README.touch
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     1 ===========================================================================
       
     2 Events
       
     3 ===========================================================================
       
     4 SDL_FINGERDOWN:
       
     5 Sent when a finger (or stylus) is placed on a touch device.
       
     6 Fields:
       
     7 event.tfinger.touchId  - the Id of the touch device.
       
     8 event.tfinger.fingerId - the Id of the finger which just went down.
       
     9 event.tfinger.x        - the x coordinate of the touch (0..touch.xres)
       
    10 event.tfinger.y        - the y coordinate of the touch (0..touch.yres)
       
    11 event.tfinger.pressure - the pressure of the touch (0..touch.pressureres)
       
    12 
       
    13 SDL_FINGERMOTION:
       
    14 Sent when a finger (or stylus) is moved on the touch device.
       
    15 Fields:
       
    16 Same as FINGERDOWN but with additional:
       
    17 event.tfginer.dx       - chagne in x coordinate during this motion event.
       
    18 event.tfginer.dy       - chagne in y coordinate during this motion event.
       
    19 
       
    20 SDL_FINGERMOTION:
       
    21 Sent when a finger (or stylus) is lifted from the touch device.
       
    22 Fields:
       
    23 Same as FINGERDOWN.
       
    24 
       
    25 
       
    26 ===========================================================================
       
    27 Functions
       
    28 ===========================================================================
       
    29 SDL provides the ability to access the underlying Touch and Finger structures.
       
    30 These structures should _never_ be modified.
       
    31 
       
    32 The following functions are included from SDL_Touch.h
       
    33 
       
    34 To get a SDL_Touch device call SDL_GetTouch(touchId). 
       
    35 This returns an SDL_Touch*. 
       
    36 IMPORTANT: If the touch has been removed, or there is no touch with the given ID, SDL_GetTouch will return null. Be sure to check for this!
       
    37 
       
    38 An SDL_Touch has the following fields:
       
    39 >pressure_max, pressure_min, x_max, x_min, y_max, y_min
       
    40 	Which give, respectively, the maximum and minumum values that the touch digitizer can return for pressure, x coordiniate, and y coordinate AS REPORTED BY THE OPERATING SYSTEM.
       
    41 On Mac/iPhone systems _max will always be 0, and _min will always be 1. 
       
    42 
       
    43 >xres,yres,pressures:
       
    44 	The resolution at which x,y, and pressure values are reported. Currently these will always be equal to 2^15, but this may not always be the case. 
       
    45 
       
    46 >native_xres,native_yres,native_pressureres:
       
    47 	The native resolution of the touch device AS REPORTED BY THE OPERATING SYSTEM.
       
    48 On Mac/iPhone systems these will always be 1.
       
    49 
       
    50 >num_fingers:
       
    51 	The number of fingers currently down on the device.
       
    52 
       
    53 >fingers:
       
    54 	An array of pointers to the fingers which are on the device.
       
    55 
       
    56 
       
    57 The most common reason to get a touch device is to normalize inputs. This would look something like:
       
    58 
       
    59       SDL_Touch* inTouch = SDL_GetTouch(event.tfinger.touchId);
       
    60       if(inTouch == NULL) continue;
       
    61 
       
    62       float x = ((float)event.tfinger.x)/inTouch->xres;
       
    63       float y = ((float)event.tfinger.y)/inTouch->yres;      
       
    64 
       
    65 
       
    66 To get an SDL_Finger, call SDL_GetFinger(touch,fingerId), where touch is a pointer to an SDL_Touch device, and fingerId is the id of the requested finger.
       
    67 This returns an SDL_Finger*, or null if the finger does not exist, or has been removed.
       
    68 An SDL_Finger is guaranteed to be persistent for the duration of a touch, but it will be de-allocated as soon as the finger is removed. This occurs when the SDL_FINGERUP event is _added_ to the event queue, and thus BEFORE the FINGERUP event is seen. 
       
    69 As a result, be very careful to check for null return values.
       
    70 
       
    71 An SDL_Finger has the following fields:
       
    72 >x,y,pressure:
       
    73 	The current coordinates of the touch.
       
    74 >xdelta,ydelta: 
       
    75 	The change in position resulting from the last finger motion.
       
    76 >last_x, last_y, last_pressure:
       
    77 	 The previous coordinates of the touch.