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How to set a minimum column width

Posted by Zafir Anjum on August 6th, 1998
Again we have to override the OnNotify() function. The code below restricts the columns to a minimum width of 80 pixels. The logic can be extended to restrict the width within a range or even specify different range for different columns. To extend the functionality, you would need to add member variables to the class to track the different settings. 
BOOL CMyListCtrl::OnNotify(WPARAM wParam, LPARAM lParam, LRESULT* pResult) 
{
    HD_NOTIFY   *pHDN = (HD_NOTIFY*)lParam;

        if((pHDN->hdr.code == HDN_ITEMCHANGINGW || pHDN->hdr.code == HDN_ITEMCHANGINGA) 
                && pHDN->pitem->cxy < 80)
        {
                *pResult = TRUE;                // disable change
                return TRUE;                    // Processed message
        }
 
        return CListCtrl::OnNotify(wParam, lParam, pResult);
}
 

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Comments

  • Fix when dragging fast

    Posted by Legacy on 11/30/1998 12:00am

    Originally posted by: Cees Mechielsen 

    The solutions given up till this point all have the disadvantage that

    the end point is missed when you drag faster than the system samples

    the mouse position. 

    This can easily be fixed. Just replace:


        *pResult = TRUE;    // disable change 

    	return TRUE;	    // Processed message 


    with:


        pHDN->pitem->cxy = 80;


    In the examples.


    The entire code now looks like this:


        if( ( pHDN->hdr.code == HDN_ITEMCHANGINGW ||

    	      pHDN->hdr.code == HDN_ITEMCHANGINGA ||

    	      pHDN->hdr.code == HDN_ENDTRACK) 

    	   && 

    	    ( pHDN->pitem->mask & HDI_WIDTH &&

    	      pHDN->pitem->cxy < 80 &&

    	      pHDN->pitem->cxy >= 0 )

    	  ) 

    	{

    	    pHDN->pitem->cxy = 80;	// Set the column width

    	}


        return CListView::OnNotify(wParam, lParam, pResult);


    Have Fun!

    Cees.

    Reply

  • Column resizing when "Show window contents while dragging" is not checked

    Posted by Legacy on 11/27/1998 12:00am

    Originally posted by: Grant Gussie 

    In the control panel Display|Plus! is an item "Show window contents while dragging". If this item
is not checked, the HDN_ITEMCHANGING messages are suppressed, and the code listed above will not work. What
is sent, however, is a HDN_ENDTRACK message after the dragging is finished.


    I would recommend that the code be modified so that the HDN_ENDTRACK messages are trapped along with the
HDN_ITEMCHANGING messages. For example, look at the code below, which also encorporates Michael Easter's
suggestion of examining the mask. 


    BOOL CMyListCtrl::OnNotify(WPARAM wParam, LPARAM lParam,

    	LRESULT* pResult)

    {

    	HD_NOTIFY* pHDN = (HD_NOTIFY*)lParam;


        if(( pHDN->hdr.code == HDN_ITEMCHANGING ||  pHDN->hdr.code == HDN_ENDTRACK) && 
(pHDN->pitem->mask & HDI_WIDTH &&  pHDN->pitem->cxy < 80)) 

    	{

    	    *pResult = TRUE;

    	    return TRUE;

    	}


        return CListCtrl::OnNotify(wParam, lParam, pResult);

    }

    Reply

  • Fix for column headers

    Posted by Legacy on 11/21/1998 12:00am

    Originally posted by: Michael Easter 

    Zafir's article How to force a minimum column width describes an easy

    method to set and enforce a minimum column width. However, the method 

    can prevent non-resizing changes to the column header to not take

    effect. For example, adding images or sort indicators to the column 

    header.


    A small change to Zafir's code fixes the problem. Add a check to see 

    if the change is related to column size.


    pHDN->pitem->mask & HDI_WIDTH


    The entire function with the change added is below. See Zafir's 

    article for a complete description.


    

    BOOL CMyListCtrl::OnNotify(WPARAM wParam, LPARAM lParam, 

    			       LRESULT* pResult)

    {

    	HD_NOTIFY* pHDN = (HD_NOTIFY*)lParam;


        if ((pHDN->hdr.code == HDN_ITEMCHANGINGW || 

    	     pHDN->hdr.code == HDN_ITEMCHANGINGA) &&

    	     pHDN->pitem->mask & HDI_WIDTH && pHDN->pitem->cxy < 80) 

    	{

    	     *pResult = TRUE;

    	     return TRUE;

    	}


        return CListCtrl::OnNotify(wParam, lParam, pResult);

    }

    Reply

  • Slight modification for owner-drawn column headers

    Posted by Legacy on 10/28/1998 12:00am

    Originally posted by: Chip Calvert 

    This is an excellent article.  Thanks for writing it.  It was a big help to me.  However, when I implemented
it, I ran into a problem.  The column headers in my CListCtrl were ownerdrawn.	The if statement below was
catching the calls for redrawing in addition to those for resizing.


    if((pHDN->hdr.code == HDN_ITEMCHANGINGW || 

       pHDN->hdr.code == HDN_ITEMCHANGINGA) 

       && pHDN->pitem->cxy < 80)


    I would recommend changing it to:


    if((pHDN->hdr.code == HDN_ITEMCHANGINGW || 

       pHDN->hdr.code == HDN_ITEMCHANGINGA) &&

       (pHDN->pitem->cxy < 80 && pHDN->pitem->cxy >= 0))


    From my testing, it appears that the value of pHDN->pitem->cxy is a negative number when the call is
for redrawing and not resizing.

    Reply
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