The break button is used to divide objects along a horizontal or vertical line. The command operates on boxes, polygons, and wires. If one or more of those objects was previously selected, the break command will operate on those selections. Otherwise, the user is asked to select objects to break. The user is then asked to click to divide the selected objects along the break line, which is attached to the pointer and ghost-drawn. The orientation of the break line is either horizontal or vertical, which can be toggled by pressing either the / (forward slash) or \ (backslash) keys when the break line is visible. The break command is useful when one wants to relocate or create a subcell from pieces of an existing design.
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 feature can be controlled from the Edge Snapping group in the Snapping page of the Grid Setup panel.
When the break command is at the state where objects are selected, and the next button press would initiate the break operation, if either of the Backspace or Delete keys is pressed, the command will revert the state back to selecting objects. Then, other objects can be selected or selected objects deselected, and the command is ready to go again. This can be repeated, to build up the set of selections needed.
At any time, pressing the Deselect button to the left of the coordinate readout will revert the command state to the level where objects may be selected to break.
The undo and redo operations (the Tab and Shift-Tab keypreses and Undo/Redo in the Modify Menu) will cycle the command state forward and backward when the command is active. Thus, the last command operation, such as initiating the break by clicking, can be undone and restarted, or redone if necessary. If all command operations are undone, additional undo operations will undo previous commands, as when the undo operation is performed outside of a command. The redo operation will reverse the effect, however when any new modifying operation is started, the redo list is cleared. Thus, for example, if one undoes a box creation, then starts a break operation, the ``redo'' capability of the box creation will be lost.