version

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

    is positive.

 5: Changed definition of De in draw.ps so savematrix is loaded with the CTM
    whenever De is executed. Original implementation didn't work with forms.ps
    because the CTM is changed with each page image. (4/29/89)

 6: Flush stdout when postio is invoked with the -t option - just convenient
    not necessary. (4/30/89)

 7: Included a man page for the picture inclusion macros - file man/mpictures.5.
    (5/6/89)

 8: Added BoundingBox code to dpost - still needs to go in other translators.
    Most of the work is done in common/bbox.c. (5/7/89)

 9: Fiddled with the bracket building stuff in dpost.ps so things finally look
    decent. Was particularly bad on the typesetter.

10: dpost now generates a PageBoundingBox comment and ps_include.c accepts
    the comment. Added -B option to enable/disable the BoundingBox calculations.
    -Bon to enable and -Boff to disable. On by default now, but that may change.
    Add similar code to the rest of the translators (6/20/89).

11: Fixed ps_include.c so it properly handles %%BeginGlobal and %%EndGlobal.
    Added braces and compare page.start to page.end instead of 0.

12: Added xymove(hpos, vpos) for \X'PS ...' request - near the end of devcntrl().
    Must output position info for following PostScript.

13: Added a call to endtext() immediately before the oput() call for \N'...'
    requests. Without it spacing often messed up with -e2 but not -e0.

------------------------
Version 3.1	11/15/88
------------------------

 1: postio can run as one or two processes (-R option) and can establish an
    interactive connection with a postscript printer (-i option). Parsing of
    status reports has been improved. The status query mechanism can be disabled
    using the -q option. An exit status of 1 implies a system error (eg. can't
    open the line) while 2 usually means there was an error in the PostScript
    file. By default postio runs as a single process. The -B, -R, and -q options
    can be used to speed things up some. A version of the program (previously
    supplied in postio.tmp) that can help if you seem to be having flow control
    problems can be obtained using the -S option. It's not generally recommended
    and should only be used as a last resort!

 2: Several widthshow encoding schemes have been added to dpost and can reduce
    print time by 20% or more. The method used to encode lines of text can be
    changed on the command line using the -e option. Level 0 produces output
    essentially identical to previous versions of dpost. The default can be
    changed by modifying the definition of ENCODING in ./Makefile. At present
    only level 0 is thoroughly tested, although level 2 (ie. -e2) may be the
    default and is undoubtedly worth a try.

 3: dpost now supports color selection and reverse video. Access in troff is via
    the stand-alone macro package ./macros/color. Examples are,

	.so /usr/lib/macros/color
	.CL red "this prints in red"
	.CL "white on black" "and this prints white text on a black background"

    The postscript procedures that handle color and reverse video can be found
    in ./postscript/color.ps. Additional colors can be added to the colordict
    dictionary defined in ./postscript/color.ps.

 4: The dpost drawing routines have been improved and have been moved from the
    prologue (ie. ./postscript/dpost.ps) to ./postscript/draw.ps. That file is
    only included if needed. Drawing routines now support the ability to group
    a series of drawing commands together as a single path. May be useful for
    future versions of pic that wish to fill regions with colors or gray levels.
    Access is via the new "x X BeginPath" and "x X DrawPath" device control
    commands. In addition there's some complicated PostScript code in file
    ./postscript/baseline.ps, that can be used to set text along an arbitrary
    curve. It's terribly confusing and I doubt anyone will have the patience to
    bother to figure it out.

 5: A simple picture packing troff preprocessor (picpack) has been included and
    the code needed to recover pictures and text has been added to dpost. The
    program is designed to supplement to the original picture inclusion mechanism,
    and should ONLY be used when absolutely necessary. Using dpost to pull picture
    files into a document is strongly recommended and will always be the more
    efficient and portable approach. picpack simply provides a way to combine
    pictures and text in a single file before dpost is executed. It may help in
    a distributed printing environment where the user runs everything through
    troff while a spooling daemon (eg. lp) handles the postprocessing. There
    are serious disadvantages to this approach, with perhaps the most important
    being that troff output files (when picpack is used) will likely result in
    files that can no longer be reliably passed through other important post-
    processors like proof.

 6: Code to handle host resident PostScript fonts in dpost has been tested and
    finally works. The -H option points dpost to a host resident font directory,
    which by default is NULL. Host resident font files stored in that directory
    must be assigned a name that corresponds to the one or two character troff
    font name. Width tables must also be built (see buildtables/README), the new
    binary font files must be installed in /usr/lib/font/devpost, and a mapping
    definition from troff's name to the PostScript font name must be added to
    ./postscript/dpost.ps.

 7: The default pattern length in postdmd has been reduced to from 10 to 6 bytes.
    Printers with fast processors (eg. PS-810s) often benefit from a further
    reduction, while optimal performance on slower printers (eg PS-800s) may
    require larger pattern sizes. The pattern length can be set using the -b
    option. Increasing the pattern size usually increases the size of the output
    file.

 8: Line drawing in posttek and postbgi includes code that automatically ties
    lines to device space coordinates when you select a non-zero width. Helps
    eliminate the variation in line thickness that many observed. The default
    line width in posttek and postbgi is still 0 (which gets 1 pixel). If you
    want a different default change the definition of variable linewidth in files
    ./postscript/posttek.ps and ./postscript/postbgi.ps.

 9: Defocused lines in posttek have been fixed.

10: postbgi now supports color and can be used to translate most PRISM (color
    BGI) jobs. Special device specific tuning needed for many PRISM jobs can be
    enabled by using the -P"/prism true" option. Missing pieces (eg. subroutines)
    needed for translating PRISM jobs, have also been implemented.

11: postreverse can reverse the pages in documents that conform to Adobe's 1.0
    or 2.0 file structuring conventions, and it works with all the translators in
    this package. The new version is backwards compatible, but files produced by
    the new translators should not be passed through old versions of postreverse.
    The likely result will be no output at all. If you choose to do a partial
    installation put the new postreverse up first!

12: All translators attempt to conform to Adobe's Version 2.0 file structuring
    conventions. dpost output falls short, but only in the interest of efficiency.
    Passing dpost output through postreverse (perhaps with the -r option) produces
    a minimally conforming PostScript file.

13: All the translators now support three options that pass arbitrary PostScript
    through to the output file. The -P and -C options add a string and the
    contents of a file respectively immediately after the prologue. It's assumed
    whatever is added is legitimate PostScript - there is no checking. In each
    case the added PostScript code becomes part of the job's global environment.

    The -R option can be used to request special action (eg. manualfeed) on a
    global or page basis.  The argument should be "request", "request:page", or
    "request:page:file". If page is given as 0 or omitted the request applies
    globally. If file is omitted the lookup is in /usr/lib/postscript/ps.requests.
    The collection of recognized requests can be modified or extended by changing
    /usr/lib/postscript/ps.requests.

14: PostScript code (from Johnathan Shopiro) that produces bolder versions of the
    Courier fonts has been included in file postscript/fatcourier.ps. The file
    can  be added to individual prologue files (eg. dpost.ps) or pulled in as
    needed using the -C option.

15: postmd is a new program that can be used to display a large matrix as a gray
    scale image. May help if you're looking for patterns in a large matrix. A very
    optimistic estimate suggests you can display up to a 600x600 matrix (with five
    different shades of gray) on 300dpi printer using 8.5x11 inch paper.

16: What's available in buildtables has been cleaned up and works well with the
    new version of postio. It can be used to have PostScript printers build troff
    width tables for both printer and host resident fonts.

17: The PostScript bind operator has been applied to all procedures that are
    expected to be executed more than once. Redefined save and restore procedures
    are no longer needed and saverestore.ps is not included in this package.

18: The bizarre PostScript code used to get to the upper left corner of a page
    in old versions of dpost.ps and postprint.ps has been replaced by something
    that's at least slightly more comprehensible. All prologues have also been
    changed so picture inclusion (eg. including a pic picture that's been run
    through troff and dpost) should work better than previous versions. Still
    missing (from most translators) is the %%BoundingBox comment and even when
    it's put out (by postdmd) only the dimensions are correct - sorry!

19: The careless mistake in the DKHOST section of postio that some noticed belongs
    to me (not Allan Buckwalter) and has now been fixed.

20: By default all prologues still use the current clipping path to determine page
    dimensions, but that behavior can be disabled by setting boolean useclippath
    (in each prologue) to false. In that case the page dimensions will be taken
    from array pagebbox, which by default is initialized to 8x11 inch paper. The
    -P options (in each translator) can change useclippth and pagebbox.

21: New in the misc directory is sample lp support from Maryann Csaszar and a
    simple program that converts host resident font files obtained from a Macintosh
    to a format that works on Unix.