c++ mouse click simulation code

Question

Im having trouble understanding the code bellow. and i cant fined a good explanation of it. I left comments next to the code segments i have questions for.

  void LeftClick ( )
        {  
          INPUT input = {0};

           // left down 
          input.type      = INPUT_MOUSE;
          input.mi.dwFlags  = MOUSEEVENTF_LEFTDOWN;
          ::SendInput(1,&input,sizeof(INPUT));

          // left up
          ::ZeroMemory(&input,sizeof(INPUT)); // why zeroMemory? removing this code changes nothing that i can tell
          input.type      = INPUT_MOUSE; // why reset this variable? is it not already set?

          input.mi.dwFlags  = MOUSEEVENTF_LEFTUP;
          ::SendInput(1,&input,sizeof(INPUT));
        }

i got this code at http://forums.codeguru.com/showthread.php?377394-Windows-SDK-User-Interface-How-can-I-emulate-mouse-events-in-an-application

Both of your speculations together would produce better code imo. — Qaz
– Qaz, Commented Jul 2, 2013 at 21:50

frr171 · Accepted Answer · 2013-07-02 21:21:02Z

4

The ZeroMemory function clears all the data in the struct named input - that's why the code has to reset the input.type variable.

Documentation: http://msdn.microsoft.com/en-us/library/windows/desktop/aa366920(v=vs.85).aspx

I actually took a look at some old code I wrote, and I didn't use the ZeroMemory macro at all. It's really unnecessary, since both values that are set are reset again.

answered Jul 2, 2013 at 21:21

frr171

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