improve wayland support

scripts/yast2

@@ -254,7 +254,7 @@ while true ; do
 		--kcontrol)   Y2UI_ARGS="$Y2UI_ARGS --kcontrol_id YaST" ; shift ;;
 		--qt)  export CMDLINE_UI="qt"  ; shift ;;
 		--gtk)  export CMDLINE_UI="gtk"  ; shift ;;
-		--ncurses)  unset DISPLAY ; shift ;;
+		--ncurses)  unset DISPLAY ;  unset WAYLAND_DISPLAY ; shift ;;
 		--) shift ; break ;;
 		*) echo "Unrecognized option $1" ; exit 1 ;;
 
@@ -304,6 +304,7 @@ case "`basename $0`" in
 	YaST|yast|yast1|zast)
 		if [ -z "$CMDLINE_UI" ]; then
 			unset DISPLAY;
+                        unset WAYLAND_DISPLAY;
 		fi
 	;;
 esac
@@ -335,9 +336,13 @@ fi
 
 # Fallback GUI
 SELECTED_GUI=ncurses
-# if we have a DISPLAY, select a preferred GUI
-if [ -n "$DISPLAY" ]; then
+# if we have a DISPLAY or WAYLAND_DISPLAY, select a preferred GUI
+if [ -n "$DISPLAY" -o -n "$WAYLAND_DISPLAY" ]; then
     select_gui_frontend
+    # for wayland only environment, switch qt to use it
+    if [ -n "$WAYLAND_DISPLAY" -a -z "$DISPLAY" ]; then
+      export QT_QPA_PLATFORM=wayland
+    fi
 fi
 
 if [ -n "$TESTING_YAST2" ]; then