Custom widget table sort

[giantdragon]

I have QTableWidget with custom progress bars (derived from QWidget), inserted into table with setCellWidget. Each bar have "progress" property and I need to sort by it. I reimplemented "<" operator, but sorting doesn't work and operator "<" not even called.

Header:

bool operator < (const ProgressBar &other);
CPP:


bool ProgressBar::operator < (const ProgressBar &other)
{
return progress < other.progress;
}

[wysota]

What exactly are you "sorting"? How are you calling the sort? If you are trying to sort widgets then it won't work :) Well... actually it will sort them but nothing in Qt expects widgets to be sorted so if you're hoping for some automatic behaviour, nothing like that will happen.

[giantdragon]

Is it possible to sort QTableWidget by custom widget?

[Santosh Reddy]

Yes it is, One way to do so is to create a CustomTableWidgetItem like this


class CustomTableWidgetItem : public QWidget, public QTableWidgetItem
{
...
public:
virtual bool operator<(const QTableWidgetItem& other) const
{
; // re-implement this, as per you sorting requirement
}
...
}

CustomTableWidgetItem gives you an interface for both you Widget (QProgressBar in your case) and QTableWidgetItem

Warning: You need to properly implement operator<(), as the the parameter "other" is not guarantied to be a CustomTableWidgetItem (unless all the items in your QTableWidget are of type CustomTableWidgetItem)

You can also inherit CustomTableWidgetItem from QProgressBar instead of QWidget, it's up to you.

[giantdragon]

All elements in given column will be custom progress bars.
In operator "<" you pass "const QTableWidgetItem&", but I need to access to the custom progress bar's property, it seems that I need to cast "this" and "other" to custom progress bar type, but dynamic_cast or "(ProgressBar*) this" doen't work.

[wysota]

If you want to do it properly then store the value of progress in your model (aka item data) and apply a custom delegate that will render the looks of a progress bar to the element. Search the forum for information how to implement a custom delegate showing a progress bar.

[Santosh Reddy]

You don't need to cast this, you just to cast other, your operator will look like this

class CustomTableWidgetItem : public QProgressBar, public QTableWidgetItem{
...
}
bool CustomTableWidgetItem::operator<(const QTableWidgetItem& other) const
{
const QProgressBar *that = dynamic_cast<const QProgressBar *>(&other);
if(that != 0)
{
if(this->value() < that->value())
return true;
}
return false;
}

[giantdragon]

Sorting now works, thanks for your answer.
But another problem emerged - I use custom progress bar (not QProgressBar) and reimplemented paintEvent to draw my own progress bar. If I add my bar to table with "setCellWidget" function sorting works, but I see white area instead of progress indicator. If I add it with "setItem" function painting works well, but sorting doesn't work.

[wysota]

Then do it properly (see #6).

[Santosh Reddy]

You need to use both setItem(), and setCellWidget().
You need set the CustomTableWidgetItem on the table using setItem(), and use setCellWidget() somewhere in the ctor (or relevant method) of CustomTableWidgetItem

[giantdragon]

It now both paints and sorts. Thanks.

In my custom table's add method:


...
setCellWidget(i, 1, bar);
setItem(i, 1, bar);