CRT screen shaders from dosbox staging

[maximilien-noal]

https://api-docs.avaloniaui.net/docs/M_Avalonia_OpenGL_GlInterface_AttachShader

https://api-docs.avaloniaui.net/docs/M_Avalonia_OpenGL_Controls_OpenGlControlBase_OnOpenGlRender

https://github.com/AvaloniaUI/Avalonia/blob/master/src/Avalonia.OpenGL/Controls/OpenGlControlBase.cs

the shaders use GLSL, and one is used among several, depending on the host screen number of pixels (ie. 1080p, 4K, ...)

Dune especially, benefits from it.

[maximilien-noal]

https://github.com/dosbox-staging/dosbox-staging/tree/main/contrib/resources/glshaders/crt

[maximilien-noal]

https://github.com/AvaloniaUI/Avalonia/blob/7842883961d094e08e9def7f30cf32fd573179c7/samples/ControlCatalog/Pages/OpenGlPage.xaml.cs

[maximilien-noal]

DOSBox Staging both uses vertex and fragment shaders. Both are important.

It requires OpenGL ES 3.1, Avalonia seems to use that.

[maximilien-noal]

opengl usage: https://github.com/SaverinOnRails/AvaloniaMpv/blob/main/src/AvaloniaMpv/MediaControl.cs