if (this->engines[0].NeedRebuild()) {

			/* We need to rebuild the left engines list */

			this->GenerateReplaceVehList(true);

			if (this->reset_sel_engine && this->sel_engine[0] == INVALID_ENGINE && this->engines[0].size() != 0) {

				this->sel_engine[0] = this->engines[0][0].engine_id;

			}

				}

				/* Regenerate the list on the right. Note: This resets sel_engine[1] to INVALID_ENGINE, if it is no longer available. */

				this->GenerateReplaceVehList(false);

				if (this->reset_sel_engine && this->sel_engine[1] != INVALID_ENGINE) {

					int position = 0;

					for (const auto &item : this->engines[1]) {

		this->bridges->NeedResort();

		this->SortBridgeList();

	}

	~BuildBridgeWindow()

	void OnPaint() override

	{

		this->GenerateBuildList();

		this->SetWidgetsDisabledState(this->sel_engine == INVALID_ENGINE, WID_BV_SHOW_HIDE, WID_BV_BUILD, WIDGET_LIST_END);

				max_width = std::max(max_width, width);

			}

			/* Always have 1 empty row, so people can change the setting of the train */

			/* Always make it longer than the longest train, so you can attach vehicles at the end, and also see the next vertical tile separator line */

			this->hscroll->SetCount(max_width + ScaleSpriteTrad(2 * VEHICLEINFO_FULL_VEHICLE_WIDTH + 1));

		} else {

				_fios_path_changed = true;

				this->fios_items.BuildFileList(this->abstract_filetype, this->fop);

				this->selected = nullptr;

				_load_check_data.Clear();

			}

		}

	}

	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override

		this->CreateNestedTree();

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

		/* Initialise the dataset */

		this->UpdatePaymentRates();

		this->groups.ForceRebuild();

		this->groups.NeedResort();

		this->BuildGroupList(vli.company);

		this->GetWidget<NWidgetCore>(WID_GL_CAPTION)->widget_data = STR_VEHICLE_LIST_TRAIN_CAPTION + this->vli.vtype;

		this->GetWidget<NWidgetCore>(WID_GL_LIST_VEHICLE)->tool_tip = STR_VEHICLE_LIST_TRAIN_LIST_TOOLTIP + this->vli.vtype;

		this->BuildGroupList(this->owner);

		/* The drop down menu is out, *but* it may not be used, retract it. */

		if (this->vehicles.size() == 0 && this->IsWidgetLowered(WID_GL_MANAGE_VEHICLES_DROPDOWN)) {

				}

				this->groups.ForceRebuild();

				this->BuildGroupList(this->owner);

				id_g = find_index(this->groups, g);

			}

			this->group_sb->ScrollTowards(id_g);

		this->UpdateAvailability();

	}

	/** Update status of the fund and display-chain widgets. */

		IndustryDirectoryWindow::produced_cargo_filter = this->cargo_filter[this->produced_cargo_filter_criteria];

		this->industries.Sort();

		this->SetDirty();

	}

		this->content.RebuildDone();

		this->SortContentList();

		this->ScrollToSelected();

	}

		this->servers.shrink_to_fit();

		this->servers.RebuildDone();

		/* Sort the list of network games as requested. */

		this->servers.Sort();

		if (data == 1) {

			/* Sprite picker finished */

			this->RaiseWidget(WID_SA_PICKER);

		}

	}

			}

		}

	}

	/**

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

		this->FinishInitNested(0);

		this->SetFocusedWidget(WID_SVP_EDITBOX);

		if (initial_text != nullptr) this->presetname_editbox.text.Assign(initial_text);

	}

		ResetObjectToPlace();

		EnsureSelectedObjectClassIsVisible();

		this->object_classes.RebuildDone();

		this->object_classes.Sort();

	}

	/**

			if (station_class == _railstation.station_class) break;

			pos++;

		}

		this->vscroll->ScrollTowards(pos);

	}

			this->station_classes.RebuildDone();

			this->station_classes.Sort();

		}

	}

			if (rs_class == _roadstop_gui_settings.roadstop_class) break;

			pos++;

		}

		this->vscrollList->ScrollTowards(pos);

	}

			this->roadstop_classes.RebuildDone();

			this->roadstop_classes.Sort();

		}

	}

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

		this->FinishInitNested(); // Initializes 'this->line_height' as side effect.

		/* Try if we can find the currently selected AI */

		this->selected = -1;

		if (!gui_scope) return;

		/* selected goes from -1 .. length of ai list - 1. */

		this->selected = std::min(this->selected, this->vscroll->GetCount() - 2);

			}

		}

	}

	void SetStringParameters(int widget) const override

		this->SelectValidDebugCompany();

		/* Update company buttons */

		for (CompanyID i = COMPANY_FIRST; i < MAX_COMPANIES; i++) {

	{

		if (this->signs.NeedRebuild()) {

			this->BuildSignsList();

			this->SetWidgetDirty(WID_SIL_CAPTION);

		}

		this->SortSignsList();

		this->stations.shrink_to_fit();

		this->stations.RebuildDone();

	}

	/** Sort stations by their name */

	{

		if (!gui_scope) return;

		FindStationsNearby<T>(this->area, true);

		this->SetDirty();

	}

			this->towns.shrink_to_fit();

			this->towns.RebuildDone();

		}

		/* Always sort the towns. */

		this->towns.Sort();

	}

	this->vehgroups.RebuildDone();

}

	 * Set the distance to scroll when using the buttons or the wheel.

	 * @param stepsize Scrolling speed.

	 */

	{

		assert(stepsize > 0);

	}

	/**

	 * @param num the number of elements in the list

	 * @note updates the position if needed

	 */

	{

		assert(num <= MAX_UVALUE(uint16));

		num -= this->cap;

		if (num < 0) num = 0;

		if (num < this->pos) this->pos = num;

	 * @param capacity the new capacity

	 * @note updates the position if needed

	 */

	{

		assert(capacity <= MAX_UVALUE(uint16));

		if (this->cap + this->pos > this->count) this->pos = std::max(0, this->count - this->cap);

	}

		}

		/* Capacity is the average number of items visible */

		this->parent_wnd_class = parent->window_class;

		this->parent_wnd_num   = parent->window_number;