Fix #3577: allow the mouse wheel to change volume in the DeskBar widget. Mouse

up increases volume, mouse down decreases it, by 5 at a time.

One issue is you must have the pointer directly over the slider for this to
work. I wonder if the B_POINTER_EVENTS in SetEventMask should also apply to
mouse wheel events?


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29620 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/bin/desklink/VolumeSlider.cpp

@@ -379,6 +379,48 @@ SliderView::Draw(BRect updateRect)
 }
 
 
+void
+SliderView::MessageReceived(BMessage* msg)
+{
+	switch (msg->what) {
+		case B_MOUSE_WHEEL_CHANGED:
+		{
+			if (Value() == -1)
+				return;
+
+			// Even though the volume bar is horizontal, we use the more common
+			// vertical mouse wheel change
+			float deltaY = 0.0f;
+
+			msg->FindFloat("be:wheel_delta_y", &deltaY);
+
+			if (deltaY == 0.0f)
+				return;
+
+			int32 currentValue = Value();
+			// deltaY is generally 1 or -1, so this should increase or decrease
+			// the 0-100 volume value by 5 each time. Also -5 is used because
+			// mousewheel up is negative but should increase the volume.
+			int32 newValue = MAX(MIN(currentValue + static_cast<int32>(deltaY * -5.0), 100), 0);
+
+			if (newValue != currentValue) {
+				SetValue(newValue);
+				Draw(Bounds());
+				Flush();
+
+				if (Window())
+					Window()->PostMessage(VOLUME_UPDATED);
+			}
+
+			break;
+		}
+
+		default:
+			return BView::MessageReceived(msg);
+	}
+}
+
+
 void
 SliderView::MouseDown(BPoint point)
 {
@@ -437,3 +479,4 @@ SliderView::MouseUp(BPoint point)
 	Draw(Bounds());
 	Flush();
 }
+

src/bin/desklink/VolumeSlider.h

@@ -40,6 +40,7 @@ class SliderView : public BControl {
 		~SliderView();
 
 		virtual void Draw(BRect);
+		virtual void MessageReceived(BMessage*);
 		virtual void MouseDown(BPoint point);
 		virtual void MouseMoved(BPoint point, uint32 transit, const BMessage *message);
 		virtual void MouseUp(BPoint point);