Description

The adaptive CRT shader always forced single-scanning in openglnb output modes which was wrong (e.g., 320x200 content always appeared single-scanned). This fix corrects that. See the updated comments block for the fixed double-scanning/pixel-doubling criteria.

The issue was reported by @SmilingSpectre and mmpp0 on the eXoDOS Discord.

Manual testing

• Commented out the debug logging at the end of log_display_properties() in sdlmain.cpp to log the actual rendered dimensions as well.
• Verified the correct double-scanning & pixel-doubling behaviour for opengl, openglnb, texture and texturenb for all VGA modes in Deluxe Paint II (both visually and by looking at the debug logs; 320x200 modes should result in 640x400 render dimensions for VGA).
• Verified that the output = opengl + glshader = none special case results in doubling for VGA modes (i.e., 640x400 render dimensions for 320x200 modes).
• Verified that the output = openglnb + glshader = none special case results in no doubling for VGA modes (i.e., 320x200 render dimensions for 320x200 modes).

Checklist

Please tick the items as you have addressed them. Don't remove items; leave the ones that are not applicable unchecked.

I have:

• followed the project's contributing guidelines and code of conduct.
• performed a self-review of my code.
• commented on the particularly hard-to-understand areas of my code.
• split my work into well-defined, bisectable commits, and I named my commits well.
• applied the appropriate labels (bug, enhancement, refactoring, documentation, etc.)
• checked that all my commits can be built.
• confirmed that my code does not cause performance regressions (e.g., by running the Quake benchmark).
• added unit tests where applicable to prove the correctness of my code and to avoid future regressions.
• made corresponding changes to the documentation or the website according to the documentation guidelines.
• locally verified my website or documentation changes.