CustomDraw ListView

• Download demo project - 10.7 Kb
• Download source - 16.1 Kb

Introduction

I wanted to customize the ListView control without going for the full owner draw approach. So custom draw was the obvious solution.

Background

I have done this sort of thing in ATL/WTL before, so I knew that I needed the parent of the control to reflect the notification message (.NET does by default). I also needed to handle the reflected notification message OCM_NOTIFY to perform my custom drawing. I stumbled across an interesting article by Georgi Atanasov, Customizing the header control in a ListView. So with the help of this article, I created my own sample ListView control that basically changes the font of the item text and sets the background color to that beautiful aqua color!!

Using the code

The EventListView.cs contains the ListView derived control and implements the ICustomDraw interface. The ICustomDraw interface contains the various stages of custom drawing that can occur:

int OnPrePaint(int idCtrl, ref Win32.NMCUSTOMDRAW nmcd);
int OnPostPaint(int idCtrl, ref Win32.NMCUSTOMDRAW nmcd);
int OnPreErase(int idCtrl, ref Win32.NMCUSTOMDRAW nmcd);
int OnPostErase(int idCtrl, ref Win32.NMCUSTOMDRAW nmcd);
int OnItemPrePaint(int idCtrl, ref Win32.NMCUSTOMDRAW nmcd);
int OnItemPostPaint(int idCtrl, ref Win32.NMCUSTOMDRAW nmcd);
int OnItemPreErase(int idCtrl, ref Win32.NMCUSTOMDRAW nmcd);
int OnItemPostErase(int idCtrl, ref Win32.NMCUSTOMDRAW nmcd);

It also contains a property Handle which is used to test that the reflect message really is for this control.

IntPtr Handel { get; }

EventListView class creates an object of type CustomDrawHandler and overrides the WndProc procedure and passes the message to this CustomDrawHandler.

protected override void WndProc(ref Message m)
{
    m_custDrawHandler.HandleReflectedCustDrawMessage(ref m);

    if (!m_custDrawHandler.MessageHandled)
        base.WndProc (ref m);
}

The HandleReflectedCustDrawMessage function checks to see if we have an OCM_NOTIFY message and that the message code is for CustomDraw. It then checks the draw stage and calls back onto the interface that was passed to its constructor, i.e., the ListView derived control. The EventListView.OnPrePaint function returns CDRF_NOTIFYITEMDRAW which causes the OnItemPrePaint function to be called. The OnItemPrePaint changes the background color of the item and draws the item text in an Arial font.

History

This is the first version of the custom draw in C#. Please feel free to email me with any comments or suggestions.

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