How to change the spacing of icons in the toolbar？

[Qt_crazyer]

My toolbar is like above. I want change my icons spacing. It seems that there is no special function to achieve it. In QStyle, I find this variable QStyle:: PM_ToolBarItemSpacing, is this variable changed? Or what other methods should be done?
Thanks for any advice!
Qt Creator 5.9.1+windows

[Chris Kawa]

To change it globally you should create a proxy style and change the value you mentioned i.e.

class CustomStyle : public QProxyStyle
{
public:
    int pixelMetric(PixelMetric metric, const QStyleOption* option = nullptr, const QWidget* widget = nullptr) const override
    {
        if (metric == QStyle:: PM_ToolBarItemSpacing)
            return 100; //or whatever you want
        else
            return QProxyStyle::pixelMetric(metric, option, widget);
    }
};

and then set it on the app object in main():

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    a.setStyle(new CustomStyle);

    ...