CIF Settings

Extension Flags
This drop-down menu provides access to a number of checkable buttons which correspond to flags which enable various CIF format extensions. There are two banks of flags, the bank displayed is initially determined by the state of the Strip For Export button in the Export Control panel, or equivalently the state of the StripForExport variable. The top entry of the menu indicates this state. Clicking this entry will switch the menu to display and control the other bank of flags. The default values for the flags in the Strip For Export inactive case are all set, so all extensions are turned on. The other bank has all flags unset, so by default no extensions will be used when Strip For Export is set. However, the status of any of the flags can be toggled with this menu.

The flag states track the value of the CifOutExtensions variable.

The format extensions enabled by these flags are described in B.3, CIF Format Extensions.

The lower section of the CIF page contains three option menus which control aspects of the syntax used when writing CIF files. The three selectable variations are the syntax used for the cell name extension, the interpretation of the ``L layer;'' syntax element, and the syntax used for the label extension. Xic can handle almost transparently any of these syntax variations, however third-party applications may require a specific variation.

The selections shown in the menus tracks the value encoded in the CifOutStyle variable. When this variable is unset, the defaults (the first choice in each menu) are used.

Last Seen
When a CIF file is read into memory, the style of the CIF file is saved internally. Pressing the Last Seen button will update the three style menus to these saved values, by setting or clearing the CifOutStyle variable.

CIF Cell Name Extensions
Cell names were not part of the original CIF syntax specification. Various extensions have been used to supply cell names in a CIF file. Each of these extensions consists of command following the ``DS ...;'' command, in the following forms:

cname_index	Historic Name	Format
0	IGS	9 cell_name;
1	Stanford/NCA	(cell_name);
2	Icarus	(9 cell_name);
3	Sif	(Name: cell_name);
4	none	no extension used

In Xic, any of the first four forms (indices 0-3) will be recognized equivalently when reading CIF input.

CIF Layer Specification
Layers are specified in CIF in a command with syntax

L token;

The the token can be interpreted in two ways; as the name of a layer, or as an index into a layer table. For the second interpretation, the token must of course be an integer.

layer_index	Historic Name	Format
0	none	L layer_name;
1	NCA	L layer_index;

Of these, the first entry is most common. Xic can handle both of these interpretations (see 14.9).

If the indexing is selected for layers, the index will be 1-based, and correspond to the layers, left to right, in the layer table, i.e., the leftmost (lowest) layer in the layer table is designated index 1.

CIF Label Extensions
Text labels were not part of the original CIF syntax specification, so that various extensions are used to pass label information.

label_index	Historic Name	Format
0	Xic	94 «label» x y orient_code width height;
1	KIC	94 label x y;
2	NCA	92 label x y layer_index;
3	Mextra	94 label x y layer_name;
4	none	no labels used

Unlike other extensions, the first extension listed above is unique to Xic. If other formats are used, label size and orientation information will be lost. When reading CIF input, any of these forms will be accepted.