Add spellcheck and word suggestion to the prediction service

third_party/prediction/suggest/core/layout/touch_position_correction_utils.h

Index: third_party/prediction/suggest/core/layout/touch_position_correction_utils.h
diff --git a/third_party/prediction/suggest/core/layout/touch_position_correction_utils.h b/third_party/prediction/suggest/core/layout/touch_position_correction_utils.h
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+/*
+ * Copyright (C) 2013 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_TOUCH_POSITION_CORRECTION_UTILS_H
+#define LATINIME_TOUCH_POSITION_CORRECTION_UTILS_H
+
+#include <algorithm>
+
+#include "third_party/prediction/defines.h"
+#include "third_party/prediction/suggest/core/layout/proximity_info_params.h"
+
+namespace latinime {
+class TouchPositionCorrectionUtils {
+ public:
+  static float getSweetSpotFactor(const bool isTouchPositionCorrectionEnabled,
+                                  const float normalizedSquaredDistance) {
+    // Promote or demote the score according to the distance from the sweet spot
+    static const float A = 0.0f;
+    static const float B = 0.24f;
+    static const float C = 1.20f;
+    static const float R0 = 0.0f;
+    static const float R1 = 0.25f;  // Sweet spot
+    static const float R2 = 1.0f;
+    const float x = normalizedSquaredDistance;
+    if (!isTouchPositionCorrectionEnabled) {
+      return std::min(C, x);
+    }
+
+    // factor is a piecewise linear function like:
+    // C        -------------.
+    //         /             .
+    // B      /              .
+    //      -/               .
+    // A _-^                 .
+    //                       .
+    //   R0 R1 R2            .
+
+    if (x < R0) {
+      return A;
+    } else if (x < R1) {
+      return (A * (R1 - x) + B * (x - R0)) / (R1 - R0);
+    } else if (x < R2) {
+      return (B * (R2 - x) + C * (x - R1)) / (R2 - R1);
+    } else {
+      return C;
+    }
+  }
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(TouchPositionCorrectionUtils);
+};
+}  // namespace latinime
+#endif  // LATINIME_TOUCH_POSITION_CORRECTION_UTILS_H