Detect if mouse button is down

Question

I am new to c++ and I am trying to activate a line of code only when the left mouse button is held down. In this example, my code works but it seems that it just toggles it. When I click, it spams the H key then, when I click again, it stops.

Currently I have this code:

if ((GetKeyState(VK_LBUTTON)))
{
    keybd_event(VkKeyScan('H'),0,0,0);
    Sleep ( 30 );
}

Edit:

I have inside the function:

int WINAPI WinMain ( HINSTANCE hInst, HINSTANCE P, LPSTR CMD, int nShowCmd );

Solution 1

Use this to determine if the button is pressed.

if((GetKeyState(VK_LBUTTON) & 0x8000) != 0)

http://vcpptips.wordpress.com/tag/vk_lbutton/

Solution 2

The application can catch messages and process being sent to your window indicating a state change of any mouse button.

When the left button is pressed a

WM_LBUTTONDOWN

is sent.

When it is released

WM_LBUTTONUP

is sent.

Please read here for various messages being sent to indicate mouse events.

Solution 3

Use the below to detect left mouse button press

if(GetAsyncKeyState(VK_LBUTTON)){
   //your code controls here
 }

You can find more controls here : https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getasynckeystate

Also if the GetAsyncKeyState(VK_LBUTTON)shows a syntax error, try including winuser.h by adding #include <winuser.h> in the includes of your code.

Here is an example

if(GetKeyState(VK_LBUTTON))
    {   //finding clicked position
        HWND hWnd = FindWindowA(0,("Motion Paths"));
        ::GetWindowThreadProcessId(hWnd,&pid);
        if (hWnd) { cout << "Found" << endl;}

            POINT p;
            GetCursorPos(&p);
            if (ScreenToClient(hWnd, &p))
            {
                int mouseX = p.x;
                int mouseY = p.y;
                cout<< p.x << " "<< p.y <<endl;
            }
    }

Comments

[Jordan B]

Thanks. At first it didn't work, but after reading the comments I tried replacing the 0x80 with 0x100 and works now. From what I read its 100 because I am using 64bit.

[Jonathan Potter]

A less fiddly way is if (GetKeyState(VK_LBUTTON) < 0) { }, fwiw.

[Remy Lebeau]

0x100 is the wrong value to mask with. It needs to be 0x8000 instead. < 0 is better, though

[KeyC0de]

@RemyLebeau The & method is more fiddly but is faster.