Reimplementing QFileSystemModel Checkboxes using QMap inconsistent results

JonB

different checkboxes get checked like random even if there's nothing random

QVariant QCheckableFileSystemModel::data(const QModelIndex &index, int role) const{
...
return checked;

I am not a C++er, so this is either very right or very wrong! Are you supposed to return an int for a QVariant? Because if not this could produce "random" state value for your checkboxes....

[EDIT: Looks like my suggestion was very wrong, sigh :( ]

mrjj

@JonB
Very good question, but i think it will return a QVariant constructed from the
int checked variable. Else compiler should be very unhappy if no automatic
conversion can happen.

moffa13

I am supposed to return a Qt::CheckState elem from enum which is int.

Yes the compiler constructs a QVariant from the int value.

So, any idea about what's going wrong here ?

moffa13

Any help please

mrjj

@moffa13
Add some qDebug() statement to see what index are sent and what it set pr index.
I think its one of those cases where debugger and tools are more useful than guessing looking at code.

moffa13

@mrjj said in Reimplementing QFileSystemModel Checkboxes using QMap inconsistent results:

@moffa13
Add some qDebug() statement to see what index are sent and what it set pr index.
I think its one of those cases where debugger and tools are more useful than guessing looking at code.

If it was that simple I wouldn't have asked.

qDebug is showing me correct paths before calling setData. The problem is that for whatever reason, some checkboxes won't get checked. I almost always get a different result whenever I run this code.

qDebug in setData tells me that the function receives Qt::Checked but it's not the case.

mrjj

@moffa13
Hi
Hmm, i would suspect the QSet<QPersistentModelIndex>
could contain incorrect indexes.
Im wondering if QFileSystemModel might invalidate QPersistentModelIndexes i have seen with QSqlTableModel.

moffa13

@mrjj It only has this behavior when I use QMap if I do this with QSet everything works fine. That's what I don't get

mrjj

@moffa13
Hmm. yes that is odd.
One difference with Set/QMap is if u ask QMap for non existing value
a default-constructed value is returned but you seem to check with contains so
should not happen?

moffa13

@mrjj

Yeah, exactly, for me it should work.

However I noticed something which may be useful. I added a QEventLoop when doing setData to look for the dataChanged signal but when I do this and I use qDebug to show the files returned by model::index, I get something like this :

Normal dir is
a.txt
b.txt
c.txt

filePath in the loop returns this :

a.txt
b.txt
b.txt

And c.txt does not get checked which is also odd.

mrjj

@moffa13
Hmm. you know how b.txt is included twice ?

moffa13

@mrjj this is absolutely not normal. It' a for loop iterating from 0 to rowCount(parent). Then it uses model->index(i, 0, parent). So this is not possible to output twice the same file.

mrjj

@moffa13
Could you try to do the same for loop from say a button and use
no localEvent loop or anything like that and see if its
reproducible in other context ?

moffa13

Ok I found what was causing this awful bug.

When I check if the map contains the index, I actually check the raw index not the QPersistantModelIndex so this is not the same object and I think qmap does not check equality using == operator .

So I have to iterate over the map and check using QPersistantModelIndex "==" operators which can compare from a QModelIndex.