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In case 'scan_evdev' and 'scan_drm' are both false, we never set 'r' to
anyhting, thus return an uninitialized error code. Fix this by always
returning 0 as we catch negative codes earlier, anyway. Thanks to Thomas
H.P. Anderson for the report.
Like systemd-subterm, this new systemd-evcat tool should only be used to
debug libsystemd-terminal. systemd-evcat attaches to the running session
and pushes all evdev devices attached to the current session into an
idev-session. All events of the created idev-devices are then printed to
stdout for input-event debugging.
The idev-keyboard object provides keyboard devices to the idev interface.
It uses libxkbcommon to provide proper keymap support.
So far, the keyboard implementation is pretty straightforward with one
keyboard device per matching evdev element. We feed everything into the
system keymap and provide proper high-level keyboard events to the
application. Compose-features and IM need to be added later.
The evdev-element provides linux evdev interfaces as idev-elements. This
way, all real input hardware devices on linux can be used with the idev
interface.
We use libevdev to interface with the kernel. It's a simple wrapper
library around the kernel evdev API that takes care to resync devices
after kernel-queue overflows, which is a rather non-trivial task.
Furthermore, it's a well tested interface used by all other major input
users (Xorg, weston, libinput, ...).
Last but not least, it provides nice keycode to keyname lookup tables (and
vice versa), which is really nice for debugging input problems.
The idev-interface provides input drivers for all libsystemd-terminal
based applications. It is split into 4 main objects:
idev_context: The context object tracks global state of the input
interface. This will include data like system-keymaps,
xkb contexts and more.
idev_session: A session serves as controller for a set of devices.
Each session on an idev-context is independent of each
other. The session is also the main notification object.
All events raised via idev are reported through the
session interface. Apart of that, the session is a
pretty dumb object that just contains devices.
idev_element: Elements provide real hardware in the idev stack. For
each hardware device, one element is added. Elements
have no knowledge of higher-level device types, they
only provide raw input data to the upper levels. For
example, each evdev device is represented by a different
element in an idev session.
idev_device: Devices are objects that the application deals with. An
application is usually not interested in elements (and
those are hidden to applications), instead, they want
high-level input devices like keyboard, touchpads, mice
and more. Device are the high-level interface provided
by idev. Each device might be fed by a set of elements.
Elements drive the device. If elements are removed,
devices are destroyed. If elements are added, suitable
devices are created.
Applications should monitor the system for sessions and hardware devices.
For each session they want to operate on, they create an idev_session
object and add hardware to that object. The idev interface requires the
application to monitor the system (preferably via sysview_*, but not
required) for hardware devices. Whenever hardware is added to the idev
session, new devices *might* be created. The relationship between hardware
and high-level idev-devices is hidden in the idev-session and not exposed.
Internally, the idev elements and devices are virtual objects. Each real
hardware and device type inherits those virtual objects and provides real
elements and devices. Those types will be added in follow-up commits.
Data flow from hardware to the application is done via idev_*_feed()
functions. Data flow from applications to hardware is done via
idev_*_feedback() functions. Feedback is usually used for LEDs, FF and
similar operations.
We're going to need multiple binaries that provide session-services via
logind device management. To avoid re-writing the seat/session/device
scan/monitor interface for each of them, this commit adds a generic helper
to libsystemd-terminal:
The sysview interface scans and tracks seats, sessions and devices on a
system. It basically mirrors the state of logind on the application side.
Now, each session-service can listen for matching sessions and
attach to them. On each session, managed device access is provided. This
way, it is pretty simple to write session-services that attach to multiple
sessions (even split across seats).
Empty format-strings are just fine if format-functions do more than
printing. This is the case here, so suppress the "empty format-string"
warning by using "%s" with an empty argument.
The unifont layer of libsystemd-terminal provides a fallback font for
situations where no system-fonts are available, or if you don't want to
deal with traditional font-formats for some reasons.
The unifont API mmaps a pre-compiled bitmap font that was generated out of
GNU-Unifont font-data. This guarantees, that all users of the font will
share the pages in memory. Furthermore, the layout of the binary file
allows accessing glyph data in O(1) without pre-rendering glyphs etc. That
is, the OS can skip loading pages for glyphs that we never access.
Note that this is currently a test-run and we want to include the binary
file in the GNU-Unifont package. However, until it was considered stable
and accepted by the maintainers, we will ship it as part of systemd. So
far it's only enabled with the experimental --enable-terminal, anyway.
The systemd-subterm example is a stacked terminal that shows how to
use sd-term. Instead of rendering images and displaying it via X11/etc.,
it uses its parent terminal to display the page (terminal-emulator inside
a terminal-emulator) (like GNU-screen and friends do).
This is only for testing and not installed system-wide!
The screen-layer represents the terminal-side (compared to the host-side).
It connects term_parser with term_page and implements all the required
control sequences.
We do not implement all available control sequences. Even though our
parser recognizes them, there is no need to handle them. Most of them are
legacy or unused. We try to be as compatible to xterm, so if we missed
something, we can implement it later. However, all the VT510 / VT440 stuff
can safely be skipped (who needs terminal macros? WTF?).
The keyboard-handling is still missing. It will be added once
systemd-console is available and we pulled in the key-definitions.
The term-parser is used to parse any input from TTY-clients. It reads CSI,
DCS, OSC and ST control sequences and normal escape sequences. It doesn't
do anything with the parsed data besides detecting the sequence and
returning it. The caller has to react to them.
The parser also comes with its own UTF-8 helpers. The reason for that is
that we don't want to assert() or hard-fail on parsing errors. Instead,
we treat any invalid UTF-8 sequences as ISO-8859-1. This allows pasting
invalid data into a terminal (which cannot be controlled through the TTY,
anyway) and we still deal with it in a proper manner.
This is _required_ for 8-bit and 7-bit DEC modes (including the g0-g3
mappings), so it's not just an ugly fallback because we can (it's still
horribly ugly but at least we have an excuse).
The page-layer is a one-dimensional array of lines. Combined with the
one-dimensional lines, you get a two-dimensional page. However, both
implementations, lines and pages only deal with their own dimension. That
means, lines don't know anything about other lines, and pages don't know
anything about cells.
Apart from pages, this also introduces history objects. A history object
is a scroll-back buffer. As some pages like alt-buffers don't have
histories, we keep them separate.
Pages itself forward all cell-related operations to the related line. Only
line-related operations are directly handled by the page. This is mostly
scrolling and history. To support proper resizing, we also keep a
fill-state just like lines do for cells.
There're 3 supported color-modes: term-color-codes, 256-color-code and
rgb-color. We now use the term-color as default so zero(attr) will do what
you'd expect. Furthermore, we split rgb and 256color so users can forward
them properly without requiring an internal RGB converter.
Furthermore, a "hidden" field according to VT510rm manual is added.
This commit introduces libsystemd-ui, a systemd-internal helper library
that will contain all the UI related functionality. It is going to be used
by systemd-welcomed, systemd-consoled, systemd-greeter and systemd-er.
Further use-cases may follow.
For now, this commit only adds terminal-page handling based on lines only.
Follow-up commits will add more functionality.
