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Display performance degradation
From: |
YAMAMOTO Mitsuharu |
Subject: |
Display performance degradation |
Date: |
Thu, 17 Dec 2009 11:49:01 +0900 |
User-agent: |
Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8 (Shijō) APEL/10.6 Emacs/22.3 (sparc-sun-solaris2.8) MULE/5.0 (SAKAKI) |
I can observe significant display performance degradation on Emacs
23.1.90 compared with 23.1, especially when scrolling TUTORIAL.ja on a
frame that uses the xft font backend. I also observe the increase of
the total number of xftfont_draw calls, and a string in a single font
and color, which was originally displayed by one call, is now
unnecessarily divided into smaller units.
As an experiment, I tried restoring the following change, and then the
performance became comparable to 23.1.
2009-11-17 Jan Djärv <address@hidden>
* font.c (font_open_entity): Do not use cache, it does not pick up new
fontconfig settings like hinting.
*** 2975,2985 ****
--- 2987,3001 ----
else if (CONSP (Vface_font_rescale_alist))
scaled_pixel_size = pixel_size * font_rescale_ratio (entity);
+ #if 0
+ /* This doesn't work if you have changed hinting or any other parameter.
+ We need to make a new object in every case to be sure. */
for (objlist = AREF (entity, FONT_OBJLIST_INDEX); CONSP (objlist);
objlist = XCDR (objlist))
if (! NILP (AREF (XCAR (objlist), FONT_TYPE_INDEX))
&& XFONT_OBJECT (XCAR (objlist))->pixel_size == pixel_size)
return XCAR (objlist);
+ #endif
val = AREF (entity, FONT_TYPE_INDEX);
for (driver_list = f->font_driver_list;
The added comment implies that the simple removal of #if 0 causes
another problem for some cases, but I think creating a new font object
for each call is too much for the usual cases. Perhaps this part
needs some improvement.
YAMAMOTO Mitsuharu
address@hidden