author Ryan C. Gordon
Thu, 16 Feb 2017 16:59:07 -0500
changeset 10893 54480745c410
parent 10486 5bf595c48fd4
permissions -rw-r--r--
More HTTPS doc tweaks.

(mostly I'm testing buildbot though. :) )
     1 Touch
     2 ===========================================================================
     3 System Specific Notes
     4 ===========================================================================
     5 Linux:
     6 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.
     8 Mac:
     9 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.
    11 iPhone: 
    12 Works out of box.
    14 Windows:
    15 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
    17 ===========================================================================
    18 Events
    19 ===========================================================================
    21 Sent when a finger (or stylus) is placed on a touch device.
    22 Fields:
    23 * event.tfinger.touchId  - the Id of the touch device.
    24 * event.tfinger.fingerId - the Id of the finger which just went down.
    25 * event.tfinger.x        - the x coordinate of the touch (0..1)
    26 * event.tfinger.y        - the y coordinate of the touch (0..1)
    27 * event.tfinger.pressure - the pressure of the touch (0..1)
    30 Sent when a finger (or stylus) is moved on the touch device.
    31 Fields:
    32 Same as SDL_FINGERDOWN but with additional:
    33 * event.tfinger.dx       - change in x coordinate during this motion event.
    34 * event.tfinger.dy       - change in y coordinate during this motion event.
    37 Sent when a finger (or stylus) is lifted from the touch device.
    38 Fields:
    39 Same as SDL_FINGERDOWN.
    42 ===========================================================================
    43 Functions
    44 ===========================================================================
    45 SDL provides the ability to access the underlying SDL_Finger structures.
    46 These structures should _never_ be modified.
    48 The following functions are included from SDL_touch.h
    50 To get a SDL_TouchID call SDL_GetTouchDevice(int index).
    51 This returns a SDL_TouchID.
    52 IMPORTANT: If the touch has been removed, or there is no touch with the given index, SDL_GetTouchDevice() will return 0. Be sure to check for this!
    54 The number of touch devices can be queried with SDL_GetNumTouchDevices().
    56 A SDL_TouchID may be used to get pointers to SDL_Finger.
    58 SDL_GetNumTouchFingers(touchID) may be used to get the number of fingers currently down on the device.
    60 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:
    62       float x = event.tfinger.x;
    63       float y = event.tfinger.y;
    67 To get a SDL_Finger, call SDL_GetTouchFinger(SDL_TouchID touchID, int index), where touchID is a SDL_TouchID, and index is the requested finger.
    68 This returns a SDL_Finger *, or NULL if the finger does not exist, or has been removed.
    69 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.
    70 As a result, be very careful to check for NULL return values.
    72 A SDL_Finger has the following fields:
    73 * x, y:
    74 	The current coordinates of the touch.
    75 * pressure:
    76 	The pressure of the touch.
    79 ===========================================================================
    80 Notes
    81 ===========================================================================
    82 For a complete example see test/testgesture.c
    84 Please direct questions/comments to:
    86    (original author, API was changed since)