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      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_SUGGEST_UTILS_H
     18 #define LATINIME_SUGGEST_UTILS_H
     19 
     20 #include "defines.h"
     21 #include "proximity_info_params.h"
     22 
     23 namespace latinime {
     24 class SuggestUtils {
     25  public:
     26     // TODO: (OLD) Remove
     27     static float getLengthScalingFactor(const float normalizedSquaredDistance) {
     28         // Promote or demote the score according to the distance from the sweet spot
     29         static const float A = ZERO_DISTANCE_PROMOTION_RATE / 100.0f;
     30         static const float B = 1.0f;
     31         static const float C = 0.5f;
     32         static const float MIN = 0.3f;
     33         static const float R1 = NEUTRAL_SCORE_SQUARED_RADIUS;
     34         static const float R2 = HALF_SCORE_SQUARED_RADIUS;
     35         const float x = normalizedSquaredDistance / static_cast<float>(
     36                 ProximityInfoParams::NORMALIZED_SQUARED_DISTANCE_SCALING_FACTOR);
     37         const float factor = max((x < R1)
     38                 ? (A * (R1 - x) + B * x) / R1
     39                 : (B * (R2 - x) + C * (x - R1)) / (R2 - R1), MIN);
     40         // factor is a piecewise linear function like:
     41         // A -_                  .
     42         //     ^-_               .
     43         // B      \              .
     44         //         \_            .
     45         // C         ------------.
     46         //                       .
     47         // 0   R1 R2             .
     48         return factor;
     49     }
     50 
     51     static float getSweetSpotFactor(const bool isTouchPositionCorrectionEnabled,
     52             const float normalizedSquaredDistance) {
     53         // Promote or demote the score according to the distance from the sweet spot
     54         static const float A = 0.0f;
     55         static const float B = 0.24f;
     56         static const float C = 1.20f;
     57         static const float R0 = 0.0f;
     58         static const float R1 = 0.25f; // Sweet spot
     59         static const float R2 = 1.0f;
     60         const float x = normalizedSquaredDistance;
     61         if (!isTouchPositionCorrectionEnabled) {
     62             return min(C, x);
     63         }
     64 
     65         // factor is a piecewise linear function like:
     66         // C        -------------.
     67         //         /             .
     68         // B      /              .
     69         //      -/               .
     70         // A _-^                 .
     71         //                       .
     72         //   R0 R1 R2            .
     73 
     74         if (x < R0) {
     75             return A;
     76         } else if (x < R1) {
     77             return (A * (R1 - x) + B * (x - R0)) / (R1 - R0);
     78         } else if (x < R2) {
     79             return (B * (R2 - x) + C * (x - R1)) / (R2 - R1);
     80         } else {
     81             return C;
     82         }
     83     }
     84  private:
     85     DISALLOW_IMPLICIT_CONSTRUCTORS(SuggestUtils);
     86 };
     87 } // namespace latinime
     88 #endif // LATINIME_SUGGEST_UTILS_H
     89