From 0d1ca2ac3805443690f3bcb6877251d9b74902c9 Mon Sep 17 00:00:00 2001 From: Yuan Fu Date: Tue, 26 May 2020 22:47:27 -0400 Subject: [PATCH] Improve word wrapping for CJK characters Note about the change around line 9257 and 23372: Before, the test for whitespace checks for can_wrap_before and can_wrap_after simutaniously. Now we separate these two checks, and the logic needs to change a little bit. However, when we don't enable the new wrapping feature, 'can_wrap_after' is equivalent to 'IT_DISPLAYING_WHITESPACE' and 'can_wrap_before' is equivalent to '!IT_DISPLAYING_WHITESPACE'. And the new logic is equivalent with the old one in that case. Old logic: if (whitespace) /* Which means can wrap after && can't wrap before. */ may_wrap = true; else if (may_wrap) /* aka (!whitespace && may_wrap) (set wrap point) * aka (can't wrap after && can wrap before may_wrap = false * && may_wrap) */ New logic: if (can_wrap_after) next_may_wrap = true else next_may_wrap = false; if (may_wrap && can_wrap_before) (set wrap point) /* Update may_wrap. */ may_wrap = next_may_wrap; * src/xdisp.c (it_char_has_category, char_can_wrap_before) (char_can_wrap_after): New functions. (move_it_in_display_line_to, display_line): Replace calls to 'IT_DISPLAYING_WHITESPACE' with either 'char_can_wrap_before' or 'char_can_wrap_after'. (word-wrap-by-category): New variable. * lisp/cus-start.el (minibuffer-prompt-properties--setter): Add 'word-wrap-by-category' as a customizable variable. * doc/emacs/display.texi (Visual Line Mode): Add a paragraph about the new 'word-wrap-by-category' feature. * etc/NEWS: Announce the change. --- doc/emacs/display.texi | 21 +++++ etc/NEWS | 6 ++ lisp/cus-start.el | 5 ++ src/xdisp.c | 189 ++++++++++++++++++++++++++++++++--------- 4 files changed, 183 insertions(+), 38 deletions(-) diff --git a/doc/emacs/display.texi b/doc/emacs/display.texi index 75ef520d62a..d56a135b640 100644 --- a/doc/emacs/display.texi +++ b/doc/emacs/display.texi @@ -1808,6 +1808,27 @@ logical lines, so having a fringe indicator for each wrapped line would be visually distracting. You can change this by customizing the variable @code{visual-line-fringe-indicators}. +@vindex word-wrap-by-category +@findex modify-category-entry +@findex char-category-set +@findex category-set-mnemonics + By default, Emacs only breaks lines after whitespace characters. +That strategy produces bad results when CJK and Latin text are mixed +together (because CJK characters don't use whitespace to separate +words). You can customize @code{word-wrap-by-category} to allow Emacs +to break lines after any character with ``|'' category +(@pxref{Categories,,, elisp, the Emacs Lisp Reference Manual}), which +includes CJK characters. Also, if this variable is set using +Customize, Emacs automatically loads kinsoku.el. When kinsoku.el is +loaded, Emacs respects kinsoku rules when breaking lines. That means +characters with the ``>'' category don't appear at the beginning of a +line (e.g., FULLWIDTH COMMA), and characters with the ``<'' category +don't appear at the end of a line (e.g., LEFT DOUBLE ANGLE BRACKET). +You can view the categories of a character by @code{char-category-set} +and @code{category-set-mnemonics}, or type @kbd{C-u C-x =} with point +on the character and look at the ``category'' section in the report. +You can add categories to a character by @code{modify-category-entry}. + @node Display Custom @section Customization of Display diff --git a/etc/NEWS b/etc/NEWS index 736892db8eb..42713642587 100644 --- a/etc/NEWS +++ b/etc/NEWS @@ -93,6 +93,12 @@ specify 'cursor-type' to be '(box . SIZE)', the cursor becomes a hollow box if the point is on an image larger than 'SIZE' pixels in any dimension. +** New custom option 'word-wrap-by-category'. + +When word-wrap is enabled, this option allows Emacs to break lines +after more characters (instead of just whitespace characters), that +means word-wrapping for CJK text mixed with Latin text is improved. + --- *** Improved language transliteration in Malayalam input methods. Added a new Mozhi scheme. The inapplicable ITRANS scheme is now diff --git a/lisp/cus-start.el b/lisp/cus-start.el index 6632687da47..7ecb7b51bec 100644 --- a/lisp/cus-start.el +++ b/lisp/cus-start.el @@ -98,6 +98,11 @@ (ctl-arrow display boolean) (truncate-lines display boolean) (word-wrap display boolean) + (word-wrap-by-category + display boolean "28.1" + :set (lambda (symbol value) + (set-default symbol value) + (when value (load "kinsoku.el")))) (selective-display-ellipses display boolean) (indicate-empty-lines fringe boolean) (indicate-buffer-boundaries diff --git a/src/xdisp.c b/src/xdisp.c index ad03ac46054..a1f7706ead2 100644 --- a/src/xdisp.c +++ b/src/xdisp.c @@ -447,6 +447,7 @@ along with GNU Emacs. If not, see . */ #include "termchar.h" #include "dispextern.h" #include "character.h" +#include "category.h" #include "buffer.h" #include "charset.h" #include "indent.h" @@ -508,6 +509,80 @@ static Lisp_Object list_of_error; && (*BYTE_POS_ADDR (IT_BYTEPOS (*it)) == ' ' \ || *BYTE_POS_ADDR (IT_BYTEPOS (*it)) == '\t')))) +/* These are the category sets we use. They are defined by + kinsoku.el and chracters.el. */ +#define NOT_AT_EOL '<' +#define NOT_AT_BOL '>' +#define LINE_BREAKABLE '|' + +static bool +it_char_has_category(struct it *it, int cat) +{ + int ch = 0; + if (it->what == IT_CHARACTER) + ch = it->c; + else if (STRINGP (it->string)) + ch = SREF (it->string, IT_STRING_BYTEPOS (*it)); + else if (it->s) + ch = it->s[IT_BYTEPOS (*it)]; + else if (IT_BYTEPOS (*it) < ZV_BYTE) + ch = *BYTE_POS_ADDR (IT_BYTEPOS (*it)); + + if (ch == 0) + return false; + else + return CHAR_HAS_CATEGORY (ch, cat); +} + +/* Return true if the current character allows wrapping before it. */ +static bool +char_can_wrap_before (struct it *it) +{ + if (!Vword_wrap_by_category) + return !IT_DISPLAYING_WHITESPACE (it); + + /* For CJK (LTR) text in RTL paragraph, EOL and BOL are flipped. + Because in RTL paragraph, each glyph is prepended to the last + one, effectively drawing right to left. */ + int not_at_bol; + if (it->glyph_row && it->glyph_row->reversed_p) + not_at_bol = NOT_AT_EOL; + else + not_at_bol = NOT_AT_BOL; + /* You cannot wrap before a space or tab because that way you'll + have space and tab at the beginning of next line. */ + return (!IT_DISPLAYING_WHITESPACE (it) + /* Can be at BOL. */ + && !it_char_has_category (it, not_at_bol)); +} + +/* Return true if the current character allows wrapping after it. */ +static bool +char_can_wrap_after (struct it *it) +{ + if (!Vword_wrap_by_category) + return IT_DISPLAYING_WHITESPACE (it); + + /* For CJK (LTR) text in RTL paragraph, EOL and BOL are flipped. + Because in RTL paragraph, each glyph is prepended to the last + one, effectively drawing right to left. */ + int not_at_eol; + if (it->glyph_row && it->glyph_row->reversed_p) + not_at_eol = NOT_AT_BOL; + else + not_at_eol = NOT_AT_EOL; + + return (IT_DISPLAYING_WHITESPACE (it) + /* Can break after && can be at EOL. */ + || (it_char_has_category (it, LINE_BREAKABLE) + && !it_char_has_category (it, not_at_eol))); +} + +#undef IT_DISPLAYING_WHITESPACE +#undef NOT_AT_EOL +#undef NOT_AT_BOL +#undef LINE_BREAKABLE + /* If all the conditions needed to print the fill column indicator are met, return the (nonnegative) column number, else return a negative value. */ @@ -9193,13 +9268,20 @@ move_it_in_display_line_to (struct it *it, { if (it->line_wrap == WORD_WRAP && it->area == TEXT_AREA) { - if (IT_DISPLAYING_WHITESPACE (it)) - may_wrap = true; - else if (may_wrap) + bool next_may_wrap = may_wrap; + /* Can we wrap after this character? */ + if (char_can_wrap_after (it)) + next_may_wrap = true; + else + next_may_wrap = false; + /* Can we wrap here? */ + if (may_wrap && char_can_wrap_before (it)) { /* We have reached a glyph that follows one or more - whitespace characters. If the position is - already found, we are done. */ + whitespace characters or a character that allows + wrapping after it. If this character allows + wrapping before it, save this position as a + wrapping point. */ if (atpos_it.sp >= 0) { RESTORE_IT (it, &atpos_it, atpos_data); @@ -9214,8 +9296,10 @@ move_it_in_display_line_to (struct it *it, } /* Otherwise, we can wrap here. */ SAVE_IT (wrap_it, *it, wrap_data); - may_wrap = false; + next_may_wrap = false; } + /* Update may_wrap for the next iteration. */ + may_wrap = next_may_wrap; } } @@ -9343,10 +9427,10 @@ move_it_in_display_line_to (struct it *it, { bool can_wrap = true; - /* If we are at a whitespace character - that barely fits on this screen line, - but the next character is also - whitespace, we cannot wrap here. */ + /* If the previous character says we can + wrap after it, but the current + character says we can't wrap before + it, then we can't wrap here. */ if (it->line_wrap == WORD_WRAP && wrap_it.sp >= 0 && may_wrap @@ -9358,7 +9442,7 @@ move_it_in_display_line_to (struct it *it, SAVE_IT (tem_it, *it, tem_data); set_iterator_to_next (it, true); if (get_next_display_element (it) - && IT_DISPLAYING_WHITESPACE (it)) + && !char_can_wrap_before (it)) can_wrap = false; RESTORE_IT (it, &tem_it, tem_data); } @@ -9437,19 +9521,18 @@ move_it_in_display_line_to (struct it *it, else IT_RESET_X_ASCENT_DESCENT (it); - /* If the screen line ends with whitespace, and we - are under word-wrap, don't use wrap_it: it is no - longer relevant, but we won't have an opportunity - to update it, since we are done with this screen - line. */ + /* If the screen line ends with whitespace (or + wrap-able character), and we are under word-wrap, + don't use wrap_it: it is no longer relevant, but + we won't have an opportunity to update it, since + we are done with this screen line. */ if (may_wrap && IT_OVERFLOW_NEWLINE_INTO_FRINGE (it) /* If the character after the one which set the - may_wrap flag is also whitespace, we can't - wrap here, since the screen line cannot be - wrapped in the middle of whitespace. - Therefore, wrap_it _is_ relevant in that - case. */ - && !(moved_forward && IT_DISPLAYING_WHITESPACE (it))) + may_wrap flag says we can't wrap before it, + we can't wrap here. Therefore, wrap_it + (previously found wrap-point) _is_ relevant + in that case. */ + && !(moved_forward && char_can_wrap_before (it))) { /* If we've found TO_X, go back there, as we now know the last word fits on this screen line. */ @@ -23322,9 +23405,14 @@ display_line (struct it *it, int cursor_vpos) if (it->line_wrap == WORD_WRAP && it->area == TEXT_AREA) { - if (IT_DISPLAYING_WHITESPACE (it)) - may_wrap = true; - else if (may_wrap) + bool next_may_wrap = may_wrap; + /* Can we wrap after this character? */ + if (char_can_wrap_after (it)) + next_may_wrap = true; + else + next_may_wrap = false; + /* Can we wrap here? */ + if (may_wrap && char_can_wrap_before (it)) { SAVE_IT (wrap_it, *it, wrap_data); wrap_x = x; @@ -23338,8 +23426,9 @@ display_line (struct it *it, int cursor_vpos) wrap_row_min_bpos = min_bpos; wrap_row_max_pos = max_pos; wrap_row_max_bpos = max_bpos; - may_wrap = false; } + /* Update may_wrap for the next iteration. */ + may_wrap = next_may_wrap; } } @@ -23463,14 +23552,18 @@ display_line (struct it *it, int cursor_vpos) /* If line-wrap is on, check if a previous wrap point was found. */ if (!IT_OVERFLOW_NEWLINE_INTO_FRINGE (it) - && wrap_row_used > 0 + && wrap_row_used > 0 /* Found. */ /* Even if there is a previous wrap point, continue the line here as usual, if (i) the previous character - was a space or tab AND (ii) the - current character is not. */ - && (!may_wrap - || IT_DISPLAYING_WHITESPACE (it))) + allows wrapping after it, AND (ii) + the current character allows wrapping + before it. Because this is a valid + break point, we can just continue to + the next line at here, there is no + need to wrap early at the previous + wrap point. */ + && (!may_wrap || !char_can_wrap_before (it))) goto back_to_wrap; /* Record the maximum and minimum buffer @@ -23498,13 +23591,16 @@ display_line (struct it *it, int cursor_vpos) /* If line-wrap is on, check if a previous wrap point was found. */ else if (wrap_row_used > 0 - /* Even if there is a previous wrap - point, continue the line here as - usual, if (i) the previous character - was a space or tab AND (ii) the - current character is not. */ - && (!may_wrap - || IT_DISPLAYING_WHITESPACE (it))) + /* Even if there is a previous + wrap point, continue the + line here as usual, if (i) + the previous character was a + space or tab AND (ii) the + current character is not, + AND (iii) the current + character allows wrapping + before it. */ + && (!may_wrap || !char_can_wrap_before (it))) goto back_to_wrap; } @@ -34662,6 +34758,23 @@ A value of nil means to respect the value of `truncate-lines'. If `word-wrap' is enabled, you might want to reduce this. */); Vtruncate_partial_width_windows = make_fixnum (50); + DEFVAR_BOOL("word-wrap-by-category", Vword_wrap_by_category, doc: /* + Non-nil means also wrap after characters of a certain category. +Normally when `word-wrap' is on, Emacs only breaks lines after +whitespace characters. When this option is turned on, Emacs also +breaks lines after characters that have the "|" category (defined in +characters.el). This is useful for allowing breaking after CJK +characters and improves the word-wrapping for CJK text mixed with +Latin text. + +If this variable is set using Customize, Emacs automatically loads +kinsoku.el. When kinsoku.el is loaded, Emacs respects kinsoku rules +when breaking lines. That means characters with the ">" category +don't appear at the beginning of a line (e.g., FULLWIDTH COMMA), and +characters with the "<" category don't appear at the end of a line +(e.g., LEFT DOUBLE ANGLE BRACKET). */); + Vword_wrap_by_category = false; + DEFVAR_LISP ("line-number-display-limit", Vline_number_display_limit, doc: /* Maximum buffer size for which line number should be displayed. If the buffer is bigger than this, the line number does not appear -- 2.39.2