forked from LuaDist/sdl
-
Notifications
You must be signed in to change notification settings - Fork 0
/
README-touch.txt
84 lines (63 loc) · 3.96 KB
/
README-touch.txt
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
===========================================================================
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 [email protected] and I will help you get support for it.
Mac:
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.
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 [email protected]
===========================================================================
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..1)
event.tfinger.y - the y coordinate of the touch (0..1)
event.tfinger.pressure - the pressure of the touch (0..1)
SDL_FINGERMOTION:
Sent when a finger (or stylus) is moved on the touch device.
Fields:
Same as SDL_FINGERDOWN but with additional:
event.tfinger.dx - change in x coordinate during this motion event.
event.tfinger.dy - change in y coordinate during this motion event.
SDL_FINGERUP:
Sent when a finger (or stylus) is lifted from the touch device.
Fields:
Same as SDL_FINGERDOWN.
===========================================================================
Functions
===========================================================================
SDL provides the ability to access the underlying Finger structures.
These structures should _never_ be modified.
The following functions are included from SDL_touch.h
To get a SDL_TouchID call SDL_GetTouchDevice(index).
This returns a SDL_TouchID.
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!
The number of touch devices can be queried with SDL_GetNumTouchDevices().
A SDL_TouchID may be used to get pointers to SDL_Finger.
SDL_GetNumTouchFingers(touchID) may be used to get the number of fingers currently down on the device.
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:
float x = event.tfinger.x;
float y = event.tfinger.y;
To get a SDL_Finger, call SDL_GetTouchFinger(touchID,index), where touchID is a SDL_TouchID, and index is the requested finger.
This returns a SDL_Finger*, or NULL if the finger does not exist, or has been removed.
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.
As a result, be very careful to check for NULL return values.
A SDL_Finger has the following fields:
>x,y,pressure:
The current coordinates of the touch.
>pressure:
The pressure of the touch.
===========================================================================
Notes
===========================================================================
For a complete example see test/testgesture.c
Please direct questions/comments to:
(original author, API was changed since)