UI: Move VolumeSlider widget to volume control

UI/volume-control.cpp

@@ -1518,3 +1518,77 @@ void VolumeMeterTimer::timerEvent(QTimerEvent *)
 		}
 	}
 }
+
+VolumeSlider::VolumeSlider(obs_fader_t *fader, QWidget *parent)
+	: SliderIgnoreScroll(parent)
+{
+	fad = fader;
+}
+
+VolumeSlider::VolumeSlider(obs_fader_t *fader, Qt::Orientation orientation,
+			   QWidget *parent)
+	: SliderIgnoreScroll(orientation, parent)
+{
+	fad = fader;
+}
+
+VolumeAccessibleInterface::VolumeAccessibleInterface(QWidget *w)
+	: QAccessibleWidget(w)
+{
+}
+
+VolumeSlider *VolumeAccessibleInterface::slider() const
+{
+	return qobject_cast<VolumeSlider *>(object());
+}
+
+QString VolumeAccessibleInterface::text(QAccessible::Text t) const
+{
+	if (slider()->isVisible()) {
+		switch (t) {
+		case QAccessible::Text::Value:
+			return currentValue().toString();
+		default:
+			break;
+		}
+	}
+	return QAccessibleWidget::text(t);
+}
+
+QVariant VolumeAccessibleInterface::currentValue() const
+{
+	QString text;
+	float db = obs_fader_get_db(slider()->fad);
+
+	if (db < -96.0f)
+		text = "-inf dB";
+	else
+		text = QString::number(db, 'f', 1).append(" dB");
+
+	return text;
+}
+
+void VolumeAccessibleInterface::setCurrentValue(const QVariant &value)
+{
+	slider()->setValue(value.toInt());
+}
+
+QVariant VolumeAccessibleInterface::maximumValue() const
+{
+	return slider()->maximum();
+}
+
+QVariant VolumeAccessibleInterface::minimumValue() const
+{
+	return slider()->minimum();
+}
+
+QVariant VolumeAccessibleInterface::minimumStepSize() const
+{
+	return slider()->singleStep();
+}
+
+QAccessible::Role VolumeAccessibleInterface::role() const
+{
+	return QAccessible::Role::Slider;
+}