Authentic adaptive CRT shaders #2777

…lised

Remove the super obscure "extension mechanism" where #define directives can be passed to shaders via GLSHADER_* environment variables. This is originating from the original OpenGL shader SVN patch. Most likely nobody uses this for anything and it just complicates the code for no good reason, so it's best to lose it.

Also turn 'glshader' into a string property as it can store either symbolic shader names or actual paths.

Replacing all uses of string_view with std::string in sdlmain.cpp as its use is not warranted (we're not dealing with substrings, neither anything performance sensitive, so 'const std::string&' is a simpler and more straightforward solution).

'Resources' also ignores 'contrib/resources' on case-preserving file systems (Windows and macOS).

These shaders have been a constant source of confusion because: - They're not documented -- a new user wouldn't know which one to pick based on the cryptic shader names alone. - Many of them assume a specific output resolution (e.g., 4k) and look quite bad on 1080p, but you don't know that only looking at the shader's name. - Most of them require further tweaking to get optimal results on specific output resolutions. - Most of them don't even aim to emulate the characteristics of PC monitors that are quite distinct from arcade monitors, home computer monitors, or TV sets from the 80s/early 90s. Because of the above, we are not bundling them with future DOSBox Staging releases anymore; they are replaced by the new dynamic shader system that picks the best CRT shader variant based on the graphics standard in use (CGA, EGA, VGA, etc.) and the available viewport resolution (1080p, 1440p, 4k, etc.) These SVN shader will still be available as a separate download for people who want to experiment with them.

- All shader management code has been moved from 'render.cpp' to the ShaderManager. - The 'default' shader alias to 'interpolation/sharp' has been replaced with the 'sharp' alias. - Three new adaptive (auto-switching) CRT emulation shader modes have been added: 'crt-auto', 'crt-auto-machine', and 'crt-auto-arcade'. These modes switch dynamically between CRT shader variants depending on the current video mode, the graphics adapter in use, and the viewport resolution (see the description of the 'glshader' setting for further details).

With the 'integer_scaling = auto' setting, vertical integer scaling is auto-enabled for adaptive CRT shaders only, and only if a CRT shader is actually in use, but not for the fallback 'sharp' shader.

After the double-scanning & pixel-doubling changes, a few video mode pairs became indistinguishable when only looking at the render parameters. E.g., the render dimensions of the 320x200 (standard BIOS mode 13h) and 320x400 (non-VESA Mode X variant only) modes are both 320x400, so they were considered the same by the mode-change detection logic prior to this adjustment. The solution is to include the contents of the VideoMode struct in the mode-changed criteria (in this example, that would contain the "nominal" dimensions of 320x200 and 320x400, respectively).

These have been superseded by VideoMode.to_string()

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Authentic adaptive CRT shaders #2777

Authentic adaptive CRT shaders #2777

Commits on Aug 31, 2023