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  1. #1
    Join Date
    May 2018
    Posts
    3

    Question Picturebox not refresh when the form is in background (not focus)

    Purpose: Mirror a window of an external process by capturing images from this window and presenting the images in a picturebox using a timer.

    Problem: When my application is in focus, everything happens fine! But if I switch the focus to the other window (not from my application), the picturebox stops refreshing the images. When I focus on my application again, everything returns to normal.

    Limitation: I need the picturebox to continue updating even though my application is in the background.

    Timer to capture images and show in picturebox:
    Code:
    private void timer_picBOX_refresh_Tick(object sender, EventArgs e)
       {
          pictureBox1.BackgroundImage = PrintScreen.CaptureWindow(GAME_MainHandle);            
          pictureBox1.Refresh();            
       }
    Class to capture specific window:
    Code:
    public class class_ScreenCapture
        {
            public Image CaptureScreen()
            {
                return CaptureWindow(User32.GetDesktopWindow());
            }
         
    	    /// <summary>
            /// Creates an Image object containing a screen shot of a specific window
            /// </summary>
            public Image CaptureWindow(IntPtr handle, int imgX = 0, int imgY = 0, int largura = 0, int altura = 0)
            {
                // get te hDC of the target window
                IntPtr hdcSrc = User32.GetWindowDC(handle);
                // get the size
                User32.RECT windowRect = new User32.RECT();
                User32.GetWindowRect(handle, ref windowRect);
    
                if (largura == 0 || altura == 0)
                {
                    largura = windowRect.right - windowRect.left;
                    altura = windowRect.bottom - windowRect.top;
                }
    
                // create a device context we can copy to
                IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
                // create a bitmap we can copy it to,
                // using GetDeviceCaps to get the width/height
                IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, largura, altura);
                // select the bitmap object
                IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);
                // bitblt over
                GDI32.BitBlt(hdcDest, 0, 0, largura, altura, hdcSrc, imgX, imgY, GDI32.SRCCOPY);
                // restore selection
                GDI32.SelectObject(hdcDest, hOld);
                // clean up 
                GDI32.DeleteDC(hdcDest);
                User32.ReleaseDC(handle, hdcSrc);
    
                // get a .NET image object for it
                Image img = Image.FromHbitmap(hBitmap);
                // free up the Bitmap object
                GDI32.DeleteObject(hBitmap);
    
                return img;
            }        
    
            /// <summary>
            /// Helper class containing Gdi32 API functions
            /// </summary>
            private class GDI32
            {
    
                public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter
    
                [DllImport("gdi32.dll")]
                public static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest,
                    int nWidth, int nHeight, IntPtr hObjectSource,
                    int nXSrc, int nYSrc, int dwRop);
                [DllImport("gdi32.dll")]
                public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth,
                    int nHeight);
                [DllImport("gdi32.dll")]
                public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
                [DllImport("gdi32.dll")]
                public static extern bool DeleteDC(IntPtr hDC);
                [DllImport("gdi32.dll")]
                public static extern bool DeleteObject(IntPtr hObject);
                [DllImport("gdi32.dll")]
                public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
            }
    
            /// <summary>
            /// Helper class containing User32 API functions
            /// </summary>
            private class User32
            {
                [StructLayout(LayoutKind.Sequential)]
                public struct RECT
                {
                    public int left;
                    public int top;
                    public int right;
                    public int bottom;
                }
    
                [DllImport("user32.dll")]
                public static extern IntPtr GetDesktopWindow();
                [DllImport("user32.dll")]
                public static extern IntPtr GetWindowDC(IntPtr hWnd);
                [DllImport("user32.dll")]
                public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
                [DllImport("user32.dll")]
                public static extern IntPtr GetWindowRect(IntPtr hWnd, ref RECT rect);
    
            }
        }

  2. #2
    Arjay's Avatar
    Arjay is offline Moderator / MS MVP Power Poster
    Join Date
    Aug 2004
    Posts
    12,674

    Re: Picturebox not refresh when the form is in background (not focus)

    Try debugging the program to figure out where the problem is. Add some debugger trace statements. Does the timer quit firing? Does the capture fail? Does the image control refresh fail? Narrowing the problem down will help you figure out what to do to fix it.

  3. #3
    Join Date
    May 2018
    Posts
    3

    Re: Picturebox not refresh when the form is in background (not focus)

    Quote Originally Posted by Arjay View Post
    Try debugging the program to figure out where the problem is. Add some debugger trace statements. Does the timer quit firing? Does the capture fail? Does the image control refresh fail? Narrowing the problem down will help you figure out what to do to fix it.
    All the code work in background. Only the visual UI of the form get frozen. Dnt happen when the active window is windows like webbrowser, notepad, calculator, etc. just with the directx game window. When this window get the focus, my winform get UI frozen. When I back the focus to my app this back to alive and proof that the code is runing when in background

  4. #4
    Arjay's Avatar
    Arjay is offline Moderator / MS MVP Power Poster
    Join Date
    Aug 2004
    Posts
    12,674

    Re: Picturebox not refresh when the form is in background (not focus)

    Quote Originally Posted by shafick View Post
    All the code work in background. Only the visual UI of the form get frozen. Dnt happen when the active window is windows like webbrowser, notepad, calculator, etc. just with the directx game window. When this window get the focus, my winform get UI frozen. When I back the focus to my app this back to alive and proof that the code is runing when in background
    Yes, you have already explained the issue in your first post and have described the result of the behavior, not the cause. You are going to have to do something else to figure out exactly what is going wrong. By adding debugger trace statements (or writing to a log file), you can record the behavior when the app has focus and then when the app doesn't have focus. Then you can compare the differences to help you narrow down what is wrong.

  5. #5
    Join Date
    May 2018
    Posts
    3

    Re: Picturebox not refresh when the form is in background (not focus)

    Quote Originally Posted by Arjay View Post
    Yes, you have already explained the issue in your first post and have described the result of the behavior, not the cause. You are going to have to do something else to figure out exactly what is going wrong. By adding debugger trace statements (or writing to a log file), you can record the behavior when the app has focus and then when the app doesn't have focus. Then you can compare the differences to help you narrow down what is wrong.
    The problem is: there is a type of window (directx games, like fifa, eurotruck, gta, etc) that when the focus is on it, all other windows (like webbrouser, notepad, word, windows explorer, etc) get the frozen visual (UI). To take the focus of this type of window, you must press ALT+TAB because the mouse does not exceed its borders.

    What I want is a way to avoid this IU freezing of my application when the game window is focused.
    Its is not a problem on my application it is a default behavior of this type of window.

    If you want to try, just open any game window and see the others windows.

  6. #6
    Arjay's Avatar
    Arjay is offline Moderator / MS MVP Power Poster
    Join Date
    Aug 2004
    Posts
    12,674

    Re: Picturebox not refresh when the form is in background (not focus)

    Quote Originally Posted by shafick View Post
    The problem is: there is a type of window (directx games, like fifa, eurotruck, gta, etc) that when the focus is on it, all other windows (like webbrouser, notepad, word, windows explorer, etc) get the frozen visual (UI). To take the focus of this type of window, you must press ALT+TAB because the mouse does not exceed its borders.

    What I want is a way to avoid this IU freezing of my application when the game window is focused.
    Its is not a problem on my application it is a default behavior of this type of window.

    If you want to try, just open any game window and see the others windows.
    Yes I got the issue from your first two descriptions of the same problem. If you are trying to solve this, you may want to try some of the things I have suggested.

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