Added mouse scrolling to List, Table, TextView, and TreeView.

application.go

@@ -37,10 +37,10 @@ const (
 	MouseRightUp
 	MouseRightClick
 	MouseRightDoubleClick
-	WheelUp
-	WheelDown
-	WheelLeft
-	WheelRight
+	MouseScrollUp
+	MouseScrollDown
+	MouseScrollLeft
+	MouseScrollRight
 )
 
 // queuedUpdate represented the execution of f queued by
@@ -467,10 +467,10 @@ func (a *Application) fireMouseActions(event *tcell.EventMouse) (consumed, isMou
 		button tcell.ButtonMask
 		action MouseAction
 	}{
-		{tcell.WheelUp, WheelUp},
-		{tcell.WheelDown, WheelDown},
-		{tcell.WheelLeft, WheelLeft},
-		{tcell.WheelRight, WheelRight}} {
+		{tcell.WheelUp, MouseScrollUp},
+		{tcell.WheelDown, MouseScrollDown},
+		{tcell.WheelLeft, MouseScrollLeft},
+		{tcell.WheelRight, MouseScrollRight}} {
 		if buttons&wheelEvent.button != 0 {
 			fire(wheelEvent.action)
 		}

list.go

@@ -560,7 +560,7 @@ func (l *List) InputHandler() func(event *tcell.EventKey, setFocus func(p Primit
 }
 
 // indexAtPoint returns the index of the list item found at the given position
-// or -1 if there is no such list item.
+// or a negative value if there is no such list item.
 func (l *List) indexAtPoint(x, y int) int {
 	rectX, rectY, width, height := l.GetInnerRect()
 	if rectX < 0 || rectX >= rectX+width || y < rectY || y >= rectY+height {
@@ -571,6 +571,7 @@ func (l *List) indexAtPoint(x, y int) int {
 	if l.showSecondaryText {
 		index /= 2
 	}
+	index += l.offset
 
 	if index >= len(l.items) {
 		return -1
@@ -586,7 +587,8 @@ func (l *List) MouseHandler() func(action MouseAction, event *tcell.EventMouse,
 		}
 
 		// Process mouse event.
-		if action == MouseLeftClick {
+		switch action {
+		case MouseLeftClick:
 			setFocus(l)
 			index := l.indexAtPoint(event.Position())
 			if index != -1 {
@@ -603,6 +605,20 @@ func (l *List) MouseHandler() func(action MouseAction, event *tcell.EventMouse,
 				l.currentItem = index
 			}
 			consumed = true
+		case MouseScrollUp:
+			if l.offset > 0 {
+				l.offset--
+			}
+			consumed = true
+		case MouseScrollDown:
+			lines := len(l.items) - l.offset
+			if l.showSecondaryText {
+				lines *= 2
+			}
+			if _, _, _, height := l.GetInnerRect(); lines > height {
+				l.offset++
+			}
+			consumed = true
 		}
 
 		return

table.go

@@ -1242,6 +1242,13 @@ func (t *Table) MouseHandler() func(action MouseAction, event *tcell.EventMouse,
 			}
 			consumed = true
 			setFocus(t)
+		case MouseScrollUp:
+			t.trackEnd = false
+			t.rowOffset--
+			consumed = true
+		case MouseScrollDown:
+			t.rowOffset++
+			consumed = true
 		}
 
 		return

textview.go

@@ -1164,6 +1164,13 @@ func (t *TextView) MouseHandler() func(action MouseAction, event *tcell.EventMou
 			}
 			consumed = true
 			setFocus(t)
+		case MouseScrollUp:
+			t.trackEnd = false
+			t.lineOffset--
+			consumed = true
+		case MouseScrollDown:
+			t.lineOffset++
+			consumed = true
 		}
 
 		return

treeview.go

@@ -757,6 +757,12 @@ func (t *TreeView) MouseHandler() func(action MouseAction, event *tcell.EventMou
 			}
 			consumed = true
 			setFocus(t)
+		case MouseScrollUp:
+			t.movement = treeUp
+			consumed = true
+		case MouseScrollDown:
+			t.movement = treeDown
+			consumed = true
 		}
 
 		return