When one or more objects are selected, activating the plugin generates a polygon memory layer containing a "mask" whose dimension is twice area of the current view.
The mask is a gray box, with holes in order to highlight the underlying objects
For advanced users, uou can trigger the creation of masks from the python console
# import plugin
from mask import aeag_mask
# Classic call : mask the selected features
aeag_mask.do()
# mask all features of selected layer, extent depends on the current extent.
# All news 'mask' features are stored in a unique layer, attributes of the original layer are duplicated
aeag_mask.do(False)
# mask all features of selected layer, specific extent (attributes of the original layer are duplicated).
aeag_mask.do(False, QgsRectangle (356419,6120047, 1051423,6595985))