bspwm is a tiling window manager that represents windows as the leaves of a full binary tree.
It only responds to X events, and the messages it receives on a dedicated socket.
bspc is a program that writes messages on bspwm's socket.
bspwm doesn't handle any keyboard or pointer inputs: a third party program (e.g. sxhkd) is needed in order to translate keyboard and pointer events to bspc invocations.
The outlined architecture is the following:
PROCESS SOCKET
sxhkd --------> bspc <------> bspwm
The default configuration file is $XDG_CONFIG_HOME/bspwm/bspwmrc: this is simply a shell script that calls bspc.
Keyboard and pointer bindings are defined with sxhkd.
Example configuration files can be found in the examples directory.
bspwm holds a list of monitors.
A monitor is just a rectangle that contains desktops.
A desktop is just a pointer to a tree.
Monitors only show the tree of one desktop at a time (their focused desktop).
The tree is a partition of a monitor's rectangle into smaller rectangular regions.
Each node in a tree either has zero or two children.
Each internal node is responsible for splitting a rectangle in half.
A split is defined by two parameters: the type (horizontal or vertical) and the ratio (a real number r such that 0 < r < 1).
Each leaf node holds exactly one window.
When bspwm receives a new window, it inserts it into a window tree at the specified insertion point (a leaf) using the insertion mode specified for that insertion point.
The insertion mode tells bspwm how it should alter the tree in order to insert new windows on a given insertion point.
By default the insertion point is the focused window and its insertion mode is automatic.
The user can specify a region in the insertion point where the next new window should appear by sending a node -p|--presel-dir DIR message to bspwm.
The DIR argument allows to specify how the insertion point should be split (horizontally or vertically) and if the new window should be the first or the second child of the new internal node (the insertion point will become its brother).
After doing so the insertion point goes into manual mode.
Let's consider the following scenario:
a a a
/ \ / \ / \
1 b ---> c b ---> c b
^ / \ / \ / \ / \ / \
2 3 4 1 2 3 d 1 2 3
^ / \
5 4
^
+-----------------------+ +-----------------------+ +-----------------------+
| | | | | | | | | |
| | 2 | | 4 | 2 | | 5 | 4 | 2 |
| | | | ^ | | | ^ | | |
| 1 |-----------| |-----------|-----------| |-----------|-----------|
| ^ | | | | | | | |
| | 3 | | 1 | 3 | | 1 | 3 |
| | | | | | | | |
+-----------------------+ +-----------------------+ +-----------------------+
X Y Z
In state X, the insertion point is 1.
We send the following message to bspwm: node -p north.
Then add a new window: 4, this leads to state Y: the new internal node, c becomes a's first child.
Finally we send another message: node -p west and add window 5.
The ratio of the preselection (that ends up being the ratio of the split of the new internal node) can be changed with the node -o|--presel-ratio message.
The automatic mode, as opposed to the manual mode, doesn't require any user choice. The way the new window is inserted is determined by the value of the automatic scheme and the initial polarity settings.
When the value of the automatic scheme is longest_side, the window will be attached as if the insertion point was in manual mode and the split direction was chosen based on the dimensions of the tiling rectangle and the initial polarity.
Let's consider the following scenario, where the initial polarity is set to second_child:
1 a a
^ / \ / \
---> 1 2 ---> 1 b
^ / \
2 3
^
+-----------------------+ +-----------------------+ +-----------------------+
| | | | | | | |
| | | | | | | 2 |
| | | | | | | |
| 1 | | 1 | 2 | | 1 |-----------|
| ^ | | | ^ | | | |
| | | | | | | 3 |
| | | | | | | ^ |
+-----------------------+ +-----------------------+ +-----------------------+
X Y Z
In state X, a new window is added.
Since 1 is wide, it gets split vertically and 2 is added as a's second child given the initial polarity.
This leads to Y where we insert window 3. 2 is tall and is therefore split horizontally. 3 is once again added as b's second child.
When the value of the automatic scheme is alternate, the window will be attached as if the insertion point was in manual mode and the split direction was chosen based on the split type of the insertion point's parent and the initial polarity. If the parent is split horizontally, the insertion point will be split vertically and vice versa.
When the value of the automatic scheme is spiral, the window will take the space of the insertion point.
Let's dive into the details with the following scenario:
a a a
/ \ / \ / \
1 b ---> 1 c ---> 1 d
/ \ / \ / \
2 3 4 b 5 c
^ ^ / \ ^ / \
3 2 b 4
/ \
3 2
+-----------------------+ +-----------------------+ +-----------------------+
| | | | | | | | |
| | 2 | | | 4 | | | 5 |
| | ^ | | | ^ | | | ^ |
| 1 |-----------| | 1 |-----------| | 1 |-----------|
| | | | | | | | | 3 | |
| | 3 | | | 3 | 2 | | |-----| 4 |
| | | | | | | | | 2 | |
+-----------------------+ +-----------------------+ +-----------------------+
X Y Z
In state X, the insertion point, 2 is in automatic mode.
When we add a new window, 4, the whole tree rooted at b is reattached, as the second child of a new internal node, c.
The splitting parameters of b (type: horizontal, ratio: ½) are copied to c and b is rotated by 90° clockwise.
The tiling rectangle of 4 in state Y is equal to the tiling rectangle of 2 in state X.
Then the insertion of 5, with 4 as insertion point, leads to Z.
The spiral automatic scheme generates window spirals that rotate clockwise (resp. anti-clockwise) if the insertion point is the first (resp. second) child of its parent.
- The RandR and Xinerama protocols.
- A subset of the EWMH and ICCCM standards.