Scripted Effects

The Concept

These are scripts hooking into polychromatic.fx, a high level Python library API to interact with a device’s individual LED addressing (matrix). Like with any custom effect, the backend and device must support individual LED addressing (matrix) as this effect type does not interface with a device’s hardware effects.

You can optionally add your own parameters to fine tune the behaviour of the effect, using integers, strings, colours and multiple choice as inputs.

There are two files in ~/.config/polychromatic/effects/scripted/ :

  • A Python (.py) file containing the code.
  • A JSON (.json) file describing the metadata.

Writing the Script

Scripted effects are written in Python. This documentation assumes familiarity with the basics of the syntax.

Scripts are written inside a play function, meaning the files do not run on their own. Polychromatic loads the script as a module and executes the play() function with the fx object and params populated and validated.

When editing the script via the Controller application, you can test the effect against real hardware or via an on-screen software graphic.

Here’s a starting example:


import polychromatic.fx

def play(fx, params={}):

    # Parameters Example:
    # params["var1"]    # "#00FF00"
    # params["var2"]    # "Fast"

    # Variables
    fx.rows             # 5
    fx.cols             # 20             # Razer BlackWidow Chroma
    fx.backend          # OpenRazer
    fx.form_factor      # keyboard

    # Helper functions
    fx.rgb_to_hex(0, 255, 0)    # Output: #00FF00
    fx.hex_to_rgb("#00FF00")    # Output: [0, 255, 0]

    # Drawing
    fx.matrix[0,0] = [255,0,0]
    fx.matrix[1,0] = [0,255,0]
    fx.matrix[2,0] = [0,0,255]
Variable Returns Purpose Example
params dict User input as specified in the metadata. See Parameters below. {"var1": "#00FF00", "var2": "Fast"}
fx.rows int Number of vertical LEDs 6
fx.cols int Number of horiziontal LEDs 22 str Human name of the device Razer BlackWidow Chroma
fx.backend str Name of backend providing this device openrazer
fx.form_factor str Label for this type of device keyboard

Function Returns Purpose Example Input Example Output
fx.rgb_to_hex() str Input integers: [R,G,B] to get the hex value [0,255,0] "#00FF00"
fx.hex_to_rgb() list Input string: ("#RRGGBB") to get separate R, G, B values "#FF0000" [255,0,0]
fx.matrix[X,Y] = [r,g,b]   Set a colour at the specified position (0-based, 3 RGB integers)    
fx.draw()   Send this frame to the hardware    
fx.clear()   Wipe all LEDs to blank    
fx.brightness()   Input float: percent to change the brightness of all LEDs 50 All LEDs at 50% brightness

The script can be very flexible using the power of Python using import’s and as many functions as desired. The application will detect these and inform the user of dependencies.

At minimum, an effect must have:

  • #!/usr/bin/python3 as the shebang.
  • import polychromatic.fx
  • def play(fx, params=[]):

Additional Metadata

Accompanying the Python file is the JSON file with the common metadata in addition to:

    "required_os": ["any", "linux"],
    "parameters": [],
    "designed_for": ["keyboard"],
    "optimised_for": ["Razer BlackWidow Chroma"]
Key Data Type Purpose
required_os list If applicable, limit effect to run on these platforms. Specify ["linux", "macos", "windows"] or leave blank for any OS.
parameters list See Parameters below.
designed_for list List of device types indicating what the effect is designed for. Leave blank for any device.
optimised_for list List of full device names to indicate where the effect was tested and approved to work on, e.g. "Razer BlackWidow Ultimate 2016".

All fields are required.

Device Types

Polychromatic identifies devices into one of these categories:

  • unrecognised
  • keyboard
  • mouse
  • mousemat
  • keypad
  • headset
  • gpu
  • accessory

For example, the logic in scripted effects could behave differently between devices by detecting like this:

if fx.form_factor == "keyboard":
    # code for keyboard

elif fx.form_factor in ["mouse", "keypad"]:
    # code for mouse or keypad

    # everything else


Polychromatic will expose these in the interface for the user to choose, and your effect will be able to reference them in params["<var>"].

As expected with Python, if your script incorrectly references a non-existant variable, the effect will abruptly halt with a KeyError exception.

"parameters": [
        "var": "cpu_colour",
        "label": "CPU Colour",
        "type": "colour",
        "value": null,
        "default": "#00FF00"
        "var": "speed",
        "label": "Speed",
        "type": "list",
        "options": ["Fast", "Medium", "Slow"],
        "value": null,
        "default": "Slow"
Key Data Type Purpose
var str Variable name, no spaces, case sensitive
label str Human readable name (English)
label[fr] str Human readable name (other language, e.g. fr)
type str One of: colour, list, int or str
options dict type: "list" only – Options to show in the interface (English). See below.
options[fr] dict type: "list" only – Options to show in other languages (e.g. fr)
value str Current value as set by the user. Starts as None (null)
default str When a value wasn’t specified, use this value

When the type is list:

  • value is validated against the list of options.
  • An invalid value will fallback to the value of default.
  • The options key should be populated with label/value combinations, like so:
      "options": {
          "Item A": 1,
          "Item B": 2,
          "Item C": 3
  • Localisation is supported in the interface:
      "options[fr]": {
          "Objet A": 1,
          "Objet B": 2,
          "Objet C": 3
  • When localised options are used, the application will validate to make sure they all offer the same values.