Add plugs to allow user to access ~/.java and ~/.openrocket

Add plugs which use the personal-files interface for snaps to allow
the users to enable OpenRocket to access the ~/.java and ~/.openrocket
directories. Currently, these must be manually connected by the user,
so the launcher is updated to ensure the user experience degrades
appropriately when they are not connected.

This method allows for new installations to OpenRocket without any
changes and for users migrating to the snap from the jar to be able
to connect their existing preferences and databases.

Signed-off-by: Billy Olsen <billy.olsen@gmail.com>

snap/local/launcher

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 JAVA_BIN="$JAVA_HOME/bin/java"
 
@@ -6,8 +6,18 @@ export DESKTOP_SESSION=gnome
 export XDG_SESSION_DESKTOP=gnome
 export XDG_CURRENT_DESKTOP=GNOME
 
+JAVA_OPTS="-Dsun.java2d.xrender=true -Dprism.useFontConfig=false -Dawt.useSystemAAFontSettings=on -Dswing.aatext=true -Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel -Dswing.crossplatformlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel -Djava.io.tmpdir=$SNAP_USER_COMMON"
+
+if ! snapctl is-connected preferences; then
+    JAVA_OPTS="$JAVA_OPTS -Djava.util.prefs.userRoot=$SNAP_USER_COMMON/"
+fi
+
+if ! snapctl is-connected openrocket-db; then
+    JAVA_OPTS="$JAVA_OPTS -Duser.home=$SNAP_USER_COMMON/"
+fi
+
+export _JAVA_OPTIONS=$JAVA_OPTS
 # Fix font / theme
-export _JAVA_OPTIONS="-Dsun.java2d.xrender=true -Dprism.useFontConfig=false -Dawt.useSystemAAFontSettings=on -Dswing.aatext=true -Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel -Dswing.crossplatformlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel -Djava.util.prefs.userRoot=$SNAP_USER_COMMON/"
 export JAVA_FONTS=$SNAP/usr/share/fonts/truetype
 exec $JAVA_BIN -jar $SNAP/OpenRocket.jar "$@"
 

snap/snapcraft.yaml

@@ -20,6 +20,20 @@ base: core18
 grade: stable
 confinement: strict
 
+plugs:
+  preferences:
+    interface: personal-files
+    read:
+      - $HOME/.java
+    write:
+      - $HOME/.java
+  openrocket-db:
+    interface: personal-files
+    read:
+      - $HOME/.openrocket
+    write:
+      - $HOME/.openrocket
+
 apps:
   openrocket:
     extensions:
@@ -30,6 +44,8 @@ apps:
       - network
       - cups-control
       - opengl
+      - preferences
+      - openrocket-db
     environment:
       JAVA_HOME: "$SNAP/usr/lib/jvm/java-11-openjdk-amd64"