Autofill to correct size in Qt Tables - c++

Question

I am trying to learn Qt by doing some project, and would like quick pointer on one part of my requirement.
I have database with multi-line passages, that I want to show in Qt using some view.
What I additionally want is that user does not have to re-size the window in order to read, so, if big passage comes in, then size shrinks, and will small passage, the font increase such that it takes the total space to display.
Kindly suggest :
what logic or functionality will suit to shrink and expand size, or is there a widget/view that already do so(by modifying the property) or suggestion on how to achieve it.
Same question again, to show shrink/expanded things, but using only using tree view. Then can I do this in tree view? And how?

Answer 1

Here is a way you could do it with a custom QItemDelegate.
Note that this solution isn't complete, you still need to do some work here.
First, some code to setup a QStandardItemModel and QTreeView.
The View uses a custom Delegate, which is described below.
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QStandardItemModel model(4, 4);
for (int row = 0; row < 4; ++row) {
for (int column = 0; column < 4; ++column) {
QStandardItem *item = new QStandardItem(QString("row %0, column %1").arg(row).arg(column));
model.setItem(row, column, item);
}
}
Delegate delegate;
QTreeView view;
view.setItemDelegate(&delegate);
view.setModel(&model);
view.setWindowTitle("QTreeView with custom delegate");
view.show();
return a.exec();
}
Here comes the code for the Delegate.
It looks how much space is available for the text, and then tries to find a font size that fits.
I'm currently only checking the width and ignoring height.
class Delegate : public QItemDelegate
{
void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const;
};
void Delegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
QRect availableSpace = option.rect;
// padding taking place, don't know how to find out how many pixels are padded.
// for me, subtracting 6 looked ok, but that's not a good solution
availableSpace.setWidth(availableSpace.width() - 6);
QString text = index.data().toString();
QStyleOptionViewItem newOption(option);
// initial font size guess
float size = 20;
int width;
// try to make font smaller until the text fits
do
{
newOption.font.setPointSizeF(size);
size -= .1;
width = QFontMetrics(newOption.font).width(text);
}
while (width > availableSpace.width());
newOption.textElideMode = Qt::ElideNone;
// call the parent paint method with the new font size
QItemDelegate::paint(painter, newOption, index);
}
This is what the result looks like: