Minimum size/width of a QPushButton that is created from code

I created 2 rows of push buttons, each row is inside a QHBoxLayout.

I create the buttons in the code:

static const char* buttonText = "23456789TJQKA";
for (int ii = 0; buttonText[ii]; ii++)
{
    QPushButton* pushButton = new QPushButton(this);
    pushButton->setText(QString(buttonText[ii]));
    ui->horizontalLayout_1->addWidget(pushButton);
}
for 开发者_JAVA技巧(int ii = 0; buttonText[ii]; ii++)
{
    QPushButton* pushButton = new QPushButton(this);
    pushButton->setText(QString(buttonText[ii]));
    ui->horizontalLayout_2->addWidget(pushButton);
}

The problem is that they can't shrink (when the user resizes the dialog) beyond that size, even though their text would fit in a much smaller width. If I create the buttons manually in the resource editor instead of in the code, they can have smaller width than that.

This happens because the minimumSizeHint of the QPushButton does not allow the QLayout to resize it :

The default implementation of minimumSizeHint() returns an invalid size if there is no layout for this widget, and returns the layout's minimum size otherwise. Most built-in widgets reimplement minimumSizeHint().

QLayout will never resize a widget to a size smaller than the minimum size hint unless minimumSize() is set or the size policy is set to QSizePolicy::Ignore. If minimumSize() is set, the minimum size hint will be ignored.

The simple solution is to set the minimum width explicitly:

static const char* buttonText = "23456789TJQKA";
for (int ii = 0; buttonText[ii]; ii++)
{
   QPushButton* pushButton = new QPushButton(this);
   pushButton->setMinimumWidth(5);
   pushButton->setText(QString(buttonText[ii]));
   ui->horizontalLayout_1->addWidget(pushButton);
}
for (int ii = 0; buttonText[ii]; ii++)
{
   QPushButton* pushButton = new QPushButton(this);
   pushButton->setMinimumWidth(5);
   pushButton->setText(QString(buttonText[ii]));
   ui->horizontalLayout_2->addWidget(pushButton);
}

As pnezis wrote, you probably want to override the default minimum size calculated by the button. Here's a way you can do it while avoiding to choose an arbitrary size that might not work when conditions vary (different font or font size, UI style, etc):

QWidget* parent = /* some widget */
auto button = new QPushButton(QLatin1String("X"), parent);
auto textSize = button->fontMetrics().size(Qt::TextShowMnemonic, button->text());
QStyleOptionButton opt;
opt.initFrom(button);
opt.rect.setSize(textSize);
button->setMinimumSize(
  button->style()->sizeFromContents(QStyle::CT_PushButton,
                                    &opt,
                                    textSize,
                                    button));

The above was adapted and simplified from QPushButton's own code. You may want to look at the source of QPushButton::sizeHint for all the details.

setMaximumWidth works for me. sample code is in pyqt, but it should translate directly to C++ without any problems.

from PyQt4 import QtGui

class Window(QtGui.QWidget):
    def __init__(self):
        super(Window, self).__init__()
        layout = QtGui.QHBoxLayout()
        texts = [":)",
                 "&Short",
                 "&Longer",
                 "&Different && text",
                 "More && text",
                 "Even longer button text", ]
        for text in texts:
            btn = QtGui.QPushButton(text)
            double = text.count('&&')
            text = text.replace('&', '') + ('&' * double)
            width = btn.fontMetrics().boundingRect(text).width() + 7
            btn.setMaximumWidth(width)
            layout.addWidget(btn)
        self.setLayout(layout)

if __name__ == '__main__':
    import sys

    app = QtGui.QApplication(sys.argv)
    mainWin = Window()
    mainWin.show()
    sys.exit(app.exec_())