Opening 2D/3D scene when no scene was previously open no longer switches to 2D/3D viewport

[akien-mga]

Tested versions

• Reproducible in 4.3.stable and 4.4.dev (514c564)
• Not reproducible in 4.2.2.stable

System information

Fedora Linux 40 (KDE Plasma) - Wayland - Vulkan (Forward+) - dedicated AMD Radeon RX 7600M XT (RADV NAVI33) - AMD Ryzen 7 7840HS w/ Radeon 780M Graphics (16 Threads)

Issue description

Godot has this nifty behavior that it can detect the type of a scene (2D or 3D) based on its root node, and infer the viewport (2D/3D) to open for that scene accordingly.

This seems to have regressed in 4.3.stable and later.

What works:

• Open a 2D scene and make sure to be on the 2D viewport.
• Open a 3D scene: it will switch to the 3D viewport.
• Close the 2D scene, reopen it: it will switch to the 2D viewport.

What doesn't work:

• Have no scene open, make sure to be on the 2D viewport.
• Open a 3D scene: it stays on the 2D viewport.
• Close the 3D scene, make sure to be on the 3D viewport.
• Open a 2D scene: it stays on the 3D viewport.

CC @KoBeWi

Steps to reproduce

See above.

Minimal reproduction project (MRP)

Test2DAnd3DScenes.zip

[matheusmdx]

Bisecting points to #91435 as the culprit, @ajreckof

[fire]

Read the #91435 description seems like this was a bugfix, but I not sure how to restore it without breaking it.

[ajreckof]

So what happens here is that when opening a scene it was always selecting the root of the scene when loading in addition to whatever the selection was and this made a lot of problems. The fact that it was switching to the 2D/3D viewer was simply a consequence of this selection. One thing I suggested was to add back the selection in the cases where there is no prior selection. If the switch is always wanted whatever the selection and only depending on the root node then I could add a patch in this way too.

[KoBeWi]

If the switch is always wanted whatever the selection and only depending on the root node then I could add a patch in this way too.

This seems to be the old behavior. #91411 is a regression between dev5 and dev6. In dev5 root node is not selected, but the editor switches correctly.

EDIT:
To be precise, this only happens with no selection. If the newly opened scene has selected node, that node is used instead.