Dispatch Action event on Knob when clicking and releasing without moving beyond a threshold distance.

include/app/Knob.hpp

@@ -38,6 +38,10 @@ struct Knob : ParamWidget {
 	void onDragLeave(const DragLeaveEvent& e) override;
 	void onHoverScroll(const HoverScrollEvent& e) override;
 	void onLeave(const LeaveEvent& e) override;
+	/** Called when user clicks the knob without moving it.
+	Useful for handling emulating push-knobs in hardware.
+	*/
+	void onAction(const ActionEvent& e) override {}
 };
 
 

src/app/Knob.cpp

@@ -24,6 +24,8 @@ struct Knob::Internal {
 	/** The mouse has once escaped from the knob while dragging. */
 	bool rotaryDragEnabled = false;
 	float dragAngle = NAN;
+
+	float distDragged = 0.f;
 };
 
 
@@ -83,6 +85,9 @@ void Knob::onDragStart(const DragStartEvent& e) {
 	internal->rotaryDragEnabled = false;
 	internal->dragAngle = NAN;
 
+	// Reset distance dragged
+	internal->distDragged = 0.f;
+
 	ParamWidget::onDragStart(e);
 }
 
@@ -113,6 +118,13 @@ void Knob::onDragEnd(const DragEndEvent& e) {
 	}
 	internal->oldValue = NAN;
 
+	// Dispatch Action event if mouse traveled less than a threshold distance
+	const float actionDistThreshold = 16.f;
+	if (internal->distDragged < actionDistThreshold) {
+		ActionEvent eAction;
+		onAction(eAction);
+	}
+
 	ParamWidget::onDragEnd(e);
 }
 
@@ -213,6 +225,8 @@ void Knob::onDragMove(const DragMoveEvent& e) {
 		pq->setSmoothValue(value);
 	}
 
+	internal->distDragged += e.mouseDelta.norm();
+
 	ParamWidget::onDragMove(e);
 }