[Qt-interest] Qt MVC Questions

[Pavel Koshevoy]

Faced with a similar problem I ended up writing a custom TreeView.  Although, my
view/model also supports non-standard layout of tree "rows" -- visible in some
columns, not visible in others, positioned/sized relative to parent frame (or
sibling frame) in the column where it's visible.  I had to do this to satisfy a
UI design that took liberties with a tree view (designer treated the second
column like a web page -- individual items not laid out as nested rows and have
no relation to sibling rows in columns 0 and 1).

Anyway, in my custom view I used a custom user role to query the model whether a
particular item was an "invisible" container in a particular column.

For question 2 -- I don't think you can get away from 1:1 mapping between Qt
view:model item mapping.  In my code I use the Qt model pretty much as a proxy
to the underlying Qt-independent model.  Some of my tree nodes present
themselves to Qt with several QModelIndexes, one for each aspect of the larger
object.  It's not pretty, but it's not awful either. The wrappers are pretty
thin.  Of course, this required a custom tree model as well.

Just so you know what this route could cost you -- my custom view weighs in at
about 3KLOC, and the custom model is about 2.5KLOC, not counting the non-Qt
model code.

	Pavel.


Willy P wrote:
> I have built a Model, a view and a delegate that represents a tree
> like data structure.
> 
> Two related questions:
> 
> 1)  Is there a way to hide TreeNodes in a view but show their
> children?  Basically I have data structures that are programatically
> useful but the user doesn't need to know about them.  So I'd like the
> view to show the invisible node's children as if they were children of
> the invisible node's parent.  I've tried setRowHidden() but it hides
> all the children as well.
> 
> 2)  The opposite question.  Is there a way to have nodes appear in the
> view but not the model?  I basically want to add categorical
> separators.  In some situations I want them and in others I don't, but
> in no case do I need them in the raw model.
> 
> Possible solution to #1, I could set a delegate for an "invisible" row
> and have it return a sizeHint of 0,0.  Seems like a hack but it may
> work.
> 
> Any other thoughts on these?
> 
> Thanks in advance...
> 
> -Willy
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