Merge commit 'dec0d4ec4153bf9fc2b78ae6c2df45b6ea8dde7a' as 'external/sdl/SDL'

external/sdl/SDL/docs/README-touch.md

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+Touch
+===========================================================================
+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
+
+===========================================================================
+Events
+===========================================================================
+SDL_EVENT_FINGER_DOWN:
+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_EVENT_FINGER_MOTION:
+Sent when a finger (or stylus) is moved on the touch device.
+Fields:
+Same as SDL_EVENT_FINGER_DOWN 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_EVENT_FINGER_UP:
+Sent when a finger (or stylus) is lifted from the touch device.
+Fields:
+Same as SDL_EVENT_FINGER_DOWN.
+
+
+===========================================================================
+Functions
+===========================================================================
+SDL provides the ability to access the underlying SDL_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(int index).
+This returns a SDL_TouchID.
+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!
+
+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(SDL_TouchID touchID, int 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_EVENT_FINGER_UP event is _added_ to the event queue, and thus _before_ the SDL_EVENT_FINGER_UP event is polled.
+As a result, be very careful to check for NULL return values.
+
+A SDL_Finger has the following fields:
+* x, y:
+	The current coordinates of the touch.
+* pressure:
+	The pressure of the touch.
+
+
+Please direct questions/comments to:
+   jim.tla+sdl_touch@gmail.com
+   (original author, API was changed since)