Transient scrollbar in Qt - macos

Question

I want to use transient scrollbar (Transient scroll bars appear when the content is scrolled and disappear when they are no longer needed) in Qt application. For this purpose I have inheritanced class QproxyStyle and reimplemented function styleHint. Code placed below.
File ScrollBar.h:
#include <QStyle>
#include <QCommonStyle>
#include <QProxyStyle>
class ScrollBarStyle : public QProxyStyle
{
public:
int styleHint(StyleHint sh, const QStyleOption *opt, const QWidget *widget, QStyleHintReturn *hret) const;
};
File ScrollBar.c:
#include "ScrollBar.h"
int ScrollBarStyle::styleHint(StyleHint sh, const QStyleOption *opt, const QWidget *widget,QStyleHintReturn *hret) const
{
int ret = 0;
switch (sh) {
case SH_ScrollBar_Transient:
ret = true;
break;
default:
return QProxyStyle::styleHint(sh, opt, widget, hret);
}
return ret;
}
File MainWindow.h:
#include <QMainWindow>
#include <QTextEdit>
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = 0);
~MainWindow();
};
File MainWindow.cpp:
#include <QTextEdit>
#include "MainWindow.h"
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
QTextEdit *l = new (std::nothrow) QTextEdit(this);
if (l == 0)
return;
setCentralWidget(l);
}
MainWindow::~MainWindow()
{
}
File main.cpp:
#include "ScrollBar.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
ScrollBarStyle *style = new (std::nothrow) ScrollBarStyle;
if(style == 0)
return -1;
style->setBaseStyle(a.style());
w.show();
return a.exec();
}
But I have got a problem: transient scrollbar has been appearing only once (when text doesn't fit in the text area) then it has been disappeared and never come back visible.
So how can I fix this problem?
Thanks!

Answer 1

You have forgotten to set the style to application.
a.setStyle(style);