README.touch
author Jim Grandpre <jim.tla@gmail.com>
Sun, 15 Aug 2010 00:36:28 -0400
changeset 4689 f9ab8df6d45a
child 4690 baf8195aeb92
permissions -rw-r--r--
Added README.touch and README.gesture. Moved touchtest/gestureSDLTest to test/testgesture
     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.