Using GDI and GDI+ mixed drawing rubber band lines

sedatkurt

3.52/5 (18 votes)

Jun 24, 2003

128244

1772

Using GDI and GDI+mixed,Rubber Band Lines in GDI+

Introduction

As every programmer knows. the easiest and fastest method to draw self erasing lines is drawing line with XOR mode. But in .NET I could not see any method that makes self erasing lines, so it forced me to use GDI and GDI+ in mixed mode. I think, using GDI+ there is no way to draw self erasing lines. I've seen some methods invented to draw self erasing lines but about all of them are using BitBlting or pushing the whole screen to buffer, and afterwards popping the buffer to erase them.

The Code

/* to be example to the xoring problem 
 * i ve written a simple namespace to referance to standat GDI.
 * But the GDIDraw namespace 
 * doesnt referance to whole methots such as drawing 
 * rectangles or other shapes
 * but can easily be enhanged if necessary */
namespace GDIDraw
{
    public enum PenStyles
    {
        PS_SOLID=0
        ,PS_DASH=1
        ,PS_DOT=2
        ,PS_DASHDOT=3
        ,PS_DASHDOTDOT=4
        ,PS_NULL=5
        ,PS_INSIDEFRAME=6
        ,PS_USERSTYLE=7
        ,PS_ALTERNATE=8
        ,PS_STYLE_MASK=0x0000000F

        ,PS_ENDCAP_ROUND=     0x00000000
        ,PS_ENDCAP_SQUARE=    0x00000100
        ,PS_ENDCAP_FLAT=      0x00000200
        ,PS_ENDCAP_MASK =     0x00000F00
        ,PS_JOIN_ROUND=       0x00000000
        ,PS_JOIN_BEVEL=       0x00001000
        ,PS_JOIN_MITER=       0x00002000
        ,PS_JOIN_MASK=        0x0000F000

        ,PS_COSMETIC=         0x00000000
        ,PS_GEOMETRIC=        0x00010000
        ,PS_TYPE_MASK=        0x000F0000
    }
    public enum drawingMode
    {
        R2_BLACK=            1   /*  0       */
        ,R2_NOTMERGEPEN=      2   /* DPon     */
        ,R2_MASKNOTPEN=       3   /* DPna     */
        ,R2_NOTCOPYPEN=       4   /* PN       */
        ,R2_MASKPENNOT=       5   /* PDna     */
        ,R2_NOT=              6   /* Dn       */
        ,R2_XORPEN=           7   /* DPx      */
        ,R2_NOTMASKPEN=       8   /* DPan     */
        ,R2_MASKPEN=          9   /* DPa      */
        ,R2_NOTXORPEN=        10  /* DPxn     */
        ,R2_NOP=              11  /* D        */
        ,R2_MERGENOTPEN=      12  /* DPno     */
        ,R2_COPYPEN=          13  /* P        */
        ,R2_MERGEPENNOT=      14  /* PDno     */
        ,R2_MERGEPEN=         15  /* DPo      */
        ,R2_WHITE=            16  /*  1       */
        ,R2_LAST=             16
    } 

    public class GDI
    {
        private IntPtr hdc;
        private System.Drawing.Graphics grp;
        
        public void BeginGDI(System.Drawing.Graphics g)
        {
            grp=g;
            hdc=grp.GetHdc();    
        }

        public void EndGDI()
        {
            grp.ReleaseHdc(hdc);
        }

        public IntPtr CreatePEN(
            PenStyles fnPenStyle,    // pen style
            int nWidth,        // pen width
            int crColor   // pen color
            )
        {
           return CreatePen(fnPenStyle,nWidth,crColor);
        }

        public bool DeleteOBJECT(IntPtr hObject)
        {
          return DeleteObject(hObject);
        }

        public IntPtr SelectObject(
            IntPtr hgdiobj   // handle to object
            )
        {
             return SelectObject(hdc,hgdiobj);
        }

        public void MoveTo(int X,int Y)
        {
           MoveToEx(hdc,X,Y,0);
        }

        public void LineTo(int X,int Y)
        {
            LineTo(hdc,X,Y);
        }

        public int SetROP2(drawingMode fnDrawMode)
        {
           return SetROP2(hdc,fnDrawMode);
        }

        [System.Runtime.InteropServices.DllImportAttribute(
             "gdi32.dll")]
        private static extern int SetROP2(
            IntPtr hdc,         // handle of device context
            drawingMode fnDrawMode      // drawing mode
            );  
       
        [System.Runtime.InteropServices.DllImportAttribute(
             "gdi32.dll")] 
        private static extern bool MoveToEx(
            IntPtr hdc,          // handle to device context
            int X,            // x-coordinate of new current position
            int Y,            // y-coordinate of new current position
            int oldp// pointer to old current position
            );

        [System.Runtime.InteropServices.DllImportAttribute(
             "gdi32.dll")]
        private static extern bool LineTo(
            IntPtr hdc,    // device context handle
            int nXEnd,  // x-coordinate of line's ending point
            int nYEnd   // y-coordinate of line's ending point
            );

        [System.Runtime.InteropServices.DllImportAttribute(
             "gdi32.dll")]
        private static extern IntPtr CreatePen(
            PenStyles fnPenStyle,    // pen style
            int nWidth,        // pen width
            int crColor   // pen color
            );

        [System.Runtime.InteropServices.DllImportAttribute(
             "gdi32.dll")]
        private static extern bool DeleteObject(IntPtr hObject   
                                               // handle to graphic object
            );

        [System.Runtime.InteropServices.DllImportAttribute(
             "gdi32.dll")]
        private static extern IntPtr SelectObject(
            IntPtr hdc,          // handle to device context
            IntPtr hgdiobj   // handle to object
            );

        public static int RGB(int R,int G,int B)
        {
            return (R|(G<<8)|(B<<16));         
        }
        
    
    }
}