The otag file contains a tag list that describes the typeface. All of these tags are defined in <diskfont/diskfonttag.h> as either level 1, level 2, or level 3 outline tags. Level 1 tags are required to be present in an otag file. Level 2 and 3 tags are optional. See the include file for more information on the tag levels. The first tag of the otag file is always OT_FileIdent. Its value is the size of the otag file. This tag is here to verify the validity of the otag file. If the first tag is not OT_FileIdent, or the OT_FileIdent tag value is not the size of the otag file, the otag file is invalid, so don't attempt to use it. If the file is valid, copy the entire file into a buffer. The tags from the otag file have a special OT_Indirect bit. If this bit is set, the tag's value is an indirect reference to data defined elsewhere in the otag file. The tag's value is the offset to the data (in bytes) from the beginning of the otag file. For example, the otag file fonts:CGTimes.otag that is on the 2.04 Release disks contains the tag OT_Family (0x80009003), which has its OT_Indirect bit set. The value of the OT_Family tag is 195, meaning that the data for it--the NULL terminated string ``CG Times''--is located 195 bytes into the otag file. Of course, if an application read the file fonts:CGTimes.otag into a memory buffer, the ``CG Times'' string would be 195 bytes from the beginning of the buffer. The OT_Family tag must point to the absolute address of its data, so when an application loads an otag file into memory, it has to resolve the indirection of the OT_Indirect tags in memory. The application can do this by adding the buffer address to each OT_Indirect tag value.
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