Add viewport override to 2D editor

[KoBeWi]

This PR supersedes #61873 with alternative approach.
Instead of enabling other viewports and fighting with the editor to make it work properly, I added a button that allows to override the default 2D editor viewport with another one.

viewport.override.mp4

I have one unresolved problem though - the overriding viewport's size must match the editor's size to display properly. Right now I'm just displaying its content with a TextureRect, but maybe I should use some different approach, idk.
I didn't make much progress for some time, so I'm opening a draft.

Closes godotengine/godot-proposals#2139
Closes godotengine/godot-proposals#5422

[KoBeWi]

Ok this is somewhat finished. I fixed the viewport problems by adding more viewports. So the 2D editor structure is now SubViewportContainer -> SubViewport -> TextureRect -> current viewport.

The current viewport is still displayed inside TextureRect, but screen transform is now different. While using main viewport, the displayed viewports' transform is changed. If the viewport is overriden, the containing viewport (the one under SubViewportContainer) is transformed instead and the overriding viewport is displayed in local space. It works quite well.

godot.windows.editor.dev.x86_64_ajTVBn3MD9.mp4

I'm really surprised that selecting nodes works without any problems in this setup.

The only problem are Window nodes. For whatever reason they don't redraw when content changes and don't draw anything while invisible.

godot.windows.editor.dev.x86_64_xk6EogJICc.mp4

(I also remembered that the override button is buggy)

But it's ready to be ready for review I think.

EDIT:
Also this is funny with Camera2D

godot.windows.editor.dev.x86_64_vLvG7cbxP7.mp4

[jordanlis]

This is amazing, really need that one :)

[Calinou]

@Variable-ind Please don't bump issues without contributing significant new information. Use the 👍 reaction button on the first post instead.

[Summersay415]

What's status of this?

[KoBeWi]

Needs testing and review.

[Summersay415]

Tested locally, works good with some caveats you mentioned. Suggestion: how about not restricting rendering outside of the overridden viewport, as in a normal, not overridden one?

[KoBeWi]

This is a technical restriction. The main viewport works a bit differently - when you move around, its canvas is transformed and displays a different region. The rendering is still restricted to the viewport's size, but it has the size of the editor, so you don't see that objects outside don't render.

[akien-mga]

Needs rebase, and then going around to poke people on #editor to actually get this reviewed :P

[jan-Kulpas]

Would this also work for 3D nodes with a 2D Subviewport?

[KoBeWi]

No, this doesn't cover 3D.

[AndreaTerenz]

Looks really good!
But what about multiple subviewports in the same scene? Would it be a simple extension to turn the toggle button into a dropdown to select a specific subview?

[KoBeWi]

Currently you have to select SubViewport node and click the button on the toolbar. You can preview any SubViewport in the scene using that.

[Calinou]

Tested locally, it works as expected in all rendering methods.

It even works with viewports that contain 3D nodes, as long as it's previewed within the 2D editor 🙂

Some feedback:

• It's hard to distinguish between the button being disabled (when a non-Viewport node is selected), enabled, and active:

Disabled	Enabled	Active

I suggest using a copy of the icon that is white, so that it's more visible (and there's higher contrast between the disabled and enabled state).

• There should be tooltip when hovering the aforementioned button. Something like this:

Viewport Override
Overrides the 2D editor view with the contents of the selected Viewport node.

This would match the tooltip of the Project Camera Override button nicely (which is right besides it).

[KoBeWi]

The button was using old style. Changed it to use the new FlatButton:

godot.windows.editor.dev.x86_64_NaJWFVzTEP.mp4

I also added tooltips:

I also found a bug where main screen plugin does not receive edit(null), causing invalid button state when node is deselected. It should be fixed separately.

[kitbdev]

• also fixes GUI/Control node in Viewport tree does not preview in layout mode in editor  #39387
• related, but 3D Allow to edit objects of SubViewports that have the Own World property enabled godot-proposals#1465

[KoBeWi]

Rebased, but the root viewport is bugged for some reason. Its ViewportTexture is smaller than the viewport, so the 2D editor view is cropped.