QtWayland and mesa might dead lock KWin if we start rendering a QWindow
before Qt/Mesa got the last frame callback. They perform blocking wayland
event reading on the main gui thread which makes it impossible for KWin
to do the compositing and send the callback.
To workaround this problem we fake a frameRendered directly after each
damage event for a Qt internal window. Unfortunately this is not yet
completely sufficient, thus we also need to ensure that the wayland
events are processed before any events are processed which would cause
a repaint and block. Thus we first flush QtWayland's wl_display and then
our Server connection. If there were any damage events we can be sure
that the frameRendered is sent before Qt attempts to render.
QtWayland only creates popup windows if they have a parent QWindow or
if there is any window which had input. It's not enough to fake an
enter, it needs to be either a pointer button press or key press.
As KWin's useraction menu doesn't have a parent and we most likely
never send a pointer press to any QWindow it doesn't get shown. To
circumvent this we create a dummy window and fake a button press/release
on the window. After that Qt is tricked into believing there's a parent
window and shows the popup.
Faking the input is only done with at least Qt 5.5 as QtWayland crashes
on pointer event without a keymap being installed. As KWin does not yet
send keymaps we better disable the dangerous code path. With Qt 5.5 the
crash condition is fixed.
The ShellClient is a Toplevel subclass for a
KWayland::Server::ShellSurfaceInterface. It gets created when a new
ShellSurfaceInterface is created and destoryed when it gets unmapped.
So far the usage is still rather limited. The ShellClient is opened
at position (0/0). While it's possible to pass pointer events to it,
it's not yet possible to activate it, so no keyboard focus.
Getting the cursor image from the cursor theme is unfortunately not
straight forward. We have three different libraries and all have
drawbacks:
* XCursor - we just kicked it out
* xcb-util/cursor - only provides xcb_cursor_t, so a dependency on X
* wayland-cursor - only a client side API
The picked solution is using wayland-cursor. It provides the cursor in a
wl_buffer. Unfortunately the client side API does not easily allow to
a) read it back
b) init without a wl_shm_pool
Thus we need to work this around:
* create an internal connection
* get a ShmPool on it
* init WaylandCursorTheme with this ShmPool
* get the cursor wl_buffer from the theme
* trigger a roundtrip
* get the corresponding BufferInterface for the buffer
* set the content as the software cursor
The AbstractBackend registers itself in the WaylandServer allowing
external users to easily get to the backend and not needing to test
manually which backend is used.
WaylandServer allows to create a ClientConnection which is intended for
QtWayland. This allows us to easily identify our "own" surfaces. The
created file descriptor is set as env variable WAYLAND_SOCKET prior to
creating the Application. Wayland will unset it after connecting, so we
don't need to unset it. This removes the hack of setting and resetting
the WAYLAND_DISPLAY environment variable.
Creates a socketpair in WaylandServer and creates a ClientConnection for
Xwayland. The created file descriptor is passed to Xwayland through the
WAYLAND_SOCKET env variable.
The WaylandServer is at the moment only used to support starting an
Xwayland. It does not support Wayland clients yet, so don't get
excited.
For Xwayland it's using the trick of creating the Display before the
QApplication is created with manual event dispatching.
