Menu concepts

  The manager has got a list of layers (see 9.1.3.16), where each layer is a independent part of the manager. Each layer, which is a subclass of group (see 9.1.3.12), can contain several objects or is a total menu itself. A layer is added to and removed from the manager with the methods "add-layer" 9.1.3.17 and "remove-layer" 9.1.3.17. The layers of the handle are comparable with the windows of graphical user interfaces like X11 and the layers have a similar using mechanism: Each one can be moved, sized and iconized. The menus of GRAPE are implemented as groups (9.1.3.12), which must be inserted into a layer of the manager. A group contains several items, but it can be handled like one single item from the superior groups and layers. If you start up a GRAPE program the standard manager consists of single layer which contains only a selector and a textmessage. The selector will then add the group, which contains all control-elements of the manag-menu (see 4.3.4), to the layer. If a different standard-menu is selected, for example the trans-menu (see 4.3.8), the selector will remove the manag-group from the layer and will add the trans-group. Pay attention that no different layers are used up to now. A layer is part of the menu, which will overlay the normal menu, for example the layer, which contains the project-add list or the file lists. If a layer depends upon another item of the normal menu structure it will be removed as well if the item is removed from the menu structure and will be added again automatically.