Drawing a widget in QItemDelegate's paint method

[darkadept]

Alright, I guess what I was going for originally would look something like the screencap in this post:

http://www.ereslibre.es/?p=61

I know that's with KDE4.x but I was wondering if there was an easy way to implement it.

Also, I have Qt 4.3.1 installed now and I'm still getting zero's in my sizeHint() option.rect parameter.

[darkadept]

I'm beginning to think that there is a bug with the QStyleOptionViewItem parameter in QAbstractItemDelegate's sizeHint() method.

How can I calculate the sizeHint if I don't know in what rect I'm working in? This makes drawing wrapped text impossible. I want to dynamically adjust the height depending on how much text can fit on screen.

Ahh well.

[marcel]

It is possible to implement dynamic word-wrap. I have done it for a QListView.

See this post: http://www.qtcentre.org/forum/f-qt-p...view-8371.html

Regards

[darkadept]

Your code works wonderfully! Thanks.

But isn't assuming that the parent of the delegate is a QListView a bad thing? So I modified your sizeHint() method to use QAbstractItemView instead of QListView.

QAbstractItemView *p = (QAbstractItemView*)parent();
	QString text = index.data(Qt::DisplayRole).toString();
	QFontMetrics fm(option.fontMetrics);
 
	float rw = float(p->viewport()->size().width());
	float tw = fm.width(text);
	float ratio = tw/rw;
	int lines = int(ratio) + 1;
 
	return QSize(rw,lines*fm.height());

QAbstractItemView *p = (QAbstractItemView*)parent();
	QString text = index.data(Qt::DisplayRole).toString();
	QFontMetrics fm(option.fontMetrics);

	float rw = float(p->viewport()->size().width());
	float tw = fm.width(text);
	float ratio = tw/rw;
	int lines = int(ratio) + 1;

	return QSize(rw,lines*fm.height());

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But yes, the gaping flaw is that by using viewport()->size() this delegate will only work when the item consumes the entire width of the view. In a QAbstractTableView we will have problems. I guess I'll tackle one thing at a time.

Thanks a ton for the help!

[marcel]

But isn't assuming that the parent of the delegate is a QListView a bad thing?

I made it for that particular case.
I didn't think someone else might use it.

Regards

[marcel]

BTW:

I'm beginning to think that there is a bug with the QStyleOptionViewItem parameter in QAbstractItemDelegate's sizeHint() method.

How can I calculate the sizeHint if I don't know in what rect I'm working in? This makes drawing wrapped text impossible. I want to dynamically adjust the height depending on how much text can fit on screen.

That QRect is actually based on the sizeHint you return.
The framework first calls sizeHint for the delegate and then paints it.

Regards

[darkadept]

That QRect is actually based on the sizeHint you return.
The framework first calls sizeHint for the delegate and then paints it.

Following that frame of thought, then making wrapping text work in a QTreeView and QTableView is different then in the QListView.
I haven't tested this yet but I think you would do something like this:

QSize PluginDelegate::sizeHint(const QStyleOptionViewItem & option, const QModelIndex & index) const
{
    int width;
 
    if (qobject_cast<QColumnView *>(parent()) != 0) {
        QColumnView *v = qobject_cast<QColumnView *>(parent());
        width = v->columnWidths().at(index.column());
    } else if (qobject_cast<QHeaderView *>(parent()) != 0) {
        //i'm going to leave this out for now because I don't know how to get the width of a QHeaderView cell
        width = 100;  //dumb value
    } else if (qobject_cast<QTableView *>(parent()) != 0) {
        QTableView *v = qobject_cast<QTableView *>(parent());
        width = v->columnWidth(index.column());
    } else if (qobject_cast<QTreeView *>(parent()) !=0) {
        QTreeView *v = qobject_cast<QTreeView *>(parent());
        width = v->columnWidth(index.column());
    } else if (qobject_cast<QListView *>(parent()) != 0) {
        QListView *v = qobject_cast<QListView*>(parent());
        width = p->viewport()->size().width();
    } else {
        //specify default value if we are using a non-standard view
        width = 400;
    }
 
    // ... calculate text wrapping and cell/row height based on width.
 
    // ... future feature: specify max # of text lines and then elide the text if it's too long. (see QFontMetrics::elidedText() method)
 
}

QSize PluginDelegate::sizeHint(const QStyleOptionViewItem & option, const QModelIndex & index) const
{
    int width;

    if (qobject_cast<QColumnView *>(parent()) != 0) {
        QColumnView *v = qobject_cast<QColumnView *>(parent());
        width = v->columnWidths().at(index.column());
    } else if (qobject_cast<QHeaderView *>(parent()) != 0) {
        //i'm going to leave this out for now because I don't know how to get the width of a QHeaderView cell
        width = 100;  //dumb value
    } else if (qobject_cast<QTableView *>(parent()) != 0) {
        QTableView *v = qobject_cast<QTableView *>(parent());
        width = v->columnWidth(index.column());
    } else if (qobject_cast<QTreeView *>(parent()) !=0) {
        QTreeView *v = qobject_cast<QTreeView *>(parent());
        width = v->columnWidth(index.column());
    } else if (qobject_cast<QListView *>(parent()) != 0) {
        QListView *v = qobject_cast<QListView*>(parent());
        width = p->viewport()->size().width();
    } else {
        //specify default value if we are using a non-standard view
        width = 400;
    }

    // ... calculate text wrapping and cell/row height based on width.

    // ... future feature: specify max # of text lines and then elide the text if it's too long. (see QFontMetrics::elidedText() method)

}

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I'm sure there is a way to optimize that whole thing too, of course.

Now if you know for sure that your delegate will only ever be used in a QListView then don't do the above.

[andytork]

Alright, I guess what I was going for originally would look something like the screencap in this post:

http://www.ereslibre.es/?p=61

I know that's with KDE4.x but I was wondering if there was an easy way to implement it.

Also, I have Qt 4.3.1 installed now and I'm still getting zero's in my sizeHint() option.rect parameter.

Did anyone ever come up with similar list to the above. I am trying to produce something similar and finding it very hard

Thanks
Andy

[shrike.pt]

I'm reviving this thread, since I need a solution to exactly this kind of problem.
I need to create a list of items with a lot of functionality and a "Look" which is quite different to a standard ListView.
Each item has multiple images, text labels with multiple formats, and multiple "action" areas, with mouse-over "hot" re-draw funtionality.
Also, anyone knows for sure what the lifetime of each item in a QListView is ? The list of items can be quite large, so I'm hopping it only keps in memory the items currently in view and requests re-draw/re-create of the item when it comes into view.
To get an ideia of what i need, go have a look at any decently powerful, fully-functional tweeter client.

[shrike.pt]

Ok, I think I've got it.
In case anyone else needs to do this:
http://www.qtforum.org/article/25345...tviewitem.html

Basically create a delegate inheriting QAbstractItemDelegate, with a reference to a widget which "looks" and "acts" like you want your nodes to do.
Override editorEvent in your delegate and pass the event to your widget, remembering to set it's data first and to adjust mouse position for the widget.

Then just use the sizeHint event to set data ( it will be called first every time your itemview needs something from your node) and render the widget to the painter in the paint event.

Presto, virtual itemview having only one "real" widget no matter how many nodes. Tested with 50k items, works beautifully.