.TH MOUSE 3
.SH NAME
mouse, cursor \- kernel mouse interface
.SH SYNOPSIS
.nf
.B bind -a #m /dev

.B /dev/mouse
.B /dev/mousein
.B /dev/mousectl
.B /dev/cursor
.fi
.SH DESCRIPTION
The 
.I mouse
device provides an interface to the mouse.
There is also a cursor associated with the screen;
it is always displayed at the current mouse position.
.PP
Reading the
.B mouse
file returns the mouse status: its position and button state.
The read blocks until the state has changed since the last read.
The read returns 49 bytes: the letter 
.B m
followed by four decimal strings, each 11 characters
wide followed by a blank:
.I x
and
.IR y ,
coordinates of the mouse position in the screen image;
.IR buttons ,
a bitmask with the
1, 2, and 4 bits set when the
mouse's left, middle, and right buttons,
respectively, are down;
and
.IR msec ,
a time stamp, in units of milliseconds.
.PP
Writing the
.B mouse
file, in the same format,
causes the mouse cursor to move to the position specified by the
.I x
and
.I y
coordinates of the message.
The
.I buttons
and
.I msec
fields are ignored and may be omitted.
.PP
Writes to the 
.B mousein
file are processed as if they were generated by the
mouse hardware itself,
as extra mouse events to be processed and passed back via
the
.B mouse
file.
The
.B mousein
file, which is exclusive-use and may be opened
only by the host owner, is intended for controlling devices, such as USB mice,
that are managed by user-level software.
Each event should consist of
the letter
.B m
followed by delta
.IR x ,
delta
.IR y ,
and
.IR buttons
as space-separated decimal numbers.
.PP
Writing to the
.B mousectl
file configures and controls the mouse.
The messages are:
.TF ps2intellimouse
.TP
.B serial\fI n\fR
sets serial port
.I n
to be the mouse port.
.TP
.B ps2
sets the PS2 port to be the mouse port.
.TP
.B intellimouse
uses the wheel on a Microsoft Intellimouse
as the middle button.
.TP
.B ps2intellimouse
is equivalent to a write of
.B ps2
followed by a write of
.BR intellimouse .
.TP
.B accelerated
turns on mouse acceleration.
.TP
.B linear
turns off mouse acceleration
.TP
.B res \fIn\fR
sets mouse resolution to a setting between 0 and
3 inclusive.
.TP
.B hwaccel \fIon/off\fR
sets whether acceleration is done in hardware or
software.
By default, PS2 mice use hardware and serial mice use
software.
Some laptops (notably the IBM Thinkpad T23) don't
implement hardware acceleration for external mice.
.TP
.B swap
swaps the left and right buttons on the mouse.
.TP
.B scrollswap
swaps the buttons generated by the scroll wheel on the mouse.
.TP
.B buttonmap \fIxyz\fR
numbers the left, middle, and right mouse buttons
.IR x ,
.IR y ,
and
.IR z ,
respectively.
If
.I xyz
is omitted, the default map, 123, is used.
Thus in the default state writing
.B "buttonmap 321
swaps left and right buttons 
and writing
.B "buttonmap 123
or just
.B buttonmap
restores their usual meaning.
Note that
.B buttonmap 
messages are idempotent,
unlike
.BR swap .
.TP
.B reset
clears the mouse
to its default state.
.PD
.PP
Not all mice interpret all messages; with some devices,
some of the messages may be no-ops.
.PP
Cursors are described in 
.IR graphics (2).
When read or written from or to the
.B cursor
file, they are represented in a 72-byte binary format.
The first and second four bytes are little endian
32-bit numbers specifying the
.I x
and
.I y 
coordinates of the cursor 
.IR offset ;
the next 32 bytes are the
.B clr
bitmask,
and the last 32 bytes the
.B set
bitmask.
.PP
Reading from the
.B cursor
file returns the current cursor information.
Writing to the 
.B cursor
file sets the current cursor information.
A write of fewer than 72 bytes sets the
cursor to the default, an arrow.
.PP
The
.B mouse
and
.B cursor
files are multiplexed by
.IR rio (1)
to give the illusion of a private mouse to each of its clients.
The semantics are otherwise the same except that notification
of a window resize is passed to the application using a
.B mouse
message beginning with
.B r
rather than
.BR m ;
see
.IR rio (4)
for details.
.PP
To cope with pointing devices with only two buttons, when the
shift key is pressed, the right mouse button generates middle-button events.
.SH SOURCE
.B /sys/src/9/port/devmouse.c
.SH "SEE ALSO
.IR rio (4)
.SH BUGS
The cursor format is big endian while the
rest of the graphics interface is little endian.