Why does QMenuBar resize icons?

[drhex]

Hi all,

In the small example below I am inserting a small pixmap into a QAction in a
QMainWindow's menubar. I'm using a pixmap ("key.png") that is 19 by 9 pixels,
but QT resizes it to 16x7.

A 19x9 pixels image would easily fit on the menubar, so why does QT feel a need to resize? Is there a way to have it shown in its original size?

(QT4.2, X-Windows)

/Joakim

#include <QApplication>
#include <QMainWindow>
#include <QMenu>
#include <QMenuBar>
 
 
int main( int argc, char **argv )
{
    QApplication app( argc, argv );
 
    QMainWindow *mw = new QMainWindow();
    mw->show();
 
    QMenuBar *mb = mw->menuBar();
    QMenu *menu = new QMenu("File");
    mb->addMenu(menu);
    menu->addAction("About", &app, SLOT(aboutQt()));
 
    QAction *act = mb->addAction("");
    act->setIcon(QPixmap("key.png"));
 
    app.exec();
    return 0;
}

#include <QApplication>
#include <QMainWindow>
#include <QMenu>
#include <QMenuBar>


int main( int argc, char **argv )
{
    QApplication app( argc, argv );

    QMainWindow *mw = new QMainWindow();
    mw->show();

    QMenuBar *mb = mw->menuBar();
    QMenu *menu = new QMenu("File");
    mb->addMenu(menu);
    menu->addAction("About", &app, SLOT(aboutQt()));

    QAction *act = mb->addAction("");
    act->setIcon(QPixmap("key.png"));

    app.exec();
    return 0;
}

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[jpn]

QMenu uses QStyle::PM_SmallIconSize. You could use a custom style and provide larger PM_SmallIconSize.

[drhex]

Alright, I found out what style the menubar was using by calling metaObject()->className() on it. It was QPlastiqueStyle,,
so I replaced the style with an instance of the class below:

class myStyle: public QPlastiqueStyle
{
    Q_OBJECT
  public:
    int pixelMetric(PixelMetric metric, const QStyleOption * option = 0, const QWidget * widget = 0 ) const {
        int s = QPlastiqueStyle::pixelMetric(metric, option, widget);
        if (metric == QStyle::PM_SmallIconSize) {
            s = 20;
        }
        return s;
    }
};

class myStyle: public QPlastiqueStyle
{
    Q_OBJECT
  public:
    int pixelMetric(PixelMetric metric, const QStyleOption * option = 0, const QWidget * widget = 0 ) const {
        int s = QPlastiqueStyle::pixelMetric(metric, option, widget);
        if (metric == QStyle::PM_SmallIconSize) {
            s = 20;
        }
        return s;
    }
};

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Small icons can now be upto 20x20 pixels instead of 16x16. And it works!
But one thing still bothers me, I had to hardcode "QPlastiqueStyle". What if another style had been specified on the commandline? Is there a way to modify the behaviour of the current style rather than forcing in a specific style?

[jpn]

But one thing still bothers me, I had to hardcode "QPlastiqueStyle". What if another style had been specified on the commandline? Is there a way to modify the behaviour of the current style rather than forcing in a specific style?

There's a technique called proxy style. A proxy style redirects all other than overridden calls to the "original" style.

[duduqq]

can you give me you code ,I have the same proble,I am a new guy at qt

could you sent a email to me
ouyangzy2005@163.com

[Farseer]

Hi, i use above code
int s = QPlastiqueStyle:: pixelMetric(metric, option, widget);
if (metric == QStyle::PM_SmallIconSize) {
s = 50;
}
then the icon and text overlap, it seems the text position doesn't change when the icon become large.
How to solve this problem?