UI: Add SliderAbsoluteSetStyle class

When this class is used in conjunction with a QSlider control, allows
direct setting of the slider handle position when clicking in an area
other than the slider handle.  The default QSlider handle behavior is to
step towards clicked position.

obs/slider-absoluteset-style.cpp

@@ -0,0 +1,19 @@
+#include "slider-absoluteset-style.hpp"
+
+SliderAbsoluteSetStyle::SliderAbsoluteSetStyle(const QString& baseStyle)
+	:QProxyStyle(baseStyle)
+{
+}
+SliderAbsoluteSetStyle::SliderAbsoluteSetStyle(QStyle* baseStyle)
+	:QProxyStyle(baseStyle)
+{
+}
+
+int SliderAbsoluteSetStyle::styleHint(QStyle::StyleHint hint,
+	const QStyleOption* option = 0, const QWidget* widget = 0,
+	QStyleHintReturn* returnData = 0) const
+{
+	if(hint == QStyle::SH_Slider_AbsoluteSetButtons)
+		return (Qt::LeftButton | Qt::MidButton);
+	return QProxyStyle::styleHint(hint, option, widget, returnData);
+}