Basically, this creates a separate thread for the mouse events, and this
thread detects that the desktop has changed (say to the secure desktop),
and unhooks, switches to the new desktop, and then rehooks.
This allows the cursor location to be updated while using NvFBC on secure
desktop and the login screen.
Unless the corresponding mouse down event was on our surface, we should
not be receiving the mouse up.
This is always the case on Wayland. On some other platforms,
SDL_CaptureMouse can be used to obtain input that happens outside the
Looking Glass surface, but Looking Glass does not make use of that
function.
We may want to process a mouse up if the corresponding mouse down
initiated a drag (e.g., of a window) that was released slightly outside
of the Looking Glass surface. Previously, Looking Glass would ignore the
mouse up, and the guest would be confused into thinking the button had
never been released, not ending the drag.
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
WTSGetActiveConsoleSessionId will return a session even if it's not logged in,
unlike our old GetInteractiveSessionID function. Launching looking glass on
such a console session will allow the login screen to be captured.
Note that WTSGetActiveConsoleSessionId() will return 0xFFFFFFFF if there are
no sessions attached.
We are actually getting mouse events directly from Wayland instead of going
through SDL, so we call app_updateCursorPos in pointer motion handlers and
swallow the SDL event.
Also removed parameters for app_handleMouseBasic as it relies exclusively on
absolute positions provided by app_updateCursorPos. Wayland does not give
you relative movements at all unless grabbed and passing absolute movements
is semantically incorrect.
Note that when the cursor is grabbed, movements are handled entirely through
relativePointerMotionHandler in wayland.c and does not go through
app_handleMouseBasic at all.
If the guest cursor state & position is unknown we can not rely on the
information to detect edge crossings. As such only allow cursor input if
LG is operating in capture mode.
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.
When capture mode is set if the cursor is not already in the view area
we need to force it to the state it would be if it were in view as
capture mode overrides all.
The pointer may not yet be in the view area so we should defer drawing
it until the mouse move handler determines that it's inside the view
area and turn it on itself.
As LG always operates in relitive mode, the actual pointer grab/ungrab
is managed by the move handler, as such setGrabQuiet should not alter
the grab/ungrab state of the local pointer.
To quote MSDN documentation:
> The lpApplicationName parameter can be NULL, in which case the executable
> name must be the first white space–delimited string in lpCommandLine. If
> the executable or path name has a space in it, there is a risk that a
> different executable could be run because of the way the function parses
> spaces. The following example is dangerous because the function will
> attempt to run "Program.exe", if it exists, instead of "MyApp.exe".
>
> LPTSTR szCmdline[] = _tcsdup(TEXT("C:\\Program Files\\MyApp"));
> CreateProcessAsUser(hToken, NULL, szCmdline, /*...*/ );
>
> If a malicious user were to create an application called "Program.exe" on
> a system, any program that incorrectly calls CreateProcessAsUser using the
> Program Files directory will run this application instead of the intended
> application.
>
> To avoid this problem, do not pass NULL for lpApplicationName.
So instead, we pass the executable to lpApplicationName instead, which avoids
the issue. MSDN says:
> The lpCommandLine parameter can be NULL. In that case, the function uses
> the string pointed to by lpApplicationName as the command line.
This also avoids the strdup since lpApplicationName is LPCSTR unlike
lpCommandLine which is LPSTR.
It shouldn't have any effect, since the host application is created with
the token, and there is no need for the service itself to impersonate.
In practice, removal doesn't appear to have any effect on the ability to
capture privileged things like secure desktop.
