Final Modern UI – Aero Snap Window, Resizing, Sliding Menu – C#, WinForms

Fields

   //Fields
    private int borderSize = 2;
    private Size formSize; //Keep form size when it is minimized and restored.Since the form is resized because it takes into account the size of the title bar and borders.

Constructor

    //Constructor
    public Form1()
    {
        InitializeComponent();
        CollapseMenu();
        this.Padding = new Padding(borderSize);//Border size
        this.BackColor = Color.FromArgb(98, 102, 244);//Border color
    }

Drag Form

    //Drag Form
    [DllImport("user32.DLL", EntryPoint = "ReleaseCapture")]
    private extern static void ReleaseCapture();

    [DllImport("user32.DLL", EntryPoint = "SendMessage")]
    private extern static void SendMessage(System.IntPtr hWnd, int wMsg, int wParam, int lParam);

    private void panelTitleBar_MouseDown(object sender, MouseEventArgs e)
    {
        ReleaseCapture();
        SendMessage(this.Handle, 0x112, 0xf012, 0);
    }

Overridden methods

    //Overridden methods
    protected override void WndProc(ref Message m)
    {
        const int WM_NCCALCSIZE = 0x0083;//Standar Title Bar - Snap Window
        const int WM_SYSCOMMAND = 0x0112; 
        const int SC_MINIMIZE = 0xF020; //Minimize form (Before)
        const int SC_RESTORE = 0xF120; //Restore form (Before)
        const int WM_NCHITTEST = 0x0084;//Win32, Mouse Input Notification: Determine what part of the window corresponds to a point, allows to resize the form.
        const int resizeAreaSize = 10;

        #region Form Resize
        // Resize/WM_NCHITTEST values
        const int HTCLIENT = 1; //Represents the client area of the window
        const int HTLEFT = 10;  //Left border of a window, allows resize horizontally to the left
        const int HTRIGHT = 11; //Right border of a window, allows resize horizontally to the right
        const int HTTOP = 12;   //Upper-horizontal border of a window, allows resize vertically up
        const int HTTOPLEFT = 13;//Upper-left corner of a window border, allows resize diagonally to the left
        const int HTTOPRIGHT = 14;//Upper-right corner of a window border, allows resize diagonally to the right
        const int HTBOTTOM = 15; //Lower-horizontal border of a window, allows resize vertically down
        const int HTBOTTOMLEFT = 16;//Lower-left corner of a window border, allows resize diagonally to the left
        const int HTBOTTOMRIGHT = 17;//Lower-right corner of a window border, allows resize diagonally to the right

        ///<Doc> More Information: https://docs.microsoft.com/en-us/windows/win32/inputdev/wm-nchittest </Doc>

        if (m.Msg == WM_NCHITTEST)
        { //If the windows m is WM_NCHITTEST
            base.WndProc(ref m);
            if (this.WindowState == FormWindowState.Normal)//Resize the form if it is in normal state
            {
                if ((int)m.Result == HTCLIENT)//If the result of the m (mouse pointer) is in the client area of the window
                {
                    Point screenPoint = new Point(m.LParam.ToInt32()); //Gets screen point coordinates(X and Y coordinate of the pointer)                           
                    Point clientPoint = this.PointToClient(screenPoint); //Computes the location of the screen point into client coordinates                          

                    if (clientPoint.Y <= resizeAreaSize)//If the pointer is at the top of the form (within the resize area- X coordinate)
                    {
                        if (clientPoint.X <= resizeAreaSize) //If the pointer is at the coordinate X=0 or less than the resizing area(X=10) in 
                            m.Result = (IntPtr)HTTOPLEFT; //Resize diagonally to the left
                        else if (clientPoint.X < (this.Size.Width - resizeAreaSize))//If the pointer is at the coordinate X=11 or less than the width of the form(X=Form.Width-resizeArea)
                            m.Result = (IntPtr)HTTOP; //Resize vertically up
                        else //Resize diagonally to the right
                            m.Result = (IntPtr)HTTOPRIGHT;
                    }
                    else if (clientPoint.Y <= (this.Size.Height - resizeAreaSize)) //If the pointer is inside the form at the Y coordinate(discounting the resize area size)
                    {
                        if (clientPoint.X <= resizeAreaSize)//Resize horizontally to the left
                            m.Result = (IntPtr)HTLEFT;
                        else if (clientPoint.X > (this.Width - resizeAreaSize))//Resize horizontally to the right
                            m.Result = (IntPtr)HTRIGHT;
                    }
                    else
                    {
                        if (clientPoint.X <= resizeAreaSize)//Resize diagonally to the left
                            m.Result = (IntPtr)HTBOTTOMLEFT;
                        else if (clientPoint.X < (this.Size.Width - resizeAreaSize)) //Resize vertically down
                            m.Result = (IntPtr)HTBOTTOM;
                        else //Resize diagonally to the right
                            m.Result = (IntPtr)HTBOTTOMRIGHT;
                    }
                }
            }
            return;
        }
        #endregion

        //Remove border and keep snap window
        if (m.Msg == WM_NCCALCSIZE && m.WParam.ToInt32() == 1)
        {
            return;
        }

        //Keep form size when it is minimized and restored. Since the form is resized because it takes into account the size of the title bar and borders.
        if (m.Msg == WM_SYSCOMMAND)
        {
            /// <see cref="https://docs.microsoft.com/en-us/windows/win32/menurc/wm-syscommand"/>
            /// Quote:
            /// In WM_SYSCOMMAND messages, the four low - order bits of the wParam parameter 
            /// are used internally by the system.To obtain the correct result when testing 
            /// the value of wParam, an application must combine the value 0xFFF0 with the 
            /// wParam value by using the bitwise AND operator.
            int wParam = (m.WParam.ToInt32() & 0xFFF0);               

            if (wParam == SC_MINIMIZE)  //Before
                formSize = this.ClientSize;
            if (wParam == SC_RESTORE)// Restored form(Before)
                this.Size = formSize;
        }
        base.WndProc(ref m);
    }  

Private methods

    //Private methods
    private void AdjustForm()
    {
        switch (this.WindowState)
        {
            case FormWindowState.Maximized: //Maximized form (After)
                this.Padding = new Padding(8, 8, 8, 0);
                break;
            case FormWindowState.Normal: //Restored form (After)
                if (this.Padding.Top != borderSize)
                    this.Padding = new Padding(borderSize);
                break; 
        }
    }

    private void CollapseMenu()
    {
        if (this.panelMenu.Width > 200) //Collapse menu
        {
            panelMenu.Width = 100;
            pictureBox1.Visible = false;
            btnMenu.Dock = DockStyle.Top;
            foreach (Button menuButton in panelMenu.Controls.OfType<Button>())
            {
                menuButton.Text = "";
                menuButton.ImageAlign = ContentAlignment.MiddleCenter;
                menuButton.Padding = new Padding(0);
            }
        }
        else
        { //Expand menu
            panelMenu.Width = 230;
            pictureBox1.Visible = true;
            btnMenu.Dock = DockStyle.None;
            foreach (Button menuButton in panelMenu.Controls.OfType<Button>())
            {
                menuButton.Text = "   " + menuButton.Tag.ToString();
                menuButton.ImageAlign = ContentAlignment.MiddleLeft;
                menuButton.Padding = new Padding(10, 0, 0, 0);
            }
        }
    }

Event methods

    //Event methods
    private void Form1_Resize(object sender, EventArgs e)
    {
        AdjustForm();
    }

    private void btnMenu_Click(object sender, EventArgs e)
    {
        CollapseMenu();
    }

    private void btnMinimize_Click(object sender, EventArgs e)
    {
        this.WindowState = FormWindowState.Minimized;
    }

    private void btnMaximize_Click(object sender, EventArgs e)
    {
        if (this.WindowState == FormWindowState.Normal)
        {
            formSize = this.ClientSize;
            this.WindowState = FormWindowState.Maximized;
        }
        else
        {
            this.WindowState = FormWindowState.Normal;
            this.Size = formSize;
        }
    }

    private void btnClose_Click(object sender, EventArgs e)
    {
        Application.Exit();
    }

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