Function LowLevelMouseProc

source/hook.cpp:228–297

LRESULT CALLBACK LowLevelMouseProc(int aCode, WPARAM wParam, LPARAM lParam)
{
	// code != HC_ACTION should be evaluated PRIOR to considering the values
	// of wParam and lParam, because those values may be invalid or untrustworthy
	// whenever code < 0.
	if (aCode != HC_ACTION)
		return CallNextHookEx(g_MouseHook, aCode, wParam, lParam);

	MSLLHOOKSTRUCT &event = *(PMSLLHOOKSTRUCT)lParam;  // For convenience, maintainability, and possibly performance.

	// Make all mouse events physical to try to simulate mouse clicks in games that normally ignore
	// artificial input.
	//event.flags &= ~LLMHF_INJECTED;

	if (!(event.flags & LLMHF_INJECTED)) // Physical mouse movement or button action (uses LLMHF vs. LLKHF).
		g_TimeLastInputPhysical = g_TimeLastInputMouse = GetTickCount();
		// Above: Don't use event.time, mostly because SendInput can produce invalid timestamps on such events
		// (though in truth, that concern isn't valid because SendInput's input isn't marked as physical).
		// Another concern is the comments at the other update of "g_TimeLastInputPhysical" elsewhere in this file.
		// A final concern is that some drivers might be faulty and might not generate an accurate timestamp.

	if (wParam == WM_MOUSEMOVE) // Only after updating for physical input, above, is this checked.
		return (g_BlockMouseMove && !(event.flags & LLMHF_INJECTED)) ? 1 : CallNextHookEx(g_MouseHook, aCode, wParam, lParam);
		// Above: In v1.0.43.11, a new mode was added to block mouse movement only since it's more flexible than
		// BlockInput (which keybd too, and blocks all mouse buttons too).  However, this mode blocks only
		// physical mouse movement because it seems most flexible (and simplest) to allow all artificial
		// movement, even if that movement came from a source other than an AHK script (such as some other
		// macro program).

	// MSDN: WM_LBUTTONDOWN, WM_LBUTTONUP, WM_MOUSEMOVE, WM_MOUSEWHEEL [, WM_MOUSEHWHEEL], WM_RBUTTONDOWN, or WM_RBUTTONUP.
	// But what about the middle button?  It's undocumented, but it is received.
	// What about doubleclicks (e.g. WM_LBUTTONDBLCLK): I checked: They are NOT received.
	// This is expected because each click in a doubleclick could be separately suppressed by
	// the hook, which would make it become a non-doubleclick.
	vk_type vk = 0;
	sc_type sc = 0; // To be overridden if this even is a wheel turn.
	short wheel_delta;
	bool key_up = true;  // Set default to safest value.

	switch (wParam)
	{
		case WM_MOUSEWHEEL:
		case WM_MOUSEHWHEEL: // v1.0.48: Lexikos: Support horizontal scrolling in Windows Vista and later.
			// MSDN: "A positive value indicates that the wheel was rotated forward, away from the user;
			// a negative value indicates that the wheel was rotated backward, toward the user. One wheel
			// click is defined as WHEEL_DELTA, which is 120."  Testing shows that on XP at least, the
			// abs(delta) is greater than 120 when the user turns the wheel quickly (also depends on
			// granularity of wheel hardware); i.e. the system combines multiple turns into a single event.
			wheel_delta = GET_WHEEL_DELTA_WPARAM(event.mouseData); // Must typecast to short (not int) via macro, otherwise the conversion to negative/positive number won't be correct.
			if (wParam == WM_MOUSEWHEEL)
				vk = wheel_delta < 0 ? VK_WHEEL_DOWN : VK_WHEEL_UP;
			else
				vk = wheel_delta < 0 ? VK_WHEEL_LEFT : VK_WHEEL_RIGHT;
			sc = (wheel_delta > 0 ? wheel_delta : -wheel_delta); // Note that sc is unsigned.
			key_up = false; // Always consider wheel movements to be "key down" events.
			break;
		case WM_LBUTTONUP: vk = VK_LBUTTON;	break;
		case WM_RBUTTONUP: vk = VK_RBUTTON; break;