Using distance to the edge of key as proximity detection

Because there may be very long key, such as space bar on tablet, we
should not use the distance between the touch point and the center of
key as proximity detection.  Instead of that, this change uses the
distance between the point and the nearest edge of key as proximity
detection.

Also this change fixes the bug that space key (code 32) was not
counted in proximity detection.

Bug: 3164020
Bug: 3168138
Change-Id: I687f1ce94a8e944c3f6eea0fe00e18ed6e68e278

1 files changed, 34 insertions, 18 deletions

diff --git a/java/src/com/android/inputmethod/latin/BaseKeyboardView.java b/java/src/com/android/inputmethod/latin/BaseKeyboardView.java
index 4ba6fbddc..070d031e7 100644
--- a/java/src/com/android/inputmethod/latin/BaseKeyboardView.java
+++ b/java/src/com/android/inputmethod/latin/BaseKeyboardView.java
@@ -71,6 +71,7 @@ import java.util.WeakHashMap;
 public class BaseKeyboardView extends View implements PointerTracker.UIProxy {
     private static final String TAG = "BaseKeyboardView";
     private static final boolean DEBUG = false;
+    private static final boolean DEBUG_KEYBOARD_GRID = false;
 
     public static final int NOT_A_TOUCH_COORDINATE = -1;
 
@@ -183,8 +184,6 @@ public class BaseKeyboardView extends View implements PointerTracker.UIProxy {
     // Main keyboard
     private BaseKeyboard mKeyboard;
     private Key[] mKeys;
-    // TODO this attribute should be gotten from Keyboard.
-    private int mKeyboardVerticalGap;
 
     // Key preview popup
     private boolean mInForeground;
@@ -609,7 +608,6 @@ public class BaseKeyboardView extends View implements PointerTracker.UIProxy {
         LatinImeLogger.onSetKeyboard(keyboard);
         mKeys = mKeyDetector.setKeyboard(keyboard, -getPaddingLeft(),
                 -getPaddingTop() + mVerticalCorrection);
-        mKeyboardVerticalGap = (int)getResources().getDimension(R.dimen.key_bottom_gap);
         for (PointerTracker tracker : mPointerTrackers) {
             tracker.setKeyboard(keyboard, mKeys, mKeyHysteresisDistance);
         }
@@ -617,7 +615,7 @@ public class BaseKeyboardView extends View implements PointerTracker.UIProxy {
         // Hint to reallocate the buffer if the size changed
         mKeyboardChanged = true;
         invalidateAllKeys();
-        computeProximityThreshold(keyboard);
+        computeProximityThreshold(keyboard, mKeys);
         mMiniKeyboardCache.clear();
     }
 
@@ -713,23 +711,27 @@ public class BaseKeyboardView extends View implements PointerTracker.UIProxy {
     }
 
     /**
-     * Compute the average distance between adjacent keys (horizontally and vertically)
-     * and square it to get the proximity threshold. We use a square here and in computing
-     * the touch distance from a key's center to avoid taking a square root.
+     * Compute the most common key width and use it as proximity key detection threshold.
      * @param keyboard
+     * @param keys
      */
-    private void computeProximityThreshold(BaseKeyboard keyboard) {
-        if (keyboard == null) return;
-        final Key[] keys = mKeys;
-        if (keys == null) return;
-        int length = keys.length;
-        int dimensionSum = 0;
-        for (int i = 0; i < length; i++) {
-            Key key = keys[i];
-            dimensionSum += Math.min(key.width, key.height + mKeyboardVerticalGap) + key.gap;
+    private void computeProximityThreshold(BaseKeyboard keyboard, Key[] keys) {
+        if (keyboard == null || keys == null || keys.length == 0) return;
+        final HashMap<Integer, Integer> histogram = new HashMap<Integer, Integer>();
+        int maxCount = 0;
+        int mostCommonWidth = 0;
+        for (Key key : keys) {
+            final Integer width = key.width + key.gap;
+            Integer count = histogram.get(width);
+            if (count == null)
+                count = 0;
+            histogram.put(width, ++count);
+            if (count > maxCount) {
+                maxCount = count;
+                mostCommonWidth = width;
+            }
         }
-        if (dimensionSum < 0 || length == 0) return;
-        mKeyDetector.setProximityThreshold((int) (dimensionSum * 1.4f / length));
+        mKeyDetector.setProximityThreshold(mostCommonWidth);
     }
 
     @Override
@@ -868,6 +870,20 @@ public class BaseKeyboardView extends View implements PointerTracker.UIProxy {
             }
             canvas.translate(-key.x - kbdPaddingLeft, -key.y - kbdPaddingTop);
         }
+
+        if (DEBUG_KEYBOARD_GRID) {
+            Paint p = new Paint();
+            p.setStyle(Paint.Style.STROKE);
+            p.setStrokeWidth(1.0f);
+            p.setColor(0x800000c0);
+            int cw = (mKeyboard.getMinWidth() + mKeyboard.GRID_WIDTH - 1) / mKeyboard.GRID_WIDTH;
+            int ch = (mKeyboard.getHeight() + mKeyboard.GRID_HEIGHT - 1) / mKeyboard.GRID_HEIGHT;
+            for (int i = 0; i <= mKeyboard.GRID_WIDTH; i++)
+                canvas.drawLine(i * cw, 0, i * cw, ch * mKeyboard.GRID_HEIGHT, p);
+            for (int i = 0; i <= mKeyboard.GRID_HEIGHT; i++)
+                canvas.drawLine(0, i * ch, cw * mKeyboard.GRID_WIDTH, i * ch, p);
+        }
+
         mInvalidatedKey = null;
         // Overlay a dark rectangle to dim the keyboard
         if (mMiniKeyboard != null) {