org  Java give you jitters?  Relax with wxPython!