author Sam Lantinga <>
Sat, 15 Mar 2014 19:30:52 -0700
changeset 8627 704a0bfecf75
parent 7241 28602f5ca96d
permissions -rw-r--r--
Fixed iOS build
     1 ===========================================================================
     2 System Specific Notes
     3 ===========================================================================
     4 Linux:
     5 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 and I will help you get support for it.
     7 Mac:
     8 The Mac and iPhone APIs 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.
    10 iPhone: 
    11 Works out of box.
    13 Windows:
    14 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
    16 ===========================================================================
    17 Events
    18 ===========================================================================
    20 Sent when a finger (or stylus) is placed on a touch device.
    21 Fields:
    22 event.tfinger.touchId  - the Id of the touch device.
    23 event.tfinger.fingerId - the Id of the finger which just went down.
    24 event.tfinger.x        - the x coordinate of the touch (0..1)
    25 event.tfinger.y        - the y coordinate of the touch (0..1)
    26 event.tfinger.pressure - the pressure of the touch (0..1)
    29 Sent when a finger (or stylus) is moved on the touch device.
    30 Fields:
    31 Same as SDL_FINGERDOWN but with additional:
    32 event.tfinger.dx       - change in x coordinate during this motion event.
    33 event.tfinger.dy       - change in y coordinate during this motion event.
    36 Sent when a finger (or stylus) is lifted from the touch device.
    37 Fields:
    38 Same as SDL_FINGERDOWN.
    41 ===========================================================================
    42 Functions
    43 ===========================================================================
    44 SDL provides the ability to access the underlying Finger structures.
    45 These structures should _never_ be modified.
    47 The following functions are included from SDL_touch.h
    49 To get a SDL_TouchID call SDL_GetTouchDevice(index).
    50 This returns a SDL_TouchID.
    51 IMPORTANT: If the touch has been removed, or there is no touch with the given ID, SDL_GetTouchID will return 0. Be sure to check for this!
    53 The number of touch devices can be queried with SDL_GetNumTouchDevices().
    55 A SDL_TouchID may be used to get pointers to SDL_Finger.
    57 SDL_GetNumTouchFingers(touchID) may be used to get the number of fingers currently down on the device.
    59 The most common reason to access SDL_Finger is to query the fingers outside the event. In most cases accessing the fingers is using the event. This would be accomplished by code like the following:
    61       float x = event.tfinger.x;
    62       float y = event.tfinger.y;
    66 To get a SDL_Finger, call SDL_GetTouchFinger(touchID,index), where touchID is a SDL_TouchID, and index is the requested finger.
    67 This returns a SDL_Finger*, or NULL if the finger does not exist, or has been removed.
    68 A 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 SDL_FINGERUP event is polled.
    69 As a result, be very careful to check for NULL return values.
    71 A SDL_Finger has the following fields:
    72 >x,y,pressure:
    73 	The current coordinates of the touch.
    74 >pressure:
    75 	The pressure of the touch.
    77 ===========================================================================
    78 Notes
    79 ===========================================================================
    80 For a complete example see test/testgesture.c
    82 Please direct questions/comments to:
    84    (original author, API was changed since)