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      1 /*
      2  * Copyright (C) 2016 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 package org.chromium.latency.walt;
     18 
     19 import android.content.Context;
     20 import android.graphics.Canvas;
     21 import android.graphics.Color;
     22 import android.graphics.Paint;
     23 import android.util.AttributeSet;
     24 import android.view.View;
     25 
     26 
     27 
     28 public class TouchCatcherView extends View {
     29 
     30     private Paint linePaint = new Paint();
     31     private WaltDevice waltDevice;
     32     private boolean isAnimated = false;
     33 
     34     private double animationAmplitude = 0.4;  // Fraction of view height
     35     private double lineLength = 0.6;  // Fraction of view width
     36     public final int animationPeriod_us = 1000000;
     37 
     38     public void startAnimation() {
     39         isAnimated = true;
     40         invalidate();
     41     }
     42 
     43     public void stopAnimation() {
     44         isAnimated = false;
     45         invalidate();
     46     }
     47 
     48     public TouchCatcherView(Context context, AttributeSet attrs) {
     49         super(context, attrs);
     50         waltDevice = WaltDevice.getInstance(context);
     51         initialisePaint();
     52     }
     53 
     54     private void initialisePaint() {
     55         float density = getResources().getDisplayMetrics().density;
     56         float lineWidth = 10f * density;
     57         linePaint.setColor(Color.GREEN);
     58         linePaint.setStrokeWidth(lineWidth);
     59     }
     60 
     61     public static double markerPosition(long t_us, int period_us) {
     62         // Normalized time within a period, goes from 0 to 1
     63         double t = (t_us % period_us) / (double) period_us;
     64 
     65         // Triangular wave with unit amplitude
     66         //  1| *               *
     67         //   |   *           *   *
     68         //   0-----*-------*---|---*-----> t
     69         //   |       *   *     1     *
     70         // -1|         *               *
     71         double y_tri = -1 + 4 * Math.abs(t - 0.5);
     72 
     73         // Apply some smoothing to get a feeling of deceleration and acceleration at the edges.
     74         // f(y) = y / {1 + exp(b(|y|-1))/(b-1)}
     75         // This is inspired by Fermi function and adjusted to have continuous derivative at extrema.
     76         // b = beta is a dimensionless smoothing parameter, value selected by experimentation.
     77         // Higher value gives less smoothing = closer to original triangular wave.
     78         double beta = 4;
     79         double y_smooth = y_tri / (1 + Math.exp(beta*(Math.abs(y_tri)-1))/(beta - 1));
     80         return y_smooth;
     81     }
     82 
     83     @Override
     84     protected void onDraw(Canvas canvas) {
     85         super.onDraw(canvas);
     86         if (!isAnimated) return;
     87 
     88         int h = getHeight();
     89         double normPos = markerPosition(waltDevice.clock.micros(), animationPeriod_us);
     90         int pos = (int) (h * (0.5 + animationAmplitude * normPos));
     91         // Log.i("AnimatedView", "Pos is " + pos);
     92         int w = getWidth();
     93 
     94         int lineStart = (int) (w * (1 - lineLength) / 2);
     95         int lineEnd   = (int) (w * (1 + lineLength) / 2);
     96         canvas.drawLine(lineStart, pos, lineEnd, pos, linePaint);
     97 
     98         // Run every frame
     99         invalidate();
    100     }
    101 }
    102