Detouring can be done for already detoured functions. Just look at Steam Overlay vs other systems that hook into Direct3D, they can coexist.

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drdexebtjl 2 hours ago | parent [-]

Any idea of how that's done? In particular, how do multiple systems synchronize the installation of their hooks?

I've made my own hooking library that lets multiple plug-ins hook the same function, but it only works decently because it has this central library synchronizing access.

	▲	apple1417 an hour ago \| parent \| next [-]
		If you use OBS, a game capture works the same way, it hooks the DirectX (or whatever API) functions to grab the rendered scene directly. It often has issues picking up overlays because there isn't really any synchronisation, just whatever made the last detour fires first. Like the sibling commit says, you can stack detours, it's only an issue for OBS if something that runs after it renders more things to the screen. There is a setting to make it pick up overlays, which works reasonably well, I'm not entirely sure how it's implemented.
	▲	quotemstr 2 hours ago \| parent \| prev [-]
		Detours rewrites instructions at the start of the detoured function. Why should it know or care whether the instructions it's overwriting happen to be ones written by a previous detour? Why would you need to synchronize?