picom is a compositor based on Dana Jansens' version of xcompmgr (which itself was written by Keith Packard). It includes some improvements over the original xcompmgr, like window frame opacity and inactive window transparency.
Enabled client-side shadows on windows. Note desktop windows (windows with '_NET_WM_WINDOW_TYPE_DESKTOP') never get shadow, unless explicitly requested using the wintypes option.
Daemonize process. Fork to background after initialization. This option can only be set from the command line, setting this in the configuration file will have no effect.
Set the log level. Possible values are "TRACE", "DEBUG", "INFO", "WARN", "ERROR", in increasing level of importance. Case doesn't matter. If using the "TRACE" log level, it's better to log into a file using *--log-file*, since it can generate a huge stream of logs.
Set the log file. If *--log-file* is never specified, logs will be written to stderr. Otherwise, logs will to written to the given file, though some of the early logs might still be written to the stderr. When setting this option from the config file, it is recommended to use an absolute path.
Look for configuration file at the path. See *CONFIGURATION FILES* section below for where picom looks for a configuration file by default. Use `/dev/null` to avoid loading configuration file.
Sets the radius of rounded window corners. When > 0, the compositor will round the corners of windows. Does not interact well with *--transparent-clipping*. (defaults to 0).
Specify a list of corner radius rules. Overrides the corner radii of matching windows. This option takes precedence over the *--rounded-corners-exclude* option, and also overrides the default exclusion of fullscreen windows. The condition has the same format as *--opacity-rule*.
Disable vsync-aware frame pacing. By default, the compositor tries to make sure it only renders once per vblank interval, and also the render happens as late as possible to minimize the latency from updates to the screen. However this can sometimes cause stuttering, or even lowered frame rate. This option can be used to disable frame pacing.
Do not paint shadows on shaped windows. Note shaped windows here means windows setting its shape through X Shape extension. Those using ARGB background is beyond our control. Deprecated, use `--shadow-exclude 'bounding_shaped'` or `--shadow-exclude 'bounding_shaped && !rounded_corners'` instead.
Use EWMH '_NET_ACTIVE_WINDOW' to determine currently focused window, rather than listening to 'FocusIn'/'FocusOut' event. Might have more accuracy, provided that the WM supports it.
Unredirect all windows in some cases. Known to cause flickering when redirecting/unredirecting windows. Currently, unredirecting is triggered by following conditions:
* If the top level window is taking up the entire screen. In multi-monitor setup, this means ALL monitors.
* If there is no window.
* If a window is fullscreen according to its WM hints. (can be disabled with *--no-ewmh-fullscreen*).
* If a window requests to bypass the compositor ('_NET_WM_BYPASS_COMPOSITOR').
Windows are also unredirected unconditionally when monitors are powered off, regardless if *--unredir-if-possible* is set.
Use 'WM_CLIENT_LEADER' to group windows, and consider windows in the same group focused at the same time. This usually means windows from the same application will be considered focused or unfocused at the same time.'WM_TRANSIENT_FOR' has higher priority if *--detect-transient* is enabled, too.
Blur background of semi-transparent / ARGB windows. Bad in performance, with driver-dependent behavior. The name of the switch may change without prior notifications.
*--blur-background-frame*::
Blur background of windows when the window frame is not opaque. Implies *--blur-background*. Bad in performance, with driver-dependent behavior. The name may change.
*--blur-background-fixed*::
Use fixed blur strength rather than adjusting according to window opacity.
In other words, the matrix is formatted as a list of comma separated numbers. The first two numbers must be integers, which specify the width and height of the matrix. They must be odd numbers. Then, the following 'width * height - 1' numbers specifies the numbers in the matrix, row by row, excluding the center element.
The element in the center will either be 1.0 or varying based on opacity, depending on whether you have *--blur-background-fixed*. Yet the automatic adjustment of blur factor may not work well with a custom blur kernel.
May also be one of the predefined kernels: `3x3box` (default), `5x5box`, `7x7box`, `3x3gaussian`, `5x5gaussian`, `7x7gaussian`, `9x9gaussian`, `11x11gaussian`. All Gaussian kernels are generated with sigma = 0.84089642 . If you find yourself needing to generate custom blur kernels, you might want to try the new blur configuration (See *BLUR*).
Resize damaged region by a specific number of pixels. A positive value enlarges it while a negative one shrinks it. If the value is positive, those additional pixels will not be actually painted to screen, only used in blur calculation, and such. (Due to technical limitations, with *--use-damage*, those pixels will still be incorrectly painted to screen.) Primarily used to fix the line corruption issues of blur, in which case you should use the blur radius value here (e.g. with a 3x3 kernel, you should use `--resize-damage 1`, with a 5x5 one you use `--resize-damage 2`, and so on). May or may not work with *--glx-no-stencil*. Shrinking doesn't function correctly.
Specify a list of opacity rules, in the format `PERCENT:PATTERN`, like `50:name *= "Firefox"`. picom-trans is recommended over this. Note we don't make any guarantee about possible conflicts with other programs that set '_NET_WM_WINDOW_OPACITY' on frame or client windows.
Specify a X geometry that describes the region in which shadow should not be painted in, such as a dock window region. Use `--shadow-exclude-reg x10+0-0`, for example, if the 10 pixels on the bottom of the screen should not have shadows painted on.
Specify the backend to use: `xrender`, `glx`, or `xr_glx_hybrid`. `xrender` is the default one.
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* `xrender` backend performs all rendering operations with X Render extension. It is what `xcompmgr` uses, and is generally a safe fallback when you encounter rendering artifacts or instability.
* `glx` (OpenGL) backend performs all rendering operations with OpenGL. It is more friendly to some VSync methods, and has significantly superior performance on color inversion (*--invert-color-include*) or blur (*--blur-background*). It requires proper OpenGL 2.0 support from your driver and hardware. You may wish to look at the GLX performance optimization options below. *--xrender-sync-fence* might be needed on some systems to avoid delay in changes of screen contents.
* `xr_glx_hybrid` backend renders the updated screen contents with X Render and presents it on the screen with GLX. It attempts to address the rendering issues some users encountered with GLX backend and enables the better VSync of GLX backends. *--vsync-use-glfinish* might fix some rendering issues with this backend.
GLX backend: Avoid using stencil buffer, useful if you don't have a stencil buffer. Might cause incorrect opacity when rendering transparent content (but never practically happened) and may not work with *--blur-background*. My tests show a 15% performance boost. Recommended.
GLX backend: Avoid rebinding pixmap on window damage. Probably could improve performance on rapid window content changes, but is known to break things on some drivers (LLVMpipe, xf86-video-intel, etc.). Recommended if it works.
Disable the use of damage information. This cause the whole screen to be redrawn every time, instead of the part of the screen has actually changed. Potentially degrades the performance, but might fix some artifacts.
Use X Sync fence to sync clients' draw calls, to make sure all draw calls are finished before picom starts drawing. Needed on nvidia-drivers with GLX backend for some users.
GLX backend: Use specified GLSL fragment shader for rendering window contents. See `compton-default-fshader-win.glsl` and `compton-fake-transparency-fshader-win.glsl` in the source tree for examples. Only works with *--legacy-backends* enabled.
Dimming bright windows so their brightness doesn't exceed this set value. Brightness of a window is estimated by averaging all pixels in the window, so this could comes with a performance hit. Setting this to 1.0 disables this behaviour. Requires *--use-damage* to be disabled. (default: 1.0)
Specify a list of conditions of windows that should never have transparent clipping applied. Useful for screenshot tools, where you need to be able to see through transparent parts of the window.
Specify GLSL fragment shader path for rendering window contents. Does not work when *--legacy-backends* is enabled. Shader is searched first relative to the directory the configuration file is in, then in the usual places for a configuration file. See section *SHADER INTERFACE* below for more details on the interface.
Specify GLSL fragment shader path for rendering window contents using patterns. Similar to *--opacity-rule*, arguments should be in the format of 'SHADER:CONDITION', e.g. "shader.frag:name = \'window\'". Leading and trailing whitespaces in 'SHADER' will be trimmed. If 'SHADER' is "default", then the default shader will be used for the matching windows. (This also unfortunately means you can't use a shader file named "default"). Does not work when *--legacy-backends* is enabled.
Use higher precision during rendering, and apply dither when presenting the rendered screen. Reduces banding artifacts, but might cause performance degradation. Only works with OpenGL.
'TARGET' is either a predefined target name, or the name of a window property to match. Supported predefined targets are `id`, `x`, `y`, `x2` (`x` + `widthb`), `y2` (like `x2`), `width`, `height`, `widthb` (`width` + 2 * `border_width`), `heightb` (like `widthb`), `border_width`, `fullscreen`, `override_redirect`, `argb` (whether the window has an ARGB visual), `focused`, `wmwin` (whether the window looks like a WM window, i.e. has no child window with `WM_STATE` and is not override-redirected), `bounding_shaped`, `rounded_corners` (requires *--detect-rounded-corners*), `client` (ID of client window), `window_type` (window type in string), `leader` (ID of window leader), `name`, `class_g` (= `WM_CLASS[1]`), `class_i` (= `WM_CLASS[0]`), and `role`.
'INDEX' (optional) is the index number of the property to look up. For example, `[2]` means look at the third value in the property. If not specified, the first value (index `[0]`) is used implicitly. Use the special value `[*]` to perform matching against all available property values using logical OR. Do not specify it for predefined targets.
'FORMAT' (optional) specifies the format of the property, 8, 16, or 32. On absence we use format X reports. Do not specify it for predefined or string targets.
'TYPE' is a single character representing the type of the property to match for: `c` for 'CARDINAL', `a` for 'ATOM', `w` for 'WINDOW', `d` for 'DRAWABLE', `s` for 'STRING' (and any other string types, such as 'UTF8_STRING'). Do not specify it for predefined targets.
'OP QUALIFIER' (optional), applicable only for equals operator, could be `?` (ignore-case).
'MATCH TYPE' (optional), applicable only for equals operator, could be nothing (exact match), `*` (match anywhere), `^` (match from start), `%` (wildcard), or `~` (PCRE regular expression).
'OPERATOR' is one of `=` (equals), `<`, `>`, `<=`, `=>`, or nothing (exists). Exists operator checks whether a property exists on a window (but for predefined targets, exists means != 0 then).
Supported logical operators are `&&` (and) and `||` (or). `&&` has higher precedence than `||`, left-to-right associativity. Use parentheses to change precedence.
'TYPE' is one of "e" (exact match), "a" (match anywhere), "s" (match from start), "w" (wildcard), and "p" (PCRE regular expressions, if compiled with the support).
'FLAGS' could be a series of flags. Currently the only defined flag is "i" (ignore case).
This secion describes the interface of a custom shader, how it is used by picom, and what parameters are passed by picom to the shader. This does not apply to the legacy backends.
A custom shader is a GLSL fragment shader program, which can be used to override the default way of how a window is rendered. If a custom shader is used, the default picom effects (e.g. dimming, color inversion, etc.) will no longer be automatically applied. It would be the custom shader's responsibility to apply these effects.
The interface between picom and a custom shader is dependent on which backend is being used. The xrender backend doesn't support shader at all. Here we descibe the interface provided by the glx backend.
The shader must define a function, 'vec4 window_shader()', which would be the entry point of the shader. The returned 'vec4' will be used to set 'gl_FragColor'. A function, 'vec4 default_post_processing(vec4 c)', is provided for applying the default picom effects to input color 'c'.
picom could read from a configuration file if libconfig support is compiled in. If *--config* is not used, picom will seek for a configuration file in `$XDG_CONFIG_HOME/picom.conf` (`~/.config/picom.conf`, usually), then `$XDG_CONFIG_HOME/picom/picom.conf`, then `$XDG_CONFIG_DIRS/picom.conf` (often `/etc/xdg/picom.conf`), then `$XDG_CONFIG_DIRS/picom/picom.conf`.
picom uses general libconfig configuration file format. A sample configuration file is available as `picom.sample.conf` in the source tree. Most of commandline switches can be used as options in configuration file as well. For example, *--vsync* option documented above can be set in the configuration file using `vsync = `. Command line options will always overwrite the settings in the configuration file.
'WINDOW_TYPE' is one of the 15 window types defined in EWMH standard: "unknown", "desktop", "dock", "toolbar", "menu", "utility", "splash", "dialog", "normal", "dropdown_menu", "popup_menu", "tooltip", "notification", "combo", and "dnd".
Controls whether shadow is drawn under the parts of the window that you normally won't be able to see. Useful when the window has parts of it transparent, and you want shadows in those areas.
Controls whether shadows that would have been drawn above the window should be clipped. Useful for dock windows that should have no shadow painted on top.
Controls whether this type of windows should cause screen to become redirected again after been unredirected. If you have *--unredir-if-possible* set, and doesn't want certain window to cause unnecessary screen redirection, you can set this to `true`.
'none' to disable blurring; 'gaussian' for gaussian blur; 'box' for box blur; 'kernel' for convolution blur with a custom kernel; 'dual_kawase' for dual-filter kawase blur.
An integer. The size of the blur kernel, required by 'gaussian' and 'box' blur methods. For the 'kernel' method, the size is included in the kernel. Corresponds to the *--blur-size* command line option (default: 3).
A floating point number. The standard deviation for the 'gaussian' blur method. Corresponds to the *--blur-deviation* command line option (default: 0.84089642).
An integer in the range 0-20. The strength of the 'dual_kawase' blur method. Corresponds to the *--blur-strength* command line option. If set to zero, the value requested by *--blur-size* is approximated (default: 5).
A string. The kernel to use for the 'kernel' blur method, specified in the same format as the *--blur-kern* option. Corresponds to the *--blur-kern* command line option.
It's possible to control picom via D-Bus messages, by running picom with *--dbus* and send messages to `com.github.chjj.compton.<DISPLAY>`. `<DISPLAY>` is the display used by picom, with all non-alphanumeric characters transformed to underscores. For `DISPLAY=:0.0` you should use `com.github.chjj.compton._0_0`, for example.
* Same thing as above, plus making inactive windows 80% transparent, making frame 80% transparent, don't fade on window open/close, and fork to background:
