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.