The polyg button is used to create and modify polygons. In electrical mode, this functionality is available from the poly menu selection brought up by the shapes button. When A polygon is created by clicking on each vertex in sequence, and is terminated by clicking again on the initial vertex, or clicking on the final vertex twice. The vertices can be undone and redone with the Tab key and Shift-Tab combination, which are equivalent to the Undo and Redo commands.
While the command is active in physical mode, the cursor will snap to horizontal or vertical edges of existing objects in the layout if the edge is on-grid, when within two pixels. When snapped, a small dotted highlight box is displayed. This makes it much easier to create abutting objects when the grid snap spacing is very fine compared with the display scaling. This is also applied to the first vertex of polygons being created, facilitating point list termination. This feature can be disabled by setting the NoSnapToEdges variable.
When adding vertices during polygon creation, the angle of each segment can be constrained to a multiple of 45 degrees with the Constrain 45 button in the Attributes Menu, in conjunction with the Shift and Ctrl keys. There are three modes: call them ``no45'' for no constraint, ``reg45'' for constraint to multiples of 45 degrees with automatic generation of the segment from the end of the 45 section to the actual point, and ``simp45'' that does no automatic segment generation. The ``reg45'' algorithm adds a 45 degree segment plus possibly an additional Manhattan segment to connect the given point. The ``simp45'' adds only the 45 degree segment. The mode employed at a given time is given by the table below.
Constrain 45 not set | ||
Shift up | Shift pressed | |
Ctrl up | no45 | reg45 |
Ctrl pressed | simp45 | simp45 |
Constrain 45 set | ||
Shift up | Shift pressed | |
Ctrl up | reg45 | no45 |
Ctrl pressed | simp45 | no45 |
In physical mode, a new polygon is tested for reentrancy and other problems, and a warning message is issued if a pathology is detected. The new polygon is not removed from the database if such an error is detected. It is up to the user to make appropriate changes.
In electrical mode, polygons have no electrical significance, but can be used for illustrative purposes.