Merge branch 'master' into next

[i3/i3] / docs / userguide

i3 User’s Guide
===============
Michael Stapelberg <michael+i3@stapelberg.de>
January 2012

This document contains all the information you need to configure and use the i3
window manager. If it does not, please contact us on IRC (preferred) or post your
question(s) on the mailing list.

== Default keybindings

For the "too long; didn’t read" people, here is an overview of the default
keybindings (click to see the full size image):

*Keys to use with mod (alt):*

image:keyboard-layer1.png["Keys to use with mod (alt)",width=600,link="keyboard-layer1.png"]

*Keys to use with Shift+mod:*

image:keyboard-layer2.png["Keys to use with Shift+mod",width=600,link="keyboard-layer2.png"]

The red keys are the modifiers you need to press (by default), the blue keys
are your homerow.

== Using i3

Throughout this guide, the keyword +mod+ will be used to refer to the
configured modifier. This is the alt key (Mod1) by default, with windows (Mod4)
being a popular alternative.

=== Opening terminals and moving around

One very basic operation is opening a new terminal. By default, the keybinding
for this is mod+Enter, that is Alt+Enter in the default configuration. By
pressing mod+Enter, a new terminal will be opened.  It will fill the whole
space available on your screen.

image:single_terminal.png[Single terminal]

If you now open another terminal, i3 will place it next to the current one,
splitting the screen size in half. Depending on your monitor, i3 will put the
created window beside the existing window (on wide displays) or below the
existing window (rotated displays).

image:two_terminals.png[Two terminals]

To move the focus between the two terminals, you can use the direction keys
which you may know from the editor +vi+. However, in i3, your homerow is used
for these keys (in +vi+, the keys are shifted to the left by one for
compatibility with most keyboard layouts). Therefore, +mod+J+ is left, +mod+K+
is down, +mod+L+ is up and `mod+;` is right. So, to switch between the
terminals, use +mod+K+ or +mod+L+. Of course, you can also use the arrow keys.

At the moment, your workspace is split (it contains two terminals) in a
specific direction (horizontal by default). Every window can be split
horizontally or vertically again, just like the workspace. The terminology is
"window" for a container that actually contains an X11 window (like a terminal
or browser) and "split container" for containers that consist of one or more
windows.

TODO: picture of the tree

To split a window vertically, press +mod+v+. To split it horizontally, press
+mod+h+.

=== Changing the container layout

A split container can have one of the following layouts:

default::
Windows are sized so that every window gets an equal amount of space in the
container.
stacking::
Only the focused window in the container is displayed. You get a list of
windows at the top of the container.
tabbed::
The same principle as +stacking+, but the list of windows at the top is only
a single line which is vertically split.

To switch modes, press +mod+e+ for default, +mod+s+ for stacking and
+mod+w+ for tabbed.

image:modes.png[Container modes]

=== Toggling fullscreen mode for a window

To display a window in fullscreen mode or to go out of fullscreen mode again,
press +mod+f+.

There is also a global fullscreen mode in i3 in which the client will span all
available outputs (the command is +fullscreen global+).

=== Opening other applications

Aside from opening applications from a terminal, you can also use the handy
+dmenu+ which is opened by pressing +mod+d+ by default. Just type the name
(or a part of it) of the application which you want to open. The corresponding
application has to be in your +$PATH+ for this to work.

Additionally, if you have applications you open very frequently, you can
create a keybinding for starting the application directly. See the section
<<configuring>> for details.

=== Closing windows

If an application does not provide a mechanism for closing (most applications
provide a menu, the escape key or a shortcut like +Control+W+ to close), you
can press +mod+Shift+q+ to kill a window. For applications which support
the WM_DELETE protocol, this will correctly close the application (saving
any modifications or doing other cleanup). If the application doesn’t support
the WM_DELETE protocol your X server will kill the window and the behaviour
depends on the application.

=== Using workspaces

Workspaces are an easy way to group a set of windows. By default, you are on
the first workspace, as the bar on the bottom left indicates. To switch to
another workspace, press +mod+num+ where +num+ is the number of the workspace
you want to use. If the workspace does not exist yet, it will be created.

A common paradigm is to put the web browser on one workspace, communication
applications (+mutt+, +irssi+, ...) on another one, and the ones with which you
work, on the third one. Of course, there is no need to follow this approach.

If you have multiple screens, a workspace will be created on each screen at
startup. If you open a new workspace, it will be bound to the screen you
created it on.  When you switch to a workspace on another screen, i3 will set
focus to that screen.

=== Moving windows to workspaces

To move a window to another workspace, simply press +mod+Shift+num+ where
+num+ is (like when switching workspaces) the number of the target workspace.
Similarly to switching workspaces, the target workspace will be created if
it does not yet exist.

=== Resizing

The easiest way to resize a container is by using the mouse: Grab the border
and move it to the wanted size.

See <<resizingconfig>> for how to configure i3 to be able to resize
columns/rows with your keyboard.

=== Restarting i3 inplace

To restart i3 inplace (and thus get into a clean state if there is a bug, or
to upgrade to a newer version of i3) you can use +mod+Shift+r+.

=== Exiting i3

To cleanly exit i3 without killing your X server, you can use +mod+Shift+e+.

=== Floating

Floating mode is the opposite of tiling mode. The position and size of a window
are not managed by i3, but by you. Using this mode violates the tiling
paradigm but can be useful for some corner cases like "Save as" dialog
windows, or toolbar windows (GIMP or similar). Those windows usually set the
appropriate hint and are opened in floating mode by default.

You can toggle floating mode for a window by pressing +mod+Shift+Space+. By
dragging the window’s titlebar with your mouse you can move the window
around. By grabbing the borders and moving them you can resize the window. You
can also do that by using the <<floating_modifier>>.

For resizing floating windows with your keyboard, see <<resizingconfig>>.

Floating windows are always on top of tiling windows.

== Tree

i3 stores all information about the X11 outputs, workspaces and layout of the
windows on them in a tree. The root node is the X11 root window, followed by
the X11 outputs, then dock areas and a content container, then workspaces and
finally the windows themselves. In previous versions of i3 we had multiple lists
(of outputs, workspaces) and a table for each workspace. That approach turned
out to be complicated to use (snapping), understand and implement.

=== The tree consists of Containers

The building blocks of our tree are so called +Containers+. A +Container+ can
host a window (meaning an X11 window, one that you can actually see and use,
like a browser). Alternatively, it could contain one or more +Containers+. A
simple example is the workspace: When you start i3 with a single monitor, a
single workspace and you open two terminal windows, you will end up with a tree
like this:

image::tree-layout2.png["layout2",float="right"]
image::tree-shot4.png["shot4",title="Two terminals on standard workspace"]

=== Orientation and Split Containers

[[OrientationSplit]]

It is only natural to use so-called +Split Containers+ in order to build a
layout when using a tree as data structure. In i3, every +Container+ has an
orientation (horizontal, vertical or unspecified). So, in our example with the
workspace, the default orientation of the workspace +Container+ is horizontal
(most monitors are widescreen nowadays). If you change the orientation to
vertical (+mod+v+ in the default config) and *then* open two terminals, i3 will
configure your windows like this:

image::tree-shot2.png["shot2",title="Vertical Workspace Orientation"]

An interesting new feature of the tree branch is the ability to split anything:
Let’s assume you have two terminals on a workspace (with horizontal
orientation), focus is on the right terminal. Now you want to open another
terminal window below the current one. If you would just open a new terminal
window, it would show up to the right due to the horizontal workspace
orientation. Instead, press +mod+v+ to create a +Vertical Split Container+ (to
open a +Horizontal Split Container+, use +mod+h+). Now you can open a new
terminal and it will open below the current one:

image::tree-layout1.png["Layout",float="right"]
image::tree-shot1.png["shot",title="Vertical Split Container"]

unfloat::[]

You probably guessed it already: There is no limit on how deep your hierarchy
of splits can be.

=== Focus parent

Let’s stay with our example from above. We have a terminal on the left and two
vertically split terminals on the right, focus is on the bottom right one. When
you open a new terminal, it will open below the current one.

So, how can you open a new terminal window to the *right* of the current one?
The solution is to use +focus parent+, which will focus the +Parent Container+ of
the current +Container+. In this case, you would focus the +Vertical Split
Container+ which is *inside* the horizontally oriented workspace. Thus, now new
windows will be opened to the right of the +Vertical Split Container+:

image::tree-shot3.png["shot3",title="Focus parent, then open new terminal"]

[[configuring]]
== Configuring i3

This is where the real fun begins ;-). Most things are very dependant on your
ideal working environment so we can’t make reasonable defaults for them.

While not using a programming language for the configuration, i3 stays
quite flexible in regards to the things you usually want your window manager
to do.

For example, you can configure bindings to jump to specific windows,
you can set specific applications to start on specific workspaces, you can
automatically start applications, you can change the colors of i3, and you
can bind your keys to do useful things.

To change the configuration of i3, copy +/etc/i3/config+ to +\~/.i3/config+
(or +~/.config/i3/config+ if you like the XDG directory scheme) and edit it
with a text editor.

On first start (and on all following starts, unless you have a configuration
file), i3 will offer you to create a configuration file. You can tell the
wizard to use either Alt (Mod1) or Windows (Mod4) as modifier in the config
file. Also, the created config file will use the key symbols of your current
keyboard layout. To start the wizard, use the command +i3-config-wizard+.
Please note that you must not have +~/.i3/config+, otherwise the wizard will
exit.

=== Comments

It is possible and recommended to use comments in your configuration file to
properly document your setup for later reference. Comments are started with
a # and can only be used at the beginning of a line:

*Examples*:
-------------------
# This is a comment
-------------------

=== Fonts

i3 uses X core fonts (not Xft) for rendering window titles. You can use
+xfontsel(1)+ to generate such a font description. To see special characters
(Unicode), you need to use a font which supports the ISO-10646 encoding.

If i3 cannot open the configured font, it will output an error in the logfile
and fall back to a working font.

*Syntax*:
------------------------------
font <X core font description>
------------------------------

*Examples*:
--------------------------------------------------------------
font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
--------------------------------------------------------------

[[keybindings]]

=== Keyboard bindings

A keyboard binding makes i3 execute a command (see below) upon pressing a
specific key. i3 allows you to bind either on keycodes or on keysyms (you can
also mix your bindings, though i3 will not protect you from overlapping ones).

* A keysym (key symbol) is a description for a specific symbol, like "a"
  or "b", but also more strange ones like "underscore" instead of "_". These
  are the ones you use in Xmodmap to remap your keys. To get the current
  mapping of your keys, use +xmodmap -pke+.

* Keycodes do not need to have a symbol assigned (handy for custom vendor
  hotkeys on some notebooks) and they will not change their meaning as you
  switch to a different keyboard layout (when using +xmodmap+).

My recommendation is: If you often switch keyboard layouts but you want to keep
your bindings in the same physical location on the keyboard, use keycodes.
If you don’t switch layouts, and want a clean and simple config file, use
keysyms.

*Syntax*:
----------------------------------
bindsym [Modifiers+]keysym command
bindcode [Modifiers+]keycode command
----------------------------------

*Examples*:
--------------------------------
# Fullscreen
bindsym mod+f fullscreen

# Restart
bindsym mod+Shift+r restart

# Notebook-specific hotkeys
bindcode 214 exec /home/michael/toggle_beamer.sh
--------------------------------

Available Modifiers:

Mod1-Mod5, Shift, Control::
Standard modifiers, see +xmodmap(1)+

Mode_switch::
Unlike other window managers, i3 can use Mode_switch as a modifier. This allows
you to remap capslock (for example) to Mode_switch and use it for both: typing
umlauts or special characters 'and' having some comfortably reachable key
bindings. For example, when typing, capslock+1 or capslock+2 for switching
workspaces is totally convenient. Try it :-).

[[floating_modifier]]

=== The floating modifier

To move floating windows with your mouse, you can either grab their titlebar
or configure the so called floating modifier which you can then press and
click anywhere in the window itself to move it. The most common setup is to
use the same key you use for managing windows (Mod1 for example). Then
you can press Mod1, click into a window using your left mouse button, and drag
it to the position you want.

When holding the floating modifier, you can resize a floating window by
pressing the right mouse button on it and moving around while holding it. If
you hold the shift button as well, the resize will be proportional (the aspect
ratio will be preserved).

*Syntax*:
--------------------------------
floating_modifier <Modifiers>
--------------------------------

*Example*:
--------------------------------
floating_modifier Mod1
--------------------------------

=== Constraining floating window size

The maximum and minimum dimensions of floating windows can be specified. If
either dimension of +floating_maximum_size+ is specified as -1, that dimension
will be unconstrained with respect to its maximum value. If either dimension of
+floating_maximum_size+ is undefined, or specified as 0, i3 will use a default
value to constrain the maximum size. +floating_minimum_size+ is treated in a
manner analogous to +floating_maximum_size+.

*Syntax*:
----------------------------------------
floating_minimum_size <width> x <height>
floating_maximum_size <width> x <height>
----------------------------------------

*Example*:
--------------------------------------
floating_minimum_size 75 x 50
floating_maximum_size -1 x -1
--------------------------------------

=== Orientation for new workspaces

New workspaces get a reasonable default orientation: Wide-screen monitors
(anything wider than high) get horizontal orientation, rotated monitors
(anything higher than wide) get vertical orientation.

With the +default_orientation+ configuration directive, you can override that
behaviour.

*Syntax*:
----------------------------------------------
default_orientation <horizontal|vertical|auto>
----------------------------------------------

*Example*:
----------------------------
default_orientation vertical
----------------------------

=== Layout mode for new containers

This option determines in which mode new containers on workspace level will
start.
///////////////////////////////
See also <<stack-limit>>.
//////////////////////////////

*Syntax*:
---------------------------------------------
workspace_layout <default|stacking|tabbed>
---------------------------------------------
/////////////////////////////////////////////
new_container stack-limit <cols|rows> <value>
/////////////////////////////////////////////

*Example*:
---------------------
workspace_layout tabbed
---------------------

=== Border style for new windows

This option determines which border style new windows will have.

*Syntax*:
---------------------------------------------
new_window <normal|1pixel|none>
---------------------------------------------

*Example*:
---------------------
new_window 1pixel
---------------------

=== Arbitrary commands for specific windows (for_window)

With the +for_window+ command, you can let i3 execute any command when it
encounters a specific window. This can be used to set windows to floating or to
change their border style, for example.

*Syntax*:
-----------------------------
for_window <criteria> command
-----------------------------

*Examples*:
------------------------------------------------
# enable floating mode for all XTerm windows
for_window [class="XTerm"] floating enable

# Make all urxvts use a 1-pixel border:
for_window [class="urxvt"] border 1pixel

# A less useful, but rather funny example:
# makes the window floating as soon as I change
# directory to ~/work
for_window [title="x200: ~/work"] floating enable
------------------------------------------------

The valid criteria are the same as those for commands, see <<command_criteria>>.

=== Variables

As you learned in the section about keyboard bindings, you will have
to configure lots of bindings containing modifier keys. If you want to save
yourself some typing and be able to change the modifier you use later,
variables can be handy.

*Syntax*:
--------------
set $name value
--------------

*Example*:
------------------------
set $m Mod1
bindsym $m+Shift+r restart
------------------------

Variables are directly replaced in the file when parsing. There is no fancy
handling and there are absolutely no plans to change this. If you need a more
dynamic configuration you should create a little script which generates a
configuration file and run it before starting i3 (for example in your
+~/.xsession+ file).

=== Automatically putting clients on specific workspaces

[[assign_workspace]]

To automatically make a specific window show up on a specific workspace, you
can use an *assignment*. You can match windows by using any criteria,
see <<command_criteria>>. It is recommended that you match on window classes
(and instances, when appropriate) instead of window titles whenever possible
because some applications first create their window, and then worry about
setting the correct title. Firefox with Vimperator comes to mind. The window
starts up being named Firefox, and only when Vimperator is loaded does the
title change. As i3 will get the title as soon as the application maps the
window (mapping means actually displaying it on the screen), you’d need to have
to match on 'Firefox' in this case.

*Syntax*:
------------------------------------------------------------
assign <criteria> [→] workspace
------------------------------------------------------------

*Examples*:
----------------------
# Assign URxvt terminals to workspace 2
assign [class="URxvt"] 2

# Same thing, but more precise (exact match instead of substring)
assign [class="^URxvt$"] 2

# Same thing, but with a beautiful arrow :)
assign [class="^URxvt$"] → 2

# Assignment to a named workspace
assign [class="^URxvt$"] → work

# Start urxvt -name irssi
assign [class="^URxvt$" instance="^irssi$"] → 3
----------------------

Note that the arrow is not required, it just looks good :-). If you decide to
use it, it has to be a UTF-8 encoded arrow, not `->` or something like that.

To get the class and instance, you can use +xprop+. After clicking on the
window, you will see the following output:

*xprop*:
-----------------------------------
WM_CLASS(STRING) = "irssi", "URxvt"
-----------------------------------

The first part of the WM_CLASS is the instance ("irssi" in this example), the
second part is the class ("URxvt" in this example).

Should you have any problems with assignments, make sure to check the i3
logfile first (see http://i3wm.org/docs/debugging.html). It includes more
details about the matching process and the window’s actual class, instance and
title when starting up.

=== Automatically starting applications on i3 startup

By using the +exec+ keyword outside a keybinding, you can configure
which commands will be performed by i3 on initial startup. +exec+
commands will not run when restarting i3, if you need a command to run
also when restarting i3 you should use the +exec_always+
keyword. These commands will be run in order.

*Syntax*:
-------------------
exec [--no-startup-id] command
exec_always [--no-startup-id] command
-------------------

*Examples*:
--------------------------------
exec chromium
exec_always ~/my_script.sh

# Execute the terminal emulator urxvt, which is not yet startup-notification aware.
exec --no-startup-id urxvt
--------------------------------

The flag --no-startup-id is explained in <<exec>>.

[[workspace_screen]]

=== Automatically putting workspaces on specific screens

If you assign clients to workspaces, it might be handy to put the
workspaces on specific screens. Also, the assignment of workspaces to screens
will determine which workspace i3 uses for a new screen when adding screens
or when starting (e.g., by default it will use 1 for the first screen, 2 for
the second screen and so on).

*Syntax*:
----------------------------------
workspace <workspace> output <output>
----------------------------------

The 'output' is the name of the RandR output you attach your screen to. On a
laptop, you might have VGA1 and LVDS1 as output names. You can see the
available outputs by running +xrandr --current+.

If you use named workspaces, they must be quoted:

*Examples*:
---------------------------
workspace 1 output LVDS1
workspace 5 output VGA1
workspace "2: vim" output VGA1
---------------------------

=== Changing colors

You can change all colors which i3 uses to draw the window decorations.

*Syntax*:
--------------------------------------------
colorclass border background text indicator
--------------------------------------------

Where colorclass can be one of:

client.focused::
        A client which currently has the focus.
client.focused_inactive::
        A client which is the focused one of its container, but it does not have
        the focus at the moment.
client.unfocused::
        A client which is not the focused one of its container.
client.urgent::
        A client which has its urgency hint activated.

You can also specify the color to be used to paint the background of the client
windows. This color will be used to paint the window on top of which the client
will be rendered.

*Syntax*:
-----------------------
client.background color
-----------------------

Only clients that do not cover the whole area of this window expose the color
used to paint it. If you use a color other than black for your terminals, you
most likely want to set the client background color to the same color as your
terminal program's background color to avoid black gaps between the rendered
area of the terminal and the i3 border.

Colors are in HTML hex format (#rrggbb), see the following example:

*Examples (default colors)*:
---------------------------------------------------------
# class                 border  backgr. text    indicator
client.focused          #4c7899 #285577 #ffffff #2e9ef4
client.focused_inactive #333333 #5f676a #ffffff #484e50
client.unfocused        #333333 #222222 #888888 #292d2e
client.urgent           #2f343a #900000 #ffffff #900000
---------------------------------------------------------

Note that for the window decorations, the color around the child window is the
background color, and the border color is only the two thin lines at the top of
the window.

The indicator color is used for indicating where a new window will be opened.
For horizontal split containers, the right border will be painted in indicator
color, for vertical split containers, the bottom border. This only applies to
single windows within a split container, which are otherwise indistinguishable
from single windows outside of a split container.

=== Interprocess communication

i3 uses unix sockets to provide an IPC interface. This allows third-party
programs to get information from i3, such as the current workspaces
(to display a workspace bar), and to control i3.

The IPC socket is enabled by default and will be created in
+/tmp/i3-%u.XXXXXX/ipc-socket.%p+ where +%u+ is your UNIX username, +%p+ is
the PID of i3 and XXXXXX is a string of random characters from the portable
filename character set (see mkdtemp(3)).

You can override the default path through the environment-variable +I3SOCK+ or
by specifying the +ipc-socket+ directive. This is discouraged, though, since i3
does the right thing by default. If you decide to change it, it is strongly
recommended to set this to a location in your home directory so that no other
user can create that directory.

*Examples*:
----------------------------
ipc-socket ~/.i3/i3-ipc.sock
----------------------------

You can then use the +i3-msg+ application to perform any command listed in
the next section.

=== Focus follows mouse

If you have a setup where your mouse usually is in your way (like a touchpad
on your laptop which you do not want to disable completely), you might want
to disable 'focus follows mouse' and control focus only by using your keyboard.
The mouse will still be useful inside the currently active window (for example
to click on links in your browser window).

*Syntax*:
----------------------------
focus_follows_mouse <yes|no>
----------------------------

*Example*:
----------------------
focus_follows_mouse no
----------------------

=== Popups during fullscreen mode

When you are in fullscreen mode, some applications still open popup windows
(take Xpdf for example). This is because these applications may not be aware
that they are in fullscreen mode (they do not check the corresponding hint).
There are two things which are possible to do in this situation:

1. Just ignore the popup (don’t map it). This won’t interrupt you while you are
   in fullscreen. However, some apps might react badly to this (deadlock until
   you go out of fullscreen).
2. Leave fullscreen mode. This is the default.

*Syntax*:
-------------------------------------------------
popup_during_fullscreen <ignore|leave_fullscreen>
-------------------------------------------------

*Example*:
------------------------------
popup_during_fullscreen ignore
------------------------------

=== Focus wrapping

When being in a tabbed or stacked container, the first container will be
focused when you use +focus down+ on the last container -- the focus wraps. If
however there is another stacked/tabbed container in that direction, focus will
be set on that container. This is the default behaviour so you can navigate to
all your windows without having to use +focus parent+.

If you want the focus to *always* wrap and you are aware of using +focus
parent+ to switch to different containers, you can use the
+force_focus_wrapping+ configuration directive. After enabling it, the focus
will always wrap.

*Syntax*:
-----------------------------
force_focus_wrapping <yes|no>
-----------------------------

*Example*:
------------------------
force_focus_wrapping yes
------------------------

=== Forcing Xinerama

As explained in-depth in <http://i3wm.org/docs/multi-monitor.html>, some X11
video drivers (especially the nVidia binary driver) only provide support for
Xinerama instead of RandR. In such a situation, i3 must be told to use the
inferior Xinerama API explicitly and therefore don’t provide support for
reconfiguring your screens on the fly (they are read only once on startup and
that’s it).

For people who do cannot modify their +~/.xsession+ to add the
+--force-xinerama+ commandline parameter, a configuration option is provided:

*Syntax*:
-----------------------
force_xinerama <yes|no>
-----------------------

*Example*:
------------------
force_xinerama yes
------------------

Also note that your output names are not descriptive (like +HDMI1+) when using
Xinerama, instead they are counted up, starting at 0: +xinerama-0+, +xinerama-1+, …

=== Automatic back-and-forth when switching to the current workspace

This configuration directive enables automatic +workspace back_and_forth+ (see
<<back_and_forth>>) when switching to the workspace that is currently focused.

For instance: Assume you are on workspace "1: www" and switch to "2: IM" using
mod+2 because somebody sent you a message. You don’t need to remember where you
came from now, you can just press mod+2 again to switch back to "1: www".

*Syntax*:
--------------------------------------
workspace_auto_back_and_forth <yes|no>
--------------------------------------

*Example*:
---------------------------------
workspace_auto_back_and_forth yes
---------------------------------

== Configuring i3bar

The bar at the bottom of your monitor is drawn by a separate process called
i3bar. Having this part of "the i3 user interface" in a separate process has
several advantages:

1. It is a modular approach. If you don’t need a workspace bar at all, or if
   you prefer a different one (dzen2, xmobar, maybe even gnome-panel?), you can
   just remove the i3bar configuration and start your favorite bar instead.
2. It follows the UNIX philosophy of "Make each program do one thing well".
   While i3 manages your windows well, i3bar is good at displaying a bar on
   each monitor (unless you configure it otherwise).
3. It leads to two separate, clean codebases. If you want to understand i3, you
   don’t need to bother with the details of i3bar and vice versa.

That said, i3bar is configured in the same configuration file as i3. This is
because it is tightly coupled with i3 (in contrary to i3lock or i3status which
are useful for people using other window managers). Therefore, it makes no
sense to use a different configuration place when we already have a good
configuration infrastructure in place.

Configuring your workspace bar starts with opening a +bar+ block. You can have
multiple bar blocks to use different settings for different outputs (monitors):

*Example*:
---------------------------
bar {
    status_command i3status
}
---------------------------

=== i3bar command

By default i3 will just pass +i3bar+ and let your shell handle the execution,
searching your +$PATH+ for a correct version.
If you have a different +i3bar+ somewhere or the binary is not in your +$PATH+ you can
tell i3 what to execute.

The specified command will be passed to +sh -c+, so you can use globbing and
have to have correct quoting etc.

*Syntax*:
----------------------
i3bar_command command
----------------------

*Example*:
-------------------------------------------------
bar {
    i3bar_command /home/user/bin/i3bar
}
-------------------------------------------------

[[status_command]]
=== Statusline command

i3bar can run a program and display every line of its +stdout+ output on the
right hand side of the bar. This is useful to display system information like
your current IP address, battery status or date/time.

The specified command will be passed to +sh -c+, so you can use globbing and
have to have correct quoting etc.

*Syntax*:
----------------------
status_command command
----------------------

*Example*:
-------------------------------------------------
bar {
    status_command i3status --config ~/.i3status.conf
}
-------------------------------------------------

=== Display mode

You can have i3bar either be visible permanently at one edge of the screen
(+dock+ mode) or make it show up when you press your modifier key (+hide+
mode). The modifier key can be configured using the +modifier+ option.

The hide mode maximizes screen space that can be used for actual windows. Also,
i3bar sends the +SIGSTOP+ and +SIGCONT+ signals to the statusline process to
save battery power.

The default is dock mode; in hide mode, the default modifier is Mod4 (usually
the windows key).

*Syntax*:
----------------
mode <dock|hide>
modifier <Modifier>
----------------

*Example*:
----------------
bar {
    mode hide
    modifier Mod1
}
----------------

Available modifiers are Mod1-Mod5, Shift, Control (see +xmodmap(1)+).

[[i3bar_position]]
=== Position

This option determines in which edge of the screen i3bar should show up.

The default is bottom.

*Syntax*:
---------------------
position <top|bottom>
---------------------

*Example*:
---------------------
bar {
    position top
}
---------------------

=== Output(s)

You can restrict i3bar to one or more outputs (monitors). The default is to
handle all outputs. Restricting the outputs is useful for using different
options for different outputs by using multiple 'bar' blocks.

To make a particular i3bar instance handle multiple outputs, specify the output
directive multiple times.

*Syntax*:
---------------
output <output>
---------------

*Example*:
-------------------------------
# big monitor: everything
bar {
    # The display is connected either via HDMI or via DisplayPort
    output HDMI2
    output DP2
    status_command i3status
}

# laptop monitor: bright colors and i3status with less modules.
bar {
    output LVDS1
    status_command i3status --config ~/.i3status-small.conf
    colors {
        background #000000
        statusline #ffffff
    }
}
-------------------------------

=== Tray output

i3bar by default provides a system tray area where programs such as
NetworkManager, VLC, Pidgin, etc. can place little icons.

You can configure on which output (monitor) the icons should be displayed or
you can turn off the functionality entirely.

*Syntax*:
-------------------------
tray_output <none|output>
-------------------------

*Example*:
-------------------------
# disable system tray
bar {
    tray_output none
}

# show tray icons on the big monitor
bar {
    tray_output HDMI2
}
-------------------------

=== Font

Specifies the font (again, X core font, not Xft, just like in i3) to be used in
the bar.

*Syntax*:
---------------------
font <font>
---------------------

*Example*:
--------------------------------------------------------------
bar {
    font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
}
--------------------------------------------------------------

=== Workspace buttons

Specifies whether workspace buttons should be shown or not. This is useful if
you want to display a statusline-only bar containing additional information.

The default is to show workspace buttons.

*Syntax*:
--------------------------
workspace_buttons <yes|no>
--------------------------

*Example*:
--------------------
bar {
    workspace_buttons no
}
--------------------

=== Colors

As with i3, colors are in HTML hex format (#rrggbb). The following colors can
be configured at the moment:

background::
        Background color of the bar.
statusline::
        Text color to be used for the statusline.
focused_workspace::
        Border, background and text color for a workspace button when the workspace
        has focus.
active_workspace::
        Border, background and text color for a workspace button when the workspace
        is active (visible) on some output, but the focus is on another one.
        You can only tell this apart from the focused workspace when you are
        using multiple monitors.
inactive_workspace::
        Border, background and text color for a workspace button when the workspace
        does not have focus and is not active (visible) on any output. This
        will be the case for most workspaces.
urgent_workspace::
        Border, background and text color for a workspace button when the workspace
        window with the urgency hint set.

*Syntax*:
----------------------------------------
colors {
    background <color>
    statusline <color>

    colorclass <border> <background> <text>
}
----------------------------------------

*Example (default colors)*:
--------------------------------------
bar {
    colors {
        background #000000
        statusline #ffffff

        focused_workspace  #4c7899 #285577 #ffffff
        active_workspace   #333333 #5f676a #ffffff
        inactive_workspace #333333 #222222 #888888
        urgent_workspace   #2f343a #900000 #ffffff
    }
}
--------------------------------------

== List of commands

Commands are what you bind to specific keypresses. You can also issue commands
at runtime without pressing a key by using the IPC interface. An easy way to
do this is to use the +i3-msg+ utility:

*Example*:
--------------------------
# execute this on your shell to make the current container borderless
i3-msg border none
--------------------------

Commands can be chained by using +;+ (a semicolon). So, to move a window to a
specific workspace and immediately switch to that workspace, you can configure
the following keybinding:

*Example*:
--------------------------------------------------------
bindsym mod+x move container to workspace 3; workspace 3
--------------------------------------------------------

[[command_criteria]]

Furthermore, you can change the scope of a command, that is, which containers
should be affected by that command, by using various criteria. These are
prefixed in square brackets to every command. If you want to kill all windows
which have the class Firefox, use:

*Example*:
------------------------------------
bindsym mod+x [class="Firefox"] kill

# same thing, but case-insensitive
bindsym mod+x [class="(?i)firefox"] kill
------------------------------------

The criteria which are currently implemented are:

class::
        Compares the window class (the second part of WM_CLASS)
instance::
        Compares the window instance (the first part of WM_CLASS)
window_role::
        Compares the window role (WM_WINDOW_ROLE).
id::
        Compares the X11 window ID, which you can get via +xwininfo+ for example.
title::
        Compares the X11 window title (_NET_WM_NAME or WM_NAME as fallback).
urgent::
        Compares the urgent state of the window. Can be "latest" or "oldest".
        Matches the latest or oldest urgent window, respectively.
        (The following aliases are also available: newest, last, recent, first)
con_mark::
        Compares the mark set for this container, see <<vim_like_marks>>.
con_id::
        Compares the i3-internal container ID, which you can get via the IPC
        interface. Handy for scripting.

The criteria +class+, +instance+, +role+, +title+ and +mark+ are actually
regular expressions (PCRE). See +pcresyntax(3)+ or +perldoc perlre+ for
information on how to use them.

[[exec]]

=== Executing applications (exec)

What good is a window manager if you can’t actually start any applications?
The exec command starts an application by passing the command you specify to a
shell. This implies that you can use globbing (wildcards) and programs will be
searched in your $PATH.

*Syntax*:
------------------------------
exec [--no-startup-id] command
------------------------------

*Example*:
------------------------------
# Start the GIMP
bindsym mod+g exec gimp

# Start the terminal emulator urxvt which is not yet startup-notification-aware
bindsym mod+Return exec --no-startup-id urxvt
------------------------------

The +--no-startup-id+ parameter disables startup-notification support for this
particular exec command. With startup-notification, i3 can make sure that a
window appears on the workspace on which you used the exec command. Also, it
will change the X11 cursor to +watch+ (a clock) while the application is
launching. So, if an application is not startup-notification aware (most GTK
and Qt using applications seem to be, though), you will end up with a watch
cursor for 60 seconds.

=== Splitting containers

The split command makes the current window a split container. Split containers
can contain multiple windows. Every split container has an orientation, it is
either split horizontally (a new window gets placed to the right of the current
one) or vertically (a new window gets placed below the current one).

If you apply this command to a split container with the same orientation,
nothing will happen. If you use a different orientation, the split container’s
orientation will be changed (if it does not have more than one window).

*Syntax*:
---------------------------
split <vertical|horizontal>
---------------------------

*Example*:
------------------------------
bindsym mod+v split vertical
bindsym mod+h split horizontal
------------------------------

=== Manipulating layout

Use +layout default+, +layout stacking+ or +layout tabbed+ to change the
current container layout to default, stacking or tabbed layout, respectively.

To make the current window (!) fullscreen, use +fullscreen+, to make
it floating (or tiling again) use +floating enable+ respectively +floating disable+
(or +floating toggle+):

*Examples*:
--------------
bindsym mod+s layout stacking
bindsym mod+l layout default
bindsym mod+w layout tabbed

# Toggle fullscreen
bindsym mod+f fullscreen

# Toggle floating/tiling
bindsym mod+t floating toggle
--------------

=== Focusing/Moving containers

To change the focus, use the focus command: +focus left+, +focus right+, +focus
down+ and +focus up+.

There are a few special parameters you can use for the focus command:

parent::
        Sets focus to the +Parent Container+ of the current +Container+.
child::
        The opposite of +focus parent+, sets the focus to the last focused
        child container.
floating::
        Sets focus to the last focused floating container.
tiling::
        Sets focus to the last focused tiling container.
mode_toggle::
        Toggles between floating/tiling containers.
output::
        Followed by a direction or an output name, this will focus the
        corresponding output.

For moving, use +move left+, +move right+, +move down+ and +move up+.

*Syntax*:
-----------------------------------
focus <left|right|down|up>
focus <parent|child|floating|tiling|mode_toggle>
focus output <<left|right|down|up>|output>
move <left|right|down|up> [<px> px]
-----------------------------------

Note that the amount of pixels you can specify for the +move+ command is only
relevant for floating containers. The default amount is 10 pixels.

*Examples*:
----------------------
# Focus container on the left, bottom, top, right:
bindsym mod+j focus left
bindsym mod+k focus down
bindsym mod+l focus up
bindsym mod+semicolon focus right

# Focus parent container
bindsym mod+u focus parent

# Focus last floating/tiling container
bindsym mod+g focus mode_toggle

# Focus the output right to the current one
bindsym mod+x focus output right

# Focus the big output
bindsym mod+x focus output HDMI-2

# Move container to the left, bottom, top, right:
bindsym mod+j move left
bindsym mod+k move down
bindsym mod+l move up
bindsym mod+semicolon move right

# Move container, but make floating containers
# move more than the default
bindsym mod+j move left 20 px
----------------------

=== Changing (named) workspaces/moving to workspaces

To change to a specific workspace, use the +workspace+ command, followed by the
number or name of the workspace. To move containers to specific workspaces, use
+move container to workspace+.

You can also switch to the next and previous workspace with the commands
+workspace next+ and +workspace prev+, which is handy, for example, if you have
workspace 1, 3, 4 and 9 and you want to cycle through them with a single key
combination. To restrict those to the current output, use +workspace
next_on_output+ and +workspace prev_on_output+. Similarly, you can use +move
container to workspace next+ and +move container to workspace prev+ to move a
container to the next/previous workspace.

[[back_and_forth]]
To switch back to the previously focused workspace, use +workspace
back_and_forth+.

To move a container to another xrandr output such as +LVDS1+ or +VGA1+, you can
use the +move container to output+ command followed by the name of the target
output. You may also use +left+, +right+, +up+, +down+ instead of the xrandr
output name to move to the next output in the specified direction.

To move a whole workspace to another xrandr output such as +LVDS1+ or +VGA1+,
you can use the +move workspace to output+ command followed by the name of the
target output. You may also use +left+, +right+, +up+, +down+ instead of the
xrandr output name to move to the next output in the specified direction.

*Examples*:
-------------------------
bindsym mod+1 workspace 1
bindsym mod+2 workspace 2
...

bindsym mod+Shift+1 move container to workspace 1
bindsym mod+Shift+2 move container to workspace 2
...

# switch between the current and the previously focused one
bindsym mod+b workspace back_and_forth

# move the whole workspace to the next output
bindsym mod+x move workspace to output right
-------------------------

==== Named workspaces

Workspaces are identified by their name. So, instead of using numbers in the
workspace command, you can use an arbitrary name:

*Example*:
-------------------------
bindsym mod+1 workspace mail
...
-------------------------

If you want the workspace to have a number *and* a name, just prefix the
number, like this:

*Example*:
-------------------------
bindsym mod+1 workspace 1: mail
bindsym mod+2 workspace 2: www
...
-------------------------

Note that the workspace will really be named "1: mail". i3 treats workspace
names beginning with a number in a slightly special way. Normally, named
workspaces are ordered the way they appeared. When they start with a number, i3
will order them numerically.

[[resizingconfig]]

=== Resizing containers/windows

If you want to resize containers/windows using your keyboard, you can use the
+resize+ command:

*Syntax*:
---------------------------------------------------------
resize <grow|shrink> <direction> [<px> px] [or <ppt> ppt]
---------------------------------------------------------

Direction can be one of +up+, +down+, +left+ or +right+. The optional pixel
argument specifies by how many pixels a *floating container* should be grown or
shrunk (the default is 10 pixels). The ppt argument means percentage points
and specifies by how many percentage points a *tiling container* should be
grown or shrunk (the default is 10 percentage points).

I recommend using the resize command inside a so called +mode+:

.Example: Configuration file, defining a mode for resizing
----------------------------------------------------------------------
mode "resize" {
        # These bindings trigger as soon as you enter the resize mode

        # They resize the border in the direction you pressed, e.g.
        # when pressing left, the window is resized so that it has
        # more space on its left

        bindsym j resize shrink left
        bindsym Shift+j resize grow left

        bindsym k resize grow down
        bindsym Shift+k resize shrink down

        bindsym l resize shrink up
        bindsym Shift+l resize grow up

        bindsym semicolon resize grow right
        bindsym Shift+semicolon resize shrink right

        # back to normal: Enter or Escape
        bindsym Return mode "default"
        bindsym Escape mode "default"
}

# Enter resize mode
bindsym mod+r mode "resize"
----------------------------------------------------------------------

=== Jumping to specific windows

Often when in a multi-monitor environment, you want to quickly jump to a
specific window. For example, while working on workspace 3 you may want to
jump to your mail client to email your boss that you’ve achieved some
important goal. Instead of figuring out how to navigate to your mailclient,
it would be more convenient to have a shortcut. You can use the +focus+ command
with criteria for that.

*Syntax*:
----------------------------------------------------
[class="class"] focus
[title="title"] focus
----------------------------------------------------

*Examples*:
------------------------------------------------
# Get me to the next open VIM instance
bindsym mod+a [class="urxvt" title="VIM"] focus
------------------------------------------------

=== VIM-like marks (mark/goto)

[[vim_like_marks]]

This feature is like the jump feature: It allows you to directly jump to a
specific window (this means switching to the appropriate workspace and setting
focus to the windows). However, you can directly mark a specific window with
an arbitrary label and use it afterwards.  You do not need to ensure that your
windows have unique classes or titles, and you do not need to change your
configuration file.

As the command needs to include the label with which you want to mark the
window, you cannot simply bind it to a key.  +i3-input+ is a tool created
for this purpose: It lets you input a command and sends the command to i3. It
can also prefix this command and display a custom prompt for the input dialog.

*Syntax*:
------------------------------
mark identifier
[con_mark="identifier"] focus
------------------------------

*Example (in a terminal)*:
------------------------------
$ i3-msg mark irssi
$ i3-msg '[con_mark="irssi"] focus'
------------------------------

///////////////////////////////////////////////////////////////////
TODO: make i3-input replace %s
*Examples*:
---------------------------------------
# Read 1 character and mark the current window with this character
bindsym mod+m exec i3-input -p 'mark ' -l 1 -P 'Mark: '

# Read 1 character and go to the window with the character
bindsym mod+g exec i3-input -p 'goto ' -l 1 -P 'Goto: '
---------------------------------------

Alternatively, if you do not want to mess with +i3-input+, you could create
seperate bindings for a specific set of labels and then only use those labels.
///////////////////////////////////////////////////////////////////

=== Changing border style

To change the border of the current client, you can use +border normal+ to use the normal
border (including window title), +border 1pixel+ to use a 1-pixel border (no window title)
and +border none+ to make the client borderless.

There is also +border toggle+ which will toggle the different border styles.

*Examples*:
----------------------------
bindsym mod+t border normal
bindsym mod+y border 1pixel
bindsym mod+u border none
----------------------------

[[stack-limit]]

///////////////////////////////////////////////////////////////////////////////
TODO: not yet implemented
=== Changing the stack-limit of a container

If you have a single container with a lot of windows inside it (say, more than
10), the default layout of a stacking container can get a little unhandy.
Depending on your screen’s size, you might end up with only half of the title
lines being actually used, wasting a lot of screen space.

Using the +stack-limit+ command, you can limit the number of rows or columns
in a stacking container. i3 will create columns or rows (depending on what
you limited) automatically as needed.

*Syntax*:
--------------------------------
stack-limit <cols|rows> <value>
--------------------------------

*Examples*:
-------------------
# I always want to have two window titles in one line
stack-limit cols 2

# Not more than 5 rows in this stacking container
stack-limit rows 5
-------------------

image:stacklimit.png[Container limited to two columns]
///////////////////////////////////////////////////////////////////////////////

=== Reloading/Restarting/Exiting

You can make i3 reload its configuration file with +reload+. You can also
restart i3 inplace with the +restart+ command to get it out of some weird state
(if that should ever happen) or to perform an upgrade without having to restart
your X session. To exit i3 properly, you can use the +exit+ command,
however you don’t need to (simply killing your X session is fine as well).

*Examples*:
----------------------------
bindsym mod+Shift+r restart
bindsym mod+Shift+w reload
bindsym mod+Shift+e exit
----------------------------

=== Scratchpad

There are two commands to use any existing window as scratchpad window. +move
scratchpad+ will move a window to the scratchpad workspace. This will make it
invisible until you show it again. There is no way to open that workspace.
Instead, when using +scratchpad show+, the window will be shown again, as a
floating window, centered on your current workspace (using +scratchpad show+ on
a visible scratchpad window will make it hidden again, so you can have a
keybinding to toggle).

As the name indicates, this is useful for having a window with your favorite
editor always at hand. However, you can also use this for other permanently
running applications which you don’t want to see all the time: Your music
player, alsamixer, maybe even your mail client…?

*Syntax*:
---------------
move scratchpad

scratchpad show
---------------

*Examples*:
------------------------------------------------
# Make the currently focused window a scratchpad
bindsym mod+Shift+minus move scratchpad

# Show the first scratchpad window
bindsym mod+minus scratchpad show

# Show the sup-mail scratchpad window, if any.
bindsym mod4+s [title="^Sup ::"] scratchpad show
------------------------------------------------

[[multi_monitor]]

== Multiple monitors

As you can see in the goal list on the website, i3 was specifically developed
with support for multiple monitors in mind. This section will explain how to
handle multiple monitors.

When you have only one monitor, things are simple. You usually start with
workspace 1 on your monitor and open new ones as you need them.

When you have more than one monitor, each monitor will get an initial
workspace.  The first monitor gets 1, the second gets 2 and a possible third
would get 3. When you switch to a workspace on a different monitor, i3 will
switch to that monitor and then switch to the workspace. This way, you don’t
need shortcuts to switch to a specific monitor, and you don’t need to remember
where you put which workspace. New workspaces will be opened on the currently
active monitor.  It is not possible to have a monitor without a workspace.

The idea of making workspaces global is based on the observation that most
users have a very limited set of workspaces on their additional monitors.
They are often used for a specific task (browser, shell) or for monitoring
several things (mail, IRC, syslog, …). Thus, using one workspace on one monitor
and "the rest" on the other monitors often makes sense. However, as you can
create an unlimited number of workspaces in i3 and tie them to specific
screens, you can have the "traditional" approach of having X workspaces per
screen by changing your configuration (using modes, for example).

=== Configuring your monitors

To help you get going if you have never used multiple monitors before, here is
a short overview of the xrandr options which will probably be of interest to
you. It is always useful to get an overview of the current screen configuration.
Just run "xrandr" and you will get an output like the following:
-------------------------------------------------------------------------------
$ xrandr
Screen 0: minimum 320 x 200, current 1280 x 800, maximum 8192 x 8192
VGA1 disconnected (normal left inverted right x axis y axis)
LVDS1 connected 1280x800+0+0 (normal left inverted right x axis y axis) 261mm x 163mm
   1280x800       60.0*+   50.0
   1024x768       85.0     75.0     70.1     60.0
   832x624        74.6
   800x600        85.1     72.2     75.0     60.3     56.2
   640x480        85.0     72.8     75.0     59.9
   720x400        85.0
   640x400        85.1
   640x350        85.1
--------------------------------------------------------------------------------------

Several things are important here: You can see that +LVDS1+ is connected (of
course, it is the internal flat panel) but +VGA1+ is not. If you have a monitor
connected to one of the ports but xrandr still says "disconnected", you should
check your cable, monitor or graphics driver.

The maximum resolution you can see at the end of the first line is the maximum
combined resolution of your monitors. By default, it is usually too low and has
to be increased by editing +/etc/X11/xorg.conf+.

So, say you connected VGA1 and want to use it as an additional screen:
-------------------------------------------
xrandr --output VGA1 --auto --left-of LVDS1
-------------------------------------------
This command makes xrandr try to find the native resolution of the device
connected to +VGA1+ and configures it to the left of your internal flat panel.
When running "xrandr" again, the output looks like this:
-------------------------------------------------------------------------------
$ xrandr
Screen 0: minimum 320 x 200, current 2560 x 1024, maximum 8192 x 8192
VGA1 connected 1280x1024+0+0 (normal left inverted right x axis y axis) 338mm x 270mm
   1280x1024      60.0*+   75.0
   1280x960       60.0
   1152x864       75.0
   1024x768       75.1     70.1     60.0
   832x624        74.6
   800x600        72.2     75.0     60.3     56.2
   640x480        72.8     75.0     66.7     60.0
   720x400        70.1
LVDS1 connected 1280x800+1280+0 (normal left inverted right x axis y axis) 261mm x 163mm
   1280x800       60.0*+   50.0
   1024x768       85.0     75.0     70.1     60.0
   832x624        74.6
   800x600        85.1     72.2     75.0     60.3     56.2
   640x480        85.0     72.8     75.0     59.9
   720x400        85.0
   640x400        85.1
   640x350        85.1
-------------------------------------------------------------------------------
Please note that i3 uses exactly the same API as xrandr does, so it will see
only what you can see in xrandr.

See also <<presentations>> for more examples of multi-monitor setups.

=== Interesting configuration for multi-monitor environments

There are several things to configure in i3 which may be interesting if you
have more than one monitor:

1. You can specify which workspace should be put on which screen. This
   allows you to have a different set of workspaces when starting than just
   1 for the first monitor, 2 for the second and so on. See
   <<workspace_screen>>.
2. If you want some applications to generally open on the bigger screen
   (MPlayer, Firefox, …), you can assign them to a specific workspace, see
   <<assign_workspace>>.
3. If you have many workspaces on many monitors, it might get hard to keep
   track of which window you put where. Thus, you can use vim-like marks to
   quickly switch between windows. See <<vim_like_marks>>.

== i3 and the rest of your software world

=== Displaying a status line

A very common thing amongst users of exotic window managers is a status line at
some corner of the screen. It is an often superior replacement to the widget
approach you have in the task bar of a traditional desktop environment.

If you don’t already have your favorite way of generating such a status line
(self-written scripts, conky, …), then i3status is the recommended tool for
this task. It was written in C with the goal of using as few syscalls as
possible to reduce the time your CPU is woken up from sleep states. Because
i3status only spits out text, you need to combine it with some other tool, like
i3bar. See <<status_command>> for how to display i3status in i3bar.

Regardless of which application you use to display the status line, you
want to make sure that it registers as a dock window using EWMH hints. i3 will
position the window either at the top or at the bottom of the screen, depending
on which hint the application sets. With i3bar, you can configure its position,
see <<i3bar_position>>.

=== Giving presentations (multi-monitor)

When giving a presentation, you typically want the audience to see what you see
on your screen and then go through a series of slides (if the presentation is
simple). For more complex presentations, you might want to have some notes
which only you can see on your screen, while the audience can only see the
slides.

[[presentations]]
==== Case 1: everybody gets the same output
This is the simple case. You connect your computer to the video projector,
turn on both (computer and video projector) and configure your X server to
clone the internal flat panel of your computer to the video output:
-----------------------------------------------------
xrandr --output VGA1 --mode 1024x768 --same-as LVDS1
-----------------------------------------------------
i3 will then use the lowest common subset of screen resolutions, the rest of
your screen will be left untouched (it will show the X background). So, in
our example, this would be 1024x768 (my notebook has 1280x800).

==== Case 2: you can see more than your audience
This case is a bit harder. First of all, you should configure the VGA output
somewhere near your internal flat panel, say right of it:
-----------------------------------------------------
xrandr --output VGA1 --mode 1024x768 --right-of LVDS1
-----------------------------------------------------
Now, i3 will put a new workspace (depending on your settings) on the new screen
and you are in multi-monitor mode (see <<multi_monitor>>).

Because i3 is not a compositing window manager, there is no ability to
display a window on two screens at the same time. Instead, your presentation
software needs to do this job (that is, open a window on each screen).