Various changes

* show full-screen option only for Android 4.4+ (no immersive mode below)
* show toast with destination IP address at start-up
* add option to keep display active (fixes #71)

app-android/app/src/main/java/at/bitfire/gfxtablet/CanvasActivity.java

@@ -1,14 +1,18 @@
 package at.bitfire.gfxtablet;
 
 import android.content.Intent;
+import android.content.SharedPreferences;
 import android.net.Uri;
 import android.os.AsyncTask;
+import android.os.Build;
 import android.os.Bundle;
 import android.preference.PreferenceManager;
 import android.support.v7.app.ActionBarActivity;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
+import android.view.WindowManager;
+import android.widget.Toast;
 
 public class CanvasActivity extends ActionBarActivity {
     NetworkClient netClient;
@@ -24,6 +28,10 @@ public class CanvasActivity extends ActionBarActivity {
     protected void onResume() {
         super.onResume();
 
+        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
+        if (prefs.getBoolean(SettingsActivity.KEY_KEEP_DISPLAY_ACTIVE, false))
+            getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
+
         new ConfigureNetworkingTask().execute();
     }
 
@@ -39,6 +47,12 @@ public class CanvasActivity extends ActionBarActivity {
 		return true;
 	}
 
+    @Override
+    public boolean onPrepareOptionsMenu(Menu menu) {
+        menu.findItem(R.id.menu_fullscreen).setVisible(Build.VERSION.SDK_INT >= 19);
+        return true;
+    }
+
 	public void showAbout(MenuItem item) {
 		startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(("https://rfc2822.github.io/GfxTablet/"))));
 	}
@@ -70,6 +84,8 @@ public class CanvasActivity extends ActionBarActivity {
             if (success) {
                 setContentView(new CanvasView(CanvasActivity.this, netClient));
                 new Thread(netClient).start();
+
+                Toast.makeText(CanvasActivity.this, "Touch events will be sent to " + netClient.destAddress.getHostAddress() + ":" + NetworkClient.GFXTABLET_PORT, Toast.LENGTH_LONG).show();
             } else
                 setContentView(R.layout.activity_no_host);
         }

app-android/app/src/main/java/at/bitfire/gfxtablet/SettingsActivity.java

@@ -7,7 +7,8 @@ public class SettingsActivity extends ActionBarActivity {
     public static final String
 		KEY_PREF_HOST = "host_preference",
 		KEY_PREF_STYLUS_ONLY = "stylus_only_preference",
-        KEY_DARK_CANVAS = "dark_canvas_preference";
+        KEY_DARK_CANVAS = "dark_canvas_preference",
+        KEY_KEEP_DISPLAY_ACTIVE = "keep_display_active_preference";
     
     @Override
     protected void onCreate(Bundle savedInstanceState) {

app-android/app/src/main/res/menu/activity_canvas.xml

@@ -2,13 +2,16 @@
     xmlns:app="http://schemas.android.com/apk/res-auto">
 
     <item
+        android:id="@+id/menu_fullscreen"
         android:onClick="switchFullScreen"
         android:title="Fullscreen"
+        android:icon="@drawable/ic_arrow_expand_white_48dp"
         app:showAsAction="always" />
 
     <item
         android:onClick="showSettings"
         android:title="@string/menu_settings"
+        android:icon="@drawable/ic_settings_white_48dp"
         app:showAsAction="ifRoom" />
 
     <item

app-android/app/src/main/res/values/strings.xml

@@ -12,9 +12,11 @@
     <string name="preferences_stylus_only">Sense stylus only</string>
     <string name="preferences_stylus_only_on">Only stylus input will be processed</string>
     <string name="preferences_stylus_only_off">Finger and stylus input will be processed</string>
-
     <string name="preferences_dark_canvas">Use dark canvas</string>
     <string name="preferences_dark_canvas_on">Black canvas will be used</string>
     <string name="preferences_dark_canvas_off">White canvas will be used</string>
+    <string name="preferences_keep_display_active">Keep display active</string>
+    <string name="preferences_keep_display_active_on">Display won\'t turn off while GfxTablet is active</string>
+    <string name="preferences_keep_display_active_off">Display will turn off according to system settings</string>
 
 </resources>

app-android/app/src/main/res/xml/preferences.xml

@@ -10,6 +10,13 @@
     </PreferenceCategory>
 
     <PreferenceCategory android:title="Drawing preferences">
+        <CheckBoxPreference
+            android:defaultValue="false"
+            android:key="keep_display_active_preference"
+            android:title="@string/preferences_keep_display_active"
+            android:summaryOn="@string/preferences_keep_display_active_on"
+            android:summaryOff="@string/preferences_keep_display_active_off" />
+
         <CheckBoxPreference
             android:defaultValue="false"
             android:key="stylus_only_preference"