Modal Operators: Click Object Event

Question

I'm currently working on a python tool using a modal operator. Now I know to finish the operation I can use:

if event.type == 'LEFTMOUSE':
    return {'FINISHED'}

However it seems not to count as a 'LEFTMOUSE' when I click (select) an object! I also tried 'SELECTMOUSE' which doesn't do anything.

What I would like to do is store the clicked object, and then automatically finish the modal operator.

Any ideas? Thanks in advance!

Answer 1

I have a solution and it's actually very simple:

class OBJECT_OT_do_stuff(bpy.types.Operator):
    bl_idname = "object.do_stuff"
    bl_label = "Do Stuff"

    origSel: None

    @classmethod
    def poll(cls, context):
        return context.active_object is not None

    def modal(self, context, event):
        # Update selection
        curSel = context.selected_objects[-1]

        # On selecting new object
        if curSel is not self.origSel:
            print("selection was changed")
            return {'FINISHED'}

        elif event.type in {'RIGHTMOUSE', 'ESC'}:
            print("cancelled operation")
            return {'CANCELLED'}

        else:
            return {'PASS_THROUGH'}

        return {'RUNNING_MODAL'}

    def invoke(self, context, event):
        self.origSel = context.object
        # Execute Modal Operation
        context.window_manager.modal_handler_add(self)
        return {'RUNNING_MODAL'}

I assigned an attribute that in the invoke function gets filled with the active object. Then the modal function keeps comparing the current selection to the previous one!

An important thing to note is that in order for that to work you need to call the function with the invoke argument :bpy.ops.object.do_stuff('INVOKE_DEFAULT')

Answer 2

Why type.event ?

You should get your event.type, and you may want to compare the event.value as well:

def modal(self, context, event):
    if event.type in {"LEFTMOUSE"} and event.value == "RELEASE":
        return {'FINISHED'}
    return {'PASS_THROUGH'}

Also, it might be possible that an event been stop propagate in most of the event handling system. You might need to check the context carefully to see what is the main problem.

Answer 3

Great script. I arranged it so that it responds even when not selected.

import bpy

class OBJECT_OT_do_stuff(bpy.types.Operator):
    bl_idname = "object.do_stuff"
    bl_label = "Do Stuff"

    origSel: None

    @classmethod
    def poll(cls, context):
        return context.active_object is not None

    def modal(self, context, event):
        # Update selection
        selobj=context.selected_objects
        
        if selobj != []:
            curSel = selobj[-1]
        else: 
            return {'PASS_THROUGH'}
    
        # On selecting new object
        if curSel is not self.origSel:
            self.report({'INFO'}, "selection was '{}' changed".format(curSel.name))
            return {'FINISHED'}

        elif event.type in {'RIGHTMOUSE', 'ESC'}:
            self.report({'INFO'}, "cancelled operation '{}'".format(curSel.name))
            return {'CANCELLED'}

        else:
            return {'PASS_THROUGH'}

        return {'RUNNING_MODAL'}

    def invoke(self, context, event):
        self.origSel = context.object
        # Execute Modal Operation
        context.window_manager.modal_handler_add(self)
        return {'RUNNING_MODAL'}
    
classes = (
    OBJECT_OT_do_stuff,
    
    )
def register():
    for cls in classes:
        bpy.utils.register_class(cls)


def unregister():
    for cls in classes:
        bpy.utils.unregister_class(cls)


if __name__ == "__main__":
    register()