C# WinForm implements mouse penetration function

C# mouse penetration function (WinForm)

During WinForm development, such a scenario will be used to add a watermark logo to the screen, but it will not affect the operation of the screen. The mouse penetration function will be used here.

function

To implement the mouse penetration function, several functions need to be used: SetWindowLong, GetWindowLong, and SetLayeredWindowAttributes.

SetWindowLong

Syntax Rules

LONG SetWindowLongA(
  [in] HWND hWnd,
  [in] int  nIndex,
  [in] LONG dwNewLong
);

describe: Change the properties of the specified window. The function also sets the 32-bit (long) value of the specified offset to additional window memory.

The value of nIndex is as follows, and the commonly used value isGWL_EXSTYLE=(-20) andGWL_STYLE=(-16)

Return value：Long

If the function succeeds, the return value is the previous value of the specified 32-bit integer.

If the function fails, the return value is zero. To get more error information, call GetLastError.

If the previous value of the specified 32-bit integer is zero and the function succeeds, the return value is zero, but the function does not clear the last error message. This makes it difficult to determine success or failure. To handle this, you should clear the last error message by calling SetLastError 0 before calling SetWindowLong. The function failure will then be indicated as non-zero by the return value zero and the GetLastError result.

No judgment is made at present

GetWindowLong

Syntax Rules

LONG GetWindowLongA(
  [in] HWND hWnd,
  [in] int  nIndex
);

describe：

Retrieve information about the specified window. This function also retrieves 32 bits (DWORD) Specifies the value of the offset to the extra window memory.

The value of nIndex is as follows, and the commonly used value isGWL_EXSTYLE=(-20) andGWL_STYLE=(-16)

Return value

Type: LONG

If the function succeeds, the return value is the requested value.

If the function fails, the return value is zero. To get more error information, call GetLastError.

If SetWindowLong has not been called before, GetWindowLong returns zero for an extra window or class memory value.

SetLayeredWindowAttributes

Syntax Rules

BOOL SetLayeredWindowAttributes(
  [in] HWND     hwnd, 
  [in] COLORREF crKey,
  [in] BYTE     bAlpha,
  [in] DWORD    dwFlags
);

describe: Set the opacity and transparency color keys of the layered window.

The second is a transparent color to be set, and the third is the transparency to be set. The range of bAlpha is 0-255. If it is 0, it is completely transparent. If it is 255, it is completely opaque. The fourth parameter is whether the setting is transparent according to the transparent color or according to the bAlpha. Or both are set. If LWA_COLORKEY is set in dwFlags, then crKey will work, and all crKey color areas in the window will be transparent. If LWA_ALPHA is set in dwFlags, then bAlpha will work, and the entire window will be transparent according to the value of bAlpha. You can also set these two together to achieve these two effects at the same time.

Function code

using System;
using ;
using ;
using ;
using ;
using ;
using ;
using ;
using ;
using ;

namespace demo189_Form Move
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        //Define parameter value        private const uint WS_EX_LAYERED = 0x80000;
        private const int WS_EX_TRANSPARENT = 0x20;
        private const int GWL_STYLE = (-16);
        private const int GWL_EXSTYLE = (-20);
        private const int LWA_ALPHA = 0;

        //Change the properties of the specified window        [DllImport("user32", EntryPoint = "SetWindowLong")]
        private static extern uint SetWindowLong(IntPtr hwnd,int nIndex,uint dwNewLong
        );
        //Retrieve information about the specified window        [DllImport("user32", EntryPoint = "GetWindowLong")]
        private static extern uint GetWindowLong(IntPtr hwnd,int nIndex
        );
        //Set the opacity and transparency color keys of the layered window        [DllImport("user32", EntryPoint = "SetLayeredWindowAttributes")]
        private static extern int SetLayeredWindowAttributes(IntPtr hwnd,int crKey,int bAlpha,int dwFlags
        );

        /// <summary> 
        /// Set the form to have a mouse penetration effect        /// </summary> 
        public void SetPenetrate()
        {
             = true;
           //GetWindowLong(, GWL_EXSTYLE);
            SetWindowLong(, GWL_EXSTYLE, WS_EX_TRANSPARENT | WS_EX_LAYERED);
            SetLayeredWindowAttributes(m_hWnd,0,(BYTE)220,LWA_ALPHA);
           //SetLayeredWindowAttributes(m_hWnd,RGB(255,0,255),(BYTE)220,LWA_ALPHA|LWA_COLORKEY);
            //SetLayeredWindowAttributes(m_hWnd,RGB(0,255,0),0,LWA_COLORKEY);
        }
        private void Form1_Load(object sender, EventArgs e)
        {
             = 0.7;
            SetPenetrate();
        }
    }
}

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