Knob: hide cursor on wheel event for .8s

src/widget/knobeventhandler.h

@@ -1,22 +1,28 @@
 #pragma once
 
-#include <QMouseEvent>
-#include <QWheelEvent>
-#include <QColor>
 #include <QCursor>
-#include <QPoint>
+#include <QMouseEvent>
 #include <QPixmap>
+#include <QPoint>
+#include <QTimer>
+#include <QWheelEvent>
 
 #include "util/math.h"
 
+// duration (ms) the cursor is blanked after a mouse wheel event
+// 800 ms is the duration the parameter value is shown in the parameter name widget
+// src/widget/weffectparameternamebase.cpp
+constexpr int wheelEventCursorTimeout = 800;
+
 template <class T>
 class KnobEventHandler {
   public:
     KnobEventHandler()
-            : m_bRightButtonPressed(false) {
-            QPixmap blankPixmap(32, 32);
-            blankPixmap.fill(QColor(0, 0, 0, 0));
-            m_blankCursor = QCursor(blankPixmap);
+            : m_bRightButtonPressed(false),
+              m_pWheelCursorTimer(nullptr) {
+        QPixmap blankPixmap(32, 32);
+        blankPixmap.fill(Qt::transparent);
+        m_blankCursor = QCursor(blankPixmap);
     }
 
     double valueFromMouseEvent(T* pWidget, QMouseEvent* e) {
@@ -103,6 +109,9 @@ class KnobEventHandler {
     }
 
     void wheelEvent(T* pWidget, QWheelEvent* e) {
+        // Hide/blank the cursor so the parameter value below the knob is not obscured.
+        // Restore the cursor when the timer runs out, or when the cursor leaves the widget.
+        pWidget->setCursor(m_blankCursor);
         // For legacy (MIDI) reasons this is tuned to 127.
         double wheelDirection = e->angleDelta().y() / (120.0 * 127.0);
         double newValue = pWidget->getControlParameter() + wheelDirection;
@@ -113,6 +122,26 @@ class KnobEventHandler {
         pWidget->setControlParameter(newValue);
         pWidget->inputActivity();
         e->accept();
+        if (!m_pWheelCursorTimer) {
+            m_pWheelCursorTimer = new QTimer(pWidget);
+            m_pWheelCursorTimer->setSingleShot(true);
+            m_pWheelCursorTimer->setInterval(wheelEventCursorTimeout);
+        }
+        m_pWheelCursorTimer->start();
+        m_pWheelCursorTimer->callOnTimeout(
+                [pWidget]() {
+                    if (pWidget) {
+                        pWidget->unsetCursor();
+                    }
+                });
+    }
+
+    void leaveEvent(T* pWidget, QEvent* e) {
+        if (m_pWheelCursorTimer && m_pWheelCursorTimer->isActive()) {
+            m_pWheelCursorTimer->stop();
+            pWidget->unsetCursor();
+        }
+        e->accept();
     }
 
   private:
@@ -123,4 +152,5 @@ class KnobEventHandler {
     QPoint m_startPos;
     QPoint m_prevPos;
     QCursor m_blankCursor;
+    QTimer* m_pWheelCursorTimer;
 };

src/widget/wknob.cpp

@@ -38,6 +38,10 @@ void WKnob::wheelEvent(QWheelEvent* e) {
     m_handler.wheelEvent(this, e);
 }
 
+void WKnob::leaveEvent(QEvent* e) {
+    m_handler.leaveEvent(this, e);
+}
+
 void WKnob::inputActivity() {
 #ifdef __APPLE__
     m_renderTimer.activity();

src/widget/wknob.h

@@ -21,6 +21,7 @@ class WKnob : public WDisplay {
 
   protected:
     void wheelEvent(QWheelEvent *e) override;
+    void leaveEvent(QEvent* e) override;
     void mouseMoveEvent(QMouseEvent *e) override;
     void mousePressEvent(QMouseEvent *e) override;
     void mouseDoubleClickEvent(QMouseEvent* e) override;

src/widget/wknobcomposed.cpp

@@ -227,6 +227,10 @@ void WKnobComposed::wheelEvent(QWheelEvent* e) {
     m_handler.wheelEvent(this, e);
 }
 
+void WKnobComposed::leaveEvent(QEvent* e) {
+    m_handler.leaveEvent(this, e);
+}
+
 void WKnobComposed::inputActivity() {
 #ifdef __APPLE__
     m_renderTimer.activity();

src/widget/wknobcomposed.h

@@ -28,6 +28,7 @@ class WKnobComposed : public WWidget {
 
   protected:
     void wheelEvent(QWheelEvent *e) override;
+    void leaveEvent(QEvent* e) override;
     void mouseMoveEvent(QMouseEvent *e) override;
     void mousePressEvent(QMouseEvent *e) override;
     void mouseDoubleClickEvent(QMouseEvent* e) override;