/*===== IMPORTANT =====This is sample code demonstrating API, technology or techniques in development.Although this sample code has been reviewed for technical accuracy, it is notfinal. Apple is supplying this information to help you plan for the adoption ofthe technologies and programming interfaces described herein. This informationis subject to change, and software implemented based on this sample code shouldbe tested with final operating system software and final documentation. Newerversions of this sample code may be provided with future seeds of the API ortechnology. For information about updates to this and other developerdocumentation, view the New & Updated sidebars in subsequent documentationseeds.=====================File: GraphView.mAbstract: This class is responsible for updating and drawing the accelerometerhistory of values. The history is a circular buffer implementation, with apointer moving repeatedly through the buffer, resetting to zero each time itreaches the end.Version: 1.6Disclaimer: IMPORTANT:  This Apple software is supplied to you by Apple Inc.("Apple") in consideration of your agreement to the following terms, and youruse, installation, modification or redistribution of this Apple softwareconstitutes acceptance of these terms.  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All Rights Reserved.*/#import "GraphView.h"// Constant for maximum acceleration.#define kMaxAcceleration 3.0// Constant for the high-pass filter.#define kFilteringFactor 0.1// GraphView class implementation.@implementation GraphView// Instruct the compiler to generate accessors for the property, and use the internal variable _filter for storage.@synthesize filteringEnabled=filter;- (void)updateHistoryWithX:(float)x Y:(float)y Z:(float)z {    // If filtering is active, apply a basic high-pass filter to remove the gravity influence from the accelerometer values    if (filter) {        acceleration[0] = x * kFilteringFactor + acceleration[0] * (1.0 - kFilteringFactor);        history[nextIndex][0] = x - acceleration[0];        acceleration[1] = y * kFilteringFactor + acceleration[1] * (1.0 - kFilteringFactor);        history[nextIndex][1] = y - acceleration[1];        acceleration[2] = z * kFilteringFactor + acceleration[2] * (1.0 - kFilteringFactor);        history[nextIndex][2] = z - acceleration[2];    } else {        history[nextIndex][0] = x;        history[nextIndex][1] = y;        history[nextIndex][2] = z;    }    // Advance buffer pointer to next position or reset to zero.    nextIndex = (nextIndex + 1) % kHistorySize;}- (void)setFilteringEnabled:(BOOL)enabled {    filter = enabled;    // Reset the acceleration filter.    acceleration[0] = acceleration[1] = acceleration[2] = 0.0;}- (void)drawHistory:(unsigned)axis fromIndex:(unsigned)index inContext:(CGContextRef)context bounds:(CGRect)bounds {    UIFont *font = [UIFont systemFontOfSize:12];    unsigned i;    float value, temp;        // Draw the background    CGContextSetGrayFillColor(context, 0.6, 1.0);    CGContextFillRect(context, bounds);        // Draw the intermediate lines    CGContextSetGrayStrokeColor(context, 0.5, 1.0);    CGContextBeginPath(context);    for (value = -kMaxAcceleration + 1.0; value <= kMaxAcceleration - 1.0; value += 1.0) {            if (value == 0.0) {            continue;        }        temp = roundf(bounds.origin.y + bounds.size.height / 2 + value / (2 * kMaxAcceleration) * bounds.size.height);        CGContextMoveToPoint(context, bounds.origin.x, temp);        CGContextAddLineToPoint(context, bounds.origin.x + bounds.size.width, temp);    }    CGContextStrokePath(context);        // Draw the center line    CGContextSetGrayStrokeColor(context, 1.0, 1.0);    CGContextBeginPath(context);    temp = roundf(bounds.origin.y + bounds.size.height / 2);    CGContextMoveToPoint(context, bounds.origin.x, temp);    CGContextAddLineToPoint(context, bounds.origin.x + bounds.size.width, temp);    CGContextStrokePath(context);        // Draw the top & bottom lines    CGContextSetGrayStrokeColor(context, 0.25, 1.0);    CGContextBeginPath(context);    CGContextMoveToPoint(context, bounds.origin.x, bounds.origin.y);    CGContextAddLineToPoint(context, bounds.origin.x + bounds.size.width, bounds.origin.y);    CGContextMoveToPoint(context, bounds.origin.x, bounds.origin.y + bounds.size.height);    CGContextAddLineToPoint(context, bounds.origin.x + bounds.size.width, bounds.origin.y + bounds.size.height);    CGContextStrokePath(context);        // Draw the history lines    CGContextSetRGBStrokeColor(context, (axis == 0 ? 1.0 : 0.0), (axis == 1 ? 1.0 : 0.0), (axis == 2 ? 1.0 : 0.0), 1.0);    CGContextBeginPath(context);    for (i = 0; i < kHistorySize; ++i) {        // NOTE: We need to draw upside-down as UIView referential has the Y axis going down        value = history[(index + i) % kHistorySize][axis] / -kMaxAcceleration;         if (i > 0) {            CGContextAddLineToPoint(context, bounds.origin.x + (float)i / (float)(kHistorySize - 1) * bounds.size.width,                                     bounds.origin.y + bounds.size.height / 2 + value * bounds.size.height / 2);        } else {            CGContextMoveToPoint(context, bounds.origin.x + (float)i / (float)(kHistorySize - 1) * bounds.size.width,                                  bounds.origin.y + bounds.size.height / 2 + value * bounds.size.height / 2);        }    }    CGContextStrokePath(context);        // Draw the labels    CGContextSetGrayFillColor(context, 1.0, 1.0);    CGContextSetAllowsAntialiasing(context, true);    for (value = -kMaxAcceleration; value <= kMaxAcceleration - 1.0; value += 1.0) {        temp = roundf(bounds.origin.y + bounds.size.height / 2 + value / (2 * kMaxAcceleration) * bounds.size.height);        // NOTE: We need to draw upside-down as UIView referential has the Y axis going down        [[NSString stringWithFormat:@"%+.1f", -(value >= 0.0 ? value + 1.0 : value)]          drawAtPoint:CGPointMake(bounds.origin.x + 4, temp + (value >= 0.0 ? 3 : 0)) withFont:font];     }    temp = roundf(bounds.origin.y + bounds.size.height / 2);    CGPoint sPoint = CGPointMake(bounds.origin.x + bounds.size.width - 40, temp - 16);    [[NSString stringWithFormat:@"%c Axis", 'X' + axis] drawAtPoint:sPoint withFont:font];    CGContextSetAllowsAntialiasing(context, false);}- (void)drawRect:(CGRect)clip {    CGSize size = [self bounds].size;    CGContextRef context = UIGraphicsGetCurrentContext();    unsigned index = nextIndex, i;        // Draw the X, Y & Z graphs with anti-aliasing turned off    CGContextSetAllowsAntialiasing(context, false);    CGFloat hOver3 = size.height / 3, hOver4 = size.height / 4;    for (i = 0; i < 3; ++i) {        CGRect hBounds = CGRectMake(0, (hOver3 - hOver4) / 2 + (float)i * hOver3, size.width, hOver4);        [self drawHistory:i fromIndex:index inContext:context bounds:hBounds];    }    CGContextSetAllowsAntialiasing(context, true);  }@end