According to the hwcomposer documentation:
"It is a (silent) error to have HWC_EVENT_VSYNC enabled when calling
hwc_composer_device.set(..., 0, 0, 0) (screen off)".
Because of that we may not enable vsync directly after toggling the
output, but need to wait till after calling the set call.
Reviewed-by: Bhushan Shah
Apparently we don't get a vsync event for the first frame during startup
which blocks the compositor till the end of days. Thus a timer is added
which calls vsync after 1 sec if we didn't get an event.
Note: qt5-qpa-hwcomposer-plugin does the vsync in a different way:
it uses a wait condition to truly block in present till the vsync.
Maybe we need to do that as well.
Based on a previous patch done by David Edmundson and heavily
inspired by qt5-qpa-hwcomposer-plugin [1].
The change requires a newer libhybris than the one used by Ubuntu. In
fact it allows to build against current master (at the day of writing [2]).
REVIEW: 125606
[1] https://github.com/mer-hybris/qt5-qpa-hwcomposer-plugin
[2] bd6df6a306
Libinput does work on libhybris enabled devices. There is no need to
use Android's input stack. This simplifies our code a lot and increases
sharing with normal Linux systems.
What's tricky is to convince the system to use libinput through with our
logind helper. Logind fails to open the files for us if we start KWin
over either ssh or adb shell. We need to get it into a proper session, so
only a kwin started through a helper like simplelogin will be able to use
libinput.
REVIEW: 125608
Unfortunately on libhybris enabled systems libinput doesn't work, thus
the backend needs to handle input events which can be read from hybris.
So far the backend only handles touch events properly, though some
aspects look wrong. E.g. motion gives only for one touch contact point.
Unfortunately the documentation is quite weak, so there might be
something important missing.
This backend interacts with libhybris to create a hwcomposer which is
used for creating the egl context and surface. The initial version of
this backend is based on test_hwcomposer.cpp provided by libhybris.
Please note that using the hwcomposer backend requires a newer libepoxy,
the latest stable release is not able to bring up OpenGLES, so one needs
a master build of libepoxy.
Notes on licensing:
libhybris is Apache 2.0 licensed, which is not compatile with GPLv2.
But it is compatible with GPLv3. Thus the source files in the hwcomposer
backend are licensed GPLv3+ and not GPLv2+ as the rest of KWin. If one
uses KWin without the hwcomposer backend (which is obviously the default)
the licence doesn't change. But if the hwcomposer backend is used the
overall license of KWin changes to GPLv3+.
