Introduce EMPTY_PREV_WORDS_INFO and BEGINNING_OF_SENTENCE.

Bug: 14119293
Change-Id: I5020e5f0aa64bc3e97b3a3c2c07a60c8b765ed64

1 files changed, 14 insertions, 7 deletions

diff --git a/java/src/com/android/inputmethod/latin/PrevWordsInfo.java b/java/src/com/android/inputmethod/latin/PrevWordsInfo.java
index 3494d16f7..e44239f1d 100644
--- a/java/src/com/android/inputmethod/latin/PrevWordsInfo.java
+++ b/java/src/com/android/inputmethod/latin/PrevWordsInfo.java
@@ -16,20 +16,27 @@
 
 package com.android.inputmethod.latin;
 
-import android.util.Log;
-
+/**
+ * Class to represent information of previous words. This class is used to add n-gram entries
+ * into binary dictionaries, to get predictions, and to get suggestions.
+ */
 // TODO: Support multiple previous words for n-gram.
 public class PrevWordsInfo {
+    public static final PrevWordsInfo EMPTY_PREV_WORDS_INFO = new PrevWordsInfo(null);
     public static final PrevWordsInfo BEGINNING_OF_SENTENCE = new PrevWordsInfo();
 
-    // The previous word. May be null after resetting and before starting a new composing word, or
-    // when there is no context like at the start of text for example. It can also be set to null
-    // externally when the user enters a separator that does not let bigrams across, like a period
-    // or a comma.
+    // The word immediately before the considered word. null means we don't have any context
+    // including the "beginning of sentence context" - we just don't know what to predict.
+    // An example of that is after a comma.
+    // For simplicity of implementation, this may also be null transiently after the WordComposer
+    // was reset and before starting a new composing word, but we should never be calling
+    // getSuggetions* in this situation.
+    // This is an empty string when mIsBeginningOfSentence is true.
     public final String mPrevWord;
 
     // TODO: Have sentence separator.
-    // Whether the current context is beginning of sentence or not.
+    // Whether the current context is beginning of sentence or not. This is true when composing at
+    // the beginning of an input field or composing a word after a sentence separator.
     public final boolean mIsBeginningOfSentence;
 
     // Beginning of sentence.