fix: register ddm as a display manager via debconf

debian/control

@@ -19,9 +19,8 @@ Rules-Requires-Root: no
 
 Package: ddm
 Section: libdevel
-#Provides: x-display-manager
+Provides: x-display-manager
 Architecture: any
-Multi-Arch: same
 Depends: ${shlibs:Depends},
          ${misc:Depends},
          seatd,

debian/ddm.config

@@ -0,0 +1,68 @@
+#!/bin/sh
+# Debian ddm package configuration script
+# based on lightdm script (based on xdm script)
+# Copyright 2001 Branden Robinson.
+# Licensed under the GNU General Public License, version 2.
+
+set -e
+
+# source debconf library
+. /usr/share/debconf/confmodule
+
+# set default display manager
+DEFAULT_DISPLAY_MANAGER_FILE=/etc/X11/default-display-manager
+
+THIS_PACKAGE=ddm
+
+OWNERS=
+if db_metaget shared/default-x-display-manager owners; then
+  OWNERS="$RET"
+fi
+
+CHOICES=
+if db_metaget shared/default-x-display-manager choices; then
+  CHOICES="$RET"
+fi
+
+if [ "$OWNERS" != "$CHOICES" ]; then
+  # Strip architecture qualifiers (e.g. "ddm:amd64" -> "ddm") so that the
+  # displayed choices and the value stored in default-display-manager file
+  # (plain package name) stay in sync.
+  OWNERS_CLEAN=$(echo "$OWNERS" | sed 's/:[[:alnum:]_-]*//g')
+  db_subst shared/default-x-display-manager choices "$OWNERS_CLEAN" || :
+  db_fset shared/default-x-display-manager seen false || :
+fi
+
+# debconf is not a registry; use the current contents of the default display
+# manager file to pre-answer the question if possible
+if [ -e "$DEFAULT_DISPLAY_MANAGER_FILE" ]; then
+  CURRENT_DEFAULT=$(grep -v '^[[:space:]]*#' "$DEFAULT_DISPLAY_MANAGER_FILE" | head -n 1)
+  if [ -n "$CURRENT_DEFAULT" ]; then
+    CURRENT_DEFAULT=$(basename "$CURRENT_DEFAULT")
+    db_set shared/default-x-display-manager "$CURRENT_DEFAULT"
+  fi
+else
+  CURRENT_DEFAULT=
+  if db_get shared/default-x-display-manager; then
+    CURRENT_DEFAULT="$RET"
+  fi
+fi
+
+db_input high shared/default-x-display-manager || :
+db_go || :
+
+# using this display manager?
+NEW_DEFAULT=
+if db_get shared/default-x-display-manager; then
+  NEW_DEFAULT="$RET"
+fi
+
+# move the default display manager file if we are going to change it
+if [ -n "$NEW_DEFAULT" ]; then
+  if [ "$NEW_DEFAULT" != "$CURRENT_DEFAULT" ]; then
+    if [ -e "$DEFAULT_DISPLAY_MANAGER_FILE" ]; then
+      mv "$DEFAULT_DISPLAY_MANAGER_FILE" \
+         "${DEFAULT_DISPLAY_MANAGER_FILE}.dpkg-tmp"
+    fi
+  fi
+fi

debian/ddm.postrm

@@ -33,6 +33,22 @@ case "$1" in
             rm "$DEFAULT_SERVICE"
         fi
 
+        ;;
+    remove)
+        # Update the display-manager.service symlink to point to the newly
+        # chosen display manager (written by prerm into DEFAULT_DISPLAY_MANAGER_FILE)
+        if [ -e "$DEFAULT_DISPLAY_MANAGER_FILE" ] && [ -d /etc/systemd/system/ ]; then
+            DM=$(basename "$(cat "$DEFAULT_DISPLAY_MANAGER_FILE")")
+            SERVICE=/lib/systemd/system/$DM.service
+            if [ -h "$DEFAULT_SERVICE" ] && [ "$(readlink "$DEFAULT_SERVICE")" = /dev/null ]; then
+                echo "Display manager service is masked" >&2
+            elif [ -e "$SERVICE" ]; then
+                ln -sf "$SERVICE" "$DEFAULT_SERVICE"
+            fi
+        elif [ -h "$DEFAULT_SERVICE" ] && [ ! -e "$DEFAULT_SERVICE" ]; then
+            # Dangling symlink, no other display-manager installed
+            rm -f "$DEFAULT_SERVICE"
+        fi
         ;;
     abort-install|abort-upgrade)
         # roll back displacement of default display manager file

debian/ddm.prerm

@@ -20,12 +20,16 @@ if [ "$1" = "remove" ] || [ "$1" = "deconfigure" ]; then
     # does the question still exist?
     if db_get shared/default-x-display-manager; then
       db_metaget shared/default-x-display-manager owners
-      db_subst shared/default-x-display-manager choices "$RET"
+      # Strip architecture qualifiers (e.g. "lightdm:amd64" -> "lightdm")
+      OWNERS_CLEAN=$(echo "$RET" | sed 's/:[[:alnum:]_-]*//g')
+      db_subst shared/default-x-display-manager choices "$OWNERS_CLEAN"
       db_get shared/default-x-display-manager
+      # Strip architecture qualifier from current value too
+      CURRENT_DM=$(echo "$RET" | sed 's/:[[:alnum:]_-]*//')
       # are we removing the currently selected display manager?
-      if [ "$THIS_PACKAGE" = "$RET" ]; then
+      if [ "$THIS_PACKAGE" = "$CURRENT_DM" ]; then
         if [ -e "$DEFAULT_DISPLAY_MANAGER_FILE" ]; then
-	  db_get "$RET"/daemon_name
+	  db_get "$THIS_PACKAGE"/daemon_name
 	  if [ "$(cat $DEFAULT_DISPLAY_MANAGER_FILE)" = "$RET" ]; then
 	    rm "$DEFAULT_DISPLAY_MANAGER_FILE"
 	  fi
@@ -38,9 +42,14 @@ if [ "$1" = "remove" ] || [ "$1" = "deconfigure" ]; then
         # to the new default display manager
         if [ ! -e $DEFAULT_DISPLAY_MANAGER_FILE ]; then
           db_get shared/default-x-display-manager
-          echo "Please be sure to run \"dpkg-reconfigure $RET\"."
-          db_get "$RET"/daemon_name
-          echo "$RET" > "$DEFAULT_DISPLAY_MANAGER_FILE"
+          # Strip any architecture qualifier from user's selection
+          NEW_DM=$(echo "$RET" | sed 's/:[[:alnum:]_-]*//')
+          echo "Please be sure to run \"dpkg-reconfigure $NEW_DM\"."
+          if db_get "$NEW_DM"/daemon_name && [ -n "$RET" ]; then
+            echo "$RET" > "$DEFAULT_DISPLAY_MANAGER_FILE"
+          else
+            echo "/usr/bin/$NEW_DM" > "$DEFAULT_DISPLAY_MANAGER_FILE"
+          fi
         fi
       fi
     fi

debian/ddm.templates

@@ -0,0 +1,20 @@
+Template: ddm/daemon_name
+Type: string
+Default: /usr/bin/ddm
+Description: for internal use only
+
+Template: shared/default-x-display-manager
+Type: select
+Choices: ${choices}
+Description: Default display manager:
+ A display manager is a program that provides graphical login capabilities for
+ the X Window System and Wayland compositors.
+ .
+ Only one display manager can manage a given X server, but multiple display
+ manager packages are installed. Please select which display manager should
+ run by default.
+ .
+ Multiple display managers can run simultaneously if they are configured to
+ manage different servers; to achieve this, configure the display managers
+ accordingly, edit each of their init scripts in /etc/init.d, and disable the
+ check for a default display manager.