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Support lower bound on hscrolling when only current line scrolls

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* doc/emacs/display.texi (Horizontal Scrolling): Document the new
mode of auto-hscrolling only the current line.

* src/xdisp.c (init_iterator): When hscrolling only the
current line, apply the	window's min_hscroll here, so that
non-current lines will be hscrolled by that minimum.
Suggested by Stephen Berman <stephen.berman@gmx.net>.
(hscroll_window_tree): Account for window's min_hscroll when
deciding whether to recompute the hscroll.
(display_line): Subtract window's min_hscroll from x_incr, as that
was already accounted for in init_iterator.  (Bug#27008)
This commit is contained in:
Eli Zaretskii 2017-05-31 19:01:31 +03:00
parent a415c8bccb
commit 140ddc321b
3 changed files with 30 additions and 6 deletions
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11
doc/emacs/display.texi
View File

@ -308,7 +308,11 @@ displayed. When the text in a window is scrolled horizontally, text
lines are truncated rather than continued (@pxref{Line Truncation}).
If a window shows truncated lines, Emacs performs automatic horizontal
scrolling whenever point moves off the left or right edge of the
screen. To disable automatic horizontal scrolling, set the variable
screen. By default, all the lines in the window are scrolled
horizontally together, but if you set the variable
@code{auto-hscroll-mode} to the special value of @code{current-line},
only the line showing the cursor will be scrolled. To disable
automatic horizontal scrolling entirely, set the variable
@code{auto-hscroll-mode} to @code{nil}. Note that when the automatic
horizontal scrolling is turned off, if point moves off the edge of the
screen, the cursor disappears to indicate that. (On text terminals,
@ -366,7 +370,10 @@ sufficiently large argument will restore the normal display.
If you use those commands to scroll a window horizontally, that sets
a lower bound for automatic horizontal scrolling. Automatic scrolling
will continue to scroll the window, but never farther to the right
than the amount you previously set by @code{scroll-left}.
than the amount you previously set by @code{scroll-left}. When
@code{auto-hscroll-mode} is set to @code{current-line}, all the lines
other than the one showing the cursor will be scrolled by that minimal
amount.
@node Narrowing
@section Narrowing

1
etc/NEWS
View File

@ -377,6 +377,7 @@ you may set this variable to nil. (Behind the scenes, there is now a
new mode line construct, '%C', which operates exactly as '%c' does
except that it counts from one.)
+++
** New single-line horizontal scrolling mode.
The 'auto-hscroll-mode' variable can now have a new special value,
'current-line', which causes only the line where the cursor is

24
src/xdisp.c
View File

@ -2890,8 +2890,19 @@ init_iterator (struct it *it, struct window *w,
}
else
{
/* When hscrolling only the current line, don't apply the
hscroll here, it will be applied by display_line when it gets
to laying out the line showing point. However, if the
window's min_hscroll is positive, the user specified a lower
bound for automatic hscrolling, so they expect the
non-current lines to obey that hscroll amount. */
if (hscrolling_current_line_p (w))
it->first_visible_x = 0;
{
if (w->min_hscroll > 0)
it->first_visible_x = w->min_hscroll * FRAME_COLUMN_WIDTH (it->f);
else
it->first_visible_x = 0;
}
else
it->first_visible_x =
window_hscroll_limited (w, it->f) * FRAME_COLUMN_WIDTH (it->f);
@ -13099,7 +13110,9 @@ hscroll_window_tree (Lisp_Object window)
that doesn't need to be hscrolled. If we omit
this condition, the line from which we move will
remain hscrolled. */
|| (hscl && w->hscroll && !cursor_row->truncated_on_left_p)))
|| (hscl
&& w->hscroll != w->min_hscroll
&& !cursor_row->truncated_on_left_p)))
{
struct it it;
ptrdiff_t hscroll;
@ -20717,9 +20730,12 @@ display_line (struct it *it, int cursor_vpos)
recenter_overlay_lists (current_buffer, IT_CHARPOS (*it));
/* If we are going to display the cursor's line, account for the
hscroll of that line. */
hscroll of that line. We subtract the window's min_hscroll,
because that was already accounted for in init_iterator. */
if (hscroll_this_line)
x_incr = window_hscroll_limited (it->w, it->f) * FRAME_COLUMN_WIDTH (it->f);
x_incr =
(window_hscroll_limited (it->w, it->f) - it->w->min_hscroll)
* FRAME_COLUMN_WIDTH (it->f);
/* Move over display elements that are not visible because we are
hscrolled. This may stop at an x-position < first_visible_x