Rework content scale to provide more options, add integer scaling

[Calinou]

I need help to finish this feature. If you want to see this for 4.0, please lend a hand 🙂

cc @Yukitty, @starry-abyss

• Add content stretch modes Fractional (default), Integer and Hybrid.

  • All modes work with any stretch mode and aspect.
  • Fractional behaves as Godot currently does when scaling viewports. Pixel art will only look good when the window is scaled at an integer multiple of the original size.
  • Integer enforces an integer scale for the final display (rounded down from the automatically computed fractional scale). This provides crisp pixel art appearance.
    • Black bars may be displayed on all sides when using the viewport stretch mode. When using the canvas_items stretch mode, no black bars are displayed (unless the stretch aspect requires it), but the game's viewable area will change in 2D.
  • (Not implemented yet): Hybrid enforces an integer scale on the internal rendering resolution (rounding up), but the viewport will be stretched down to the final display with linear filtering. This provides good pixel art appearance, though not as crisp as the Integer mode. This is known as Sharp Bilinear in some other apps, though I think we should go for a shader-less approach.

• Tweak project setting for stretch scale to allow values as low as 0.5 (values below 1 are valid, and can be useful for UI testing purposes).

Testing project: test_stretch_master.zip

TODO

• Make UI anchors work properly when using integer scaling mode.
• Implement hybrid scaling mode.

This closes godotengine/godot-proposals#1666.

[starry-abyss]

I've just attached a minimal hybrid scaling project for Godot 3 implemented in nodes: godotengine/godot-proposals#1666 (comment)

Hope it helps!

[starry-abyss]

Maybe I don't fully understand how to use this, but I don't see what I expect to see with integer scaling. When I resize the window, the new integer scale isn't automatically chosen. Instead, there is a smooth fractional scaling.

Ideally I'd like to have 2 approaches:

1. the default one with fixed game size, bars on sides and automatic scale calculation to fit all the scene with max possible zoom while staying integer.
   Example 1: if game size is 400x300 and window size is 700x600, then scale is 1, because for a scale of 2 one needs 800 or more window pixels horizontally. So there would be 150 pixels bars on each side around the game scene.
   Example 2: if game size is 400x300 and window size is 1500x1000, then scale is 3, with 150 pixels bars on the left and right, and 50 pixels bars on top and bottom.
2. a special case for some games: imagine a FPS or RTS style 3D game, where the amount of what you can see depends on the aspect ratio of the window (there are no bars on sides). Then replace graphics with 2D pixel art and add integer scaling on top. So instead of bars you get more area of view. And to balance scale factor depending on resolution and aspect ratio, I expect a way to turn off the stock scale calculator from approach 1, to calculate the desired integer ratio in the script on window resize event and then be able to set it in the engine.

[dkaste]

Is there a reason why the content scale feature is implemented on Window instead of Viewport?

I have a project that uses viewports to contain multiple game instances in the same window. It would be nice to be able to scale the canvas items (i.e. GUI) in each viewport instead of globally on the window.

[Calinou]

• Superseded by Add content scale stretch modes, implement integer scaling #75784.