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Generating missing Paint event for TreeView and ListView controls

, 14 Jul 2003
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Article on generating missing Paint event for TreeView, ListView

Microsoft .NET forms controls like TreeView and Listview are just wrappers around the controls in ComCtl. As such they do not normally invoke the Paint event. The only suggestion I have seen posted is to set the ControlStyles.UserPaint style and do all the drawing yourself!

TreeViewWithPaint Control

To solve this problem a internal Graphics object based on a Bitmap was used. It is re-created during any Resize.

//Recreate internal graphics object
protected override void OnResize( System.EventArgs e ) {
    if( internalBitmap == null  ||
        internalBitmap.Width != Width || internalBitmap.Height != Height ) {

        if( Width != 0 && Height != 0 ) {
            DisposeInternal();
            internalBitmap = new Bitmap( Width, Height );
            internalGraphics = Graphics.FromImage( internalBitmap );
        }
    }
}

When the control receives a WM_PAINT, three steps are performed:

  1. The ComCtl is painted into the internal Graphics object via a WM_PRINTCLIENT message.
    //Draw Internal Graphics
    IntPtr hdc = internalGraphics.GetHdc();
    Message printClientMessage = Message.Create( Handle, 
         WM_PRINTCLIENT, hdc, IntPtr.Zero );  
    DefWndProc( ref printClientMessage );
    internalGraphics.ReleaseHdc( hdc );
  2. The OnPaint() is now invoked using PaintEventArgs constructed from the internal Graphics object.
    //Add the missing OnPaint() call
    OnPaint( new PaintEventArgs( internalGraphics, Rectangle.FromLTRB( 
        updateRect.left,
        updateRect.top,
        updateRect.right,
        updateRect.bottom ) ) );
  3. The Bitmap of the internal Graphics object is copied to the normal screen Graphics device.
    //Draw Screen Graphics
    screenGraphics.DrawImage( internalBitmap, 0, 0 );

Also the WM_ERASEBKGND was filtered out to remove flicker.

case WM_ERASEBKGND:
    //removes flicker
    return;

Also the Paint event was added to restore browsable attributes.

[
//Re-enable Attributes for the Paint Event
EditorBrowsableAttribute( EditorBrowsableState.Always ),
BrowsableAttribute(true)
]
public new event PaintEventHandler Paint {
    add   { base.Paint += value; }
    remove{ base.Paint -= value; }
}

Using the code

To use the TreeViewWithPaint control:

  1. Just add the control to the toolbox.
  2. Drag it on to your form.
  3. Attach a Paint handler to the now exposed Paint event.

To create a <AnotherComCtl>WithPaint, modify TreeViewWithPaint as follows:

  1. Use <AnotherComCtl> as the base class.
  2. Copy the <AnotherComCtl> class attributes to the <AnotherComCtl>WithPaint class.
  3. Add an <AnotherComCtl>WithPaint.bmp, which is a 16x16 bit map used for the toolbox icon.

TreeViewWithPaint Control Test Bench

I created a simple Form containing a single TreeViewWithPaint control. The Paint event can now be used.

treeViewWithPaint1.Paint += new PaintEventHandler( 
       treeViewWithPaint1_Paint );

This particular Paint handler just draws a simple white band inside the selected node.

//Add a simple yellow band inside the selected node
private void treeViewWithPaint1_Paint(object sender, PaintEventArgs e) {
    Graphics g = e.Graphics;
    TreeNode node = treeViewWithPaint1.SelectedNode;
    
    if( node != null && node.IsVisible ) {
        using( Pen pen = new Pen( Color.Yellow ) ) {
            g.DrawRectangle( pen, 
                node.Bounds.X + 1,
                node.Bounds.Y + 1,
                node.Bounds.Width  - 3,
                node.Bounds.Height - 3
                );
        }
    }
}

Points of Interest

  • The needed attributes were discovered by using the VB (not C#) object browser for VS 2002 (not VS 2003).
  • There is an undocumented feature of XP that horizontal scroll bars appear on TreeView if you add items at design time.

License

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A list of licenses authors might use can be found here

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About the Author

J Young

United States United States
No Biography provided

Comments and Discussions

 
GeneralCustom DrawNod PinmemberDblK29-Jun-09 11:43 
GeneralRIGHT TO LEFT DISPLAY NOT CORRECT Pinmemberbenchserv18-May-08 18:17 
Questionget internalgraphics with alpha? Pinmemberboxed19-Jul-06 4:31 
GeneralFlickerfree Treeview PinmemberIvi2210-Jul-06 1:17 
GeneralUpdate PinmemberIvi226-Aug-07 3:10 
QuestionListView Pain Evetn in VB.NET Pinmemberk^s4-May-06 4:50 
QuestionRe: ListView Pain Evetn in VB.NET Pinmemberk^s4-May-06 7:10 
AnswerRe: ListView Pain Evetn in VB.NET PinmemberGraznok29-Sep-11 10:42 
QuestionLegal info? PinmemberFilip Fracz30-Jan-06 11:47 
Generalorganization chart (horizontal tree view) Pinmembercahnakal4-Oct-05 0:23 

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