Make a better effort to detect a framework lie.

Bug: 17130496
Change-Id: I1a3631670c152d9b7667c9c4e08e14c48569eef5

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

@@ -926,8 +926,10 @@ public class LatinIME extends InputMethodService implements KeyboardActionListen
                 // mLastSelection{Start,End} are reset later in this method, no need to do it here
                 needToCallLoadKeyboardLater = true;
             } else {
-                // When rotating, initialSelStart and initialSelEnd sometimes are lying. Make a best
+                // When rotating, and when input is starting again in a field from where the focus
-                // effort to work around this bug.
+                // didn't move (the keyboard having been closed with the back key),
+                // initialSelStart and initialSelEnd sometimes are lying. Make a best effort to
+                // work around this bug.
                 mInputLogic.mConnection.tryFixLyingCursorPosition();
                 mHandler.postResumeSuggestions(true /* shouldIncludeResumedWordInSuggestions */,
                         true /* shouldDelay */);

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

@@ -849,8 +849,9 @@ public final class RichInputConnection {
 
     /**
      * Try to get the text from the editor to expose lies the framework may have been
-     * telling us. Concretely, when the device rotates, the frameworks tells us about where the
+     * telling us. Concretely, when the device rotates and when the keyboard reopens in the same
-     * cursor used to be initially in the editor at the time it first received the focus; this
+     * text field after having been closed with the back key, the frameworks tells us about where
+     * the cursor used to be initially in the editor at the time it first received the focus; this
      * may be completely different from the place it is upon rotation. Since we don't have any
      * means to get the real value, try at least to ask the text view for some characters and
      * detect the most damaging cases: when the cursor position is declared to be much smaller
@@ -859,7 +860,20 @@ public final class RichInputConnection {
     public void tryFixLyingCursorPosition() {
         final CharSequence textBeforeCursor = getTextBeforeCursor(
                 Constants.EDITOR_CONTENTS_CACHE_SIZE, 0);
-        if (null == textBeforeCursor) {
+        final CharSequence selectedText = mIC.getSelectedText(0 /* flags */);
+        if (null == textBeforeCursor ||
+                (!TextUtils.isEmpty(selectedText) && mExpectedSelEnd == mExpectedSelStart)) {
+            // If textBeforeCursor is null, we have no idea what kind of text field we have or if
+            // thinking about the "cursor position" actually makes any sense. In this case we
+            // remember a meaningless cursor position. Contrast this with an empty string, which is
+            // valid and should mean the cursor is at the start of the text.
+            // Also, if we expect we don't have a selection but we DO have non-empty selected text,
+            // then the framework lied to us about the cursor position. In this case, we should just
+            // revert to the most basic behavior possible for the next action (backspace in
+            // particular comes to mind), so we remember a meaningless cursor position which should
+            // result in degraded behavior from the next input.
+            // Interestingly, in either case, chances are any action the user takes next will result
+            // in a call to onUpdateSelection, which should set things right.
             mExpectedSelStart = mExpectedSelEnd = Constants.NOT_A_CURSOR_POSITION;
         } else {
             final int textLength = textBeforeCursor.length();

java/src/com/android/inputmethod/latin/inputlogic/InputLogic.java

@@ -1127,19 +1127,21 @@ public final class InputLogic {
                 StatsUtils.onBackspaceSelectedText(numCharsDeleted);
             } else {
                 // There is no selection, just delete one character.
-                if (Constants.NOT_A_CURSOR_POSITION == mConnection.getExpectedSelectionEnd()) {
+                if (inputTransaction.mSettingsValues.isBeforeJellyBean()
-                    // This should never happen.
+                        || inputTransaction.mSettingsValues.mInputAttributes.isTypeNull()
-                    Log.e(TAG, "Backspace when we don't know the selection position");
+                        || Constants.NOT_A_CURSOR_POSITION
-                }
+                                == mConnection.getExpectedSelectionEnd()) {
-                if (inputTransaction.mSettingsValues.isBeforeJellyBean() ||
+                    // There are three possible reasons to send a key event: either the field has
-                        inputTransaction.mSettingsValues.mInputAttributes.isTypeNull()) {
-                    // There are two possible reasons to send a key event: either the field has
                     // type TYPE_NULL, in which case the keyboard should send events, or we are
-                    // running in backward compatibility mode. Before Jelly bean, the keyboard
+                    // running in backward compatibility mode, or we don't know the cursor position.
-                    // would simulate a hardware keyboard event on pressing enter or delete. This
+                    // Before Jelly bean, the keyboard would simulate a hardware keyboard event on
-                    // is bad for many reasons (there are race conditions with commits) but some
+                    // pressing enter or delete. This is bad for many reasons (there are race
-                    // applications are relying on this behavior so we continue to support it for
+                    // conditions with commits) but some applications are relying on this behavior
-                    // older apps, so we retain this behavior if the app has target SDK < JellyBean.
+                    // so we continue to support it for older apps, so we retain this behavior if
+                    // the app has target SDK < JellyBean.
+                    // As for the case where we don't know the cursor position, it can happen
+                    // because of bugs in the framework. But the framework should know, so the next
+                    // best thing is to leave it to whatever it thinks is best.
                     sendDownUpKeyEvent(KeyEvent.KEYCODE_DEL);
                     int totalDeletedLength = 1;
                     if (mDeleteCount > Constants.DELETE_ACCELERATE_AT) {