diff --git a/native/jni/src/geometry_utils.h b/native/jni/src/geometry_utils.h
new file mode 100644
index 0000000..ada889e
--- /dev/null
+++ b/native/jni/src/geometry_utils.h
@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_INCREMENTAL_GEOMETRY_UTILS_H
+#define LATINIME_INCREMENTAL_GEOMETRY_UTILS_H
+
+#include <cmath>
+
+#define MAX_DISTANCE 10000000
+#define KEY_NUM 27
+#define SPACE_KEY 26
+#define MAX_PATHS 2
+
+#define DEBUG_DECODER false
+
+namespace latinime {
+
+static inline float sqr(float x) {
+    return x * x;
+}
+
+static inline float getNormalizedSqrDistance(int x1, int y1, int x2, int y2, int scale) {
+    return sqr((x1 - x2) * 1.0 / scale) + sqr((y1 - y2) * 1.0 / scale);
+}
+
+static inline int getDistance(int x1, int y1, int x2, int y2) {
+    return (int) sqrt(sqr(x2 - x1) + sqr(y2 - y1));
+}
+
+static inline float getDistanceSq(float x1, float y1, float x2, float y2) {
+    return sqr(x2 - x1) + sqr(y2 - y1);
+}
+
+static inline float getAngle(int x1, int y1, int x2, int y2) {
+    float dx = x1 - x2;
+    float dy = y1 - y2;
+    if (dx == 0 && dy == 0)
+        return 0;
+    return atan2(dy, dx);
+}
+
+static inline float angleDiff(float a1, float a2) {
+    float diff = a1 - a2;
+    if (diff < 0) {
+        diff = -diff;
+    }
+    if (diff > M_PI) {
+        return 2 * M_PI - diff;
+    }
+    return diff;
+}
+
+//static float pointToLineDistanceSq(float x, float y, float x1, float y1, float x2, float y2) {
+//    float A = x - x1;
+//    float B = y - y1;
+//    float C = x2 - x1;
+//    float D = y2 - y1;
+//    return abs(A * D - C * B) / sqrt(C * C + D * D);
+//}
+
+static inline float pointToLineSegDistanceSq(
+        float x, float y, float x1, float y1, float x2, float y2) {
+    float ray1x = x - x1;
+    float ray1y = y - y1;
+    float ray2x = x2 - x1;
+    float ray2y = y2 - y1;
+
+    float dotProduct = ray1x * ray2x + ray1y * ray2y;
+    float lineLengthSq = ray2x * ray2x + ray2y * ray2y;
+    float projectionLengthSq = dotProduct / lineLengthSq;
+
+    float projectionX, projectionY;
+    if (projectionLengthSq < 0) {
+        projectionX = x1;
+        projectionY = y1;
+    } else if (projectionLengthSq > 1) {
+        projectionX = x2;
+        projectionY = y2;
+    } else {
+        projectionX = x1 + projectionLengthSq * ray2x;
+        projectionY = y1 + projectionLengthSq * ray2y;
+    }
+
+    float dist = getDistanceSq(x, y, projectionX, projectionY);
+    return dist;
+}
+} // namespace latinime
+#endif // LATINIME_INCREMENTAL_GEOMETRY_UTILS_H
diff --git a/native/jni/src/proximity_info.cpp b/native/jni/src/proximity_info.cpp
index 2564c8a..2633913 100644
--- a/native/jni/src/proximity_info.cpp
+++ b/native/jni/src/proximity_info.cpp
@@ -23,6 +23,7 @@
 #include "additional_proximity_chars.h"
 #include "char_utils.h"
 #include "defines.h"
+#include "geometry_utils.h"
 #include "jni.h"
 #include "proximity_info.h"
 
@@ -55,6 +56,7 @@
         const jfloatArray sweetSpotRadii)
         : MAX_PROXIMITY_CHARS_SIZE(maxProximityCharsSize), KEYBOARD_WIDTH(keyboardWidth),
           KEYBOARD_HEIGHT(keyboardHeight), GRID_WIDTH(gridWidth), GRID_HEIGHT(gridHeight),
+          MOST_COMMON_KEY_WIDTH(mostCommonKeyWidth),
           MOST_COMMON_KEY_WIDTH_SQUARE(mostCommonKeyWidth * mostCommonKeyWidth),
           CELL_WIDTH((keyboardWidth + gridWidth - 1) / gridWidth),
           CELL_HEIGHT((keyboardHeight + gridHeight - 1) / gridHeight),
@@ -84,6 +86,7 @@
     safeGetOrFillZeroFloatArrayRegion(env, sweetSpotCenterYs, KEY_COUNT, mSweetSpotCenterYs);
     safeGetOrFillZeroFloatArrayRegion(env, sweetSpotRadii, KEY_COUNT, mSweetSpotRadii);
     initializeCodeToKeyIndex();
+    initializeG();
 }
 
 // Build the reversed look up table from the char code to the index in mKeyXCoordinates,
@@ -222,6 +225,67 @@
     return mCodeToKeyIndex[baseLowerC];
 }
 
+int ProximityInfo::getKeyCode(const int keyIndex) const {
+    if (keyIndex < 0 || keyIndex >= KEY_COUNT) {
+        return NOT_AN_INDEX;
+    }
+    return mKeyToCodeIndexG[keyIndex];
+}
+
+void ProximityInfo::initializeG() {
+    for (int i = 0; i < KEY_COUNT; ++i) {
+        const int code = mKeyCharCodes[i];
+        const int lowerCode = toBaseLowerCase(code);
+        mCenterXsG[i] = mKeyXCoordinates[i] + mKeyWidths[i] / 2;
+        mCenterYsG[i] = mKeyYCoordinates[i] + mKeyHeights[i] / 2;
+        if (code != lowerCode && lowerCode >= 0 && lowerCode <= MAX_CHAR_CODE) {
+            mCodeToKeyIndex[lowerCode] = i;
+            mKeyToCodeIndexG[i] = lowerCode;
+        } else {
+            mKeyToCodeIndexG[i] = code;
+        }
+    }
+    for (int i = 0; i < KEY_COUNT; i++) {
+        mKeyKeyDistancesG[i][i] = 0;
+        for (int j = i + 1; j < KEY_COUNT; j++) {
+            mKeyKeyDistancesG[i][j] = getDistance(
+                    mCenterXsG[i], mCenterYsG[i], mCenterXsG[j], mCenterYsG[j]);
+            mKeyKeyDistancesG[j][i] = mKeyKeyDistancesG[i][j];
+        }
+    }
+}
+
+float ProximityInfo::getKeyCenterXOfCharG(int charCode) const {
+    return getKeyCenterXOfIdG(getKeyIndex(charCode));
+}
+
+float ProximityInfo::getKeyCenterYOfCharG(int charCode) const {
+    return getKeyCenterYOfIdG(getKeyIndex(charCode));
+}
+
+float ProximityInfo::getKeyCenterXOfIdG(int keyId) const {
+    if (keyId >= 0) {
+        return mCenterXsG[keyId];
+    }
+    return 0;
+}
+
+float ProximityInfo::getKeyCenterYOfIdG(int keyId) const {
+    if (keyId >= 0) {
+        return mCenterYsG[keyId];
+    }
+    return 0;
+}
+
+int ProximityInfo::getKeyKeyDistanceG(int key0, int key1) const {
+    const int keyId0 = getKeyIndex(key0);
+    const int keyId1 = getKeyIndex(key1);
+    if (keyId0 >= 0 && keyId1 >= 0) {
+        return mKeyKeyDistancesG[keyId0][keyId1];
+    }
+    return 0;
+}
+
 // TODO: [Staging] Optimize
 void ProximityInfo::getCenters(int *centerXs, int *centerYs, int *codeToKeyIndex,
         int *keyToCodeIndex, int *keyCount, int *keyWidth) const {
diff --git a/native/jni/src/proximity_info.h b/native/jni/src/proximity_info.h
index d7e24c5..58f2d75 100644
--- a/native/jni/src/proximity_info.h
+++ b/native/jni/src/proximity_info.h
@@ -49,6 +49,7 @@
         return left < right && top < bottom && x >= left && x < right && y >= top && y < bottom;
     }
     int getKeyIndex(const int c) const;
+    int getKeyCode(const int keyIndex) const;
     bool hasSweetSpotData(const int keyIndex) const {
         // When there are no calibration data for a key,
         // the radius of the key is assigned to zero.
@@ -70,6 +71,10 @@
         return HAS_TOUCH_POSITION_CORRECTION_DATA;
     }
 
+    int getMostCommonKeyWidth() const {
+        return MOST_COMMON_KEY_WIDTH;
+    }
+
     int getMostCommonKeyWidthSquare() const {
         return MOST_COMMON_KEY_WIDTH_SQUARE;
     }
@@ -98,6 +103,12 @@
         return GRID_HEIGHT;
     }
 
+    float getKeyCenterXOfCharG(int charCode) const;
+    float getKeyCenterYOfCharG(int charCode) const;
+    float getKeyCenterXOfIdG(int keyId) const;
+    float getKeyCenterYOfIdG(int keyId) const;
+    int getKeyKeyDistanceG(int key0, int key1) const;
+
     // Returns the keyboard key-center information.
     void getCenters(int *centersX, int *centersY, int *codeToKeyIndex, int *keyToCodeIndex,
             int *keyCount, int *keyWidth) const;
@@ -113,6 +124,7 @@
 
     int getStartIndexFromCoordinates(const int x, const int y) const;
     void initializeCodeToKeyIndex();
+    void initializeG();
     float calculateNormalizedSquaredDistance(const int keyIndex, const int inputIndex) const;
     float calculateSquaredDistanceFromSweetSpotCenter(
             const int keyIndex, const int inputIndex) const;
@@ -123,6 +135,7 @@
     const int KEYBOARD_HEIGHT;
     const int GRID_WIDTH;
     const int GRID_HEIGHT;
+    const int MOST_COMMON_KEY_WIDTH;
     const int MOST_COMMON_KEY_WIDTH_SQUARE;
     const int CELL_WIDTH;
     const int CELL_HEIGHT;
@@ -139,6 +152,11 @@
     float mSweetSpotCenterYs[MAX_KEY_COUNT_IN_A_KEYBOARD];
     float mSweetSpotRadii[MAX_KEY_COUNT_IN_A_KEYBOARD];
     int mCodeToKeyIndex[MAX_CHAR_CODE + 1];
+
+    int mKeyToCodeIndexG[MAX_KEY_COUNT_IN_A_KEYBOARD];
+    int mCenterXsG[MAX_KEY_COUNT_IN_A_KEYBOARD];
+    int mCenterYsG[MAX_KEY_COUNT_IN_A_KEYBOARD];
+    int mKeyKeyDistancesG[MAX_KEY_COUNT_IN_A_KEYBOARD][MAX_KEY_COUNT_IN_A_KEYBOARD];
     // TODO: move to correction.h
 };
 } // namespace latinime