win32 content changed but doesn't show update unless window is moved

Question

My win32 GUI content changes every second but it doesn't show update unless the window is manually moved. I tried to pop up a messagebox every second to trigger the window to refresh and it worked. Hence it proves that my content really changes but the window doesnt update. I want the window to refresh without popping up a messagebox everytime, is there a windows function for this? Thanks

case WM_PAINT:


RECT fingerprintSection;
fingerprintSection.left=500;
fingerprintSection.top=300;
fingerprintSection.bottom=540;
fingerprintSection.right=660;

    wmId    = LOWORD(wParam);
    hdc = BeginPaint(hWnd, &ps);

    refresh=!refresh;
    if((start==true)&&(refresh==true)&&(stop!=true))
    {       

    windowName = MultiByteStringToWideString(name1, CP_ACP);
    LoadAndBlitBitmap(windowName.c_str(), hdc,500,0);//loading a picture that doesnt change
    fingerprint();
    LoadAndBlitBitmap(TEXT("outresized.bmp"), hdc,500,300);//loading a picture that constantly change
    refresh=!refresh;

//RedrawWindow(hWnd,&fingerprintSection,NULL,RDW_INTERNALPAINT|RDW_VALIDATE|RDW_UPDATENOW|RDW_NOCHILDREN);

InvalidateRect( hWnd, &fingerprintSection, TRUE );
    }
    EndPaint(hWnd, &ps);
    break;

you can use the RedrawWindow function: http://msdn.microsoft.com/en-us/library/windows/desktop/dd162911(v=vs.85).aspx — inixsoftware, Mar 09 '14 at 02:45
@inixsoftware, i tried the function InvalidateRect and loading the blitmap to paint it again in a loop. Does it deliver the same thing as RedrawWindow? — user3396218, Mar 09 '14 at 02:48
It should. It will send message to WM_REPAINT to force it repaint — inixsoftware, Mar 09 '14 at 02:50
=( the window is redrawn but it just doesn't show the update unless it's moved or a messagebox wakes it up. It's like having to press f5 everytime — user3396218, Mar 09 '14 at 02:53
Note, `WM_SHOWWINDOW` isn't a function. It is a **message** which you handle in WndProc — inixsoftware, Mar 09 '14 at 02:57
i used this RedrawWindow(hWnd,&fingerprintSection,NULL,RDW_UPDATENOW); but it still doesn't update unless i pop up a messagebox — user3396218, Mar 09 '14 at 03:06
If your content is in child windows, you'll need the `RDW_ALLCHILDREN` flag as well. — Jonathan Potter, Mar 09 '14 at 03:12
Hi. my content is in the main window and I would like to maintain the content at the child window. I updated the code. Kindly have a look and enlighten me if anything is wrong. thanks — user3396218, Mar 09 '14 at 03:48

TonyWilk · Accepted Answer · 2014-03-09T03:55:48.237

6

If you are drawing in a window outside of WM_PAINT (I guess in this case you are probably doing some GDI drawing on a timer when you get a WM_TIMER message), then you should call InvalidateRect() e.g.

InvalidateRect( hWnd, NULL, FALSE );   // invalidate whole window

This should cause Windows to redraw the whole window. If you have only written a small area, pass a RECT describing the area you have written.

If you want to draw when your windows procedure receives a WM_PAINT message AND for example, want to force that to happen every second, then set a timer...

#define SECOND_TIMER 1000

case WM_INITDIALOG:
   SetTimer( hWnd, SECOND_TIMER, SECOND_TIMER, NULL );
   //other initialisation stuff
   break;

case WM_TIMER:
   if( wParam == SECOND_TIMER )
   { 
       InvalidateRect( hWnd, NULL, FALSE );   // invalidate whole window
   }
   break;

In this simple case the whole window should be redrawn every second since Windows will send a WM_PAINT message due to the InvalidateRect. Ideally you should only invalidate the part you are redrawing.

edited Mar 09 '14 at 03:55

answered Mar 09 '14 at 03:18

TonyWilk

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10
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Hi. I'm doing the drawing inside WM_PAINT. i tried using InvalidateRect in a loop but it is not working for me. Here's my code. http://pastebin.com/d8PVQuBr – user3396218 Mar 09 '14 at 03:45
Doing drawing inside WM_PAINT will only be done when Windows sends your window procedure the WM_PAINT message. If your application is not doing anything, WM_PAINT will not be sent - unless, for example, you move another window in the desktop over your window. Simple fix added to answer above... – TonyWilk Mar 09 '14 at 03:50
I didn't know about that! Thank you very much for your fix and enlightenment! – user3396218 Mar 09 '14 at 04:01
You saved me here. Been hacking around for hours wondering why SetBitmapBits and SelectObject seemed only to work the first time but never refresh. InvalidateRect( hWnd, NULL, FALSE ); was the key. Thankyou! – KANJICODER Mar 09 '19 at 05:30

win32 content changed but doesn't show update unless window is moved

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