SDL  2.0
docs/README-touch.md
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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 jim.tla+sdl_touch@gmail.com and I will help you get support for it.
7 
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.
10 
11 iPhone:
12 Works out of box.
13 
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 jim.tla+sdl_touch@gmail.com
16 
17 ===========================================================================
18 Events
19 ===========================================================================
20 SDL_FINGERDOWN:
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)
28 
29 SDL_FINGERMOTION:
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.
35 
36 SDL_FINGERUP:
37 Sent when a finger (or stylus) is lifted from the touch device.
38 Fields:
39 Same as SDL_FINGERDOWN.
40 
41 
42 ===========================================================================
43 Functions
44 ===========================================================================
45 SDL provides the ability to access the underlying SDL_Finger structures.
46 These structures should _never_ be modified.
47 
48 The following functions are included from SDL_touch.h
49 
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!
53 
54 The number of touch devices can be queried with SDL_GetNumTouchDevices().
55 
56 A SDL_TouchID may be used to get pointers to SDL_Finger.
57 
58 SDL_GetNumTouchFingers(touchID) may be used to get the number of fingers currently down on the device.
59 
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:
61 
62  float x = event.tfinger.x;
63  float y = event.tfinger.y;
64 
65 
66 
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.
71 
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.
77 
78 
79 ===========================================================================
80 Notes
81 ===========================================================================
82 For a complete example see test/testgesture.c
83 
84 Please direct questions/comments to:
85  jim.tla+sdl_touch@gmail.com
86  (original author, API was changed since)