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Merged Jim's Google Summer of Code work from SDL-gsoc2010_gesture
author Sam Lantinga <slouken@libsdl.org>
date Sun, 22 Aug 2010 12:07:55 -0700
parents 2ede56a19f2f
children
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4638:08d22c54a21f 4694:c24ba2cc9583
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 jim.tla+sdl_touch@gmail.com and I will help you get support for it.
6
7 Mac:
8 The Mac and Iphone API's 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.
9
10 iPhone:
11 Works out of box.
12
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 jim.tla+sdl_touch@gmail.com
15
16 ===========================================================================
17 Events
18 ===========================================================================
19 SDL_FINGERDOWN:
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..touch.xres)
25 event.tfinger.y - the y coordinate of the touch (0..touch.yres)
26 event.tfinger.pressure - the pressure of the touch (0..touch.pressureres)
27
28 SDL_FINGERMOTION:
29 Sent when a finger (or stylus) is moved on the touch device.
30 Fields:
31 Same as FINGERDOWN but with additional:
32 event.tfginer.dx - change in x coordinate during this motion event.
33 event.tfginer.dy - change in y coordinate during this motion event.
34
35 SDL_FINGERMOTION:
36 Sent when a finger (or stylus) is lifted from the touch device.
37 Fields:
38 Same as FINGERDOWN.
39
40
41 ===========================================================================
42 Functions
43 ===========================================================================
44 SDL provides the ability to access the underlying Touch and Finger structures.
45 These structures should _never_ be modified.
46
47 The following functions are included from SDL_Touch.h
48
49 To get a SDL_Touch device call SDL_GetTouch(touchId).
50 This returns an SDL_Touch*.
51 IMPORTANT: If the touch has been removed, or there is no touch with the given ID, SDL_GetTouch will return null. Be sure to check for this!
52
53 An SDL_Touch has the following fields:
54 >xres,yres,pressures:
55 The resolution at which x,y, and pressure values are reported. Currently these will always be equal to 2^15, but this may not always be the case.
56
57 >pressure_max, pressure_min, x_max, x_min, y_max, y_min
58 Which give, respectively, the maximum and minumum values that the touch digitizer can return for pressure, x coordiniate, and y coordinate AS REPORTED BY THE OPERATING SYSTEM.
59 On Mac/iPhone systems _max will always be 0, and _min will always be 1.
60
61 >native_xres,native_yres,native_pressureres:
62 The native resolution of the touch device AS REPORTED BY THE OPERATING SYSTEM.
63 On Mac/iPhone systems these will always be 1.
64
65 >num_fingers:
66 The number of fingers currently down on the device.
67
68 >fingers:
69 An array of pointers to the fingers which are on the device.
70
71
72 The most common reason to access a touch device is to normalize inputs. This would be accomplished by code like the following:
73
74 SDL_Touch* inTouch = SDL_GetTouch(event.tfinger.touchId);
75 if(inTouch == NULL) continue; //The touch has been removed
76
77 float x = ((float)event.tfinger.x)/inTouch->xres;
78 float y = ((float)event.tfinger.y)/inTouch->yres;
79
80
81
82 To get an SDL_Finger, call SDL_GetFinger(touch,fingerId), where touch is a pointer to an SDL_Touch device, and fingerId is the id of the requested finger.
83 This returns an SDL_Finger*, or null if the finger does not exist, or has been removed.
84 An 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 FINGERUP event is polled.
85 As a result, be very careful to check for null return values.
86
87 An SDL_Finger has the following fields:
88 >x,y,pressure:
89 The current coordinates of the touch.
90 >xdelta,ydelta:
91 The change in position resulting from the last finger motion.
92 >last_x, last_y, last_pressure:
93 The previous coordinates of the touch.
94
95 ===========================================================================
96 Notes
97 ===========================================================================
98 For a complete example see test/testgesture.c
99
100 Please direct questions/comments to:
101 jim.tla+sdl_touch@gmail.com