fix(present): black video flashes and other bugs linked to Qt (#465)

* Relies on Pixel Format instead of Size

* chore(lib): remove deprecated warning

* chore(deps): update lockfiles

* chore(lib): cleanup code

* chore(ci): run fmt

* chore: update changelog

* chore: typo

* chore(docs): remove ref. to black screen

* fix(deps): issue on Windows

---------

Co-authored-by: PeculiarProgrammer <179261820+PeculiarProgrammer@users.noreply.github.com>

CHANGELOG.md

@@ -37,6 +37,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   [#429](https://github.com/jeertmans/manim-slides/pull/429)
 - Fixed whitespace issue in default RevealJS template.
   [#442](https://github.com/jeertmans/manim-slides/pull/442)
+- Fixed black screen issue on recent Qt versions and device loss detected,
+  thanks to [@PeculiarProgrammer](https://github.com/PeculiarProgrammer)!
+  [#465](https://github.com/jeertmans/manim-slides/pull/465)
 
 (unreleased-removed)=
 ### Removed

docs/source/installation.md

@@ -113,10 +113,7 @@ using optional dependencies:
   and does not work with ManimGL;
 - `manim` and `manimgl`, for installing the corresponding
   dependencies;
-- `pyqt6` to include PyQt6 Qt bindings. Those bindings are available
-  on most platforms and Python version, but produce a weird black
-  screen between slide with `manim-slides present`,
-  see [#QTBUG-118501](https://bugreports.qt.io/browse/QTBUG-118501);
+- `pyqt6` to include PyQt6 Qt bindings;
 - `pyqt6-full` to include `full` and `pyqt6`;
 - `pyside6` to include PySide6 Qt bindings. Those bindings are available
   on most platforms and Python version, except on Python 3.12[^2];

manim_slides/present/__init__.py

@@ -11,23 +11,6 @@
 from ..config import Config, PresentationConfig
 from ..logger import logger
 
-PREFERRED_QT_VERSIONS = ("6.5.1", "6.5.2")
-
-
-def warn_if_non_desirable_pyside6_version() -> None:
-    from qtpy import API, QT_VERSION
-
-    if sys.version_info < (3, 12) and (
-        API != "pyside6" or QT_VERSION not in PREFERRED_QT_VERSIONS
-    ):
-        logger.warn(
-            f"You are using {API = }, {QT_VERSION = }, "
-            "but we recommend installing 'PySide6==6.5.2', mainly to avoid "
-            "flashing screens between slides, "
-            "see issue https://github.com/jeertmans/manim-slides/issues/293. "
-            "You can do so with `pip install 'manim-slides[pyside6]'`."
-        )
-
 
 @click.command()
 @folder_path_option
@@ -302,8 +285,6 @@ def present(
     if start_at[1]:
         start_at_slide_number = start_at[1]
 
-    warn_if_non_desirable_pyside6_version()
-
     from qtpy.QtCore import Qt
     from qtpy.QtGui import QScreen
 

manim_slides/present/player.py

@@ -226,6 +226,8 @@ def __init__(
         self.icon = QIcon(":/icon.png")
         self.setWindowIcon(self.icon)
 
+        self.frame = QVideoFrame()
+
         self.audio_output = QAudioOutput()
         self.video_widget = QVideoWidget()
         self.video_sink = self.video_widget.videoSink()
@@ -240,26 +242,14 @@ def __init__(
         self.presentation_changed.connect(self.presentation_changed_callback)
         self.slide_changed.connect(self.slide_changed_callback)
 
-        old_frame = None
-
-        def frame_changed(frame: QVideoFrame) -> None:
-            nonlocal old_frame
-
-            if old_frame and (frame.size() != old_frame.size()):
-                self.video_sink.setVideoFrame(old_frame)
-                frame = old_frame
-
-            self.info.video_sink.setVideoFrame(frame)
-            old_frame = frame
-
         self.info = Info(
             full_screen=full_screen,
             aspect_ratio_mode=aspect_ratio_mode,
             screen=info_window_screen,
         )
         self.info.close_event.connect(self.closeEvent)
         self.info.key_press_event.connect(self.keyPressEvent)
-        self.video_sink.videoFrameChanged.connect(frame_changed)
+        self.video_sink.videoFrameChanged.connect(self.frame_changed)
         self.hide_info_window = hide_info_window
 
         # Connecting key callbacks
@@ -555,6 +545,34 @@ def hide_mouse(self) -> None:
         else:
             self.setCursor(Qt.BlankCursor)
 
+    def frame_changed(self, frame: QVideoFrame) -> None:
+        """
+        Slot to handle possibly invalid frames.
+
+        This slot cannot be decorated with ``@Slot`` as
+        the video sinks are handled in different threads.
+
+        As of Qt>=6.5.3, the last frame of every video is "flushed",
+        resulting in a short black screen between each slide.
+
+        To avoid this issue, we check every frame, and avoid playing
+        invalid ones.
+
+        References
+        ----------
+        1. https://github.com/jeertmans/manim-slides/issues/293
+        2. https://github.com/jeertmans/manim-slides/pull/464
+
+        :param frame: The most recent frame.
+
+        """
+        if frame.isValid():
+            self.frame = frame
+        else:
+            self.video_sink.setVideoFrame(self.frame)  # Reuse previous frame
+
+        self.info.video_sink.setVideoFrame(self.frame)
+
     def closeEvent(self, event: QCloseEvent) -> None:  # noqa: N802
         self.close()
 

pyproject.toml

@@ -60,7 +60,7 @@ full = [
 magic = ["manim-slides[manim]", "ipython>=8.12.2"]
 manim = ["manim>=0.18.0"]
 manimgl = ["manimgl>=1.6.1;python_version<'3.12'"]
-pyqt6 = ["pyqt6>=6.6.1"]
+pyqt6 = ["pyqt6>=6.7.0"]
 pyqt6-full = ["manim-slides[full,pyqt6]"]
 pyside6 = ["pyside6>=6.6.1"]
 pyside6-full = ["manim-slides[full,pyside6]"]