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Avoid segfaults in pos_visible_p

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* src/xdisp.c (pos_visible_p): Don't try accessing the glyphs
produced by iterator whose glyph_row was set to NULL; instead,
record the X coordinate before the display string when moving past
it, and use the recorded coordinate if needed.  (Bug#45156)
This commit is contained in:
Eli Zaretskii 2020-12-10 17:10:06 +02:00
parent 6596b5541d
commit 97c2bca729
1 changed files with 18 additions and 22 deletions
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40
src/xdisp.c
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@ -1925,12 +1925,12 @@ pos_visible_p (struct window *w, ptrdiff_t charpos, int *x, int *y,
/* If it3_moved stays false after the 'while' loop
below, that means we already were at a newline
before the loop (e.g., the display string begins
with a newline), so we don't need to (and cannot)
inspect the glyphs of it3.glyph_row, because
PRODUCE_GLYPHS will not produce anything for a
newline, and thus it3.glyph_row stays at its
stale content it got at top of the window. */
with a newline), so we don't need to return to
the last position before the display string,
because PRODUCE_GLYPHS will not produce anything
for a newline. */
bool it3_moved = false;
int top_x_before_string = it3.current_x;
/* Finally, advance the iterator until we hit the
first display element whose character position is
CHARPOS, or until the first newline from the
@ -1938,6 +1938,8 @@ pos_visible_p (struct window *w, ptrdiff_t charpos, int *x, int *y,
display line. */
while (get_next_display_element (&it3))
{
if (!EQ (it3.object, string))
top_x_before_string = it3.current_x;
PRODUCE_GLYPHS (&it3);
if (IT_CHARPOS (it3) == charpos
|| ITERATOR_AT_END_OF_LINE_P (&it3))
@ -1952,32 +1954,26 @@ pos_visible_p (struct window *w, ptrdiff_t charpos, int *x, int *y,
if (!it3.line_number_produced_p)
{
if (it3.lnum_pixel_width > 0)
top_x += it3.lnum_pixel_width;
{
top_x += it3.lnum_pixel_width;
top_x_before_string += it3.lnum_pixel_width;
}
else if (it.line_number_produced_p)
top_x += it.lnum_pixel_width;
{
top_x += it.lnum_pixel_width;
top_x_before_string += it3.lnum_pixel_width;
}
}
/* Normally, we would exit the above loop because we
found the display element whose character
position is CHARPOS. For the contingency that we
didn't, and stopped at the first newline from the
display string, move back over the glyphs
produced from the string, until we find the
rightmost glyph not from the string. */
display string, reset top_x to the coordinate of
the rightmost glyph not from the string. */
if (it3_moved
&& newline_in_string
&& IT_CHARPOS (it3) != charpos && EQ (it3.object, string))
{
struct glyph *g = it3.glyph_row->glyphs[TEXT_AREA]
+ it3.glyph_row->used[TEXT_AREA];
while (EQ ((g - 1)->object, string))
{
--g;
top_x -= g->pixel_width;
}
eassert (g < it3.glyph_row->glyphs[TEXT_AREA]
+ it3.glyph_row->used[TEXT_AREA]);
}
top_x = top_x_before_string;
}
}