CODEWITHSUNDEEP
c++windowswinapiscreenresolution
AndroidDev
AndroidDev

Reputation: 5565

The index of mouse click co-ordinates start from 0 or from 1?

In Win32 do the co-ordinates returned by GET_X_PARAM and GET_Y_PARAM calls start from 0 or from 1? If I have a screen with resolution 640X480 then what values do I get? Are they from 0 to 639 and 0 to 479? Or 1 to 640 and 1 to 480?

extern "C" LRESULT CALLBACK WindowProc (HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam)  
{  
      Switch(message)  
      {  
            case WM_MOUSEMOVE:              
                  iXPosition = GET_X_LPARAM(lParam);   
                  iYPosition = GET_Y_LPARAM(lParam);  
      }  
}

Upvotes: 0

Views: 174

Answers (2)

BrendanMcK
BrendanMcK

Reputation: 14498

For WM_MOUSEMOVE, the coordinates are relative to the window's client area, not the screen - see MSDN. Given that, the points start at 0,0 for the top-left corner of the window's client area.

Also note that if you do use an API that returns screen-based mouse coordinates, like GetCursorPos, you can get negative values back on a multi-monitor system: 0,0 is the top-left of the primary monitor, which could have a secondary monitor set above or to the left of it; so the actual desktop could 'start' at a negative or other non-0,0 value. (GetSystemMetrics(SM_XVIRTUALSCREEN) will return the left edge, for example.)

Upvotes: 5

Dabbler
Dabbler

Reputation: 9873

The value is zero-based, not one-based

Upvotes: 3

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