/**

 * Make a number of rows with button-like graphics, for enabling/disabling each company.

 * @param biggest_index Storage for collecting the biggest index used in the returned tree.

 * @return Panel with rows of company buttons.

 * @post \c *biggest_index contains the largest used index in the tree.

 */

static NWidgetBase *MakeCompanyButtonRows(int *biggest_index)

	static const int MAX_LENGTH = 8; // Maximal number of company buttons in one row.

	NWidgetVertical *vert = NULL; // Storage for all rows.

	NWidgetHorizontal *hor = NULL; // Storage for buttons in one row.

	int hor_length = 0;

	Dimension sprite_size = GetSpriteSize(SPR_COMPANY_ICON);

	sprite_size.width  += WD_MATRIX_LEFT + WD_MATRIX_RIGHT;

	sprite_size.height += WD_MATRIX_TOP + WD_MATRIX_BOTTOM + 1; // 1 for the 'offset' of being pressed

	for (int widnum = PRW_COMPANY_FIRST; widnum <= PRW_COMPANY_LAST; widnum++) {

		/* Ensure there is room in 'hor' for another button. */

		if (hor_length == MAX_LENGTH) {

			if (vert == NULL) vert = new NWidgetVertical();

			vert->Add(hor);

			hor = NULL;

			hor_length = 0;

		}

		if (hor == NULL) {

			hor = new NWidgetHorizontal();

			hor_length = 0;

		}

		NWidgetBackground *panel = new NWidgetBackground(WWT_PANEL, COLOUR_GREY, widnum);

		panel->SetMinimalSize(sprite_size.width, sprite_size.height);

		panel->SetFill(1, 0);

		panel->SetDataTip(0x0, STR_PERFORMANCE_DETAIL_SELECT_COMPANY_TOOLTIP);

		hor->Add(panel);

		hor_length++;

	}

	*biggest_index = PRW_COMPANY_LAST;

	if (vert == NULL) return hor; // All buttons fit in a single row.

	if (hor_length > 0 && hor_length < MAX_LENGTH) {

		/* Last row is partial, add a spacer at the end to force all buttons to the left. */

		NWidgetSpacer *spc = new NWidgetSpacer(0, 0);

		spc->SetMinimalSize(sprite_size.width, sprite_size.height);

		spc->SetFill(1, 0);

		hor->Add(spc);

	}

	if (hor != NULL) vert->Add(hor);

	return vert;

		NWidgetFunction(MakeCompanyButtonRows), SetPadding(0, 1, 1, 2),