Scrollbars accept both directions of scroll

heading.go

@@ -18,6 +18,8 @@ func NewHeading (level int, text string) *Heading {
 	this.SetRole(tomo.R("objects", "Heading"))
 	this.SetTag(fmt.Sprint(level), true)
 	this.SetText(text)
+	this.SetSelectable(true)
+	this.SetFocusable(true)
 	return this
 }
 

label.go

@@ -13,5 +13,7 @@ func NewLabel (text string) *Label {
 	this.SetRole(tomo.R("objects", "Label"))
 	this.SetText(text)
 	this.SetAttr(tomo.AAlign(tomo.AlignStart, tomo.AlignMiddle))
+	this.SetSelectable(true)
+	this.SetFocusable(true)
 	return this
 }

scrollbar.go

@@ -235,6 +235,16 @@ func (this *Scrollbar) handleMouseMove () bool {
 
 func (this *Scrollbar) handleScroll (x, y float64) bool {
 	if this.layout.linked == nil { return false }
+	
+	delta := (x + y)
+	if this.layout.vertical {
+		x = 0
+		y = delta
+	} else {
+		x = delta
+		y = 0
+	}
+	
 	this.layout.linked.ScrollTo (
 		this.layout.linked.ContentBounds().Min.
 		Sub(image.Pt(int(x), int(y))))