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, 23 insertions, 23 deletions

diff --git a/java/src/com/android/inputmethod/latin/BaseKeyboard.java b/java/src/com/android/inputmethod/latin/BaseKeyboard.java
index 266300eb3..e5b2756d4 100644
--- a/java/src/com/android/inputmethod/latin/BaseKeyboard.java
+++ b/java/src/com/android/inputmethod/latin/BaseKeyboard.java
@@ -24,7 +24,6 @@ import android.content.res.TypedArray;
 import android.content.res.XmlResourceParser;
 import android.graphics.drawable.Drawable;
 import android.text.TextUtils;
-import android.util.DisplayMetrics;
 import android.util.Log;
 import android.util.TypedValue;
 import android.util.Xml;
@@ -109,15 +108,16 @@ public class BaseKeyboard {
 
     // Variables for pre-computing nearest keys.
 
-    private final int GRID_WIDTH;
-    private final int GRID_HEIGHT;
+    public final int GRID_WIDTH;
+    public final int GRID_HEIGHT;
     private final int GRID_SIZE;
     private int mCellWidth;
     private int mCellHeight;
     private int[][] mGridNeighbors;
     private int mProximityThreshold;
+    private static int[] EMPTY_INT_ARRAY = new int[0];
     /** Number of key widths from current touch point to search for nearest keys. */
-    private static float SEARCH_DISTANCE = 1.8f;
+    private static float SEARCH_DISTANCE = 1.2f;
 
     /**
      * Container for keys in the keyboard. All keys in a row are at the same Y-coordinate.
@@ -402,18 +402,21 @@ public class BaseKeyboard {
         }
 
         /**
-         * Returns the square of the distance between the center of the key and the given point.
+         * Returns the square of the distance to the nearest edge of the key and the given point.
          * @param x the x-coordinate of the point
          * @param y the y-coordinate of the point
-         * @return the square of the distance of the point from the center of the key
+         * @return the square of the distance of the point from the nearest edge of the key
          */
-        public int squaredDistanceFrom(int x, int y) {
-            // We should count vertical gap between rows to calculate the center of this Key.
-            // TODO: We should re-think how we define the center of the key.
-            final int verticalGap = keyboard.getVerticalGap();
-            int xDist = this.x + width / 2 - x;
-            int yDist = this.y + (height + verticalGap) / 2 - y;
-            return xDist * xDist + yDist * yDist;
+        public int squaredDistanceToEdge(int x, int y) {
+            final int left = this.x;
+            final int right = left + this.width;
+            final int top = this.y;
+            final int bottom = top + this.height;
+            final int edgeX = x < left ? left : (x > right ? right : x);
+            final int edgeY = y < top ? top : (y > bottom ? bottom : y);
+            final int dx = x - edgeX;
+            final int dy = y - edgeY;
+            return dx * dx + dy * dy;
         }
 
         /**
@@ -633,24 +636,21 @@ public class BaseKeyboard {
         mCellWidth = (getMinWidth() + GRID_WIDTH - 1) / GRID_WIDTH;
         mCellHeight = (getHeight() + GRID_HEIGHT - 1) / GRID_HEIGHT;
         mGridNeighbors = new int[GRID_SIZE][];
-        int[] indices = new int[mKeys.size()];
+        final int[] indices = new int[mKeys.size()];
         final int gridWidth = GRID_WIDTH * mCellWidth;
         final int gridHeight = GRID_HEIGHT * mCellHeight;
+        final int threshold = mProximityThreshold;
         for (int x = 0; x < gridWidth; x += mCellWidth) {
             for (int y = 0; y < gridHeight; y += mCellHeight) {
+                final int centerX = x + mCellWidth / 2;
+                final int centerY = y + mCellHeight / 2;
                 int count = 0;
                 for (int i = 0; i < mKeys.size(); i++) {
                     final Key key = mKeys.get(i);
-                    final int threshold = mProximityThreshold;
-                    if (key.squaredDistanceFrom(x, y) < threshold ||
-                            key.squaredDistanceFrom(x + mCellWidth - 1, y) < threshold ||
-                            key.squaredDistanceFrom(x + mCellWidth - 1, y + mCellHeight - 1)
-                                < threshold ||
-                            key.squaredDistanceFrom(x, y + mCellHeight - 1) < threshold) {
+                    if (key.squaredDistanceToEdge(centerX, centerY) < threshold)
                         indices[count++] = i;
-                    }
                 }
-                int [] cell = new int[count];
+                final int[] cell = new int[count];
                 System.arraycopy(indices, 0, cell, 0, count);
                 mGridNeighbors[(y / mCellHeight) * GRID_WIDTH + (x / mCellWidth)] = cell;
             }
@@ -672,7 +672,7 @@ public class BaseKeyboard {
                 return mGridNeighbors[index];
             }
         }
-        return new int[0];
+        return EMPTY_INT_ARRAY;
     }
 
     // TODO should be private