From: Dmitry Gutov <dgutov@yandex.ru>
To: Eli Zaretskii <eliz@gnu.org>
Cc: 20847@debbugs.gnu.org
Subject: bug#20847: [display engine] 25.0.50; company-mode popup makes point jump to an entirely different location
Date: Sun, 21 Jun 2015 16:56:56 +0300 [thread overview]
Message-ID: <5586C2A8.1020904@yandex.ru> (raw)
In-Reply-To: <83wpyyiond.fsf@gnu.org>
On 06/20/2015 02:51 PM, Eli Zaretskii wrote:
> In a nutshell, when a screen line ends in a newline that comes from an
> overlay string, we don't want to display the cursor on that line. The
> reasons are heuristic, but they give good results, and we used this
> heuristic for a very long time, so changing it now is out of question.
Do you have a scenario in mind that performs better under the current
behavior?
> Due to this, when you type Backspace to delete "l" in "hell", and the
> Company post-command-hook runs and puts an overlay string on the same
> line that begins with a newline, the display engine decides, after
> redrawing the window, that it doesn't want to put the cursor there,
> and looks for an alternative place. The first such place is after the
> overlay string, so point is moved there.
I can understand the scenario until now, but why move point?
Displaying cursor in a different place is relatively fine, but moving
the point is destructive.
> The font-lock part of this riddle is that when font-lock-mode is
> active in the buffer, making any changes to buffer text cause JIT Lock
> to spring to action, which doesn't really do anything, but disables a
> certain redisplay optimization, which bypasses the above test.
Sounds messy.
> My suggestion would be to use the 'cursor' property on the overlay
> string in some place where it could be picked up by the display engine
> (i.e. not on a newline), to countermand this problem.
See the bottom of `company--replacement-string'. If `cursor' is applied
unconditionally, and if I change the arguments 0 and 1 to 1 and 2, on
step 6 the cursor is displayed at the beginning of the next line (so we
know the change has effect), but the second problem (after step 9) is
still present.
> E.g., perhaps
> begin the overlay string a few characters earlier, so that it replaces
> part of buffer text in "hel", and have the 'cursor' property on that
> part of the string.
That's doable, even if I don't like the extra complexity. Are you sure
about this?
> I still think the overlay string is constructed incorrectly in this
> case, something that should be fixed in Company. The above special
> setting of 'cursor' could be part of that fix.
Do you also have explanations for the following?
- The bug only manifests after the step 9 (backspacing), whereas the
whole explanation seems to apply to the step 6 as well. Yet, point stays
in place there.
- With bidi-display-reordering set to nil, there's no bug.
next prev parent reply other threads:[~2015-06-21 13:56 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-19 1:04 bug#20847: [display engine] 25.0.50; company-mode popup makes point jump to an entirely different location Dmitry Gutov
2015-06-19 19:07 ` Eli Zaretskii
2015-06-20 11:51 ` Eli Zaretskii
2015-06-21 13:56 ` Dmitry Gutov [this message]
2015-06-21 16:43 ` Eli Zaretskii
2015-06-21 18:06 ` Dmitry Gutov
2015-06-21 18:24 ` Eli Zaretskii
2015-06-21 19:23 ` Eli Zaretskii
2015-06-21 20:17 ` Dmitry Gutov
2015-06-21 20:02 ` Dmitry Gutov
2015-06-22 2:45 ` Eli Zaretskii
2015-06-22 11:01 ` Dmitry Gutov
2015-06-22 13:40 ` Dmitry Gutov
2015-06-22 16:26 ` Eli Zaretskii
2015-06-22 21:06 ` Dmitry Gutov
2015-06-23 16:39 ` Eli Zaretskii
2015-06-23 18:44 ` Dmitry Gutov
2015-06-23 19:07 ` Eli Zaretskii
2015-06-23 21:15 ` Dmitry Gutov
2015-06-24 16:18 ` Eli Zaretskii
2015-06-29 15:48 ` Dmitry Gutov
2015-06-30 17:46 ` Eli Zaretskii
2015-06-30 19:41 ` Dmitry Gutov
2015-06-30 20:11 ` Eli Zaretskii
2015-06-30 20:20 ` Dmitry Gutov
2015-07-01 2:42 ` Eli Zaretskii
2015-07-01 10:21 ` Dmitry Gutov
2015-07-01 15:16 ` Eli Zaretskii
2015-07-01 16:36 ` Dmitry Gutov
2015-07-01 16:40 ` Eli Zaretskii
2015-06-21 13:30 ` Dmitry Gutov
2015-06-21 14:16 ` Dmitry Gutov
2015-06-21 16:24 ` Eli Zaretskii
2015-06-21 17:46 ` Dmitry Gutov
2015-06-21 18:09 ` Eli Zaretskii
2015-06-21 20:01 ` Dmitry Gutov
2015-06-22 2:43 ` Eli Zaretskii
2015-06-22 10:57 ` Dmitry Gutov
2015-06-22 16:23 ` Eli Zaretskii
2015-06-23 0:15 ` Dmitry Gutov
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