🚀 go-pugleaf

Hi,

I've made a sample code to monitor the clipboard changes, and
write the changed clipboard contents (if text) to TMemo. I also
have one TCheckBox to say whether the monitoring should currently
be activated or not.

Unfortunately, *my* viewer works fine but *other* clipboard
viewers does not receive clipoard changes any more, untill I
close my app.

I tested that problematic issue with M$ ClipBook Viewer as a
secondary viewer:

C:\WINDOWS\system32\clipbrd.exe

Here's my code (I obviously missed something):

--- H ---

   HWND hNextViewer;

   MESSAGE void __fastcall ChangeChain(TMessage &Message);
   MESSAGE void __fastcall ClpBrdNotify(TMessage &Message);

   BEGIN_MESSAGE_MAP
      MESSAGE_HANDLER(WM_CHANGECBCHAIN,TMessage,ChangeChain)
      MESSAGE_HANDLER(WM_DRAWCLIPBOARD,TMessage,ClpBrdNotify)
   END_MESSAGE_MAP(TForm)


--- CPP ---

// ...
#include <ClipBrd.hpp>
// ...
void __fastcall TForm1::FormShow(TObject *Sender)
{
   static bool PassedOnceOnShow = false;

   if ( !PassedOnceOnShow )
   {
      if ( CheckBox1->Checked )
      {
         hNextViewer = SetClipboardViewer( Handle );
      }
   }
}

void __fastcall TForm1::FormClose(TObject *Sender, TCloseAction &Action)
{
   ChangeClipboardChain( Handle, hNextViewer );
}

void __fastcall TForm1::CheckBox1Click(TObject *Sender)
{
   if ( ! CheckBox1->Checked )
   {
      ChangeClipboardChain( Handle, hNextViewer );
   }
   else
   {
      hNextViewer = SetClipboardViewer( Handle );
   }
}

void __fastcall TForm1::ChangeChain( TMessage& Message )
{
   if ( (HWND)Message.WParam == hNextViewer )
      hNextViewer = (HWND)Message.LParam;

   PostMessage( hNextViewer, WM_CHANGECBCHAIN, (WPARAM)Message.WParam, 
(LPARAM)Message.LParam );
}

void __fastcall TForm1::ClpBrdNotify( TMessage& Message )
{
   if ( ::Clipboard()->HasFormat( CF_TEXT ) )
   {
      AnsiString cText = ::Clipboard()->AsText;
      Memo1->Lines->Add( cText );
   }
}



P.S.

Some additional questions:

1) How should I check the correctness of SetClipboardViewer()
regarding this:

BCB/Win32 Help:

<quote>
   SetClipboardViewer()
   Return Values
   If the function succeeds, the return value identifies the next window
   in the clipboard viewer chain. If an error occurs OR THERE ARE NO OTHER 
WINDOWS
   in the clipboard viewer chain, the return value is NULL. To get extended 
error
   information, call GetLastError.
</quote>

Can I use this:

   ::SetLastError( 0 );
   hNextViewer = SetClipboardViewer( Handle );
   if ( ( !hNextViewer ) && ( ::GetLastError() ) )
   {
      CheckBox1->Checked = false;
   }

2) Is there any signifficant differences between these two approachs
to read the clipboard:

   --- code 1 ---

   if ( ::Clipboard()->HasFormat( CF_TEXT ) )
   {
      AnsiString cText = ::Clipboard()->AsText;
      Memo1->Lines->Add( cText );
   }

   --- code 2 ---

   if ( IsClipboardFormatAvailable( CF_TEXT ) )
   {
      if ( OpenClipboard( Handle ) )
      {
         HANDLE cbh = GetClipboardData( CF_TEXT );
         if ( cbh != NULL )
         {
            AnsiString cText = AnsiString( (char*)GlobalLock( cbh ) );
            GlobalUnlock( cbh );
            Memo1->Lines->Add( cText );
         }
      }
      CloseClipboard();
   }



-- 
Best regards,
Vladimir Stefanovic