Commit 940f53e5 authored by Richard M. Stallman's avatar Richard M. Stallman
Browse files

(window_scroll_pixel_based): Only look at

Vscroll_preserve_screen_position if the old PT can't be kept.
(syms_of_window) <scroll-preserve-screen-position>: Doc fix.
parent 1241e32d
......@@ -4671,30 +4671,32 @@ window_scroll_pixel_based (window, n, whole, noerror)
not including the height of the header line if any. */
it.current_y = it.vpos = 0;
/* Preserve the screen position if we should. */
if (preserve_y >= 0)
/* Move PT out of scroll margins.
This code wants current_y to be zero at the window start position
even if there is a header line. */
this_scroll_margin = max (0, scroll_margin);
this_scroll_margin = min (this_scroll_margin, XFASTINT (w->total_lines) / 4);
this_scroll_margin *= FRAME_LINE_HEIGHT (it.f);
if (n > 0)
{
/* If we have a header line, take account of it. */
if (WINDOW_WANTS_HEADER_LINE_P (w))
preserve_y -= CURRENT_HEADER_LINE_HEIGHT (w);
/* We moved the window start towards ZV, so PT may be now
in the scroll margin at the top. */
move_it_to (&it, PT, -1, -1, -1, MOVE_TO_POS);
if (IT_CHARPOS (it) == PT && it.current_y >= this_scroll_margin)
/* We found PT at a legitimate height. Leave it alone. */
;
else if (preserve_y >= 0)
{
/* If we have a header line, take account of it. */
if (WINDOW_WANTS_HEADER_LINE_P (w))
preserve_y -= CURRENT_HEADER_LINE_HEIGHT (w);
move_it_to (&it, -1, -1, preserve_y, -1, MOVE_TO_Y);
SET_PT_BOTH (IT_CHARPOS (it), IT_BYTEPOS (it));
}
else
{
/* Move PT out of scroll margins.
This code wants current_y to be zero at the window start position
even if there is a header line. */
this_scroll_margin = max (0, scroll_margin);
this_scroll_margin = min (this_scroll_margin, XFASTINT (w->total_lines) / 4);
this_scroll_margin *= FRAME_LINE_HEIGHT (it.f);
if (n > 0)
move_it_to (&it, -1, -1, preserve_y, -1, MOVE_TO_Y);
SET_PT_BOTH (IT_CHARPOS (it), IT_BYTEPOS (it));
}
else
{
/* We moved the window start towards ZV, so PT may be now
in the scroll margin at the top. */
move_it_to (&it, PT, -1, -1, -1, MOVE_TO_POS);
while (it.current_y < this_scroll_margin)
{
int prev = it.current_y;
......@@ -4704,22 +4706,44 @@ window_scroll_pixel_based (window, n, whole, noerror)
}
SET_PT_BOTH (IT_CHARPOS (it), IT_BYTEPOS (it));
}
else if (n < 0)
{
int charpos, bytepos;
}
else if (n < 0)
{
int charpos, bytepos;
/* Save our position, for the preserve_y case. */
charpos = IT_CHARPOS (it);
bytepos = IT_BYTEPOS (it);
/* We moved the window start towards BEGV, so PT may be now
in the scroll margin at the bottom. */
move_it_to (&it, PT, -1,
it.last_visible_y - this_scroll_margin - 1, -1,
MOVE_TO_POS | MOVE_TO_Y);
/* We moved the window start towards BEGV, so PT may be now
in the scroll margin at the bottom. */
move_it_to (&it, PT, -1,
it.last_visible_y - this_scroll_margin - 1, -1,
MOVE_TO_POS | MOVE_TO_Y);
if (IT_CHARPOS (it) == PT)
/* We found PT before we found the display margin, so PT is ok. */
;
else if (preserve_y >= 0)
{
SET_TEXT_POS_FROM_MARKER (start, w->start);
start_display (&it, w, start);
/* If we have a header line, take account of it. */
if (WINDOW_WANTS_HEADER_LINE_P (w))
preserve_y -= CURRENT_HEADER_LINE_HEIGHT (w);
move_it_to (&it, -1, -1, preserve_y, -1, MOVE_TO_Y);
SET_PT_BOTH (IT_CHARPOS (it), IT_BYTEPOS (it));
}
else
{
/* Save our position, in case it's correct. */
charpos = IT_CHARPOS (it);
bytepos = IT_BYTEPOS (it);
/* See if point is on a partially visible line at the end. */
move_it_by_lines (&it, 1, 1);
if (it.current_y > it.last_visible_y)
/* The last line was only partially visible, so back up two
lines to make sure we're on a fully visible line. */
......@@ -6753,7 +6777,9 @@ If there is only one window, it is split regardless of this value. */);
DEFVAR_LISP ("scroll-preserve-screen-position",
&Vscroll_preserve_screen_position,
doc: /* *Non-nil means scroll commands move point to keep its screen line unchanged. */);
doc: /* *Non-nil means scroll commands move point to keep its screen line unchanged.
This is only when it is impossible to keep point fixed and still
scroll as specified. */);
Vscroll_preserve_screen_position = Qnil;
DEFVAR_LISP ("window-configuration-change-hook",
......
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