Custom Properties

Formation studio allows you to specify custom properties for your Custom Widgets. Owing to the adaptive nature of how the studio handles properties adding custom properties is relatively easy. The studio relies on proper implementation of the configure, keys, cget, __getitem__ and __setitem__ methods of a widget for custom properties to be correctly detected. Luckily, formation provides utilities to achieve this through the CustomPropertyMixin Let us add a custom properties button_color and button_bg to our Dpad widget. We will modify our class to use the CustomPropertyMixin as shown below

from tkinter import Frame, Button
from formation.utils import CustomPropertyMixin

class DPad(CustomPropertyMixin, Frame):

    prop_info = {
        "button_color": {
            "name": "button_color",
            "default": None,
            "setter": "set_btn_fg",
            "getter": "_btn_fg"
        "button_bg": {
            "name": "button_bg",
            "default": None,
            "setter": "set_btn_bg",
            "getter": "_btn_bg"

    def __init__(self, master, **kw):
        super(DPad, self).__init__(master, **kw)
        self.left = Button(self, text="L", padx=8, pady=5)
        self.right = Button(self, text="R", padx=8, pady=5)
        self.up = Button(self, text="U", padx=8, pady=5)
        self.down = Button(self, text="D", padx=8, pady=5)

        self.up.grid(row=0, column=1)
        self.left.grid(row=1, column=0)
        self.right.grid(row=1, column=2)
        self.down.grid(row=2, column=1)

        self._btns = [self.left, self.right, self.up, self.down]

        self._btn_bg = self.left["bg"]
        self._btn_fg = self.left["fg"]

    def set_btn_bg(self, val):
        for i in self._btns:
            i["bg"] = val
        self._btn_bg = val

    def set_btn_fg(self, val):
        for i in self._btns:
            i["fg"] = val
        self._btn_fg = val


The CustomPropertyMixin is not necessary if configure, keys and the other methods are already implemented to accommodate you custom properties. It is however advisable to use the mixin as it has been thoroughly tested and is less prone to issues.

Our widget is ready for use. We still need to inform the studio on how our properties should be handled and what type of values they contain. The studio supports the following property types:

  • choice : Allows selection from a set of values using a dropdown widget. Options are specified as a tuple using the options key.

  • boolean : Selection of true or false using a checkbutton

  • relief : Allows selection from the available relief types in tkinter

  • cursor : Allows selection from available cursor types in tkinter

  • bitmap : Allows selection from the built-in bitmaps

  • color : Provides a colorpicker dialog to select colors

  • text : Allows entry of arbitrary text

  • textarea : Similar to text but allows entry of longer texts.

  • number : Entry of integers

  • float : Entry of floating point numbers

  • duration : Allow entry of durations. You can specify the units options which can be one of (‘ns’, ‘ms’, ‘sec’, ‘min’, ‘hrs’).

  • font : Selection from available system fonts. It also includes a font picker that can pick fonts from anywhere within the studio.

  • dimension : Entry of dimension. Currently only supports pixels

  • anchor : Allows easy setting of anchor and sticky values by providing realtime preview of anchor/sticky behaviour on a dummy widget. Setting the multiple option allows the application of multiple anchors simultaneously

  • image : Allows user to pick an image from their local machine

  • variable : Allows user to select from variables created by the Variable pane

  • stringvariable: A variation of the variable type that only allows selection of tk.StringVar


It is currently not possible to implement your own types but we hope to make allow custom types in future.

To specify the types our custom properties, we will modify the meta class as shown below:

class DPadMeta(DPad, metaclass=WidgetMeta):
    display_name = 'D Pad'
    impl = DPad
    icon = "gaming"
    is_container = False
    initial_dimensions = 90, 100

        "button_color": {
            "display_name": "button color",
            "type": "color",
            # you can specify additional options supported by type here
            "name": "button_color"
        "button_bg": {
            "display_name": "button bg",
            "type": "color",
            "name": "button_bg"

DEF_OVERRIDES is a special attribute checked at runtime by the studio to make decisions on what properties to display and how. You can also override behaviour of default properties by specifying alternative definitions here.


The key and the name should always match to avoid issues.

Assuming your widget is properly setup as explained in Custom Widgets, if you open the studio and use your custom widget, the custom properties will appear in the attributes section on the stylepane as shown below