Apple LaserWriter Pro 630 Envelope Feeder Specifications download pdf (Page 90)

CHAPTER 4

TrueType Fonts

78 Downloading TrueType Fonts to Disk

procedure with respect to setcharwidth, setcachedevice, and so on. This behavior

has existed in all PostScript font formats, but it has only been documented as part of

Level 2. This behavior is part of Type 42 BuildChar.

Class B Devices 4

Class B devices provide the primary motivation and design center for the TrueType font

format in its current conﬁguration. The small low-level patches are downloaded to

Class B devices to assist the TrueType code in its operation and to provide the necessary

hooks into the PostScript code. The deﬁnitions provided here are downloaded in the

userdict at the beginning of every job.

As stated earlier, TrueType code is downloaded on demand. If the eexec and cexec

operators are provided, their implementation must be compatible with Adobe

PostScript, or TrueType will not print on that implementation. Depending on the level

of compatibility, a PostScript error may be raised, or the printer may crash.

Since the content of the font on a Class A device may differ from that on a Class B

or Class C device, executing a PostScript forall operation within the context of a

TrueType font dictionary produces different results on different machines. This should

not be of signiﬁcant concern, since the main contents and required deﬁnitions are

the same.

Class C Devices 4

One crucial assumption made by the TrueType code is that all Class C devices support

the Adobe Type 1 font format. TrueType cannot be printed on a PostScript-compatible

printer that cannot interpret the Type 1 font format. An alternative solution (not

documented in this note) would allow TrueType characters to be printed on any

PostScript-compatible device by downloading a Type 3 (user-deﬁned) font with a

BuildChar procedure. This would convert TrueType data into cubic Bezier

curves

to be ﬁlled by PostScript. This is not an efﬁcient solution. With Adobe Systems,

Incorporated making the Type 1 font format public, more PostScript-compatible printers

will support the Type 1 format and therefore print TrueType.

Downloading TrueType Fonts to Disk 4

TrueType fonts may be downloaded to printers equipped with hard disk drives that

store fonts. The entire font may be stored and used just like any other PostScript font, or,

depending on the intelligence of the font-downloading utility, the font can be stripped of

unnecessary items that will not be used on a particular class of printer. To facilitate the

A Bezier curve is a freehand curve, named after the mathematician who first described it. It is similar to a

hand-drawn curve, and you may use it when you need a continuous curve. A filled curve is one in which the

enclosed area of the curve is shaded.

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Apple LaserWriter Pro 630 Envelope Feeder Specifications Page 90