Maintaining checkedstatus inheritance in a QTreeView - c++

Question

I'm trying to do something basic : you have a QTreeView. 1st depth are folders only, 2nd depth are files only. I want to have a check box with the checked status next to each item. Files are either checked or unchecked, folders can also be partiallyChecked depending on their files; all in all quite natural I believe.
The way I though I should go was using a QStandardItemModel and populate it with a custom subclass of QStandardItem : DescriptionFileItem. Maybe that was a bad idea, if there's an easier way please enlight me.
I tried using signals and slots so that my signal CheckStateChanged on a file would be connected to a slot UpdateCheckedStateOnChildStateChanged on its containing folder. This required my DescriptionFileItem to inherit from QObject as well (BTW, I was surprised that QStandardItem did not inherit from QObject). I initially hoped this would work seamlessly with the provided base classes but it did not : emitDataChanged() didn't seem to trigger my model's dataChanged() signal...
Using the model's dataChanged signals directly didn't work either: it's call is protected so you can't use it without subclassing (I think that's my next move unless somebody can help me get it right).
At the moment I have a signal -> slot connection that won't work and I have no idea why; compile and link work ok. Here's the code; perhapps you'll spot my mistakes easily. I'm leaving some commented lines so you can maybe see what I did wrong in a previous attempt. Thanks for your input!
#ifndef DESCRIPTIONFILEITEM_H
#define DESCRIPTIONFILEITEM_H
#include <QStandardItem>
#include <Qt>
class DescriptionFileItem : public QObject, public QStandardItem
{
Q_OBJECT
public:
explicit DescriptionFileItem(const QString & text, bool isFileName=false, QObject* parent = 0);
void setData ( const QVariant & value, int role = Qt::UserRole + 1 );
QVariant data( int role = Qt::UserRole + 1 ) const;
QString text;
Qt::CheckState checkedState;
bool isFileName;
signals:
void CheckStateChanged();
public slots:
void UpdateCheckedStateOnChildStateChanged();
};
#endif // DESCRIPTIONFILEITEM_H
Corresponding .cpp :
#include "DescriptionFileItem.h"
DescriptionFileItem::DescriptionFileItem(const QString & text, bool isFileName, QObject* parent):
QObject(parent),QStandardItem(text)
{
this->isFileName = isFileName;
checkedState = Qt::Checked;
}
void DescriptionFileItem::setData ( const QVariant & value, int role){
if(role == Qt::CheckStateRole){
Qt::CheckState newCheckState = (Qt::CheckState)value.toInt();
checkedState = newCheckState;
if(isFileName){
if(newCheckState == Qt::Unchecked || newCheckState == Qt::Checked){
for(int i = 0; i<rowCount(); i++){
DescriptionFileItem* child = (DescriptionFileItem*)QStandardItem::child(i);
QModelIndex childIndex = child->index();
child->model()->setData(childIndex,newCheckState, Qt::CheckStateRole);
//child->setCheckState(newCheckState);
//child->setData(newCheckState,Qt::CheckStateRole);
}
/*if(rowCount()>1){
emit this->model()->dataChanged(this->child(0)->index(),this->child(rowCount()-1)->index());
}else{
emit this->model()->dataChanged(this->child(0)->index(),this->child(0)->index());
}*/
}
}else{
emit CheckStateChanged();
}
//emit this->model()->dataChanged(this->index(),this->index());
}else{
QStandardItem::setData(value,role);
}
}
QVariant DescriptionFileItem::data( int role ) const{
if (role == Qt::CheckStateRole){
return checkedState;
}
return QStandardItem::data(role);
}
void DescriptionFileItem::UpdateCheckedStateOnChildStateChanged()
{
Qt::CheckState min = Qt::Checked;
Qt::CheckState max = Qt::Unchecked;
Qt::CheckState childState;
for(int i = 0; i<rowCount(); i++){
DescriptionFileItem* child = (DescriptionFileItem*)QStandardItem::child(i);
childState = (Qt::CheckState) child->data(Qt::CheckStateRole).toInt();
min = min>childState ? childState: min;
max = max<childState ? childState: max;
}
if(min >= max)
setData(min, Qt::CheckStateRole);
else
setData(Qt::PartiallyChecked, Qt::CheckStateRole);
}
And the construction of the connection / tree:
DescriptionFileItem* descFileStdItem = new DescriptionFileItem(descriptionFileName, true);
descFileStdItem->setFlags(Qt::ItemIsSelectable|Qt::ItemIsUserCheckable|Qt::ItemIsEnabled|Qt::ItemIsTristate);
descriptionFileSIModel.appendRow(descFileStdItem);
typedef pair<string,int> indexType;
foreach(indexType index,dataFile->indexes){
DescriptionFileItem* key_xItem = new DescriptionFileItem(index.first.c_str());
descFileStdItem->appendRow(key_xItem);
key_xItem->setFlags(Qt::ItemIsSelectable|Qt::ItemIsUserCheckable|Qt::ItemIsEnabled);
QObject::connect(key_xItem,SIGNAL(CheckStateChanged()),descFileStdItem,SLOT(UpdateCheckedStateOnModelDataChanged()));
}
EDIT: final answer, thanks to stu (see below)
void DataLoadWidget::ModelItemChanged(QStandardItem *item)
{
QStandardItem* parent = item->parent();
if(parent == 0){
//folder state changed--> update children if not partially selected
Qt::CheckState newState = item->checkState();
if(newState != Qt::PartiallyChecked){
for (int i = 0; i < item->rowCount(); i++)
{
item->child(i)->setCheckState(newState);
}
}
}
else{//child item changed--> count parent's children that are checked
int checkCount = 0;
for (int i = 0; i < parent->rowCount(); i++)
{
if (parent->child(i)->checkState() == Qt::Checked)
checkCount++;
}
if(checkCount == 0)
parent->setCheckState(Qt::Unchecked);
else if (checkCount == parent->rowCount())
parent->setCheckState(Qt::Checked);
else
parent->setCheckState(Qt::PartiallyChecked);
}
}

Answer 1

Unless I've misunderstood your question it seems that your solution is massively over-complicated. You should be able to do this trivially with the default QStandardItemModel implementation.
How about something like this (error handling omitted)?
QObject::connect(model, SIGNAL(itemChanged(QStandardItem*)), someObject, SLOT(modelItemChanged(QStandardItem*)));
And then in the signal handler:
void modelItemChanged(QStandardItem* item)
{
QStandardItem* parent = item->parent();
int checkCount = 0;
int rowCount = parent->rowCount();
for (int i = 0; i < rowCount; i++)
{
if (parent->child(i)->checkState() == Qt::Checked)
checkCount++;
}
switch (checkCount)
{
case 0:
parent->setCheckState(Qt::Unchecked);
break;
case rowCount:
parent->setCheckState(Qt::Checked);
break;
default:
parent->setCheckState(Qt::PartiallyChecked);
}
}
This is by no means optimal but it may be good enough for your purposes.