1Touch
2===========================================================================
3System Specific Notes
4===========================================================================
5Linux:
6The 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.
7
8Mac:
9The 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
11iPhone:
12Works out of box.
13
14Windows:
15Unfortunately 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
16
17===========================================================================
18Events
19===========================================================================
20SDL_FINGERDOWN:
21Sent when a finger (or stylus) is placed on a touch device.
22Fields:
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)
28
29SDL_FINGERMOTION:
30Sent when a finger (or stylus) is moved on the touch device.
31Fields:
32Same 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.
35
36SDL_FINGERUP:
37Sent when a finger (or stylus) is lifted from the touch device.
38Fields:
39Same as SDL_FINGERDOWN.
40
41
42===========================================================================
43Functions
44===========================================================================
45SDL provides the ability to access the underlying SDL_Finger structures.
46These structures should _never_ be modified.
47
48The following functions are included from SDL_touch.h
49
50To get a SDL_TouchID call SDL_GetTouchDevice(int index).
51This returns a SDL_TouchID.
52IMPORTANT: 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!
53
54The number of touch devices can be queried with SDL_GetNumTouchDevices().
55
56A SDL_TouchID may be used to get pointers to SDL_Finger.
57
58SDL_GetNumTouchFingers(touchID) may be used to get the number of fingers currently down on the device.
59
60The 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
62      float x = event.tfinger.x;
63      float y = event.tfinger.y;
64
65
66
67To get a SDL_Finger, call SDL_GetTouchFinger(SDL_TouchID touchID, int index), where touchID is a SDL_TouchID, and index is the requested finger.
68This returns a SDL_Finger *, or NULL if the finger does not exist, or has been removed.
69A 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.
70As a result, be very careful to check for NULL return values.
71
72A SDL_Finger has the following fields:
73* x, y:
74	The current coordinates of the touch.
75* pressure:
76	The pressure of the touch.
77
78
79===========================================================================
80Notes
81===========================================================================
82For a complete example see test/testgesture.c
83
84Please direct questions/comments to:
85   jim.tla+sdl_touch@gmail.com
86   (original author, API was changed since)
87