Method scrollDelta

core/scroll.go:219–255

scrollDelta processes a scroll event. If only one dimension is processed, and there is a non-zero in other, then the consumed dimension is reset to 0 and the event is left unprocessed, so a higher level can consume the remainder.

(e events.Event)

// and the event is left unprocessed, so a higher level can consume the
// remainder.
func (fr *Frame) scrollDelta(e events.Event) {
	se := e.(*events.MouseScroll)
	fdel := se.Delta

	hasShift := e.HasAnyModifier(key.Shift, key.Alt) // shift or alt indicates to scroll horizontally
	if hasShift {
		if !fr.HasScroll[math32.X] { // if we have shift, we can only horizontal scroll
			return
		}
		if fr.scrollActionDelta(math32.X, fdel.Y) {
			e.SetHandled()
		}
		return
	}

	if fr.HasScroll[math32.Y] && fr.HasScroll[math32.X] {
		ch1 := fr.scrollActionDelta(math32.Y, fdel.Y)
		ch2 := fr.scrollActionDelta(math32.X, fdel.X)
		if ch1 || ch2 {
			e.SetHandled()
		}
	} else if fr.HasScroll[math32.Y] {
		if fr.scrollActionDelta(math32.Y, fdel.Y) {
			e.SetHandled()
		}
	} else if fr.HasScroll[math32.X] {
		if se.Delta.X != 0 {
			if fr.scrollActionDelta(math32.X, fdel.X) {
				e.SetHandled()
			}
		} else if se.Delta.Y != 0 {
			if fr.scrollActionDelta(math32.X, fdel.Y) {
				e.SetHandled()
			}
		}
	}
}

// parentScrollFrame returns the first parent frame that has active scrollbars.
func (wb *WidgetBase) parentScrollFrame() *Frame {