This commit converts the output of ds->getProp(LG_DS_WARP_SUPPORT) to
an enum containing three items:
* LG_DS_WARP_NONE: warp is not supported at all
* LG_DS_WARP_SURFACE: warp is possible, but only inside the window
* LG_DS_WARP_SCREEN: warp is possible anywhere on the screen
LG_DS_WARP_NONE corresponds to the old false return value, and
LG_DS_WARP_SCREEN corresponds to the old true return value.
LG_DS_WARP_SURFACE is designed for Wayland, where warping is possible,
but only in our window. In this case, since we cannot warp outside
the window, we can warp the cursor to the edge when we attempt to exit.
If the cursor leaves, the normal leave routine gets called, and the
cursor disappears. If the cursor does not end up leaving, we grab it
again.
Using a macro ENABLE_OPENGL just like ENABLE_EGL to optionally remove
OpenGL implementation code. This is mostly because on Wayland it's just
a rehash of the EGL code (as EGL is the only way to create OpenGL
contexts on Wayland).
As the window manager may change our mode to full screen without our
request we must ask the ds backend for the current state when we want to
toggle the mode.
zwp_relative_pointer_manager_v1 and zwp_pointer_constraints_v1 are
supported by GNOME/KDE/sway (and most other compositors), but they are
not a required part of the protocol.
Some users also run software in one-off nested compositors like cage[0]
for an extra layer of isolation; cage, at least, does not support
pointer captures.
This commit makes Looking Glass warn when an optional protocol is
unsupported, and fail if a required one is missing. Pointer grab paths
have a new guard against the aforementioned protocols being missing.
[0]: https://github.com/Hjdskes/cage
Platforms such as Wayland have no abillity to warp the cursor, as such
can not operate in an always relative mode. This property allows
platforms to report the lack of warp support and prevent LG from
grabbing the pointer.
Some platforms such as Wayland need to set environment vairables before
SDL is initialized, as such this change detects the display server
before SDL has started and calls the new `earlyInit` method providing
the implementation an opportunity to set things up.
