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Optionally allow point to enter composed character sequences

Browse source 
This changeset is based on code originally posted by
Kenichi Handa <handa@gnu.org> as part of discussing bug#20140,
with a few adjustments and changes, mainly to support R2L
text and provide a user option to control the feature.
* src/xdisp.c (compute_stop_pos, next_element_from_buffer)
(composition_reseat_it): Don't allow auto-composing characters
past point when 'composition-break-at-point' is non-nil.
(syms_of_xdisp) <composition-break-at-point>: New boolean variable.
(redisplay_internal, redisplay_window): Disable "just move the
cursor" optimizations when 'composition-break-at-point' is non-nil.
* src/keyboard.c (command_loop_1): Force redisplay when
'composition-break-at-point' is non-nil.

* lisp/cus-start.el (standard): Provide customization form for
'composition-break-at-point'.

* etc/NEWS: Announce the new feature.
This commit is contained in:
Eli Zaretskii 2022-02-12 20:38:51 +02:00
parent 09fecae877
commit b5997c0f10
5 changed files with 79 additions and 19 deletions
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11
etc/NEWS
View file

@ -476,6 +476,17 @@ The options 'mouse-wheel-down-alternate-event', 'mouse-wheel-up-alternate-event'
been added to better support systems where two kinds of wheel events can be
received.
** Editing complex text layout (CTL) scripts
*** The <Delete> function key now allows deleting the entire composed sequence.
For the details, see the item about the 'delete-forward-char' command
above.
*** New user option 'composition-break-at-point'.
Setting it to a non-nil value temporarily disables automatic
composition of character sequences at point, and thus makes it easier
to edit such sequences by allowing point to "enter" the sequence.
* Changes in Specialized Modes and Packages in Emacs 29.1

1
lisp/cus-start.el
View file

@ -811,6 +811,7 @@ since it could result in memory overflow and make Emacs crash."
character)
"27.1"
:safe (lambda (value) (or (characterp value) (null value))))
(composition-break-at-point display boolean "29.1")
;; xfaces.c
(scalable-fonts-allowed
display (choice (const :tag "Don't allow scalable fonts" nil)

10
src/composite.c
View file

@ -1292,6 +1292,16 @@ composition_reseat_it (struct composition_it *cmp_it, ptrdiff_t charpos,
if (cmp_it->lookback > 0)
{
cpos = charpos - cmp_it->lookback;
/* Reject the composition if it starts before ENDPOS,
which here can only happen if
composition-break-at-point is non-nil and point is
inside the composition. */
if (cpos < endpos)
{
eassert (composition_break_at_point);
eassert (endpos == PT);
goto no_composition;
}
if (STRINGP (string))
bpos = string_char_to_byte (string, cpos);
else

42
src/keyboard.c
View file

@ -1603,23 +1603,33 @@ command_loop_1 (void)
if (current_buffer == prev_buffer
&& XBUFFER (XWINDOW (selected_window)->contents) == current_buffer
&& last_point_position != PT
&& NILP (Vdisable_point_adjustment)
&& NILP (Vglobal_disable_point_adjustment))
&& last_point_position != PT)
{
if (last_point_position > BEGV
&& last_point_position < ZV
&& (composition_adjust_point (last_point_position,
last_point_position)
!= last_point_position))
/* The last point was temporarily set within a grapheme
cluster to prevent automatic composition. To recover
the automatic composition, we must update the
display. */
windows_or_buffers_changed = 21;
if (!already_adjusted)
adjust_point_for_property (last_point_position,
MODIFF != prev_modiff);
if (NILP (Vdisable_point_adjustment)
&& NILP (Vglobal_disable_point_adjustment)
&& !composition_break_at_point)
{
if (last_point_position > BEGV
&& last_point_position < ZV
&& (composition_adjust_point (last_point_position,
last_point_position)
!= last_point_position))
/* The last point was temporarily set within a grapheme
cluster to prevent automatic composition. To recover
the automatic composition, we must update the
display. */
windows_or_buffers_changed = 21;
if (!already_adjusted)
adjust_point_for_property (last_point_position,
MODIFF != prev_modiff);
}
else if (PT > BEGV && PT < ZV
&& (composition_adjust_point (last_point_position, PT)
!= PT))
/* Now point is within a grapheme cluster. We must update
the display so that this cluster is de-composed on the
screen and the cursor is correctly placed at point. */
windows_or_buffers_changed = 39;
}
/* Install chars successfully executed in kbd macro. */

34
src/xdisp.c
View file

@ -3984,6 +3984,12 @@ compute_stop_pos (struct it *it)
pos = next_overlay_change (charpos);
if (pos < it->stop_charpos)
it->stop_charpos = pos;
/* If we are breaking compositions at point, stop at point. */
if (!NILP (BVAR (current_buffer, enable_multibyte_characters))
&& !NILP (Vauto_composition_mode)
&& composition_break_at_point
&& charpos < PT && PT < it->stop_charpos)
it->stop_charpos = PT;
/* Set up variables for computing the stop position from text
property changes. */
@ -3995,7 +4001,8 @@ compute_stop_pos (struct it *it)
chunks. We play safe here by assuming that only SPC, TAB,
FF, and NL cannot be in some composition; in particular, most
ASCII punctuation characters could be composed into ligatures. */
if (!NILP (BVAR (current_buffer, enable_multibyte_characters))
if (!composition_break_at_point
&& !NILP (BVAR (current_buffer, enable_multibyte_characters))
&& !NILP (Vauto_composition_mode))
{
ptrdiff_t endpos = charpos + 10 * TEXT_PROP_DISTANCE_LIMIT;
@ -9186,7 +9193,19 @@ next_element_from_buffer (struct it *it)
&& IT_CHARPOS (*it) >= it->redisplay_end_trigger_charpos)
run_redisplay_end_trigger_hook (it);
stop = it->bidi_it.scan_dir < 0 ? -1 : it->end_charpos;
if (composition_break_at_point
&& !NILP (BVAR (current_buffer, enable_multibyte_characters))
&& !NILP (Vauto_composition_mode))
{
/* Limit search for composable characters to point's position. */
if (it->bidi_it.scan_dir < 0)
stop = (PT <= IT_CHARPOS (*it)) ? PT : -1;
else
stop = (IT_CHARPOS (*it) < PT
&& PT < it->end_charpos) ? PT : it->end_charpos;
}
else
stop = it->bidi_it.scan_dir < 0 ? -1 : it->end_charpos;
if (CHAR_COMPOSED_P (it, IT_CHARPOS (*it), IT_BYTEPOS (*it),
stop)
&& next_element_from_composition (it))
@ -16390,7 +16409,8 @@ redisplay_internal (void)
/* If highlighting the region, or if the cursor is in the echo area,
then we can't just move the cursor. */
else if (NILP (Vshow_trailing_whitespace)
&& !cursor_in_echo_area)
&& !cursor_in_echo_area
&& !composition_break_at_point)
{
struct it it;
struct glyph_row *row;
@ -18928,6 +18948,7 @@ redisplay_window (Lisp_Object window, bool just_this_one_p)
&& !current_buffer->clip_changed
&& !current_buffer->prevent_redisplay_optimizations_p
&& !window_outdated (w)
&& !composition_break_at_point
&& !hscrolling_current_line_p (w));
beg_unchanged = BEG_UNCHANGED;
@ -36527,6 +36548,13 @@ Otherwise, use custom-tailored code after resizing minibuffer windows to try
and display the most important part of the minibuffer. */);
/* See bug#43519 for some discussion around this. */
redisplay_adhoc_scroll_in_resize_mini_windows = true;
DEFVAR_BOOL ("composition-break-at-point",
composition_break_at_point,
doc: /* If non-nil, prevent auto-composition of characters around point.
This makes it easier to edit character sequences that are
composed on display. */);
composition_break_at_point = false;
}