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Fix #124: add ability to move to LSP-precise columns
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Also close #125.

Idea and much of design contributed by Michał Krzywkowski
<k.michal@zoho.com>

This introduces the variable eglot-move-to-column-function.

According to the standard, LSP column/character offsets are based
on a count of UTF-16 code units, not actual visual columns.  So
when LSP says position 3 of a line containing just \"aXbc\",
where X is a multi-byte character, it actually means `b', not
`c'.  This is what the function
`eglot-move-to-lsp-abiding-column' does.

However, many servers don't follow the spec this closely, and
thus this variable should be set to `move-to-column' in buffers
managed by those servers.

* eglot.el (eglot-move-to-column-function): New variable.
(eglot-move-to-lsp-abiding-column): New function.
(eglot--lsp-position-to-point): Use eglot-move-to-column-function.

#124: joaotavora/eglot#124
#125: joaotavora/eglot#125
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joaotavora committed Nov 12, 2018
1 parent f8d7303 commit 0eb340d
Showing 1 changed file with 35 additions and 8 deletions.
43 changes: 35 additions & 8 deletions lisp/progmodes/eglot.el
Original file line number Diff line number Diff line change
Expand Up @@ -728,16 +728,43 @@ CONNECT-ARGS are passed as additional arguments to
:character (- (goto-char (or pos (point)))
(line-beginning-position)))))

(defvar eglot-move-to-column-function #'move-to-column
"How to move to a column reported by the LSP server.
According to the standard, LSP column/character offsets are based
on a count of UTF-16 code units, not actual visual columns. So
when LSP says position 3 of a line containing just \"aXbc\",
where X is a multi-byte character, it actually means `b', not
`c'. This is what the function
`eglot-move-to-lsp-abiding-column' does.
However, many servers don't follow the spec this closely, and
thus this variable should be set to `move-to-column' in buffers
managed by those servers.")

(defun eglot-move-to-lsp-abiding-column (column)
"Move to COLUMN abiding by the LSP spec."
(cl-loop
initially (move-to-column column)
with lbp = (line-beginning-position)
for diff = (- column
(/ (- (length (encode-coding-region lbp (point) 'utf-16 t))
2)
2))
until (zerop diff)
for offset = (max 1 (abs (/ diff 2)))
do (if (> diff 0) (forward-char offset) (backward-char offset))))

(defun eglot--lsp-position-to-point (pos-plist &optional marker)
"Convert LSP position POS-PLIST to Emacs point.
If optional MARKER, return a marker instead"
(save-excursion (goto-char (point-min))
(forward-line (min most-positive-fixnum
(plist-get pos-plist :line)))
(forward-char (min (plist-get pos-plist :character)
(- (line-end-position)
(line-beginning-position))))
(if marker (copy-marker (point-marker)) (point))))
(save-excursion
(goto-char (point-min))
(forward-line (min most-positive-fixnum
(plist-get pos-plist :line)))
(unless (eobp) ;; if line was excessive leave point at eob
(funcall eglot-move-to-column-function (plist-get pos-plist :character)))
(if marker (copy-marker (point-marker)) (point))))

(defun eglot--path-to-uri (path)
"URIfy PATH."
Expand Down Expand Up @@ -1040,7 +1067,7 @@ Uses THING, FACE, DEFS and PREPEND."
(priority . ,(+ 50 i))
(keymap . ,(let ((map (make-sparse-keymap)))
(define-key map [mouse-1]
(eglot--mouse-call 'eglot-code-actions))
(eglot--mouse-call 'eglot-code-actions))
map)))))


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