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@BigRoy
Created August 1, 2019 10:04
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Simple example of running a Qt interface in Blender 2.8 without blocking Blender.
import bpy
from PyQt5 import QtWidgets
class QtModalOperator(bpy.types.Operator):
"""A base class for Operators that run a Qt interface."""
def modal(self, context, event):
if self._app:
self._app.processEvents()
return {'PASS_THROUGH'}
return {"FINISHED"}
def execute(self, context):
"""Execute the Operator.
The child class must implement execute() and call super to trigger this
class' execute() at the beginning. The execute() method must finally
return {'RUNNING_MODAL"}
Note that the Qt code should *not* call QApplication.exec_() as it
seems that magically the Qt application already processes straight
away in Blender. Maybe due to:
https://stackoverflow.com/questions/28060218/where-is-pyqt-event
-loop-running
"""
self._app = QtWidgets.QApplication.instance()
if not self._app:
self._app = QtWidgets.QApplication(["blender"])
class QtTestOperator(QtModalOperator):
"""Launch Avalon Creator.."""
bl_idname = "object.qt_test"
bl_label = "Test Qt UI.."
def execute(self, context):
# Initialize Qt operator execution
super(QtTestOperator, self).execute(context)
global widget
widget = QtWidgets.QPushButton("Hello")
widget.show()
return {'RUNNING_MODAL'}
bpy.utils.register_class(QtTestOperator)
bpy.ops.object.qt_test()
@BigRoy
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BigRoy commented Aug 1, 2019

Another test snippet by Jasper van Nieuwenhuizen: https://gitlab.com/snippets/1881226
See discussion here.

@jasperges
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A note about this: the modal operator only finishes when self._app doesn't exist anymore. That will most likely only be the case when Blender quits. So it would be better to check widget.isVisible() and return {'FINISHED'} when it's not. Else the modal operator keeps running which at least prevents auto saves (and probably more unwanted behavior).

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