Document the meaning of display/window/stretch/aspect

[PGijsbers]

Add documentation for ProjectSettings.display/window/stretch/aspect.

I understand bad documentation is worse than no documentation. I'd be happy to make changes, though I understand closing the PR if it's poor since it probably takes much longer to educate me rather than write the docs.

I could not find related issues or PRs.

[Chubercik]

LGTM

[PGijsbers]

Suggested change

	Defines if and how the aspect ratio of the root [Viewport] should be preserved when stretching is applied.
	[b]"ignore"[/b]: Keep the width and height of the viewport. If the aspect ratio of the window or screen does not match that of the viewport, stretch the render to fill it.
	[b]"keep"[/b]: Keep the width and height of the viewport. If the aspect ratio of the window or screen does not match that of the viewport, empty space is filled with black.
	[b]"keep_width"[/b]: Keep the width of the viewport, but allow its height to expand. If the aspect ratio of the window or screen is greater, the game is shown centered with vertical black bars. If the aspect ratio is smaller, the viewport is expanded vertically downwards.
	[b]"keep_height"[/b]: Keep the height of the viewport, but allow its width to expand. If the aspect ratio of the window or screen is smaller, the game is shown centered with horizontal black bars. If the aspect ratio is greater, the viewport is expanded horizontally to the right.
	[b]"expand"[/b]: Allow the viewport to expand in either direction to fill the screen or window. If the aspect ratio of the window or screen is greater, the game is expanded horizontally to the right. If the aspect ratio is smaller, the viewport is expanded vertically downwards.
	Defines if and how the aspect ratio of the root [Viewport] should be preserved when stretching is applied.
	[b]"ignore"[/b]: Keep the width and height of the viewport. If the aspect ratio of the window or screen does not match that of the viewport, stretch the render to fill it.
	[b]"keep"[/b]: Keep the width and height of the viewport. If the aspect ratio of the window or screen does not match that of the viewport, empty space is filled with black.
	[b]"keep_width"[/b]: Keep the width of the viewport, but allow its height to expand. If the aspect ratio of the window or screen is wider, the game is shown centered with vertical black bars. If the aspect ratio is narrower, the viewport is expanded vertically downwards.
	[b]"keep_height"[/b]: Keep the height of the viewport, but allow its width to expand. If the aspect ratio of the window or screen is narrower, the game is shown centered with horizontal black bars. If the aspect ratio is wider, the viewport is expanded horizontally to the right.
	[b]"expand"[/b]: Allow the viewport to expand in either direction to fill the screen or window. If the aspect ratio of the window or screen is wider, the game is expanded horizontally to the right. If the aspect ratio is narrower, the viewport is expanded vertically downwards.

[PGijsbers]

Sorry to edit things after the review, so I propose it through the suggestions. After sleeping on it, I think it's probably better to use narrower (instead of smaller) and wider (instead of greater), as the meaning w.r.t. game screen/window shape is more intuitive.

[Chubercik]

No worries, though I'm not sure about the change; more intuitive, sure, but in the context of aspect ratios, comparisons would usually use words like smaller/greater, no? I'm not a native speaker so I wouldn't want to call the shots here, we might want to wait for a review from someone on the docs team.

[PGijsbers]

I wasn't sure either, which is why I initially used greater/smaller (since it's a ratio, it's at least correct). However, reading the wikipedia page they do use "wider/narrower" in this context:

but converted when the international standards group introduced a wider ratio of 5+1⁄3 to 3 (= 16:9).

and

which progressed to a wider 4:3

and

This aspect ratio is also wider than the popular 16:9

and

Notably one of the few popular display aspect ratios narrower than 4:3

So I'll leave it for your (and the docs team's) consideration.

[PGijsbers]

I don't know why I couldn't find it yesterday, but I found the proper documentation page for this now: https://docs.godotengine.org/en/stable/tutorials/rendering/multiple_resolutions.html#stretch-aspect

I can update the PR to include these descriptions instead, or is there a way to instead share the same source to reduce the risk of the doc pages and attribute documentation get out-of-sync? And/or can we link to this documentation directly? The animated gifs will be very useful.