Add option to delete whole words when holding the delete key

app/src/main/java/helium314/keyboard/latin/LatinIME.kt

@@ -1689,10 +1689,21 @@ class LatinIME : InputMethodService(),
         }
     }
 
+    /** Haptic and audio feedback when holding delete removed a word */
+    fun feedbackForDeletedWord() {
+        try {
+            hapticAndAudioFeedback(KeyCode.DELETE, 0, HapticEvent.KEY_PRESS)
+        } catch (e: Exception) {
+            Log.w(TAG, "no feedback for deleted word", e)
+        }
+    }
+
     fun hapticAndAudioFeedback(code: Int, repeatCount: Int, hapticEvent: HapticEvent) {
         val keyboardView = keyboardSwitcher.mainKeyboardView
         if (keyboardView != null && keyboardView.isInDraggingFinger()) return
 
+        // holding delete removes whole words: feedback comes per word, see feedbackForDeletedWord
+        if (repeatCount > 0 && code == KeyCode.DELETE && inputLogic.isBackspaceWordModeActive(mSettings.current)) return
         if (repeatCount > 0) {
             when (code) {
                 KeyCode.DELETE, KeyCode.ARROW_LEFT, KeyCode.ARROW_UP, KeyCode.WORD_LEFT, KeyCode.PAGE_UP -> if (!inputLogic.connection.canDeleteCharacters()) return

app/src/main/java/helium314/keyboard/latin/inputlogic/InputLogic.kt

@@ -89,6 +89,13 @@ class InputLogic(
     private var mTypedWordOnShiftPress: String? = null
 
     private var mDeleteCount = 0
+    // for "backspace repeat deletes words": repeat ticks in the current hold, and words deleted so far
+    private var mBackspaceRepeatTicks = 0
+    private var mBackspaceWordsDeleted = 0
+    /** time (ms after the first key repeat) when the next word is deleted */
+    private var mBackspaceNextWordTime = 0f
+    /** word deletion not possible in the current hold (no text available), normal deletion is used */
+    private var mBackspaceWordModeFailed = false
     private var mLastKeyTime = 0L
     private var mEnteredText: String? = null
     private var mIsAutoCorrectionIndicatorOn = false
@@ -1350,6 +1357,65 @@ class InputLogic(
         }
     }
 
+    /**
+     * Whether holding delete currently removes whole words. Not for languages without spaces, where
+     * a "word" may be a whole sentence. Also used to give feedback per word instead of per key repeat.
+     */
+    fun isBackspaceWordModeActive(settingsValues: SettingsValues): Boolean =
+        settingsValues.mBackspaceRepeatDeletesWords
+            && settingsValues.mSpacingAndPunctuations.mCurrentLanguageHasSpaces
+            && !mBackspaceWordModeFailed
+
+    /**
+     * When the option is enabled and the delete key is held down, switch from deleting characters
+     * to deleting whole words after a short while. Words are deleted with increasing speed.
+     * Returns true if the event was consumed (a word was deleted, or this repeat tick is skipped).
+     */
+    private fun handleBackspaceRepeatWordDeletion(event: Event, settingsValues: SettingsValues): Boolean {
+        if (!event.isKeyRepeat || mDeleteCount <= 1) {
+            // new press of the delete key
+            mBackspaceRepeatTicks = 0
+            mBackspaceWordsDeleted = 0
+            mBackspaceNextWordTime = 0f
+            mBackspaceWordModeFailed = false
+        }
+        if (!event.isKeyRepeat) return false
+        mBackspaceRepeatTicks++
+        if (!isBackspaceWordModeActive(settingsValues)) return false
+        // key repeats come in fixed intervals, so we can count time in repeats
+        val time = (mBackspaceRepeatTicks - 1) * KEY_REPEAT_INTERVAL_MS
+        if (time < mBackspaceNextWordTime) return true // wait between words
+
+        if (mWordComposer.isComposingWord()) {
+            mConnection.finishComposingText()
+            resetComposingState(true)
+        }
+        // with very short intervals, more than one word may be due per key repeat
+        var deletedWords = 0
+        while (time >= mBackspaceNextWordTime && deletedWords < 2) {
+            val textBefore = mConnection.getTextBeforeCursor(BACKSPACE_WORD_LOOKBACK, 0)?.toString()
+            if (textBefore == null) { // fall back to normal deletion
+                mBackspaceWordModeFailed = true
+                return deletedWords > 0
+            }
+            if (textBefore.isEmpty()) return true
+            val length = textBefore.length - getStartOfPreviousWord(textBefore)
+            if (InputTypeUtils.isWebEditor(getCurrentInputEditorInfo())) {
+                repeat(length) { sendDownUpKeyEvent(KeyEvent.KEYCODE_DEL) }
+            } else {
+                mConnection.deleteTextBeforeCursor(length)
+            }
+            StatsUtils.onBackspaceWordDelete(length)
+            mBackspaceNextWordTime += getBackspaceWordInterval(mBackspaceWordsDeleted)
+            mBackspaceWordsDeleted++
+            deletedWords++
+        }
+        mSuggestionStripViewAccessor.setNeutralSuggestionStrip()
+        // one feedback per deleted word, key repeat feedback is suppressed in word mode
+        mLatinIME.feedbackForDeletedWord()
+        return true
+    }
+
     private fun handleBackspaceEvent(event: Event, inputTransaction: InputTransaction) {
         val currentKeyboardScript = inputTransaction.settingsValues.mCurrentKeyboardScript
         mSpaceState = SpaceState.NONE
@@ -1410,6 +1476,8 @@ class InputLogic(
         }
         inputTransaction.requireShiftUpdate(shiftUpdateKind)
 
+        if (handleBackspaceRepeatWordDeletion(event, inputTransaction.settingsValues)) return
+
         if (mWordComposer.isCursorFrontOrMiddleOfComposingWord()) {
             unlearnWord(mWordComposer.getTypedWord(), inputTransaction.settingsValues, Constants.EVENT_BACKSPACE)
             resetEntireInputState(mConnection.expectedSelectionStart, mConnection.expectedSelectionEnd, true)
@@ -2947,10 +3015,42 @@ class InputLogic(
     companion object {
         private const val TAG = "InputLogic"
         private const val INLINE_EMOJI_SEARCH_MARKER = ':'
+        private const val KEY_REPEAT_INTERVAL_MS = 50
+        /** interval before the second word, it gets shorter with each word until the minimum */
+        private const val BACKSPACE_WORD_START_INTERVAL = 350f
+        private const val BACKSPACE_WORD_ACCELERATION = 0.8f
+        private const val BACKSPACE_WORD_MIN_INTERVAL = 80f
+
+        /** Time until the next word is deleted, after [wordsDeleted] words were deleted already */
+        fun getBackspaceWordInterval(wordsDeleted: Int): Float {
+            var interval = BACKSPACE_WORD_START_INTERVAL
+            repeat(wordsDeleted.coerceAtMost(30)) { interval *= BACKSPACE_WORD_ACCELERATION }
+            return interval.coerceAtLeast(BACKSPACE_WORD_MIN_INTERVAL)
+        }
+        private const val BACKSPACE_WORD_LOOKBACK = 200
         private val THAI_LOCALE = Locale.forLanguageTag("th")
         private val THAI_WORD_BREAK_ITERATOR = ThreadLocal.withInitial { BreakIterator.getWordInstance(THAI_LOCALE) }
         private val CURSOR_PATTERN = java.util.regex.Pattern.compile("%cursor(\\d+)%")
 
+        /**
+         * Index where the word before the end of [text] starts, including whitespace and punctuation
+         * after it, but keeping the whitespace before it (so "one two " -> "one ").
+         */
+        internal fun getStartOfPreviousWord(text: String): Int {
+            var i = text.length
+            fun skipWhile(predicate: (Int) -> Boolean) {
+                while (i > 0) {
+                    val cp = Character.codePointBefore(text, i)
+                    if (!predicate(cp)) break
+                    i -= Character.charCount(cp)
+                }
+            }
+            skipWhile { Character.isWhitespace(it) }
+            skipWhile { !Character.isLetterOrDigit(it) && !Character.isWhitespace(it) }
+            skipWhile { Character.isLetterOrDigit(it) }
+            return i
+        }
+
         fun isSpaceStrippingPunctuation(codePoint: Int): Boolean {
             return codePoint == '.'.code
                 || codePoint == ','.code

app/src/main/java/helium314/keyboard/latin/settings/Defaults.kt

@@ -94,6 +94,7 @@ object Defaults {
     const val PREF_AUTO_CORRECT_THRESHOLD = 0.185f
     const val PREF_AUTOCORRECT_SHORTCUTS = true
     const val PREF_BACKSPACE_REVERTS_AUTOCORRECT = true
+    const val PREF_BACKSPACE_REPEAT_DELETES_WORDS = false
     const val PREF_CENTER_SUGGESTION_TEXT_TO_ENTER = false
     const val PREF_CENTER_TYPED_WORD = false
     const val PREF_SHOW_SUGGESTIONS = true

app/src/main/java/helium314/keyboard/latin/settings/Settings.kt

@@ -343,6 +343,7 @@ class Settings private constructor() : SharedPreferences.OnSharedPreferenceChang
         const val PREF_AUTO_CORRECT_THRESHOLD = "auto_correct_threshold"
         const val PREF_AUTOCORRECT_SHORTCUTS = "autocorrect_shortcuts"
         const val PREF_BACKSPACE_REVERTS_AUTOCORRECT = "backspace_reverts_autocorrect"
+        const val PREF_BACKSPACE_REPEAT_DELETES_WORDS = "backspace_repeat_deletes_words"
         const val PREF_CENTER_SUGGESTION_TEXT_TO_ENTER = "center_suggestion_text_to_enter"
         const val PREF_CENTER_TYPED_WORD = "center_typed_word"
         const val PREF_SHOW_SUGGESTIONS = "show_suggestions"

app/src/main/java/helium314/keyboard/latin/settings/SettingsValues.kt

@@ -219,6 +219,7 @@ open class SettingsValues(
     val mRememberFloatingKeyboard: Boolean
     val mPersistTextEditMode: Boolean
     val mBackspaceRevertsAutocorrect: Boolean
+    val mBackspaceRepeatDeletesWords: Boolean
     val mDisableMultiWordSuggestions: Boolean
     val mPrioritizePersonalSuggestions: Boolean
     val mSuggestionBalance: Int
@@ -360,6 +361,7 @@ open class SettingsValues(
         mRememberFloatingKeyboard = prefs.getBoolean(Settings.PREF_REMEMBER_FLOATING_KEYBOARD, Defaults.PREF_REMEMBER_FLOATING_KEYBOARD)
         mPersistTextEditMode = prefs.getBoolean(Settings.PREF_PERSIST_TEXT_EDIT_MODE, Defaults.PREF_PERSIST_TEXT_EDIT_MODE)
         mBackspaceRevertsAutocorrect = prefs.getBoolean(Settings.PREF_BACKSPACE_REVERTS_AUTOCORRECT, Defaults.PREF_BACKSPACE_REVERTS_AUTOCORRECT)
+        mBackspaceRepeatDeletesWords = prefs.getBoolean(Settings.PREF_BACKSPACE_REPEAT_DELETES_WORDS, Defaults.PREF_BACKSPACE_REPEAT_DELETES_WORDS)
         mDisableMultiWordSuggestions = prefs.getBoolean(Settings.PREF_DISABLE_MULTI_WORD_SUGGESTIONS, Defaults.PREF_DISABLE_MULTI_WORD_SUGGESTIONS)
         mBigramPredictionEnabled = prefs.getBoolean(Settings.PREF_BIGRAM_PREDICTIONS, Defaults.PREF_BIGRAM_PREDICTIONS)
         mPrioritizePersonalSuggestions = prefs.getBoolean(Settings.PREF_PRIORITIZE_PERSONAL_SUGGESTIONS, Defaults.PREF_PRIORITIZE_PERSONAL_SUGGESTIONS)

app/src/main/java/helium314/keyboard/settings/screens/TextCorrectionScreen.kt

@@ -59,6 +59,7 @@ fun TextCorrectionScreen(
             if (autocorrectEnabled) Settings.PREF_AUTO_CORRECT_AGGRESSIVENESS else null,
             if (autocorrectEnabled) Settings.PREF_AUTO_CORRECT_TRIGGER else null,
             if (autocorrectEnabled) Settings.PREF_BACKSPACE_REVERTS_AUTOCORRECT else null,
+            Settings.PREF_BACKSPACE_REPEAT_DELETES_WORDS,
             if (autocorrectEnabled) Settings.PREF_EXPAND_FINE_TUNE_AUTOCORRECT else null,
             if (autocorrectEnabled && fineTuneAutocorrectExpanded) Settings.PREF_AUTO_CORRECT_THRESHOLD else null,
             if (autocorrectEnabled && fineTuneAutocorrectExpanded) Settings.PREF_MORE_AUTO_CORRECTION else null,
@@ -215,6 +216,11 @@ fun createCorrectionSettings(context: Context) = listOf(
     Setting(context, Settings.PREF_BACKSPACE_REVERTS_AUTOCORRECT, R.string.backspace_reverts_autocorrect) {
         SwitchPreference(it, Defaults.PREF_BACKSPACE_REVERTS_AUTOCORRECT)
     },
+    Setting(context, Settings.PREF_BACKSPACE_REPEAT_DELETES_WORDS,
+        R.string.backspace_repeat_deletes_words, R.string.backspace_repeat_deletes_words_summary
+    ) {
+        SwitchPreference(it, Defaults.PREF_BACKSPACE_REPEAT_DELETES_WORDS)
+    },
     Setting(context, Settings.PREF_AUTO_CAP,
         R.string.auto_cap, R.string.auto_cap_summary
     ) {

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

@@ -408,6 +408,8 @@
     <string name="subtype_dag">Dagbani</string>
     <string name="subtype_st">Sesotho</string>
     <string name="backspace_reverts_autocorrect">Rücktaste macht Autokorrektur rückgängig</string>
+    <string name="backspace_repeat_deletes_words">Gedrückte Löschtaste löscht ganze Wörter</string>
+    <string name="backspace_repeat_deletes_words_summary">Nach kurzem Halten der Löschtaste wortweise löschen, zunehmend schneller</string>
     <string name="autospace_after_suggestion">Automatische Leerzeichen nach Auswählen eines Vorschlags</string>
     <string name="prefs_emoji_key_fit">Skaliere den Emoji-Knopf mit der Schriftgröße</string>
     <string name="backup_restored">Backup wiederhergestellt</string>

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

@@ -184,6 +184,10 @@
     <string name="large_screen_layout_note">Settings on this screen apply to large-screen layout</string>
     <!-- Option to undo auto correction with backspace -->
     <string name="backspace_reverts_autocorrect">Backspace reverts autocorrect</string>
+    <!-- Option to delete whole words when holding the delete key -->
+    <string name="backspace_repeat_deletes_words">Holding delete removes whole words</string>
+    <!-- Description for "backspace_repeat_deletes_words" option -->
+    <string name="backspace_repeat_deletes_words_summary">After holding the delete key for a moment, delete word by word with increasing speed</string>
     <!-- Option to disable auto correction. -->
     <string name="auto_correction_threshold_mode_off">Off</string> <!-- todo: use it or remove it -->
     <!-- Option to suggest auto correction suggestions modestly. Auto-corrects only to a word which has small edit distance from typed word. -->

app/src/test/java/helium314/keyboard/latin/InputLogicTest.kt

@@ -1576,6 +1576,66 @@ class InputLogicTest {
         assertEquals("", composingText)
     }
 
+    @Test fun `held backspace deletes whole words when enabled`() {
+        reset()
+        latinIME.prefs().edit { putBoolean(Settings.PREF_BACKSPACE_REPEAT_DELETES_WORDS, true) }
+        setText("eins zwei drei vier fuenf sechs sieben")
+        functionalKeyPress(KeyCode.DELETE) // a single press deletes one character
+        assertEquals("eins zwei drei vier fuenf sechs siebe", text)
+        // the first key repeat deletes the rest of the word
+        functionalKeyPress(KeyCode.DELETE, isKeyRepeat = true)
+        assertEquals("eins zwei drei vier fuenf sechs ", text)
+        // some repeats pass without deleting before the next word
+        for (i in 1..6) {
+            functionalKeyPress(KeyCode.DELETE, isKeyRepeat = true)
+        }
+        assertEquals("eins zwei drei vier fuenf sechs ", text)
+        functionalKeyPress(KeyCode.DELETE, isKeyRepeat = true)
+        assertEquals("eins zwei drei vier fuenf ", text)
+        // keep holding: everything gets deleted word by word
+        for (i in 1..30) {
+            functionalKeyPress(KeyCode.DELETE, isKeyRepeat = true)
+        }
+        assertEquals("", text)
+    }
+
+    @Test fun `held backspace word deletion accelerates`() {
+        reset()
+        latinIME.prefs().edit { putBoolean(Settings.PREF_BACKSPACE_REPEAT_DELETES_WORDS, true) }
+        setText("a b c d e f g h")
+        functionalKeyPress(KeyCode.DELETE) // deletes "h"
+        // key repeats every 50 ms: repeat 1 at 0 ms ... repeat 22 at 1050 ms
+        for (i in 1..22) functionalKeyPress(KeyCode.DELETE, isKeyRepeat = true)
+        // recommended: words at 0, 350, 630, 854, 1033 ms
+        assertEquals("a b ", text)
+    }
+
+    @Test fun `backspace word intervals`() {
+        assertEquals(350f, InputLogic.getBackspaceWordInterval(0), 0.01f)
+        assertEquals(280f, InputLogic.getBackspaceWordInterval(1), 0.01f)
+        assertEquals(80f, InputLogic.getBackspaceWordInterval(20), 0.01f) // minimum
+    }
+
+    @Test fun `start of previous word keeps whitespace before the word`() {
+        fun remaining(text: String) = text.substring(0, InputLogic.getStartOfPreviousWord(text))
+        assertEquals("Hallo, ", remaining("Hallo, Welt! "))
+        assertEquals("", remaining("Hallo, "))
+        assertEquals("", remaining("Hallo"))
+        assertEquals("eins ", remaining("eins zwei"))
+        assertEquals("", remaining("   "))
+    }
+
+    @Test fun `held backspace deletes characters only when word deletion is disabled`() {
+        reset()
+        latinIME.prefs().edit { putBoolean(Settings.PREF_BACKSPACE_REPEAT_DELETES_WORDS, false) }
+        setText("eins zwei drei vier")
+        functionalKeyPress(KeyCode.DELETE)
+        for (i in 1..15) {
+            functionalKeyPress(KeyCode.DELETE, isKeyRepeat = true)
+        }
+        assertEquals("ein", text) // with word deletion, "eins" would be gone completely
+    }
+
     @Test fun timestamp() {
         reset()
         chainInput("hello")