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- 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 jim.tla+sdl_touch@gmail.com 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 jim.tla+sdl_touch@gmail.com
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- 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:
- jim.tla+sdl_touch@gmail.com
- (original author, API was changed since)
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