From: Keith David Bershatsky <esq@lawlist.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: emacs-devel@gnu.org
Subject: Re: Problems with move_it_in_display_line_to X when tabs exist.
Date: Mon, 15 Jan 2018 20:41:52 -0800 [thread overview]
Message-ID: <m21siq76un.wl%esq@lawlist.com> (raw)
[-- Attachment #1: Type: text/plain, Size: 2774 bytes --]
Thank you, Eli, for teaching me about "integer division". I have added that concept to my learning "todo list" and anticipate having a handle on that in the next couple of days.
GOAL: The goal is to interactively call (scroll-left 1) -- one or more times in a row -- and obtain the beginning _visible_ X and HPOS of the STRETCH tab; and, also obtain its _visible_ pixel-width.
The following screenshots with stderr results were obtained by calling the function debug-tab-pixel-width, which is contained in the attached patch.diff. I saw that x_produce_glyphs is able to achieve the correct it->pixel_width for the STRETCH tab when x0 >= it->lnum_pixel_width; however, it is run subsequent in time to when we call move_it_in_display_line_to.
0. Opening screenshot -- just setting up the test buffer.
https://www.lawlist.com/images/tab_width_bug_00.png
1. Place the cursor on the line that begins with a tab, and press the f5 key once.
https://www.lawlist.com/images/tab_width_bug_01.png
OBSERVATIONS (w->hscroll == 1): The expected result is that the STRETCH tab will have an it.pixel_width of 42. The third (3rd) iteration/loop has the wrong value; i.e., 49. The fourth (4th) iteration/loop has the correct value; i.e., 42. x_produce_glyphs runs subsequent in time and contains the desired value of 42 when x0 >= it->lnum_pixel_width.
2. With the cursor still on the line that began with a tab, Press the f5 key once.
https://www.lawlist.com/images/tab_width_bug_02.png
OBSERVATIONS (w->hscroll == 2): The expected result is that the STRETCH tab will have an it.pixel_width of 35; however, it has a value of 49 instead. x_produce_glyphs runs subsequent in time and contains the desired value of 35 when x0 >= it->lnum_pixel_width.
3. With the cursor still on the line that began with a tab, Press the f5 key once.
https://www.lawlist.com/images/tab_width_bug_03.png
OBSERVATIONS (w->hscroll == 3): The expected result is that the STRETCH tab will have an it.pixel_width of 28; however, it has a value of 49 instead. x_produce_glyphs runs subsequent in time and contains the desired value of 28 when x0 >= it->lnum_pixel_width.
LISP CODE (buffer-local):
(setq display-line-numbers t)
(setq buffer-display-table (make-display-table))
(aset buffer-display-table
?\t
(vector (make-glyph-code ?\u00BB 'font-lock-warning-face)
(make-glyph-code ?\t 'highlight)))
(setq tab-width 8)
(global-set-key [f5] (lambda () (interactive) (debug-tab-pixel-width)))
TEST TEXT (a tab, followed by some arbitrary letters such Hello-world) -- the text begins on line 13:
Hello-world.
C CODE: Apply the attached patch.diff to Emacs 26 as of 01/15/2018 bearing last commit 9f22b7d2317eff65897355dcf68ba10d521cfa5a.
[-- Attachment #2: patch.diff --]
[-- Type: application/diff, Size: 7581 bytes --]
next reply other threads:[~2018-01-16 4:41 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-16 4:41 Keith David Bershatsky [this message]
2018-01-16 17:00 ` Problems with move_it_in_display_line_to X when tabs exist Eli Zaretskii
-- strict thread matches above, loose matches on Subject: below --
2018-01-23 7:38 Keith David Bershatsky
2018-01-21 20:32 Keith David Bershatsky
2018-01-16 17:53 Keith David Bershatsky
2018-01-15 5:48 Keith David Bershatsky
2018-01-15 12:06 ` Eli Zaretskii
2017-12-06 16:24 Keith David Bershatsky
2017-12-04 8:03 Keith David Bershatsky
2017-12-04 3:01 Keith David Bershatsky
2017-12-04 16:26 ` Eli Zaretskii
2017-12-03 20:56 Keith David Bershatsky
2017-12-04 15:48 ` Eli Zaretskii
2017-12-03 3:38 Keith David Bershatsky
2017-12-03 14:29 ` Eli Zaretskii
2017-12-02 22:28 Keith David Bershatsky
2017-12-03 3:32 ` Eli Zaretskii
2017-12-02 19:52 Keith David Bershatsky
2017-12-02 21:14 ` Eli Zaretskii
2017-11-30 4:29 Keith David Bershatsky
2017-11-29 6:12 Keith David Bershatsky
2017-11-29 18:04 ` Eli Zaretskii
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