Fallback to Wayland if Xorg is not available

In environments where Anaconda handles the overall GUI environment
setup (eq. netinst/boot.iso) try to use Wayland compositor if
Xorg server is not found.

Also add support for a (temporary?) boot inst.wayland boot option,
that can be used to force Wayland compositor to be used. This makes it
possible to check if Waland can be used in the given environment even
if the given installation image still contains Xorg.

pyanaconda/display.py

@@ -28,6 +28,7 @@
 
 from pyanaconda.core.configuration.anaconda import conf
 from pyanaconda.core.process_watchers import WatchProcesses
+from pyanaconda.core.kernel import kernel_arguments
 from pyanaconda import startup_utils
 from pyanaconda.core import util, constants, hw
 from pyanaconda import vnc
@@ -245,6 +246,56 @@ def write_xdriver(driver, root=None):
     f.close()
 
 
+# Wayland
+
+def start_wayland_compositor():
+    """Start Wayland compositor for the Anaconda GUI.
+
+    Add XDG_DATA_DIRS to the environment to pull in our overridden schema
+    files.
+
+    FIXME: Will XDG_DATA_DIRS work with Wayland compositor ?
+    """
+    datadir = os.environ.get('ANACONDA_DATADIR', '/usr/share/anaconda')
+    if 'XDG_DATA_DIRS' in os.environ:
+        xdg_data_dirs = datadir + '/window-manager:' + os.environ['XDG_DATA_DIRS']
+    else:
+        xdg_data_dirs = datadir + '/window-manager:/usr/share'
+
+    def wayland_preexec():
+        # to set GUI subprocess SIGINT handler
+        # FIXME: does this even work with a Wayland compoitor ?
+        signal.signal(signal.SIGINT, signal.SIG_IGN)
+
+    childproc = util.startProgram(["gnome-kiosk", "--wayland-display", ":1", "--sm-disable",
+                                  "--wayland"], env_add={'XDG_DATA_DIRS': xdg_data_dirs},
+                                  preexec_fn=wayland_preexec)
+    WatchProcesses.watch_process(childproc, "gnome-kiosk")
+
+
+def set_wayland_resolution(runres):
+    """Set Wayland server screen resolution.
+
+    FIXME: implement this using Mutter DBus API
+    FIXME: keep runres or use horizontal/vertical resolution instead ?
+
+    :param str runres: a resolution specification string
+    """
+    log.error("FIXME: set screen resolution - not yet implemented on Wayland")
+
+
+def do_extra_wayland_actions(runres, gui_mode):
+    """Perform Wayland related actions not related to startup.
+
+    :param str runres: a resolution specification string
+    :param gui_mode: an Anaconda display mode
+    """
+    if runres and gui_mode and not flags.usevnc:
+        set_wayland_resolution(runres)
+
+    start_user_systemd()
+
+
 # general display startup
 def setup_display(anaconda, options):
     """Setup the display for the installation environment.
@@ -319,16 +370,35 @@ def setup_display(anaconda, options):
         for error_message in vnc_error_messages:
             stdout_log.warning(error_message)
 
-    # Should we try to start Xorg?
-    want_x = anaconda.gui_mode and not (flags.preexisting_x11 or flags.usevnc)
-
-    # Is Xorg is actually available?
-    if want_x and not os.access("/usr/bin/Xorg", os.X_OK):
-        stdout_log.warning(_("Graphical installation is not available. "
-                             "Starting text mode."))
-        time.sleep(2)
-        anaconda.display_mode = constants.DisplayModes.TUI
-        want_x = False
+    # Xorg or Wayland?
+    want_x = False
+    want_wayland = False
+
+    # try to run in local GUI mode
+    if anaconda.gui_mode and not (flags.preexisting_x11 or flags.usevnc):
+        # is Xorg actually available?
+        xorg_server_available = os.access("/usr/bin/Xorg", os.X_OK)
+
+        # is our Wayland compositor available ?
+        wayland_compositor_available = os.access("/usr/bin/gnome-kiosk", os.X_OK)
+
+        # do we have at least one of the needed deps we need to run in graphical mode ?
+        elif xorg_server_available:
+            # check for Wayland override
+            if "wayland" in kernel_arguments and wayland_compositor_available:
+                # this way we can test if insaller on Wayland works on a given system
+                want_wayland = True
+            else:
+                # no Wayland override or no Wayland, just use X
+                want_x = True
+        elif wayland_compositor_available:
+            want_wayland = True
+        else:
+            # neither X or Wayland is available
+            anaconda.display_mode = constants.DisplayModes.TUI
+            stdout_log.warning(_("Graphical installation is not available. "
+                                 "Starting text mode."))
+            time.sleep(2)
 
     if anaconda.tui_mode and flags.vncquestion:
         # we prefer vnc over text mode, so ask about that
@@ -346,7 +416,13 @@ def setup_display(anaconda, options):
 
     # check_memory may have changed the display mode
     want_x = want_x and (anaconda.gui_mode)
-    if want_x:
+    want_wayland = want_wayland and (anaconda.gui_mode)
+
+    if want_wayland:
+        log.debug("Using Wayland compositor to provide locally running graphical interface.")
+        start_wayland_compositor()
+    elif want_x:
+        log.debug("Using Xorg server to provide locally running graphical interface.")
         try:
             start_x11(xtimeout)
             do_startup_x11_actions()