Expose OS accessibility preferences?

[Semphriss]

There exists SDL_GetSystemTheme for light/dark theme; would it be good to add similar options for some accessibility settings? Some ideas based on what my OS provides: Reduced motion; high contrast; shape-based replacement for color coding (for colorblind users); preferred text/cursor scaling.

I'm suggesting this to discuss whether such features would be within the scope of SDL, but also whether those things are reasonably implementable across platforms.

[icculus]

I think most platforms can't offer this information, but if you want to play around with it, I think it'd be cool to offer it in the API.

[Semphriss]

I was curious about the feasability of this, and so far, I've found the following:

• Windows offers SystemParametersInfoA with SPI_GETCLIENTAREAANIMATION (reduced motion), SPI_GETHIGHCONTRAST and SPI_GETSCREENREADER among other options.
• For macOS, there's dagronf/DSFAppearanceManager that offers a plethora of functions, including reduced motion, high contrast and various theme-related settings.
• For GNOME, there is the D-Bus setting enable-animations on org.gnome.desktop.interface. Presumably, the other settings have a similar interface, and other desktop environments have something equivalent.
• Android has Settings.Global.WINDOW_ANIMATION_SCALE and two others. I did not yet check for other options.
• iOS has UIAccessibility.isReduceMotionEnabled and various other options (contrast, grayscale, text-to-speech, labeled tickboxes...) under the same class.

I'll try to come up with a first implementation after the system tray PR will be done.

[OrichalcumCosmonaut]

Linux also has org.freedesktop.portal.Settings, which has the colour scheme, preferred contrast, and an accent colour. Looks like it’s already being used for the colour scheme:

SDL/src/core/linux/SDL_system_theme.c

Lines 29 to 37 in 313d522

	#define PORTAL_DESTINATION "org.freedesktop.portal.Desktop"
	#define PORTAL_PATH "/org/freedesktop/portal/desktop"
	#define PORTAL_INTERFACE "org.freedesktop.portal.Settings"
	#define PORTAL_METHOD "Read"
	#define SIGNAL_INTERFACE "org.freedesktop.portal.Settings"
	#define SIGNAL_NAMESPACE "org.freedesktop.appearance"
	#define SIGNAL_NAME "SettingChanged"
	#define SIGNAL_KEY "color-scheme"