LatinIME: Implement slide-to-delete on backspace key

Change-Id: Ia38e8d6f72bec53cd2f12e708875dcdc2eb9370a

Author: pgaskin

java/res/values/cm_strings.xml

@@ -40,6 +40,10 @@ disposition rather than other common dispositions for Latin languages. [CHAR LIM
     <string name="space_trackpad">Space bar trackpad</string>
     <string name="space_trackpad_summary">Swipe on the spacebar to move the cursor</string>
 
+    <!-- Preference item for the backspace key track pad -->
+    <string name="backspace_trackpad">Backspace key trackpad</string>
+    <string name="backspace_trackpad_summary">Swipe on the backspace key to delete words</string>
+
     <!-- Preference item for enabling longpress key hints -->
     <string name="show_longpress_hints">Show long-press key hints</string>
     <string name="show_longpress_hints_summary">Shows long-press hints for supported keys</string>

java/res/xml/prefs_screen_advanced.xml

@@ -53,6 +53,11 @@
         android:title="@string/space_trackpad"
         android:summary="@string/space_trackpad_summary"
         android:defaultValue="true" />
+    <CheckBoxPreference
+        android:key="pref_backspace_trackpad"
+        android:title="@string/backspace_trackpad"
+        android:summary="@string/backspace_trackpad_summary"
+        android:defaultValue="true" />
     <com.android.inputmethod.latin.settings.SeekBarDialogPreference
         android:key="pref_keyboard_height_scale"
         android:title="@string/prefs_keyboard_height_scale"

java/src/com/android/inputmethod/keyboard/KeyboardActionListener.java

@@ -106,6 +106,16 @@ public interface KeyboardActionListener {
      */
     public void onMovePointer(int steps);
 
+    /**
+     * Called while user is sliding backspace key.
+     */
+    public void onBackspaceSlide(int steps);
+
+    /**
+     * Called when user finished sliding backspace key.
+     */
+    public void onBackspaceSlideFinished();
+
     public static final KeyboardActionListener EMPTY_LISTENER = new Adapter();
 
     public static class Adapter implements KeyboardActionListener {
@@ -135,5 +145,9 @@ public boolean onCustomRequest(int requestCode) {
         }
         @Override
         public void onMovePointer(int steps) {}
+        @Override
+        public void onBackspaceSlide(int steps) {}
+        @Override
+        public void onBackspaceSlideFinished() {}
     }
 }

java/src/com/android/inputmethod/keyboard/PointerTracker.java

@@ -86,6 +86,7 @@ public PointerTrackerParams(final TypedArray mainKeyboardViewAttr) {
     // Parameters for pointer handling.
     private static PointerTrackerParams sParams;
     private static int sPointerStep;
+    private static int sPointerWordStep;
     private static GestureStrokeRecognitionParams sGestureStrokeRecognitionParams;
     private static GestureStrokeDrawingParams sGestureStrokeDrawingParams;
     private static boolean sNeedsPhantomSuddenMoveEventHack;
@@ -129,11 +130,12 @@ public PointerTrackerParams(final TypedArray mainKeyboardViewAttr) {
     private int mLastX;
     private int mLastY;
 
-    // For spacebar slide tracking.
+    // For spacebar/backspace slide tracking.
     private int mStartX;
     private int mStartY;
     private long mStartTime;
     private boolean mSlidOnSpaceBar = false;
+    private boolean mSlidOnBackspace = false;
 
     // true if keyboard layout has been changed.
     private boolean mKeyboardLayoutHasBeenChanged;
@@ -164,6 +166,7 @@ public static void init(final TypedArray mainKeyboardViewAttr, final TimerProxy
             final DrawingProxy drawingProxy) {
         sParams = new PointerTrackerParams(mainKeyboardViewAttr);
         sPointerStep = (int)(10.0 * Resources.getSystem().getDisplayMetrics().density);
+        sPointerWordStep = (int)(20.0 * Resources.getSystem().getDisplayMetrics().density);
         sGestureStrokeRecognitionParams = new GestureStrokeRecognitionParams(mainKeyboardViewAttr);
         sGestureStrokeDrawingParams = new GestureStrokeDrawingParams(mainKeyboardViewAttr);
         sTypingTimeRecorder = new TypingTimeRecorder(
@@ -296,6 +299,9 @@ private void callListenerOnCodeInput(final Key key, final int primaryCode, final
         if (ignoreModifierKey) {
             return;
         }
+        if (mSlidOnBackspace && code == Constants.CODE_DELETE) {
+            return;
+        }
         // Even if the key is disabled, it should respond if it is in the altCodeWhileTyping state.
         if (key.isEnabled() || altersCode) {
             sTypingTimeRecorder.onCodeInput(code, eventTime);
@@ -925,6 +931,20 @@ private void onMoveEventInternal(final int x, final int y, final long eventTime)
             return;
         }
 
+        // Backspace slider
+        if (oldKey != null && oldKey.getCode() == Constants.CODE_DELETE
+                && Settings.getInstance().getCurrent().mBackspaceTrackpadEnabled) {
+            int steps = (x - mStartX) / sPointerWordStep;
+            if (steps != 0
+                    && mStartTime + Settings.getInstance().getCurrent().mKeyLongpressTimeout
+                    < System.currentTimeMillis()) {
+                mSlidOnBackspace = true;
+                mStartX += steps * sPointerWordStep;
+                sListener.onBackspaceSlide(steps);
+            }
+            return;
+        }
+
         if (sGestureEnabler.shouldHandleGesture()) {
             // Register move event on gesture tracker.
             onGestureMoveEvent(x, y, eventTime, true /* isMajorEvent */, newKey);
@@ -1012,6 +1032,12 @@ private void onUpEventInternal(final int x, final int y, final long eventTime) {
             return;
         }
 
+        if (mSlidOnBackspace) {
+            sListener.onBackspaceSlideFinished();
+            mSlidOnBackspace = false;
+            return;
+        }
+
         if (sInGesture) {
             if (currentKey != null) {
                 callListenerOnRelease(currentKey, currentKey.getCode(), true /* withSliding */);
@@ -1057,6 +1083,9 @@ public void onLongPressed() {
         if (mSlidOnSpaceBar) {
             return;
         }
+        if (mSlidOnBackspace) {
+            return;
+        }
         final Key key = getKey();
         if (key == null) {
             return;

java/src/com/android/inputmethod/latin/LatinIME.java

@@ -106,6 +106,7 @@
 
 import java.io.FileDescriptor;
 import java.io.PrintWriter;
+import java.text.BreakIterator;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
@@ -159,6 +160,8 @@ public class LatinIME extends InputMethodService implements KeyboardActionListen
     // If it turns out we need several, it will get grown seamlessly.
     final SparseArray<HardwareEventDecoder> mHardwareEventDecoders = new SparseArray<>(1);
 
+    BreakIterator mBreakWordIterator = BreakIterator.getWordInstance();
+
     // TODO: Move these {@link View}s to {@link KeyboardSwitcher}.
     private View mInputView;
     private InsetsUpdater mInsetsUpdater;
@@ -746,6 +749,19 @@ private void resetDictionaryFacilitator(final Locale locale) {
         mInputLogic.mSuggest.setPlausibilityThreshold(settingsValues.mPlausibilityThreshold);
     }
 
+    /**
+     * Reset the BreakIterator for the given locale.
+     *
+     * @param locale the locale
+     */
+    private void resetBreakIterator(final Locale locale) {
+        if (locale == null) {
+            mBreakWordIterator = BreakIterator.getWordInstance(Locale.US);
+        } else {
+            mBreakWordIterator = BreakIterator.getWordInstance(locale);
+        }
+    }
+
     /**
      * Reset suggest by loading the main dictionary of the current locale.
      */
@@ -1441,6 +1457,64 @@ public void onMovePointer(int steps) {
         getCurrentInputConnection().setSelection(newPosition, newPosition);
     }
 
+    @Override
+    public void onBackspaceSlide(int steps) {
+        int delta = 0;
+        if (steps < 0) {
+            CharSequence text =
+                    getCurrentInputConnection().getTextBeforeCursor(MAX_SPACESLIDE_CHARS, 0);
+            if (text == null || text.length() == 0) {
+                return;
+            }
+            mBreakWordIterator.setText(text.toString());
+            mBreakWordIterator.last();
+            delta = text.length();
+            while (steps < 0) {
+                int start = mBreakWordIterator.previous();
+                if (start == BreakIterator.DONE) {
+                    break;
+                }
+                delta = start;
+                steps++;
+            }
+            delta -= text.length();
+        } else if (steps > 0) {
+            CharSequence text = getCurrentInputConnection().getSelectedText(0);
+            if (text == null || text.length() == 0) {
+                return;
+            }
+            mBreakWordIterator.setText(text.toString());
+            mBreakWordIterator.first();
+            while (steps > 0) {
+                int end = mBreakWordIterator.next();
+                if (end == BreakIterator.DONE) {
+                    break;
+                }
+                delta = end;
+                steps--;
+            }
+        } else {
+            return;
+        }
+
+        // We only extend the start of the selection, never going past the original selection end.
+        int newStart = mInputLogic.mConnection.getExpectedSelectionStart() + delta;
+        int newEnd = mInputLogic.mConnection.getExpectedSelectionEnd();
+        if (newStart > newEnd) {
+            newStart = newEnd;
+        }
+        getCurrentInputConnection().setSelection(newStart, newEnd);
+    }
+
+    @Override
+    public void onBackspaceSlideFinished() {
+        final int start = mInputLogic.mConnection.getExpectedSelectionStart();
+        final int end = mInputLogic.mConnection.getExpectedSelectionEnd();
+        if (start != end) {
+            getCurrentInputConnection().commitText("", 1);
+        }
+    }
+
     private boolean isShowingOptionDialog() {
         return mOptionsDialog != null && mOptionsDialog.isShowing();
     }

java/src/com/android/inputmethod/latin/settings/Settings.java

@@ -124,6 +124,9 @@ public final class Settings implements SharedPreferences.OnSharedPreferenceChang
     // Space bar trackpad slider
     public static final String PREF_SPACE_TRACKPAD = "pref_space_trackpad";
 
+    // Backspace key trackpad slider
+    public static final String PREF_BACKSPACE_TRACKPAD = "pref_backspace_trackpad";
+
     // Emoji
     public static final String PREF_EMOJI_RECENT_KEYS = "emoji_recent_keys";
     public static final String PREF_EMOJI_CATEGORY_LAST_TYPED_ID = "emoji_category_last_typed_id";
@@ -372,6 +375,10 @@ public static boolean readSpaceTrackpadEnabled(final SharedPreferences prefs) {
         return prefs.getBoolean(PREF_SPACE_TRACKPAD, true);
     }
 
+    public static boolean readBackspaceTrackpadEnabled(final SharedPreferences prefs) {
+        return prefs.getBoolean(PREF_BACKSPACE_TRACKPAD, true);
+    }
+
     public static boolean readUseFullscreenMode(final Resources res) {
         return res.getBoolean(R.bool.config_use_fullscreen_mode);
     }

java/src/com/android/inputmethod/latin/settings/SettingsValues.java

@@ -77,6 +77,7 @@ public class SettingsValues {
     public final boolean mUseDoubleSpacePeriod;
     public final boolean mBlockPotentiallyOffensive;
     public final boolean mSpaceTrackpadEnabled;
+    public final boolean mBackspaceTrackpadEnabled;
     // Use bigrams to predict the next word when there is no input for it yet
     public final boolean mBigramPredictionEnabled;
     public final boolean mGestureInputEnabled;
@@ -228,6 +229,7 @@ public SettingsValues(final Context context, final SharedPreferences prefs, fina
                     .execute(mInputAttributes.mTargetApplicationPackageName);
         }
         mSpaceTrackpadEnabled = Settings.readSpaceTrackpadEnabled(prefs);
+        mBackspaceTrackpadEnabled = Settings.readBackspaceTrackpadEnabled(prefs);
     }
 
     public boolean isMetricsLoggingEnabled() {