docs/README-touch.md
author Sam Lantinga <slouken@libsdl.org>
Thu, 23 May 2019 14:19:00 -0700
changeset 12756 4116bf232fe7
parent 10486 5bf595c48fd4
permissions -rw-r--r--
Added a function to get the current Android SDK version at runtime
slouken@10486
     1
Touch
gabomdq@9023
     2
===========================================================================
gabomdq@9023
     3
System Specific Notes
gabomdq@9023
     4
===========================================================================
gabomdq@9023
     5
Linux:
gabomdq@9023
     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.
gabomdq@9023
     7
gabomdq@9023
     8
Mac:
gabomdq@9023
     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.
gabomdq@9023
    10
gabomdq@9023
    11
iPhone: 
gabomdq@9023
    12
Works out of box.
gabomdq@9023
    13
gabomdq@9023
    14
Windows:
gabomdq@9023
    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
gabomdq@9023
    16
gabomdq@9023
    17
===========================================================================
gabomdq@9023
    18
Events
gabomdq@9023
    19
===========================================================================
gabomdq@9023
    20
SDL_FINGERDOWN:
gabomdq@9023
    21
Sent when a finger (or stylus) is placed on a touch device.
gabomdq@9023
    22
Fields:
philipp@9066
    23
* event.tfinger.touchId  - the Id of the touch device.
philipp@9066
    24
* event.tfinger.fingerId - the Id of the finger which just went down.
philipp@9066
    25
* event.tfinger.x        - the x coordinate of the touch (0..1)
philipp@9066
    26
* event.tfinger.y        - the y coordinate of the touch (0..1)
philipp@9066
    27
* event.tfinger.pressure - the pressure of the touch (0..1)
gabomdq@9023
    28
gabomdq@9023
    29
SDL_FINGERMOTION:
gabomdq@9023
    30
Sent when a finger (or stylus) is moved on the touch device.
gabomdq@9023
    31
Fields:
gabomdq@9023
    32
Same as SDL_FINGERDOWN but with additional:
philipp@9066
    33
* event.tfinger.dx       - change in x coordinate during this motion event.
philipp@9066
    34
* event.tfinger.dy       - change in y coordinate during this motion event.
gabomdq@9023
    35
gabomdq@9023
    36
SDL_FINGERUP:
gabomdq@9023
    37
Sent when a finger (or stylus) is lifted from the touch device.
gabomdq@9023
    38
Fields:
gabomdq@9023
    39
Same as SDL_FINGERDOWN.
gabomdq@9023
    40
gabomdq@9023
    41
gabomdq@9023
    42
===========================================================================
gabomdq@9023
    43
Functions
gabomdq@9023
    44
===========================================================================
philipp@10212
    45
SDL provides the ability to access the underlying SDL_Finger structures.
gabomdq@9023
    46
These structures should _never_ be modified.
gabomdq@9023
    47
gabomdq@9023
    48
The following functions are included from SDL_touch.h
gabomdq@9023
    49
philipp@10212
    50
To get a SDL_TouchID call SDL_GetTouchDevice(int index).
gabomdq@9023
    51
This returns a SDL_TouchID.
philipp@10212
    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!
gabomdq@9023
    53
gabomdq@9023
    54
The number of touch devices can be queried with SDL_GetNumTouchDevices().
gabomdq@9023
    55
gabomdq@9023
    56
A SDL_TouchID may be used to get pointers to SDL_Finger.
gabomdq@9023
    57
gabomdq@9023
    58
SDL_GetNumTouchFingers(touchID) may be used to get the number of fingers currently down on the device.
gabomdq@9023
    59
gabomdq@9023
    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:
gabomdq@9023
    61
gabomdq@9023
    62
      float x = event.tfinger.x;
gabomdq@9023
    63
      float y = event.tfinger.y;
gabomdq@9023
    64
gabomdq@9023
    65
gabomdq@9023
    66
philipp@10212
    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.
philipp@10212
    68
This returns a SDL_Finger *, or NULL if the finger does not exist, or has been removed.
gabomdq@9023
    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.
gabomdq@9023
    70
As a result, be very careful to check for NULL return values.
gabomdq@9023
    71
gabomdq@9023
    72
A SDL_Finger has the following fields:
philipp@10212
    73
* x, y:
gabomdq@9023
    74
	The current coordinates of the touch.
philipp@9066
    75
* pressure:
gabomdq@9023
    76
	The pressure of the touch.
gabomdq@9023
    77
philipp@9066
    78
gabomdq@9023
    79
===========================================================================
gabomdq@9023
    80
Notes
gabomdq@9023
    81
===========================================================================
gabomdq@9023
    82
For a complete example see test/testgesture.c
gabomdq@9023
    83
gabomdq@9023
    84
Please direct questions/comments to:
gabomdq@9023
    85
   jim.tla+sdl_touch@gmail.com
gabomdq@9023
    86
   (original author, API was changed since)