Function HandleScrollbarScrolling

src/window.cpp:2367–2401

* Handle scrollbar scrolling with the mouse. * @param w window with active scrollbar. */

 * @param w window with active scrollbar.
 */
static void HandleScrollbarScrolling(Window *w)
{
	int i;
	NWidgetScrollbar *sb = w->GetWidget<NWidgetScrollbar>(w->mouse_capture_widget);
	bool rtl = false;

	if (sb->type == NWID_HSCROLLBAR) {
		i = _cursor.pos.x - _cursorpos_drag_start.x;
		rtl = _current_text_dir == TD_RTL;
	} else {
		i = _cursor.pos.y - _cursorpos_drag_start.y;
	}

	if (sb->disp_flags.Any({NWidgetDisplayFlag::ScrollbarUp, NWidgetDisplayFlag::ScrollbarDown})) {
		if (_scroller_click_timeout == 1) {
			_scroller_click_timeout = 3;
			if (sb->UpdatePosition(rtl == sb->disp_flags.Test(NWidgetDisplayFlag::ScrollbarUp) ? 1 : -1)) {
				w->OnScrollbarScroll(w->mouse_capture_widget);
				w->SetDirty();
			}
		}
		return;
	}

	/* Find the item we want to move to. SetPosition will make sure it's inside bounds. */
	int range = sb->GetCount() - sb->GetCapacity();
	if (range <= 0) return;

	int pos = RoundDivSU((i + _scrollbar_start_pos) * range, std::max(1, _scrollbar_size));
	if (rtl) pos = range - pos;
	if (sb->SetPosition(pos)) {
		w->OnScrollbarScroll(w->mouse_capture_widget);
		w->SetDirty();
	}
}

/**
 * Handle active widget (mouse dragging on widget) with the mouse.