diff options
Diffstat (limited to 'lisp/international/mule-util.el')
| -rw-r--r-- | lisp/international/mule-util.el | 38 |
1 files changed, 30 insertions, 8 deletions
diff --git a/lisp/international/mule-util.el b/lisp/international/mule-util.el index 55449599fe9..c2f91e77e7c 100644 --- a/lisp/international/mule-util.el +++ b/lisp/international/mule-util.el @@ -67,10 +67,15 @@ decide whether the selected frame can display that Unicode character." ellipsis-text-property) "Truncate string STR to end at column END-COLUMN. The optional 3rd arg START-COLUMN, if non-nil, specifies the starting -column; that means to return the characters occupying columns -START-COLUMN ... END-COLUMN of STR. Both END-COLUMN and START-COLUMN -are specified in terms of character display width in the current -buffer; see also `char-width'. +column (default: zero); that means to return the characters occupying +columns START-COLUMN ... END-COLUMN of STR. Both END-COLUMN and +START-COLUMN are specified in terms of character display width in the +current buffer; see `char-width'. + +Since character composition on display can produce glyphs whose +width is smaller than the sum of `char-width' values of the +composed characters, this function can produce inaccurate results +when used in such cases. The optional 4th arg PADDING, if non-nil, specifies a padding character (which should have a display width of 1) to add at the end @@ -333,13 +338,20 @@ QUALITY can be: `approximate', in which case we may cut some corners to avoid excessive work. `exact', in which case we may end up re-(en/de)coding a large - part of the file/buffer, this can be expensive and slow. + part of the file/buffer, this can be expensive and slow. (It + is an error to request the `exact' method when the buffer's + EOL format is not yet decided.) nil, in which case we may return nil rather than an approximation." (unless coding-system (setq coding-system buffer-file-coding-system)) (let ((eol (coding-system-eol-type coding-system)) (type (coding-system-type coding-system)) (base (coding-system-base coding-system)) (pm (save-restriction (widen) (point-min)))) + ;; Handle EOL edge cases. + (unless (numberp eol) + (if (eq quality 'exact) + (error "Unknown EOL format in coding system: %s" coding-system) + (setq eol 0))) (and (eq type 'utf-8) ;; Any post-read/pre-write conversions mean it's not really UTF-8. (not (null (coding-system-get coding-system :post-read-conversion))) @@ -409,14 +421,24 @@ QUALITY can be: `approximate', in which case we may cut some corners to avoid excessive work. `exact', in which case we may end up re-(en/de)coding a large - part of the file/buffer, this can be expensive and slow. + part of the file/buffer, this can be expensive and slow. (It + is an error to request the `exact' method when the buffer's + EOL format is not yet decided.) nil, in which case we may return nil rather than an approximation." (unless coding-system (setq coding-system buffer-file-coding-system)) (let* ((eol (coding-system-eol-type coding-system)) - (lineno (if (= eol 1) (1- (line-number-at-pos position)) 0)) (type (coding-system-type coding-system)) (base (coding-system-base coding-system)) - (point-min 1)) ;Clarify what the `1' means. + (point-min 1) ;Clarify what the `1' means. + lineno) + ;; Handle EOL edge cases. + (unless (numberp eol) + (if (eq quality 'exact) + (error "Unknown EOL format in coding system: %s" coding-system) + (setq eol 0))) + (setq lineno (if (= eol 1) + (1- (line-number-at-pos position)) + 0)) (and (eq type 'utf-8) ;; Any post-read/pre-write conversions mean it's not really UTF-8. (not (null (coding-system-get coding-system :post-read-conversion))) |