C++ DropDownList::Begin方法代码示例

	/**
	 * Find the dropdown item under the cursor.
	 * @param value [out] Selected item, if function returns \c true.
	 * @return Cursor points to a dropdown item.
	 */
	bool GetDropDownItem(int &value)
	{
		if (GetWidgetFromPos(this, _cursor.pos.x - this->left, _cursor.pos.y - this->top) < 0) return false;

		NWidgetBase *nwi = this->GetWidget<NWidgetBase>(WID_DM_ITEMS);
		int y     = _cursor.pos.y - this->top - nwi->pos_y - 2;
		int width = nwi->current_x - 4;
		int pos   = this->vscroll->GetPosition();

		const DropDownList *list = this->list;

		for (const DropDownListItem * const *it = list->Begin(); it != list->End(); ++it) {
			/* Skip items that are scrolled up */
			if (--pos >= 0) continue;

			const DropDownListItem *item = *it;
			int item_height = item->Height(width);

			if (y < item_height) {
				if (item->masked || !item->Selectable()) return false;
				value = item->result;
				return true;
			}

			y -= item_height;
		}

		return false;
	}

	/**
	 * Create a dropdown menu.
	 * @param parent        Parent window.
	 * @param list          Dropdown item list.
	 * @param selected      Index of the selected item in the list.
	 * @param button        Widget of the parent window doing the dropdown.
	 * @param instant_close Close the window when the mouse button is raised.
	 * @param position      Topleft position of the dropdown menu window.
	 * @param size          Size of the dropdown menu window.
	 * @param wi_colour     Colour of the parent widget.
	 * @param scroll        Dropdown menu has a scrollbar.
	 * @param widget        Widgets of the dropdown menu window.
	 */
	DropdownWindow(Window *parent, const DropDownList *list, int selected, int button, bool instant_close, const Point &position, const Dimension &size, Colours wi_colour, bool scroll)
			: Window(&_dropdown_desc)
	{
		assert(list->Length() > 0);

		this->position = position;

		this->CreateNestedTree();

		this->vscroll = this->GetScrollbar(WID_DM_SCROLL);

		uint items_width = size.width - (scroll ? NWidgetScrollbar::GetVerticalDimension().width : 0);
		NWidgetCore *nwi = this->GetWidget<NWidgetCore>(WID_DM_ITEMS);
		nwi->SetMinimalSize(items_width, size.height + 4);
		nwi->colour = wi_colour;

		nwi = this->GetWidget<NWidgetCore>(WID_DM_SCROLL);
		nwi->colour = wi_colour;

		this->GetWidget<NWidgetStacked>(WID_DM_SHOW_SCROLL)->SetDisplayedPlane(scroll ? 0 : SZSP_NONE);

		this->FinishInitNested(0);
		CLRBITS(this->flags, WF_WHITE_BORDER);

		/* Total length of list */
		int list_height = 0;
		for (const DropDownListItem * const *it = list->Begin(); it != list->End(); ++it) {
			const DropDownListItem *item = *it;
			list_height += item->Height(items_width);
		}

		/* Capacity is the average number of items visible */
		this->vscroll->SetCapacity(size.height * (uint16)list->Length() / list_height);
		this->vscroll->SetCount((uint16)list->Length());

		this->parent_wnd_class = parent->window_class;
		this->parent_wnd_num   = parent->window_number;
		this->parent_button    = button;
		this->list             = list;
		this->selected_index   = selected;
		this->click_delay      = 0;
		this->drag_mode        = instant_close;
		this->instant_close    = instant_close;
		this->left_button_state = _left_button_down;
	}