=========================================================================== System Specific Notes =========================================================================== Linux: The linux touch system is currently based off event streams, and proc/bus/devices. The active user must be given permissions to read /dev/input/TOUCHDEVICE, where TOUCHDEVICE is the event stream for your device. Currently only Wacom tablets are supported. If you have an unsupported tablet contact me at jim.tla+sdl_touch@gmail.com and I will help you get support for it. Mac: The Mac and Iphone API's are pretty. If your touch device supports them then you'll be fine. If it doesn't, then there isn't much we can do. iPhone: Works out of box. Windows: Unfortunately there is no windows support as of yet. Support for Windows 7 is planned, but we currently have no way to test. If you have a Windows 7 WM_TOUCH supported device, and are willing to help test please contact me at jim.tla+sdl_touch@gmail.com =========================================================================== 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 - change in x coordinate during this motion event. event.tfginer.dy - change 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: >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. >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. >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 access a touch device is to normalize inputs. This would be accomplished by code like the following: SDL_Touch* inTouch = SDL_GetTouch(event.tfinger.touchId); if(inTouch == NULL) continue; //The touch has been removed 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 polled. 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. =========================================================================== Notes =========================================================================== For a complete example see test/testgesture.c Please direct questions/comments to: jim.tla+sdl_touch@gmail.com