src/joystick/iphoneos/SDLUIAccelerationDelegate.m

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2013 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/

#import "SDLUIAccelerationDelegate.h"
/* needed for SDL_IPHONE_MAX_GFORCE macro */
#import "../../../include/SDL_config_iphoneos.h"

static SDLUIAccelerationDelegate *sharedDelegate=nil;

@implementation SDLUIAccelerationDelegate

/*
    Returns a shared instance of the SDLUIAccelerationDelegate, creating the shared delegate if it doesn't exist yet.
*/
+(SDLUIAccelerationDelegate *)sharedDelegate {
    if (sharedDelegate == nil) {
        sharedDelegate = [[SDLUIAccelerationDelegate alloc] init];
    }
    return sharedDelegate;
}
/*
    UIAccelerometerDelegate delegate method.  Invoked by the UIAccelerometer instance when it has new data for us.
    We just take the data and mark that we have new data available so that the joystick system will pump it to the
    events system when SDL_SYS_JoystickUpdate is called.
*/
-(void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {

    x = acceleration.x;
    y = acceleration.y;
    z = acceleration.z;

    hasNewData = YES;
}
/*
    getLastOrientation -- put last obtained accelerometer data into Sint16 array

    Called from the joystick system when it needs the accelerometer data.
    Function grabs the last data sent to the accelerometer and converts it
    from floating point to Sint16, which is what the joystick system expects.

    To do the conversion, the data is first clamped onto the interval
    [-SDL_IPHONE_MAX_G_FORCE, SDL_IPHONE_MAX_G_FORCE], then the data is multiplied
    by MAX_SINT16 so that it is mapped to the full range of an Sint16.

    You can customize the clamped range of this function by modifying the
    SDL_IPHONE_MAX_GFORCE macro in SDL_config_iphoneos.h.

    Once converted to Sint16, the accelerometer data no longer has coherent units.
    You can convert the data back to units of g-force by multiplying it
    in your application's code by SDL_IPHONE_MAX_GFORCE / 0x7FFF.
 */
-(void)getLastOrientation:(Sint16 *)data {

    #define MAX_SINT16 0x7FFF

    /* clamp the data */
    if (x > SDL_IPHONE_MAX_GFORCE) x = SDL_IPHONE_MAX_GFORCE;
    else if (x < -SDL_IPHONE_MAX_GFORCE) x = -SDL_IPHONE_MAX_GFORCE;
    if (y > SDL_IPHONE_MAX_GFORCE) y = SDL_IPHONE_MAX_GFORCE;
    else if (y < -SDL_IPHONE_MAX_GFORCE) y = -SDL_IPHONE_MAX_GFORCE;
    if (z > SDL_IPHONE_MAX_GFORCE) z = SDL_IPHONE_MAX_GFORCE;
    else if (z < -SDL_IPHONE_MAX_GFORCE) z = -SDL_IPHONE_MAX_GFORCE;

    /* pass in data mapped to range of SInt16 */
    data[0] = (x / SDL_IPHONE_MAX_GFORCE) * MAX_SINT16;
    data[1] = (y / SDL_IPHONE_MAX_GFORCE) * MAX_SINT16;
    data[2] = (z / SDL_IPHONE_MAX_GFORCE) * MAX_SINT16;

}

/*
    Initialize SDLUIAccelerationDelegate.  Since we don't have any data yet,
    just set our last received data to zero, and indicate we don't have any;
*/
-(id)init {
    self = [super init];
    x = y = z = 0.0;
    hasNewData = NO;
    return self;
}

-(void)dealloc {
    sharedDelegate = nil;
    [self shutdown];
    [super dealloc];
}

/*
    Lets our delegate start receiving accelerometer updates.
*/
-(void)startup {
    [UIAccelerometer sharedAccelerometer].delegate = self;
    isRunning = YES;
}
/*
    Stops our delegate from receiving accelerometer updates.
*/
-(void)shutdown {
    if ([UIAccelerometer sharedAccelerometer].delegate == self) {
        [UIAccelerometer sharedAccelerometer].delegate = nil;
    }
    isRunning = NO;
}
/*
    Our we currently receiving accelerometer updates?
*/
-(BOOL)isRunning {
    return isRunning;
}
/*
    Do we have any data that hasn't been pumped into SDL's event system?
*/
-(BOOL)hasNewData {
    return hasNewData;
}
/*
    When the joystick system grabs the new data, it sets this to NO.
*/
-(void)setHasNewData:(BOOL)value {
    hasNewData = value;
}

@end