Mercurial > sdl-ios-xcode
diff README.touch @ 4689:f9ab8df6d45a
Added README.touch and README.gesture. Moved touchtest/gestureSDLTest to test/testgesture
author | Jim Grandpre <jim.tla@gmail.com> |
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date | Sun, 15 Aug 2010 00:36:28 -0400 |
parents | |
children | baf8195aeb92 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/README.touch Sun Aug 15 00:36:28 2010 -0400 @@ -0,0 +1,77 @@ +=========================================================================== +Events +=========================================================================== +SDL_FINGERDOWN: +Sent when a finger (or stylus) is placed on a touch device. +Fields: +event.tfinger.touchId - the Id of the touch device. +event.tfinger.fingerId - the Id of the finger which just went down. +event.tfinger.x - the x coordinate of the touch (0..touch.xres) +event.tfinger.y - the y coordinate of the touch (0..touch.yres) +event.tfinger.pressure - the pressure of the touch (0..touch.pressureres) + +SDL_FINGERMOTION: +Sent when a finger (or stylus) is moved on the touch device. +Fields: +Same as FINGERDOWN but with additional: +event.tfginer.dx - chagne in x coordinate during this motion event. +event.tfginer.dy - chagne in y coordinate during this motion event. + +SDL_FINGERMOTION: +Sent when a finger (or stylus) is lifted from the touch device. +Fields: +Same as FINGERDOWN. + + +=========================================================================== +Functions +=========================================================================== +SDL provides the ability to access the underlying Touch and Finger structures. +These structures should _never_ be modified. + +The following functions are included from SDL_Touch.h + +To get a SDL_Touch device call SDL_GetTouch(touchId). +This returns an SDL_Touch*. +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! + +An SDL_Touch has the following fields: +>pressure_max, pressure_min, x_max, x_min, y_max, y_min + 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. +On Mac/iPhone systems _max will always be 0, and _min will always be 1. + +>xres,yres,pressures: + 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. + +>native_xres,native_yres,native_pressureres: + The native resolution of the touch device AS REPORTED BY THE OPERATING SYSTEM. +On Mac/iPhone systems these will always be 1. + +>num_fingers: + The number of fingers currently down on the device. + +>fingers: + An array of pointers to the fingers which are on the device. + + +The most common reason to get a touch device is to normalize inputs. This would look something like: + + SDL_Touch* inTouch = SDL_GetTouch(event.tfinger.touchId); + if(inTouch == NULL) continue; + + float x = ((float)event.tfinger.x)/inTouch->xres; + float y = ((float)event.tfinger.y)/inTouch->yres; + + +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. +This returns an SDL_Finger*, or null if the finger does not exist, or has been removed. +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. +As a result, be very careful to check for null return values. + +An SDL_Finger has the following fields: +>x,y,pressure: + The current coordinates of the touch. +>xdelta,ydelta: + The change in position resulting from the last finger motion. +>last_x, last_y, last_pressure: + The previous coordinates of the touch. \ No newline at end of file