Method Eval

source/script.cpp:10659–10720

Evaluate an #HotIf expression or callback function. This is called by MainWindowProc when it receives an AHK_HOT_IF_EVAL message.

// Evaluate an #HotIf expression or callback function.
// This is called by MainWindowProc when it receives an AHK_HOT_IF_EVAL message.
ResultType HotkeyCriterion::Eval(LPTSTR aHotkeyName)
{
	// Initialize a new quasi-thread to evaluate the expression. This may not be necessary for simple
	// expressions, but expressions which call user-defined functions may otherwise interfere with
	// whatever quasi-thread is running when the hook thread requests that this expression be evaluated.
	
	// Based on parts of MsgMonitor(). See there for comments.

	if (g_nThreads >= g_MaxThreadsTotal)
		return CONDITION_FALSE;

	bool prev_defer_messages = g_DeferMessagesForUnderlyingPump;
	// Force the use of PeekMessage() within MsgSleep() since GetMessage() is known to stall while
	// the system is waiting for our keyboard hook to return (last confirmed on Windows 10.0.18356).
	// This might relate to WM_TIMER being lower priority than the input hardware processing
	// performed by GetMessage().  MsgSleep() relies on WM_TIMER acting as a timeout for GetMessage().
	g_DeferMessagesForUnderlyingPump = true;

	// See MsgSleep() for comments about the following section.
	// Critical seems to improve reliability, either because the thread completes faster (i.e. before the timeout) or because we check for messages less often.
	InitNewThread(0, false, true, true);
	ResultType result;

	// Let HotIf default to the criterion currently being evaluated, in case Hotkey() is called.
	g->HotCriterion = this;

	// Update A_ThisHotkey, useful if #HotIf calls a function to do its dirty work.
	LPTSTR prior_hotkey_name[] = { g_script.mThisHotkeyName, g_script.mPriorHotkeyName };
	DWORD prior_hotkey_time[] = { g_script.mThisHotkeyStartTime, g_script.mPriorHotkeyStartTime };
	g_script.mPriorHotkeyName = g_script.mThisHotkeyName;			// For consistency
	g_script.mPriorHotkeyStartTime = g_script.mThisHotkeyStartTime; //
	g_script.mThisHotkeyName = aHotkeyName;
	g_script.mThisHotkeyStartTime = // Updated for consistency.
	g_script.mLastPeekTime = GetTickCount();

	// CALL THE CALLBACK
	ExprTokenType param = aHotkeyName;
	__int64 retval;
	result = IObjectPtr(Callback)->ExecuteInNewThread(_T("#HotIf"), &param, 1, &retval);
	if (result != FAIL)
		result = retval ? CONDITION_TRUE : CONDITION_FALSE;
	

	// The following allows the expression to set the Last Found Window for the
	// hotkey function.
	// There may be some rare cases where the wrong hotkey gets this HWND (perhaps
	// if there are multiple hotkey messages in the queue), but there doesn't seem
	// to be any easy way around that.
	g_HotExprLFW = g->hWndLastUsed; // Even if above failed, for simplicity.

	// A_ThisHotkey must be restored else A_PriorHotkey will get an incorrect value later.
	g_script.mThisHotkeyName = prior_hotkey_name[0];
	g_script.mThisHotkeyStartTime = prior_hotkey_time[0];
	g_script.mPriorHotkeyName = prior_hotkey_name[1];
	g_script.mPriorHotkeyStartTime = prior_hotkey_time[1];

	ResumeUnderlyingThread();