Add charCount heuristic to TextView textDirection

- threshold set to 60% (using a constant)
- fix also one issue during layout direction resolution (parent could be null so delay resolution
up to when parent is no more null)

Change-Id: I65f24a297aac6bc0d5d482ee31b55db0b201e5bf

3 files changed, 64 insertions, 3 deletions

diff --git a/core/java/android/view/View.java b/core/java/android/view/View.java
index bf7f359303ef..8a72c4a14c66 100644
--- a/core/java/android/view/View.java
+++ b/core/java/android/view/View.java
@@ -2523,18 +2523,26 @@ public class View implements Drawable.Callback2, KeyEvent.Callback, Accessibilit
     public static final int TEXT_DIRECTION_ANY_RTL = 2;
 
     /**
+     * Text direction is the same as the one held by a 60% majority of the characters. If there is
+     * no majority then the paragraph direction is the resolved layout direction of the View.
+     *
+     * @hide
+     */
+    public static final int TEXT_DIRECTION_CHAR_COUNT = 3;
+
+    /**
      * Text direction is forced to LTR.
      *
      * @hide
      */
-    public static final int TEXT_DIRECTION_LTR = 3;
+    public static final int TEXT_DIRECTION_LTR = 4;
 
     /**
      * Text direction is forced to RTL.
      *
      * @hide
      */
-    public static final int TEXT_DIRECTION_RTL = 4;
+    public static final int TEXT_DIRECTION_RTL = 5;
 
     /**
      * Default text direction is inherited
@@ -2542,6 +2550,11 @@ public class View implements Drawable.Callback2, KeyEvent.Callback, Accessibilit
     protected static int DEFAULT_TEXT_DIRECTION = TEXT_DIRECTION_INHERIT;
 
     /**
+     * Default threshold for "char count" heuristic.
+     */
+    protected static float DEFAULT_TEXT_DIRECTION_CHAR_COUNT_THRESHOLD = 0.6f;
+
+    /**
      * The text direction that has been defined by {@link #setTextDirection(int)}.
      *
      * {@hide}
@@ -2551,6 +2564,7 @@ public class View implements Drawable.Callback2, KeyEvent.Callback, Accessibilit
             @ViewDebug.IntToString(from = TEXT_DIRECTION_INHERIT, to = "INHERIT"),
             @ViewDebug.IntToString(from = TEXT_DIRECTION_FIRST_STRONG, to = "FIRST_STRONG"),
             @ViewDebug.IntToString(from = TEXT_DIRECTION_ANY_RTL, to = "ANY_RTL"),
+            @ViewDebug.IntToString(from = TEXT_DIRECTION_CHAR_COUNT, to = "CHAR_COUNT"),
             @ViewDebug.IntToString(from = TEXT_DIRECTION_LTR, to = "LTR"),
             @ViewDebug.IntToString(from = TEXT_DIRECTION_RTL, to = "RTL")
     })
@@ -11963,7 +11977,7 @@ public class View implements Drawable.Callback2, KeyEvent.Callback, Accessibilit
         mPrivateFlags |= FORCE_LAYOUT;
         mPrivateFlags |= INVALIDATED;
 
-        if (mLayoutParams != null) {
+        if (mLayoutParams != null && mParent != null) {
             mLayoutParams.resolveWithDirection(getResolvedLayoutDirection());
         }
 
@@ -12990,6 +13004,7 @@ public class View implements Drawable.Callback2, KeyEvent.Callback, Accessibilit
      * {@link #TEXT_DIRECTION_INHERIT},
      * {@link #TEXT_DIRECTION_FIRST_STRONG}
      * {@link #TEXT_DIRECTION_ANY_RTL},
+     * {@link #TEXT_DIRECTION_CHAR_COUNT},
      * {@link #TEXT_DIRECTION_LTR},
      * {@link #TEXT_DIRECTION_RTL},
      *
@@ -13007,6 +13022,7 @@ public class View implements Drawable.Callback2, KeyEvent.Callback, Accessibilit
      * {@link #TEXT_DIRECTION_INHERIT},
      * {@link #TEXT_DIRECTION_FIRST_STRONG}
      * {@link #TEXT_DIRECTION_ANY_RTL},
+     * {@link #TEXT_DIRECTION_CHAR_COUNT},
      * {@link #TEXT_DIRECTION_LTR},
      * {@link #TEXT_DIRECTION_RTL},
      *
diff --git a/core/java/android/view/ViewGroup.java b/core/java/android/view/ViewGroup.java
index 2a90ddea3b55..25ca42178417 100644
--- a/core/java/android/view/ViewGroup.java
+++ b/core/java/android/view/ViewGroup.java
@@ -5039,6 +5039,7 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
             // Pass down the hierarchy the following text direction values
             case TEXT_DIRECTION_FIRST_STRONG:
             case TEXT_DIRECTION_ANY_RTL:
+            case TEXT_DIRECTION_CHAR_COUNT:
             case TEXT_DIRECTION_LTR:
             case TEXT_DIRECTION_RTL:
                 resolvedTextDirection = mTextDirection;
diff --git a/core/java/android/widget/TextView.java b/core/java/android/widget/TextView.java
index f79dabd9a808..04b79c5ef8e6 100644
--- a/core/java/android/widget/TextView.java
+++ b/core/java/android/widget/TextView.java
@@ -10039,6 +10039,9 @@ public class TextView extends View implements ViewTreeObserver.OnPreDrawListener
             case TEXT_DIRECTION_ANY_RTL:
                 resolvedTextDirection = getTextDirectionFromAnyRtl(mText);
                 break;
+            case TEXT_DIRECTION_CHAR_COUNT:
+                resolvedTextDirection = getTextDirectionFromCharCount(mText);
+                break;
             case TEXT_DIRECTION_LTR:
                 resolvedTextDirection = TEXT_DIRECTION_LTR;
                 break;
@@ -10072,6 +10075,9 @@ public class TextView extends View implements ViewTreeObserver.OnPreDrawListener
      */
     private static int getTextDirectionFromFirstStrong(final CharSequence cs) {
         final int length = cs.length();
+        if (length == 0) {
+            return TEXT_DIRECTION_UNDEFINED;
+        }
         for(int i = 0; i < length; i++) {
             final char c = cs.charAt(i);
             final byte dir = Character.getDirectionality(c);
@@ -10094,6 +10100,9 @@ public class TextView extends View implements ViewTreeObserver.OnPreDrawListener
      */
     private static int getTextDirectionFromAnyRtl(final CharSequence cs) {
         final int length = cs.length();
+        if (length == 0) {
+            return TEXT_DIRECTION_UNDEFINED;
+        }
         boolean foundStrongLtr = false;
         boolean foundStrongRtl = false;
         for(int i = 0; i < length; i++) {
@@ -10115,6 +10124,41 @@ public class TextView extends View implements ViewTreeObserver.OnPreDrawListener
     }
 
     /**
+     * Get text direction following the "char count" heuristic.
+     *
+     * @param cs the CharSequence used to get the text direction.
+     *
+     * @return {@link #TEXT_DIRECTION_RTL} if direction it RTL, {@link #TEXT_DIRECTION_LTR} if
+     * direction it LTR or {@link #TEXT_DIRECTION_UNDEFINED} if direction cannot be found.
+     */
+    private int getTextDirectionFromCharCount(CharSequence cs) {
+        final int length = cs.length();
+        if (length == 0) {
+            return TEXT_DIRECTION_UNDEFINED;
+        }
+        int countLtr = 0;
+        int countRtl = 0;
+        for(int i = 0; i < length; i++) {
+            final char c = cs.charAt(i);
+            final byte dir = Character.getDirectionality(c);
+            if (isStrongLtrChar(dir)) {
+                countLtr++;
+            } else if (isStrongRtlChar(dir)) {
+                countRtl++;
+            }
+        }
+        final float percentLtr = ((float) countLtr) / (countLtr + countRtl);
+        if (percentLtr > DEFAULT_TEXT_DIRECTION_CHAR_COUNT_THRESHOLD) {
+            return TEXT_DIRECTION_LTR;
+        }
+        final float percentRtl = ((float) countRtl) / (countLtr + countRtl);
+        if (percentRtl > DEFAULT_TEXT_DIRECTION_CHAR_COUNT_THRESHOLD) {
+            return TEXT_DIRECTION_RTL;
+        }
+        return TEXT_DIRECTION_UNDEFINED;
+    }
+
+    /**
      * Return true if the char direction is corresponding to a "strong RTL char" following the
      * Unicode Bidirectional Algorithm (UBA).
      */