The box command button allows creation of boxes (rectangles) on the currently selected layer. The box can be defined by either clicking button 1 on two diagonal corners, or by pressing button 1 to define the first corner, dragging, then releasing button 1 to define the second corner. The outline of the box is ghost-drawn during creation. The new box will be merged with or clipped to existing boxes on the same layer, unless this feature has been suppressed.
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.
In physical mode, boxes can also be created from the Show/Select Devices panel from the Device Selections button in the Extract Menu. The Enable Measure Box button provides a means of creating boxes of a specific size to match electrical requirements, for example to create rectangular resistor bodies for a given resistance. Boxes can be created whether or not the electrical layer parameters are used or present.
In physical mode while the box command is active, holding down the Ctrl key while clicking on a subcell will paint the area of the subcell with the current layer.
In electrical mode, the box command is available by selecting the box function in the shapes menu. If the current layer is the SCED layer, the box will be created using the ETC2 layer, otherwise the box will be created on the current layer. It is best to avoid use of the SCED layer for other than active wires, for efficiency reasons, though it is not an error. The Change Layer command in the Modify Menu can be used to change the layer of existing objects to the SCED layer, if necessary. The outline style and fill will be those of the rendering layer. Boxes have no electrical significance, but can be used for illustrative purposes.
The box, erase, and xor commands participate in a protocol that is handy on occasion.
Suppose that you want to erase an area, and you have zoomed in and clicked to define the anchor, then zoomed out or panned and clicked to finish the operation. Oops, the box command was active, not erase. One can press Tab to undo the unwanted new box, then press the erase button, and the erase command will have the same anchor point and will be showing the ghost box, so clicking once will finish the erase operation.
The anchor point is remembered, when switching directly between these three commands, and the command being exited is in the state where the anchor point is defined, and the ghost box is being displayed. One needs to press the command button in the side menu to switch commands. If Esc is pressed, or a non-participating command is entered, the anchor point will be lost.