Resolve #21494: Automatically set window scaling based on DPI

[karstenvanf]

I used a similar to solution to #6991, but modified it to include a config option that flags whether the DPI has been checked instead of setting an invalid scaling factor. If the DPI check returns an error, it does not change from the default of 1.

[Gymnasiast]

@karstenvanf Could you apply the requested changes?

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[github-actions]

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[AaronVanGeffen]

I've rebased and updated this PR. The initial implementation used SDL_GetDisplayDPI, which was producing unreliable results on macOS, and apparently is also discouraged by SDL.

Instead, I've changed the implementation to use SDL_GetWindowSize and SDL_GetRendererOutputSize instead, as recommended by SDL. This infers the scaling ratio from the actual canvas size vs the one requested. This appears to work well for me.

Could someone test this works as expected on Windows as well?

[Basssiiie]

Tested it on Windows 10 64-bit, regular DPI setup and I get this at launch:

crash.zip

Error: The thread tried to divide an integer value by an integer divisor of zero.

Top of the stack trace:

openrct2.com!OpenGLDrawingContext::CalculcateClipping(DrawPixelInfo & dpi) Line 1087
	at D:\a\OpenRCT2\OpenRCT2\src\openrct2-ui\drawing\engines\opengl\OpenGLDrawingEngine.cpp(1087)
openrct2.com!OpenGLDrawingContext::Clear(DrawPixelInfo & dpi, unsigned char paletteIndex) Line 516
	at D:\a\OpenRCT2\OpenRCT2\src\openrct2-ui\drawing\engines\opengl\OpenGLDrawingEngine.cpp(516)
openrct2.com!OpenRCT2::PreloaderScene::Load() Line 51
	at D:\a\OpenRCT2\OpenRCT2\src\openrct2\scenes\preloader\PreloaderScene.cpp(51)

[AaronVanGeffen]

@Basssiiie Pushed a fix to take cases into account where SDL_GetRendererOutputSize returned an error code. Could you re-test?

[Basssiiie]

@AaronVanGeffen Tested the newest build and no crashes anymore. The game looks the same as develop now. I wonder what the returned error code was. 😅

[AaronVanGeffen]

I wonder what the returned error code was. 😅

In the current code, I can't be certain, but here's the enum from SDL_error.h:

typedef enum
{
    SDL_ENOMEM,
    SDL_EFREAD,
    SDL_EFWRITE,
    SDL_EFSEEK,
    SDL_UNSUPPORTED,
    SDL_LASTERROR
} SDL_errorcode;

I'm guessing it was returning SDL_UNSUPPORTED.