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bug#39133: 28.0.50; Emacs slowdown on special char
From: |
YAMAMOTO Mitsuharu |
Subject: |
bug#39133: 28.0.50; Emacs slowdown on special char |
Date: |
Wed, 15 Jan 2020 13:26:11 +0900 |
User-agent: |
Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (Gojō) APEL/10.8 EasyPG/1.0.0 Emacs/26 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) |
On Wed, 15 Jan 2020 01:24:05 +0900,
Robert Pluim wrote:
>
> >>>>> On Tue, 14 Jan 2020 17:26:45 +0200, Eli Zaretskii <eliz@gnu.org> said:
>
> >> From: Evgeny Zajcev <lg.zevlg@gmail.com>
> >> Date: Tue, 14 Jan 2020 16:21:23 +0300
> >>
> >> I'm experiencing extreme Emacs slowdown when VARIATION SELECTOR-16 char
> >> is used somewhere in Emacs buffer. For example, I just executed:
> >>
> >> (insert "a\xfe0f")
> >>
> >> in *scratch* buffer. Moving cursor (when this char is visible) become
> >> unbearable. Here is the results of cpu profiling:
> >>
> >> - command-execute 776
> 62%
> >> - call-interactively 776
> 62%
> >> - funcall-interactively 675
> 54%
> >> - previous-line 476 38%
> >> - line-move 476 38%
> >> - line-move-1 476 38%
> >> + vertical-motion 225 18%
>
> Eli> Does it help to set inhibit-compacting-font-caches non-nil?
>
> >> As I remember I did not experienced something similar in Emacs 26/27
>
> Eli> I don't think Emacs < 27 supported variation selectors, did it?
>
> Itʼs coming from the caching in ftcrfont_glyph_extents:
>
> row = glyph / METRICS_NCOLS_PER_ROW; <== glyph == 0xFFFFFFFF, row ->
> 0x1FFFFFF
> col = glyph % METRICS_NCOLS_PER_ROW;
> if (row >= ftcrfont_info->metrics_nrows)
> {
> ftcrfont_info->metrics =
> xrealloc (ftcrfont_info->metrics,
> sizeof (struct font_metrics *) * (row + 1));
> memset (ftcrfont_info->metrics + ftcrfont_info->metrics_nrows, 0,
> (sizeof (struct font_metrics *)
> * (row + 1 - ftcrfont_info->metrics_nrows)));
> ftcrfont_info->metrics_nrows = row + 1; <=== weʼre updating
> metrics_nrows, lets look in ftfont.h
> }
>
> ftfont.h:
>
> #ifdef USE_CAIRO
> cairo_scaled_font_t *cr_scaled_font;
> /* Scale factor from the bitmap strike metrics in 1/64 pixels, used
> as the hb_position_t value in HarfBuzz, to those in (scaled)
> pixels. The value is 0 for scalable fonts. */
> double bitmap_position_unit;
> /* Font metrics cache. */
> struct font_metrics **metrics;
> short metrics_nrows;
> ^^^^^ oops! Now we end up calling xrealloc every time we enter
> ftctfont_glyph_extents for that glyph.
>
> Of course, I donʼt think glyph should be 0xFFFFFFFF, but thatʼs a
> different problem.
>
> Robert
0xFFFFFFFF comes from FONT_INVALID_CODE. font->driver->text_extents
shouldn't be called if font->font->driver->encode_char returns it.
diff --git a/src/font.c b/src/font.c
index 2b90903c90..03e6176220 100644
--- a/src/font.c
+++ b/src/font.c
@@ -4420,15 +4420,19 @@ font_fill_lglyph_metrics (Lisp_Object glyph,
Lisp_Object font_object)
{
struct font *font = XFONT_OBJECT (font_object);
unsigned code = font->driver->encode_char (font, LGLYPH_CHAR (glyph));
- struct font_metrics metrics;
-
- LGLYPH_SET_CODE (glyph, code);
- font->driver->text_extents (font, &code, 1, &metrics);
- LGLYPH_SET_LBEARING (glyph, metrics.lbearing);
- LGLYPH_SET_RBEARING (glyph, metrics.rbearing);
- LGLYPH_SET_WIDTH (glyph, metrics.width);
- LGLYPH_SET_ASCENT (glyph, metrics.ascent);
- LGLYPH_SET_DESCENT (glyph, metrics.descent);
+
+ if (code != FONT_INVALID_CODE)
+ {
+ struct font_metrics metrics;
+
+ LGLYPH_SET_CODE (glyph, code);
+ font->driver->text_extents (font, &code, 1, &metrics);
+ LGLYPH_SET_LBEARING (glyph, metrics.lbearing);
+ LGLYPH_SET_RBEARING (glyph, metrics.rbearing);
+ LGLYPH_SET_WIDTH (glyph, metrics.width);
+ LGLYPH_SET_ASCENT (glyph, metrics.ascent);
+ LGLYPH_SET_DESCENT (glyph, metrics.descent);
+ }
}
But I'm not sure if it is ok to leave the code and metrics-related
fields nil when encode_char returns FONT_INVALID_CODE. Handa-san?
YAMAMOTO Mitsuharu
mituharu@math.s.chiba-u.ac.jp
- bug#39133: 28.0.50; Emacs slowdown on special char, Evgeny Zajcev, 2020/01/14
- bug#39133: 28.0.50; Emacs slowdown on special char, Eli Zaretskii, 2020/01/14
- bug#39133: 28.0.50; Emacs slowdown on special char, Robert Pluim, 2020/01/14
- bug#39133: 28.0.50; Emacs slowdown on special char, Eli Zaretskii, 2020/01/15
- bug#39133: 28.0.50; Emacs slowdown on special char, Robert Pluim, 2020/01/24
- bug#39133: 28.0.50; Emacs slowdown on special char, Eli Zaretskii, 2020/01/24
- bug#39133: 28.0.50; Emacs slowdown on special char, Robert Pluim, 2020/01/24
- bug#39133: 28.0.50; Emacs slowdown on special char, Eli Zaretskii, 2020/01/24
- bug#39133: 28.0.50; Emacs slowdown on special char, Robert Pluim, 2020/01/24
- bug#39133: 28.0.50; Emacs slowdown on special char, Robert Pluim, 2020/01/24
- bug#39133: 28.0.50; Emacs slowdown on special char, Eli Zaretskii, 2020/01/24