1 files changed, 197 insertions, 0 deletions
diff --git a/examples/async/eratosthenes/eratosthenes_trio.py b/examples/async/eratosthenes/eratosthenes_trio.py
new file mode 100644
index 000000000..89d3d1ce6
--- /dev/null
+++ b/examples/async/eratosthenes/eratosthenes_trio.py
@@ -0,0 +1,197 @@
+# Copyright (C) 2022 The Qt Company Ltd.
+# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+from PySide6.QtCore import (Qt, QEvent, QObject, QTimer, Signal, Slot)
+from PySide6.QtGui import (QColor, QFont, QPalette)
+from PySide6.QtWidgets import (QApplication, QGridLayout, QLabel, QMainWindow, QVBoxLayout, QWidget)
+
+import outcome
+import signal
+import sys
+import traceback
+import trio
+from random import randint
+
+
+class MainWindow(QMainWindow):
+
+    set_num = Signal(int, QColor)
+
+    def __init__(self, rows, cols):
+        super().__init__()
+
+        self.rows = rows
+        self.cols = cols
+
+        widget_central = QWidget()
+        self.setCentralWidget(widget_central)
+
+        layout_outer = QVBoxLayout(widget_central)
+
+        self.widget_outer_text = QLabel()
+        font = QFont()
+        font.setPointSize(14)
+        self.widget_outer_text.setFont(font)
+        layout_outer.addWidget(self.widget_outer_text, alignment=Qt.AlignmentFlag.AlignCenter)
+
+        widget_inner_grid = QWidget()
+        layout_outer.addWidget(widget_inner_grid, alignment=Qt.AlignmentFlag.AlignCenter)
+
+        self.layout_inner_grid = QGridLayout(widget_inner_grid)
+        k = 1
+        for i in range(self.rows):
+            for j in range(self.cols):
+                box = QLabel(f"{k}")
+                self.layout_inner_grid.addWidget(box, i, j, Qt.AlignmentFlag.AlignCenter)
+                k += 1
+
+        self.set_num.connect(self.set_num_handler)
+
+    @Slot(int, QColor)
+    def set_num_handler(self, i, color):
+        row = int((i - 1) / self.cols)
+        col = (i - 1) - (row * self.cols)
+        widget = self.layout_inner_grid.itemAtPosition(row, col).widget()
+
+        font = QFont()
+        font.setWeight(QFont.Bold)
+        palette = QPalette()
+        palette.setColor(QPalette.WindowText, color)
+        widget.setFont(font)
+        widget.setPalette(palette)
+
+
+class Eratosthenes(QObject):
+
+    """ This Sieve of Eratosthenes runs on a configurable tick (default
+        0.1 seconds). At each tick, a new subroutine will be created
+        that will check multiples of the next prime number. Each of
+        these subroutines also operates on the same tick. """
+
+    def __init__(self, num, window, tick=0.1):
+        super().__init__()
+        self.num = num
+        self.sieve = [True] * self.num
+        self.base = 0
+        self.window = window
+        self.tick = tick
+        self.coroutines = []
+        self.done = False
+        self.nursery = None
+
+    async def start(self):
+        async with trio.open_nursery() as self.nursery:
+            self.nursery.start_soon(self.update_text)
+            while self.base <= self.num / 2:
+                await trio.sleep(self.tick)
+                for i in range(self.base + 1, self.num):
+                    if self.sieve[i]:
+                        self.base = i
+                        break
+                self.nursery.start_soon(self.mark_number, self.base + 1)
+            while sum(self.coroutines) > 0:
+                await trio.sleep(self.tick)
+            self.done = True
+
+    async def mark_number(self, base):
+        id = len(self.coroutines)
+        self.coroutines.append(1)
+        color = QColor(randint(64, 192), randint(64, 192), randint(64, 192))
+        for i in range(2 * base, self.num + 1, base):
+            if self.sieve[i - 1]:
+                self.sieve[i - 1] = False
+                self.window.set_num.emit(i, color)
+            await trio.sleep(self.tick)
+        self.coroutines[id] = 0
+
+    async def update_text(self):
+        while not self.done:
+            await trio.sleep(self.tick)
+            if int(trio.lowlevel.current_clock().current_time() + self.tick) % 2:
+                text = "⚙️ ...Calculating prime numbers... ⚙️"
+            else:
+                text = "👩‍💻 ...Hacking the universe... 👩‍💻"
+            self.window.widget_outer_text.setText(text)
+
+        self.window.widget_outer_text.setText(
+            "🥳 Congratulations! You found all the prime numbers and solved mathematics. 🥳"
+        )
+
+
+class AsyncHelper(QObject):
+
+    class ReenterQtObject(QObject):
+        """ This is a QObject to which an event will be posted, allowing
+            Trio to resume when the event is handled. event.fn() is the
+            next entry point of the Trio event loop. """
+        def event(self, event):
+            if event.type() == QEvent.Type.User + 1:
+                event.fn()
+                return True
+            return False
+
+    class ReenterQtEvent(QEvent):
+        """ This is the QEvent that will be handled by the ReenterQtObject.
+            self.fn is the next entry point of the Trio event loop. """
+        def __init__(self, fn):
+            super().__init__(QEvent.Type(QEvent.Type.User + 1))
+            self.fn = fn
+
+    def __init__(self, worker, entry):
+        super().__init__()
+        self.reenter_qt = self.ReenterQtObject()
+        self.entry = entry
+
+        self.worker = worker
+        if hasattr(self.worker, "start_signal") and isinstance(self.worker.start_signal, Signal):
+            self.worker.start_signal.connect(self.launch_guest_run)
+
+    @Slot()
+    def launch_guest_run(self):
+        """ To use Trio and Qt together, one must run the Trio event
+            loop as a "guest" inside the Qt "host" event loop. """
+        if not self.entry:
+            raise Exception("No entry point for the Trio guest run was set.")
+        trio.lowlevel.start_guest_run(
+            self.entry,
+            run_sync_soon_threadsafe=self.next_guest_run_schedule,
+            done_callback=self.trio_done_callback,
+        )
+
+    def next_guest_run_schedule(self, fn):
+        """ This function serves to re-schedule the guest (Trio) event
+            loop inside the host (Qt) event loop. It is called by Trio
+            at the end of an event loop run in order to relinquish back
+            to Qt's event loop. By posting an event on the Qt event loop
+            that contains Trio's next entry point, it ensures that Trio's
+            event loop will be scheduled again by Qt. """
+        QApplication.postEvent(self.reenter_qt, self.ReenterQtEvent(fn))
+
+    def trio_done_callback(self, outcome_):
+        """ This function is called by Trio when its event loop has
+            finished. """
+        if isinstance(outcome_, outcome.Error):
+            error = outcome_.error
+            traceback.print_exception(type(error), error, error.__traceback__)
+
+
+if __name__ == "__main__":
+    rows = 40
+    cols = 40
+    num = rows * cols
+
+    app = QApplication(sys.argv)
+    main_window = MainWindow(rows, cols)
+    eratosthenes = Eratosthenes(num, main_window)
+    async_helper = AsyncHelper(eratosthenes, eratosthenes.start)
+
+    # This establishes the entry point for the Trio guest run. It varies
+    # depending on how and when its event loop is to be triggered, e.g.,
+    # from the beginning (as here) or rather at a specific moment like
+    # a button press.
+    QTimer.singleShot(0, async_helper.launch_guest_run)
+
+    main_window.show()
+
+    signal.signal(signal.SIGINT, signal.SIG_DFL)
+    app.exec()