1 /*
2  * Copyright (C) 2013 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef LATINIME_TOUCH_POSITION_CORRECTION_UTILS_H
18 #define LATINIME_TOUCH_POSITION_CORRECTION_UTILS_H
19 
20 #include <algorithm>
21 
22 #include "defines.h"
23 #include "suggest/core/layout/proximity_info_params.h"
24 
25 namespace latinime {
26 class TouchPositionCorrectionUtils {
27  public:
getSweetSpotFactor(const bool isTouchPositionCorrectionEnabled,const float normalizedSquaredDistance)28     static float getSweetSpotFactor(const bool isTouchPositionCorrectionEnabled,
29             const float normalizedSquaredDistance) {
30         // Promote or demote the score according to the distance from the sweet spot
31         static const float A = 0.0f;
32         static const float B = 0.24f;
33         static const float C = 1.20f;
34         static const float R0 = 0.0f;
35         static const float R1 = 0.25f; // Sweet spot
36         static const float R2 = 1.0f;
37         const float x = normalizedSquaredDistance;
38         if (!isTouchPositionCorrectionEnabled) {
39             return std::min(C, x);
40         }
41 
42         // factor is a piecewise linear function like:
43         // C        -------------.
44         //         /             .
45         // B      /              .
46         //      -/               .
47         // A _-^                 .
48         //                       .
49         //   R0 R1 R2            .
50 
51         if (x < R0) {
52             return A;
53         } else if (x < R1) {
54             return (A * (R1 - x) + B * (x - R0)) / (R1 - R0);
55         } else if (x < R2) {
56             return (B * (R2 - x) + C * (x - R1)) / (R2 - R1);
57         } else {
58             return C;
59         }
60     }
61  private:
62     DISALLOW_IMPLICIT_CONSTRUCTORS(TouchPositionCorrectionUtils);
63 };
64 } // namespace latinime
65 #endif // LATINIME_TOUCH_POSITION_CORRECTION_UTILS_H
66