Read support for customizing through properties

By using the file $HOME/.config/termux/termux.properties it will
be possible to configure the behaviour of:

- The bell character.
- Tapping the terminal.
- The back key.

app/src/main/java/com/termux/app/TermuxPreferences.java

@@ -5,12 +5,38 @@ import com.termux.terminal.TerminalSession;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.preference.PreferenceManager;
+import android.support.annotation.IntDef;
+import android.util.Log;
 import android.util.TypedValue;
+import android.widget.Toast;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.util.Properties;
 
 final class TermuxPreferences {
 
+	@IntDef({BELL_VIBRATE, BELL_BEEP, BELL_IGNORE})
+	@Retention(RetentionPolicy.SOURCE)
+	public @interface AsciiBellBehaviour {}
+
+	static final int BELL_VIBRATE = 1;
+	static final int BELL_BEEP = 2;
+	static final int BELL_IGNORE = 3;
+
+	@IntDef({TAP_TOGGLE_KEYBOARD, TAP_SHOW_MENU, TAP_IGNORE})
+	@Retention(RetentionPolicy.SOURCE)
+	public @interface TapTerminalBehaviour {}
+
+	static final int TAP_TOGGLE_KEYBOARD = 1;
+	static final int TAP_SHOW_MENU = 2;
+	static final int TAP_IGNORE = 3;
+
 	private final int MIN_FONTSIZE;
 	private static final int MAX_FONTSIZE = 256;
+
 	private static final String FULLSCREEN_KEY = "fullscreen";
 	private static final String FONTSIZE_KEY = "fontsize";
 	private static final String CURRENT_SESSION_KEY = "current_session";
@@ -19,7 +45,16 @@ final class TermuxPreferences {
 	private boolean mFullScreen;
 	private int mFontSize;
 
+	@AsciiBellBehaviour
+	int mBellBehaviour = BELL_VIBRATE;
+
+	@TapTerminalBehaviour
+	int mTapBehaviour = TAP_TOGGLE_KEYBOARD;
+
+	boolean mBackIsEscape = true;
+
 	TermuxPreferences(Context context) {
+		reloadFromProperties(context);
 		SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
 
 		float dipInPixels = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 1, context.getResources().getDisplayMetrics());
@@ -86,4 +121,49 @@ final class TermuxPreferences {
 		PreferenceManager.getDefaultSharedPreferences(context).edit().putBoolean(SHOW_WELCOME_DIALOG_KEY, false).apply();
 	}
 
+	public void reloadFromProperties(Context context) {
+		try {
+			File propsFile = new File(TermuxService.HOME_PATH + "/.config/termux/termux.properties");
+			if (propsFile.isFile() && propsFile.canRead()) {
+				Properties props = new Properties();
+				try (FileInputStream in = new FileInputStream(propsFile)) {
+					props.load(in);
+				}
+
+				switch (props.getProperty("bell-character", "vibrate")) {
+					case "beep":
+						mBellBehaviour = BELL_BEEP;
+						break;
+					case "ignore":
+						mBellBehaviour = BELL_IGNORE;
+						break;
+					default: // "vibrate".
+						mBellBehaviour = BELL_VIBRATE;
+						break;
+				}
+
+				switch (props.getProperty("tap-screen", "toggle-keyboard")) {
+					case "show-menu":
+						mTapBehaviour = TAP_SHOW_MENU;
+						break;
+					case "ignore":
+						mTapBehaviour = TAP_IGNORE;
+						break;
+					default: // "toggle-keyboard".
+						mTapBehaviour = TAP_TOGGLE_KEYBOARD;
+						break;
+				}
+
+				mBackIsEscape = !"back".equals(props.getProperty("back-key", "escape"));
+			} else {
+				mBellBehaviour = BELL_VIBRATE;
+				mTapBehaviour = TAP_TOGGLE_KEYBOARD;
+				mBackIsEscape = true;
+			}
+		} catch (Exception e) {
+			Toast.makeText(context, "Error loading properties: " + e.getMessage(), Toast.LENGTH_LONG).show();
+			Log.e("termux", "Error loading props", e);
+		}
+	}
+
 }