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891ac4e5bd
Flutter implements the UI isolates message via posting to a UI task queue. That task queue has a primary and a secondary queue. The * primary is used for running tasks resulated to framework (e.g. draw frame) * secondary is used to run Dart event loop messages (e.g. received data on a socket) The Dart semantics requires running microtasks before processing the next event loop message. The way flutter implements by attaching an observer to the secondary queue. Every time a task from the queue is run, all observers are run and one of them is going to run pending microtasks. In some situations the engine pauses the dart event loop. The terminology used in the code is "microtask" when in reality what it means is "event loop". => This PR changes this terminology to reflect what actually happens.
104 lines
2.5 KiB
C++
104 lines
2.5 KiB
C++
// Copyright 2013 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#define FML_USED_ON_EMBEDDER
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#include "flutter/fml/task_source.h"
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namespace fml {
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TaskSource::TaskSource(TaskQueueId task_queue_id)
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: task_queue_id_(task_queue_id) {}
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TaskSource::~TaskSource() {
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ShutDown();
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}
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void TaskSource::ShutDown() {
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primary_task_queue_ = {};
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secondary_task_queue_ = {};
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}
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void TaskSource::RegisterTask(const DelayedTask& task) {
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switch (task.GetTaskSourceGrade()) {
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case TaskSourceGrade::kUserInteraction:
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primary_task_queue_.push(task);
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break;
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case TaskSourceGrade::kUnspecified:
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primary_task_queue_.push(task);
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break;
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case TaskSourceGrade::kDartEventLoop:
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secondary_task_queue_.push(task);
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break;
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}
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}
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void TaskSource::PopTask(TaskSourceGrade grade) {
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switch (grade) {
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case TaskSourceGrade::kUserInteraction:
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primary_task_queue_.pop();
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break;
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case TaskSourceGrade::kUnspecified:
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primary_task_queue_.pop();
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break;
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case TaskSourceGrade::kDartEventLoop:
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secondary_task_queue_.pop();
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break;
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}
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}
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size_t TaskSource::GetNumPendingTasks() const {
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size_t size = primary_task_queue_.size();
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if (secondary_pause_requests_ == 0) {
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size += secondary_task_queue_.size();
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}
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return size;
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}
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bool TaskSource::IsEmpty() const {
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return GetNumPendingTasks() == 0;
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}
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TaskSource::TopTask TaskSource::Top() const {
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FML_CHECK(!IsEmpty());
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if (secondary_pause_requests_ > 0 || secondary_task_queue_.empty()) {
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const auto& primary_top = primary_task_queue_.top();
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return {
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.task_queue_id = task_queue_id_,
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.task = primary_top,
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};
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} else if (primary_task_queue_.empty()) {
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const auto& secondary_top = secondary_task_queue_.top();
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return {
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.task_queue_id = task_queue_id_,
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.task = secondary_top,
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};
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} else {
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const auto& primary_top = primary_task_queue_.top();
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const auto& secondary_top = secondary_task_queue_.top();
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if (primary_top > secondary_top) {
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return {
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.task_queue_id = task_queue_id_,
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.task = secondary_top,
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};
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} else {
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return {
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.task_queue_id = task_queue_id_,
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.task = primary_top,
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};
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}
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}
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}
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void TaskSource::PauseSecondary() {
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secondary_pause_requests_++;
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}
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void TaskSource::ResumeSecondary() {
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secondary_pause_requests_--;
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FML_DCHECK(secondary_pause_requests_ >= 0);
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}
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} // namespace fml
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