Function KeyToModifiersLR

source/keyboard_mouse.cpp:3616–3681

modLR_type KeyToModifiersLR(vk_type aVK, sc_type aSC, bool *pIsNeutral)
// Convert the given virtual key / scan code to its equivalent bitwise modLR value.
// Callers rely upon the fact that we convert a neutral key such as VK_SHIFT into MOD_LSHIFT,
// not the bitwise combo of MOD_LSHIFT|MOD_RSHIFT.
// v1.0.43: VK_SHIFT should yield MOD_RSHIFT if the caller explicitly passed the right vs. left scan code.
// The SendPlay method relies on this to properly release AltGr, such as after "SendPlay @" in German.
// Other things may also rely on it because it is more correct.
{
	bool placeholder;
	bool &is_neutral = pIsNeutral ? *pIsNeutral : placeholder; // Simplifies other things below.
	is_neutral = false; // Set default for output parameter for caller.

	if (!(aVK || aSC))
		return 0;

	if (aVK) // Have vk take precedence over any non-zero sc.
		switch(aVK)
		{
		case VK_SHIFT:
			if (aSC == SC_RSHIFT)
				return MOD_RSHIFT;
			//else aSC is omitted (0) or SC_LSHIFT.  Either way, most callers would probably want that considered "neutral".
			is_neutral = true;
			return MOD_LSHIFT;
		case VK_LSHIFT: return MOD_LSHIFT;
		case VK_RSHIFT:	return MOD_RSHIFT;

		case VK_CONTROL:
			if (aSC == SC_RCONTROL)
				return MOD_RCONTROL;
			//else aSC is omitted (0) or SC_LCONTROL.  Either way, most callers would probably want that considered "neutral".
			is_neutral = true;
			return MOD_LCONTROL;
		case VK_LCONTROL: return MOD_LCONTROL;
		case VK_RCONTROL: return MOD_RCONTROL;

		case VK_MENU:
			if (aSC == SC_RALT)
				return MOD_RALT;
			//else aSC is omitted (0) or SC_LALT.  Either way, most callers would probably want that considered "neutral".
			is_neutral = true;
			return MOD_LALT;
		case VK_LMENU: return MOD_LALT;
		case VK_RMENU: return MOD_RALT;

		case VK_LWIN: return MOD_LWIN;
		case VK_RWIN: return MOD_RWIN;

		default:
			return 0;
		}

	// If above didn't return, rely on the scan code instead, which is now known to be non-zero.
	switch(aSC)
	{
	case SC_LSHIFT: return MOD_LSHIFT;
	case SC_RSHIFT:	return MOD_RSHIFT;
	case SC_LCONTROL: return MOD_LCONTROL;