feat: Add swipe-to-delete-word functionality

java/res/values/strings-uix.xml

@@ -538,6 +538,9 @@
     <string name="swipe_settings_enable_swipe_typing">Enable swipe typing</string>
     <string name="swipe_settings_enable_swipe_typing_subtitle">Allow swiping from key to key to write words.</string>
 
+    <string name="swipe_settings_delete_word_swipe">Swipe to delete word</string>
+    <string name="swipe_settings_delete_word_swipe_subtitle">Swipe left on the keyboard to delete the last word. Only works when swipe typing is off.</string>
+
     <string name="swipe_settings_sensitive_swipe">Increase sensitivity</string>
     <string name="swipe_settings_sensitive_swipe_subtitle">Make swipe trigger more often</string>
 

java/src/org/futo/inputmethod/engine/IMEInterface.kt

@@ -83,6 +83,7 @@ interface IMEInterface {
 
     fun onMovePointer(steps: Int, stepOverWords: Boolean, select: Boolean?)
     fun onMoveDeletePointer(steps: Int)
+    fun onSelectWordLeft()
     fun onUpWithDeletePointerActive()
     fun onUpWithPointerActive()
     fun onSwipeLanguage(direction: Int)

java/src/org/futo/inputmethod/engine/general/ActionInputTransactionIME.kt

@@ -63,6 +63,7 @@ class ActionInputTransactionIME(val helper: IMEHelper) : IMEInterface, ActionInp
     override fun onCustomRequest(requestCode: Int): Boolean = false
     override fun onMovePointer(steps: Int, stepOverWords: Boolean, select: Boolean?) {}
     override fun onMoveDeletePointer(steps: Int) {}
+    override fun onSelectWordLeft() {}
     override fun onUpWithDeletePointerActive() {}
     override fun onUpWithPointerActive() {}
     override fun onSwipeLanguage(direction: Int) {}

java/src/org/futo/inputmethod/engine/general/ChineseIME.kt

@@ -849,6 +849,7 @@ class ChineseIME(val helper: IMEHelper) : IMEInterface, SuggestionStripViewAcces
         }
         connect?.setSelection(lBound, currentMovingCursor)
     }
+    override fun onSelectWordLeft() {}
     override fun onUpWithDeletePointerActive() {
         anchorOutOfDate = true
         val selection: CharSequence? = connect?.getSelectedText(0)

java/src/org/futo/inputmethod/engine/general/GeneralIME.kt

@@ -672,6 +672,15 @@ class GeneralIME(val helper: IMEHelper) : IMEInterface, WordLearner, SuggestionS
         }
     }
 
+    override fun onSelectWordLeft() {
+        // Select exactly one word to the left, regardless of the backspace-mode setting.
+        // Used by the "left swipe anywhere to delete one word" gesture.
+        setNeutralSuggestionStrip()
+        if (inputLogic.mConnection.hasCursorPosition()) {
+            inputLogic.cursorLeft(-1, true, true)
+        }
+    }
+
     override fun onUpWithDeletePointerActive() {
         if (inputLogic.mConnection.hasSelection()) {
             val selection: CharSequence? = inputLogic.mConnection.getSelectedText(0)

java/src/org/futo/inputmethod/engine/general/JapaneseIME.kt

@@ -1195,6 +1195,8 @@ class JapaneseIME(val helper: IMEHelper) : IMEInterface {
 
     }
 
+    override fun onSelectWordLeft() {}
+
     override fun onUpWithDeletePointerActive() {
 
     }

java/src/org/futo/inputmethod/keyboard/KeyboardActionListener.java

@@ -103,6 +103,7 @@ public interface KeyboardActionListener {
 
     public void onMovePointer(int steps);
     public void onMoveDeletePointer(int steps);
+    public void onSelectWordLeft();
     public void onUpWithDeletePointerActive();
     public void onUpWithPointerActive();
     public void onSwipeLanguage(int direction);
@@ -138,6 +139,8 @@ public void onMovePointer(int steps) {}
         @Override
         public void onMoveDeletePointer(int steps) {}
         @Override
+        public void onSelectWordLeft() {}
+        @Override
         public void onUpWithDeletePointerActive() {}
         @Override
         public void onUpWithPointerActive() {}

java/src/org/futo/inputmethod/keyboard/PointerTracker.java

@@ -156,6 +156,7 @@ public static void setStateHint(StateHint stateHint) {
     private long mStartTime;
     private boolean mStartedOnFastLongPress;
     private boolean mCursorMoved = false;
+    private boolean mIsLeftSwipeDeleteWord = false;
     private boolean mSpacebarLongPressed = false;
 
     // true if keyboard layout has been changed.
@@ -761,6 +762,7 @@ private void onDownEventInternal(final int x, final int y, final long eventTime)
             mStartedOnFastLongPress = key.isFastLongPress();
             mSpacebarLongPressed = false;
 
+            mIsLeftSwipeDeleteWord = false;
             mIsSlidingCursor = key.getCode() == Constants.CODE_DELETE || key.getCode() == Constants.CODE_SPACE;
             mIsFlickingKey = !mIsSlidingCursor && key.getHasFlick();
             mFlickDirection = key.flickDirection(0, 0);
@@ -1021,6 +1023,37 @@ private void onMoveEventInternal(final int x, final int y, final long eventTime)
             return;
         }
 
+        // Left swipe anywhere on the alphabet keyboard deletes exactly one word to the left.
+        // This only fires when glide/swipe typing is off, the stroke starts on a regular key
+        // (not Delete or Space), and the motion is predominantly horizontal and leftward.
+        // Mirror direction for RTL: in RTL, swiping right (toward line start) triggers the
+        // delete, so we negate dx before checking.
+        if (mIsLeftSwipeDeleteWord) {
+            // Already latched: consume remaining moves silently, no normal handling.
+            mLastX = x;
+            mLastY = y;
+            return;
+        }
+
+        if (!sInGesture && !settingsValues.mGestureInputEnabled
+                && !mIsSlidingCursor
+                && settingsValues.mDeleteWordSwipeEnabled
+                && mKeyboard != null && mKeyboard.mId.isAlphabetKeyboard()) {
+            final int dx = x - mStartX;
+            final int dy = y - mStartY;
+            final int threshold = sPointerBigStep;
+            final int adjustedDx = settingsValues.mIsRTL ? -dx : dx;
+            if (adjustedDx <= -threshold && Math.abs(dx) > 2 * Math.abs(dy)) {
+                mIsLeftSwipeDeleteWord = true;
+                mCursorMoved = true;
+                sListener.onSelectWordLeft();
+                mLastX = x;
+                mLastY = y;
+                return;
+            }
+            // Non-qualifying move: fall through to normal drag/flick handling below.
+        }
+
         if(mIsFlickingKey && oldKey != null) {
             final Direction prevDirection = mFlickDirection;
             mFlickDirection = oldKey.flickDirection(x - mStartX, y - mStartY);
@@ -1132,11 +1165,14 @@ private void onUpEventInternal(final int x, final int y, final long eventTime) {
 
         if(mCursorMoved && currentKey != null && currentKey.getCode() == Constants.CODE_DELETE) {
             sListener.onUpWithDeletePointerActive();
+        } else if(mIsLeftSwipeDeleteWord) {
+            sListener.onUpWithDeletePointerActive();
+            mIsLeftSwipeDeleteWord = false;
         } else if(mCursorMoved) {
             sListener.onUpWithPointerActive();
         }
 
-        if(mIsFlickingKey && currentKey != null) {
+        if(mIsFlickingKey && currentKey != null && !mCursorMoved) {
             final Key flickedKey = currentKey.flick(x - mStartX, y - mStartY);
             detectAndSendKey(flickedKey, mKeyX, mKeyY, eventTime);
 
@@ -1192,6 +1228,7 @@ public void cancelTrackingForAction() {
             return;
         }
         mIsTrackingForActionDisabled = true;
+        mIsLeftSwipeDeleteWord = false;
     }
 
     public boolean isInOperation() {
@@ -1284,6 +1321,7 @@ private void onCancelEventInternal() {
         setReleasedKeyGraphics(mCurrentKey, true /* withAnimation */);
         resetKeySelectionByDraggingFinger();
         dismissMoreKeysPanel();
+        mIsLeftSwipeDeleteWord = false;
     }
 
     private boolean isMajorEnoughMoveToBeOnNewKey(final int x, final int y, final long eventTime,

java/src/org/futo/inputmethod/latin/LatinIMELegacy.java

@@ -630,6 +630,13 @@ public void onMoveDeletePointer(int steps) {
         ).onMoveDeletePointer(steps);
     }
 
+    @Override
+    public void onSelectWordLeft() {
+        mImeManager.getActiveIME(
+                mSettings.getCurrent()
+        ).onSelectWordLeft();
+    }
+
     @Override
     public void onUpWithDeletePointerActive() {
         mImeManager.getActiveIME(

java/src/org/futo/inputmethod/latin/settings/Settings.java

@@ -90,6 +90,7 @@ public final class Settings implements SharedPreferences.OnSharedPreferenceChang
     public static final String PREF_BIGRAM_PREDICTIONS = "next_word_prediction";
     public static final String PREF_GESTURE_INPUT = "gesture_input";
     public static final String PREF_GESTURE_INPUT_SENSITIVITY = "gesture_input_sensitivity";
+    public static final String PREF_DELETE_WORD_SWIPE = "delete_word_swipe";
     public static final String PREF_VIBRATION_DURATION_SETTINGS =
             "pref_vibration_duration_settings";
     public static final String PREF_KEYPRESS_SOUND_VOLUME = "pref_keypress_sound_volume";

java/src/org/futo/inputmethod/latin/settings/SettingsValues.java

@@ -86,6 +86,7 @@ public class SettingsValues {
     public final boolean mTransformerPredictionEnabled;
     public final boolean mGestureInputEnabled;
     public final boolean mGestureInputSensitive;
+    public final boolean mDeleteWordSwipeEnabled;
     public final boolean mGestureTrailEnabled;
     public final boolean mGestureFloatingPreviewTextEnabled;
     public final boolean mSlidingKeyInputPreviewEnabled;
@@ -233,6 +234,7 @@ public SettingsValues(final Context context, final SharedPreferences prefs, fina
         mPlausibilityThreshold = Settings.readPlausibilityThreshold(res);
         mGestureInputEnabled = Settings.readGestureInputEnabled(prefs, res);
         mGestureInputSensitive = prefs.getBoolean(Settings.PREF_GESTURE_INPUT_SENSITIVITY, false);
+        mDeleteWordSwipeEnabled = prefs.getBoolean(Settings.PREF_DELETE_WORD_SWIPE, true);
         mGestureTrailEnabled = prefs.getBoolean(Settings.PREF_GESTURE_PREVIEW_TRAIL, true);
         mCloudSyncEnabled = prefs.getBoolean(LocalSettingsConstants.PREF_ENABLE_CLOUD_SYNC, false);
         mAccount = prefs.getString(LocalSettingsConstants.PREF_ACCOUNT_NAME,
@@ -496,6 +498,8 @@ public String dump() {
         sb.append("" + mTransformerPredictionEnabled);
         sb.append("\n   mGestureInputEnabled = ");
         sb.append("" + mGestureInputEnabled);
+        sb.append("\n   mDeleteWordSwipeEnabled = ");
+        sb.append("" + mDeleteWordSwipeEnabled);
         sb.append("\n   mGestureTrailEnabled = ");
         sb.append("" + mGestureTrailEnabled);
         sb.append("\n   mGestureFloatingPreviewTextEnabled = ");

java/src/org/futo/inputmethod/latin/uix/settings/pages/Swipe.kt

@@ -38,6 +38,7 @@ import org.futo.inputmethod.latin.uix.settings.UserSetting
 import org.futo.inputmethod.latin.uix.settings.UserSettingsMenu
 import org.futo.inputmethod.latin.uix.settings.useDataStore
 import org.futo.inputmethod.latin.uix.settings.useDataStoreValue
+import org.futo.inputmethod.latin.uix.settings.useSharedPrefsBool
 import org.futo.inputmethod.latin.uix.settings.userSettingDecorationOnly
 import org.futo.inputmethod.latin.uix.settings.userSettingNavigationItem
 import org.futo.inputmethod.latin.uix.settings.userSettingToggleSharedPrefs
@@ -97,6 +98,14 @@ val SwipeMenu = UserSettingsMenu(
             default = {true},
         ),
 
+        userSettingToggleSharedPrefs(
+            title = R.string.swipe_settings_delete_word_swipe,
+            subtitle = R.string.swipe_settings_delete_word_swipe_subtitle,
+            key = Settings.PREF_DELETE_WORD_SWIPE,
+            default = {true},
+            disabled = { useSharedPrefsBool(Settings.PREF_GESTURE_INPUT, true).value },
+        ),
+
         userSettingToggleSharedPrefs(
             title = R.string.swipe_settings_sensitive_swipe,
             subtitle = R.string.swipe_settings_sensitive_swipe_subtitle,