993 lines
41 KiB
Plaintext
993 lines
41 KiB
Plaintext
Hacking i3: How To
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==================
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Michael Stapelberg <michael+i3@stapelberg.de>
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July 2011
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This document is intended to be the first thing you read before looking and/or
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touching i3’s source code. It should contain all important information to help
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you understand why things are like they are. If it does not mention something
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you find necessary, please do not hesitate to contact me.
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== Window Managers
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A window manager is not necessarily needed to run X, but it is usually used in
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combination with X to facilitate some things. The window manager's job is to
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take care of the placement of windows, to provide the user with some mechanisms
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to change the position/size of windows and to communicate with clients to a
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certain extent (for example handle fullscreen requests of clients such as
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MPlayer).
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There are no different contexts in which X11 clients run, so a window manager
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is just another client, like all other X11 applications. However, it handles
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some events which normal clients usually don’t handle.
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In the case of i3, the tasks (and order of them) are the following:
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. Grab the key bindings (events will be sent upon keypress/keyrelease)
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. Iterate through all existing windows (if the window manager is not started as
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the first client of X) and manage them (reparent them, create window
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decorations, etc.)
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. When new windows are created, manage them
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. Handle the client’s `_WM_STATE` property, but only the `_WM_STATE_FULLSCREEN`
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. Handle the client’s `WM_NAME` property
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. Handle the client’s size hints to display them proportionally
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. Handle the client’s urgency hint
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. Handle enter notifications (focus follows mouse)
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. Handle button (as in mouse buttons) presses for focus/raise on click
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. Handle expose events to re-draw own windows such as decorations
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. React to the user’s commands: Change focus, Move windows, Switch workspaces,
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Change the layout mode of a container (default/stacking/tabbed), start a new
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application, restart the window manager
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In the following chapters, each of these tasks and their implementation details
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will be discussed.
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=== Tiling window managers
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Traditionally, there are two approaches to managing windows: The most common
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one nowadays is floating, which means the user can freely move/resize the
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windows. The other approach is called tiling, which means that your window
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manager distributes windows to use as much space as possible while not
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overlapping each other.
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The idea behind tiling is that you should not need to waste your time
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moving/resizing windows while you usually want to get some work done. After
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all, most users sooner or later tend to lay out their windows in a way which
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corresponds to tiling or stacking mode in i3. Therefore, why not let i3 do this
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for you? Certainly, it’s faster than you could ever do it.
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The problem with most tiling window managers is that they are too unflexible.
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In my opinion, a window manager is just another tool, and similar to vim which
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can edit all kinds of text files (like source code, HTML, …) and is not limited
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to a specific file type, a window manager should not limit itself to a certain
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layout (like dwm, awesome, …) but provide mechanisms for you to easily create
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the layout you need at the moment.
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=== The layout table
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*********************************************************************************
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This section has not been updated for v4.0 yet, sorry! We wanted to release on
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time, but we will update this soon. Please talk to us on IRC if you need to
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know stuff *NOW* :).
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*********************************************************************************
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/////////////////////////////////////////////////////////////////////////////////
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To accomplish flexible layouts, we decided to simply use a table. The table
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grows and shrinks as you need it. Each cell holds a container which then holds
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windows (see picture below). You can use different layouts for each container
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(default layout and stacking layout).
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So, when you open a terminal and immediately open another one, they reside in
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the same container, in default layout. The layout table has exactly one column,
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one row and therefore one cell. When you move one of the terminals to the
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right, the table needs to grow. It will be expanded to two columns and one row.
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This enables you to have different layouts for each container. The table then
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looks like this:
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[width="15%",cols="^,^"]
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|========
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| T1 | T2
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|========
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When moving terminal 2 to the bottom, the table will be expanded again.
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[width="15%",cols="^,^"]
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|========
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| T1 |
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| | T2
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|========
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You can really think of the layout table like a traditional HTML table, if
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you’ve ever designed one. Especially col- and rowspan work similarly. Below,
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you see an example of colspan=2 for the first container (which has T1 as
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window).
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[width="15%",cols="^asciidoc"]
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|========
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| T1
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[cols="^,^",frame="none"]
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!========
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! T2 ! T3
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!========
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|========
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Furthermore, you can freely resize table cells.
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/////////////////////////////////////////////////////////////////////////////////
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== Files
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include/atoms.xmacro::
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A file containing all X11 atoms which i3 uses. This file will be included
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various times (for defining, requesting and receiving the atoms), each time
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with a different definition of xmacro().
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include/data.h::
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Contains data definitions used by nearly all files. You really need to read
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this first.
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include/*.h::
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Contains forward definitions for all public functions, as well as
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doxygen-compatible comments (so if you want to get a bit more of the big
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picture, either browse all header files or use doxygen if you prefer that).
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src/cfgparse.l::
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Contains the lexer for i3’s configuration file, written for +flex(1)+.
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src/cfgparse.y::
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Contains the parser for i3’s configuration file, written for +bison(1)+.
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src/click.c::
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Contains all functions which handle mouse button clicks (right mouse button
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clicks initiate resizing and thus are relatively complex).
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src/cmdparse.l::
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Contains the lexer for i3 commands, written for +flex(1)+.
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src/cmdparse.y::
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Contains the parser for i3 commands, written for +bison(1)+.
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src/con.c::
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Contains all functions which deal with containers directly (creating
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containers, searching containers, getting specific properties from containers,
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…).
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src/config.c::
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Contains all functions handling the configuration file (calling the parser
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(src/cfgparse.y) with the correct path, switching key bindings mode).
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src/debug.c::
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Contains debugging functions to print unhandled X events.
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src/ewmh.c::
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Functions to get/set certain EWMH properties easily.
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src/floating.c::
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Contains functions for floating mode (mostly resizing/dragging).
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src/handlers.c::
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Contains all handlers for all kinds of X events (new window title, new hints,
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unmapping, key presses, button presses, …).
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src/ipc.c::
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Contains code for the IPC interface.
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src/load_layout.c::
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Contains code for loading layouts from JSON files.
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src/log.c::
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Handles the setting of loglevels, contains the logging functions.
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src/main.c::
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Initializes the window manager.
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src/manage.c::
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Looks at existing or new windows and decides whether to manage them. If so, it
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reparents the window and inserts it into our data structures.
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src/match.c::
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A "match" is a data structure which acts like a mask or expression to match
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certain windows or not. For example, when using commands, you can specify a
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command like this: [title="*Firefox*"] kill. The title member of the match
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data structure will then be filled and i3 will check each window using
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match_matches_window() to find the windows affected by this command.
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src/move.c::
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Contains code to move a container in a specific direction.
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src/output.c::
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Functions to handle CT_OUTPUT cons.
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src/randr.c::
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The RandR API is used to get (and re-query) the configured outputs (monitors,
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…).
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src/render.c::
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Renders the tree data structure by assigning coordinates to every node. These
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values will later be pushed to X11 in +src/x.c+.
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src/resize.c::
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Contains the functions to resize containers.
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src/sighandler.c::
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Handles +SIGSEGV+, +SIGABRT+ and +SIGFPE+ by showing a dialog that i3 crashed.
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You can chose to let it dump core, to restart it in-place or to restart it
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in-place but forget about the layout.
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src/tree.c::
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Contains functions which open or close containers in the tree, change focus or
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cleanup ("flatten") the tree. See also +src/move.c+ for another similar
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function, which was moved into its own file because it is so long.
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src/util.c::
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Contains useful functions which are not really dependant on anything.
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src/window.c::
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Handlers to update X11 window properties like +WM_CLASS+, +_NET_WM_NAME+,
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+CLIENT_LEADER+, etc.
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src/workspace.c::
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Contains all functions related to workspaces (displaying, hiding, renaming…)
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src/x.c::
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Transfers our in-memory tree (see +src/render.c+) to X11.
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src/xcb.c::
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Contains wrappers to use xcb more easily.
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src/xcursor.c::
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XCursor functions (for cursor themes).
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src/xinerama.c::
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Legacy support for Xinerama. See +src/randr.c+ for the preferred API.
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== Data structures
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See include/data.h for documented data structures. The most important ones are
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explained right here.
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/////////////////////////////////////////////////////////////////////////////////
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// TODO: update image
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image:bigpicture.png[The Big Picture]
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/////////////////////////////////////////////////////////////////////////////////
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So, the hierarchy is:
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. *X11 root window*, the root container
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. *Output container* (LVDS1 in this example)
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. *Content container* (there are also containers for dock windows)
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. *Workspaces* (Workspace 1 in this example, with horizontal orientation)
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. *Split container* (vertically split)
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. *X11 window containers*
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The data type is +Con+, in all cases.
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=== X11 root window
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The X11 root window is a single window per X11 display (a display is identified
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by +:0+ or +:1+ etc.). The root window is what you draw your background image
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on. It spans all the available outputs, e.g. +VGA1+ is a specific part of the
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root window and +LVDS1+ is a specific part of the root window.
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=== Output container
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Every active output obtained through RandR is represented by one output
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container. Outputs are considered active when a mode is configured (meaning
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something is actually displayed on the output) and the output is not a clone.
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For example, if your notebook has a screen resolution of 1280x800 px and you
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connect a video projector with a resolution of 1024x768 px, set it up in clone
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mode (+xrandr \--output VGA1 \--mode 1024x768 \--same-as LVDS1+), i3 will
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reduce the resolution to the lowest common resolution and disable one of the
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cloned outputs afterwards.
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However, if you configure it using +xrandr \--output VGA1 \--mode 1024x768
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\--right-of LVDS1+, i3 will set both outputs active. For each output, a new
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workspace will be assigned. New workspaces are created on the output you are
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currently on.
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=== Content container
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Each output has multiple children. Two of them are dock containers which hold
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dock clients. The other one is the content container, which holds the actual
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content (workspaces) of this output.
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=== Workspace
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A workspace is identified by its name. Basically, you could think of
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workspaces as different desks in your office, if you like the desktop
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metaphor. They just contain different sets of windows and are completely
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separate of each other. Other window managers also call this ``Virtual
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desktops''.
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=== Split container
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A split container is a container which holds an arbitrary amount of split
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containers or X11 window containers. It has an orientation (horizontal or
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vertical) and a layout.
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Split containers (and X11 window containers, which are a subtype of split
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containers) can have different border styles.
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=== X11 window container
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An X11 window container holds exactly one X11 window. These are the leaf nodes
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of the layout tree, they cannot have any children.
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== List/queue macros
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i3 makes heavy use of the list macros defined in BSD operating systems. To
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ensure that the operating system on which i3 is compiled has all the expected
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features, i3 comes with `include/queue.h`. On BSD systems, you can use man
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`queue(3)`. On Linux, you have to use google (or read the source).
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The lists used are +SLIST+ (single linked lists), +CIRCLEQ+ (circular
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queues) and +TAILQ+ (tail queues). Usually, only forward traversal is necessary,
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so an `SLIST` works fine. If inserting elements at arbitrary positions or at
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the end of a list is necessary, a +TAILQ+ is used instead. However, for the
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windows inside a container, a +CIRCLEQ+ is necessary to go from the currently
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selected window to the window above/below.
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== Naming conventions
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There is a row of standard variables used in many events. The following names
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should be chosen for those:
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* ``conn'' is the xcb_connection_t
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* ``event'' is the event of the particular type
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* ``con'' names a container
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* ``current'' is a loop variable when using +TAILQ_FOREACH+ etc.
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== Startup (src/mainx.c, main())
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* Establish the xcb connection
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* Check for XKB extension on the separate X connection, load Xcursor
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* Check for RandR screens (with a fall-back to Xinerama)
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* Grab the keycodes for which bindings exist
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* Manage all existing windows
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* Enter the event loop
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== Keybindings
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=== Grabbing the bindings
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Grabbing the bindings is quite straight-forward. You pass X your combination of
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modifiers and the keycode you want to grab and whether you want to grab them
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actively or passively. Most bindings (everything except for bindings using
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Mode_switch) are grabbed passively, that is, just the window manager gets the
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event and cannot replay it.
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We need to grab bindings that use Mode_switch actively because of a bug in X.
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When the window manager receives the keypress/keyrelease event for an actively
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grabbed keycode, it has to decide what to do with this event: It can either
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replay it so that other applications get it or it can prevent other
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applications from receiving it.
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So, why do we need to grab keycodes actively? Because X does not set the
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state-property of keypress/keyrelease events properly. The Mode_switch bit is
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not set and we need to get it using XkbGetState. This means we cannot pass X
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our combination of modifiers containing Mode_switch when grabbing the key and
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therefore need to grab the keycode itself without any modifiers. This means,
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if you bind Mode_switch + keycode 38 ("a"), i3 will grab keycode 38 ("a") and
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check on each press of "a" if the Mode_switch bit is set using XKB. If yes, it
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will handle the event, if not, it will replay the event.
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=== Handling a keypress
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As mentioned in "Grabbing the bindings", upon a keypress event, i3 first gets
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the correct state.
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Then, it looks through all bindings and gets the one which matches the received
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event.
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The bound command is parsed by the cmdparse lexer/parser, see +parse_cmd+ in
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+src/cmdparse.y+.
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== Manage windows (src/main.c, manage_window() and reparent_window())
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`manage_window()` does some checks to decide whether the window should be
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managed at all:
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* Windows have to be mapped, that is, visible on screen
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* The override_redirect must not be set. Windows with override_redirect shall
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not be managed by a window manager
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Afterwards, i3 gets the intial geometry and reparents the window (see
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`reparent_window()`) if it wasn’t already managed.
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Reparenting means that for each window which is reparented, a new window,
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slightly larger than the original one, is created. The original window is then
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reparented to the bigger one (called "frame").
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After reparenting, the window type (`_NET_WM_WINDOW_TYPE`) is checked to see
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whether this window is a dock (`_NET_WM_WINDOW_TYPE_DOCK`), like dzen2 for
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example. Docks are handled differently, they don’t have decorations and are not
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assigned to a specific container. Instead, they are positioned at the bottom
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or top of the screen (in the appropriate dock area containers). To get the
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height which needs to be reserved for the window, the `_NET_WM_STRUT_PARTIAL`
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property is used.
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Furthermore, the list of assignments (to other workspaces, which may be on
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other screens) is checked. If the window matches one of the user’s criteria,
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it may either be put in floating mode or moved to a different workspace. If the
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target workspace is not visible, the window will not be mapped.
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== What happens when an application is started?
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i3 does not care for applications. All it notices is when new windows are
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mapped (see `src/handlers.c`, `handle_map_request()`). The window is then
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reparented (see section "Manage windows").
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After reparenting the window, `render_tree()` is called which renders the
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internal layout table. The new window has been placed in the currently focused
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container and therefore the new window and the old windows (if any) need to be
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moved/resized so that the currently active layout (default/stacking/tabbed mode)
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is rendered correctly. To move/resize windows, a window is ``configured'' in
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X11-speak.
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Some applications, such as MPlayer obviously assume the window manager is
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stupid and try to configure their windows by themselves. This generates an
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event called configurerequest. i3 handles these events and tells the window the
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size it had before the configurerequest (with the exception of not yet mapped
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windows, which get configured like they want to, and floating windows, which
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can reconfigure themselves).
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== _NET_WM_STATE
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Only the _NET_WM_STATE_FULLSCREEN atom is handled. It calls
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``toggle_fullscreen()'' for the specific client which just configures the
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client to use the whole screen on which it currently is. Also, it is set as
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fullscreen_client for the i3Screen.
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== WM_NAME
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When the WM_NAME property of a window changes, its decoration (containing the
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title) is re-rendered. Note that WM_NAME is in COMPOUND_TEXT encoding which is
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totally uncommon and cumbersome. Therefore, the _NET_WM_NAME atom will be used
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if present.
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== _NET_WM_NAME
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Like WM_NAME, this atom contains the title of a window. However, _NET_WM_NAME
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is encoded in UTF-8. i3 will recode it to UCS-2 in order to be able to pass it
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to X. Using an appropriate font (ISO-10646), you can see most special
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characters (every special character contained in your font).
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== Size hints
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Size hints specify the minimum/maximum size for a given window as well as its
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aspect ratio. This is important for clients like mplayer, who only set the
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aspect ratio and resize their window to be as small as possible (but only with
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some video outputs, for example in Xv, while when using x11, mplayer does the
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necessary centering for itself).
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So, when an aspect ratio was specified, i3 adjusts the height of the window
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until the size maintains the correct aspect ratio. For the code to do this, see
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src/layout.c, function resize_client().
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== Rendering (src/layout.c, render_layout() and render_container())
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Rendering in i3 version 4 is the step which assigns the correct sizes for
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borders, decoration windows, child windows and the stacking order of all
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windows. In a separate step (+x_push_changes()+), these changes are pushed to
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X11.
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Keep in mind that all these properties (+rect+, +window_rect+ and +deco_rect+)
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are temporary, meaning they will be overwritten by calling +render_con+.
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Persistent position/size information is kept in +geometry+.
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The entry point for every rendering operation (except for the case of moving
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floating windows around) currently is +tree_render()+ which will re-render
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everything that’s necessary (for every output, only the currently displayed
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workspace is rendered). This behavior is expected to change in the future,
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since for a lot of updates, re-rendering everything is not actually necessary.
|
||
Focus was on getting it working correct, not getting it work very fast.
|
||
|
||
What +tree_render()+ actually does is calling +render_con()+ on the root
|
||
container and then pushing the changes to X11. The following sections talk
|
||
about the different rendering steps, in the order of "top of the tree" (root
|
||
container) to the bottom.
|
||
|
||
=== Rendering the root container
|
||
|
||
The i3 root container (`con->type == CT_ROOT`) represents the X11 root window.
|
||
It contains one child container for every output (like LVDS1, VGA1, …), which
|
||
is available on your computer.
|
||
|
||
Rendering the root will first render all tiling windows and then all floating
|
||
windows. This is necessary because a floating window can be positioned in such
|
||
a way that it is visible on two different outputs. Therefore, by first
|
||
rendering all the tiling windows (of all outputs), we make sure that floating
|
||
windows can never be obscured by tiling windows.
|
||
|
||
Essentially, though, this code path will just call +render_con()+ for every
|
||
output and +x_raise_con(); render_con()+ for every floating window.
|
||
|
||
In the special case of having a "global fullscreen" window (fullscreen mode
|
||
spanning all outputs), a shortcut is taken and +x_raise_con(); render_con()+ is
|
||
only called for the global fullscreen window.
|
||
|
||
=== Rendering an output
|
||
|
||
Output containers (`con->layout == L_OUTPUT`) represent a hardware output like
|
||
LVDS1, VGA1, etc. An output container has three children (at the moment): One
|
||
content container (having workspaces as children) and the top/bottom dock area
|
||
containers.
|
||
|
||
The rendering happens in the function +render_l_output()+ in the following
|
||
steps:
|
||
|
||
1. Find the content container (`con->type == CT_CON`)
|
||
2. Get the currently visible workspace (+con_get_fullscreen_con(content,
|
||
CF_OUTPUT)+).
|
||
3. If there is a fullscreened window on that workspace, directly render it and
|
||
return, thus ignoring the dock areas.
|
||
4. Sum up the space used by all the dock windows (they have a variable height
|
||
only).
|
||
5. Set the workspace rects (x/y/width/height) based on the position of the
|
||
output (stored in `con->rect`) and the usable space
|
||
(`con->rect.{width,height}` without the space used for dock windows).
|
||
6. Recursively raise and render the output’s child containers (meaning dock
|
||
area containers and the content container).
|
||
|
||
=== Rendering a workspace or split container
|
||
|
||
From here on, there really is no difference anymore. All containers are of
|
||
`con->type == CT_CON` (whether workspace or split container) and some of them
|
||
have a `con->window`, meaning they represent an actual window instead of a
|
||
split container.
|
||
|
||
==== Default layout
|
||
|
||
In default layout, containers are placed horizontally or vertically next to
|
||
each other (depending on the `con->orientation`). If a child is a leaf node (as
|
||
opposed to a split container) and has border style "normal", appropriate space
|
||
will be reserved for its window decoration.
|
||
|
||
==== Stacked layout
|
||
|
||
In stacked layout, only the focused window is actually shown (this is achieved
|
||
by calling +x_raise_con()+ in reverse focus order at the end of +render_con()+).
|
||
|
||
The available space for the focused window is the size of the container minus
|
||
the height of the window decoration for all windows inside this stacked
|
||
container.
|
||
|
||
If border style is "1pixel" or "none", no window decoration height will be
|
||
reserved (or displayed later on), unless there is more than one window inside
|
||
the stacked container.
|
||
|
||
==== Tabbed layout
|
||
|
||
Tabbed layout works precisely like stacked layout, but the window decoration
|
||
position/size is different: They are placed next to each other on a single line
|
||
(fixed height).
|
||
|
||
==== Dock area layout
|
||
|
||
This is a special case. Users cannot chose the dock area layout, but it will be
|
||
set for the dock area containers. In the dockarea layout (at the moment!),
|
||
windows will be placed above each other.
|
||
|
||
=== Rendering a window
|
||
|
||
A window’s size and position will be determined in the following way:
|
||
|
||
1. Subtract the border if border style is not "none" (but "normal" or "1pixel").
|
||
2. Subtract the X11 border, if the window has an X11 border > 0.
|
||
3. Obey the aspect ratio of the window (think MPlayer).
|
||
4. Obey the height- and width-increments of the window (think terminal emulator
|
||
which can only be resized in one-line or one-character steps).
|
||
|
||
== Pushing updates to X11 / Drawing
|
||
|
||
A big problem with i3 before version 4 was that we just sent requests to X11
|
||
anywhere in the source code. This was bad because nobody could understand the
|
||
entirety of our interaction with X11, it lead to subtle bugs and a lot of edge
|
||
cases which we had to consider all over again.
|
||
|
||
Therefore, since version 4, we have a single file, +src/x.c+, which is
|
||
responsible for repeatedly transferring parts of our tree datastructure to X11.
|
||
|
||
+src/x.c+ consists of multiple parts:
|
||
|
||
1. The state pushing: +x_push_changes()+, which calls +x_push_node()+.
|
||
2. State modification functions: +x_con_init+, +x_reinit+,
|
||
+x_reparent_child+, +x_move_win+, +x_con_kill+, +x_raise_con+, +x_set_name+
|
||
and +x_set_warp_to+.
|
||
3. Expose event handling (drawing decorations): +x_deco_recurse()+ and
|
||
+x_draw_decoration()+.
|
||
|
||
=== Pushing state to X11
|
||
|
||
In general, the function +x_push_changes+ should be called to push state
|
||
changes. Only when the scope of the state change is clearly defined (for
|
||
example only the title of a window) and its impact is known beforehand, one can
|
||
optimize this and call +x_push_node+ on the appropriate con directly.
|
||
|
||
+x_push_changes+ works in the following steps:
|
||
|
||
1. Clear the eventmask for all mapped windows. This leads to not getting
|
||
useless ConfigureNotify or EnterNotify events which are caused by our
|
||
requests. In general, we only want to handle user input.
|
||
2. Stack windows above each other, in reverse stack order (starting with the
|
||
most obscured/bottom window). This is relevant for floating windows which
|
||
can overlap each other, but also for tiling windows in stacked or tabbed
|
||
containers. We also update the +_NET_CLIENT_LIST_STACKING+ hint which is
|
||
necessary for tab drag and drop in Chromium.
|
||
3. +x_push_node+ will be called for the root container, recursively calling
|
||
itself for the container’s children. This function actually pushes the
|
||
state, see the next paragraph.
|
||
4. If the pointer needs to be warped to a different position (for example when
|
||
changing focus to a differnt output), it will be warped now.
|
||
5. The eventmask is restored for all mapped windows.
|
||
6. Window decorations will be rendered by calling +x_deco_recurse+ on the root
|
||
container, which then recursively calls itself for the children.
|
||
7. If the input focus needs to be changed (because the user focused a different
|
||
window), it will be updated now.
|
||
8. +x_push_node_unmaps+ will be called for the root container. This function
|
||
only pushes UnmapWindow requests. Separating the state pushing is necessary
|
||
to handle fullscreen windows (and workspace switches) in a smooth fashion:
|
||
The newly visible windows should be visible before the old windows are
|
||
unmapped.
|
||
|
||
+x_push_node+ works in the following steps:
|
||
|
||
1. Update the window’s +WM_NAME+, if changed (the +WM_NAME+ is set on i3
|
||
containers mainly for debugging purposes).
|
||
2. Reparents a child window into the i3 container if the container was created
|
||
for a specific managed window.
|
||
3. If the size/position of the i3 container changed (due to opening a new
|
||
window or switching layouts for example), the window will be reconfigured.
|
||
Also, the pixmap which is used to draw the window decoration/border on is
|
||
reconfigured (pixmaps are size-dependent).
|
||
4. Size/position for the child window is adjusted.
|
||
5. The i3 container is mapped if it should be visible and was not yet mapped.
|
||
When mapping, +WM_STATE+ is set to +WM_STATE_NORMAL+. Also, the eventmask of
|
||
the child window is updated and the i3 container’s contents are copied from
|
||
the pixmap.
|
||
6. +x_push_node+ is called recursively for all children of the current
|
||
container.
|
||
|
||
+x_push_node_unmaps+ handles the remaining case of an i3 container being
|
||
unmapped if it should not be visible anymore. +WM_STATE+ will be set to
|
||
+WM_STATE_WITHDRAWN+.
|
||
|
||
|
||
=== Drawing window decorations/borders/backgrounds
|
||
|
||
+x_draw_decoration+ draws window decorations. It is run for every leaf
|
||
container (representing an actual X11 window) and for every non-leaf container
|
||
which is in a stacked/tabbed container (because stacked/tabbed containers
|
||
display a window decoration for split containers, which at the moment just says
|
||
"another container").
|
||
|
||
Then, parameters are collected to be able to determine whether this decoration
|
||
drawing is actually necessary or was already done. This saves a substantial
|
||
number of redraws (depending on your workload, but far over 50%).
|
||
|
||
Assuming that we need to draw this decoration, we start by filling the empty
|
||
space around the child window (think of MPlayer with a specific aspect ratio)
|
||
in the user-configured client background color.
|
||
|
||
Afterwards, we draw the appropriate border (in case of border styles "normal"
|
||
and "1pixel") and the top bar (in case of border style "normal").
|
||
|
||
The last step is drawing the window title on the top bar.
|
||
|
||
|
||
/////////////////////////////////////////////////////////////////////////////////
|
||
|
||
== Resizing containers
|
||
|
||
By clicking and dragging the border of a container, you can resize the whole
|
||
column (respectively row) which this container is in. This is necessary to keep
|
||
the table layout working and consistent.
|
||
|
||
The resizing works similarly to the resizing of floating windows or movement of
|
||
floating windows:
|
||
|
||
* A new, invisible window with the size of the root window is created
|
||
(+grabwin+)
|
||
* Another window, 2px width and as high as your screen (or vice versa for
|
||
horizontal resizing) is created. Its background color is the border color and
|
||
it is only there to inform the user how big the container will be (it
|
||
creates the impression of dragging the border out of the container).
|
||
* The +drag_pointer+ function of +src/floating.c+ is called to grab the pointer
|
||
and enter its own event loop which will pass all events (expose events) but
|
||
motion notify events. This function then calls the specified callback
|
||
(+resize_callback+) which does some boundary checking and moves the helper
|
||
window. As soon as the mouse button is released, this loop will be
|
||
terminated.
|
||
* The new width_factor for each involved column (respectively row) will be
|
||
calculated.
|
||
|
||
/////////////////////////////////////////////////////////////////////////////////
|
||
|
||
== User commands / commandmode (src/cmdparse.{l,y})
|
||
|
||
*********************************************************************************
|
||
This section has not been updated for v4.0 yet, sorry! We wanted to release on
|
||
time, but we will update this soon. Please talk to us on IRC if you need to
|
||
know stuff *NOW* :).
|
||
*********************************************************************************
|
||
|
||
/////////////////////////////////////////////////////////////////////////////////
|
||
|
||
|
||
Like in vim, you can control i3 using commands. They are intended to be a
|
||
powerful alternative to lots of shortcuts, because they can be combined. There
|
||
are a few special commands, which are the following:
|
||
|
||
exec <command>::
|
||
Starts the given command by passing it to `/bin/sh`.
|
||
|
||
restart::
|
||
Restarts i3 by executing `argv[0]` (the path with which you started i3) without
|
||
forking.
|
||
|
||
w::
|
||
"With". This is used to select a bunch of windows. Currently, only selecting
|
||
the whole container in which the window is in, is supported by specifying "w".
|
||
|
||
f, s, d::
|
||
Toggle fullscreen, stacking, default mode for the current window/container.
|
||
|
||
The other commands are to be combined with a direction. The directions are h,
|
||
j, k and l, like in vim (h = left, j = down, k = up, l = right). When you just
|
||
specify the direction keys, i3 will move the focus in that direction. You can
|
||
provide "m" or "s" before the direction to move a window respectively or snap.
|
||
|
||
/////////////////////////////////////////////////////////////////////////////////
|
||
|
||
== Moving containers
|
||
|
||
The movement code is pretty delicate. You need to consider all cases before
|
||
making any changes or before being able to fully understand how it works.
|
||
|
||
=== Case 1: Moving inside the same container
|
||
|
||
The reference layout for this case is a single workspace in horizontal
|
||
orientation with two containers on it. Focus is on the left container (1).
|
||
|
||
|
||
[width="15%",cols="^,^"]
|
||
|========
|
||
| 1 | 2
|
||
|========
|
||
|
||
When moving the left window to the right (command +move right+), tree_move will
|
||
look for a container with horizontal orientation and finds the parent of the
|
||
left container, that is, the workspace. Afterwards, it runs the code branch
|
||
commented with "the easy case": it calls TAILQ_NEXT to get the container right
|
||
of the current one and swaps both containers.
|
||
|
||
=== Case 2: Move a container into a split container
|
||
|
||
The reference layout for this case is a horizontal workspace with two
|
||
containers. The right container is a v-split with two containers. Focus is on
|
||
the left container (1).
|
||
|
||
[width="15%",cols="^,^"]
|
||
|========
|
||
1.2+^.^| 1 | 2
|
||
| 3
|
||
|========
|
||
|
||
When moving to the right (command +move right+), i3 will work like in case 1
|
||
("the easy case"). However, as the right container is not a leaf container, but
|
||
a v-split, the left container (1) will be inserted at the right position (below
|
||
2, assuming that 2 is focused inside the v-split) by calling +insert_con_into+.
|
||
|
||
+insert_con_into+ detaches the container from its parent and inserts it
|
||
before/after the given target container. Afterwards, the on_remove_child
|
||
callback is called on the old parent container which will then be closed, if
|
||
empty.
|
||
|
||
Afterwards, +con_focus+ will be called to fix the focus stack and the tree will
|
||
be flattened.
|
||
|
||
=== Case 3: Moving to non-existant top/bottom
|
||
|
||
Like in case 1, the reference layout for this case is a single workspace in
|
||
horizontal orientation with two containers on it. Focus is on the left
|
||
container:
|
||
|
||
[width="15%",cols="^,^"]
|
||
|========
|
||
| 1 | 2
|
||
|========
|
||
|
||
This time however, the command is +move up+ or +move down+. tree_move will look
|
||
for a container with vertical orientation. As it will not find any,
|
||
+same_orientation+ is NULL and therefore i3 will perform a forced orientation
|
||
change on the workspace by creating a new h-split container, moving the
|
||
workspace contents into it and then changing the workspace orientation to
|
||
vertical. Now it will again search for parent containers with vertical
|
||
orientation and it will find the workspace.
|
||
|
||
This time, the easy case code path will not be run as we are not moving inside
|
||
the same container. Instead, +insert_con_into+ will be called with the focused
|
||
container and the container above/below the current one (on the level of
|
||
+same_orientation+).
|
||
|
||
Now, +con_focus+ will be called to fix the focus stack and the tree will be
|
||
flattened.
|
||
|
||
=== Case 4: Moving to existant top/bottom
|
||
|
||
The reference layout for this case is a vertical workspace with two containers.
|
||
The bottom one is a h-split containing two containers (1 and 2). Focus is on
|
||
the bottom left container (1).
|
||
|
||
[width="15%",cols="^,^"]
|
||
|========
|
||
2+| 3
|
||
| 1 | 2
|
||
|========
|
||
|
||
This case is very much like case 3, only this time the forced workspace
|
||
orientation change does not need to be performed because the workspace already
|
||
is in vertical orientation.
|
||
|
||
=== Case 5: Moving in one-child h-split
|
||
|
||
The reference layout for this case is a horizontal workspace with two
|
||
containers having a v-split on the left side with a one-child h-split on the
|
||
bottom. Focus is on the bottom left container (2(h)):
|
||
|
||
[width="15%",cols="^,^"]
|
||
|========
|
||
| 1 1.2+^.^| 3
|
||
| 2(h)
|
||
|========
|
||
|
||
In this case, +same_orientation+ will be set to the h-split container around
|
||
the focused container. However, when trying the easy case, the next/previous
|
||
container +swap+ will be NULL. Therefore, i3 will search again for a
|
||
+same_orientation+ container, this time starting from the parent of the h-split
|
||
container.
|
||
|
||
After determining a new +same_orientation+ container (if it is NULL, the
|
||
orientation will be force-changed), this case is equivalent to case 2 or case
|
||
4.
|
||
|
||
|
||
=== Case 6: Floating containers
|
||
|
||
The reference layout for this case is a horizontal workspace with two
|
||
containers plus one floating h-split container. Focus is on the floating
|
||
container.
|
||
|
||
TODO: nice illustration. table not possible?
|
||
|
||
When moving up/down, the container needs to leave the floating container and it
|
||
needs to be placed on the workspace (at workspace level). This is accomplished
|
||
by calling the function +attach_to_workspace+.
|
||
|
||
== Click handling
|
||
|
||
Without much ado, here is the list of cases which need to be considered:
|
||
|
||
* click to focus (tiling + floating) and raise (floating)
|
||
* click to focus/raise when in stacked/tabbed mode
|
||
* floating_modifier + left mouse button to drag a floating con
|
||
* floating_modifier + right mouse button to resize a floating con
|
||
* click on decoration in a floating con to either initiate a resize (if there
|
||
is more than one child in the floating con) or to drag the
|
||
floating con (if it’s the one at the top).
|
||
* click on border in a floating con to resize the floating con
|
||
* floating_modifier + right mouse button to resize a tiling con
|
||
* click on border/decoration to resize a tiling con
|
||
|
||
== Gotchas
|
||
|
||
* Forgetting to call `xcb_flush(conn);` after sending a request. This usually
|
||
leads to code which looks like it works fine but which does not work under
|
||
certain conditions.
|
||
|
||
== Using git / sending patches
|
||
|
||
For a short introduction into using git, see
|
||
http://www.spheredev.org/wiki/Git_for_the_lazy or, for more documentation, see
|
||
http://git-scm.com/documentation
|
||
|
||
When you want to send a patch because you fixed a bug or implemented a cool
|
||
feature (please talk to us before working on features to see whether they are
|
||
maybe already implemented, not possible for some some reason, or don’t fit
|
||
into the concept), please use git to create a patchfile.
|
||
|
||
First of all, update your working copy to the latest version of the master
|
||
branch:
|
||
|
||
--------
|
||
git pull
|
||
--------
|
||
|
||
Afterwards, make the necessary changes for your bugfix/feature. Then, review
|
||
the changes using +git diff+ (you might want to enable colors in the diff using
|
||
+git config diff.color auto+). When you are definitely done, use +git commit
|
||
-a+ to commit all changes you’ve made.
|
||
|
||
Then, use the following command to generate a patchfile which we can directly
|
||
apply to the branch, preserving your commit message and name:
|
||
|
||
-----------------------
|
||
git format-patch origin
|
||
-----------------------
|
||
|
||
Just send us the generated file via email.
|
||
|
||
== Thought experiments
|
||
|
||
In this section, we collect thought experiments, so that we don’t forget our
|
||
thoughts about specific topics. They are not necessary to get into hacking i3,
|
||
but if you are interested in one of the topics they cover, you should read them
|
||
before asking us why things are the way they are or why we don’t implement
|
||
things.
|
||
|
||
=== Using cgroups per workspace
|
||
|
||
cgroups (control groups) are a linux-only feature which provides the ability to
|
||
group multiple processes. For each group, you can individually set resource
|
||
limits, like allowed memory usage. Furthermore, and more importantly for our
|
||
purposes, they serve as a namespace, a label which you can attach to processes
|
||
and their children.
|
||
|
||
One interesting use for cgroups is having one cgroup per workspace (or
|
||
container, doesn’t really matter). That way, you could set different priorities
|
||
and have a workspace for important stuff (say, writing a LaTeX document or
|
||
programming) and a workspace for unimportant background stuff (say,
|
||
JDownloader). Both tasks can obviously consume a lot of I/O resources, but in
|
||
this example it doesn’t really matter if JDownloader unpacks the download a
|
||
minute earlier or not. However, your compiler should work as fast as possible.
|
||
Having one cgroup per workspace, you would assign more resources to the
|
||
programming workspace.
|
||
|
||
Another interesting feature is that an inherent problem of the workspace
|
||
concept could be solved by using cgroups: When starting an application on
|
||
workspace 1, then switching to workspace 2, you will get the application’s
|
||
window(s) on workspace 2 instead of the one you started it on. This is because
|
||
the window manager does not have any mapping between the process it starts (or
|
||
gets started in any way) and the window(s) which appear.
|
||
|
||
Imagine for example using dmenu: The user starts dmenu by pressing Mod+d, dmenu
|
||
gets started with PID 3390. The user then decides to launch Firefox, which
|
||
takes a long time. So he enters firefox into dmenu and presses enter. Firefox
|
||
gets started with PID 4001. When it finally finishes loading, it creates an X11
|
||
window and uses MapWindow to make it visible. This is the first time i3
|
||
actually gets in touch with Firefox. It decides to map the window, but it has
|
||
no way of knowing that this window (even though it has the _NET_WM_PID property
|
||
set to 4001) belongs to the dmenu the user started before.
|
||
|
||
How do cgroups help with this? Well, when pressing Mod+d to launch dmenu, i3
|
||
would create a new cgroup, let’s call it i3-3390-1. It launches dmenu in that
|
||
cgroup, which gets PID 3390. As before, the user enters firefox and Firefox
|
||
gets launched with PID 4001. This time, though, the Firefox process with PID
|
||
4001 is *also* member of the cgroup i3-3390-1 (because fork()ing in a cgroup
|
||
retains the cgroup property). Therefore, when mapping the window, i3 can look
|
||
up in which cgroup the process is and can establish a mapping between the
|
||
workspace and the window.
|
||
|
||
There are multiple problems with this approach:
|
||
|
||
. Every application has to properly set +_NET_WM_PID+. This is acceptable and
|
||
patches can be written for the few applications which don’t set the hint yet.
|
||
. It does only work on Linux, since cgroups are a Linux-only feature. Again,
|
||
this is acceptable.
|
||
. The main problem is that some applications create X11 windows completely
|
||
independent of UNIX processes. An example for this is Chromium (or
|
||
gnome-terminal), which, when being started a second time, communicates with
|
||
the first process and lets the first process open a new window. Therefore, if
|
||
you have a Chromium window on workspace 2 and you are currently working on
|
||
workspace 3, starting +chromium+ does not lead to the desired result (the
|
||
window will open on workspace 2).
|
||
|
||
Therefore, my conclusion is that the only proper way of fixing the "window gets
|
||
opened on the wrong workspace" problem is in the application itself. Most
|
||
modern applications support freedesktop startup-notifications which can be
|
||
used for this.
|