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bug#21028: Slow font rendering in emacs
From: |
Ralf Jung |
Subject: |
bug#21028: Slow font rendering in emacs |
Date: |
Tue, 14 Mar 2017 16:57:33 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 |
Hi,
>> I know very little about emacs, so I wouldn't know how to make any
>> measurements.
>
> If some reaction time is slow, just estimating how many seconds it
> takes might be good enough, if you describe the slow command and what
> is on the screen when it is slow.
Okay, so what I do as actually quite simple: I open the aforementioned
file in emacs, and then I use the scroll wheel on my mouse to scroll
around quickly (move wheel up fast - move wheel down fast - repeat).
When I do this with the "good" setup, text keeps flying over my screen
and everything reacts instantaneously. When I do this with the "bad"
setup, nothing moves until I stop turning the scroll wheel and wait a
little more, where the waiting time is roughly half the time I spent
scrolling quickly.
>>> Also, what is your value of system-configuration-options and
>>> system-configuration-features? And which version of Emacs is that?
>>
>> Sorry, I have no idea how to read those variables
>
> Type
>
> M-: system-configuration-options RET
>
> and tell what Emacs displays. the same with the other one.
The -options variable says
"--build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
--libexecdir=/usr/lib --localstatedir=/var/lib --infodir=/usr/share/info
--mandir=/usr/share/man --with-pop=yes
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
--build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
--libexecdir=/usr/lib --localstatedir=/var/lib --infodir=/usr/share/info
--mandir=/usr/share/man --with-pop=yes
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
--with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g
-O2 -fdebug-prefix-map=/build/emacs24-OFSh0x/emacs24-24.5+1=.
-fstack-protector-strong -Wformat -Werror=format-security -Wall
-fno-PIE' 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2'
'LDFLAGS=-Wl,-z,relro -no-pie'"
And the -features one says
Symbol's value as variable is void: system-configuration-features
>> Emacs is fine in terms of speed, but it uses the wrong font for
>> characters not supported by Fira Sans Mono.
>> For example, for ∃ it picks "STIX"
>
> The default fontset was improved in Emacs 25.1, so there you should
> have Symbola for this character automatically.
But I don't want Symbola for this character. Symbola is not monospace,
so it's not going to look right in a document that otherwise uses
monospace characters.
> I'm hesitant because no one understands why that patch should have any
> profound effect on performance. We arrived at the patch by
> selectively reverting a particular commit that was fond by bisection.
> But that commit fixed an unrelated bug, so it wasn't done by mistake.
I see; thanks.
Kind regards,
Ralf
bug#21028: Slow font rendering in emacs, Eli Zaretskii, 2017/03/14