enable overriding the gl param

3d acceleration is not stable on some setups (looking at you, nvidia)

quickemu

@@ -221,7 +221,6 @@ function vm_boot() {
   local HOST_CPU_SMT=""
   local HOST_CPU_SOCKETS=""
   local HOST_CPU_VENDOR=""
-  local GL="on"
   local GUEST_TWEAKS=""
   local KERNEL_NAME="Unknown"
   local KERNEL_NODE=""
@@ -734,24 +733,32 @@ function vm_boot() {
       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"
+        gl="off"
       fi
       ;;
     none|spice)
       DISPLAY_RENDER="none";;
+    # spice-app has a bug where using spice-app,gl=off seems to enable gl, but
+    # if the gl param is omitted it works fine.
+    spice-app)
+      DISPLAY_RENDER="${OUTPUT}"
+      if [[ "${gl}" == "on" ]]; then
+        DISPLAY_RENDER+=",gl=on"
+      fi
+      ;;
     *)
-      DISPLAY_RENDER="${OUTPUT},gl=${GL}";;
+      DISPLAY_RENDER="${OUTPUT},gl=${gl}";;
   esac
 
-  if [ "${GL}" == "on" ] && [[ "${DISPLAY_DEVICE}" == *"virtio"* ]]; then
+  if [ "${gl}" == "on" ] && [[ "${DISPLAY_DEVICE}" == *"virtio"* ]]; then
     if [ "${QEMU_VER_SHORT}" -ge 61 ]; then
       DISPLAY_DEVICE="${DISPLAY_DEVICE}-gl"
     else
       DISPLAY_DEVICE="${DISPLAY_DEVICE},virgl=on"
     fi
-    echo ", GL (${GL}), VirGL (on)"
+    echo ", GL (${gl}), VirGL (on)"
   else
-    echo ", GL (${GL}), VirGL (off)"
+    echo ", GL (${gl}), VirGL (off)"
   fi
 
   # Build the video configuration
@@ -1626,6 +1633,12 @@ if [ -n "${VM}" ] && [ -e "${VM}" ]; then
   fi
   viewer_param_check
 
+  # Set the default 3d acceleration. Will be overridden to "off" if
+  # DISPLAY_DEVICE is determined to be virtio-vga since it doesn't work there.
+  if [ -z "${gl}" ]; then
+    gl="on"
+  fi
+
   if [ -z "${PUBLIC}" ]; then
     PUBLIC="${public_dir}"
   fi