QToolButton with icon + text: How to center both?

Question

I am using multiple QToolButtons in a custom QGridLayout widget. The buttons are set to display icon + text based on an assigned default QAction. The only issue is that the content (icon + text) is always left-aligned.

The content (icon + text, marked as a red box in the screenshot), should be center in the button (indicated by the blue box).

For most cases this is just fine, given that Qt automatically tries to render that button with the minimal size. However I am stretching the button to fit nicely into my QGridLayout.

QToolButton* pButton = new QToolButton(0);
pButton->addDefaultAction(pAction);
pButton->setToolButtonStyle(Qt::ToolButtonTextBesideIcon);
pButton->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Preferred);

QGridLayout *pActionAreaLayout = new QGridLayout;
pActionAreaLayout->addWidget(pSomeOtherWidget, 0, 0, 1, 2);
pActionAreaLayout->addWidget(pButton , 1, 0, 1, 1);

Is there a way to force the content to be centered in the button?

PS: I found the following comment in another forum, which however seems quite invasive and is not really clear to me yet:

You can try doing the horizontal alignment using a stylesheet, but you probably have to implement a QStyle proxy and reimplement drawControl() for QStyle::CE_ToolButtonLabel Or derive from QToolButton, overwrite paintEvent() and call the style for everything other than the label.

Answer 1

The following class does the job for me:

class CenteredToolButtonStyle : public QProxyStyle
{
Q_OBJECT

public:
CenteredToolButtonStyle(QToolButton* b, const QSize& sIcon);

virtual void drawItemPixmap(QPainter *painter, const QRect &rect, int, const QPixmap &pixmap) const
    override { m_pic = pixmap; m_ny = rect.y(); Draw(painter); }
virtual void drawItemText(QPainter *painter, const QRect &rect, int flags, const QPalette &pal, bool enabled,
    const QString &text, QPalette::ColorRole textRole = QPalette::NoRole) const override;
void Draw(QPainter *painter) const;

const QToolButton* B;
const QSize SICON;
mutable QString m_s;
mutable QPixmap m_pic;
mutable QRect m_r;
mutable int m_nf, m_ny;
mutable bool m_bEnabled;
mutable QPalette m_pal;
mutable QPalette::ColorRole m_textRole;
};


CenteredToolButtonStyle::CenteredToolButtonStyle(QToolButton* b, const QSize& sIcon)
: QProxyStyle(), B(b), SICON(sIcon), m_nf(0), m_bEnabled(true), m_ny(0)
{
b->setToolButtonStyle(Qt::ToolButtonTextBesideIcon);
setParent(b);
}

void CenteredToolButtonStyle::drawItemText(QPainter *painter, const QRect &rect, int flags, const QPalette &pal,
bool enabled, const QString &text, QPalette::ColorRole textRole/* = QPalette::NoRole*/) const
{
m_s = text;
m_r = rect;
m_nf = flags | Qt::AlignCenter;
m_bEnabled = enabled;
m_pal = pal;
m_textRole = textRole;
Draw(painter);
}

void CenteredToolButtonStyle::Draw(QPainter *painter) const
{
if (m_ny) {
    if (m_r.y() != m_ny) return;
    auto r = m_r;
    r.adjust(-SICON.width() - 8, m_ny = 0, -itemTextRect(B->fontMetrics(), m_r, m_nf, m_bEnabled, m_s).width(), 0);
    QProxyStyle::drawItemPixmap(painter, r, Qt::AlignCenter, m_pic);
}
QProxyStyle::drawItemText(painter, m_r, m_nf, m_pal, m_bEnabled, m_s, m_textRole);
}

Sample use:

foreach(auto b, ui.mainToolBar->findChildren<QToolButton*>()) 
    b->setStyle(new CenteredToolButtonStyle(b, ui.mainToolBar->iconSize()));

Answer 2

As I suggest in answer to you another question. https://stackoverflow.com/a/28630318/1917249 Do not use QToolButton, just use QPushButton, and add popup menu if needed.

Then you wont have different sizes of QToolButton and QPushButton widgets. And you will have centered icon and text.

Popupmenu can be easily added to QPushButton ( only small arrow wont be shown )

QPushButton *pushButton = new QPushButton(toolAction->icon(), "PushButton", window);
// window - widget where button is placed ( to get correct QMenu position )
QObject::connect(pushButton, &QPushButton::released, [window, pushButton, action](){
    QMenu menu;
    menu.addAction(action);
    QPoint pos = window->mapToGlobal(pushButton3->pos());
    pos += QPoint(0, pushButton->height());
    menu.exec(pos);
 });

Or you can subclass QPushButton and add Popup menu handling there. Much better then try to center text with icon in QToolButton or have in same size of QPushButton and QToolButton

For complex example please see my answer: https://stackoverflow.com/a/28630318/1917249