fixed window flashing bug

apps/studio/src/orisys_studio/ui/mesh3d_panel.py

@@ -115,6 +115,30 @@ class Mesh3dPanel(QFrame):
         #: ``set_domain_latch``). Held until the view exists.
         self._domain_latch = None
 
+        # Reserve this top-level window's native handle *now*, before the window is
+        # shown and while no OpenGL widget exists yet.
+        #
+        # The view is built on first use, so on a first run — the pane starts on a box,
+        # which has no 3D scene — the GL widget is created later, while the window is
+        # already on screen. Creating the first *native* child of a visible window makes
+        # Qt re-create the window, and Qt does that by hiding it and showing it again:
+        # measured here as a 250–400 ms disappearance of the whole application, with the
+        # popup or transient dialog that was open losing its activation and being
+        # dismissed with it. (``QOpenGLWidget`` sets ``WA_NativeWindow`` on itself.)
+        # Switching the sensor to ``finger`` in the sensor dialog is exactly that moment,
+        # which is why it read as "the window closes and reopens and the dialog closes by
+        # itself".
+        #
+        # One zero-sized native child is enough: Qt then already owns a native window
+        # handle when the 3D widget is added, and no recreation — and so no hide/show —
+        # happens. It reserves the handle only; it creates no context, no scene and no GL
+        # import, so the pane stays as lazy as it was. There is no "re-layout" to force
+        # here: the window was never meant to be hidden at all.
+        self._native_handle = QWidget(self)
+        self._native_handle.setObjectName("mesh3dNativeHandle")
+        self._native_handle.setGeometry(0, 0, 0, 0)
+        self._native_handle.winId()  # creating the handle *is* the point
+
         root = QVBoxLayout(self)
         root.setContentsMargins(0, 0, 0, 0)
         # The header carries the title and the two actions that belong to *looking*:
@@ -324,7 +348,6 @@ class Mesh3dPanel(QFrame):
         if self._loaded or self._source is None or self._view is None:
             return
         self._loaded = True
-        view = self._view
         if self._loader is None:
             self._loader = SceneAssetLoader(self)
             self._loader.loaded.connect(self._on_loaded)