# Layer Link

- Object

Add objects to the layer or move the layer to another window.

### Hierarchy

Layers can be linked to objects above or below, in the Gamgi hierarchy. Pressing the button Below (the default), the Objects menu shows the classes of objects that can be owned by layers: Assembliy, Light, Cell, Cluster, Molecule, Group, Plane, Direction, Atom (the default), Orbital and Text. Pressing the button Above, the same menu shows the only class of objects that can own layers: Window.

### Object

Gamgi expects users to identify first the layer or list of layers and then the object to link. When the Layer entry is active and empty, pressing the mouse over the graphic area in the current window (local selection) creates a menu with all the layers in the window, which can then be selected. Initially, the identification of the current layer is entered in the Layer entry.

Gamgi is now expecting users to click on a object of the class currently selected in the Object menu. This object can be in a different layer or even in a different window (global selection). To select a visible object in a different layer, in the same window, just press the mouse over the object, as if it was in the current layer. To select objects without visual representation, as windows and lights, press the mouse over the graphic area in a window, to create a menu with all the objects of that class in the window (when the class is Light) or in Gamgi (when the class is Window), which can then be selected. To select an object in a different window, with the mouse, use exactly the same procedure, in that window.

### Link

Gamgi suppports only one type of linking mode for Layer: Object.

The Object method links a layer to a single Object. When the Hierarchy is Above, the layer is unlinked from its previous window and linked to the new window. The layer history kept by the Undo and Save mechanisms is preserved in this operation. When the Hierarchy is Below, the object is unlinked from its current parent and linked to the layer. An error is issued when the parent already owned the child object.

After the linking operation, Gamgi always puts on top the window and layer containing the linked objects.
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