fix: deal with the threads being initialized in the process_frame callback with a threading.Lock

Author: sassanh

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## Upcoming
+
+- fix: deal with the threads being initialized in the `process_frame` callback with a `threading.Lock`
+
 ## Version 0.12.3
 
 - chore: update dependencies, update code with the latest ruff and pyright rules

demo.py

@@ -60,24 +60,25 @@ def build(self) -> FboGridLayout:
         """Build the demo application."""
         fbg = FboGridLayout(rows=2, cols=2)
 
+        shape_by_label = {}
         for index, color in enumerate(
             [(1, 0, 0, 1), (0, 1, 0, 1), (0, 0, 1, 1), (1, 1, 0, 0)],
         ):
             label = Label(text=f'Hello {index}')
 
             with label.canvas.before:
                 Color(*color)
-                label.shape = Ellipse()
+                shape_by_label[label] = Ellipse()
 
             label.bind(
                 size=lambda label, *_: (
                     setattr(
-                        label.shape,
+                        shape_by_label[label],
                         'size',
                         (label.size[0] / 2, label.size[1] / 2),
                     ),
                     setattr(
-                        label.shape,
+                        shape_by_label[label],
                         'pos',
                         (
                             label.pos[0] + label.size[0] / 4,
@@ -86,7 +87,7 @@ def build(self) -> FboGridLayout:
                     ),
                 ),
                 pos=lambda label, *_: setattr(
-                    label.shape,
+                    shape_by_label[label],
                     'pos',
                     (
                         label.pos[0] + label.size[0] / 4,

headless_kivy/config.py

@@ -29,7 +29,7 @@
 if TYPE_CHECKING:
     from numpy._typing import NDArray  # pyright: ignore[reportPrivateImportUsage]
 
-kivy.require('2.1.0')
+kivy.require('2.1.0')  # pyright: ignore[reportAttributeAccessIssue]
 
 
 class SetupHeadlessConfig(TypedDict):

headless_kivy/widget.py

@@ -6,9 +6,10 @@
 
 from __future__ import annotations
 
+import contextlib
 import threading
 import time
-from queue import Queue
+from queue import Empty, Queue
 from threading import Thread
 from typing import TYPE_CHECKING, ClassVar
 
@@ -67,6 +68,7 @@ def __init__(self: HeadlessWidget, **kwargs: object) -> None:
 
         __import__('kivy.core.window')
 
+        self.thread_lock = threading.Lock()
         self.last_thread: threading.Thread | None = None
         self.last_render = 0
         self.render_queue = Queue(2 if config.double_buffering() else 1)
@@ -171,19 +173,20 @@ def process_frame(self: HeadlessWidget, *_: object) -> None:
         if not np.any(mask):
             return
 
-        self.last_thread = Thread(
-            target=self.render,
-            kwargs={
-                'mask': mask,
-                'data': data,
-                'x': x,
-                'y': y,
-                'last_thread': self.last_thread,
-            },
-            daemon=False,
-        )
-        self.render_queue.put(self.last_thread)
-        self.last_thread.start()
+        with self.thread_lock:
+            new_thread = self.last_thread = Thread(
+                target=self.render,
+                kwargs={
+                    'mask': mask,
+                    'data': data,
+                    'x': x,
+                    'y': y,
+                    'last_thread': self.last_thread,
+                },
+                daemon=False,
+            )
+            self.render_queue.put(new_thread)
+        new_thread.start()
         self.last_render = time.time()
 
     def render(
@@ -271,7 +274,8 @@ def render(
                 for region in regions
             ],
         )
-        self.render_queue.get_nowait()
+        with contextlib.suppress(Empty):
+            self.render_queue.get_nowait()
 
     @classmethod
     def get_instance(

pyproject.toml

@@ -89,6 +89,7 @@ profile = "black"
 [tool.pyright]
 exclude = ['typings', '.venv']
 filterwarnings = 'error'
+disableTaggedHints = true
 
 [tool.coverage.report]
 exclude_also = ["if TYPE_CHECKING:"]