Method UpdateListPositionOnKeyPress

src/widget.cpp:2474–2517

* Update the given list position as if it were on this scroll bar when the given keycode was pressed. * This does not update the actual position of this scroll bar, that is left to the caller. It does, * however use the capacity and count of the scroll bar for the bounds and amount to scroll. * * When the count is 0 or the return is ES_NOT_HANDLED, then the position is not updated. * With WKC

 * @return ES_NOT_HANDLED when another key than the 6 specific keys was pressed, otherwise ES_HANDLED.
 */
EventState Scrollbar::UpdateListPositionOnKeyPress(int &list_position, uint16_t keycode) const
{
	int new_pos = list_position;
	switch (keycode) {
		case WKC_UP:
			/* scroll up by one */
			new_pos--;
			break;

		case WKC_DOWN:
			/* scroll down by one */
			new_pos++;
			break;

		case WKC_PAGEUP:
			/* scroll up a page */
			new_pos -= this->GetCapacity();
			break;

		case WKC_PAGEDOWN:
			/* scroll down a page */
			new_pos += this->GetCapacity();
			break;

		case WKC_HOME:
			/* jump to beginning */
			new_pos = 0;
			break;

		case WKC_END:
			/* jump to end */
			new_pos = this->GetCount() - 1;
			break;

		default:
			return ES_NOT_HANDLED;
	}

	/* If there are no elements, there is nothing to scroll/update. */
	if (this->GetCount() != 0) {
		list_position = Clamp(new_pos, 0, this->GetCount() - 1);
	}
	return ES_HANDLED;
}


/**