tasks_queue.py

# ##### BEGIN GPL LICENSE BLOCK #####
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU General Public License
#  as published by the Free Software Foundation; either version 2
#  of the License, or (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program; if not, write to the Free Software Foundation,
#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
#
# ##### END GPL LICENSE BLOCK #####

if "bpy" in locals():
    from importlib import reload

    utils = reload(utils)
else:
    from blenderkit import utils

import bpy
from bpy.app.handlers import persistent

import queue

@persistent
def scene_load(context):
    user_preferences = bpy.context.preferences.addons['blenderkit'].preferences
    if user_preferences.use_timers:
        if not (bpy.app.timers.is_registered(queue_worker)):
            bpy.app.timers.register(queue_worker)


def get_queue():
    # we pick just a random one of blender types, to try to get a persistent queue
    t = bpy.types.Scene

    if not hasattr(t, 'task_queue'):
        t.task_queue = queue.Queue()
    return t.task_queue

class task_object:
    def __init__(self, command = '', arguments = (), wait = 0, only_last = False, fake_context = False, fake_context_area = 'VIEW_3D'):
        self.command = command
        self.arguments = arguments
        self.wait = wait
        self.only_last = only_last
        self.fake_context = fake_context
        self.fake_context_area = fake_context_area

def add_task(task, wait = 0, only_last = False, fake_context = False, fake_context_area = 'VIEW_3D'):
    q = get_queue()
    taskob = task_object(task[0],task[1], wait = wait, only_last = only_last, fake_context = fake_context, fake_context_area = fake_context_area)
    q.put(taskob)


def queue_worker():
    time_step = 2.0
    q = get_queue()

    back_to_queue = [] #delayed events
    stashed = {}
    # first round we get all tasks that are supposed to be stashed and run only once (only_last option)
    # stashing finds tasks with the property only_last and same command and executes only the last one.
    while not q.empty():
        task = q.get()
        if task.only_last:
            stashed[task.command] = task
        else:
            back_to_queue.append(task)
    #return tasks to que except for stashed
    for task in back_to_queue:
        q.put(task)
    #return stashed tasks to queue
    for k in stashed.keys():
        q.put(stashed[k])
    #second round, execute or put back waiting tasks.
    back_to_queue = []
    while not q.empty():
        # print('window manager', bpy.context.window_manager)
        task = q.get()

        if task.wait>0:
            task.wait-=time_step
            back_to_queue.append(task)
        else:
            utils.p('as a task:   ')
            utils.p(task.command, task.arguments)
            try:
                if task.fake_context:
                    fc = utils.get_fake_context(bpy.context, area_type = task.fake_context_area)
                    task.command(fc,*task.arguments)
                else:
                    task.command(*task.arguments)
            except Exception as e:
                utils.p('task failed:')
                print(e)
    for task in back_to_queue:
        q.put(task)
    return 2.0


def register():
    bpy.app.handlers.load_post.append(scene_load)


def unregister():
    bpy.app.handlers.load_post.remove(scene_load)