Disable clicking on selected report view columns

I have developed a short piece of code to disable clicking column headers for columns than cannot be sorted-by.

This code simply uses the customization of header control as presented in "Indicating sort order" article. I just added slight more functionality to that header control.

1. I define a prototype and a variable in a class declaration body:


public:
	typedef BOOL (*ColumnCheckF)(void *,int,LPARAM);

	void SetCallback(ColumnCheckF checkf=NULL,void * cbdata=NULL)
	{
		m_fColumnCheck=checkf;
		m_pCBData=cbdata;
	}

private:
	ColumnCheckF m_fColumnCheck;
	void *m_pCBData;

After a click in a header, I find out the column (and I try to be wise and not disable clicking to resize columns) and ask the callback if the click is allowed (TRUE returned) or not.

It means, in the header (class declaration), I add


	// handlers
	afx_msg void OnLButtonDown(UINT,CPoint);
	DECLARE_MESSAGE_MAP()

and in the .CPP I add


BEGIN_MESSAGE_MAP(CCustHeaderCtrl,CHeaderCtrl)
	ON_WM_LBUTTONDOWN()
END_MESSAGE_MAP()

void CCustHeaderCtrl::OnLButtonDown(UINT flags,CPoint pt)
{
	if (m_fColumnCheck!=NULL)
	{
		HD_ITEM hditem;
		CClientDC dc(this);
		int offset=dc.GetTextExtent(_T(" "),1).cx*2;
		int x_coord=pt.x;

		int column=0;
		hditem.mask=HDI_WIDTH;
		while (x_coord>((column==0)?0:offset))
		{
			GetItem(column,&hditem);
			if (x_coord<hditem.cxy-offset)
			{
				// falls inside - query the func
				hditem.mask=HDI_LPARAM;
				GetItem(column,&hditem);
				if (!m_fColumnCheck(m_pCBData,column,hditem.lParam))
				{
					// don't forward the message!
					return;
				}
				break;
			}
			
			x_coord-=hditem.cxy;
			column++;
		}
	}

	CHeaderCtrl::OnLButtonDown(flags,pt);
}

The side effect of this code - it disables dragging the "disabled" columns. (That's because the header control never hears of LButtonDown message - I filter it of.)



Comments

  • Is any demo source is possible

    Posted by Legacy on 11/05/2001 12:00am

    Originally posted by: anup

    I need some demo code for this, if possible please send it to me.
    
    Thanks in advance.
    Anup

    Reply
Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Live Event Date: October 29, 2014 @ 11:00 a.m. ET / 8:00 a.m. PT Are you interested in building a cognitive application using the power of IBM Watson? Need a platform that provides speed and ease for rapidly deploying this application? Join Chris Madison, Watson Solution Architect, as he walks through the process of building a Watson powered application on IBM Bluemix. Chris will talk about the new Watson Services just released on IBM bluemix, but more importantly he will do a step by step cognitive …

  • Live Event Date: November 13, 2014 @ 2:00 p.m. ET / 11:00 a.m. PT APIs can be a great source of competitive advantage. The practice of exposing backend services as APIs has become pervasive, however their use varies widely across companies and industries. Some companies leverage APIs to create internal, operational and development efficiencies, while others use them to drive ancillary revenue channels. Many companies successfully support both public and private programs from the same API by varying levels …

Most Popular Programming Stories

More for Developers

Latest Developer Headlines

RSS Feeds