CheckBoxTreeItem behavior

[John Hendrikx]

On 18/11/2022 00:10, Nir Lisker wrote:
> Hi,
>
> I have been working on fixing some issues with the behavior 
> of CheckBoxTreeItem. I stumbled across this situation:
>
> When a parent is de/selected, all of its children are set to the same 
> state. However, a CheckBoxTreeItem can be set to indeterminate 
> programmatically (the control itself does not allow indeterminate). 
> Should all children also be set to an indeterminate state? If so, this 
> will put the tree at an "invalid" state where leaf nodes can be 
> indeterminate as well. OTOH, if not, then we are again at an invalid 
> state if all children have the same state, but the parent doesn't.

I think the indeterminate state is best left up completely to the owner 
of the control. You may need information that is not part of the tree to 
actually determine if something is indeterminate or not.  A tree may be 
filtered, or a tree may represent only "nodes" while "leaves" are 
displayed in a 2nd control as a list.  This means that in theory, parent 
nodes could be indeterminate even if all its children are in the same 
state (checked/unchecked) due to filtering, and leaf nodes could be 
indeterminate if they represent a directory while the file selection is 
displayed in a separate control.  In Backup software, a directory may be 
partially selected if it has a filter associated with it (like *.java) 
even if that directory is empty or has only Java files currently...

Some UI's will even allow you to click on an indeterminate parent node 
to check it (checking all children), click again to uncheck it 
(unchecked all children), and click a 3rd time to put it back to an 
indeterminate state (restoring all children to the state they had before 
the first click).

--John