ScrollContainer can step scroll with normal up/down

scrollcontainer.go

@@ -210,6 +210,22 @@ func (this *ScrollContainer) handleKeyDown (key input.Key, numpad bool) bool {
 		}
 		this.scrollBy(vector)
 		return true
+	case input.KeyUp:
+		if modifiers.Shift {
+			vector.X -= this.StepSize().X
+		} else {
+			vector.Y -= this.StepSize().Y
+		}
+		this.scrollBy(vector)
+		return true
+	case input.KeyDown:
+		if modifiers.Shift {
+			vector.X += this.StepSize().X
+		} else {
+			vector.Y += this.StepSize().Y
+		}
+		this.scrollBy(vector)
+		return true
 	}
 	return false
 }