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Code Block

language	cpp

uint16 type  // Type of record, including KEY (key/button), REL (relative scalar), ABS (absolute scalar), SYN (Synchronization events.) or DEV (Device change events).
uint16 code  // This indicated which item (be it a key or axis) this record represents.
uint32 value // This is the new value for the item indicated by two field above. For a button or key, this would be a Boolean.

The records above are able to accommodate a huge number of different types of event. Furthermore, events are aggregated to form more complex events. Each input device will only be able to send a small subset of the possible events. DEV (device) events are used to indicate which device is emitting the following events, as well as indicating which events are possible. For example a tablet stylus can emit absolute X and Y events, while a traditional mouse emits relative X and Y events.

Below is a small subset of events that are possible. This list should probably be considered the minimum to set to implement. A fuller list can be found here with descriptions here. Detail on the multitouch protocol here.

Type 0x6 DEV: Device

These events describe actions relating to the device emmiting the remaining events. DEV events are not subject to Synchronization events.

Code	Name	Description
0x1	DEV_SET	Events after this event belong to the device indicated by <value>. A value of -1 indicates that it is from an unknown source. This number may be referred to as the device's slot number.
0x2	DEV_CONF	This indicates that a new device has been created, which from here shall be referred to as <value>. The provided slot number ( <value> ) can be used to find a description of this device, in the configuration space, described later. This information is expected to be considered before attempting to decode events for this device.
0x3	DEV_RESET	This indicates that device <value> is no longer valid, and any resources associated with this may be freed. If <value> is 0xFFFF, then all devices are existing invalid - such event is used on start up.

Type 0x0 SYN: Synchronization

Code	Name	Description
0x0	SYN_REPORT	This is used as a barrier to indicate that all events of other types (excluding DEV), which occur between the same set of SYN:REPORT events, occurred at the same time. That is to say, events between pairs of SYN:REPORT events are to be aggregated. For example, when moving a mouse, it is common for both the X and Y coordinate to change together, and so an event for each would be emitted, and because they where emmited between a pair of SYN:REPORT events, they would be aggregated. If however, only one axis changed, then only an event for that axis would be emitted. After this event has been added to the buffer, and interrupt is generated.
0x2	SYN_MT_REPORT	This is used for less able multitouch devices, to separate multiple sets of X/Y coordinates. We currently have no devices which do this.
0x3	SYN_DROPPED	This informs the client when input events have been dropped from the evdev input buffer due to a buffer overrun. The client should use this event as a hint to reset its state or ignore all following events until the next packet begins. Client should ignore all events up to and including next SYN_REPORT.

Type 0x2 REL: Relative

Code	Name	Description
0x00	REL_X	Movement on the X axis.
0x01	REL_Y	Movement on the Y axis.
0x08	REL_WHEEL	Vertical wheel movement.

Type 0x3 ABS: Absolute

Code	Name	Description
0x00	ABS_X	Position on the X axis.
0x01	ABS_Y	Position on the Y axis.
0x18	ABS_PRESSURE	The pressure the pen/tool is being applied.
0x2f	ABS_MT_SLOT	Each finger/pen in contact with the screen is given a slot number, and this is maintained until it is released. Multitouch events, on the current device, are henceforth for this slot. If only one finger/pen is in contact with the screen, then only one slot in required, and so this event may be omitted. If multiple fingers/pens are in contact with the screen, it would be common for may slot changes to occur during one pair SYN:REPORT events, to indicate each finger moved at the same time.
0x35	ABS_MT_POSITION_X	X coordinate for the current slot. (Finger/pen)
0x36	ABS_MT_POSITION_Y	Y coordinate for the current slot. (Finger/pen)
0x39	ABS_MT_TRACKING_ID	Unique ID of initiated contact, a value of -1 indicates finger/pen released.

Type 0x01 KEY: Key/Button

Code	Name	Description
0x110	BTN_LEFT	The left button on a mouse.
0x111	BTN_RIGHT	The right button on a mouse.
0x112	BTN_MIDDLE	The middle button on a mouse.
0x113	BTN_SIDE	The side button on a mouse.
0x114	BTN_EXTRA	The extra button on a mouse.
0x115	BTN_FORWARD	The forward button on a mouse.
0x116	BTN_BACK	The back button on a mouse.
0x117	BTN_TASK	The task button on a mouse.
0x140	BTN_TOOL_PEN	The current tool is now a pen.
0x141	BTN_TOOL_RUBBER	The current tool is now a rubber.
0x145	BTN_TOOL_FINGER	The current tool is now a finger.
0x146	BTN_TOOL_MOUSE	The current tool is now a mouse.
0x14a	BTN_TOUCH	The current tool touched the surface.
0x14b	BTN_STYLUS	The first button on the stylus was pressed.
0x14c	BTN_STYLUS2	The second button on the stylus was pressed.

Example

A stream might look as follows: