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author | Norbert Preining <norbert@preining.info> | 2019-09-02 13:46:59 +0900 |
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committer | Norbert Preining <norbert@preining.info> | 2019-09-02 13:46:59 +0900 |
commit | e0c6872cf40896c7be36b11dcc744620f10adf1d (patch) | |
tree | 60335e10d2f4354b0674ec22d7b53f0f8abee672 /obsolete/systems/omega/README |
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diff --git a/obsolete/systems/omega/README b/obsolete/systems/omega/README new file mode 100644 index 0000000000..4793b07993 --- /dev/null +++ b/obsolete/systems/omega/README @@ -0,0 +1,134 @@ + +Dear Omegists, + +Multiple direction support is now included in Omega 1.10. +The release can be found at + +ftp://ftp.cse.unsw.edu.au/pub/users/plaice/Omega/web2c-7.3-omega-1.10.tar.gz + +Here is the README file. Real documentation will follow. + +Enjoy! + +John and Yannis +=========================================================================== + + +Release 1.10 includes substantially improved support for multidirectional +typesetting. It goes well beyond the support anticipated in the last +documentation. Here is some cursory documentation en attendant that the +real documentation is prepared with lots of examples. + + +1. The directions +----------------- + +It turns out that there are 32 (!) writing directions. They are +designated by three-letter codes. The three letters are always T, R, +B or L, and they mean, respectively, the Top, Right, Bottom or Left +sides of the page. + +The first letter (the primary direction), corresponds to the side of +the page where the first line is to be found. The second letter (the +secondary direction), corresponds to the side of the page where the +first character of a line is to be found. The third letter (the +tertiary direction), corresponds to the orientation of characters +within each line. + +Four directions seem to satisfy the needs of unilingual typesetting +for all of the modern scripts. + +TLT: Left-to-right writing. The most commonly used writing direction. +Scripts include LGC scripts, Indic scripts, South-East-Asian scripts, +various syllabaries. + +TRT: Right-to-left writing. Scripts include Hebrew, Arabic and Syriac. + +RTT: Vertical ideogram writing. Scripts include Chinese, Japanese +and Korean. + +LTL: Vertical cursive writing. Scripts include Mongolian. + +However, when we start to mix scripts of different directions, +a number of interesting combinations appear. The authors have +seen the following combinations: + +RTR: English within a Japanese text. + +RTL: Arabic within a Japanese text. + +RBR: Arabic within a Japanese text (starts at bottom of page). + +LTT: Chinese within a Mongolian text. + +RTL: Mongolian within a Chinese text. + +LTR: English or Russian within a Mongolian text. + + +2. The parameters +----------------- + +The following parameters are called direction parameters, and they +control the behavior of the Omega system. + +\pagedir The direction for pages (\shipout). +\bodydir The direction for vboxes, including the main body of text. +\pardir The direction for paragraphs. +\textdir The direction for text and hboxes. +\mathdir The direction for mathematics. + +Direction parameters act similarly to other parameters. For example +\bodydir RTT changes the direction of the main body of text to RTT. +Similarly, \the\mathdir gives the current direction for mathematics. +All these parameters respect groups. + + +3. Additional primitives +------------------------ + +\pageheight and \pagewidth are new dimensions. The default values +for these are for A4 pages. + +\hbox, \vbox and \vtop can all take a direction parameter. The syntax +is \hbox dir TRT ...{...}. The direction must be the first parameter +to the box. + + +4. How it works +--------------- + +Normally, the page and body directions would be set once --- at the +beginning --- in the document. Furthermore, in most situations they +would be the same. However, for vertical typesetting, it is common +for the headers and footers to be horizontal. In that case, the page +and body directions would be set to be orthogonal to each other, for +Japanese, say, \pagedir TRT\bodydir RTT. + +The paragraph and text directions would also normally be the same. +However, if there are scripts of different directions within the same +paragraph, then the text direction would vary. Since the parameter +definitions respect the groups, nesting of writing directions is +easily done. For example, an English insertion in a Hebrew document +would simply be {\textdir TLT\cmr10 An English insertion}. Note that +you can get interesting effects, since paragraphs are not group +delimiters. + +The math direction would normally be the same as the text direction. +However, real math only works properly for the left-to-right writing +directions (TLT, RTR, BRB, LBL). Fake math (used for typesetting +tabular in LaTeX) works properly. + +Note that when a box is begun, then the body, paragraph and text +directions all take the same direction as that box. This will be true +regardless of whether the direction of the box was given explicitly. + + +5. Limitations +-------------- + +Not all of the possible interactions will currently give meaningful +results. Bidirectional support (TLT and TRT) is complete. Some +subtleties in mixed vertical-horizontal writing still need to be +worked out. + |