The selcp button in the top button menu displays the Selection Control Panel which provides a number of mode switches which control object selection.
There are three ``radio button'' groups. The Pointer Mode group sets the mode for selections initiated with button 1 while outside of commands. There are three choices:
The Area Mode group provides three modes for area (drag-over) selections.
The Selections group modifies how chosen objects are processed.
While selecting, and the Selections group is Normal, during completion of the selection operation, the modifier keys are recognized:
Thus, the Toggle/Add/Remove modes can be established transiently with the modifier keys. For area selection, the normal operation is to toggle the selections. For a point select (mouse click), if more than one underlying object is selected, one of the selected objects is deselected, and there is no new selection.
The Objects group specifies the type of objects that can be selected and deselected with mouse operations. The buttons are labeled Cells, Boxes, Polys, Wires, and Labels. These buttons control whether or not the indicated type of object can be selected or deselected with the mouse. This is useful, for example, when one needs to select cells that are covered by geometric objects, since the geometric objects will always be selected with a mouse click, and not the cells.
Normally, when scanning through the database for objects that are within the selection area, layers are searched from logical top to bottom. The logical top layer is the last layer listed in the layer table (i.e., at the bottom). Thus, in some modes objects on upper layers will be selected preferentially over objects on lower layers. If the Search Up button is active, this ordering is reversed, layers are searched from logical bottom to top, or top to bottom as listed in the layer table.
In the extraction system, the search order will affect the default association of terminals to layers. It also applies to the operations in the Path Selection Control panel.