Re: [PyQt] Re: problem with QAbstractItemModel
Vicent Mas escribió:
On 2009-11-06 Baz Walter said:
...
your implementation of QAbstractItemModel.index is going to get called
*a lot* and in many unforseen ways.
Yes, but it is a general fact, not something that happens to my particular
implementation, right?
i think a more sane implementation
would be something like this:
def index(self, row, column, parent):
if self.hasIndex(row, column, parent):
branch = self.nodeFromIndex(parent)
return self.createIndex(row, column, branch.childAtRow(row))
return QModelIndex()
this fixes your immediate bug, and will probably avoid many others.
I know that my implementation is very rough, but it is intended just for
testing purposes. Of course your workaround and other similar (like the one
sent by Linos) fixes the problem, but they leave the main question unanswered:
why wrong row values are passed to the index method? Is it expected? If it is
developers are forced to include good sanity code in their index method
implementation (as you and Linos did), but I've not seen any reference to this
in the Qt documentation. IMHO the Qt model implementation should not allow
wrong row values to be passed to the index method. In fact, the example in the
'Editable Tree Model Example' section of the Qt documentation doesn't check at
all the validity of the row argument passed to the index method
implementation.
On the other hand the fact that my script works fine with some Qt/PyQt versions
but fails with recent versions seems to indicate that there is a bug either in
the Qt implemention of models or in that PyQt versions.
Vicent
PS: Baz, thanks for your code snippet
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Hi,
in the qt examples from qt 4.5 documentation you can see they use this in the
model:
http://doc.trolltech.com/4.5/itemviews-simpletreemodel-treemodel-cpp.html
QModelIndex TreeModel::index(int row, int column, const QModelIndex &parent)
const
{
if (!hasIndex(row, column, parent))
return QModelIndex();
TreeItem *parentItem;
if (!parent.isValid())
parentItem = rootItem;
else
parentItem = static_cast(parent.internalPointer());
TreeItem *childItem = parentItem->child(row);
if (childItem)
return createIndex(row, column, childItem);
else
return QModelIndex();
}
and this in the item class.
http://doc.trolltech.com/4.5/itemviews-simpletreemodel-treeitem-cpp.html
TreeItem *TreeItem::child(int row)
{
return childItems.value(row);
}
but they can do this because QList .value method dont get an error if it is out
of bounds.
http://doc.trolltech.com/4.5/qlist.html#value
T QList::value ( int i ) const
Returns the value at index position i in the list.
If the index i is out of bounds, the function returns a default-constructed
value. If you are certain that the index is going to be within bounds, you can
use at() instead, which is slightly faster.
I am using this same strategy but like i am using python list i check before if
i can return the children, you can use a "try except" too.
Regards,
Miguel Angel.
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Re: [PyQt] Re: problem with QAbstractItemModel
On 2009-11-07 Linos said:
> ...
> Hi,
> in the qt examples from qt 4.5 documentation you can see they use this
> in
> the model:
> http://doc.trolltech.com/4.5/itemviews-simpletreemodel-treemodel-cpp.html
>
> QModelIndex TreeModel::index(int row, int column, const QModelIndex
> &parent) const
> {
> if (!hasIndex(row, column, parent))
> return QModelIndex();
>
> TreeItem *parentItem;
>
> if (!parent.isValid())
> parentItem = rootItem;
> else
> parentItem = static_cast(parent.internalPointer());
>
> TreeItem *childItem = parentItem->child(row);
> if (childItem)
> return createIndex(row, column, childItem);
> else
> return QModelIndex();
> }
>
Thanks for this info. I simply didn't check this page because I was interested
in editable models not in read-only models. Its funny to see that index method
implementation in the read-only example is more complex than in the editable
one.
But still, it is nearly the same workaround provided by Baz and doesn't answer
my question about validity of the passed row argument.
> and this in the item class.
> http://doc.trolltech.com/4.5/itemviews-simpletreemodel-treeitem-cpp.html
>
> TreeItem *TreeItem::child(int row)
> {
> return childItems.value(row);
> }
>
> but they can do this because QList .value method dont get an error if it is
> out of bounds.
Yes but, as you can see in the in the index method provided in that example,
this is called *after* the row argument has been validated so it has no impact
in my question.
Vicent
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Re: [PyQt] Re: problem with QAbstractItemModel
On 2009-11-07 Vicent Mas said:
> On 2009-11-07 Linos said:
> > ...
> > Hi,
> > in the qt examples from qt 4.5 documentation you can see they use this
> > in the model:
> > http://doc.trolltech.com/4.5/itemviews-simpletreemodel-treemodel-cpp.html
> >
> > QModelIndex TreeModel::index(int row, int column, const QModelIndex
> > &parent) const
> > {
> > if (!hasIndex(row, column, parent))
> > return QModelIndex();
> >
> > TreeItem *parentItem;
> >
> > if (!parent.isValid())
> > parentItem = rootItem;
> > else
> > parentItem = static_cast(parent.internalPointer());
> >
> > TreeItem *childItem = parentItem->child(row);
> > if (childItem)
> > return createIndex(row, column, childItem);
> > else
> > return QModelIndex();
> > }
>
> Thanks for this info. I simply didn't check this page because I was
> interested in editable models not in read-only models. Its funny to see
> that index method implementation in the read-only example is more complex
> than in the editable one.
>
> But still, it is nearly the same workaround provided by Baz and doesn't
> answer my question about validity of the passed row argument.
>
> > and this in the item class.
> > http://doc.trolltech.com/4.5/itemviews-simpletreemodel-treeitem-cpp.html
> >
> > TreeItem *TreeItem::child(int row)
> > {
> > return childItems.value(row);
> > }
> >
> > but they can do this because QList .value method dont get an error if it
> > is out of bounds.
>
> Yes but, as you can see in the in the index method provided in that
> example, this is called *after* the row argument has been validated so it
> has no impact in my question.
>
OK, finally I got it. The validity of the parent model index passed to the
QAbstractItemModel *must* be checked. It is said explicitely in the page
referenced by Linos:
Models must implement an index() function to provide indexes for views and
delegates to use when accessing data. Indexes are created for other components
when they are referenced by their row and column numbers, and their parent
model index. If an invalid model index is specified as the parent, it is up to
the model to return an index that corresponds to a top-level item in the
model.
Checking the parent validity in the way suggested by Balz will check
implicitely the row and column validity.
As I said I did read the "Editable tree model example" which doesn't do that
checking (I don't know why) but not the "Simple tree model example" (which
does exactly that checking) so I was puzzled.
THANKS guys for your help.
Vicent
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RE: [PyQt] cleaning up after removing items from layout
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