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gpm
***

* Menu:

* Overview::
* Server Invocation::
* Gpm Internals::
* The ClientLib::
* Demo Clients::
* Type Index::
* Function Index::
* Variable Index::

File: gpm.info,  Node: Overview,  Next: Server Invocation,  Prev: Top,  Up: Top

1 Overview
**********

The "gpm" package is a mouse server for the Linux console.  It is meant
to provide cooked mouse events to text-only applications, such as
editors and simple menu-based apps. The daemon is also able to repeat
packets in "msc" format to a graphic application.  This last feature is
meant to override the single-open problem of busmice.  The roots of
`gpm' come from the `selection-1.5' package, by Andrew Haylett.

   The first application to support the mouse has been The Midnight
Commander, by Miguel de Icaza.  `mc-0.11' and later releases offer
mouse support if you have the mouse server running on your system.  The
file `t-mouse.el' provides support for using the mouse from within
Emacs. *Note Emacs Support::.

   As of release 0.96, a default-handler is released with gpm, and can
be used to handle Control-Mouse events to draw menus on the screen.
The `gpm-root' program, however, needs kernel 1.1.73 or newer.  *Note
gpm-root::.

   Release 1.00 has been an incompatible one (is is incompatible with
releases older than 0.97), but is compatible with the kernel-level mouse
driver (available as `kmouse-?.??.tar.gz' from the mirrors of
`ftp://tsx-11.mit.edu'. With 1.0 the high level library is available,
together with a demonstration/test program. A small utility to help in
detecting your mouse-type is also included.

   As of release 1.20.0 the default device is removed. Now -m is a must.

   Release 1.20.1 introduces the must for -t and a specific way to use
-m,-t,-o: Now you've got to use -m first, then -t and at last -o.  This
seems to be more complex, but makes using of multiply mice possible with
clean code.

* Menu:

* Building the Release::

File: gpm.info,  Node: Building the Release,  Prev: Overview,  Up: Overview

1.1 Compiling and Installing
============================

Just say `./configure && make && make install' to your shell. You'll
need gpm installed to compile the latest release of The Midnight
Commander with mouse support enabled.

   Binaries are not released with the package because it's safer for
you to compile the package by yourself.

File: gpm.info,  Node: Server Invocation,  Next: Gpm Internals,  Prev: Overview,  Up: Top

2 Server Invocation
*******************

The `gpm' executable is meant to act like a daemon (thus, `gpmd' would
be a better name for it). This section is meant to describe the
command-line options for `gpm', while its internals are outlined in the
next section.  *Note Gpm Internals::.

   Due to restrictions in the `ioctl(TIOCLINUX)' system call, `gpm' must
be run by the superuser. The restrictions have been added in the last
1.1 kernels to fix a security hole related to selection and screen
dumping.

   The server can be configured to match the user's taste, and any
application using the mouse will inherit the server's attitude. From
release 1.02 up to 1.19.2 is was possible for any user logged on the
system console to change the mouse _feeling_ using the -q option. This
is no longer possible for security reasons.

   As of 0.97 the server program puts itself in the background. To kill
`gpm' you can just reinvoke it with the `-k' cmdline switch, although
`killall gpm' can be a better choice.

* Menu:

* Special Commands::
* Command Line::
* Bugs and Problems::
* Mouse Types::

File: gpm.info,  Node: Special Commands,  Next: Command Line,  Prev: Server Invocation,  Up: Server Invocation

2.1 Special Commands
====================

Version 1.10 adds the capability to execute _special_ commands on
certain circumstances. Special commands default to rebooting and halting
the system, but the user can specify his/her personal choice. The
capability to invoke commands using the mouse is a handy one for
programmers, because it allows to issue a clean shutdown when the
keyboard is locked and no network is available to restore the system to
a sane state.

   Special commands are toggled by triple-clicking the left and right
button - an unlikely event during normal mouse usage. The easiest way
to triple-click is pressing one of the buttons and triple-click the
other one. When special processing is toggled, a message appears on the
console (and the speaker beeps twice, if you have a speaker); if the
user releases all the buttons and presses one of them again within
three seconds, then the special command corresponding to the button is
executed.

   The default special commands are:

LEFT BUTTON
     Reboot the system by signalling the init process

MIDDLE BUTTON (IF ANY)
     Execute `/sbin/shutdown -h now'

RIGHT BUTTON
     Execute `/sbin/shutdown -r now'

   The `-S' command line switch enables special command processing and
allows to change the three special commands. To accept the default
commands use `-S ""' (i.e., specify an empty argument).  To specify
your own commands, use a colon-separated list to specify commands
associated to the left, middle and right button. If any of the commands
is empty, it is interpreted as `send a signal to the init process'. This
particular operation is supported, in addition to executing external
commands, because sometimes bad bugs put the system to the impossibility
to fork; in these rare case the programmer should be able to shutdown
the system anyways, and killing init from a running process is the only
way to do it.

   As an example, `-S ":telinit 1:/sbin/halt"', associates killing init
to the left button, going single user to the middle one, and halting
the system to the right button.

   System administrators should obviously be careful about special
commands, as gpm runs with superuser permissions. Special commands are
best suited for computers whose mouse can be physically accessed only by
trusted people.

File: gpm.info,  Node: Command Line,  Next: Bugs and Problems,  Prev: Special Commands,  Up: Server Invocation

2.2 Command Line Options
========================

Available command line options are the following:

`-a ACCEL'
     Set the acceleration value used when a single motion event is
     longer than DELTA (see `-d').

`-A[LIMIT]'
     Start up with selection pasting disabled.  This is intended as a
     security measure; a plausible attack on a system seems to be to
     stuff a nasty shell command into the selection buffer (`rm -rf /')
     including the terminating line break, then all the victim has to
     do is click the middle mouse button ..  As of version 1.17.2, this
     has developed into a more general aging mechanism; the gpm daemon
     can disable (_age_) selection pasting automatically after a period
     of inactivity.  To enable this mode just give the optional LIMIT
     parameter (no space in between !)  which is interpreted as the
     time in seconds for which a selection is considered valid and
     pastable.  As of version 1.15.7, a trivial program called
     `disable-paste' is provided. The following makes a good addition
     to `/etc/profile' if you allow multiple users to work on your
     console.

     `case $( /usr/bin/tty ) in
     /dev/tty[0-9]*) /usr/bin/disable-paste ;;
     esac'

`-b BAUD'
     Set the baud rate.

`-B SEQUENCE'
     Set the button sequence. `123' is the normal sequence, `321' can
     be used by left-handed people, and `132' can be useful with
     two-button mice (especially within Emacs). All the button
     permutations are allowable.

`-d DELTA'
     Set the delta value. When a single motion event is longer than
     DELTA, ACCEL is used as a multiplying factor. (Must be 2 or above)

`-D'
     Do not automatically enter background operation when started, and
     log messages to the standard error stream, not the syslog
     mechanism.  This is useful for debugging; in previous releases it
     was done with a compile-time option.

`-g NUMBER'
     With glidepoint devices, emulate the specified button with tapping.
     NUMBER must be `1', `2', or `3', and refers to the button number
     _before_ the `-B' button remapping is performed.  This option
     applies to the mman and ps2 decoding. No button is emulated by
     default because the ps2 tapping is incompatible with some normal
     ps2 mice

`-h'
     Print a summary of command line options.

`-i INTERVAL'
     Set INTERVAL to be used as an upper time limit for multiple
     clicks. If the interval between button-up and button-down events
     is less than LIMIT, the press is considered a double or triple
     click. Time is in milliseconds.

`-k'
     Kill a running gpm. This can be used by busmouse users to kill gpm
     before running X (unless they use `-R' or the single-open
     limitation is removed from the kernel).

`-l CHARSET'
     Choose the `inword()' look up table. The CHARSET argument is a
     list of characters. `-' is used to specify a range and `\ ' is
     used to escape the next character or to provide octal codes.  Only
     visible character can appear in CHARSET because control characters
     can't appear in text-mode video memory, whence selection is cut.

`-m FILENAME'
     Choose the mouse file to open. Must be before -t and -o.

`-M'
     Enable multiple mode. The daemon will read two different mouse
     devices.  Any subsequent option will refer to the second device,
     while any preceding option will be used for the first device. This
     option automatically forces the _repeater_ (`-R') option on.

`-o LIST-OF-EXTRA-OPTIONS'
     The option works similary to the "-o" option of mount; it is used
     to specify a list of "extra options" that are specific to each
     mouse type. The list is comma-separated. The options `dtr', `rts'
     or `both' are used by the serial initialization to toggle the
     modem lines like, compatibly with earlier gpm versions; note
     however that using -o dtr associated with non-plain-serial mouse
     types may now generate an error. *Note Mouse Types::.  And by the
     way, use -o after -m and after -t.

`-p'
     Forces the pointer to be visible while selecting. This is the
     behaviour of `selection-1.7', but it is sometimes confusing.  The
     default is not to show the pointer, which can be confusing as well.

`-r NUMBER'
     Set the responsiveness. A higher responsiveness is used for a
     faster cursor motion.

`-R[NAME]'
     Causes `gpm' to act as a repeater: any mouse data received while
     in graphic mode will be produced on the fifo `/dev/gpmdata' in
     protocol NAME, given as an optional argument (no space in between
     !).  In principle, you can use the same names as for the `-t'
     option, although repeating into some protocols may not be
     implemented for a while.  *Note Mouse Types::.  In addition, you
     can specify `raw' as the NAME, to repeat the mouse data byte by
     byte, without any protocol translation.  If NAME is omitted, it
     defaults to `msc'.  Using gpm in repeater mode, you can configure
     the X server to use its fifo as a mouse device. This option is
     useful for bus-mouse owners to override the single-open
     limitation. It is also an easy way to manage those stupid
     dual-mode mice which force you to keep the middle button down
     while changing video mode. The option is forced on by the `-M'
     option.

`-s NUMBER'
     Set the sample rate for the mouse device.

`-S COMMANDS'
     Enable special-command processing, and optionally specify custom
     commands as a colon-separated list. See above for a detailed
     description of special commands.

`-t NAME'
     Set the mouse type. Use `-t help' to get a list of allowable
     types. Since version 1.18.1, the list also shows which protocols
     are available as repeaters (see -R above), by marking them with an
     asterisk ("*").  *Note Mouse Types::.  Use -t after you selected
     the mouse device with -m.

`-v'
     Print version information and exit.

`-2'
     Force two buttons. This means that the middle button, if any, will
     be taken as it was the right one.

`-3'
     Force three buttons. By default the mouse is considered to be a
     2-buttons one, until the middle button is pressed. If three
     buttons are there, the right one is used to extend the selection,
     and the middle one is used to paste it.  Beware: if you use the
     `-3' option with a 2-buttons mouse, you won't be able to paste the
     selection.


* Menu:

* Bugs and Problems::

File: gpm.info,  Node: Bugs and Problems,  Next: Mouse Types,  Prev: Command Line,  Up: Server Invocation

2.3 Bugs and Problems
=====================

The `gpm' server may have problems interacting with X: if your mouse is
a single-open device (i.e. a bus mouse), you should kill `gpm' before
starting X, or use the `-R' option (see above).  To kill `gpm' just
invoke `gpm -k'. This problem doesn't apply to serial mice.

   Two instances of gpm can't run on the same system. If you have two
mice use the `-M' option (see above).

   While the current console is in graphic mode, `gpm' sleeps until
text mode is back (unless `-R' is used). Thus, it won't reply to
clients. Anyways, it is unlikely that mouse-eager clients will spur out
in hidden consoles.

   The clients shipped out with gpm are not updated, thus there are
potential security risks when using them.

File: gpm.info,  Node: Mouse Types,  Prev: Bugs and Problems,  Up: Server Invocation

2.4 Mouse Types
===============

This section of the gpm documentation manual describes the various
pointer types currently available in gpm. If you look at the source
code, you'll find that pointer-specific code is confined to `mice.c'
(while it used to only include mouse decoders, gpm now supports tablets
and touchscreens as well).

   The mouse type is specified on command line with the `-t' option.
The option takes an argument, which represents the name of a mouse
type. Each type can be associated to different names. For old mouse
types, one name is the old selection-compatible name, and another is
the XFree name. After version 1.18.1 of gpm, the number of synonyms was
made arbitrary and the actual name being used is made available to the
function responsible for mouse initialization. Therefore it is possible
for a mouse decoder to behave slightly differently according to the
name being used for the device (if this feature was already present, we
wouldn't have for example ms+ and ms+lr as different mouse types).

   The initialization procedure of each mouse type can also receive
extra option, by means of the -o command line option. Since
interpretation of the option string is decoder-specific, the allowed
options are described in association to each mouse type. When no
description of option strings is provided, that means the option string
is unused for that mouse type and specifying one generates an error.
When the document refer to "standard serial options" it means that one
of -o dtr, -o rts, -o both can be specified to toggle the control lines
of the serial port.

   The following mouse type are corrently recognized:

`bare Microsoft'
     The Microsoft protocol, without any extension. It only reports two
     buttons. If your device has three, you should either try running
     the mman decoder or msc. In the latter case, you need to tell the
     mouse to talk msc protocol by toggling the DTR and RTS lines (with
     one of -o drt, -o rts or -o both) or invoking `gpm -t msc' while
     keeping the middle button pressed. Very annoying, indeed.  This
     mouse decoder accepts standard serial options, although they
     should not be needed.

`ms'
     This is the original Microsoft protocol, with a middle-button
     extension.  Some old two-button devices send some spurious packets
     which can be misunderstood as middle-button events. If this is
     your case, use the `bare' mouse type.  Some new two-button devices
     are "plug and play", and they don't play fair at all; in this case
     try -t pnp.  Many (most) three-button devices that use the
     microsoft protocol fail to report some middle-button events during
     mouse motion.  Since the protocol does not distinguish between the
     middle button going up and the middle button going down it would
     be liable to get out of step, so this decoder declares the middle
     button to be up whenever the mouse moves. This prevents dragging
     with the middle button, so you should probably use `-t ms+lr'
     instead of this decoder, especially if you want to use X.  This
     mouse decoder accepts standard serial options, although they
     should not be needed.

`ms+'
     This is the same as `-t ms' except that the middle button is not
     reset during mouse motion. So you can drag with the middle button.
     However, if your mouse exhibits the usual buggy behaviour the
     decoder is likely to get out of step with reality, thinking the
     middle button is up when it's down and vice versa.  You should
     probably use `-t ms+lr' instead of this decoder.  This mouse
     decoder accepts standard serial options, although they should not
     be needed.

`ms+lr'
     This is the same as `-t ms+' except that there is an additional
     facility to reset the state of the middle button by pressing the
     other two buttons together. Do this when the decoder gets into a
     confused state where it thinks the middle button is up when it's
     down and vice versa. (If you get sick of having to do this, please
     don't blame gpm; blame your buggy mouse! Note that most
     three-button mice that do the microsoft protocol can be made to do
     the MouseSystems protocol instead. The "3 Button Serial Mouse
     mini-HOWTO" has information about this.)  This mouse decoder
     accepts standard serial options, although they should not be
     needed.

`msc MouseSystems'
     This is the standard protocol for three-button serial devices.
     Some of such devices only enter MouseSystem mode if the RTS, DTR
     or both lines are pushed low. Thus, you may try -t msc associated
     with -o rts, -o dtr or -o both.

`mman Mouseman'
     The protocol used by the new Logitech devices with three buttons.
     It is backward compatible with the Microsoft protocol, so if your
     mouse has three buttons and works with -t ms or similar decoders
     you may try -t mman instead to use the middle button.  This mouse
     decoder accepts standard serial options, although they should not
     be needed.

`sun'
     The protocol used on Sparc computers and a few others.  This mouse
     decoder accepts standard serial options, although they should not
     be needed.

`mm MMSeries'
     Title says it all.  This mouse decoder accepts standard serial
     options, although they should not be needed.

`logi Logitech'
     This is the protocol used by old serial Logitech mice.

`bm BusMouse'
     Some bus devices use this protocol, including those produced by
     Logitech.

`ps2 PS/2'
     The protocol used by most busmice.

`ncr'
     This `type' is able to decode the pointing pen found on some
     laptops (the NCR 3125 pen)

`wacom'
     The protocol used by the Wacom tablet. Since version 1.18.1 we
     have a new Wacom decoder, as the old one was not working with new
     tablets. This decoder was tested with Ultrapad, PenPartner, and
     Graphire tablets.  Options: -o relative (default) for relative
     mode, -o absolute for absolute mode.

`genitizer'
     The \"Genitizer\" tablet, in relative mode.  This mouse decoder
     accepts standard serial options, although they should not be
     needed.

`logim'
     Used to turn Logitech mice into Mouse-Systems-Compatible.
     Obviously, it only works with some of the Logitech mice.

`pnp'
     This decoder works with the new mice produces by our friend Bill,
     and maybe with the old ones as well. The Pnp protocol is hardwired
     at 1200 baud and is upset by normal initialization, so this is a
     -t bare decoder with no initialization at all.  This mouse decoder
     accepts standard serial options, although they should not be
     needed.

`ms3'
     A decoder for the new serial IntelliMouse devices, the ones with
     three buttons and a protocol incompatible with older ones. The
     wheel is currently unused.

`imps2'
     "IntelliMouse" on the ps/2 port. This type can also be used for a
     generic 2-button ps/2 mouse too, since it will auto-detect the
     type.

`netmouse'
     Decodes the "Genius NetMouse" type of devices on the ps/2 port.
     For serial "Netmouse" devices, use the "ms3" decoder.

`cal'
     A decoder of the "Calcomp UltraSlate device.

`calr'
     Same as above, but in relative mode.

`twid'
     Support for the twiddler keyboard. As of gpm-1.14 this decoder
     includes a char generator for the text console, but doesn't yet
     support X keycodes. If used with `-R', `gpm' will anyway repeat
     mouse events to the X server. More information about twiddler
     support can be found in `README.twiddler', in the gpm distribution.

`syn synaptics'
     A decoder for the Synaptics TouchPad connected to the serial port.
     This mouse decoder accepts standard serial options, although they
     should not be needed.

`synps2 synaptics_ps2'
     Same as above, but for the devices attached to the ps2 port.

`brw'
     A decoder for the Fellowes Browser, a device with 4 buttons and a
     wheel.  This mouse decoder accepts standard serial options,
     although they should not be needed.

`js Joystick'
     This mouse type uses the joystick device to generate mouse events.
     It is only available if the header `linux/joystick.h' is found at
     compile time. The header (and the device as well) has been
     introduced only during 2.1 development, and is not present in
     version 2.0 of the kernel.

`summa'
     This is a decode for the Symmagraphics of Genius tablet, run in
     absolute mode. A repeater is associated to this decoder, so it can
     -R summa can be used to generate X events even for other
     absolute-pointing devices, like touchscreens. To use the repeated
     data from X, you need a modified xf86Summa.o module.

`mtouch'
     A decoder for the MicroTouch touch screen. Please refer to the
     file `README.microtouch' in the source tree of gpm for further
     information. In the near future, anyways, I plan to fold back to
     this documentation the content of that file.

`gunze'
     A decoder for the gunze touch screen. Please refer to the file
     `README.gunze' in the source tree of gpm for further information.
     In the near future, anyways, I plan to fold back to this
     documentation the content of that file. The decoder accepts the
     following options: smooth=, debounce=. An higher smoothness
     results in slower motion as well; a smaller smoothness gives
     faster motion but, obviously, less smooth.  The default smoothness
     is 9. The debounce time is express in milliseconds and is the
     minimum duration of an up-down event to be taken as a tap. Smaller
     bounces are ignored.

`acecad'
     The Acecad tablet in absolute mode.

`wp wizardpad'
     Genius WizardPad tablet


File: gpm.info,  Node: Gpm Internals,  Next: The ClientLib,  Prev: Server Invocation,  Up: Top

3 Gpm Internals
***************

The server is organized as a main loop built around a `select()' system
call. It responds both to mouse events and to input from the clients,
which are connected to the server through a unix domain socket. The
connection is used to tell the server what a client is interested in,
and to get mouse events.

   When no clients are connected to the active console, the server runs
the selection mechanism (cut and paste of text).  The selection
mechanism is a simple and well-designed application, whose behaviour
can be cloned by clients, by telling the server to inherit the default
response for certain mouse events (motion being the most interesting).

* Menu:

* Events::
* Margins::
* Event Types::
* Connection Details::
* Default Handlers::

File: gpm.info,  Node: Events,  Next: Margins,  Prev: Gpm Internals,  Up: Gpm Internals

3.1 Events
==========

Whenever the mouse generates an event, the event is dispatched to the
active client for the current console, or to the default handler, if
present.  Otherwise selection is run. A default handler is a client
process which gets mouse events form all the virtual consoles.  *Note
Default Handlers::.

   When a client is involved, it is handled a `Gpm_Event' structure,
built by the server. The fields for `Gpm_Event' are the following:

`unsigned char buttons;'
     An or-mask of the values `GPM_B_LEFT', `GPM_B_MIDDLE' and
     `GPM_B_RIGHT'. It corresponds to the state of the mouse buttons
     when the event is reported. The current implementation of gpm
     allows at most three buttons.

`unsigned char modifiers;'
     The value of the kernel variable `shift_state', as of
     `keyboard.c', when the event is reported. It is a bitmask value,
     and corresponds to the least significant byte of the value used by
     the `loadkeys' program. Use of symbolic names in source code is
     available after inclusion of `linux/keyboard.h', as exemplified in
     `mev.c'.

`unsigned short vc;'
     The number of the active virtual console when the event is
     reported. The client is not expected to use this value, which
     corresponds to the controlling terminal of the client process,
     unless it gets events form multiple consoles.  *Note Default
     Handlers::.

`short x, y;'
     The position of the mouse pointer where the event is reported. It
     is 1-based by default, to be compatible with `selection' and
     `libcurses'.  This behavior can be overriden, though, by setting
     the library variable `gpm_zerobased'.  *Note Variables::.

`short dx, dy;'
     The change in position since the last reported event.

`enum Gpm_Etype type;'
     A bit-mask, representing the type of reported event, as described
     later.  *Note Event Types::.

`int clicks;'
     A counter, which is valid at button-down, drag or button-up. It
     can be 0, 1 or 2 to mean single, double or triple click.

`enum Gpm_Margin margin;'
     A bit-mask, telling if the pointer has gone out of the visible
     screen. The indivudual bits are named `GPM_TOP', `GPM_BOT',
     `GPM_LFT', `GPM_RGT'. Only one of them is active at a time, to
     allow using `switch' on the value. Vertical outrun takes
     precedence on horizontal outrun.  *Note Margins::.

File: gpm.info,  Node: Margins,  Next: Event Types,  Prev: Events,  Up: Gpm Internals

3.2 How margins are managed
===========================

Motion and button-press events are constrained to remain within the
visible screen. This means that the `x' will be within 1 and 80 and `y'
will be within 1 and 25 when the console is 80x25 cells. However, a
client can keep track of movements outside the screen, by using the
`dx' and `dy' fields, which aren't subject to clipping.

   The server helps applications in detecting margin conditions by
filling the `margin' field. Whenever the pointer tries to cross screen
boundaries, it is forced to remain on the border, but a flag is set in
`margin'.

   A different policy is in force for drag and button-release events.
In this case the pointer is allowed to go outside the physical screen
by exactly one position. This allows, for example, selecting to end of
line by dragging down-left. The peculiar situation is nonetheless
signaled through the `margin' flags. The client should be careful to
fit the values within the screen if needed.  *Note Utility Functions::.

File: gpm.info,  Node: Event Types,  Next: Connection Details,  Prev: Margins,  Up: Gpm Internals

3.3 Event Types
===============

The `type' field in `Gpm_Event' is made up of bit-wide flags. The
existing bit masks belong to two groups: bare events and cooked events.
The bit-mask `GPM_BARE_EVENTS' is provided to extract bare events, by
and-ing (`&') it with the `type' field.  For any event, exactly one bit
will be set in the resulting bitmask.

   Bare events are the following:

`GPM_MOVE'
     A motion event, with all buttons up.

`GPM_DRAG'
     A motion event, but one or more buttons are kept pressed.

`GPM_DOWN'
     A button press event. The `buttons' field will report which
     buttons are pressed after the event.

`GPM_UP'
     A button release event. The `buttons' field will report which
     buttons are being released. Note that this is different from the
     previous case.

`GPM_ENTER'
     This means "enter in the current Region of Interest", and such
     event can only happen if the high-level library is used.  When the
     type is `GPM_ENTER', all the other fields are undefined.  *Note
     High Level Lib::.

`GPM_LEAVE'
     This is only delivered by the high level library, too. Events of
     type `GPM_LEAVE' have all other fields undefined.

   Cooked events are the following:

`GPM_SINGLE'
     This bit may be set at button-press, drag and button release
     events, and can be used to identify a single press. The time
     interval used to choose a double click from two single clicks is
     set by a parameter in the daemon (configurable at daemon
     invocation).

`GPM_DOUBLE'
     Used to identify a double click (press, drag, release)

`GPM_TRIPLE'
     Used to identify a triple click (press, drag, release)

`GPM_MFLAG'
     The "motion flag" is true if some dragging happened between
     button-press and button-release. It can be used by those
     applications which respond to events at button release.  It is
     available at drag and release.

File: gpm.info,  Node: Connection Details,  Next: Default Handlers,  Prev: Event Types,  Up: Gpm Internals

3.4 Connection Details
======================

Each virtual console has a stack of clients attached to it. They talk to
gpm by writing to a control socket and get mouse events by reading it.
All the clients in the stack can receive events. Gpm-1.10 and earlier
only sent events to the top client, but sometimes users play with
multiple programs using suspend-resume (thanks Ian).

   In addition to the per-console stacks, another stack is there to
store default-handling clients.  *Note Default Handlers::.

   Each client registers with the server and tells which events it is
interested in. Events not managed by the client can be handled by the
selection mechanism, which is compiled in the server itself. This
approach simplifies writing clients which respond only to button
press/release events, because highlighting the mouse pointer can be
performed by the server. A default handler in turn can respond only to
mouse events associated with modifier keys, so that selection is used
for any mouse-only event.

   Clients are required to fill a `Gpm_Connect' structure and pass it
to the server. The structure is made up by four `unsigned int' fields.
*Note Open and Close::.

`eventMask'
     A bitmask of the events the client wants to receive. Both bare and
     cooked events are allowed to appear in the mask.

`defaultMask'
     A mask to tell which events allow a default treatment (the
     selection one). These are mouse events, independent of the
     modifier keys.

`minMod'
     The minimum amount of modifiers required by the client. This field
     is used for default-handlers which manage control-mouse events
     without interfering with mouse-only ones.  *Note Default
     Handlers::.

`maxMod'
     The maximum amount of modifiers the client is willing to receive.
     Events featuring a modifier key not included in `maxMod' won't be
     passed to the client.
   Two more fields are there to tell about the connection itself, and
you're not asked to fill them, because `Gpm_Open' will do it for you.

`int pid'
     The process id of the connecting application.

`int vc'
     Which virtual console to gain control of.

   Keyboard modifiers are used to multiplex clients on the same virtual
console. You (as a programmer) don't need to care about the internal
workings.  They are detailed in *note Default Handlers::, but you only
need to choose the right values for your application.

   Examples:
`minMod=0; maxMod=0;'
     specifies a client which senses mouse-only events, but neither
     shift-mouse nor alt-mouse nor control-mouse.

`minMod=0; maxMod=~0;'
     is a client which gets any mouse event.

`minMod=1<<KG_SHIFT; maxMod=1<<KG_SHIFT;'
     is a client which senses all shift-mouse events and nothing more.

`minMod=1<<KG_SHIFT; maxMod=~0;'
     is a client interested in shift-and-whatever-else mouse events,
     but disregarding mouse-only events.

   If the modifier keys in the event are too few or too many, the event
won't be reported to the client. If the modifiers are right but the
current event is not part of the `eventMask', it is not reported as
well. If the event is not used by the client, it can nonetheless be
passed to another client (a default handler or the internal selection
mechanism), according to the `defaultMask'.  If the event has been
already reported to the current application, it will also be passed
along the chain, if the GPM_HARD bit is set the `defaultMask'.

   Good values for `defaultMask' can thus be the following:

`0'
     To sink any event, even those I don't use.

`~eventMask'
     Pass along any event I don't use.

`~GPM_HARD'
     Just the same, independently of `eventMask'.

`GPM_MOVE|GPM_HARD'
     Pass motion events, even if I use them.  This is the good choice
     for an application which wants information on mouse motion, but
     leaves the task of cursor-drawing to the server.

File: gpm.info,  Node: Default Handlers,  Prev: Connection Details,  Up: Gpm Internals

3.5 Default Handlers
====================

In addition to console-specific clients, `gpm' allows for
console-independent clients - those clients which handle events ignored
by conventional clients

   Keyboard modifiers are used to multiplex the different clients on the
same console, and a default handler should specify a non-zero minimum
modifier set.

   To summarize, events which get to the server can be delivered to the
following _clients_, in the order of decreasing priority:

  1. The current client for the current console, if any.

  2. The default handler, if any.

  3. The builtin `selection' mechanism.

   A keyboard modifier which connected with a `minMod' equal to the
"Control" modifier and a `maxMod' of `~0' (all bits on), will then get
any event including the control key, if the application disregards it.

   This means that if the foreground application gets only the "Meta"
key, control-mouse is sufficient to invoke the default handler. If the
application gets control-mouse but disregards "Meta", conversely,
meta-control-mouse will invoke the default handler, and meta-mouse will
be delivered to selection.

   Both the `minMod' and `maxMod' fields are bitmasks, and their values
are bitwise or-ed and and-ed with the current modifier mask.

   `gpm-root' is an example of default handler. It gets control-mouse
events by default, and reads user-specific configuration files in order
to draw menus on the background of your screen.  *Note gpm-root::.

File: gpm.info,  Node: The ClientLib,  Next: Demo Clients,  Prev: Gpm Internals,  Up: Top

4 The Client Library
********************

The `libgpm.a' archive is meant to provide the mouse protocol at
different levels of abstraction. Applications linking to the `gpm'
server are expected to benefit from using the library, as compared to
managing the raw socket interface. Any source file using the library
should include `gpm.h' to get gpm specific macros and prototypes.

   Delivery of events within the library makes heavy use of the concept
of "Handling Function" (or "handler", for short).

* Menu:

* Handling Functions::
* Low Level Library::
* High Level Lib::
* Xterm::

File: gpm.info,  Node: Handling Functions,  Next: Low Level Library,  Prev: The ClientLib,  Up: The ClientLib

4.1 Handling Functions
======================

A mouse handler is a function which registers itself within the
library, and is called whenever a mouse event is reported to the
application. It is passed two arguments and returns an integer value,
according to the following typedef:

   `typedef int Gpm_Handler(Gpm_Event *EVENT, void *CLIENTDATA);'

   The EVENT is used to instantiate the mouse event just received, and
the CLIENTDATA pointer is needed to implement some higher level
functionality. An handler will be typically invoked by `Gpm_Getc', or
by the high-level library, and the following discussion assumes the
invoking function is `Gpm_Getc' (the high-level library only runs on
behalf of `Gpm_Getc').

   Handling functions can do whatever they want to, and return to the
caller an integer value, which can be used to generate a keyboard
event. This feature is useful in that often the mouse is a shortcut for
something which could be made by means of the keyboard.

   The application main loop can detect if the keyboard event is a
physical or generated one by looking at the global variable
`gpm_hflag', which is not zero only for handler-generated events.

   An handling function can generate more than one key in response of a
single mouse event. If it sets the global variable `gpm_morekeys' to a
non-zero variable before returning, it will be invoked again without
waiting for mouse events. You can use `gpm_morekeys' as a counter of how
many times you want to be called again - the client library only
compares it to zero.

   The return value from an handler is used as follows:

`EOF'
     This value is used to signal a fatal error, and will cause
     `Gpm_Getc' to return the same value to the caller, after setting
     `gpm_hflag' to 1.

`0'
     A zero return value means that `Gpm_Getc' should go on as before,
     without returning to the caller. The event has been eaten by the
     handler and no key-press is simulated.

`ANYTHING-ELSE'
     Any other value is considered a simulated character, and is
     returned to the caller after setting `gpm_hflag'.  This allows a
     quick way to implement yes/no boxes and simple menus without
     interfering with the main body of an existing application.
     Moreover, if return values greater than 255 are used a single
     switch loop can parse both keyboard and mouse events.

A mouse handler is passed as second argument the content of the
`gpm_data' variable, i.e. the current clientdata. The clientdata is
almost unuseful unless you use the high-level library, because it holds
a static value. Delivering the clientdata however allows the high-level
management of mouse events to be a superset of the low-level code,
rather than an incompatible alternative.

File: gpm.info,  Node: Low Level Library,  Next: High Level Lib,  Prev: Handling Functions,  Up: The ClientLib

4.2 Low Level Library
=====================

The library offers utility functions to establish the connection and to
get mouse events. They are designed to work painlessly if the server is
not running on the host machine. Xterm support is available as well.
*Note Xterm::.

* Menu:

* Variables ::
* Open and Close::
* Getting Events::
* Utility Functions::
* Extra Functions::

File: gpm.info,  Node: Variables,  Next: Open and Close,  Prev: Low Level Library,  Up: Low Level Library

4.2.1 Global Variables
----------------------

This is the list of all the global variables present in the client
library:

`int gpm_flag'
     Initially zero, it is used to tell if the process is connected
     with a mouse server or not. It is used as a counter to manage
     multiple opens as well.

`int gpm_tried'
     A flag, used to avoid retrying a connection if the server is not
     available on the system.

`int gpm_fd'
     Initially `-1', it is the file descriptor used to talk with the
     server. If we run under xterm, it will be -2.

`int gpm_zerobased'
     Since selection and curses has always been one-based, this
     variable, zero by default, can be used to trigger zero-based
     coordinates in event reporting. It must be set before opening the
     mouse connection, and never changed later.  *Note Events::.

`int gpm_visiblepointer'
     If not zero, causes the mouse cursor to be always visible on the
     window. It is zero by default.

`gpm_mx'
`gpm_my'
     These variables (max X and max Y) are used when fitting events
     inside the screen.  They are initialized by `Gpm_Open', and
     updated by a `SIGWINCH' handler internal to the library.  (Don't
     worry, the library doesn't _replace_ any `SIGWINCH' handler your
     program may already have installed; instead the library _hooks_
     the signal, that is, it calls any preexisting handler after taking
     care of its own needs.)

`int gpm_hflag'
     Used to signal if a character has been generated by a mouse
     handler.  *Note Handling Functions::.

`Gpm_Handler *gpm_handler; void *gpm_data'
     Both initially `NULL', they're used to setup asynchronous mouse
     handling, as described below under the `Gpm_Getc()' item.

`gpm_morekeys'
     Used by the mouse handler to provide more than one key: if
     `gpm_morekeys' is not zero, `Gpm_Getc' will invoke the handler
     without waiting for events. `gpm_morekeys' is never set by the
     mouse library.

File: gpm.info,  Node: Open and Close,  Next: Getting Events,  Prev: Variables,  Up: Low Level Library

4.2.2 Connecting and Disconnecting
----------------------------------

 -- Function: int Gpm_Open (Gpm_Connect *CONN, int FLAG);
     Open a connection with the server.  The CONN parameter points to
     the connection information for the being-created connection, as
     already described.  *Note Connection Details::.  It is passed to
     the server after filling the `pid' and `vc' fields.

     FLAG should be `0' for normal applications, those interested in
     events related to their own console. The own console is considered
     to be the one attached to `stdin', and it must match the string
     `/dev/tty*'. A negative value for FLAG is used to make the
     invoking application a default handler *note Default Handlers::,
     while a positive value is used to force connection to a particular
     console, either for debugging issues or whenever `stdin' is not a
     tty when `Gpm_Open' is invoked.

     Multiple opens are allowed, and a stack of `Gpm_Connect' structures
     is managed by the library. You can, thus, re-open the connection in
     order to temporarily change the range of events you're interested
     in. When you invoke an external program, for example, you should
     re-open the connection with `eventMask' zeroed, and `defaultMask',
     `minMod' and `maxMod' all equal to `~0'.

     The return value is either `-1' or the file descriptor used to
     communicate with the server. When run under xterm, a gpm client
     gets event through `stdin', and the return value for `Gpm_Open()'
     will be `-2'.  This value is always available in `gpm_fd'.

 -- Function: int Gpm_Close (void);
     Pops the connection stack. It is used to restore the previous
     situation after a change in the connection masks. Closes the
     actual connection when the stack gets empty. On last close it
     returns 0, -1 otherwise.

File: gpm.info,  Node: Getting Events,  Next: Utility Functions,  Prev: Open and Close,  Up: Low Level Library

4.2.3 Getting Events
--------------------

 -- Function: int Gpm_GetEvent (Gpm_Event *EVENT);
     Reads an event form `gpm_fd'. It should be called only when the
     `gpm_fd' descriptor is reported as readable by a `select()' system
     call, or it will block until an event arrives (unless you put the
     mouse file in non-blocking mode). It returns 1 on success, -1 on
     failure, and 0 after closing the connection. Failure can happen if
     a signal interrupted the read system call. This function doesn't
     work with xterm mouse reporting and is meant for internal use by
     the library.

 -- Function: int Gpm_CharsQueued (void);
     It returns the number of characters (contained in `nbprevchar'
     index) queued into the array `prevchar' by function `Gpm_Getc'.
     This call is useful i.e. in recognition of function or arrow keys,
     when we need to know the next character read by `Gpm_getc' in
     order to subsequently get it.

 -- Function: int Gpm_CharsQueued (void);
     It returns the number of characters (contained in `nbprevchar'
     index) queued into the array `prevchar' by function `Gpm_Getc'.
     This call is useful i.e. in recognition of function or arrow keys,
     when we need to know the next character read by `Gpm_getc' in
     order to subsequently get it.

 -- Function: int Gpm_Getc (FILE *F);
 -- Function: int Gpm_Getchar (void);
     These are intended to be replacements for `getc()' and `getchar()'
     to be used by applications which are interested in the mouse.
     Their external behaviour is the same as `getc()', but a mouse
     handler gets invoked whenever an event is available.  *Note
     Handling Functions::.  A mouse handler can force `Gpm_Getc' to
     return a specific value to the caller, and the "simulated"
     character is signaled by setting `gpm_hflag' to 1.

 -- Function: int Gpm_Wgetch (WINDOW *WIN);
 -- Function: int Gpm_Getch (void);
     These are intended to be replacements for `wgetch()' and `getch()'
     to be used by applications which are interested in the mouse. They
     are the curses equivalent of `Gpm_Getchar'.

File: gpm.info,  Node: Utility Functions,  Next: Extra Functions,  Prev: Getting Events,  Up: Low Level Library

4.2.4 Utility Functions
-----------------------

 -- Function: int Gpm_Repeat (int MILLISECS);
     It returns 1 if no mouse events arrive in the next MILLICECS
     milliseconds, 0 otherwise. It is meant to be used by those handlers
     which need to repeat an action as long as the mouse button is
     pressed (`while(Gpm_Repeat(200))...').

 -- Function: int Gpm_DrawPointer (int X, int Y, int FD);
 -- Function: int GPM_DRAWPOINTER (Gpm_Event *EPTR;)
     These are actually macros. They should be used to draw the mouse
     pointer after mangling the screen (while dragging on a menu, say),
     because letting it to the server won't work nicely, due to lack of
     synchronism between client and server. The file descriptor should
     refer to the console. The return value is 0 on success and -1 on
     failure. `Gpm_DrawPointer' is obsolete, and is retained only for
     compatibility.

 -- Function: int Gpm_FitValuesM (int *X, int *Y, int MARGIN);
 -- Function: int Gpm_FitValues (X,Y);
 -- Function: void Gpm_FitEvent (EPTR);
     The first is a function, while the other are macros.  Note that
     `Gpm_FitEvent' does not return values.  These three procedures
     should be used to fit the pointer inside the visible screen. They
     are needed for drag and release event. A connection bit will be
     available in the future to force the pointer in the visible region.

     Note that fitting uses `gpm_mx' and `gpm_my'.  *Note Variables::.

File: gpm.info,  Node: Extra Functions,  Prev: Utility Functions,  Up: Low Level Library

4.2.5 Extra Functions
---------------------

 -- Function: char* Gpm_GetLibVersion (int *WHERE);
     This function returns a pointer to a static storage representing
     the version number of the library. It is only available from
     0.98.2 onward, and returns a string like `"0.98.2"'. The third
     number is optional.  All numbers may be one or two digits. This
     behaviour changed in version 2.1.0 of libgpm. In releases before
     2.1.0 the second number was always reported as two digits. The
     WHERE pointer, if not null, is used to store a decimal number
     representing the version - 0.98.2 is 9802 and 2.1.1 is 20101.

 -- Function: char* Gpm_GetServerVersion (int *WHERE);
     This function returns a pointer to a static storage representing
     the version number of the server. The version is retrieved through
     `popen()', so it could fail (and return `NULL')if no `gpm' program
     is in the current path. Alternatively, it could fail (and return a
     wrong value) if the `gpm' in the path is not the currently running
     one.  The function is only available in the clientlibrary version
     0.98.2 or newer, but it works with any daemon, from 0.01 onward.
     The string returned can be parsed in the same way as for
     `Gpm_GetLibVersion()'. A preparsed version is stored in *WHERE if
     WHERE is not null. Both these functions do their calculations only
     the first time they are invoked.

 -- Function: int Gpm_GetSnapshot (Gpm_Event *EPTR);
     This function gives a non-blocking snapshot of the current
     situation: it returns the number of mouse buttons, as known to the
     server, or -1 if that information is not available (under Xterm,
     or before connecting).  If EPTR is not null, it is filled with
     information about the current state of the mouse. The fields have
     the following meaning: `x,y': current position of the cursor;
     `dx,dy' size of the window; `vc,modifiers' the current console and
     the current shift state; `buttons' which buttons are currently
     help down; `clicks' the number of clicks (0,1,2).  This function
     is only available from 0.98.2 onward, and will return -1 if run
     with an older server.

     Since this information travels on the same file descriptor as the
     events, and applications usually don't want to lose events, the
     function returns 0 if the input queue is not empty.


File: gpm.info,  Node: High Level Lib,  Next: Xterm,  Prev: Low Level Library,  Up: The ClientLib

4.3 High Level Library
======================

The high level library is part of the main `libgpm.a', but it acts at a
different level of abstraction. The high level library depends in the
low-level one, so if you link your application with any object of the
high-level library, you're forced to link in the low-level one too.

   If your application _only_ runs under xterm, please see `gpm-xterm'
in the `sample' subdirectory of the distribution, which offers all the
needed functionality.

   The main role of the high-level library is to define a way to manage
windows (or "Regions of Interest" on your text screen). The regions are
arranged in a stack, and event are delivered to the different windows
according to their position both on the stack and on the screen.  *Note
hltest::.

* Menu:

* Concepts::
* hl-Variables::
* hl-Functions::

File: gpm.info,  Node: Concepts,  Next: hl-Variables,  Prev: High Level Lib,  Up: High Level Lib

4.3.1 Concepts
--------------

The high-level library is completely independent of the low-level one,
so it uses `gpm_handler' and `gpm_data' as connection point with
`Gpm_Getc()'.

   All the functionality is based on the concept of RoI's. each RoI is
described by a `Gpm_Roi' structure, which is made up by the following
fields:

`short xMin, xMax'
     These numbers identify the upper-left corner of the region.  When
     events are reported to the region, the event coordinate will be
     relative to this position (zero-based).

`short yMin, yMax'
     These numbers identify the lower-right corner of the region.

`unsigned short minMod, maxMod'
     These modifier masks have the same role within the application as
     the same fields have in inter-application multiplexing.

`unsigned short eventMask'
     It is the mask of events which are to be reported to the current
     region.

`unsigned short owned'
     This is a bit, used to know if the region is owned by the library
     or the application, in order to issue `free(0' when needed.

`Gpm_Handler *handler'
     The function to be called when events are to be reported to the
     current region.

`void *clientdata'
     The clientdata to be passed to the handler

`Gpm_Roi *next, *prev'
     Links to the RoI chain.


File: gpm.info,  Node: hl-Variables,  Next: hl-Functions,  Prev: Concepts,  Up: High Level Lib

4.3.2 Variables
---------------

`Gpm_Roi* gpm_roi'
     The linked list of regions (pointer to the top one).

`Gpm_Roi* gpm_current_roi'
     The region which got the last event (used to generate enter and
     leave events).

`Gpm_Handler* gpm_roi_handler'
     This variable is meant to be set by the user. It is the catch-all
     region of interest, which will be called for any mouse event not
     falling within any registered region. If NULL, the event will be
     discarded.

`void* gpm_roi_data'
     the client data to be passed to `gpm_roi_handler'.

File: gpm.info,  Node: hl-Functions,  Prev: hl-Variables,  Up: High Level Lib

4.3.3 Functions
---------------

 -- Function: Gpm_Roi* Gpm_PushRoi (int XMIN, int YMIN, int XMAX, int
          YMAX,
     int MASK, Gpm_Handler *FUN, void *XTRADATA);

     This function pushes a Region of Interest on top of the stack,
     after allocating it and filling with the provided values. FUN is
     the function which will be called in order to handle events, and
     the roi itself will be passed to the function as clientdata. The
     Roi is represented by a `struct Gpm_Roi' structure, described in
     `gpm.h'.  The `xtradata' field will be used to fill the `xtradata'
     field in `Gpm_Roi'.  the return value is the Roi just pushed (i.e.
     the top of stack).

 -- Function: char* Gpm_UseRoi (Gpm_Roi *ROI);
     While `Gpm_PushRoi' has to allocate the Region before pushing it,
     this function passes a pre-allocated function to the stack manager.
     The return value is the Roi just used.

 -- Function: Gpm_Roi* Gpm_PopRoi (Gpm_Roi *ROI);
     Used to extract a Region of Interest from the stack, this function
     will also clear the Region if it is needed.

 -- Function: Gpm_Roi* Gpm_RaiseRoi (Gpm_Roi *WHICH, Gpm_Roi *BEFORE);
     Raise the specified roi, either before the second Roi or at top-of-
     stack (if BEFORE is `NULL'). The return value is the new
     top-of-stack.

 -- Function: Gpm_Roi* Gpm_LowerRoi (Gpm_Roi *WHICH, Gpm_Roi *AFTER);
     Lower the specified roi, either after the second Roi or at
     bottom-of- stack (if BEFORE is NULL). The return value is the new
     top-of-stack.

 -- Function: Gpm_Roi* Gpm_HandleRoi (Gpm_Event *EPTR, void *
          CLIENTDATA);
     This function, which should not be invoked by the user, is the
     dispatching manager within the application for mouse events. This
     function will browse the stack of regions of interest in order to
     notify windows about Enter and Leave events (if they are
     interested in them), and then delivers the current event to the
     relevant Roi.

     If no Roi is interested in he event the `*gpm_roi_handler' function
     is invoked (if not null), with null clientdata.

     Reported events are all those in `Gpm_Event', and also `GPM_ENTER'
     and `GPM_LEAVE'. These can be used to toggle highlighting on a
     button or to drop a menu if the menubutton is entered during a
     drag.  Remember that when Enter or Leave is notified, no other
     information in the event item should be used.


File: gpm.info,  Node: Xterm,  Prev: High Level Lib,  Up: The ClientLib

4.4 Running under `xterm'
=========================

As of release 0.18, gpm-based applications can run under xterm without
any need for recompilation. The library is designed to convert xterm
mouse events to gpm-style structures, so that the client will get the
same events it got under the Linux console. Moreover, a source file
`sample/gpm-xterm.c' is available to mimic libgpm under a different OS
than Linux. Porting to other text-based consoles is an open issue, but
I myself have Linux alone.

   The goal is to provide a uniform mouse interface with both xterm and
the Linux console. Some features of libgpm would not be available, but
if you run under xterm you know what you get, so you couldn't use them
on the console anyway.

   The `sample' directory in the distribution tree is meant to show how
a simple mouse-sensitive application can be easily autoconfigured and
compiled. The `rmev' program has proved to compile and run smoothly
under Linux (both with and without `libgpm.a'), SunOS-4, Solaris-5,
hpux-8.x and Ultrix-3.0.

File: gpm.info,  Node: Demo Clients,  Next: Type Index,  Prev: The ClientLib,  Up: Top

5 Demonstration Clients
***********************

* Menu:

* mev::
* sample/rmev::
* Emacs Support::
* gpm-root::
* hltest::
* mouse-test::

File: gpm.info,  Node: mev,  Next: sample/rmev,  Prev: Demo Clients,  Up: Demo Clients

5.1 `mev'
=========

The `mev' program is modeled after `xev'. It prints to `stdout' the
mouse console events it gets.

   `mev''s default behaviour is to get anything, but command line
switches can be used to set the various fields in the `Gpm_Connect'
structure, in order to customize the program's behaviour. I'm using
`mev' to handle mouse events to Emacs.  *Note Emacs Support::.

   Command line switches for `mev' are the following:

`-C NUMBER'
     Select a virtual console to get events from.  This is intended to
     be used for debugging.

`-d NUMBER'
     Choose a default mask. By default the server gets any events not
     belonging to the event mask. The mask can be provided either as a
     decimal number, or as a symbolic string.

`-e NUMBER'
     Choose the event mask. By default any event is received. The mask
     can be provided either as a decimal number, or as a symbolic
     string.

`-E'
     Enter emacs mode. In emacs mode events are reported as lisp forms
     rather than numbers. This is the format used by the t-mouse
     package within emacs.

`-f'
     Fit events inside the screen before reporting them. This options
     re-fits drag events, which are allowed to exit the screen border,
     *Note Margins::.

`-i'
     Interactive. Accepts input from `stdin' to change connection
     parameters.

`-m NUMBER'
     Choose the minimum modifier mask. Any event with fewer modifiers
     will not be reported to `mev'. It defaults to `0'.  The mask must
     be provided either as a decimal number, or as a symbolic string.

`-M NUMBER'
     Choose the maximum modifier mask. Any event with more modifier
     than specified will not be reported to `mev'.  It defaults to
     `\~0', i.e. all events are received.  The mask must be provided
     either as a decimal number, or as a symbolic string.

`-p'
     Requests to draw the pointer during drags. This option is used by
     emacs to avoid invoking `ioctl()' from lisp code.

   When the arguments are not decimal integers, they are considered
lists of alphanumeric characters, separated by a single non-alphanumeric
character. I use the comma (`,'), but any will do.

   Allowed names for events are `move', `drag', `down' or `press', `up'
or `release', `motion' (which is both `move' and `drag'), and `hard'.

   Allowed names for modifiers are `shift', `leftAlt', `rightAlt',
`anyAlt' (one or the other), `control'.

   When the `-i' switch is specified, `mev' looks at its standard input
as command lines rather than events. The input lines are parsed, and the
commands `push' and `pop' are recognized.

   The `push' command, then, accepts the options `-d', `-e', `-m' and
`-M', with the same meaning described above. Unspecified options retain
the previous value and the resulting masks are used to reopen the
connection with the server. `pop' is used to pop the connection stack.
If an empty stack is popped the program exits.

   Other commands recognized are `info', used to return the stack
depth; `quit' to prematurely terminate the program; and `snapshot' to
get some configuration information from the server.

File: gpm.info,  Node: sample/rmev,  Next: Emacs Support,  Prev: mev,  Up: Demo Clients

5.2 `sample/rmev'
=================

`rmev' is a reduced version of `mev', but it is designed to be as
portable as possible. It uses a subset of the capabilities of
`libgpm.a', but works smoothly on both xterm and the Linux console. It
is distributed with `gpm' to show how a curses based application can
support the mouse with a small effort. Most of the xterm decoding is by
Janne Kukonlehto.  *Note Xterm::.

File: gpm.info,  Node: Emacs Support,  Next: gpm-root,  Prev: sample/rmev,  Up: Demo Clients

5.3 Emacs Support
=================

Emacs support is quite complete as of 0.14.  The enclosed file
`t-mouse.el', also available in byte-compiled form, is used to pass
mouse events to emacs.  `t-mouse.elc' is installed in the correct
site-lisp directory for you emacs installation (as detected by the
configure phase).

   Events with modifiers other than Meta, Control, and Shift are not
managed by the library.  Managed events are passed to the lisp program,
which converts them to be similar to X mouse events inside emacs.
Actions are then invoked through a local keymap.

   In my own environment I can use mouse-only and meta mouse within
emacs, shift-mouse to run selection and control-mouse to run `gpm-root'.
*Note gpm-root::.

   I suggest to put the following form in your own `.emacs' file, to
avoid loading `t-mouse' when you aren't working on the Linux console:

     (if (and (string-match ".*-linux" system-configuration)
              (or (string-match "linux" (getenv "TERM"))
                  (string-match "con.*" (getenv "TERM"))))
         (load-library "t-mouse"))

   Mouse events are appended to the list variable
`unread-command-events' where the Emacs main event loop will find them.
They can be made to trigger any command (or interactive function, in
Emacs Lisp terminology) at all.  Actually Emacs already comes with
reasonable bindings for most mouse events, so usually you won't have to
do anything beyond installing `t-mouse'.  If you want to modify what
Emacs does in response to mouse events, please see *note Keymaps:
(elisp)Keymaps.

   The scrollbar sits on the last column of the screen, though it is not
visible.  When you click on the last column, a scroll-bar action is
taken.  If this annoys you, again it can be turned off by changing the
appropriate Emacs keymap.

   If you kill the `gpm' server, Emacs won't respond to mouse events
any more. If the server is then restarted, you can invoke ``M-x
t-mouse-run'' to restart mouse responsiveness in the editor.

File: gpm.info,  Node: gpm-root,  Next: hltest,  Prev: Emacs Support,  Up: Demo Clients

5.4 The "gpm-root" program
==========================

The program `gpm-root' is designed to handle Control-Mouse events to
draw menus on the background of the current tty. The actual menus are
described by a configuration file in the user's home directory.

   Please note that `gpm-root' needs to run with Linux 1.1.73 or newer,
because previous kernels lack some screen handling capabilities
required by the program.

   The program uses the files `/dev/vcs*' to draw to the console screen.
These are available only from kernel 1.1.81 onward. If you miss those
device nodes, you should create them using `create_vcs' in the
distribution directory. The tool won't run with kernels older than
1.1.81, because they lacked a full screen dump/restore capability.

   Available command line options are the following:

`-m NUMBER'
     Choose the modifier to use (by default: `control'). The modifier
     can be provided either as a number or as a symbolic string.
     Allowed strings are `shift', `anyAlt', `leftAlt', `rightAlt',
     `control'.

`-u'
     Deny using user-specific configuration files. With this option on,
     only `/etc/gpm-root.conf' will be used as a source of
     configuration information. This option is intended for those
     system administrators who fear security could be broken by this
     daemon. Things should be sufficiently secure, but if you find a
     hole please tell me about it.

`-D'
     Do not automatically enter background operation when started, and
     log messages to the standard error stream, not the syslog
     mechanism.  This is useful for debugging; in previous releases it
     was done with a compile-time option.

`-V VERBOSITY INCREMENT'
     Raise the maximum level of messages that will be logged.  Thus a
     positive argument has the effect of making the program more
     verbose.  One can also give a negative argument to hush the
     program; however, note that due to getopt(3) rules a negative
     argument must follow the option with no space betwixt (that is,
     `-V-1' but not `-V -1').  *Note Program Arguments: (libc)Program
     Arguments.  The argument is optional and its default value is 1.


   Each time a menu is drawn, the configuration file is reparsed if it
has changed. This allows modification of personal setup without
reinvoking the daemon.

   The actual configuration file is better introduced by an example:

     # sample configuration file for gpm-root
     # edit it to suit your taste

     button 2 {
       name "system status"
       foreground red
       background black
       border yellow
       head bright yellow

       ""          f.nop
       "load: "    f.load
       "free:"     f.free
       "---------" f.nop
       "disk usage" f.bgcmd  "du | sort -rn > /tmp/du"
     }

     button 3 {
       name "jump"

       foreground black
       background red
       border bright yellow
       head bright yellow

       "tty1"  f.jptty  "1"
       "tty2"  f.jptty  "2"
       "tty3"  f.jptty  "3"
       "tty4"  f.jptty  "4"
       "tty5"  f.jptty  "5"
       "tty6"  f.jptty  "6"
         ""        f.nop
         "more of them..." {
               "tty 17" f.jptty  "17"
               }
      }

   The syntax for the file won't be described here, being it quite
apparent from the example above. Blanks and newlines are unused in
parsing the file, and the layout of the file is free. Comments are
allowed in the file: any hash mark (`#') found at the beginning of the
line or after white space makes the parser discard anything up to the
next line. To insert quotes (`"') in strings precede them with a
backslash.

   Note that recursive menus are allowed, to any level of recursion.

   Keywords belong to three groups: the button keyword, the cfg
keywords and the action keywords. They are all described in the table
below:

`button NUMBER MENU'
     The `button' keyword is used to introduce a menu. It is followed
     by the number of the relevant button (1=left, 2=middle, 3=right),
     an open brace, a menu and a closed brace.  A menu is made up of
     cfg statements, followed by action statements. Cfg statements can
     come in any order, while the order of action statements tells the
     actual order in which actions will appear on the screen, top to
     bottom.

   The following statements belong to the cfg set.

`name STRING'
     If the `name' keyword is present, the specified STRING will be
     used as the name for the current menu.

`background COLOR'
     This statements is used to specify the background color to be used
     in the current menu. The COLOR can be specified with one of the
     eight canonical strings `black', `red', `cyan' etc. The background
     defaults to black.

`foreground COLOR'
     This statements is used to specify the foreground color for menu
     items. Its value defaults to `white'.  An optional `bright'
     keyword can appear before the actual color.

`border COLOR'
     `border' is used to specify the border color for the menu. Its
     value defaults to `white'.  An optional `bright' keyword can
     appear before the actual color.

`head COLOR'
     `head' is used to specify the foreground color for the title of
     the menu. Its value defaults to `white'.  An optional `bright'
     keyword can appear before the actual color.

   The following statements belong to the action set.

`STRING f.fgcmd CMDSTRING'
     When the mouse button is released above the corresponding menu
     item, the CMDSTRING is pasted in the keyboard queue of the current
     console. This is not yet implemented.

`STRING f.bgcmd CMDSTRING'
     When the mouse button is released above the corresponding menu
     item, a shell (`/bin/sh') is forked to execute the specified
     command, with `stdin' connected to `/dev/null', and `stdout',
     `stderr' connected to the active console.

`STRING f.jptty TTYNUMBER'
     When the mouse button is released above the corresponding menu
     item, the console is switched to the one specified. The TTYNUMBER
     must be specified as a string. Any tty can be reached this way,
     even those which are not accessible via the keyboard.

`STRING f.mktty TTYNUMBER'
     When the mouse button is released above the corresponding menu
     item, an unused console is selected, and `/sbin/mingetty' is
     executed in it. The current console is switched to the newly
     opened console. I use this command to save kernel memory by
     opening a single console through `/etc/inittab' and requesting the
     others only when i need to login.

`STRING WHOLE-MENU'
     A menu can directly follow the label string.  When the mouse
     pointer leaves the menu frame at the level of STRING, a second
     menu is posted on screen.

`STRING f.lock'
     When the mouse button is released above the corresponding menu
     item, the keyboard and the screen are locked, and only the locking
     user or the superuser can unlock them. This is not yet implemented.

`STRING f.load'
     The current loadavg when the menu is posted is concatenated to
     STRING to build the actual message displayed on screen. Nothing
     happens at button release.

`STRING f.free'
     The free memory and swap when the menu is posted is concatenated
     to STRING to build the actual message displayed on screen. Nothing
     happens at button release.

`STRING f.time'
     The current time is formatted with strftime(3), according to
     STRING. The resulting string is the actual message displayed on
     screen. Nothing happens at button release.

`STRING f.pipe CMDLINE'
     When the mouse pointer leaves the menu frame at the level of
     STRING, a message box is posted on screen showing the last ten
     lines of the output of CMDLINE. CMDLINE is executed by `/bin/sh'.
     This is not yet implemented.

`STRING f.nop'
     This does nothing, it only displays STRING on the menu.

   The `HOME', `LOGNAME' and `USER' environment variables are setup to
the values for the invoking user before spawning an external process
(`f.bgcmd', `f.pipe'). The current directory is always `/'.

   Known bugs have been fixed. In particular, if you invoke `gpm-root'
right after `gpm', it will delay a few seconds before trying to connect
to the daemon.

File: gpm.info,  Node: hltest,  Next: mouse-test,  Prev: gpm-root,  Up: Demo Clients

5.5 `hltest'
============

High-level test is a simple sample application using the high-level
library. It implements something like a window manager for text windows,
though it is small and unuseful.

   The application is meant to be read by programmers trying to use the
high-level library. It is equipped with event reporting to help in
understanding the internal workings.

File: gpm.info,  Node: mouse-test,  Prev: hltest,  Up: Demo Clients

5.6 `mouse-test'
================

This experimental and incomplete application tries to help in detecting
which protocol does your mouse speak. It is able to detect MouseMan
devices, and to choose between `-t ms' (three-buttons aware) and `-t
bare' old two-buttons-only serial mice.

   I know the application is buggy, but I only own one mouse device.
If you are interested in this application, just call me and awake me
from my laziness.

File: gpm.info,  Node: Type Index,  Next: Function Index,  Prev: Demo Clients,  Up: Top

Type Index
**********

[index]
* Menu:

* Gpm_Connect:                           Connection Details.   (line 26)
* Gpm_Event:                             Events.               (line 13)
* Gpm_Handler:                           Handling Functions.   (line 11)
* Gpm_roi:                               Concepts.             (line 12)

File: gpm.info,  Node: Function Index,  Next: Variable Index,  Prev: Type Index,  Up: Top

API Index
*********

[index]
* Menu:

* Gpm_CharsQueued:                       Getting Events.       (line 17)
* Gpm_Close:                             Open and Close.       (line 34)
* GPM_DRAWPOINTER:                       Utility Functions.    (line 14)
* Gpm_DrawPointer:                       Utility Functions.    (line 13)
* Gpm_FitEvent:                          Utility Functions.    (line 25)
* Gpm_FitValues:                         Utility Functions.    (line 24)
* Gpm_FitValuesM:                        Utility Functions.    (line 23)
* Gpm_Getc:                              Getting Events.       (line 31)
* Gpm_Getch:                             Getting Events.       (line 42)
* Gpm_Getchar:                           Getting Events.       (line 32)
* Gpm_GetEvent:                          Getting Events.       (line  7)
* Gpm_GetLibVersion:                     Extra Functions.      (line  7)
* Gpm_GetServerVersion:                  Extra Functions.      (line 17)
* Gpm_GetSnapshot:                       Extra Functions.      (line 30)
* Gpm_HandleRoi:                         hl-Functions.         (line 40)
* Gpm_LowerRoi:                          hl-Functions.         (line 34)
* Gpm_Open:                              Open and Close.       (line  7)
* Gpm_PopRoi:                            hl-Functions.         (line 25)
* Gpm_PushRoi:                           hl-Functions.         (line  8)
* Gpm_RaiseRoi:                          hl-Functions.         (line 29)
* Gpm_Repeat:                            Utility Functions.    (line  7)
* Gpm_UseRoi:                            hl-Functions.         (line 20)
* Gpm_Wgetch:                            Getting Events.       (line 41)

File: gpm.info,  Node: Variable Index,  Prev: Function Index,  Up: Top

Variable Index
**************

[index]
* Menu:

* gpm_current_roi:                       hl-Variables.         (line 11)
* gpm_data:                              Variables.            (line 44)
* gpm_fd:                                Variables.            (line 16)
* gpm_flag:                              Variables.            (line  9)
* gpm_handler:                           Variables.            (line 44)
* gpm_hflag:                             Variables.            (line 40)
* gpm_morekeys:                          Variables.            (line 48)
* gpm_mx:                                Variables.            (line 30)
* gpm_my:                                Variables.            (line 30)
* gpm_roi:                               hl-Variables.         (line  7)
* gpm_roi_data:                          hl-Variables.         (line 20)
* gpm_roi_handler:                       hl-Variables.         (line 17)
* gpm_tried:                             Variables.            (line 12)
* gpm_visiblepointer:                    Variables.            (line 26)
* gpm_zerobased:                         Variables.            (line 20)