Base widget class for using Maya's MayaQWidgetDockableMixin class that handles showing and restoring of the UI.

maya_mixin_widget.txt

from maya.app.general.mayaMixin import MayaQWidgetDockableMixin
import maya.cmds as cmds
import PySide2.QtWidgets as qtwidgets
import maya.OpenMayaUI as omui


class DockableMixinWidget(MayaQWidgetDockableMixin, qtwidgets.QWidget):

	_instance = None
	_show_kwargs = {}  # see kwargs for setDockableParameters in mayaMixin.py 

	def __init__(self):
		super(DockableMixinWidget, self).__init__()

		self.setObjectName(f'dockable_mixin_{self.__class__.__name__}')

	@classmethod
	def restore(cls):
		'''Logic for restoring widget to Maya's workspace.'''

		workspace_control = omui.MQtUtil.getCurrentParent()
		cls._instance = cls()
		pointer = omui.MQtUtil.findControl(cls._instance.objectName())
		omui.MQtUtil.addWidgetToMayaLayout(int(pointer), int(workspace_control))

	@classmethod
	def open(cls, delete_ui=False):
		'''Show the UI and store UI Script for restoration.

		Args:
			delete_ui(bool): Remove existing UI and instantiate a fresh version. Use to test changes to the UI.

		Returns:
			DockableMixinWidget: instance of object
		'''

		if delete_ui and cmds.workspaceControl(f'dockable_mixin_{cls.__name__}WorkspaceControl', exists=True):
			cmds.deleteUI(f'dockable_mixin_{cls.__name__}WorkspaceControl')
			cls._instance = None

		if cls._instance is None:
			cls._instance = cls()

		cls._instance.show(
			dockable=True,
			uiScript=f"import {cls.__module__}\n{cls.__module__}.{cls.__name__}.restore()",
			**cls._show_kwargs)

		return cls._instance


class ExampleWidget(DockableMixinWidget):

	_show_kwargs = {'widthSizingProperty':'preferred', 'minWidth':300}

	def __init__(self):
		super(ExampleWidget, self).__init__()

		self.setWindowTitle('Example Dockable Widget')
		self.setLayout(qtwidgets.QVBoxLayout())

		label = qtwidgets.QLabel('Example Label')
		self.layout().addWidget(label)
		button = qtwidgets.QPushButton('Example Button')
		self.layout().addWidget(button)


# To show your subclass UI call open
# ExampleWidget.open()