Remove pthread dependency

src/ftxui/component/receiver.cppm

@@ -12,9 +12,15 @@ export module ftxui.component.receiver;
  * @brief The FTXUI ftxui:: namespace
  */
 export namespace ftxui {
+    // Deprecated:
     using ftxui::SenderImpl;
+    // Deprecated:
     using ftxui::ReceiverImpl;
+    // Deprecated:
     using ftxui::Sender;
+    // Deprecated:
     using ftxui::Receiver;
+    // Deprecated:
     using ftxui::MakeReceiver;
+    // Deprecated:
 }

src/ftxui/component/receiver_test.cpp

@@ -1,81 +0,0 @@
-// Copyright 2020 Arthur Sonzogni. All rights reserved.
-// Use of this source code is governed by the MIT license that can be found in
-// the LICENSE file.
-#include <thread>   // for thread
-#include <utility>  // for move
-
-#include "ftxui/component/receiver.hpp"
-#include "gtest/gtest.h"  // for AssertionResult, Message, Test, TestPartResult, EXPECT_EQ, EXPECT_TRUE, EXPECT_FALSE, TEST
-
-// NOLINTBEGIN
-namespace ftxui {
-
-TEST(Receiver, Basic) {
-  auto receiver = MakeReceiver<char>();
-  auto sender = receiver->MakeSender();
-
-  sender->Send('a');
-  sender->Send('b');
-  sender->Send('c');
-  sender.reset();
-
-  char a, b, c, d;
-  EXPECT_TRUE(receiver->Receive(&a));
-  EXPECT_TRUE(receiver->Receive(&b));
-  EXPECT_TRUE(receiver->Receive(&c));
-  EXPECT_FALSE(receiver->Receive(&d));
-
-  EXPECT_EQ(a, 'a');
-  EXPECT_EQ(b, 'b');
-  EXPECT_EQ(c, 'c');
-}
-
-TEST(Receiver, BasicWithThread) {
-  auto r1 = MakeReceiver<char>();
-  auto r2 = MakeReceiver<char>();
-  auto r3 = MakeReceiver<char>();
-
-  auto s1 = r1->MakeSender();
-  auto s2 = r2->MakeSender();
-  auto s3 = r3->MakeSender();
-
-  auto s1_bis = r1->MakeSender();
-
-  auto stream = [](Receiver<char> receiver, Sender<char> sender) {
-    char c;
-    while (receiver->Receive(&c))
-      sender->Send(c);
-  };
-
-  // Convert data from a different thread.
-  auto t12 = std::thread(stream, std::move(r1), std::move(s2));
-  auto t23 = std::thread(stream, std::move(r2), std::move(s3));
-
-  // Send some data.
-  s1->Send('1');
-  s1_bis->Send('2');
-  s1->Send('3');
-  s1_bis->Send('4');
-
-  // Close the stream.
-  s1.reset();
-  s1_bis.reset();
-
-  char c;
-  EXPECT_TRUE(r3->Receive(&c));
-  EXPECT_EQ(c, '1');
-  EXPECT_TRUE(r3->Receive(&c));
-  EXPECT_EQ(c, '2');
-  EXPECT_TRUE(r3->Receive(&c));
-  EXPECT_EQ(c, '3');
-  EXPECT_TRUE(r3->Receive(&c));
-  EXPECT_EQ(c, '4');
-  EXPECT_FALSE(r3->Receive(&c));
-
-  // Thread will end at the end of the stream.
-  t12.join();
-  t23.join();
-}
-
-}  // namespace ftxui
-// NOLINTEND

src/ftxui/component/screen_interactive.cpp

@@ -17,24 +17,22 @@
 #include <memory>
 #include <stack>  // for stack
 #include <string>
-#include <thread>       // for thread, sleep_for
-#include <tuple>        // for _Swallow_assign, ignore
-#include <type_traits>  // for decay_t
-#include <utility>      // for move, swap
-#include <variant>      // for visit, variant
-#include <vector>       // for vector
+#include <thread>   // for thread, sleep_for
+#include <tuple>    // for _Swallow_assign, ignore
+#include <utility>  // for move, swap
+#include <variant>  // for visit, variant
+#include <vector>   // for vector
 #include "ftxui/component/animation.hpp"  // for TimePoint, Clock, Duration, Params, RequestAnimationFrame
 #include "ftxui/component/captured_mouse.hpp"  // for CapturedMouse, CapturedMouseInterface
 #include "ftxui/component/component_base.hpp"  // for ComponentBase
 #include "ftxui/component/event.hpp"           // for Event
 #include "ftxui/component/loop.hpp"            // for Loop
-#include "ftxui/component/receiver.hpp"  // for ReceiverImpl, Sender, MakeReceiver, SenderImpl, Receiver
+#include "ftxui/component/task_runner.hpp"
 #include "ftxui/component/terminal_input_parser.hpp"  // for TerminalInputParser
 #include "ftxui/dom/node.hpp"                         // for Node, Render
-#include "ftxui/dom/requirement.hpp"                  // for Requirement
-#include "ftxui/screen/pixel.hpp"                     // for Pixel
 #include "ftxui/screen/terminal.hpp"                  // for Dimensions, Size
 #include "ftxui/screen/util.hpp"                      // for util::clamp
+#include "ftxui/util/autoreset.hpp"                   // for AutoReset
 
 #if defined(_WIN32)
 #define DEFINE_CONSOLEV2_PROPERTIES
@@ -47,9 +45,11 @@
 #error Must be compiled in UNICODE mode
 #endif
 #else
+#include <fcntl.h>
 #include <sys/select.h>  // for select, FD_ISSET, FD_SET, FD_ZERO, fd_set, timeval
 #include <termios.h>  // for tcsetattr, termios, tcgetattr, TCSANOW, cc_t, ECHO, ICANON, VMIN, VTIME
 #include <unistd.h>  // for STDIN_FILENO, read
+#include <cerrno>
 #endif
 
 // Quick exit is missing in standard CLang headers
@@ -59,6 +59,20 @@
 
 namespace ftxui {
 
+struct ScreenInteractive::Internal {
+  // Convert char to Event.
+  TerminalInputParser terminal_input_parser;
+
+  task::TaskRunner task_runner;
+
+  // The last time a character was received.
+  std::chrono::time_point<std::chrono::steady_clock> last_char_time =
+      std::chrono::steady_clock::now();
+
+  explicit Internal(std::function<void(Event)> out)
+      : terminal_input_parser(std::move(out)) {}
+};
+
 namespace animation {
 void RequestAnimationFrame() {
   auto* screen = ScreenInteractive::Active();
@@ -82,75 +96,9 @@ constexpr int timeout_milliseconds = 20;
     timeout_milliseconds * 1000;
 #if defined(_WIN32)
 
-void EventListener(std::atomic<bool>* quit, Sender<Task> out) {
-  auto console = GetStdHandle(STD_INPUT_HANDLE);
-  auto parser =
-      TerminalInputParser([&](Event event) { out->Send(std::move(event)); });
-  while (!*quit) {
-    // Throttle ReadConsoleInput by waiting 250ms, this wait function will
-    // return if there is input in the console.
-    auto wait_result = WaitForSingleObject(console, timeout_milliseconds);
-    if (wait_result == WAIT_TIMEOUT) {
-      parser.Timeout(timeout_milliseconds);
-      continue;
-    }
-
-    DWORD number_of_events = 0;
-    if (!GetNumberOfConsoleInputEvents(console, &number_of_events))
-      continue;
-    if (number_of_events <= 0)
-      continue;
-
-    std::vector<INPUT_RECORD> records{number_of_events};
-    DWORD number_of_events_read = 0;
-    ReadConsoleInput(console, records.data(), (DWORD)records.size(),
-                     &number_of_events_read);
-    records.resize(number_of_events_read);
-
-    for (const auto& r : records) {
-      switch (r.EventType) {
-        case KEY_EVENT: {
-          auto key_event = r.Event.KeyEvent;
-          // ignore UP key events
-          if (key_event.bKeyDown == FALSE)
-            continue;
-          std::wstring wstring;
-          wstring += key_event.uChar.UnicodeChar;
-          for (auto it : to_string(wstring)) {
-            parser.Add(it);
-          }
-        } break;
-        case WINDOW_BUFFER_SIZE_EVENT:
-          out->Send(Event::Special({0}));
-          break;
-        case MENU_EVENT:
-        case FOCUS_EVENT:
-        case MOUSE_EVENT:
-          // TODO(mauve): Implement later.
-          break;
-      }
-    }
-  }
-}
-
 #elif defined(__EMSCRIPTEN__)
 #include <emscripten.h>
 
-// Read char from the terminal.
-void EventListener(std::atomic<bool>* quit, Sender<Task> out) {
-  auto parser =
-      TerminalInputParser([&](Event event) { out->Send(std::move(event)); });
-
-  char c;
-  while (!*quit) {
-    while (read(STDIN_FILENO, &c, 1), c)
-      parser.Add(c);
-
-    emscripten_sleep(1);
-    parser.Timeout(1);
-  }
-}
-
 extern "C" {
 EMSCRIPTEN_KEEPALIVE
 void ftxui_on_resize(int columns, int rows) {
@@ -164,8 +112,8 @@ void ftxui_on_resize(int columns, int rows) {
 
 #else  // POSIX (Linux & Mac)
 
-int CheckStdinReady(int usec_timeout) {
-  timeval tv = {0, usec_timeout};  // NOLINT
+int CheckStdinReady() {
+  timeval tv = {0, 0};  // NOLINT
   fd_set fds;
   FD_ZERO(&fds);                                          // NOLINT
   FD_SET(STDIN_FILENO, &fds);                             // NOLINT
@@ -173,25 +121,6 @@ int CheckStdinReady(int usec_timeout) {
   return FD_ISSET(STDIN_FILENO, &fds);                    // NOLINT
 }
 
-// Read char from the terminal.
-void EventListener(std::atomic<bool>* quit, Sender<Task> out) {
-  auto parser =
-      TerminalInputParser([&](Event event) { out->Send(std::move(event)); });
-
-  while (!*quit) {
-    if (!CheckStdinReady(timeout_microseconds)) {
-      parser.Timeout(timeout_milliseconds);
-      continue;
-    }
-
-    const size_t buffer_size = 100;
-    std::array<char, buffer_size> buffer;                        // NOLINT;
-    size_t l = read(fileno(stdin), buffer.data(), buffer_size);  // NOLINT
-    for (size_t i = 0; i < l; ++i) {
-      parser.Add(buffer[i]);  // NOLINT
-    }
-  }
-}
 #endif
 
 std::stack<Closure> on_exit_functions;  // NOLINT
@@ -338,15 +267,6 @@ class CapturedMouseImpl : public CapturedMouseInterface {
   std::function<void(void)> callback_;
 };
 
-void AnimationListener(std::atomic<bool>* quit, Sender<Task> out) {
-  // Animation at around 60fps.
-  const auto time_delta = std::chrono::milliseconds(15);
-  while (!*quit) {
-    out->Send(AnimationTask());
-    std::this_thread::sleep_for(time_delta);
-  }
-}
-
 }  // namespace
 
 ScreenInteractive::ScreenInteractive(Dimension dimension,
@@ -356,7 +276,8 @@ ScreenInteractive::ScreenInteractive(Dimension dimension,
     : Screen(dimx, dimy),
       dimension_(dimension),
       use_alternative_screen_(use_alternative_screen) {
-  task_receiver_ = MakeReceiver<Task>();
+  internal_ = std::make_unique<Internal>(
+      [&](Event event) { PostEvent(std::move(event)); });
 }
 
 // static
@@ -417,6 +338,8 @@ ScreenInteractive ScreenInteractive::TerminalOutput() {
   };
 }
 
+ScreenInteractive::~ScreenInteractive() = default;
+
 /// Create a ScreenInteractive whose width and height match the component being
 /// drawn.
 // static
@@ -452,13 +375,9 @@ void ScreenInteractive::TrackMouse(bool enable) {
 /// @brief Add a task to the main loop.
 /// It will be executed later, after every other scheduled tasks.
 void ScreenInteractive::Post(Task task) {
-  // Task/Events sent toward inactive screen or screen waiting to become
-  // inactive are dropped.
-  if (!task_sender_) {
-    return;
-  }
-
-  task_sender_->Send(std::move(task));
+  internal_->task_runner.PostTask([this, task = std::move(task)]() mutable {
+    HandleTask(component_, task);
+  });
 }
 
 /// @brief Add an event to the main loop.
@@ -502,7 +421,7 @@ void ScreenInteractive::Loop(Component component) {  // NOLINT
 
 /// @brief Return whether the main loop has been quit.
 bool ScreenInteractive::HasQuitted() {
-  return task_receiver_->HasQuitted();
+  return quit_;
 }
 
 // private
@@ -659,7 +578,15 @@ void ScreenInteractive::Install() {
 
   SetConsoleMode(stdin_handle, in_mode);
   SetConsoleMode(stdout_handle, out_mode);
-#else
+#else  // POSIX (Linux & Mac)
+  // #if defined(__EMSCRIPTEN__)
+  //// Reading stdin isn't blocking.
+  // int flags = fcntl(0, F_GETFL, 0);
+  // fcntl(0, F_SETFL, flags | O_NONBLOCK);
+
+  //// Restore the terminal configuration on exit.
+  // on_exit_functions.emplace([flags] { fcntl(0, F_SETFL, flags); });
+  // #endif
   for (const int signal : {SIGWINCH, SIGTSTP}) {
     InstallSignalHandler(signal);
   }
@@ -732,40 +659,57 @@ void ScreenInteractive::Install() {
   Flush();
 
   quit_ = false;
-  task_sender_ = task_receiver_->MakeSender();
-  event_listener_ =
-      std::thread(&EventListener, &quit_, task_receiver_->MakeSender());
-  animation_listener_ =
-      std::thread(&AnimationListener, &quit_, task_receiver_->MakeSender());
+
+  PostAnimationTask();
 }
 
 // private
 void ScreenInteractive::Uninstall() {
   ExitNow();
-  event_listener_.join();
-  animation_listener_.join();
   OnExit();
 }
 
 // private
 // NOLINTNEXTLINE
 void ScreenInteractive::RunOnceBlocking(Component component) {
-  ExecuteSignalHandlers();
-  Task task;
-  if (task_receiver_->Receive(&task)) {
-    HandleTask(component, task);
+  // Set FPS to 60 at most.
+  const auto time_per_frame = std::chrono::microseconds(16666);  // 1s / 60fps
+
+  auto time = std::chrono::steady_clock::now();
+  size_t executed_task = internal_->task_runner.ExecutedTasks();
+
+  // Wait for at least one task to execute.
+  while (executed_task == internal_->task_runner.ExecutedTasks() &&
+         !HasQuitted()) {
+    RunOnce(component);
+
+    const auto now = std::chrono::steady_clock::now();
+    const auto delta = now - time;
+    time = now;
+
+    if (delta < time_per_frame) {
+      const auto sleep_duration = time_per_frame - delta;
+      std::this_thread::sleep_for(sleep_duration);
+    }
   }
-  RunOnce(component);
 }
 
 // private
 void ScreenInteractive::RunOnce(Component component) {
-  Task task;
-  while (task_receiver_->ReceiveNonBlocking(&task)) {
-    HandleTask(component, task);
-    ExecuteSignalHandlers();
+  AutoReset set_component(&component_, component);
+  ExecuteSignalHandlers();
+  FetchTerminalEvents();
+
+  // Execute the pending tasks from the queue.
+  const size_t executed_task = internal_->task_runner.ExecutedTasks();
+  internal_->task_runner.RunUntilIdle();
+  // If no executed task, we can return early without redrawing the screen.
+  if (executed_task == internal_->task_runner.ExecutedTasks()) {
+    return;
   }
-  Draw(std::move(component));
+
+  ExecuteSignalHandlers();
+  Draw(component);
 
   if (selection_data_previous_ != selection_data_) {
     selection_data_previous_ = selection_data_;
@@ -786,6 +730,7 @@ void ScreenInteractive::HandleTask(Component component, Task& task) {
         // clang-format off
     // Handle Event.
     if constexpr (std::is_same_v<T, Event>) {
+
       if (arg.is_cursor_position()) {
         cursor_x_ = arg.cursor_x();
         cursor_y_ = arg.cursor_y();
@@ -1037,7 +982,6 @@ void ScreenInteractive::Exit() {
 // private:
 void ScreenInteractive::ExitNow() {
   quit_ = true;
-  task_sender_.reset();
 }
 
 // private:
@@ -1070,6 +1014,117 @@ void ScreenInteractive::Signal(int signal) {
 #endif
 }
 
+void ScreenInteractive::FetchTerminalEvents() {
+#if defined(_WIN32)
+  auto get_input_records = [&]() -> std::vector<INPUT_RECORD> {
+    // Check if there is input in the console.
+    auto console = GetStdHandle(STD_INPUT_HANDLE);
+    DWORD number_of_events = 0;
+    if (!GetNumberOfConsoleInputEvents(console, &number_of_events)) {
+      return std::vector<INPUT_RECORD>();
+    }
+    if (number_of_events <= 0) {
+      // No input, return.
+      return std::vector<INPUT_RECORD>();
+    }
+    // Read the input events.
+    std::vector<INPUT_RECORD> records(number_of_events);
+    DWORD number_of_events_read = 0;
+    if (!ReadConsoleInput(console, records.data(), (DWORD)records.size(),
+                          &number_of_events_read)) {
+      return std::vector<INPUT_RECORD>();
+    }
+    records.resize(number_of_events_read);
+    return records;
+  };
+
+  auto records = get_input_records();
+  if (records.size() == 0) {
+    const auto timeout =
+        std::chrono::steady_clock::now() - internal_->last_char_time;
+    const size_t timeout_microseconds =
+        std::chrono::duration_cast<std::chrono::microseconds>(timeout).count();
+    internal_->terminal_input_parser.Timeout(timeout_microseconds);
+    return;
+  }
+  internal_->last_char_time = std::chrono::steady_clock::now();
+
+  // Convert the input events to FTXUI events.
+  // For each event, we call the terminal input parser to convert it to
+  // Event.
+  for (const auto& r : records) {
+    switch (r.EventType) {
+      case KEY_EVENT: {
+        auto key_event = r.Event.KeyEvent;
+        // ignore UP key events
+        if (key_event.bKeyDown == FALSE)
+          continue;
+        std::wstring wstring;
+        wstring += key_event.uChar.UnicodeChar;
+        for (auto it : to_string(wstring)) {
+          internal_->terminal_input_parser.Add(it);
+        }
+      } break;
+      case WINDOW_BUFFER_SIZE_EVENT:
+        Post(Event::Special({0}));
+        break;
+      case MENU_EVENT:
+      case FOCUS_EVENT:
+      case MOUSE_EVENT:
+        // TODO(mauve): Implement later.
+        break;
+    }
+  }
+#elif defined(__EMSCRIPTEN__)
+  // Read chars from the terminal.
+  // We configured it to be non blocking.
+  std::array<char, 128> out{};
+  size_t l = read(STDIN_FILENO, out.data(), out.size());
+  if (l == 0) {
+    const auto timeout =
+        std::chrono::steady_clock::now() - internal_->last_char_time;
+    const size_t timeout_microseconds =
+        std::chrono::duration_cast<std::chrono::microseconds>(timeout).count();
+    internal_->terminal_input_parser.Timeout(timeout_microseconds);
+    return;
+  }
+  internal_->last_char_time = std::chrono::steady_clock::now();
+
+  // Convert the chars to events.
+  for (size_t i = 0; i < l; ++i) {
+    internal_->terminal_input_parser.Add(out[i]);
+  }
+#else  // POSIX (Linux & Mac)
+  if (!CheckStdinReady()) {
+    const auto timeout =
+        std::chrono::steady_clock::now() - internal_->last_char_time;
+    const size_t timeout_ms =
+        std::chrono::duration_cast<std::chrono::milliseconds>(timeout).count();
+    internal_->terminal_input_parser.Timeout(timeout_ms);
+    return;
+  }
+  internal_->last_char_time = std::chrono::steady_clock::now();
+
+  // Read chars from the terminal.
+  std::array<char, 128> out{};
+  size_t l = read(fileno(stdin), out.data(), out.size());
+
+  // Convert the chars to events.
+  for (size_t i = 0; i < l; ++i) {
+    internal_->terminal_input_parser.Add(out[i]);
+  }
+#endif
+}
+
+void ScreenInteractive::PostAnimationTask() {
+  Post(AnimationTask());
+
+  // Repeat the animation task every 15ms. This correspond to a frame rate
+  // of around 66fps.
+  internal_->task_runner.PostDelayedTask([this] { PostAnimationTask(); },
+                                         std::chrono::milliseconds(15));
+}
+
 bool ScreenInteractive::SelectionData::operator==(
     const ScreenInteractive::SelectionData& other) const {
   if (empty && other.empty) {

src/ftxui/component/task.cpp

@@ -0,0 +1,20 @@
+// Copyright 2024 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.
+#include "ftxui/component/task_internal.hpp"
+
+namespace ftxui::task {
+bool PendingTask::operator<(const PendingTask& other) const {
+  if (!time && !other.time) {
+    return false;
+  }
+  if (!time) {
+    return true;
+  }
+  if (!other.time) {
+    return false;
+  }
+  return time.value() > other.time.value();
+}
+} // namespace ftxui::task
+

src/ftxui/component/task_internal.hpp

@@ -0,0 +1,42 @@
+// Copyright 2024 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.
+#ifndef TASK_HPP
+#define TASK_HPP
+
+#include <chrono>
+#include <functional>
+#include <optional>
+
+namespace ftxui::task {
+
+/// A task represents a unit of work.
+using Task = std::function<void()>;
+
+/// A PendingTask represents a task that is scheduled to be executed at a
+/// specific time, or as soon as possible.
+struct PendingTask {
+  // Immediate task:
+  PendingTask(Task t) : task(std::move(t)) {}  // NOLINT
+
+  // Delayed task with a duration
+  PendingTask(Task t, std::chrono::steady_clock::duration duration)
+      : task(std::move(t)),
+        time(std::chrono::steady_clock::now() + duration) {}
+
+  /// The task to be executed.
+  Task task;
+
+  /// The time when the task should be executed. If the time is empty, the task
+  /// should be executed as soon as possible.
+  std::optional<std::chrono::steady_clock::time_point> time;
+
+  /// Compare two PendingTasks by their time.
+  /// If both tasks have no time, they are considered equal.
+  bool operator<(const PendingTask& other) const;
+};
+
+} // namespace ftxui::task
+
+
+#endif  // TASK_HPP_

src/ftxui/component/task_queue.cpp

@@ -0,0 +1,54 @@
+// Copyright 2024 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.
+#include "ftxui/component/task_queue.hpp"
+
+namespace ftxui::task {
+
+auto TaskQueue::PostTask(PendingTask task) -> void {
+  if (!task.time) {
+    immediate_tasks_.push(task);
+    return;
+  }
+
+  if (task.time.value() < std::chrono::steady_clock::now()) {
+    immediate_tasks_.push(task);
+    return;
+  }
+
+  delayed_tasks_.push(task);
+}
+
+auto TaskQueue::Get() -> MaybeTask {
+  // Attempt to execute a task immediately.
+  if (!immediate_tasks_.empty()) {
+    auto task = immediate_tasks_.front();
+    immediate_tasks_.pop();
+    return task.task;
+  }
+
+  // Move all tasks that can be executed to the immediate queue.
+  auto now = std::chrono::steady_clock::now();
+  while (!delayed_tasks_.empty() && delayed_tasks_.top().time.value() <= now) {
+    immediate_tasks_.push(delayed_tasks_.top());
+    delayed_tasks_.pop();
+  }
+
+  // Attempt to execute a task immediately.
+  if (!immediate_tasks_.empty()) {
+    auto task = immediate_tasks_.front();
+    immediate_tasks_.pop();
+    return task.task;
+  }
+
+  // If there are no tasks to execute, return the delay until the next task.
+  if (!delayed_tasks_.empty()) {
+    return delayed_tasks_.top().time.value() - now;
+  }
+
+  // If there are no tasks to execute, return the maximum duration.
+  return std::monostate{};
+}
+
+} // namespace ftxui::task
+

src/ftxui/component/task_queue.hpp

@@ -0,0 +1,40 @@
+// Copyright 2024 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.
+#ifndef TASK_QUEUE_HPP
+#define TASK_QUEUE_HPP
+
+#include <queue>
+#include <variant>
+
+#include "ftxui/component/task_internal.hpp"  // for PendingTask, Task
+
+namespace ftxui::task {
+
+/// A task queue that schedules tasks to be executed in the future. Tasks can be
+/// scheduled to be executed immediately, or after a certain duration.
+/// - The tasks are executed in the order they were scheduled.
+/// - If multiple tasks are scheduled to be executed at the same time, they are
+///   executed in the order they were scheduled.
+/// - If a task is scheduled to be executed in the past, it is executed
+///   immediately.
+struct TaskQueue {
+  auto PostTask(PendingTask task) -> void;
+
+  using MaybeTask =
+      std::variant<Task, std::chrono::steady_clock::duration, std::monostate>;
+  auto Get() -> MaybeTask;
+
+  bool HasImmediateTasks() const {
+    return !immediate_tasks_.empty();
+  }
+
+ private:
+  std::queue<PendingTask> immediate_tasks_;
+  std::priority_queue<PendingTask> delayed_tasks_;
+};
+
+} // namespace ftxui::task
+
+
+#endif

src/ftxui/component/task_runner.cpp

@@ -0,0 +1,77 @@
+// Copyright 2024 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.
+#include "ftxui/component/task_runner.hpp"
+
+#include <cassert>
+#include <thread>
+
+namespace ftxui::task {
+
+static thread_local TaskRunner* current_task_runner = nullptr;  // NOLINT
+
+TaskRunner::TaskRunner() {
+  assert(!previous_task_runner_);
+  previous_task_runner_ = current_task_runner;
+  current_task_runner = this;
+}
+
+TaskRunner::~TaskRunner() {
+  current_task_runner = previous_task_runner_;
+}
+
+
+// static
+auto TaskRunner::Current() -> TaskRunner* {
+  assert(current_task_runner);
+  return current_task_runner;
+}
+
+auto TaskRunner::PostTask(Task task) -> void {
+  queue_.PostTask(PendingTask{std::move(task)});
+}
+
+auto TaskRunner::PostDelayedTask(Task task,
+                                 std::chrono::steady_clock::duration duration)
+    -> void {
+  queue_.PostTask(PendingTask{std::move(task), duration});
+}
+
+/// Runs the tasks in the queue.
+auto TaskRunner::RunUntilIdle()
+    -> std::optional<std::chrono::steady_clock::duration> {
+  while (true) {
+    auto maybe_task = queue_.Get();
+    if (std::holds_alternative<std::monostate>(maybe_task)) {
+      // No more tasks to execute, exit the loop.
+      return std::nullopt;
+    }
+
+    if (std::holds_alternative<Task>(maybe_task)) {
+      executed_tasks_++;
+      std::get<Task>(maybe_task)();
+      continue;
+    }
+
+    if (std::holds_alternative<std::chrono::steady_clock::duration>(
+            maybe_task)) {
+      return std::get<std::chrono::steady_clock::duration>(maybe_task);
+    }
+  }
+}
+
+auto TaskRunner::Run() -> void {
+  while (true) {
+    auto duration = RunUntilIdle();
+    if (!duration) {
+      // No more tasks to execute, exit the loop.
+      return;
+    }
+
+    // Sleep for the duration until the next task can be executed.
+    std::this_thread::sleep_for(duration.value());
+  }
+}
+
+} // namespace ftxui::task
+

src/ftxui/component/task_runner.hpp

@@ -0,0 +1,49 @@
+// Copyright 2024 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.
+#ifndef TASK_RUNNER_HPP
+#define TASK_RUNNER_HPP
+
+#include "ftxui/component/task_internal.hpp"
+#include "ftxui/component/task_queue.hpp"
+
+namespace ftxui::task {
+
+class TaskRunner {
+ public:
+  TaskRunner();
+  ~TaskRunner();
+
+  // Returns the task runner for the current thread.
+  static auto Current() -> TaskRunner*;
+
+  /// Schedules a task to be executed immediately.
+  auto PostTask(Task task) -> void;
+
+  /// Schedules a task to be executed after a certain duration.
+  auto PostDelayedTask(Task task,
+                       std::chrono::steady_clock::duration duration) -> void;
+
+  /// Runs the tasks in the queue, return the delay until the next delayed task
+  /// can be executed.
+  auto RunUntilIdle() -> std::optional<std::chrono::steady_clock::duration>;
+
+  // Runs the tasks in the queue, blocking until all tasks are executed.
+  auto Run() -> void;
+
+  bool HasImmediateTasks() const {
+    return queue_.HasImmediateTasks();
+  }
+
+  size_t ExecutedTasks() const { return executed_tasks_; }
+
+ private:
+  TaskRunner* previous_task_runner_ = nullptr;
+  TaskQueue queue_;
+  size_t executed_tasks_ = 0;
+};
+
+} // namespace ftxui::task
+
+
+#endif  // TASK_RUNNER_HPP

src/ftxui/component/task_test.cpp

@@ -0,0 +1,94 @@
+// Copyright 2024 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.
+// Copyright 2024 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.
+#include "ftxui/component/task_internal.hpp"
+
+#include <gtest/gtest.h>
+
+#include <thread>  // for sleep_for
+#include "ftxui/component/task_runner.hpp"
+
+namespace ftxui::task {
+
+TEST(TaskTest, Basic) {
+  std::vector<int> values;
+
+  auto task_1 = [&values] { values.push_back(1); };
+  auto task_2 = [&values] { values.push_back(2); };
+  auto task_3 = [&values] { values.push_back(3); };
+
+  auto runner = TaskRunner();
+
+  runner.PostTask(task_1);
+  runner.PostTask(task_2);
+  runner.PostTask(task_3);
+  while (true) {
+    auto duration = runner.RunUntilIdle();
+    if (!duration) {
+      break;
+    }
+    std::this_thread::sleep_for(duration.value());
+  }
+
+  EXPECT_EQ(values, (std::vector<int>{1, 2, 3}));
+}
+
+TEST(TaskTest, PostedWithinTask) {
+  std::vector<int> values;
+
+  auto task_1 = [&values] {
+    values.push_back(1);
+    auto task_2 = [&values] { values.push_back(5); };
+    TaskRunner::Current()->PostTask(std::move(task_2));
+    values.push_back(2);
+  };
+
+  auto task_2 = [&values] {
+    values.push_back(3);
+    auto task_2 = [&values] { values.push_back(6); };
+    TaskRunner::Current()->PostTask(std::move(task_2));
+    values.push_back(4);
+  };
+
+  auto runner = TaskRunner();
+
+  runner.PostTask(task_1);
+  runner.PostTask(task_2);
+  while (true) {
+    auto duration = runner.RunUntilIdle();
+    if (!duration) {
+      break;
+    }
+    std::this_thread::sleep_for(duration.value());
+  }
+
+  EXPECT_EQ(values, (std::vector<int>{1, 2, 3, 4, 5, 6}));
+}
+
+TEST(TaskTest, RunDelayedTask) {
+  std::vector<int> values;
+
+  auto task_1 = [&values] { values.push_back(1); };
+  auto task_2 = [&values] { values.push_back(2); };
+  auto task_3 = [&values] { values.push_back(3); };
+
+  auto runner = TaskRunner();
+
+  runner.PostDelayedTask(task_3, std::chrono::milliseconds(300));
+  runner.PostDelayedTask(task_1, std::chrono::milliseconds(100));
+  runner.PostDelayedTask(task_2, std::chrono::milliseconds(200));
+  while (true) {
+    auto duration = runner.RunUntilIdle();
+    if (!duration) {
+      break;
+    }
+    std::this_thread::sleep_for(duration.value());
+  }
+
+  EXPECT_EQ(values, (std::vector<int>{1, 2, 3}));
+}
+
+} // namespace ftxui::task