ebiten: expose the default implementation of FinalScreenDrawer

[noppikinatta]

Operating System

• Windows
• macOS
• Linux
• FreeBSD
• OpenBSD
• Android
• iOS
• Nintendo Switch
• PlayStation 5
• Xbox
• Web Browsers

What feature would you like to be added?

I may want to call the following code in DrawFinalScreen that I have implemented in my Game.

https://github.com/hajimehoshi/ebiten/blob/v2.8.1/gameforui.go#L139-L155

I would like this code to be a function and be able to call it like ebiten.DrawFinalScreenDefault(screen, offscreen, geoM).

Why is this needed?

Whether or not a filter is applied when drawing a game depends on the situation. For example, I may want to draw the Ebitengine splash screen unfiltered when the game starts up, and apply the CRT filter on the title screen and beyond.
Now Ebitengine does not allow me to call the default behavior if Game implements FinalScreenDrawer.

[hajimehoshi]

Makes sense.