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qt5ellipsisqcombobox

QComboBox elided text on selected item

So, I have a QComboBox.

enter image description here

If the currentText() is too long for the widget then I want to show an ellipsis.

Like this :

enter image description here

So :

void MyComboBox::paintEvent(QPaintEvent * )
{
      QStylePainter painter(this);
      QStyleOptionComboBox opt;
      initStyleOption(&opt);
      painter.drawComplexControl(QStyle::CC_ComboBox, opt);

      QRect rect = this->rect();
      //this is not ideal
      rect.setLeft(rect.left() + 7);
      rect.setRight(rect.width() - 15);
      //

      QTextOption option;
      option.setAlignment(Qt::AlignVCenter);

      QFontMetrics fontMetric(painter.font());
      const QString elidedText = QAbstractItemDelegate::elidedText(fontMetric, rect.width(), Qt::ElideRight, this->currentText());
      painter.drawText( rect, elidedText, option);
}

This is working flawlessy. The problem is the code in between the comments, because I am hardcoding the distances from the left and right border. It makes me cringe.

The result without that code is:

enter image description here

Does anybody know a more general way to do this, without hardcoding? Thank you

Solution

  • Where the text should be drawn exactly depends on the used style. You can get information about (some of) the positioning of subelements with QStyle::subControlRect. The subcontrol that matches the combo box text best seems to be QStyle::SC_ComboBoxEditField, though if the item has an icon, this needs to be taken into account as well. If the items do not have icons, you can go with

      QRect textRect = style()->subControlRect(QStyle::CC_ComboBox, &opt, QStyle::SC_ComboBoxEditField, this);
  QFontMetrics fontMetric(painter.font());
  const QString elidedText = QAbstractItemDelegate::elidedText(fontMetric, textRect.width(), Qt::ElideRight, this->currentText());
  opt.currentText = elidedText;
  painter.drawControl(QStyle::CE_ComboBoxLabel, opt);

    You might want to have a look at how e.g. QFusionStyle::drawControl works for details.

    In general, if you want all your combo boxes to elide the text, you should consider implementing your own QProxyStyle and only override MyStyle::drawControl for QStyle::CE_ComboBoxLabel.