QLineEdit: displaying overlong text as a tooltip if hovering with mouse - c++

Question

Under Windows, I've seen a nice feature: If I hover with the mouse over a short text field which contains overlong text not fitting completely into the field, a tooltip opens, displaying the complete contents of the text field.
Can someone point me to a code snippet which does this with QLineEdit?

Answer 1

I would create a custom class derived from QLineEdit like so:
#ifndef LINEEDIT_H
#define LINEEDIT_H
#include <QtGui>
class LineEdit : public QLineEdit
{
Q_OBJECT
public:
LineEdit();
public slots:
void changeTooltip(QString);
};
LineEdit::LineEdit()
{
connect(this, SIGNAL(textChanged(QString)), this, SLOT(changeTooltip(QString)));
}
void LineEdit::changeTooltip(QString tip)
{
QFont font = this->font();
QFontMetrics metrics(font);
int width = this->width();
if(metrics.width(tip) > width)
{
this->setToolTip(tip);
}
else
{
this->setToolTip("");
}
}
#include "moc_LineEdit.cpp"
#endif // LINEEDIT_H
Then just add it to whatever:
#include <QtGui>
#include "LineEdit.h"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
LineEdit edit;
edit.show();
return app.exec();
}

Answer 2

Here the improved function as mentioned in the comments above.
void LineEdit::changeTooltip(QString tip)
{
QFont font = this->font();
QFontMetrics metrics(font);
// get the (sum of the) left and right borders;
// note that Qt doesn't have methods
// to access those margin values directly
int lineMinWidth = minimumSizeHint().width();
int charMaxWidth = metrics.maxWidth();
int border = lineMinWidth - charMaxWidth;
int lineWidth = this->width();
int textWidth = metrics.width(tip);
if (textWidth > lineWidth - border)
this->setToolTip(tip);
else
this->setToolTip("");
}

Answer 3

You can try to change the tooltip each time the text is changed:
First, define a private slot to react the textChanged() signal from the QLineEdit:
(in the header file from the class where your QTextEdit belongs)
....
private slots:
void onTextChanged();
....
In the cpp file, then, connect the QLineEdit textChanged() signal to the slot you defined, and implement the behavior when the text changes:
// In constructor, or wherever you want to start tracking changes in the QLineEdit
connect(myLineEdit, SIGNAL(textChanged()), this, SLOT(onTextChanged()));
Finally, this is how the slot would look like:
void MainWindow::onTextChanged() {
myLineEdit->setTooltip(myLineEdit->text());
}
I'm supposing a class called MainWindow contains the QLineEdit.