Fix Window light theme detection being backwards

[Insprill]

In the Windows backend, when dark mode was enabled, should_use_light_theme would return true, and vice-versa. This caused the title bar's color to be the opposite of the system theme. This fixes that behavior so the title bar matches the system theme.

[xStrom]

This doesn't seem right to me. I'm using the dark theme and that registry value is 0 for me.

Are you claiming that if the AppsUseLightTheme property in registry is 0 then apps should use the light theme, and when it is 1 they should not use the light theme?

If so, does this match the registry value you see on your setup?

[Insprill]

Apologies, after looking at it again, it's where the theme is set that's backward. DWMWA_USE_IMMERSIVE_DARK_MODE sets whether dark mode should be used, however, the value of the registry key was being passed in which states whether light mode should be used. I've renamed the function to should_use_dark_theme to match the change in return value.

[xStrom]

Aha, that does seem like a bug. I confirmed that this fixes the issue. 🎉

Thanks!