Function RegExCallout

source/script2.cpp:11920–12031

};

int RegExCallout(pcret_callout_block *cb)
{
	// It should be documented that (?C) is ignored if encountered by the hook thread,
	// which could happen if SetTitleMatchMode,Regex and "#HotIf Winactive/Exist" are used.
	// This would be a problem if the callout should affect the outcome of the match or 
	// should be called even if #HotIf WinA/E. will ultimately prevent the hotkey from firing. 
	// This is because:
	//	- The callout cannot be called from the hook thread, and therefore cannot affect
	//		the outcome of #HotIf WinA/E. when called by the hook thread.
	//	- If #HotIf WinA/E does NOT prevent the hotkey from firing, it will be reevaluated from
	//		the main thread before the hotkey is actually fired. This will allow any
	//		callouts to occur on the main thread.
	//  - By contrast, if #HotIf WinA/E DOES prevent the hotkey from firing, 
	//		#HotIf WinA/E will not be reevaluated from the main thread,
	//		so callouts cannot occur.
	if (GetCurrentThreadId() != g_MainThreadID)
		return 0;

	if (!cb->callout_data)
		return 0;
	RegExCalloutData &cd = *(RegExCalloutData *)cb->callout_data;

	auto callout_func = (IObject *)cb->user_callout;
	if (!callout_func)
	{
		Var *pcre_callout_var = g_script.FindVar(_T("pcre_callout"), 12, FINDVAR_FOR_READ); // This may be a local of the UDF which called RegExMatch/Replace().
		if (!pcre_callout_var)
			return 0; // Seems best to ignore the callout rather than aborting the match.
		callout_func = pcre_callout_var->ToObject();
		if (!callout_func)
		{
			if (!pcre_callout_var->HasContents()) // Var exists but is empty.
				return 0;
			// Could be an invalid name, or the name of a built-in function.
			cd.result_token->Error(_T("Invalid pcre_callout"));
			return PCRE_ERROR_CALLOUT;
		}
	}

	// Adjust offset to account for options, which are excluded from the regex passed to PCRE.
	cb->pattern_position += cd.options_length;
	
	// Save EventInfo to be restored when we return.
	EventInfoType EventInfo_saved = g->EventInfo;

	g->EventInfo = (EventInfoType) cb;
	
	/*
	callout_number:		should be available since callout number can be specified within (?C...).
	subject:			useful when behaviour might depend on text surrounding a capture.
	start_match:		as above. equivalent to return value of RegExMatch, so should be available somehow.
	
	pattern_position:	useful to debug regexes when combined with auto-callouts. otherwise not useful.
	next_item_length:	as above. combined 'next_item' instead of these two would be less useful as it cannot distinguish between multiple identical items, and would sometimes be empty.
	
	capture_top:		not sure if useful? helps to distinguish between empty capture and non-capture. could maybe use callout number to determine this instead.
	capture_last:		as above.