migrate pyqt5 to pyside6

apps/studio/tests/conftest.py

@@ -3,6 +3,10 @@
 The tests render real Qt widgets with the offscreen platform plugin, so they need
 no display and no camera hardware. A single ``QApplication`` is shared by the
 whole session (Qt forbids creating more than one).
+
+The suite requires PySide6, the app's only Qt binding. Where it is missing the
+modules are skipped rather than failed, so a broken environment cannot look like a
+broken application (the same rule ``apps/autocal`` follows).
 """
 
 from __future__ import annotations
@@ -16,11 +20,30 @@ from pathlib import Path
 import pytest
 
 os.environ.setdefault("QT_QPA_PLATFORM", "offscreen")
+# In a development environment that also has PyQt5 installed, pyqtgraph would otherwise
+# bind to it (it takes whichever toolkit it finds first) and the plots would break.
+os.environ.setdefault("PYQTGRAPH_QT_LIB", "PySide6")
 if sys.platform == "win32" and "QT_QPA_FONTDIR" not in os.environ:
     _fonts = Path(os.environ.get("WINDIR", r"C:\Windows")) / "Fonts"
     if _fonts.is_dir():
         os.environ["QT_QPA_FONTDIR"] = str(_fonts)
 
+
+def _have_pyside6() -> tuple[bool, str]:
+    try:
+        import PySide6
+    except ImportError as exc:  # pragma: no cover - depends on the machine
+        return False, str(exc)
+    return True, getattr(PySide6, "__version__", "unknown")
+
+
+HAVE_PYSIDE6, PYSIDE6_VERSION = _have_pyside6()
+
+if not HAVE_PYSIDE6:  # pragma: no cover - depends on the machine
+    # Mirrors apps/autocal/tests/conftest.py: nothing is collected, so a machine without
+    # the binding reports no tests instead of a wall of import errors.
+    collect_ignore_glob = ["test_*.py"]
+
 # ``tools/ui_check.py`` owns the palette rules; importing it keeps one source of
 # truth between the pytest suite and the dependency-free checker.
 _TOOLS_DIR = Path(__file__).resolve().parents[1] / "tools"
@@ -30,7 +53,7 @@ if _TOOLS_DIR.is_dir() and str(_TOOLS_DIR) not in sys.path:
 
 @pytest.fixture(scope="session")
 def qt_app():
-    from PyQt5.QtWidgets import QApplication
+    from PySide6.QtWidgets import QApplication
 
     app = QApplication.instance() or QApplication([])
     yield app
@@ -83,7 +106,7 @@ def visible_descendants(widget):
 
 def show_window(window, size):
     """Show a window at ``size`` and flush pending Qt events."""
-    from PyQt5.QtWidgets import QApplication
+    from PySide6.QtWidgets import QApplication
 
     window.resize(*size)
     window.show()