Technote 1146

LaserWriter 8 and Fonts

CONTENTS

LaserWriter 8 Spooling and Fonts

Character Encodings

Font Keys

Font Downloading

Classic TrueType Support

OFA Font Support

Double-Byte Font Support

Font-Related Queries

Font Preferences Bits

Downloadables

LaserWriter 8 Spooling and Fonts

Character Encodings

Note 1:
On most PostScript printers, the Symbol font contains a description of the Macintosh Apple character
() decimal 240 in the Macintosh character set). However, printers from vendors other than Apple typically do not include this character in the encoding vector for the Symbol font, making the character inaccessible when printing without reencoding. LaserWriter 8 explicitly reencodes the Symbol font to include the Apple character, ensuring that it will print correctly even on non-Apple printers.

Note:
PostScript printers with a PostScript language level of 1 or 2 do not include the Euro glyph in the Symbol font. In order to print the Euro glyph on these printers, LaserWriter 8 downloads a Type 1 Euro glyph and maps it into the printer's Symbol font. The Roman fonts shipping with Mac OS 8.5 have the Euro glyph included.

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Font Keys

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Font Downloading

0. A PostScript outline font stored as a Type 1 'sfnt'
   
1. A PostScript outline font file in Adobe Type 1 or Type 3 format
   
2. An outline font in classic Apple TrueType format
   
3. A font with an 'sfnt' resource in a format recognized by OFA (Mac OS 8.5 and later only). See note below.
   
4. A QuickDraw bitmap font that can be converted to Adobe Type 3
   

Note:
Prior to Mac OS 8.5, all fonts with 'sfnt' resources were either classic Apple TrueType fonts or Type 1 'sfnt' fonts. Mac OS 8.5 introduces Open Font Architecture (OFA) scalers and the ability to have additional 'sfnt' types besides classic Apple TrueType fonts and Type 1 'sfnt' fonts. (Prior to Mac OS 8.5, OFA was only available when QuickDraw GX was installed.) When this document refers to OFA-only fonts, it refers specifically to 'sfnt' fonts which are neither classic TrueType fonts or Type 1 'sfnt' fonts. See the section OFA Font Support for how OFA-only fonts are handled in Mac OS 8.5.

For fonts that are not already available on the target output device, LaserWriter 8 attempts to download a suitable version from the host Macintosh as part of the PostScript output stream. It first determines if the font is a Type 1 'sfnt' font. A Type 1 'sfnt' font has 'typ1' for the version of the 'sfnt' data. If the font is a Type 1 'sfnt' font, then the Type 1 data from the 'sfnt' is emitted into the PostScript output stream.

If the font is not a Type 1 'sfnt' font, the driver next looks for a file on disk containing a PostScript version of the font. The name of the file containing the font is constructed from its PostScript name, along with any style attributes applied to it, using the standard “5–3–3” rule described below:

1. Obtain the base font name from the style mapping table of the 'FOND' resource. Truncate this name to the first five characters (ignoring the leading four characters, "ITC-", if present). For example the base PostScript base font name "Palatino" becomes "Palat" while the base name "ITC-Palatino" also becomes "Palat".

2. Truncate each suffix to three characters needed to satisfy a QuickDraw style as specified by the style mapping table. For example the suffix "Bold" becomes "Bol" and "Light" becomes "Lig". Each triple is appended to the truncated base name.

Full example:

"Helvetica-Heavy-Italic-Condensed" becomes the file name "HelveHeaItaCon".

The driver searches for the font file in the following locations, in the order listed:
1. In the System's Font Folder
2. In the System's Extensions folder on the startup volume
3. In the System folder

If the PostScript font file is not available on disk and the font is a classic TrueType version, it is handled as described in the Classic TrueType Support section. If the font is not a classic TrueType font but is instead an OFA-only font, the driver uses OFA to download the font. The section OFA Font Support below describes the details.

If the font is none of the above types, the driver uses the QuickDraw bitmap (screen) version. Using the bitmap font, the driver constructs a PostScript Type 3 font using the PostScript imagemask operator to draw the characters from the font's bitmap data.

Saving to Disk

When saving to a disk file rather than printing to a printer, LaserWriter 8 never includes bitmap versions of PostScript fonts, regardless of the "Font inclusion" setting in the Save dialog. Instead, it simply includes an Adobe Document Structuring Conventions (DSC) %%IncludeFont comment indicating that the PostScript font is needed. By contrast, pure Macintosh bitmap fonts—those whose font description ('FOND') resource does not identify a PostScript equivalent—are always included when saving a PostScript file to disk. Such fonts are not bracketed with the DSC comments %%BeginFont and %%EndFont, however, since, for purposes of document management, the driver does not treat them as PostScript fonts.

Substitute Fonts
If the user has checked the "substitute Fonts" option in the PostScript Options panel of the Page Setup dialog, the driver replaces all occurrences of the standard Macintosh screen fonts Geneva, New York, and Monaco with the PostScript equivalents Helvetica, Times, and Courier, respectively. The substitution occurs even if TrueType outline fonts are available for Geneva, New York, and Monaco. Text sizes in the document are appropriately scaled to compensate for size differences between the corresponding families of screen and printer fonts: for instance, each size of Times is scaled by a factor of 1.087 to approximate the corresponding size of New York. Unlike the LaserWriter 7 driver, LaserWriter 8 does not suppress font substitution if the client program has enabled QuickDraw's fractional character widths.

Standard Font Downloading
When background printing, the driver knows the entire document's font needs prior to its generation of PostScript output. Ordinarily, when background printing, all of a document's downloaded fonts are transmitted just once at the beginning of the document, as part of the job setup section preceding the first page. LaserWriter 8, when printing directly to a printer, but not to a print queue server or to disk, can delay the downloading of a given font to just before the start of the page with that font's first occurrence. Fonts are downloaded once for each document, and are downloaded so that they remain in PostScript VM for the duration of the document.

When foreground printing, fonts are downloaded as they are encountered within a document. Each font is downloaded outside of the PostScript page level save, and therefore remains in the printer's VM for the duration of the job.

Unlimited Downloadable Fonts
The "Unlimited Downloadable Fonts" option in the PostScript Options panel of the Page Setup dialog modifies the behavior described above for foreground and background printing so that instead each downloadable font is sent each time it is switched to within the document. This minimizes the demands on printer memory by, in effect, keeping only one downloaded font resident at a time, but it can significantly affect the time needed to print the document.

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Classic TrueType Support

If no PostScript version of a required font is available, either on the target output device or on the host Macintosh, LaserWriter 8 looks for a classic TrueType font to download from the host machine. LaserWriter 8 classifies a font as a classic TrueType font if it contains a resource of type 'sfnt' with a version of either 0x00010000 or 'true', and also contains a 'glyf' table in the 'sfnt'. If the font is an 'sfnt' font but is not a classic TrueType font (or Type 1 'sfnt'), then the font is considered to be an OFA-only font and is handled as described below in the section OFA Font Support.

Note:
With LaserWriter 8.6, if both PostScript and TrueType versions of a font are available, the driver always gives preference to the PostScript version. In LaserWriter 8.6.5, the user can modify this behavior by choosing "TrueType" as the Preferred Format in the "Font Settings" panel. In that case, the driver does not look for the PostScript version of the font on the host if the TrueType version exists.

In order to use TrueType fonts directly for drawing text, the PostScript interpreter on the output device needs a copy of Apple's TrueType rasterizing code, known as the TrueType scaler. The device may have its own resident copy of the scaler, or, for some printers, it may be included in the PostScript output stream as one of LaserWriter 8's downloadable procedure sets. The downloadable rasterizer only works on some level 1 PostScript interpreters.

• Properly working versions of the PostScript cexec and eexec operators are defined in the device's systemdict dictionary.
• The device has enough virtual memory (at least 120K) available to run the scaler.
• The device is not an older-model (original) LaserWriter or LaserWriter Plus.

The response LaserWriter 8 receives to its print-time *TTRasterizer feature query tells whether the device has its own copy of the scaler or, if not, whether it can accept a copy in downloaded form. LaserWriter 8 uses this information to determine how to handle TrueType fonts:

1. If the scaler is built into the output device, LaserWriter 8 simply transmits each font in Type 42 format.
2. If the scaler is not built in, but can be downloaded, LaserWriter 8 includes the TrueType scaler in its print job and then transmits each font in a Type 42 format.
3. If the scaler is not built in and cannot be downloaded, LaserWriter 8 converts each TrueType font to an unhinted Adobe Type 1 font, and transmits it in that form.

If the status of the scaler on the output device is unknown (for example, if the PostScript output is being saved to a disk file or sent to a spooler that does not understand the *TTRasterizer feature query), LaserWriter 8 includes the scaler in the PostScript output stream and transmits each TrueType font in both a Type 42 and an unhinted Type 1 version. In this case, the driver also emits conditional PostScript code to test the availability of the scaler at print time and load it into the device's memory only if the device can accept it and doesn"t already have a built-in copy. If the scaler is available at print time (whether built-in or downloaded from the PostScript output), the conditional code uses the Type 42 version of each font and discards the Type 1 version; if not, it uses the Type 1 version and skips the Type 42 version.

LaserWriter 8.6.5 introduces special handling of protected fonts. Some TrueType fonts contain a special 'OS/2' table indicating that they are to be specially protected. Such fonts are to be specially marked so that post-processing software can protect the font in an appropriate fashion. To properly support a font containing an 'OS/2' table, LaserWriter 8.6.5 now emits special data into a Type 42 format PostScript font generated from such a host font. It does this by using the value of the fsType field of the 'OS/2' table to insert a /FSType key into the FontInfo dictionary of the generated Type 42 font. Note that the integer value stored in the /FSType key is the fsType value from the 'OS/2' table with its zero bit masked off. Adobe Acrobat Distiller 4.0 uses this /FSType key as an indicator as to whether or not such a font can be embedded in a PDF document that Distiller generates from a PostScript file.

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OFA Font Support

Fonts which are considered to be "OFA-only fonts" are only available and supported on Mac OS 8.5 and later. For these fonts, the driver itself does not know how to generate the PostScript version of the font; it asks OFA to do so. In this case, the driver tells OFA what font it requires and what type of output the PostScript interpreter can handle; OFA is then responsible for streaming the PostScript version of the font into the output data stream.

When the driver requests a font from OFA, it indicates what the supported output types are, and OFA is then responsible for generating one of the types that can be supported. When printing to a PostScript device where it knows that Type 42 data can be directly supported, the driver indicates that Type 42, Type 1, and Type 3 output are supported. If the driver knows that the device cannot support Type 42 data, then the driver indicates that Type 1 and Type 3 output are supported. If the driver does not know whether Type 42 can be supported, it requests a portable format. When using OFA, the LaserWriter 8.6 driver never requests the downloadable TrueType scaler format described above.

As of Mac OS 8.5, OFA generates Type 1 (or perhaps Type 3) output for the portable format requested by the driver. OFA does not generate the wrapper containing both Type 42 and Type 1 fonts described above for classic TrueType font support. This means, for example, that when saving to disk, an OFA-only font is never inserted into the stream as a Type 42 font, only as Type 1 font data.

LaserWriter 8.6.5 adds support for OFA fonts that are so-called data fork fonts. These fonts do not have the traditional 'sfnt' resource, but instead contain the 'sfnt' data in the font data fork. LaserWriter 8.6.5 supports printing and downloading these fonts when they are used with by applications drawing with QuickDraw.

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Double-Byte Font Support

The character sets for Chinese, Japanese, and Korean fonts are typically thousands of characters and require 2 bytes of data to specify a given glyph. Such fonts are frequently called "CJK fonts" and support for such fonts is called "CJK support." Because these fonts are very large (megabytes in size), it is impractical to download these fonts to PostScript printers as part of a print job. For this reason, LaserWriter 8's support for CJK fonts in the Macintosh OS is handled differently than that for traditional 1 byte fonts. This support is done by working with WorldScript II.

On the Macintosh, text drawing is done through the textProc QuickDraw bottleneck. As with all bottlenecks, LaserWriter 8 installs its own textProc bottleneck in the port so that all text imaging is done via calls to its text bottleneck. This bottleneck is responsible for turning text drawing into PostScript code to select the appropriate font and draw the requested text in that font.

In some cases, the text coming to the driver's text bottleneck needs to be intercepted and handled specially by system software. This is made possible by the driver's use of the print action routine. Immediately after LaserWriter 8 inserts its bottlenecks into the printing port, it calls the Script Manager's print action routine. When it calls the print action routine, it passes in the printing port and a verb indicating the action it will take with that port. The action verbs consist of kLWSpoolAction (during spooling when two-pass printing), kLW2PassPlaybackAction (during playback when two-pass printing), and kLW1PassPlaybackAction (during one-pass printing).

The driver's call to the print action routine allows the Script Manager to replace the driver's textProc bottleneck with its own textProc bottleneck in the printing grafPort. This allows the Script Manager to first process text drawing calls before the driver's text drawing processes them. In the case of double-byte fonts, the Script Manager, together with WorldScript II, can either pass the text through to the driver's text bottleneck or, when appropriate, rasterize the text drawing on the host and call CopyBits on the rendered bitmaps. This results in calls to the driver's bitsProc bottleneck to send the rendered bitmaps in the printer.

In principle, all drawing of 2-byte text could be drawn on the host as bitmaps, but this would result in slow performance and would not utilize any 2-byte fonts that were actually available in the printer. Instead, if the current font used for drawing is a 2-byte font, WorldScript II's text bottleneck routine calls the LaserWriter 8 driver to determine whether the font used for this call to the text bottleneck is available in the printer. If driver reports that the font is available in the printer, WorldScript II's text bottleneck calls through to the driver's text bottleneck and the driver's bottleneck generates the PostScript code necessary to draw the text in the printer. If the LaserWriter 8 driver reports that the font is not available in the printer, WorldScript II images the text on the host and calls CopyBits to image the rendered text into the printing port.

Note:
This discussion applies to all versions of LaserWriter 8, up to and including LaserWriter 8.6.5.

During background printing, the driver first spools all drawing to disk. The print action verb kLWSpoolAction is used when calling the Script Manager's print action routine. If WorldScript II's text bottleneck determines that a two-byte font is used, it calls the driver to determine if that double-byte font is available in the printer. During the spooling pass, the driver always reports that all fonts are available in the printer. This ensures that there is never any conversion of text into bitmaps during the spooling pass.

On the second pass of background printing, the driver uses the print action verb kLW2PassPlaybackAction. As described above in the section LaserWriter 8 Spooling and Fonts, during the second pass prior to playing back the spooled application drawing, LaserWriter 8 first queries the printer to determine the availability of the fonts that were used in the drawing. Thus, during the second pass, when WorldScript II's text bottleneck routine calls the driver to determine whether a given font is available in the printer, the driver can correctly answer based on its knowledge of the document fonts in the printer.

During foreground printing, the driver calls the print action routine with the verb kLW1PassPlaybackAction. As described above in the section LaserWriter 8 Spooling and Fonts, during one-pass printing, prior to any application drawing, LaserWriter 8 first queries the printer to request the list of all fonts that are available. Thus, when WorldScript II's text bottleneck routine calls the driver to determine whether a given font is available in the printer, the driver can correctly answer based on its knowledge of fonts in the printer.

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Font-Related Queries

The LaserWriter 8 driver uses two different font queries; one is for the availability of a specific set of fonts, while the other is for a full list of fonts available in the printer. The query used depends upon whether the driver is printing in foreground or background mode.

When background printing, the LaserWriter 8 driver gathers the list of PostScript fonts used in the document during the spool pass, and queries the printer about the availability of each font. The font query takes the following form:

%%?BeginFontQuery: <list of font names>. . .  % PostScript code to find font availability
%%?EndFontQuery: Unknown

The %%?BeginFontQuery comment contains a list of all fonts required by the document. Fonts are listed without the slash character (/) that typically precedes a PostScript font invocation: for example,

%%?BeginFontQuery: Times-Roman Times-Bold Minion Helvetica

For each required font, the driver uses the QuickDraw name recorded in the spool file to access the font description resource, which contains a style mapping table giving the corresponding PostScript font name, which is dependent on the QuickDraw style attributes taken from the spool file. The driver then uses this PostScript name in its print-time font query. PostScript Level 1 output devices respond to the query by reporting a font available if it is permanently resident in the device's ROM, or if it is currently present in RAM or on a disk connected to the device. On Level 2 devices, the query code determines the font's availability via the PostScript resourcestatus operator: the font may potentially reside in memory, on a disk, in a cartridge, on a remote server accessible over the network, or on any other type of device known to the resourcestatus operator. See the PostScript Language Reference Manual for more information on the resourcestatus operator.

The response to the query indicates which of the specified fonts are already available on the target device; the driver then downloads the remaining fonts as part of the ensuing print job. See below for further specifics on this query.

%%?BeginFontQuery: font1 font2 ... fontn

Requests information about the availability of PostScript fonts on the target output device. LaserWriter 8 uses this information to decide which fonts to include as part of the ensuing print job. If the PostScript output is being saved to a disk file rather than sent directly to a printer, the equivalent information is provided by the user in the "Font inclusion" item of the Print dialog's Save panel.

Under version 3.0 of the Document Structuring Conventions, the correct response to this query is of the form:

/fontn:Yes
. . .
/font2:No
/font1:Yes
*

where each font name is followed by a colon and the word "Yes" if the given font is available on the target device, "No" if it is not.

Notice that each font name is preceded by a slash character (/) in the response to the query, but not in the query itself. Notice also that the fonts appear in the response in reverse order from the way they are listed in the original query, and that the entire response is terminated with an asterisk (*). For example, the response to the query:

%%?BeginFontQuery: Times-Roman Times-Bold
%%+ Minion Helvetica
might be
/Helvetica:Yes
/Minion:No
/Times-Bold:Yes
/Times-Roman:Yes
*

Note:
In describing the response to this query, some printings of the PostScript Language Reference Manual (Second Edition, section G.8) erroneously show a space between the colon and the word "Yes" or "No". LaserWriter 8 compensates for this error by accepting responses with or without a space following the colon.

Some print queue servers (notably the AppleShare print server prior to version 5.0) use an older form of response to the font query, as defined by version 2.0 (rather than 3.0) of the Document Structuring Conventions. For compatibility, LaserWriter 8 also accepts responses of this form. Such responses simply use the integers "1" and "0" instead of "Yes" and "No" to indicate font availability, and do not include the font names themselves or the terminating asterisk: for example,

As in the first form, the order of the fonts is reversed from the original query (Minion, Times-Bold, Times-Roman, and Helvetica in the example).

Note:
The AppleShare print server prior to version 5.0 imposes a further restriction on the length of a single font query: the number of characters in the list of font names in the %%?BeginFontQuery comment must not exceed 128. To accommodate this restriction, LaserWriter 8 breaks any font query that exceeds this limit into two or more separate queries.

%%?BeginFontListQuery
. . .  % PostScript code to return font list
%%?EndFontListQuery: Unknown

/Helvetica-Bold
/Palatino-Roman
/ZapfDingbats
/Times-Roman
/Times-Italic
/Palatino-Italic
/Times-Bold
/Palatino-Bold
/Helvetica
/Courier
/Helvetica-Oblique
/Courier-Oblique
/Symbol
*

See Adobe Technical Note #5001, PostScript Language Document Structuring Conventions Specification for more information on the font queries.

%%?BeginFeatureQuery: *TTRasterizer
// PostScript code to look for the rasterizer.
%%?EndFeatureQuery: Unknown
The further specifics of this query are:
%%?BeginFeatureQuery: *TTRasterizer

As described earlier, LaserWriter 8.6.5 allows the user to choose the "Never generate Type 42 format" setting, which causes the driver to always treat the results of the *TTRasterizer query as 'None', regardless of the results of any query. This setting also applies to save to file print jobs.

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Font Preferences Bits

Note:
The information about the 'PRFS' and 'PRF2' resources in LaserWriter 8 and PrintingLib versions 8.6 and 8.6.5 is for informational purposes only. The existence of these resources and bits control special behaviors that are subject to change with further releases of the LaserWriter 8 driver.

Summary

Further References

• Adobe's PostScript Language Reference Manual
  
• Inside Macintosh: Text
  
• Technote 1140: The Euro Currency Symbol
  
• Technote 1169: The Download Manager
  
• Adobe Technical Note #5001, PostScript Language Document Structuring Conventions Specification
  

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Downloadables

Acrobat version of this Note (51K).

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Change History

• Originally written in November 1998, as Technote 1146, "LaserWriter 8.6 and Fonts" by David Gelphman and Ingrid Kelly.
  
  
• In May 1999, this Technote was updated to reflect changes made for LaserWriter 8.6.5.
  
  

Acknowledgments

Thanks to John Blanchard, Rich Blanchard, and Paul Danbold.