Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 571

Layer subobjects attributes and methods
Return type: Comp or Footage.
source
Returns the source Comp or source Footage object for the layer. Default time is adjusted to the time in the source.
Example:
source.layer(1).position
Return type: Effect.
effect(name)
Argument type: name is a String.
After Effects finds the effect by its name in the Effect Controls panel. The name can be the default name or a user-
defined name. If there is more than one effect with the same name, the effect closest to the top of the Effect Controls
panel is used. Example:
effect("Fast Blur")("Blurriness")
Return type: Effect.
effect(index)
Argument type: index is a Number.
After Effects finds the effect by its index in the Effect Controls panel, starting at 1 and counting from the top.
Return type: Mask.
mask(name)
Argument type: name is a String.
The name can be the default name or a user-defined name. If there is more than one mask with the same name, the
first (topmost) mask is used. Example:
mask("Mask 1")
Return type: Mask.
mask(index)
Argument type: index is a Number.
After Effects finds the mask by its index in the Timeline panel, starting at 1 and counting from the top.
Layer General attributes and methods
Return type: Number.
width
Returns the width of the layer, in pixels. It is the same as
Return type: Number.
height
Returns the height of the layer, in pixels. It is the same as
Return type: Number.
index
Returns the index number of the layer in the composition.
Return type: Layer, Light, or Camera.
parent
Returns the parent Layer object of the layer, if there is one. Example:
Return type: Boolean.
hasParent
Returns true if the layer has a parent or false if it doesn't.
Use the attribute to determine if a layer has a parent. You can use this attribute even if there isn't a parent
hasParent
layer at present. For example, the following expression indicates that the layer to which you apply it will wiggle based
on the position of the layer's parent. If the layer has no parent, then it will wiggle based on its own position. If the
layer is given a parent later, then the layer's behavior will change accordingly:
.
source.width
.
source.height
position[0] + parent.width
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