Implemented one-handed mode feature

app/src/main/java/org/dslul/openboard/inputmethod/keyboard/KeyboardSwitcher.java

@@ -32,6 +32,7 @@ import org.dslul.openboard.inputmethod.keyboard.emoji.EmojiPalettesView;
 import org.dslul.openboard.inputmethod.keyboard.internal.KeyboardState;
 import org.dslul.openboard.inputmethod.keyboard.internal.KeyboardTextsSet;
 import org.dslul.openboard.inputmethod.latin.InputView;
+import org.dslul.openboard.inputmethod.latin.KeyboardWrapperView;
 import org.dslul.openboard.inputmethod.latin.LatinIME;
 import org.dslul.openboard.inputmethod.latin.R;
 import org.dslul.openboard.inputmethod.latin.RichInputMethodManager;
@@ -51,6 +52,7 @@ public final class KeyboardSwitcher implements KeyboardState.SwitchActions {
     private static final String TAG = KeyboardSwitcher.class.getSimpleName();
 
     private InputView mCurrentInputView;
+    private KeyboardWrapperView mKeyboardViewWrapper;
     private View mMainKeyboardFrame;
     private MainKeyboardView mKeyboardView;
     private EmojiPalettesView mEmojiPalettesView;
@@ -117,7 +119,7 @@ public final class KeyboardSwitcher implements KeyboardState.SwitchActions {
         final KeyboardLayoutSet.Builder builder = new KeyboardLayoutSet.Builder(
                 mThemeContext, editorInfo);
         final Resources res = mThemeContext.getResources();
-        final int keyboardWidth = ResourceUtils.getDefaultKeyboardWidth(res);
+        final int keyboardWidth = ResourceUtils.getKeyboardWidth(res, settingsValues);
         final int keyboardHeight = ResourceUtils.getKeyboardHeight(res, settingsValues);
         builder.setKeyboardGeometry(keyboardWidth, keyboardHeight);
         builder.setSubtype(mRichImm.getCurrentSubtype());
@@ -129,7 +131,8 @@ public final class KeyboardSwitcher implements KeyboardState.SwitchActions {
                 && settingsValues.mIsSplitKeyboardEnabled);
         mKeyboardLayoutSet = builder.build();
         try {
-            mState.onLoadKeyboard(currentAutoCapsState, currentRecapitalizeState);
+            mState.onLoadKeyboard(currentAutoCapsState, currentRecapitalizeState,
+                    settingsValues.mOneHandedModeEnabled);
             mKeyboardTextsSet.setLocale(mRichImm.getCurrentSubtypeLocale(), mThemeContext);
         } catch (KeyboardLayoutSetException e) {
             Log.w(TAG, "loading keyboard failed: " + e.mKeyboardId, e.getCause());
@@ -424,6 +427,30 @@ public final class KeyboardSwitcher implements KeyboardState.SwitchActions {
         }
     }
 
+    // Implements {@link KeyboardState.SwitchActions}.
+    @Override
+    public void setOneHandedModeEnabled(boolean enabled) {
+        if (mKeyboardViewWrapper.getOneHandedModeEnabled() == enabled) {
+            return;
+        }
+        final Settings settings = Settings.getInstance();
+        mKeyboardViewWrapper.setOneHandedModeEnabled(enabled);
+        mKeyboardViewWrapper.setOneHandedGravity(settings.getCurrent().mOneHandedModeGravity);
+
+        settings.writeOneHandedModeEnabled(enabled);
+
+        // Reload the entire keyboard set with the same parameters
+        loadKeyboard(mLatinIME.getCurrentInputEditorInfo(), settings.getCurrent(),
+                mLatinIME.getCurrentAutoCapsState(), mLatinIME.getCurrentRecapitalizeState());
+    }
+
+    // Implements {@link KeyboardState.SwitchActions}.
+    @Override
+    public void switchOneHandedMode() {
+        mKeyboardViewWrapper.switchOneHandedModeSide();
+        Settings.getInstance().writeOneHandedModeGravity(mKeyboardViewWrapper.getOneHandedGravity());
+    }
+
     // Implements {@link KeyboardState.SwitchActions}.
     @Override
     public boolean isInDoubleTapShiftKeyTimeout() {
@@ -476,7 +503,7 @@ public final class KeyboardSwitcher implements KeyboardState.SwitchActions {
         } else if (isShowingClipboardHistory()) {
             return mClipboardHistoryView;
         }
-        return mKeyboardView;
+        return mKeyboardViewWrapper;
     }
 
     public MainKeyboardView getMainKeyboardView() {
@@ -509,6 +536,8 @@ public final class KeyboardSwitcher implements KeyboardState.SwitchActions {
         mEmojiPalettesView = mCurrentInputView.findViewById(R.id.emoji_palettes_view);
         mClipboardHistoryView = mCurrentInputView.findViewById(R.id.clipboard_history_view);
 
+        mKeyboardViewWrapper = mCurrentInputView.findViewById(R.id.keyboard_view_wrapper);
+        mKeyboardViewWrapper.setKeyboardActionListener(mLatinIME);
         mKeyboardView = mCurrentInputView.findViewById(R.id.keyboard_view);
         mKeyboardView.setHardwareAcceleratedDrawingEnabled(isHardwareAcceleratedDrawingEnabled);
         mKeyboardView.setKeyboardActionListener(mLatinIME);

app/src/main/java/org/dslul/openboard/inputmethod/keyboard/internal/KeyboardCodesSet.java

@@ -54,7 +54,10 @@ public final class KeyboardCodesSet {
         "key_alpha_from_emoji",
         "key_unspecified",
         "key_clipboard",
-        "key_alpha_from_clipboard"
+        "key_alpha_from_clipboard",
+        "key_start_onehanded",
+        "key_stop_onehanded",
+        "key_switch_onehanded"
     };
 
     private static final int[] DEFAULT = {
@@ -76,7 +79,10 @@ public final class KeyboardCodesSet {
         Constants.CODE_ALPHA_FROM_EMOJI,
         Constants.CODE_UNSPECIFIED,
         Constants.CODE_CLIPBOARD,
-        Constants.CODE_ALPHA_FROM_CLIPBOARD
+        Constants.CODE_ALPHA_FROM_CLIPBOARD,
+        Constants.CODE_START_ONE_HANDED_MODE,
+        Constants.CODE_STOP_ONE_HANDED_MODE,
+        Constants.CODE_SWITCH_ONE_HANDED_MODE
     };
 
     static {

app/src/main/java/org/dslul/openboard/inputmethod/keyboard/internal/KeyboardIconsSet.java

@@ -62,6 +62,9 @@ public final class KeyboardIconsSet {
     public static final String NAME_CLIPBOARD_ACTION_KEY = "clipboard_action_key";
     public static final String NAME_CLIPBOARD_NORMAL_KEY = "clipboard_normal_key";
     public static final String NAME_CLEAR_CLIPBOARD_KEY = "clear_clipboard_key";
+    public static final String NAME_START_ONEHANDED_KEY = "start_onehanded_mode_key";
+    public static final String NAME_STOP_ONEHANDED_KEY = "stop_onehanded_mode_key";
+    public static final String NAME_SWITCH_ONEHANDED_KEY = "switch_onehanded_key";
 
     private static final SparseIntArray ATTR_ID_TO_ICON_ID = new SparseIntArray();
 
@@ -95,6 +98,9 @@ public final class KeyboardIconsSet {
         NAME_CLIPBOARD_ACTION_KEY,        R.styleable.Keyboard_iconClipboardActionKey,
         NAME_CLIPBOARD_NORMAL_KEY,        R.styleable.Keyboard_iconClipboardNormalKey,
         NAME_CLEAR_CLIPBOARD_KEY,         R.styleable.Keyboard_iconClearClipboardKey,
+        NAME_START_ONEHANDED_KEY,         R.styleable.Keyboard_iconStartOneHandedMode,
+        NAME_STOP_ONEHANDED_KEY,          R.styleable.Keyboard_iconStopOneHandedMode,
+        NAME_SWITCH_ONEHANDED_KEY,        R.styleable.Keyboard_iconSwitchOneHandedMode,
     };
 
     private static int NUM_ICONS = NAMES_AND_ATTR_IDS.length / 2;

app/src/main/java/org/dslul/openboard/inputmethod/keyboard/internal/KeyboardState.java

@@ -30,7 +30,7 @@ import org.dslul.openboard.inputmethod.latin.utils.RecapitalizeStatus;
  *
  * This class contains all keyboard state transition logic.
  *
- * The input events are {@link #onLoadKeyboard(int, int)}, {@link #onSaveKeyboardState()},
+ * The input events are {@link #onLoadKeyboard(int, int, boolean)}, {@link #onSaveKeyboardState()},
  * {@link #onPressKey(int,boolean,int,int)}, {@link #onReleaseKey(int,boolean,int,int)},
  * {@link #onEvent(Event,int,int)}, {@link #onFinishSlidingInput(int,int)},
  * {@link #onUpdateShiftState(int,int)}, {@link #onResetKeyboardStateToAlphabet(int,int)}.
@@ -65,6 +65,9 @@ public final class KeyboardState {
         void startDoubleTapShiftKeyTimer();
         boolean isInDoubleTapShiftKeyTimeout();
         void cancelDoubleTapShiftKeyTimer();
+
+        void setOneHandedModeEnabled(boolean enabled);
+        void switchOneHandedMode();
     }
 
     private final SwitchActions mSwitchActions;
@@ -130,7 +133,8 @@ public final class KeyboardState {
         mRecapitalizeMode = RecapitalizeStatus.NOT_A_RECAPITALIZE_MODE;
     }
 
-    public void onLoadKeyboard(final int autoCapsFlags, final int recapitalizeMode) {
+    public void onLoadKeyboard(final int autoCapsFlags, final int recapitalizeMode,
+                   final boolean onHandedModeEnabled) {
         if (DEBUG_EVENT) {
             Log.d(TAG, "onLoadKeyboard: " + stateToString(autoCapsFlags, recapitalizeMode));
         }
@@ -147,6 +151,7 @@ public final class KeyboardState {
             // Reset keyboard to alphabet mode.
             setAlphabetKeyboard(autoCapsFlags, recapitalizeMode);
         }
+        mSwitchActions.setOneHandedModeEnabled(onHandedModeEnabled);
     }
 
     // Constants for {@link SavedKeyboardState#mShiftMode} and {@link #setShifted(int)}.
@@ -368,6 +373,20 @@ public final class KeyboardState {
         mSwitchActions.setClipboardKeyboard();
     }
 
+    private void setOneHandedModeEnabled(boolean enabled) {
+        if (DEBUG_INTERNAL_ACTION) {
+            Log.d(TAG, "setOneHandedModeEnabled");
+        }
+        mSwitchActions.setOneHandedModeEnabled(enabled);
+    }
+
+    private void switchOneHandedMode() {
+        if (DEBUG_INTERNAL_ACTION) {
+            Log.d(TAG, "switchOneHandedMode");
+        }
+        mSwitchActions.switchOneHandedMode();
+    }
+
     public void onPressKey(final int code, final boolean isSinglePointer, final int autoCapsFlags,
             final int recapitalizeMode) {
         if (DEBUG_EVENT) {
@@ -697,6 +716,12 @@ public final class KeyboardState {
             }
         } else if (code == Constants.CODE_ALPHA_FROM_CLIPBOARD) {
             setAlphabetKeyboard(autoCapsFlags, recapitalizeMode);
+        } else if (code == Constants.CODE_START_ONE_HANDED_MODE) {
+            setOneHandedModeEnabled(true);
+        } else if (code == Constants.CODE_STOP_ONE_HANDED_MODE) {
+            setOneHandedModeEnabled(false);
+        } else if (code == Constants.CODE_SWITCH_ONE_HANDED_MODE) {
+            switchOneHandedMode();
         }
     }
 

app/src/main/java/org/dslul/openboard/inputmethod/latin/KeyboardWrapperView.kt

@@ -0,0 +1,131 @@
+package org.dslul.openboard.inputmethod.latin
+
+import android.annotation.SuppressLint
+import android.content.Context
+import android.util.AttributeSet
+import android.view.Gravity
+import android.view.View
+import android.widget.FrameLayout
+import android.widget.ImageButton
+import org.dslul.openboard.inputmethod.keyboard.KeyboardActionListener
+import org.dslul.openboard.inputmethod.latin.common.Constants
+
+class KeyboardWrapperView @JvmOverloads constructor(
+        context: Context,
+        attrs: AttributeSet? = null,
+        defStyle: Int = 0
+) : FrameLayout(context, attrs, defStyle), View.OnClickListener {
+
+    var keyboardActionListener: KeyboardActionListener? = null
+
+    private lateinit var stopOneHandedModeBtn: ImageButton
+    private lateinit var switchOneHandedModeBtn: ImageButton
+    private lateinit var keyboardView: View
+    private val iconStopOneHandedModeId: Int
+    private val iconSwitchOneHandedModeId: Int
+
+    var oneHandedModeEnabled = false
+        set(enabled) {
+            field = enabled
+            updateViewsVisibility()
+            requestLayout()
+        }
+
+    var oneHandedGravity = Gravity.NO_GRAVITY
+        set(value) {
+            field = value
+            updateSwitchButtonSide()
+            requestLayout()
+        }
+
+
+    override fun onFinishInflate() {
+        super.onFinishInflate()
+        stopOneHandedModeBtn = findViewById(R.id.btn_stop_one_handed_mode)
+        stopOneHandedModeBtn.setImageResource(iconStopOneHandedModeId)
+        stopOneHandedModeBtn.visibility = GONE
+        switchOneHandedModeBtn = findViewById(R.id.btn_switch_one_handed_mode)
+        switchOneHandedModeBtn.setImageResource(iconSwitchOneHandedModeId)
+        switchOneHandedModeBtn.visibility = GONE
+        keyboardView = findViewById(R.id.keyboard_view)
+
+        stopOneHandedModeBtn.setOnClickListener(this)
+        switchOneHandedModeBtn.setOnClickListener(this)
+    }
+
+    @SuppressLint("RtlHardcoded")
+    fun switchOneHandedModeSide() {
+        oneHandedGravity = if (oneHandedGravity == Gravity.LEFT) Gravity.RIGHT else Gravity.LEFT
+    }
+
+    private fun updateViewsVisibility() {
+        stopOneHandedModeBtn.visibility = if (oneHandedModeEnabled) VISIBLE else GONE
+        switchOneHandedModeBtn.visibility = if (oneHandedModeEnabled) VISIBLE else GONE
+    }
+
+    private fun updateSwitchButtonSide() {
+        switchOneHandedModeBtn.scaleX = if (oneHandedGravity == Gravity.RIGHT) -1f else 1f
+    }
+
+    override fun onClick(view: View) {
+        if (view === stopOneHandedModeBtn) {
+            keyboardActionListener?.onCodeInput(Constants.CODE_STOP_ONE_HANDED_MODE,
+                Constants.NOT_A_COORDINATE, Constants.NOT_A_COORDINATE,
+                false /* isKeyRepeat */)
+        } else if (view === switchOneHandedModeBtn) {
+            keyboardActionListener?.onCodeInput(Constants.CODE_SWITCH_ONE_HANDED_MODE,
+                Constants.NOT_A_COORDINATE, Constants.NOT_A_COORDINATE,
+                false /* isKeyRepeat */)
+        }
+    }
+
+    @SuppressLint("RtlHardcoded")
+    override fun onLayout(changed: Boolean, left: Int, top: Int, right: Int, bottom: Int) {
+        if (!oneHandedModeEnabled) {
+            super.onLayout(changed, left, top, right, bottom)
+            return
+        }
+
+        val isLeftGravity = oneHandedGravity == Gravity.LEFT
+        val width = right - left
+        val spareWidth = width - keyboardView.measuredWidth
+
+        val keyboardLeft = if (isLeftGravity) 0 else spareWidth
+        keyboardView.layout(
+                keyboardLeft,
+                0,
+                keyboardLeft + keyboardView.measuredWidth,
+                keyboardView.measuredHeight
+        )
+
+        val buttonsLeft = if (isLeftGravity) keyboardView.measuredWidth else 0
+        stopOneHandedModeBtn.layout(
+                buttonsLeft + (spareWidth - stopOneHandedModeBtn.measuredWidth) / 2,
+                stopOneHandedModeBtn.measuredHeight / 2,
+                buttonsLeft + (spareWidth + stopOneHandedModeBtn.measuredWidth) / 2,
+                3 * stopOneHandedModeBtn.measuredHeight / 2
+        )
+        switchOneHandedModeBtn.layout(
+                buttonsLeft + (spareWidth - switchOneHandedModeBtn.measuredWidth) / 2,
+                2 * stopOneHandedModeBtn.measuredHeight,
+                buttonsLeft + (spareWidth + switchOneHandedModeBtn.measuredWidth) / 2,
+                2 * stopOneHandedModeBtn.measuredHeight + switchOneHandedModeBtn.measuredHeight
+        )
+    }
+
+    init {
+        val keyboardAttr = context.obtainStyledAttributes(attrs,
+                R.styleable.Keyboard, defStyle, R.style.Keyboard)
+        iconStopOneHandedModeId = keyboardAttr.getResourceId(R.styleable.Keyboard_iconStopOneHandedMode, 0)
+        iconSwitchOneHandedModeId = keyboardAttr.getResourceId(R.styleable.Keyboard_iconSwitchOneHandedMode, 0)
+        keyboardAttr.recycle()
+
+        val themeAttr = context.obtainStyledAttributes(attrs,
+                R.styleable.KeyboardTheme, defStyle, 0)
+        val keyboardViewStyleId = themeAttr.getResourceId(R.styleable.KeyboardTheme_mainKeyboardViewStyle, 0)
+        themeAttr.recycle()
+        val styleAttr = context.obtainStyledAttributes(keyboardViewStyleId, intArrayOf(android.R.attr.background))
+        setBackgroundResource(styleAttr.getResourceId(0, 0))
+        styleAttr.recycle()
+    }
+}

app/src/main/java/org/dslul/openboard/inputmethod/latin/LatinIME.java

@@ -1341,11 +1341,11 @@ public class LatinIME extends InputMethodService implements KeyboardActionListen
         }
     }
 
-    int getCurrentAutoCapsState() {
+    public int getCurrentAutoCapsState() {
         return mInputLogic.getCurrentAutoCapsState(mSettings.getCurrent());
     }
 
-    int getCurrentRecapitalizeState() {
+    public int getCurrentRecapitalizeState() {
         return mInputLogic.getCurrentRecapitalizeState();
     }
 

app/src/main/java/org/dslul/openboard/inputmethod/latin/common/Constants.java

@@ -247,8 +247,11 @@ public final class Constants {
     public static final int CODE_SYMBOL_SHIFT = -14;
     public static final int CODE_ALPHA_FROM_EMOJI = -15;
     public static final int CODE_ALPHA_FROM_CLIPBOARD = -16;
+    public static final int CODE_START_ONE_HANDED_MODE = -17;
+    public static final int CODE_STOP_ONE_HANDED_MODE = -18;
+    public static final int CODE_SWITCH_ONE_HANDED_MODE = -19;
     // Code value representing the code is not specified.
-    public static final int CODE_UNSPECIFIED = -17;
+    public static final int CODE_UNSPECIFIED = -20;
 
     public static boolean isLetterCode(final int code) {
         return code >= CODE_SPACE;
@@ -276,6 +279,9 @@ public final class Constants {
         case CODE_TAB: return "tab";
         case CODE_ENTER: return "enter";
         case CODE_SPACE: return "space";
+        case CODE_START_ONE_HANDED_MODE: return "startOneHandedMode";
+        case CODE_STOP_ONE_HANDED_MODE: return "stopOneHandedMode";
+        case CODE_SWITCH_ONE_HANDED_MODE: return "switchOneHandedMode";
         default:
             if (code < CODE_SPACE) return String.format("\\u%02X", code);
             if (code < 0x100) return String.format("%c", code);

app/src/main/java/org/dslul/openboard/inputmethod/latin/inputlogic/InputLogic.java

@@ -717,6 +717,15 @@ public final class InputLogic {
                 // line, so that does affect the contents of the editor.
                 inputTransaction.setDidAffectContents();
                 break;
+            case Constants.CODE_START_ONE_HANDED_MODE:
+            case Constants.CODE_STOP_ONE_HANDED_MODE:
+                // Note: One-handed mode activation is being
+                // handled in {@link KeyboardState#onEvent(Event,int)}.
+                break;
+            case Constants.CODE_SWITCH_ONE_HANDED_MODE:
+                // Note: Switching one-handed side is being
+                // handled in {@link KeyboardState#onEvent(Event,int)}.
+                break;
             default:
                 throw new RuntimeException("Unknown key code : " + event.getMKeyCode());
         }

app/src/main/java/org/dslul/openboard/inputmethod/latin/settings/Settings.java

@@ -16,6 +16,7 @@
 
 package org.dslul.openboard.inputmethod.latin.settings;
 
+import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.content.pm.ApplicationInfo;
@@ -24,6 +25,7 @@ import android.content.res.Resources;
 import android.os.Build;
 import android.util.Log;
 
+import android.view.Gravity;
 import org.dslul.openboard.inputmethod.latin.AudioAndHapticFeedbackManager;
 import org.dslul.openboard.inputmethod.latin.InputAttributes;
 import org.dslul.openboard.inputmethod.latin.R;
@@ -107,6 +109,9 @@ public final class Settings implements SharedPreferences.OnSharedPreferenceChang
             "pref_gesture_floating_preview_text";
     public static final String PREF_SHOW_SETUP_WIZARD_ICON = "pref_show_setup_wizard_icon";
 
+    public static final String PREF_ONE_HANDED_MODE = "pref_one_handed_mode_enabled";
+    public static final String PREF_ONE_HANDED_GRAVITY = "pref_one_handed_mode_gravity";
+
     public static final String PREF_KEY_IS_INTERNAL = "pref_key_is_internal";
 
     public static final String PREF_ENABLE_METRICS_LOGGING = "pref_enable_metrics_logging";
@@ -403,6 +408,23 @@ public final class Settings implements SharedPreferences.OnSharedPreferenceChang
         return prefs.getBoolean(PREF_SHOW_SETUP_WIZARD_ICON, false);
     }
 
+    public static boolean readOneHandedModeEnabled(final SharedPreferences prefs) {
+        return prefs.getBoolean(PREF_ONE_HANDED_MODE, false);
+    }
+
+    public void writeOneHandedModeEnabled(final boolean enabled) {
+        mPrefs.edit().putBoolean(PREF_ONE_HANDED_MODE, enabled).apply();
+    }
+
+    @SuppressLint("RtlHardcoded")
+    public static int readOneHandedModeGravity(final SharedPreferences prefs) {
+        return prefs.getInt(PREF_ONE_HANDED_GRAVITY, Gravity.LEFT);
+    }
+
+    public void writeOneHandedModeGravity(final int gravity) {
+        mPrefs.edit().putInt(PREF_ONE_HANDED_GRAVITY, gravity).apply();
+    }
+
     public static boolean readHasHardwareKeyboard(final Configuration conf) {
         // The standard way of finding out whether we have a hardware keyboard. This code is taken
         // from InputMethodService#onEvaluateInputShown, which canonically determines this.

app/src/main/java/org/dslul/openboard/inputmethod/latin/settings/SettingsValues.java

@@ -82,6 +82,8 @@ public class SettingsValues {
     public final boolean mDeleteSwipeEnabled;
     public final boolean mClipboardHistoryEnabled;
     public final long mClipboardHistoryRetentionTime;
+    public final boolean mOneHandedModeEnabled;
+    public final int mOneHandedModeGravity;
     // Use bigrams to predict the next word when there is no input for it yet
     public final boolean mBigramPredictionEnabled;
     public final boolean mGestureInputEnabled;
@@ -237,6 +239,8 @@ public class SettingsValues {
         mDeleteSwipeEnabled = Settings.readDeleteSwipeEnabled(prefs);
         mClipboardHistoryEnabled = Settings.readClipboardHistoryEnabled(prefs);
         mClipboardHistoryRetentionTime = Settings.readClipboardHistoryRetentionTime(prefs, res);
+        mOneHandedModeEnabled = Settings.readOneHandedModeEnabled(prefs);
+        mOneHandedModeGravity = Settings.readOneHandedModeGravity(prefs);
     }
 
     public boolean isMetricsLoggingEnabled() {

app/src/main/java/org/dslul/openboard/inputmethod/latin/utils/ResourceUtils.java

@@ -182,6 +182,15 @@ public final class ResourceUtils {
         return matchedAll;
     }
 
+    public static int getKeyboardWidth(final Resources res, final SettingsValues settingsValues) {
+        final int defaultKeyboardWidth = getDefaultKeyboardWidth(res);
+        if (settingsValues.mOneHandedModeEnabled) {
+            return (int) res.getFraction(R.fraction.config_one_handed_mode_width_ratio,
+                    defaultKeyboardWidth, defaultKeyboardWidth);
+        }
+        return defaultKeyboardWidth;
+    }
+
     public static int getDefaultKeyboardWidth(final Resources res) {
         final DisplayMetrics dm = res.getDisplayMetrics();
         return dm.widthPixels;

app/src/main/res/layout/main_keyboard_frame.xml

@@ -37,9 +37,30 @@
 
     <!-- To ensure that key preview popup is correctly placed when the current system locale is
          one of RTL locales, layoutDirection="ltr" is needed in the SDK version 17+. -->
-    <org.dslul.openboard.inputmethod.keyboard.MainKeyboardView
-        android:id="@+id/keyboard_view"
-        android:layoutDirection="ltr"
+    <org.dslul.openboard.inputmethod.latin.KeyboardWrapperView
+        android:id="@+id/keyboard_view_wrapper"
         android:layout_width="match_parent"
-        android:layout_height="wrap_content" />
+        android:layout_height="wrap_content"
+        android:layoutDirection="ltr" >
+
+        <org.dslul.openboard.inputmethod.keyboard.MainKeyboardView
+            android:id="@+id/keyboard_view"
+            android:layoutDirection="ltr"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content" />
+
+        <ImageButton
+            android:id="@+id/btn_stop_one_handed_mode"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            style="?attr/suggestionWordStyle" />
+
+        <ImageButton
+            android:id="@+id/btn_switch_one_handed_mode"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            style="?attr/suggestionWordStyle" />
+
+    </org.dslul.openboard.inputmethod.latin.KeyboardWrapperView>
+
 </LinearLayout>

app/src/main/res/values/attrs.xml

@@ -290,6 +290,9 @@
         <attr name="iconClipboardActionKey" format="reference" />
         <attr name="iconClipboardNormalKey" format="reference" />
         <attr name="iconClearClipboardKey" format="reference" />
+        <attr name="iconStartOneHandedMode" format="reference" />
+        <attr name="iconStopOneHandedMode" format="reference" />
+        <attr name="iconSwitchOneHandedMode" format="reference" />
     </declare-styleable>
 
     <declare-styleable name="Keyboard_GridRows">

app/src/main/res/values/config.xml

@@ -27,6 +27,9 @@
 
     <dimen name="config_key_hysteresis_distance">8.0dp</dimen>
 
+    <!-- Amount of width reduction in one-handed mode -->
+    <fraction name="config_one_handed_mode_width_ratio">86%</fraction>
+
     <!-- Preferable keyboard height in absolute scale: 1.285in -->
     <!-- This config_default_keyboard_height value should match with keyboard-heights.xml -->
     <dimen name="config_default_keyboard_height">205.6dp</dimen>

app/src/main/res/values/keyboard-icons-holo.xml

@@ -41,5 +41,8 @@
         <item name="iconClipboardActionKey">@drawable/sym_keyboard_clipboard_holo_dark</item>
         <item name="iconClipboardNormalKey">@drawable/sym_keyboard_clipboard_holo_dark</item>
         <item name="iconClearClipboardKey">@drawable/sym_keyboard_clear_clipboard_holo_dark</item>
+        <item name="iconStartOneHandedMode">@drawable/sym_keyboard_start_onehanded_holo_dark</item>
+        <item name="iconStopOneHandedMode">@drawable/sym_keyboard_stop_onehanded_holo_dark</item>
+        <item name="iconSwitchOneHandedMode">@drawable/sym_keyboard_switch_onehanded_holo_dark</item>
     </style>
 </resources>

app/src/main/res/values/keyboard-icons-lxx-dark-parent.xml

@@ -46,5 +46,8 @@
         <item name="iconClipboardActionKey">@drawable/sym_keyboard_clipboard_lxx_dark</item>
         <item name="iconClipboardNormalKey">@drawable/sym_keyboard_clipboard_lxx_dark</item>
         <item name="iconClearClipboardKey">@drawable/sym_keyboard_clear_clipboard_lxx_dark</item>
+        <item name="iconStartOneHandedMode">@drawable/sym_keyboard_start_onehanded_lxx_dark</item>
+        <item name="iconStopOneHandedMode">@drawable/sym_keyboard_stop_onehanded_lxx_dark</item>
+        <item name="iconSwitchOneHandedMode">@drawable/sym_keyboard_switch_onehanded_lxx_dark</item>
     </style>
 </resources>

app/src/main/res/values/keyboard-icons-lxx-light-parent.xml

@@ -46,5 +46,8 @@
         <item name="iconClipboardActionKey">@drawable/sym_keyboard_clipboard_lxx_dark</item>
         <item name="iconClipboardNormalKey">@drawable/sym_keyboard_clipboard_lxx_light</item>
         <item name="iconClearClipboardKey">@drawable/sym_keyboard_clear_clipboard_lxx_light</item>
+        <item name="iconStartOneHandedMode">@drawable/sym_keyboard_start_onehanded_lxx_light</item>
+        <item name="iconStopOneHandedMode">@drawable/sym_keyboard_stop_onehanded_lxx_light</item>
+        <item name="iconSwitchOneHandedMode">@drawable/sym_keyboard_switch_onehanded_lxx_light</item>
     </style>
 </resources>

app/src/main/res/xml/key_styles_settings.xml

@@ -35,36 +35,36 @@
             latin:languageSwitchKeyEnabled="true"
         >
             <key-style
-                    latin:styleName="settingsMoreKeysStyle"
-                    latin:keyLabelFlags="hasPopupHint"
-                    latin:additionalMoreKeys="!text/keyspec_settings,!text/keyspec_clipboard_normal_key"
-                    latin:backgroundType="functional" />
+                latin:styleName="settingsMoreKeysStyle"
+                latin:keyLabelFlags="hasPopupHint"
+                latin:additionalMoreKeys="!text/keyspec_settings,!text/keyspec_clipboard_normal_key,!text/keyspec_start_onehanded_mode"
+                latin:backgroundType="functional" />
         </case>
         <case
             latin:emojiKeyEnabled="false"
             latin:languageSwitchKeyEnabled="true"
         >
             <key-style
-                    latin:styleName="settingsMoreKeysStyle"
-                    latin:keyLabelFlags="hasPopupHint"
-                    latin:additionalMoreKeys="!text/keyspec_settings,!text/keyspec_clipboard_normal_key,!text/keyspec_emoji_normal_key"
-                    latin:backgroundType="functional" />
+                latin:styleName="settingsMoreKeysStyle"
+                latin:keyLabelFlags="hasPopupHint"
+                latin:additionalMoreKeys="!text/keyspec_settings,!text/keyspec_clipboard_normal_key,!text/keyspec_emoji_normal_key,!text/keyspec_start_onehanded_mode"
+                latin:backgroundType="functional" />
         </case>
         <case
             latin:emojiKeyEnabled="true"
             latin:languageSwitchKeyEnabled="false"
         >
             <key-style
-                    latin:styleName="settingsMoreKeysStyle"
-                    latin:keyLabelFlags="hasPopupHint"
-                    latin:additionalMoreKeys="!text/keyspec_settings,!icon/language_switch_key|!code/key_language_switch,!text/keyspec_clipboard_normal_key"
-                    latin:backgroundType="functional" />
+                latin:styleName="settingsMoreKeysStyle"
+                latin:keyLabelFlags="hasPopupHint"
+                latin:additionalMoreKeys="!text/keyspec_settings,!icon/language_switch_key|!code/key_language_switch,!text/keyspec_clipboard_normal_key,!text/keyspec_start_onehanded_mode"
+                latin:backgroundType="functional" />
         </case>
         <default>
             <key-style
                 latin:styleName="settingsMoreKeysStyle"
                 latin:keyLabelFlags="hasPopupHint"
-                latin:additionalMoreKeys="!text/keyspec_settings,!icon/language_switch_key|!code/key_language_switch,!text/keyspec_clipboard_normal_key,!text/keyspec_emoji_normal_key"
+                latin:additionalMoreKeys="!text/keyspec_settings,!icon/language_switch_key|!code/key_language_switch,!text/keyspec_clipboard_normal_key,!text/keyspec_emoji_normal_key,!text/keyspec_start_onehanded_mode"
                 latin:backgroundType="functional" />
         </default>
     </switch>

tools/make-keyboard-text/src/main/resources/values/donottranslate-more-keys.xml

@@ -262,6 +262,7 @@
     <string name="keyspec_emoji_normal_key">!icon/emoji_normal_key|!code/key_emoji</string>
     <string name="keyspec_clipboard_action_key">!icon/clipboard_action_key|!code/key_clipboard</string>
     <string name="keyspec_clipboard_normal_key">!icon/clipboard_normal_key|!code/key_clipboard</string>
+    <string name="keyspec_start_onehanded_mode">!icon/start_onehanded_mode_key|!code/key_start_onehanded</string>
     <string name="label_go_key">!string/label_go_key</string>
     <string name="label_send_key">!string/label_send_key</string>
     <string name="label_next_key">!string/label_next_key</string>