NAME

FvwmMFL - the Fvwm3 front-loader module

SYNOPSIS

FvwmMFL can only be invoked by Fvwm3. Command line invocation of the FvwmMFL will not work.

This module has no command-line options.

DESCRIPTION

The FvwmMFL module provides access to Fvwm events over a unix-domain socket. This module is intended to provide externally-written programs (clients) the ability to receive information from Fvwm and to perform an action on that event.

The information from Fvwm3 is in the form of JSON packets. Each JSON packet has different fields, depending on the type requested.

COMMUNICATION

The default unix-domain socket for FvwmMFL is $TMPDIR/fvwm_mfl.sock, although this can be overridden via an environment variable FVWMMFL_SOCKET.

REGISTERING INTEREST

Commands can be sent to FvwmMFL to control which information is sent the client. The set command is used for this. The table below shows which events can be subscribed to.

Event	Description
new_window	Fired when a new window is mapped and visible.
map	Fired when a window is mapped.
configure_window	Fired when a window is moved or resized.
destroy_window	Fired when a window is closed.
new_page	Fired when a new page is switched to.
new_desk	Fired when a new desk is switched to.
raise_window	Fired when a window is raised (or changes layer).
lower_window	Fired when a window is lowered (or changed layer).
focus_change	Fired when a window loses/gains focus.
enter_window	Fired when a window has the pointer moved into it.
leave_Window	Fired when a window has pointer moved out of it.
window_shade	Fired when a window is shaded.
window_unshade	Fired when a window is unshaded.
window_name	Fired when the window name changes.
visible_name	Fired when the visible window name changes.
res_class	Fired when the class of the window is set.
res_name	Fired when the resource of the window is set.
iconify	Fired when a window is iconified.
deiconify	Fired when a window is deiconified.
icon_name	Fired when the icon name changes.
visible_icon_name	Fired when the icon’s visible name changes.
icon_file	Fired when the path to the icon changes.
icon_location	Fired when the icon location changes.
restack	Fired when the window stacking order changes.
echo	Fired when Fvwm receives an Echo command.

For example, to register an interest in new_window and focus_change, the following commands would be set via the socket:

set new_window
set focus_change

To remove interest in an event, use the unset command:

unset focus_change

JSON FORMAT

Each packet sent to a client is in plain JSON. The information contained in each packet varies depending on the event.

TODO: document each JSON structure.

EXAMPLE

The following example shows how to monitor for focus_change events at the shell, printing the JSON returned:

  echo set focus_change | nc -U /tmp/fvwm_mfl.sock 2>&1 | jq --unbuffered

Outputs:

{ "focus_change": { "window": "0x5400022", "type": 0, "hilight": {
"text_colour": 16777215, "bg_colour": 32767 } } }

AUTHORS

This module first appeared in 2020.