KB10216 - Difference between Layer.Visible and Layer.Active properties.
A visible layer can be changed inside a project/configuration file and is tested during the Paint procedure. An active layer property is something more important, as it overrides any configuration file settings. For instance, assigning
layer.Active := False
would cause the layer processing to turn off at a much earlier stage, which could mean speed improvement in situations involving management of a lot of hidden layers.
Created: November 21, 2003, Modified: December 18, 2015