3.6 Layer

Layers are like transparent sheets laying op top of each other, with objects glued to them.

The layer order determines the drawing order of the objects, although there is a second drawing order, that of the objects of each layer. Within a layer, objects can be moved to the front or to the back of the layer. The layer itself can be moved in front of or behind other layers.

The next figure shows a drawing where some of the layers are dimmed. Each layer can be in one of the following modes

• editable (same as selectable)
• visible
• dimmed
• invisible

So, for example, to create the situation in 4D Draw, you would have

• one layer with mode invisible for "hidden objects"
• one layer with mode visible that serves as "background"
• one layer with mode editable on top of it that serves as "foreground".

Of course, 4D CAD gives you more power to work with layers than 4D Draw does. Other attributes of a layer are

• the layer’s ID, a number (of type longint) that uniquely identifies it
• the layer’s name. The name of a layer need not be unique, but there is a special case. When pasting objects from other areas, the layer’s name and its unmasked keys, identify the layer, see Copy and paste and Keys
• the layer’s transparency flag. A transparent layer automaticaly shows all solid and background object fills as if they were transparent (see Fill)
• the layer’s hatching flag. Objects on a non-hatching layer don’t show hatches (see Hatch)
• the layer’s snapping flag. Objects on a non-snapping layer don’t snap (see Snaps). By default, the layer’s mode determines whether a layer snaps. You can reset the minimum mode where a layer snaps with CADSetSnapPrefs and then maintain the snapping flag of each layer by calling CADSetLayerAttributes This is useful when you want to add invisible snapping points or an invisible snapping grid
• the layer’s keys can be used to further identify the layer, for example to distinguish between user layers and application specific layers, see Keys
• the layer’s sublayers, see Sublayer
• whether it is the Current layer or not.

A layer ID passed as a Scope ID, describes all objects on the layer.

Methods
CADAddLayer, CADRemoveLayer, CADGetLayers, CADGetLayerAttributes, CADSetLayerAttributes, CADGetLayerKey, CADSetLayerKey, CADGetLayerOrder, CADSetLayerOrder, CADGetCurrentLayer, CADSetCurrentLayer, CADGetSnapPrefs, CADSetSnapPrefs.