Emacs-kp implements the knuth-plass typesetting algorithm, but its capabilities extend beyond English typesetting. Through further optimization of the algorithm, it achieves hybrid typesetting for both CJK and Latin-based languages.
First, let's look at a demo of the typesetting effect:
Currently, it only supports hybrid typesetting between CJK and one Latin-based language. Mixed typesetting with multiple Latin-based languages is not supported. This limitation arises because the system cannot precisely determine which language a word belongs to in order to perform hyphenation.
ekp-latin-lang is used to set the primary Latin-based language in the text. The default setting is "en_US". All supported languages can be found in the "dictionaries" directory. The language name must match the name following "hyph_" in the dictionary files. Test cases include examples of German and French typesetting. Other languages have not been tested extensively but should theoretically work; however, finer customization may be required.
ekp-param-set is a function used to configure fundamental typesetting parameters. These parameters include:
| Parameter | Meaning |
|---|---|
| ekp-lws-ideal-pixel | Ideal pixel width between Latin words |
| ekp-lws-stretch-pixel | Stretchable pixel width between Latin words |
| ekp-lws-shrink-pixel | Shrinkable pixel width between Latin words |
| ekp-mws-ideal-pixel | Ideal pixel width between Latin words and CJK characters |
| ekp-mws-stretch-pixel | Stretchable pixel width between Latin words and CJK characters |
| ekp-mws-shrink-pixel | Shrinkable pixel width between Latin words and CJK characters |
| ekp-cws-ideal-pixel | Ideal pixel width between CJK characters |
| ekp-cws-stretch-pixel | Stretchable pixel width between CJK characters |
| ekp-cws-shrink-pixel | Shrinkable pixel width between CJK characters |
For example: (ekp-param-set 7 3 2 5 2 1 0 2 0) sets the above parameters accordingly. Do not modify these variables directly – always use this function for configuration.
If not manually configured, the default values follow KP algorithm recommendations for spaces between latin words:
- The ideal width is set to the pixel width of a space character.
- The stretchable width defaults to 1/2 of the ideal width.
- The shrinkable width defaults to 1/3 of the ideal width.
For spaces between latin word and CJK character: ekp-mws-ideal-pixel = ekp-lws-ideal-pixel - 2 while maintaining the same stretch/shrink proportions.
For spaces between CJK characters: Ideal width between CJK characters defaults to 0. Stretchable width between CJK characters defaults to 2 pixels. Shrinkable width between CJK characters defaults to 0 (non-compressible).
Two functions are provided:
(ekp-pixel-justify string line-pixel)
Formats the text STRING to fit a pixel width of LINE-PIXEL per line and returns the justified text.
(ekp-pixel-range-justify string min-pixel max-pixel)
Searches for optimal typesetting within the range of MIN-PIXEL to MAX-PIXEL. Returns a cons-cell where the car is the formatted text and the cdr is the pixel value achieving the best typesetting result. Please Note: This function iteratively computes the typesetting cost between the minimum and maximum pixel values to find the optimal case at the minimum cost. If the specified range is too large, execution time may increase significantly. Future updates plan to leverage Rust dynamic libraries for parallel computation to improve performance.
- Preserve the original text's text properties.
- Refactor using Rust dynamic modules: Utilize Rust's parallel computing capabilities to enhance rendering performance.
- Implement autocorrection for punctuation: Correct English punctuation mistakenly used in Chinese text; Correct Chinese punctuation mistakenly used in English texts...
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The core algorithm is fundamentally derived from the seminal paper: "Breaking Paragraphs into Lines" by DONALD E. KNUTH AND MICHAEL F. PLASS.
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The implementation of Latin word hyphenation is adapted from the source code of the
Pyphen Python library, and the corresponding dictionaries originate from this project: https://github.com/Kozea/Pyphen