Re: CListView with checkbox problem

"Tom Serface" <>
Thu, 19 Feb 2009 07:26:28 -0800
There are a number of problems with calling the GUI thread from a worker
thread, especially where MFC is involved. The right way to do it is to set
up a handler in the GUI thread that does what you want and post messages to
it using PostMessage() or SendMessage() if you want to block it whil the
message is being handled.

I agree with Victor, you should try to separate this code from your thread
and just post messages to the GUI to update your list. This could be why it
is not working as expected.

Of course, the thread to GUI stuff will sometimes work, but it's kind of a
timebomb since it will eventually fail.


"Victor" <> wrote in message

You must not directly access main GUI thread controls form within another
thread. You could find some info about it in MSDN, and I guess, Joe will
explain you this problem with more details. :)
Read Joe's essay about using worker threads:


"97612" <> wrote in message

//*********** code *************//
unsigned long _stdcall RunLoadThumbnailThread( LPVOID lpParam )
int nIndex = 0;
std::vector<CString>::iterator iter;

CThumbView *pView = (CThumbView*)lpParam;
CePhotoSyncDoc *pDoc = (CePhotoSyncDoc*)pView->GetDocument();

CListCtrl& ListCtrl = pView->GetListCtrl();
CImageList *pImgList = &pView->m_ImageListThumb;

int iImageCount = pImgList->GetImageCount();

for( int i=0; i < iImageCount; i++ )

pImgList->SetImageCount( pDoc->m_vFileName.size() );

ListCtrl.SetRedraw( FALSE );

for( iter = pDoc->m_vFileName.begin();
iter != pDoc->m_vFileName.end() && pView->m_bTerminate != TRUE;
iter++, nIndex++ )
  HBITMAP hbmReturn = NULL;
  Bitmap *bmPhoto = NULL;
   CBitmap Bmp1;

  ListCtrl.InsertItem( nIndex, *iter, nIndex );

  CString path; path.Empty();
  path.Format( _T("%s\\%s"), pDoc->m_strCurrentDirectory, *iter);

  Bitmap image( path.AllocSysString() );

  int sourceWidth = image.GetWidth();
  int sourceHeight = image.GetHeight();

  int destX = 0, destY = 0;

  float nPercent = 0;
  float nPercentW = ((float)THUMBNAIL_WIDTH/(float)sourceWidth);;
  float nPercentH = ((float)THUMBNAIL_HEIGHT/(float)sourceHeight);

  if(nPercentH < nPercentW)
  nPercent = nPercentH;
  destX = (int)((THUMBNAIL_WIDTH - (sourceWidth * nPercent))/2);
  nPercent = nPercentW;
  destY = (int)((THUMBNAIL_HEIGHT - (sourceHeight * nPercent))/2);

  int destWidth = (int)(sourceWidth * nPercent);
  int destHeight = (int)(sourceHeight * nPercent);

PixelFormat24bppRGB );
  bmPhoto->SetResolution( image.GetHorizontalResolution(),
image.GetVerticalResolution() );

  Graphics *grPhoto = Graphics::FromImage( bmPhoto );
  Color colorW(255, 255, 255, 255);
  grPhoto->Clear( colorW );
  grPhoto->SetInterpolationMode( InterpolationModeHighQualityBicubic );
  grPhoto->DrawImage( &image, Rect(destX, destY, destWidth,
destHeight) );

  bmPhoto->GetHBITMAP( colorW, &hbmReturn );

  Bmp1.Attach( hbmReturn );
  pImgList->Replace( nIndex, &Bmp1, NULL );

  delete grPhoto;
  delete bmPhoto;
  DeleteObject( hbmReturn );


pView->m_bRunning = FALSE;
pView->m_bTerminate = FALSE;

pView->m_hThreadLoad = NULL;
::CloseHandle( pView->m_hThreadLoad );

return 0;
//*********** code *************//

Above is the code I got from the Internet, run as a thread.

I don't really know the icon you mentioned, can you explain more for me?


"Tom Serface" wrote:

How are you setting up your bitmaps? Are you thinking your bitmap
the icon?


"97612" <> wrote in message

I got another problem. When I click a thumbnail image, the
"hitinfo.flags != LVHT_ONITEMSTATEICON" still true, and the program
returned. I don't know if I use the wrong way?

Below is my source code:
void CThumbView::OnLvnItemchanged(NMHDR *pNMHDR, LRESULT *pResult)
// TODO: Add your control notification handler code here
CListCtrl& ListCtrl = GetListCtrl();
*pResult = 0;

//Copy click point = pNMLV->ptAction;

//Make the hit test...
int nItem = ListCtrl.HitTest(&hitinfo);
//No click on image item, return
if(hitinfo.flags != LVHT_ONITEMSTATEICON)

//Image item hit
CePhotoSyncDoc* pDoc = (CePhotoSyncDoc*)GetDocument();
pDoc->SelectItem( pNMLV->iItem );
pDoc->UpdateAllViews(this, UPDATE_PREVIEW);

"97612" wrote:

Thanks for your help, it works.

Thanks a lot.

"Tom Serface" wrote:

You could check if the user clicked on the state icon:

    *pResult = 0;

 //Copy click point = pNMListView->ptAction;

 //Make the hit test...
 int nItem = m_cList.HitTest(&hitinfo);

 if(hitinfo.flags != LVHT_ONITEMSTATEICON)
      return; // Didn't click on an icon


"97612" <> wrote in message

I use CListView to draw the thumbnail of a image list. And I want
checkbox for the image list. When I select a thumbnail, the
trigger the "OnLvnItemchanged" event to let another view to show
image of the selected image.
My problem is that when I use
"OnLvnItemchanged" is trigger by the initial operation for
not I expected, how can I solve the problem?

Thanks for your help.

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