The Infinality bytecode interpreter is removed in favor of the new v40 TrueType
interpreter. In the past, the Infinality interpreter provided support for
ClearType-style hinting instructions while the default interpreter (then v35)
provided support only for original TrueType-style instructions. The v40
interpreter corrects this deficiency, so the Infinality interpreter is no longer
necessary.
To understand why the Infinality interpreter is no longer necessary, we should
understand how ClearType differs from TrueType and how the v40 interpreter
works. The following is a summary of information available on the FreeType
website [1] mixed with my own editorializing.
TrueType instructions use horizontal and vertical hints to improve glyph
rendering. Before TrueType, fonts were only vertically hinted; horizontal hints
improved rendering by snapping stems to pixel boundaries. Horizontal hinting is
a risk because it can significantly distort glyph shapes and kerning. Extensive
testing at different resolutions is needed to perfect the TrueType
hints. Microsoft invested significant effort to do this with its "Core fonts for
the Web" project, but few other typefaces have seen this level of attention.
With the advent of subpixel rendering, the effective horizontal resolution of
most displays increased significantly. ClearType eschews horizontal hinting in
favor of horizontal supersampling. Most fonts are designed for the Microsoft
bytecode interpreter, which implements a compatibility mode with
TrueType-style (horizontal and vertical) instructions. However, applying the
full horizontal hints to subpixel-rendered fonts leads to color fringes and
inconsistent stem widths. The Infinality interpreter implements several
techniques to mitigate these problems, going so far as to embed font- and
glyph-specific hacks in the interpreter. On the other hand, the v40 interpreter
ignores the horizontal hinting instructions so that glyphs render as they are
intended to on the Microsoft interpreter. Without the horizontal hints, the
problems of glyph and kerning distortion, color fringes, and inconsistent stem
widths--the problems the Infinality interpreter was created to solve--simply
don't occur in the first place.
There are also security concerns which motivate removing the Infinality patches.
Although there is an updated version of the Infinality interpreter for FreeType
2.7, the lack of a consistent upstream maintainer is a security concern. The
interpreter is a Turing-complete virtual machine which has had security
vulnerabilities in the past. While the default interpreter is used in billions
of devices and is maintained by an active developer, the Infinality interpreter
is neither scrutinized nor maintained. We will probably never know if there are
defects in the Infinality interpreter, and if they were discovered they would
likely never be fixed. I do not think that is an acceptable situtation for a
core library like FreeType.
Dropping the Infinality patches means that font rendering will be less
customizable. I think this is an acceptable trade-off. The Infinality
interpreter made many compromises to mitigate the problems with horizontal
hinting; the main purpose of customization is to tailor these compromises to the
user's preferences. The new interpreter does not have to make these compromises
because it renders fonts as their designers intended, so this level of
customization is not necessary.
The Infinality-associated patches are also removed from cairo. These patches
only set the default rendering options in case they aren't set though
Fontconfig. On NixOS, the rendering options are always set in Fontconfig, so
these patches never actually did anything for us!
The Fontconfig test suite is patched to account for a quirk in the way PCF fonts
are named.
The fontconfig option `hintstyle` is no longer configurable in NixOS. This
option selects the TrueType interpreter; the v40 interpreter is `hintslight` and
the older v35 interpreter is `hintmedium` or `hintfull` (which have actually
always been the same thing). The setting may still be changed through the
`localConf` option or by creating a user Fontconfig file.
Users with HiDPI displays should probably disable hinting and antialiasing: at
best they have no visible effect.
The fontconfig-ultimate settings are still available in NixOS, but they are no
longer the default. They still work, but their main purpose is to set rendering
quirks which are no longer necessary and may actually be
detrimental (e.g. setting `hintfull` for some fonts). Also, the vast array of
font substitutions provided is not an appropriate default; the default setting
should be to give the user the font they asked for.
[1]. https://www.freetype.org/freetype2/docs/subpixel-hinting.html
This reverts commit 29caa185a7.
Not clear what the proper thing to do is. cf94cdb59b renders this
question mostly moot. Reverting before 17.03 branch to avoid a repeat
of #19054.
This provides a default console_cmd for the slim display-manager.
When the user enters "console" as the user name, slim will run this
command.
Having a default is rather important; the virtual terminals don't work
with some display drivers, so having a broken X session can leave you
locked out of your machine.
- As noted on github, GDM needs different parameters for X.
- Making xserverArgs a true list instead of concat-string helps to
filter it and it feels more correct anyway.
- Tested: gdm+gnome, lightdm+gnome. There seems to be no logout option
in gnome, and gdm doesn't offer other sessions, but maybe these are normal.
Fixes#20713, though I'm certain nixpkgs contains loads of places
without proper quoting, as (ba)sh unfortunately encourages that.
The only plus side is that most of such problems in nixpkgs aren't
actually security problems but mere annoyance to those who are foolish
enough to use "weird" characters in critical names.
It was lacking the dbus configuration to bind to
org.freedesktop.DisplayManager, and it was passing fixed TTY/display
numbers to the X server (see 9be012f0d4).
The following changes are included:
1) install user unit files from upstream dbus
2) use absolute paths to config for --system and --session instances
3) make socket activation of user units configurable
There has been a number of PRs to address this, so this one does the
bare minimum, which is to make the functionality available and
configurable but defaults to off.
Related PRs:
- #18382
- #18222
(cherry picked from commit f7215c9b5b)
Signed-off-by: Domen Kožar <domen@dev.si>
KDM and LightDM (at least with autologin) call the xsession-script with
two arguments: the first is the path of the xsession script itself,
while the second one are the actual arguments. The line to re-exec the
script under systemd-cat only forwarded a single argument, therefore
breaking LightDM and KDM login. This commit fixes the issue by always
forwarding all the arguments.
When displaying a warning about a removed Option we should always
include reasoning why it was removed and how to get the same
functionality without it.
Introduces such a description argument and patches occurences (mostly
with an empty string).
startGnuPGAgent: further notes on replacement
... rather than ~/.xsession-errors. It might make sense to make this
the default, in order to eliminate ad hoc, uncentralised, poorly
discoverable log files.
This ensures that "journalctl -u display-manager" does what you would
expect in 2016. However, the main reason is to ensure that our VM
tests show the output of the X server.
A slight problem is that with KDE user switching, messages from the
various X servers end up in the same place. However, that's an
improvement over the previous situation, where the second X server
would overwrite the /var/log/X.0.log of the first. (This was caused by
the fact that we were passing a hard-coded value for -logfile.)
`dbus-launch` is executed early in the script, before desktop managers
had a chance to setup the environment. If DBus activation is used,
applications launched by this may therefore lack necessary environment
variables. This patch sends the complete environment to DBus after
launching the desktop manager.
GnuPG 2.1.x changed the way the gpg-agent works, and that new approach no
longer requires (or even supports) the "start everything as a child of the
agent" scheme we've implemented in NixOS for older versions.
To configure the gpg-agent for your X session, add the following code to
~/.xsession or some other appropriate place that's sourced at start-up:
gpg-connect-agent /bye
GPG_TTY=$(tty)
export GPG_TTY
If you want to use gpg-agent for SSH, too, also add the settings
unset SSH_AGENT_PID
export SSH_AUTH_SOCK="${HOME}/.gnupg/S.gpg-agent.ssh"
and make sure that
enable-ssh-support
is included in your ~/.gnupg/gpg-agent.conf.
The gpg-agent(1) man page has more details about this subject, i.e. in the
"EXAMPLES" section.
