c#透明TextBox

在 http://www.codeproject.com/KB/edit/AlphaBlendedTextControls.aspx 的基础上增加了水印文字

代码如下：

  public class TextBoxTransparent : TextBoxEx
     {
         #region private variables

         private uPictureBox myPictureBox;
         private bool myUpToDate = false;
         private bool myCaretUpToDate = false;
         private Bitmap myBitmap;
         private Bitmap myAlphaBitmap;

         private int myFontHeight = ;

         private System.Windows.Forms.Timer myTimer1;

         private bool myCaretState = true;

         private bool myPaintedFirstTime = false;

         private Color myBackColor = Color.White;
         private int myBackAlpha = ;

         /// <summary>
         /// Required designer variable.
         /// </summary>
         private System.ComponentModel.Container components = null;

         #endregion // end private variables

         #region public methods and overrides

         public TextBoxTransparent()
         {
             // This call is required by the Windows.Forms Form Designer.
             InitializeComponent();
             // TODO: Add any initialization after the InitializeComponent call

             this.BackColor = myBackColor;

             this.SetStyle(ControlStyles.UserPaint, false);
             this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
             this.SetStyle(ControlStyles.DoubleBuffer, true);

             myPictureBox = new uPictureBox();
             this.Controls.Add(myPictureBox);
             myPictureBox.Dock = DockStyle.Fill;
         }

         protected override void OnResize(EventArgs e)
         {

             base.OnResize(e);
             this.myBitmap = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height);//(this.Width,this.Height);
             this.myAlphaBitmap = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height);//(this.Width,this.Height);
             myUpToDate = false;
             this.Invalidate();
         }

         //Some of these should be moved to the WndProc later

         protected override void OnKeyDown(KeyEventArgs e)
         {
             base.OnKeyDown(e);
             myUpToDate = false;
             this.Invalidate();
         }

         protected override void OnKeyUp(KeyEventArgs e)
         {
             base.OnKeyUp(e);
             myUpToDate = false;
             this.Invalidate();

         }

         protected override void OnKeyPress(KeyPressEventArgs e)
         {
             base.OnKeyPress(e);
             myUpToDate = false;
             this.Invalidate();
         }

         protected override void OnMouseUp(MouseEventArgs e)
         {
             base.OnMouseUp(e);
             this.Invalidate();
         }

         protected override void OnGiveFeedback(GiveFeedbackEventArgs gfbevent)
         {
             base.OnGiveFeedback(gfbevent);
             myUpToDate = false;
             this.Invalidate();
         }

         protected override void OnMouseLeave(EventArgs e)
         {
             //found this code to find the current cursor location
             //at http://www.syncfusion.com/FAQ/WinForms/FAQ_c50c.asp#q597q

             Point ptCursor = Cursor.Position;

             Form f = this.FindForm();
             ptCursor = f.PointToClient(ptCursor);
             if (!this.Bounds.Contains(ptCursor))
                 base.OnMouseLeave(e);
         }

         protected override void OnChangeUICues(UICuesEventArgs e)
         {
             base.OnChangeUICues(e);
             myUpToDate = false;
             this.Invalidate();
         }

         //--
         protected override void OnGotFocus(EventArgs e)
         {
             base.OnGotFocus(e);
             myCaretUpToDate = false;
             myUpToDate = false;
             this.Invalidate();

             myTimer1 = new System.Windows.Forms.Timer(this.components);
             myTimer1.Interval = (int)win32.GetCaretBlinkTime(); //  usually around 500;

             myTimer1.Tick += new EventHandler(myTimer1_Tick);
             myTimer1.Enabled = true;

         }

         protected override void OnLostFocus(EventArgs e)
         {
             base.OnLostFocus(e);
             myCaretUpToDate = false;
             myUpToDate = false;
             this.Invalidate();

             myTimer1.Dispose();
         }

         //--        

         protected override void OnFontChanged(EventArgs e)
         {
             if (this.myPaintedFirstTime)
                 this.SetStyle(ControlStyles.UserPaint, false);

             base.OnFontChanged(e);

             if (this.myPaintedFirstTime)
                 this.SetStyle(ControlStyles.UserPaint, true);

             myFontHeight = GetFontHeight();

             myUpToDate = false;
             this.Invalidate();
         }

         protected override void OnTextChanged(EventArgs e)
         {
             base.OnTextChanged(e);
             myUpToDate = false;
             this.Invalidate();
         }

         protected override void WndProc(ref Message m)
         {

             base.WndProc(ref m);

             // need to rewrite as a big switch

             if (m.Msg == win32.WM_PAINT)
             {

                 myPaintedFirstTime = true;

                 if (!myUpToDate || !myCaretUpToDate)
                     GetBitmaps();
                 myUpToDate = true;
                 myCaretUpToDate = true;

                 if (myPictureBox.Image != null) myPictureBox.Image.Dispose();

                 if (string.IsNullOrEmpty(this.Text) && !string.IsNullOrEmpty(this.PromptText))
                 {
                     Bitmap bit = (Bitmap)myAlphaBitmap.Clone();
                     Graphics g = Graphics.FromImage(bit);
                     SizeF sizet1 = g.MeasureString(this.PromptText, this.PromptFont);
                     g.DrawString(this.PromptText, this.PromptFont, new SolidBrush(PromptColor), new PointF(, (bit.Height - sizet1.Height) / ));
                     g.Dispose();
                     myPictureBox.Image = bit;
                 }
                 else
                 {
                     myPictureBox.Image = (Image)myAlphaBitmap.Clone();
                 }
             }

             else if (m.Msg == win32.WM_HSCROLL || m.Msg == win32.WM_VSCROLL)
             {
                 myUpToDate = false;
                 this.Invalidate();
             }

             else if (m.Msg == win32.WM_LBUTTONDOWN
                 || m.Msg == win32.WM_RBUTTONDOWN
                 || m.Msg == win32.WM_LBUTTONDBLCLK
                 //  || m.Msg == win32.WM_MOUSELEAVE  ///****
                 )
             {
                 myUpToDate = false;
                 this.Invalidate();
             }

             else if (m.Msg == win32.WM_MOUSEMOVE)
             {
                 if (m.WParam.ToInt32() != )  //shift key or other buttons
                 {
                     myUpToDate = false;
                     this.Invalidate();
                 }
             }

             if (m.Msg ==  || m.Msg ==  || m.Msg == )
             {
                 base.OnPaint(null);
             }

             //System.Diagnostics.Debug.WriteLine("Pro: " + m.Msg.ToString("X"));

         }

         /// <summary>
         /// Clean up any resources being used.
         /// </summary>
         protected override void Dispose(bool disposing)
         {
             if (disposing)
             {
                 //this.BackColor = Color.Pink;
                 if (components != null)
                 {
                     components.Dispose();
                 }
             }
             base.Dispose(disposing);
         }

         #endregion        //end public method and overrides

         #region public property overrides

         public new BorderStyle BorderStyle
         {
             get { return base.BorderStyle; }
             set
             {
                 if (this.myPaintedFirstTime)
                     this.SetStyle(ControlStyles.UserPaint, false);

                 base.BorderStyle = value;

                 if (this.myPaintedFirstTime)
                     this.SetStyle(ControlStyles.UserPaint, true);

                 this.myBitmap = null;
                 this.myAlphaBitmap = null;
                 myUpToDate = false;
                 this.Invalidate();
             }
         }

         public new Color BackColor
         {
             get
             {
                 return Color.FromArgb(base.BackColor.R, base.BackColor.G, base.BackColor.B);
             }
             set
             {
                 myBackColor = value;
                 base.BackColor = value;
                 myUpToDate = false;
             }
         }
         public override bool Multiline
         {
             get { return base.Multiline; }
             set
             {
                 if (this.myPaintedFirstTime)
                     this.SetStyle(ControlStyles.UserPaint, false);

                 base.Multiline = value;

                 if (this.myPaintedFirstTime)
                     this.SetStyle(ControlStyles.UserPaint, true);

                 this.myBitmap = null;
                 this.myAlphaBitmap = null;
                 myUpToDate = false;
                 this.Invalidate();
             }
         }

         #endregion    //end public property overrides

         #region private functions and classes

         private int GetFontHeight()
         {
             Graphics g = this.CreateGraphics();
             SizeF sf_font = g.MeasureString("X", this.Font);
             g.Dispose();
             return (int)sf_font.Height;
         }

         private void GetBitmaps()
         {

             if (myBitmap == null
                 || myAlphaBitmap == null
                 || myBitmap.Width != Width
                 || myBitmap.Height != Height
                 || myAlphaBitmap.Width != Width
                 || myAlphaBitmap.Height != Height)
             {
                 myBitmap = null;
                 myAlphaBitmap = null;
             }

             if (myBitmap == null)
             {
                 myBitmap = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height);//(Width,Height);
                 myUpToDate = false;
             }

             if (!myUpToDate)
             {
                 //Capture the TextBox control window

                 this.SetStyle(ControlStyles.UserPaint, false);

                 win32.CaptureWindow(this, ref myBitmap);

                 this.SetStyle(ControlStyles.UserPaint, true);
                 this.SetStyle(ControlStyles.SupportsTransparentBackColor, true);
                 this.BackColor = Color.FromArgb(myBackAlpha, myBackColor);

             }
             //--

             Rectangle r2 = new Rectangle(, , this.ClientRectangle.Width, this.ClientRectangle.Height);
             ImageAttributes tempImageAttr = new ImageAttributes();

             //Found the color map code in the MS Help

             ColorMap[] tempColorMap = new ColorMap[];
             tempColorMap[] = new ColorMap();
             tempColorMap[].OldColor = Color.FromArgb(, myBackColor);
             tempColorMap[].NewColor = Color.FromArgb(myBackAlpha, myBackColor);

             tempImageAttr.SetRemapTable(tempColorMap);

             if (myAlphaBitmap != null)
                 myAlphaBitmap.Dispose();

             myAlphaBitmap = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height);//(Width,Height);

             Graphics tempGraphics1 = Graphics.FromImage(myAlphaBitmap);

             tempGraphics1.DrawImage(myBitmap, r2, , , this.ClientRectangle.Width, this.ClientRectangle.Height, GraphicsUnit.Pixel, tempImageAttr);

             tempGraphics1.Dispose();

             //----

             if (this.Focused && (this.SelectionLength == ))
             {
                 Graphics tempGraphics2 = Graphics.FromImage(myAlphaBitmap);
                 if (myCaretState)
                 {
                     //Draw the caret
                     Point caret = this.findCaret();
                     Pen p = new Pen(this.ForeColor, );
                     tempGraphics2.DrawLine(p, caret.X+, caret.Y + , caret.X+, caret.Y + myFontHeight);
                     tempGraphics2.Dispose();
                 }

             }

         }

         private Point findCaret()
         {
             /*  Find the caret translated from code at
              * http://www.vb-helper.com/howto_track_textbox_caret.html
              *
              * and
              *
              * http://www.microbion.co.uk/developers/csharp/textpos2.htm
              *
              * Changed to EM_POSFROMCHAR
              *
              * This code still needs to be cleaned up and debugged
              * */

             Point pointCaret = new Point();
             int i_char_loc = this.SelectionStart;
             IntPtr pi_char_loc = new IntPtr(i_char_loc);

             int i_point = win32.SendMessage(this.Handle, win32.EM_POSFROMCHAR, pi_char_loc, IntPtr.Zero);
             pointCaret = new Point(i_point);

             if (i_char_loc == )
             {
                 pointCaret = new Point();
             }
             else if (i_char_loc >= this.Text.Length)
             {
                 pi_char_loc = new IntPtr(i_char_loc - );
                 i_point = win32.SendMessage(this.Handle, win32.EM_POSFROMCHAR, pi_char_loc, IntPtr.Zero);
                 pointCaret = new Point(i_point);

                 Graphics g = this.CreateGraphics();
                 String t1 = this.Text.Substring(this.Text.Length - , ) + "X";
                 SizeF sizet1 = g.MeasureString(t1, this.Font);
                 SizeF sizex = g.MeasureString("X", this.Font);
                 g.Dispose();
                 int xoffset = (int)(sizet1.Width - sizex.Width);
                 pointCaret.X = pointCaret.X + xoffset;

                 if (i_char_loc == this.Text.Length)
                 {
                     String slast = this.Text.Substring(Text.Length - , );
                     if (slast == "\n")
                     {
                         pointCaret.X = ;
                         pointCaret.Y = pointCaret.Y + myFontHeight;
                     }
                 }

             }

             return pointCaret;
         }

         private void myTimer1_Tick(object sender, EventArgs e)
         {
             //Timer used to turn caret on and off for focused control

             myCaretState = !myCaretState;
             myCaretUpToDate = false;
             this.Invalidate();
         }

         private class uPictureBox : PictureBox
         {
             public uPictureBox()
             {
                 this.SetStyle(ControlStyles.Selectable, false);
                 this.SetStyle(ControlStyles.UserPaint, true);
                 this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
                 this.SetStyle(ControlStyles.DoubleBuffer, true);

                 this.Cursor = null;
                 this.Enabled = true;
                 this.SizeMode = PictureBoxSizeMode.Normal;

             }

             //uPictureBox
             protected override void WndProc(ref Message m)
             {
                 if (m.Msg == win32.WM_LBUTTONDOWN
                     || m.Msg == win32.WM_RBUTTONDOWN
                     || m.Msg == win32.WM_LBUTTONDBLCLK
                     || m.Msg == win32.WM_MOUSELEAVE
                     || m.Msg == win32.WM_MOUSEMOVE)
                 {
                     //Send the above messages back to the parent control
                     win32.PostMessage(this.Parent.Handle, (uint)m.Msg, m.WParam, m.LParam);
                 }

                 else if (m.Msg == win32.WM_LBUTTONUP)
                 {
                     //??  for selects and such
                     this.Parent.Invalidate();
                 }

                 base.WndProc(ref m);
             }

         }   // End uPictureBox Class

         #endregion  // end private functions and classes

         #region Component Designer generated code
         /// <summary>
         /// Required method for Designer support - do not modify
         /// the contents of this method with the code editor.
         /// </summary>
         private void InitializeComponent()
         {
             components = new System.ComponentModel.Container();
         }
         #endregion

         #region New Public Properties

         [
         Category("Appearance"),
         Description("The alpha value used to blend the control's background. Valid values are 0 through 255."),
         Browsable(true),
         DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)

         ]
         public int BackAlpha
         {
             get { return myBackAlpha; }
             set
             {
                 int v = value;
                 if (v > )
                     v = ;
                 myBackAlpha = v;
                 myUpToDate = false;
                 Invalidate();
             }
         }

         #endregion

     }  // End AlphaTextBox Class 

  public class win32
     {

         public const int WM_MOUSEMOVE = 0x0200;
         public const int WM_LBUTTONDOWN = 0x0201;
         public const int WM_LBUTTONUP = 0x0202;
         public const int WM_RBUTTONDOWN = 0x0204;
         public const int WM_LBUTTONDBLCLK = 0x0203;

         public const int WM_MOUSELEAVE = 0x02A3;

         public const int WM_PAINT = 0x000F;
         public const int WM_ERASEBKGND = 0x0014;

         public const int WM_PRINT = 0x0317;

         //const int EN_HSCROLL       =   0x0601;
         //const int EN_VSCROLL       =   0x0602;

         public const int WM_HSCROLL = 0x0114;
         public const int WM_VSCROLL = 0x0115;

         public const int EM_GETSEL = 0x00B0;
         public const int EM_LINEINDEX = 0x00BB;
         public const int EM_LINEFROMCHAR = 0x00C9;

         public const int EM_POSFROMCHAR = 0x00D6;

         [DllImport("USER32.DLL", EntryPoint = "PostMessage")]
         public static extern bool PostMessage(IntPtr hwnd, uint msg,
             IntPtr wParam, IntPtr lParam);

         /*
             BOOL PostMessage(          HWND hWnd,
                 UINT Msg,
                 WPARAM wParam,
                 LPARAM lParam
                 );
         */

         // Put this declaration in your class   //IntPtr
         [DllImport("USER32.DLL", EntryPoint = "SendMessage")]
         public static extern int SendMessage(IntPtr hwnd, int msg, IntPtr wParam,
             IntPtr lParam);

         [DllImport("USER32.DLL", EntryPoint = "GetCaretBlinkTime")]
         public static extern uint GetCaretBlinkTime();

         const int WM_PRINTCLIENT = 0x0318;

         const long PRF_CHECKVISIBLE = 0x00000001L;
         const long PRF_NONCLIENT = 0x00000002L;
         const long PRF_CLIENT = 0x00000004L;
         const long PRF_ERASEBKGND = 0x00000008L;
         const long PRF_CHILDREN = 0x00000010L;
         const long PRF_OWNED = 0x00000020L;

         /*  Will clean this up later doing something like this
         enum  CaptureOptions : long
         {
             PRF_CHECKVISIBLE= 0x00000001L,
             PRF_NONCLIENT    = 0x00000002L,
             PRF_CLIENT        = 0x00000004L,
             PRF_ERASEBKGND    = 0x00000008L,
             PRF_CHILDREN    = 0x00000010L,
             PRF_OWNED        = 0x00000020L
         }
         */

         public static bool CaptureWindow(System.Windows.Forms.Control control,
                                 ref System.Drawing.Bitmap bitmap)
         {
             //This function captures the contents of a window or control

             Graphics g2 = Graphics.FromImage(bitmap);

             //PRF_CHILDREN // PRF_NONCLIENT
             int meint = (int)(PRF_CLIENT | PRF_ERASEBKGND); //| PRF_OWNED ); //  );
             System.IntPtr meptr = new System.IntPtr(meint);

             System.IntPtr hdc = g2.GetHdc();
             win32.SendMessage(control.Handle, win32.WM_PRINT, hdc, meptr);

             g2.ReleaseHdc(hdc);
             g2.Dispose();

             return true;

         }

     }

另外一个透明textbox如下 http://www.codeproject.com/KB/edit/alphablendtextbox.aspx

效果图：