[Qt4] Noob and custom Item Delegate

[naresh]

Hello! I'm trying to create custom item delegate to view multiline text in QTreeView properly... So I've started trying to create my delegate... the result is that it doesn't draw anything (the scrollbar appear when i resize app window so items are there) :| Here is some code:

painting:

void rosterDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
  painter->setRenderHint(QPainter::TextAntialiasing);
  painter->setPen(Qt::NoPen);
 
  if (option.state & QStyle::State_Selected)
    painter->setBrush(option.palette.highlight());
  else
    painter->setBrush(QBrush(Qt::white));
 
  QTextOption textOption;
  textOption.setWrapMode(QTextOption::WordWrap);
 
  QSize sizehint=sizeHint(option, index);
  int width=Qxygen->viewWidth();
  int height=ceil((sizehint.width()*sizehint.height())/width);
 
  rosterItem *item = static_cast<rosterItem*>(index.internalPointer());
 
  painter->drawText(QRectF(option.rect.x(), option.rect.y(), width, height), /* FROM WHERE GET THAT TEXT?  */, textOption);
}

void rosterDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
  painter->setRenderHint(QPainter::TextAntialiasing);
  painter->setPen(Qt::NoPen);

  if (option.state & QStyle::State_Selected)
    painter->setBrush(option.palette.highlight());
  else
    painter->setBrush(QBrush(Qt::white));

  QTextOption textOption;
  textOption.setWrapMode(QTextOption::WordWrap);

  QSize sizehint=sizeHint(option, index);
  int width=Qxygen->viewWidth();
  int height=ceil((sizehint.width()*sizehint.height())/width);

  rosterItem *item = static_cast<rosterItem*>(index.internalPointer());

  painter->drawText(QRectF(option.rect.x(), option.rect.y(), width, height), /* FROM WHERE GET THAT TEXT?  */, textOption);
}

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here is my modelView data

QVariant rosterView::data(const QModelIndex &index, int role) const
{
  if (!index.isValid())
    return QVariant();
 
  if (role == Qt::DisplayRole)
  {
    rosterItem *item = static_cast<rosterItem*>(index.internalPointer());
 
    if(descr && !(item->isGroup())) // CHECKS IF VIEW HAS TO SHOW ITEM DESCRIPTION AND ITEM ISN'T GROUP - GROUPS DOESN'T NEED DESCRIPTION
    {
      if((item->data(1)).isEmpty()) return item->data(index.column());
      else return QString(item->data(index.column()))+"\n"+QString(item->data(1));
    }
    else
    {
      return item->data(index.column());
    }
  }
  else if(role == Qt::DecorationRole)
  {
    rosterItem *item = static_cast<rosterItem*>(index.internalPointer());
    if(item->isGroup())
    {
      if(item->isExpanded())
      {
        return QIcon(":expanded.png");
      }
      else
      {
        return QIcon(":collapsed.png");
      }
    }
    else
    {
      return QIcon(":dnd.png");
    }
  }
  else
  {
    return QVariant();
  }
}

QVariant rosterView::data(const QModelIndex &index, int role) const
{
  if (!index.isValid())
    return QVariant();

  if (role == Qt::DisplayRole)
  {
    rosterItem *item = static_cast<rosterItem*>(index.internalPointer());

    if(descr && !(item->isGroup())) // CHECKS IF VIEW HAS TO SHOW ITEM DESCRIPTION AND ITEM ISN'T GROUP - GROUPS DOESN'T NEED DESCRIPTION
    {
      if((item->data(1)).isEmpty()) return item->data(index.column());
      else return QString(item->data(index.column()))+"\n"+QString(item->data(1));
    }
    else
    {
      return item->data(index.column());
    }
  }
  else if(role == Qt::DecorationRole)
  {
    rosterItem *item = static_cast<rosterItem*>(index.internalPointer());
    if(item->isGroup())
    {
      if(item->isExpanded())
      {
        return QIcon(":expanded.png");
      }
      else
      {
        return QIcon(":collapsed.png");
      }
    }
    else
    {
      return QIcon(":dnd.png");
    }
  }
  else
  {
    return QVariant();
  }
}

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Now i have no idea how to make my delegate paint icon and text (in one column). Any suggestion/help?

[wysota]

It's best to see how the default delegate does it. Where to get the text to render? From the model Using data(index, Qt :: DisplayRole). But in your case it should be enough to change style options (to turn on word wrapping) and call the default delegate.

[naresh]

Turn on word wrapping to what? QTreeView and QItemDelegate has no such property. I also need to display description italic... I know that QTreeView has property uniformRowHeights and its already changed to false (by calling setUniformRowHeights(FALSE)). So where to set word wrapping and is it possible to display description in italics?

[wysota]

You might want to take a look at QStyleOptionViewItem class. You have the ability to change font settings there.

Looks like I might have been wrong with the word wrapping thing, you need to set it directly.

Anyway, this is my multiline drawing "thing" (it's not a delegate but rather part of the view, but all rules remain the same).

void ColumnChartView::drawRowNames( QPainter * p ) {
    int itemwidth = itemWidth();
    int seriesCount = model()->columnCount();
    int columnWidth = itemWidth()/seriesCount;
    int maxh = chartSize().height();
    int valueSpan = _maxVal - _minVal;
    uint rowHeight = (_flags & XTitle) ? _canvasVMargin-QFontMetrics(font()).height()-2 : _canvasVMargin;
    p->save();
    for(int i=0;i<model()->rowCount(rootIndex());i++) {
        QRect rect(qRound(_canvasHMargin+itemwidth/4+i*itemwidth*3/2), maxh+_canvasVMargin, itemwidth, rowHeight);
        QStyleOptionViewItem opt = getOptionsForRowLabel(i);
        p->setFont(opt.font);
        p->setPen(opt.palette.color(QPalette::Normal, QPalette::Text));
        p->drawText(rect,opt.displayAlignment|Qt::TextWordWrap,QAbstractItemDelegate::elidedText(fontMetrics(), rect.width(),Qt::ElideRight,model()->headerData(i, Qt::Vertical).toString()));
    }
    p->restore();
}

void ColumnChartView::drawRowNames( QPainter * p ) {
    int itemwidth = itemWidth();
    int seriesCount = model()->columnCount();
    int columnWidth = itemWidth()/seriesCount;
    int maxh = chartSize().height();
    int valueSpan = _maxVal - _minVal;
    uint rowHeight = (_flags & XTitle) ? _canvasVMargin-QFontMetrics(font()).height()-2 : _canvasVMargin;
    p->save();
    for(int i=0;i<model()->rowCount(rootIndex());i++) {
        QRect rect(qRound(_canvasHMargin+itemwidth/4+i*itemwidth*3/2), maxh+_canvasVMargin, itemwidth, rowHeight);
        QStyleOptionViewItem opt = getOptionsForRowLabel(i);
        p->setFont(opt.font);
        p->setPen(opt.palette.color(QPalette::Normal, QPalette::Text));
        p->drawText(rect,opt.displayAlignment|Qt::TextWordWrap,QAbstractItemDelegate::elidedText(fontMetrics(), rect.width(),Qt::ElideRight,model()->headerData(i, Qt::Vertical).toString()));
    }
    p->restore();
}

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In your case you need to use model()->data() instead of model()->headerData().

Just for completeness:

QStyleOptionViewItem ColumnChartView::getOptionsForRowLabel( int row ) {
    QStyleOptionViewItem opt = viewOptions();
    opt.displayAlignment |= Qt::AlignHCenter;
    opt.displayAlignment &= ~Qt::AlignVCenter;
    opt.displayAlignment |= Qt::AlignTop;
    QVariant value;
    value = model()->headerData(row, Qt::Vertical, Qt::FontRole);
    if(value.isValid())
        opt.font = qvariant_cast<QFont>(value);
    value = model()->headerData(row, Qt::Vertical, Qt::TextColorRole);
    if(value.isValid() && qvariant_cast<QColor>(value).isValid())
        opt.palette.setColor(QPalette::Text, qvariant_cast<QColor>(value));
    return opt;
}

QStyleOptionViewItem ColumnChartView::getOptionsForRowLabel( int row ) {
    QStyleOptionViewItem opt = viewOptions();
    opt.displayAlignment |= Qt::AlignHCenter;
    opt.displayAlignment &= ~Qt::AlignVCenter;
    opt.displayAlignment |= Qt::AlignTop;
    QVariant value;
    value = model()->headerData(row, Qt::Vertical, Qt::FontRole);
    if(value.isValid())
        opt.font = qvariant_cast<QFont>(value);
    value = model()->headerData(row, Qt::Vertical, Qt::TextColorRole);
    if(value.isValid() && qvariant_cast<QColor>(value).isValid())
        opt.palette.setColor(QPalette::Text, qvariant_cast<QColor>(value));
    return opt;
}

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[naresh]

And when should i call drawRowNames?

[wysota]

You shouldn't I told you, it is part of my own code which does something different. But it behaves the same as the painting routine from a delegate. The part you might find interesting is the way to call drawText() and a way to set and use wanted item options (this is the way to transfer data between the view and the delegate -- for data transfer between the model and the delegate model()->data() should be used).

What my code does is to render a multiline text (if it can be wrapped to fit into the desired rectangle) or elide it if it's not possible to fit it all.

You might also want to reimplement sizeHint() for the delegate and calculate the size needed to fit your item (using QFontMetrics).

[naresh]

Well I've updated my delegate paint routine and still result is blank... Here it is:

void rosterDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
  painter->setRenderHint(QPainter::TextAntialiasing);
  painter->setPen(Qt::NoPen);
 
  if (option.state & QStyle::State_Selected)
    painter->setBrush(option.palette.highlight());
  else
    painter->setBrush(QBrush(Qt::white));
 
  QTextOption textOption;
  textOption.setWrapMode(QTextOption::WordWrap);
 
  rosterItem *item = static_cast<rosterItem*>(index.internalPointer());
 
  int width=Qxygen->viewWidth(), height;
 
	QFontMetrics fmetrics=Qxygen->fontMetrics();
 
  if(item->data(1).isEmpty())
  {
    height=fmetrics.height();
  }
  else
  {
    height=fmetrics.height()+fmetrics.height()*ceil(fmetrics.width(item->data(1))/width);
  }
 
  QRect rect(option.rect.x(), option.rect.y(), width, height);
 
  painter->drawText(rect,Qt::TextWordWrap,QAbstractItemDelegate::elidedText(static_cast<const QFontMetrics&>(Qxygen->roster()->fontMetrics()), rect.width(),Qt::ElideRight,Qxygen->model()->data(index, Qt::DisplayRole).toString()));
 
  printf("Width: %d Height:%d\n", width, height);
}

void rosterDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
  painter->setRenderHint(QPainter::TextAntialiasing);
  painter->setPen(Qt::NoPen);

  if (option.state & QStyle::State_Selected)
    painter->setBrush(option.palette.highlight());
  else
    painter->setBrush(QBrush(Qt::white));

  QTextOption textOption;
  textOption.setWrapMode(QTextOption::WordWrap);

  rosterItem *item = static_cast<rosterItem*>(index.internalPointer());

  int width=Qxygen->viewWidth(), height;

	QFontMetrics fmetrics=Qxygen->fontMetrics();

  if(item->data(1).isEmpty())
  {
    height=fmetrics.height();
  }
  else
  {
    height=fmetrics.height()+fmetrics.height()*ceil(fmetrics.width(item->data(1))/width);
  }

  QRect rect(option.rect.x(), option.rect.y(), width, height);

  painter->drawText(rect,Qt::TextWordWrap,QAbstractItemDelegate::elidedText(static_cast<const QFontMetrics&>(Qxygen->roster()->fontMetrics()), rect.width(),Qt::ElideRight,Qxygen->model()->data(index, Qt::DisplayRole).toString()));

  printf("Width: %d Height:%d\n", width, height);
}

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Still no idea why it doesn't print anything. As i said before my QTreeView behaves like there were all items... The scroll bar shows when i resize whole app

[wysota]

painter->setPen(Qt::NoPen);

painter->setPen(Qt::NoPen);

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How do you expect to paint anything without a pen?

[naresh]

Ok i've made even painting of icon, but it doesn't paint with the height i requested :|

Here's code:

void rosterDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
	painter->setRenderHint(QPainter::TextAntialiasing);
	//painter->setPen(Qt::NoPen);
 
	if (option.state == QStyle::State_Selected)
		painter->setBrush(option.palette.highlight());
	else
		painter->setBrush(QBrush(Qt::white));
 
	QTextOption textOption;
	textOption.setWrapMode(QTextOption::WordWrap);
 
	rosterItem *item = static_cast<rosterItem*>(index.internalPointer());
 
	int width=Qxygen->viewWidth(), height;
 
	QFontMetrics fmetrics=Qxygen->fontMetrics();
 
	if(item->data(1).isEmpty())
	{
		height=fmetrics.height();
	}
	else
	{
		height=fmetrics.height()+fmetrics.height()*qRound(fmetrics.width(item->data(1))/width);
		if(fmetrics.width(item->data(1))%width>0)
			height+=14;
	}
 
	printf("Width: %d Height:%d\n", width, height);
 
	QImage img=Qxygen->model()->data(index, Qt::DecorationRole).value<QImage>();
 
	QRect irect(option.rect.x(), option.rect.y(), img.width(), img.height());
	QRect rect(option.rect.x()+img.width()+2, option.rect.y(), width-img.width()-2, height);
 
	QTextOption opt;
	opt.setWrapMode(QTextOption::WordWrap);
	opt.setAlignment(Qt::AlignTop|Qt::AlignLeft);
 
	painter->drawImage(irect, img);
//	painter->drawText(rect, Qxygen->model()->data(index, Qt::DisplayRole).toString(), opt);
	painter->drawText(rect, Qt::TextWordWrap|Qt::AlignLeft|Qt::AlignTop, Qxygen->model()->data(index, Qt::DisplayRole).toString());
//	painter->drawText(rect,Qt::TextWordWrap,elidedText(static_cast<const QFontMetrics&>(Qxygen->roster()->fontMetrics()), rect.width(),Qt::ElideRight,Qxygen->model()->data(index, Qt::DisplayRole).toString()));
}

void rosterDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
	painter->setRenderHint(QPainter::TextAntialiasing);
	//painter->setPen(Qt::NoPen);

	if (option.state == QStyle::State_Selected)
		painter->setBrush(option.palette.highlight());
	else
		painter->setBrush(QBrush(Qt::white));

	QTextOption textOption;
	textOption.setWrapMode(QTextOption::WordWrap);

	rosterItem *item = static_cast<rosterItem*>(index.internalPointer());

	int width=Qxygen->viewWidth(), height;

	QFontMetrics fmetrics=Qxygen->fontMetrics();

	if(item->data(1).isEmpty())
	{
		height=fmetrics.height();
	}
	else
	{
		height=fmetrics.height()+fmetrics.height()*qRound(fmetrics.width(item->data(1))/width);
		if(fmetrics.width(item->data(1))%width>0)
			height+=14;
	}

	printf("Width: %d Height:%d\n", width, height);

	QImage img=Qxygen->model()->data(index, Qt::DecorationRole).value<QImage>();

	QRect irect(option.rect.x(), option.rect.y(), img.width(), img.height());
	QRect rect(option.rect.x()+img.width()+2, option.rect.y(), width-img.width()-2, height);

	QTextOption opt;
	opt.setWrapMode(QTextOption::WordWrap);
	opt.setAlignment(Qt::AlignTop|Qt::AlignLeft);

	painter->drawImage(irect, img);
//	painter->drawText(rect, Qxygen->model()->data(index, Qt::DisplayRole).toString(), opt);
	painter->drawText(rect, Qt::TextWordWrap|Qt::AlignLeft|Qt::AlignTop, Qxygen->model()->data(index, Qt::DisplayRole).toString());
//	painter->drawText(rect,Qt::TextWordWrap,elidedText(static_cast<const QFontMetrics&>(Qxygen->roster()->fontMetrics()), rect.width(),Qt::ElideRight,Qxygen->model()->data(index, Qt::DisplayRole).toString()));
}

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The painted text is in one line... When I resize app (height is calculated well i can see on console output) text isnt wrapped its only "hidden" behind border... Is there any possibility to put there rich text?

[wysota]

Ok i've made even painting of icon, but it doesn't paint with the height i requested :|

You can't "request" height. paint() only paints an item, it doesn't "set" its height. If you don't provide a boundingRect (or don't enable clipping) the text (or whatever you draw) will "flow out" of the item rectangle. Did you reimplement sizeHint for the delegate as I suggested (QItemDelegate)?

[naresh]

I didnt reimplement sizeHint... can you show me an example? I'm calculating width and height in paint (lines 20-29). Would you mind explaining me what were you mean by "don't enable clipping" and "boundingRect" ? ? ?