🚀 go-pugleaf

Il Mon, 28 May 2007 20:02:21 +0200, Wookie <fa067235@skynet.be> ha scritto:

>Hi all,
>
>I am working inside a thread that drives a LCD screen and a camera. I
>have to synchronize the display on the LCD and the camera acquisition. I
>would like to know if there is any window message that is sent when a
>window has been repainted (a sort of WM_ENDPAINT). I do call the Repaint
>method of TWinControl but most of the time, the camera acquires a mix of
>the previous frame and the new one. How can I be sure the LCD has been
>fully repainted ?

Hi Christophe,

    I'm not sure if this approach can help you, but you could try to paint
directly from (synchronized with) the thread. Then you can invoke the GDIFlush
API whenever you need to have the screen updated. 

For example:

void __fastcall TYourThread::Execute()
{
    while ( !Terminated ) {
        TCanvas* Canvas = /* acquire here the control's canvas */
        Canvas->Lock();

        // Perform here the painting
 
        Canvas->Unlock();
        GdiFlush();
    }
}

or, for exception safety, something like this:

class TCanvasLockManager : boost::noncopyable {
public:
    TCanvasLockManager( TCanvas& Canvas )
      : canvas_( Canvas ) { canvas_.Lock(); }
    ~TCanvasLockManager() throw() { canvas_.Unlock(); }
    operator bool() const { return true; }
private:
    TCanvas& canvas_;
};

#define  LOCK_CANVAS( C ) \
    if ( bool const & C_lk ## __LINE__ = TCanvasLockManager( ( C ) ) )

struct TGDIFlusher {
    ~TGDIFlusher() throw() { GdiFlush(); }
};

void __fastcall TYourThread::Execute()
{
    while ( !Terminated ) {
        TCanvas* Canvas = /* acquire here the control's canvas */
        TGDIFlusher const GDIFlusher;
        LOCK_CANVAS( *Canvas ) {
            // Perform here the painting
        }
    }
}

Regards

Giuliano