Re: Curious: TreeCtrl.GetNextVisible() vs CustomTreeCtrl.GetNextVisible()

Hi,

On Wed, 28 Jun 2023 at 20.31, [email protected] <[email protected]>
wrote:

> The docs for both are clear and correct:
>
> TreeCtrl:
> GetNextVisible(*self*, *item*)
> <#m_-7195478226309837869_wx.TreeCtrl.GetNextVisible>
>
> Returns the next visible item *or an invalid item* if this item is the
> last visible one.
>
> -----------
>
> CustomTreeCtrl
>
> GetNextVisible(*self*, *item*)
> <#m_-7195478226309837869_wx.lib.agw.customtreectrl.CustomTreeCtrl.GetNextVisible>
>
> Returns the next visible item.
>
> An instance of GenericTreeItem
> <http://wx.lib.agw.customtreectrl.GenericTreeItem.html#wx.lib.agw.customtreectrl.GenericTreeItem>
>  *or None* if there are no next visible items.
>
>
> Migrating code from TreeCtrl to a CustomTreeCtrl -- it's so close to a
> drop-in replacement but this tripped me up: was expecting an invalid tree
> item but got an unexpected None. Why the difference? Couldn't the Python
> CustomTreeCtrl code just as easily have returned a nascent GenericTreeItem,
> analogous to what the treectlg.cpp wxWidgets code does for the TreeCtrl ?
>
> Again, not a bug, and the difference is easily worked around -- but why
> the difference? Why *not* try to keep the same behavior?
>
> -ck
>

CustomTreeCtrl was written 17 years ago, and at that time generating an
“invalid” GenericTreeItem (and thus instantiating a whole class) just for
its IsOk() method to return False seemed a very wasteful approach to me.

17 years later I haven’t changed my opinion.

It’s a phenomenal waste of cycles - at least in Python - and returning None
is a cheap alternative.

That said, it would probably take about 10 minutes to subclass and
monkey-patch GenericTreeItem to make it do what you want.

Andrea.




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