[Qt-interest] QAbstractItemModel, tree structure and dynamic datas

[Tanguy Krotoff]

Hello

I can easily make my QAbstractItemModel be updated with new datas
dynamically when QAbstractItemModel is a simple list.

But I have some hard time to get this done with a tree structure like this one:
+ item1
    - item11
    - item12
(screenshot: http://www.ldc.usb.ve/docs/qt/images/windowsxp-treeview.png )

Here what I would like to achieve:
The user clicks on the "+" in front of item1:
  - In another thread is done some computation
  - When the computation is done, a signal computationDone(result) is sent
  - The child items of item1 are getting added

To sum up, I would like to populate an item with its childs
dynamically using a different thread. Why? I want a responsive GUI and
the internal tree structure can be very big


Here what I have understood from the documentation, examples and mails
from this mailing-list:
- The "+" in front of item1 is showed when hasChildren() returns true
- When the user clicks on the "+", method canFetchMore() is being
called. If true is returned, it will call method fetchMore()

Here what I would like to implement inside my
QAbstractItemModel::fetchMore() method:

fetchMore(const QModelIndex & parent) {
	computeInAnotherThread(parent);
	//emits signal computationDone()
}

//Catches signal compuationDone()
slotComputationDoneFromOtherThread(const QStringList & childs) {
	beginInsertRows(parent, first, last);
	foreach (QString child, childs) {
		//Change my internal tree data structure
	}
	endInsertRows();
}

Is it the right way to do it? Am I wrong about the use of
canFetchMore() and fetchMore()? Is there some examples/projects around
using QAbstractItemModel this way?

-- 
Tanguy Krotoff <tkrotoff at gmail.com>
+33 6 68 42 70 24