Add -display none option. Close #110

Using the -display none option will start the VM with SPICE enabled but no display attached. The .ports file in the VM directory can be used to lookup the SSH and SPICE ports used by the VM.

quickemu

@@ -197,6 +197,7 @@ function vm_boot() {
   local CPU=""
   local DISK_USED=""
   local DISPLAY_DEVICE=""
+  local DISPLAY_RENDER=""
   local EFI_CODE=""
   local EFI_VARS=""
   local GUEST_CPU_CORES=""
@@ -630,7 +631,7 @@ function vm_boot() {
   # https://www.kraxel.org/blog/2019/09/display-devices-in-qemu/
   if [ "${guest_os}" == "linux" ]; then
     case ${OUTPUT} in
-      spice) DISPLAY_DEVICE="qxl-vga";;
+      none|spice) DISPLAY_DEVICE="qxl-vga";;
       *) DISPLAY_DEVICE="virtio-vga";;
     esac
   elif [ "${guest_os}" == "macos" ]; then
@@ -651,10 +652,6 @@ function vm_boot() {
 
   echo -n " - Display:  ${OUTPUT^^}, ${DISPLAY_DEVICE}"
 
-  if [ "${OUTPUT}" == "spice" ]; then
-    OUTPUT="none"
-  fi
-
   # Build the video configuration
   VIDEO="-device ${DISPLAY_DEVICE}"
 
@@ -669,17 +666,20 @@ function vm_boot() {
   fi
   VIDEO="${VIDEO} ${FULLSCREEN}"
 
-  if [ "${OUTPUT}" == "gtk" ]; then
-    OUTPUT="${OUTPUT},grab-on-hover=on,zoom-to-fit=off"
-    # GL is not working with GTK and virtio-vga
-    if [ "${DISPLAY_DEVICE}" == "virtio-vga" ]; then
-      GL="off"
-    fi
-  fi
-
-  if [ "${OUTPUT}" != "none" ]; then
-    OUTPUT="${OUTPUT},gl=${GL}"
-  fi
+  # Map Quickemu OUTPUT to QEMU -display
+  case ${OUTPUT} in
+    gtk)
+      DISPLAY_RENDER="${OUTPUT},grab-on-hover=on,zoom-to-fit=off"
+      # GL is not working with GTK and virtio-vga
+      if [ "${DISPLAY_DEVICE}" == "virtio-vga" ]; then
+        GL="off"
+      fi
+      ;;
+    none|spice)
+      DISPLAY_RENDER="none";;
+    *)
+      DISPLAY_RENDER="${OUTPUT},gl=${GL}";;
+  esac
 
   if [ "${GL}" == "on" ] && [[ "${DISPLAY_DEVICE}" == *"virtio"* ]]; then
     if [ "${QEMU_VER_SHORT}" -ge 61 ]; then
@@ -725,7 +725,7 @@ function vm_boot() {
   SPICE_PORT=$(get_port 5930 9)
   if [ -z "${SPICE_PORT}" ]; then
     echo " - SPICE:    All SPICE ports have been exhausted."
-    if [ "${OUTPUT}" == "none" ] || [ "${OUTPUT}" == "spice-app" ]; then
+    if [ "${OUTPUT}" == "none" ] || [ "${OUTPUT}" == "spice" ] || [ "${OUTPUT}" == "spice-app" ]; then
       echo "             ERROR! Requested SPICE display, but no SPICE ports are free."
       exit 1
     fi
@@ -797,7 +797,7 @@ function vm_boot() {
          ${CPU} ${SMP}
          -m ${RAM_VM} ${BALLOON}
          -smbios type=2,manufacturer="Wimpys World",product="Quickemu",version="${VERSION}",serial="jvzclfjbeyq.pbz",location="wimpysworld.com",asset="${VMNAME}"
-         ${VIDEO} -display ${OUTPUT}
+         ${VIDEO} -display ${DISPLAY_RENDER}
          -device usb-ehci,id=input
          -device usb-kbd,bus=input.0
          -device ${MOUSE},bus=input.0
@@ -918,12 +918,15 @@ function vm_boot() {
   ${QEMU} "${args[@]}" > "${VMDIR}/${VMNAME}.log" &
 
   # If output is 'none' then SPICE was requested.
-  if [ ${OUTPUT} == "none" ]; then
+  if [ "${OUTPUT}" == "spice" ]; then
     if [ -n "${PUBLIC}" ]; then
       spicy --title "${VMNAME}" --port "${SPICE_PORT}" --spice-shared-dir "${PUBLIC}" "${FULLSPICY}" >/dev/null 2>&1 &
     else
       spicy --title "${VMNAME}" --port "${SPICE_PORT}" "${FULLSPICY}" >/dev/null 2>&1 &
     fi
+  elif [ "${OUTPUT}" == "none" ]; then
+    sleep 0.25
+    echo " - PID:      ${VMNAME} ($(cat "${VMDIR}/${VMNAME}.pid"))"
   fi
 }
 
@@ -949,7 +952,7 @@ function usage() {
   echo
   echo "You can also pass optional parameters"
   echo "  --delete                : Delete the disk image."
-  echo "  --display               : Select display backend. 'sdl' (default), 'gtk' or 'spice'"
+  echo "  --display               : Select display backend. 'sdl' (default), 'gtk', 'none', or 'spice'"
   echo "  --fullscreen            : Starts VM in full screen mode (Ctl+Alt+f to exit)"
   echo "  --ignore-msrs-always    : Configure KVM to always ignore unhandle machine-specific registers"
   echo "  --screen <screen>       : Use specified screen to determine the window size."
@@ -1046,7 +1049,7 @@ else
             shift;;
           -display|--display)
             OUTPUT="${2}"
-            if [ "${OUTPUT}" != "gtk" ] && [ "${OUTPUT}" != "sdl" ] && [ "${OUTPUT}" != "spice" ]; then
+            if [ "${OUTPUT}" != "gtk" ] && [ "${OUTPUT}" != "none" ] && [ "${OUTPUT}" != "sdl" ] && [ "${OUTPUT}" != "spice" ]; then
               echo "ERROR! Requested output '${OUTPUT}' is not recognised."
               exit 1
             elif [ "${OUTPUT}" == "spice" ] && ! command -v spicy &>/dev/null; then