Overlay File Format

Overlay File Format

This is a work in progress for documenting the overlay layout files used by the IntelliKeys software. Please add and correct details.

There are at least three different file extensions for overlay files, but it appears all of them starts with overlay data in the same format. A guess is that the data at the end of the file might be used for editing.

An overlay file is a list of membrane regions and which keys each respective region activates. The list can be split into modes/levels such that a membrane region sends different events depending on the mode.

The code for parsing the overlay files is in source files named IKOverlay, IKDevice and IKUniversal.

File Contents

The file contents starting at the beginning of the file is:

Size	Description
2 bytes LE	Length The number of bytes in the command lookup table, including length and checksum. At most 0x7200= 29184 bytes.
2 bytes LE	Checksum A 16-bit sum of all bytes in command table.
Length-4 bytes	The command table. It describes how membrane presses and switches should be converted to keyboard and mouse input. See tables below for encoding.
32 bytes	Name The name of the overlay file, encoded as command data. E.g. upper case ‘A’ is encoded as ‘Shift+A’.
1 byte	Unknown/Number Is always 0?
1 byte	NumberOfLevels An overlay can switch between up to 16 different modes, called levels in the code. This changes how membrane presses are converted to key inputs.
1 byte	Unknown/SetupFlag Is always 0?
1 byte	Unknown/CoordMode Is always 0?
4 bytes	Unused/Reserved
16 bytes	Unknown/BaseLevel
16 bytes	Unknown/MouseLevel
2 bytes BE	OffsetLevel0 Offset of command table for mode/level 0. Offset in bytes from start of file.
2 bytes BE	OffsetLevel1 Offset of command table for mode/level 1. Offset in bytes from start of file.
...	...
2 bytes BE	OffsetLevel15 Offset of command table for mode/level 15. Offset in bytes from start of file.
?	Any data after the above structure is not used by the command processing.

Command table/list

The command table is a list of when each command is triggered and what to do when it is triggered. It is encoded as a repeated list of the following:

Size	Description
1 byte	Domain A unique number of the command, duplicates are not expected. 0 Indicates the last command in the list. Must not be 0xff for switches.
2 bytes	MembraneLocation/SwitchNumber If the first byte is any of {255, 254, 253, 252, 251, 250} it matches switch 1 through 6 respectively. Otherwise it is a bit-encoded rectangle on the membrane. The first byte is the x offset and length. The second byte is the y offset and length. The offset and length are encoded in each byte using the 3 most significant bits for length, l, and the 5 least significant bits for offset, o: 0blllooooo
? bytes	CommandData A list of actions to perform when the command is triggered. Each action is encoded as one or more non-zero bytes. The last action is end-of-actions.

CommandData actions

The action list for each command can be one key or a list of keys. If it is one key it behaves as a regular keyboard, otherwise it behaves as each key is typed one after the other. There are also special actions for mouse movement and changing the keyboard settings. The following table lists all known actions.

Byte value	Action/Key
0x00	End of the action list
0x01	F1
0x02	F2
0x03	F3
0x04	F4
0x05	F5
0x06	F6
0x07	F7
0x08	F8
0x09	F9
0x0A	F10
0x0B	F11
0x0C	F12
0x0D	Print Screen
0x0E	Scroll Lock
0x0F	Pause
0x10	Numpad 0
0x11	Numpad 1
0x12	Numpad 2
0x13	Numpad 3
0x14	Numpad 4
0x15	Numpad 5
0x16	Numpad 6
0x17	Numpad 7
0x18	Numpad 8
0x19	Numpad 9
0x1A	Numpad +
0x1B	Numpad -
0x1C	Numpad ×
0x1D	Numpad ÷
0x1E	Numpad =
0x1F	Numpad ⏎
0x20	Space
0x21	Numpad .
0x22	Insert
0x23	Delete
0x24	Up Arrow
0x25	Down Arrow
0x26	Left Arrow
0x27	Right Arrow
0x28	Home
0x29	End
0x2A	Page Up
0x2B	Page Down
0x2C	,
0x2D	-
0x2E	.
0x2F	/
0x30	0
0x31	1
0x32	2
0x33	3
0x34	4
0x35	5
0x36	6
0x37	7
0x38	8
0x39	9
-
0x3B	;
-
0x3D	=
0x3E	~
0x3F	"
-
0x41	A
0x42	B
0x43	C
0x44	D
0x45	E
0x46	F
0x47	G
0x48	H
0x49	I
0x4A	J
0x4B	K
0x4C	L
0x4D	M
0x4E	N
0x4F	O
0x50	P
0x51	Q
0x52	R
0x53	S
0x54	T
0x55	U
0x56	V
0x57	W
0x58	X
0x59	Y
...
0x60	Enter/Return
0x61	Escape
0x62	Tab
0x63	Backspace
0x64	Caps Lock
0x65	Num Lock
-
0x67,0xhh,0xll	UCS-2 encoding (?) of code point 0xhhll? Win only
...
0x70	Shift
0x71	Right Shift
0x72	Control
0x73	Right Control
0x74	Alt, Meny, Option
0x75	Alt Gr, Right Option
0x76	Command
...
0x80	Mouse move up
0x81	Mouse move up+right
0x82	Mouse move right
0x83	Mouse move down+right
0x84	Mouse move down
0x85	Mouse move down+left
0x86	Mouse move left
0x87	Mouse move up+left
0x88	Mouse click
0x89	Mouse double click
0x8A	Mouse button down
0x8B	Mouse button up
0x8C	Mouse on
0x8D	Mouse off
0x8E	Mouse toggle
0x8F	Mouse right button click
0x90	Mouse right button double click
0x91	Mouse right button down
0x92	Mouse right button up
0x93	Mouse right button toggle
0x94	Mouse middle button click
0x95	Mouse middle button double click
0x96	Mouse middle button down
0x97	Mouse middle button up
0x98	Mouse middle button toggle
0x99	Mouse button 4 click
0x9A	Mouse button 4 double click
0x9B	Mouse button 4 down
0x9C	Mouse button 4 up
0x9D	Mouse button 4 toggle
0x9E	Mouse button 5 click
0x9F	Mouse button 5 double click
0xA0	Mouse button 5 down
0xA1	Mouse button 5 up
0xA2	Mouse button 5 toggle
0xA3	Mouse button 6 click
0xA4	Mouse button 6 double click
0xA5	Mouse button 6 down
0xA6	Mouse button 6 up
0xA7	Mouse button 6 toggle
0xA8	Mouse button 7 click
0xA9	Mouse button 7 double click
0xAA	Mouse button 7 down
0xAB	Mouse button 7 up
0xAC	Mouse button 7 toggle
0xAD	Mouse button 8 click
0xAE	Mouse button 8 double click
0xAF	Mouse button 8 down
0xB0	Mouse button 8 up
0xB1	Mouse button 8 toggle
0xB2	Wait. Pauses input for 1 second.
...
0xC0	Switch to overlay mode/level 0.
0xC1	Switch to overlay mode/level 1.
0xC2	Switch to overlay mode/level 2.
0xC3	Switch to overlay mode/level 3.
0xC4	Switch to overlay mode/level 4.
0xC5	Switch to overlay mode/level 5.
0xC6	Switch to overlay mode/level 6.
0xC7	Switch to overlay mode/level 7.
0xC8	Switch to overlay mode/level 8.
0xC9	Switch to overlay mode/level 9.
0xCA	Switch to overlay mode/level 10.
0xCB	Switch to overlay mode/level 11.
0xCC	Switch to overlay mode/level 12.
0xCD	Switch to overlay mode/level 13.
0xCE	Switch to overlay mode/level 14.
0xCF	Switch to overlay mode/level 15.
0xD0	Non repeating.
0xD1	Repeat last command.
0xD2	Non-smart typing. Not supported?
...
0xE0,0x32,0xrr	Set data send rate to 0xrr
0xE0,0x33	Display features
0xE0,0x41,0xrr	Set response rate to 0xrr
0xE0,0x42	Require lift off: on
0xE0,0x43	Require lift off: off
0xE0,0x44	Sound: off
0xE0,0x45	Sound: on
0xE0,0x47	Repeat: on
0xE0,0x48	Repeat: off
0xE0,0x49,0xrr	Set repeat rate to 0xrr
0xE0,0x4A	Repeat latching: on
0xE0,0x4B	Repeat latching: off
0xE0,0x4C	Shift latching
0xE0,0x4D	Shift locking
0xE0,0x4E	No shift latching
0xE0,0x51	3 Indicator lights
0xE0,0x52	6 Indicator lights
0xE0,0x53	Smart typing: On
0xE0,0x54	Smart typing: Off
0xE0,0x55,0xrr	Set mouse speed to 0xrr
0xE0,0x56	Ignored? Mouse arrow: On
0xE0,0x57	Ignored? Mouse arrow: Off
0xE0,0x58,0xrr	Ignored? Custom mode/level
0xE1,0x45	Reset to default settings
0xE1,0x53	Toggle smart typing