🚀 go-pugleaf

Remy,

thanks for the advice.

>> I am thinking about a separate window, appropriately sized, with a
>> transparent background and the cross hair drawn on it, so sit on top
>> of the image display window (which is also the main program window).
>
>Why not just maintain a separate bitmap in memory, copy your images to it
>when needed, draw the cross directly onto it whenever you change it, and
>then have the main window simply render the current bitmap when needed?
>This is known as "double-buffering".

I'm dealing with slow computers (industrials, Pentium 166 MHz w/ MMX)
and am trying to run the frame grabber (which supplies the image
stream as bitmaps already)  at full speed, i.e., 30 fps.  I'll try
this.

>> 2.  If it is, how do I tell it to not display a title bar?
>
>Simply don't give the window the WS_CAPTION style.

That's what I thought, but it refuses to do as told.  Here is how the
main and the overlay windows are defined right now (no transparency
yet):

    // Register window class
    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hInst;
    wndclass.hIcon = LoadIcon (hInst, "ICONX11");
    wndclass.hCursor = LoadCursor (NULL, IDC_ARROW);
    wndclass.hbrBackground = GetStockObject (WHITE_BRUSH);
    wndclass.lpszMenuName = "Sample2";
    wndclass.lpszClassName = szAppName;
    RegisterClass (&wndclass);

    // Create program window
        xwidth  = XACT_NTSC + GetSystemMetrics(SM_CXBORDER) * 2 ;
        yheight = YACT_NTSC + GetSystemMetrics(SM_CYCAPTION) +
                                        GetSystemMetrics(SM_CYMENU) ;
    hwndMain = CreateWindow(szAppName, szAppName,
                                       WS_OVERLAPPEDWINDOW ^
                                          WS_MAXIMIZEBOX ^WS_SIZEBOX,
                                       CW_USEDEFAULT, CW_USEDEFAULT,
                                       xwidth,
                                       yheight +
                                    GetSystemMetrics(SM_CYBORDER) * 2,
                                       NULL, NULL, hInst, NULL);

    ShowWindow (hwndMain, SW_SHOWNORMAL);
    SetWindowPos (hwndMain, HWND_TOP, 0, 0, xwidth, yheight,
                                    SWP_NOMOVE);

    hMenuAcq = GetSubMenu(GetMenu(hwndMain), 1); // Acquisition menu

    // Register window class
    crossclass.style = CS_HREDRAW | CS_VREDRAW;
    crossclass.lpfnWndProc = WndProc;
    crossclass.cbClsExtra = 0;
    crossclass.cbWndExtra = 0;
    crossclass.hInstance = hInst;
    crossclass.hIcon = LoadIcon (hInst, "ICONX11");
    crossclass.hCursor = LoadCursor (NULL, IDC_ARROW);
    crossclass.hbrBackground = GetStockObject (WHITE_BRUSH);
    crossclass.lpszMenuName = NULL ;
    crossclass.lpszClassName = szCrosshair;
    RegisterClass (&crossclass);
        // Create overlay window for cross hair.
        GetWindowRect(hwndMain, &mainRect) ;
        xwidth = XACT_NTSC + 2 ;
        yheight = YACT_NTSC + 2 ;
        hwndCross = CreateWindow(szCrosshair, NULL,
                               WS_BORDER,
                               mainRect.left +
                                    GetSystemMetrics(SM_CXBORDER) - 1,
                               mainRect.top +
                                    GetSystemMetrics(SM_CYBORDER) +
                                    GetSystemMetrics(SM_CYCAPTION) +
                                    GetSystemMetrics(SM_CYMENU),
                               xwidth, yheight,
                               hwndMain, NULL, hInst, NULL) ;
        SetMenu(hwndCross, NULL) ;
        ShowWindow(hwndCross, SW_SHOWNORMAL) ;
        SetWindowPos(hwndCross, HWND_TOP, 0, 0, xwidth, yheight,
                                        SWP_NOMOVE) ;

It does not matter if I keep this a separate window class, or reuse
the main window class, and what I put in for the style - WS_BORDER,
WS_DLGFRAME, WS_OVERLAPPED (which is 0x0L) all give the same result,
i.e., there is a title bar.  I also can set the icon handle to NULL
and there still is a title bar.  The paint process for the overlay
window is all of

     BeginPaint(&ps); EndPaint(&ps);

If you now think this guy has never done plain API windows you are
right - I have for a long time gone with OWL, and have for a bunch of
more recent apps usually used VCL.  My problem here is that I have the
plain windows app which does everyhing I want except that the cross
hair gets drawn on every displayed image and I want to shave off that
time (and get id of the unstable cross display, I got customers to
please ...).

>> 3.  How do I tell it to have a transparent background?
>
>Give the window the WS_EX_TRANSPARENT style, and also intercept the
>WM_ERASEBKGND message to not actually draw any background.

Now that's easy ...


Thanks again,

Jochen

hjtrost at microfab dot com


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