The layer table is arrayed vertically to the left of the main drawing window. If layers have been specified to Xic, they will be shown in this area. If there are more layers than space available for display, a scroll bar is provided. There is no limit on the number of layers that can be defined in Xic. Separate layer tables are provided for electrical and physical modes.
The ``grip'' that separates the layer table from the main drawing window can be dragged to change the layer table width.
To the left of each entry sample box are indicators that when clicked on will toggle either the visibility or selectability of that layer. If the layer is not visible, objects on that layer will not be shown in layout images. It the layer is not selectable, objects on the layer can't be selected.
To the right of the sample box are the layer name and purpose names.
When the layer is not visible, the sample box is not drawn, and the green ``v'' indicator becomes a red ``nv''. Layers with the Invisible technology file keyword will by default be invisible. If the layer is not selectable, the layer name / purpose name area is shown with a dark background, and the green ``s'' indicator becomes a red ``ns''. Layers with the NoSelect technology file keyword will by default be non-selectable.
Visibility can be toggled by clicking on the v/nv indicator with button 1, or by clicking in the sample box area with button 2, or by clicking anywhere in the entry with button 1 and the Shift key held.
In releases earlier than 4.1.6, a layer visibility change would not automatically redraw the screen in physical mode. This is ancient behavior intended to accommodate slow screen redraws. When several layer visibility changes are to be made, one can make the changes and then force a screen redraw. This seems to be unnecessary on newer computers, which render very quickly, so the updating is now automatic. There is a variable, NoPhysRedraw, that if set will revert to the original behavior of no automatic redraw in physical mode, if the user prefers this.
Pressing Shift along with clicking button 2 in the sample box area will suppress redraw if the variable is not set. If the variable is set, then the Shift-click will redraw tha main window and all similar sub-windows after the operation. The drawing window that has the keyboard focus can be redrawn by pressing Ctrl-r. The rdraw button to the left of the coordinate readout will redraw the main window and all similar sub-windows.
In electrical mode, the SCED layer, which is the electrical mode active wiring layer, is always visible. Instead, of toggling visibility of this layer, the button presses will toggle between solid and empty fill.
Selectability can be toggled by clicking on the s/ns indicator with button 1, or by clicking in the layer name/purpose name area with button 2, or by clicking anywhere on the entry with button 1 and the Ctrl key held.
One can also toggle the visibility and selectability states of all layers except for the current layer. At the bottom of the layer table, there are two gray areas labeled ``vis'' and ``sel''.
Clicking the ``vis'' area with button 1 or button 2 will switch all layers except for the current layer to invisible, and back. The comment above regarding window redraw in physical mode applies here as well. If Shift is held while clicking, the current redrawing behavior is reversed. When switching back to ``all layers visible'', layers with the Invisible keyword applied in the technology file will remain invisible.
Similarly, clicking the ``sel'' area will switch all layers except for the current layer to non-selectable and back. When switching back to ``all layers selectable'', layers with the NoSelect keyword applied in the technology file will remain non-selectable.
Button 3 enables layer blinking, if neither of Shift or Ctrl is pressed. Pressing and holding button 3 over a layer entry in the layer table will cause that layer to blink periodically in the drawing windows, while button 3 remains pressed. Layers that happen to have the same color as the selected blinking layer will also blink, since the operation is sensitive only to the layer color.
In combination with Shift and Ctrl, clicking with button 3 on a layer entry provides a shortcut:
The current layer is shown with a blue highlighting box. Clicking on a layer entry with button 1 will make it the current layer. The current layer is used when creating objects in the layout.
One can also search for a layer to set as the current layer by name. Just above the layer table is a text entry area, with a button containing a blue triangle icon to the left. The name of the current layer is displayed in this area. This can be used to find layers by name. One can enter the first few characters of a layer name into the text area, then press the button to the left. The button icon will change to two triangles, and the layer table will scroll to the first matching layer found (if any), as the current layer. Clicking the button a second and subsequent time will scroll to the next and later matches. Though the text in the entry area will take on the selected layer name, the search string is retained internally as long as the two-triangle icon is displayed on the button. This will revert to the single triangle after a few seconds if not clicked. When using the layer:purpose form, both the layer and purpose strings are handled independently, and both can contain just the first few characters of the actual layer and purpose names.
The current layer can also be set with the setcl button in the top button menu. If one presses this button, then clicks on an object in a drawing window (the object must be contained in the current cell), the current layer will be changed to the object's layer. All of the rules for selections apply when interpreting which object will specify the layer, and in particular the object must be selectable.
The ltvis button in the top button menu will toggle the visibility of the layer table. The layer table takes a lot of screen area, and often it is not needed. The layer palette can be used instead to provide access to a few chosen layers.