UI: Make T-Bar unclickable

The T-Bar should only be draggable and not act on clicks.

UI/slider-ignorewheel.cpp

@@ -94,3 +94,42 @@ QAccessible::Role VolumeAccessibleInterface::role() const
 {
 	return QAccessible::Role::Slider;
 }
+
+void SliderIgnoreClick::mousePressEvent(QMouseEvent *event)
+{
+	QStyleOptionSlider styleOption;
+	initStyleOption(&styleOption);
+	QRect handle = style()->subControlRect(QStyle::CC_Slider, &styleOption,
+					       QStyle::SC_SliderHandle, this);
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+	QPointF pointExact = event->position();
+#endif
+	if (handle.contains(
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+		    QPoint(pointExact.x(), pointExact.y())
+#else
+		    // Ubuntu 20.04. Sigh.
+		    QPoint(event->x(), event->y())
+#endif
+			    )) {
+		SliderIgnoreScroll::mousePressEvent(event);
+		dragging = true;
+	} else {
+		event->accept();
+	}
+}
+
+void SliderIgnoreClick::mouseReleaseEvent(QMouseEvent *event)
+{
+	dragging = false;
+	SliderIgnoreScroll::mouseReleaseEvent(event);
+}
+
+void SliderIgnoreClick::mouseMoveEvent(QMouseEvent *event)
+{
+	if (dragging) {
+		SliderIgnoreScroll::mouseMoveEvent(event);
+	} else {
+		event->accept();
+	}
+}

UI/slider-ignorewheel.hpp

@@ -5,6 +5,7 @@
 #include <QInputEvent>
 #include <QtCore/QObject>
 #include <QAccessibleWidget>
+#include <QStyleOptionSlider>
 
 class SliderIgnoreScroll : public QSlider {
 	Q_OBJECT
@@ -49,3 +50,20 @@ protected:
 	virtual QAccessible::Role role() const override;
 	virtual QString text(QAccessible::Text t) const override;
 };
+
+class SliderIgnoreClick : public SliderIgnoreScroll {
+public:
+	inline SliderIgnoreClick(Qt::Orientation orientation,
+				 QWidget *parent = nullptr)
+		: SliderIgnoreScroll(orientation, parent)
+	{
+	}
+
+protected:
+	virtual void mousePressEvent(QMouseEvent *event) override;
+	virtual void mouseReleaseEvent(QMouseEvent *event) override;
+	virtual void mouseMoveEvent(QMouseEvent *event) override;
+
+private:
+	bool dragging = false;
+};

UI/window-basic-main-transitions.cpp

@@ -797,7 +797,7 @@ void OBSBasic::CreateProgramOptions()
 	mainButtonLayout->addWidget(transitionButton);
 	mainButtonLayout->addWidget(configTransitions);
 
-	tBar = new SliderIgnoreScroll(Qt::Horizontal);
+	tBar = new SliderIgnoreClick(Qt::Horizontal);
 	tBar->setMinimum(0);
 	tBar->setMaximum(T_BAR_PRECISION - 1);