Capture HWND with context menu

Question

I am using WinAPI to capture the windows in Java.

public static BufferedImage capture(Pointer hWnd2, String wText) {
   HWND hWnd = new HWND(hWnd2);
   boolean success;
   if(User32Extra.INSTANCE.IsIconic(hWnd))
   {
       success= User32Extra.INSTANCE.ShowWindow(hWnd, 4);
       System.err.println(success);
       System.err.println(wText+Native.getLastError());
   }
   HDC hdcWindow2 = User32.INSTANCE.GetDC(hWnd);
   HDC hdcMemDC = GDI32.INSTANCE.CreateCompatibleDC(hdcWindow2);
   success = User32Extra.INSTANCE.PrintWindow(hWnd,hdcWindow2,1);
   RECT bounds = new RECT();
   RECT bounds1 = new RECT();
   User32Extra.INSTANCE.GetWindowRect(hWnd, bounds);
   User32Extra.INSTANCE.GetClientRect(hWnd, bounds1);

   int extraGap = (bounds.right-bounds.left-bounds1.right);
   int width = bounds.right-bounds.left-extraGap;
   int height = bounds.bottom-bounds.top-extraGap ;
   HBITMAP hBitmap = GDI32.INSTANCE.CreateCompatibleBitmap(hdcWindow2, width, height);

   HANDLE hOld = GDI32.INSTANCE.SelectObject(hdcMemDC, hBitmap);
   GDI32Extra.INSTANCE.BitBlt(hdcMemDC,0, 0, width, height, hdcWindow2, bounds.left+bounds1.right-bounds.right+extraGap, bounds.top+bounds1.bottom-bounds.bottom+extraGap, WinGDIExtra.SRCCOPY);
   GDI32.INSTANCE.SelectObject(hdcMemDC, hOld);

   BITMAPINFO bmi = new BITMAPINFO();
   bmi.bmiHeader.biWidth = width;
   bmi.bmiHeader.biHeight = -height;
   bmi.bmiHeader.biPlanes = 1;
   bmi.bmiHeader.biBitCount = 32;
   bmi.bmiHeader.biCompression = WinGDI.BI_RGB;
   Memory buffer = new Memory(width * height * 4);
   GDI32.INSTANCE.GetDIBits(hdcWindow2, hBitmap, 0, height, buffer, bmi, WinGDI.DIB_RGB_COLORS);

   BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

   GDI32.INSTANCE.DeleteObject(hBitmap);
   GDI32.INSTANCE.DeleteDC(hdcMemDC);
   User32.INSTANCE.ReleaseDC(hWnd, hdcWindow2);

   return image;
}

This code captures the HWND specified window. But if the user opens the context menu or menu bar options. Those are not being captured.

How to capture context menu of the window?

Answer 1

I would use GetDesktopWindow() to capture entire screen, then pass window coordinates to BitBlt to copy only target window with all overlays (including context menu)

public static BufferedImage capture(Pointer hWnd2, String wText) {
   HWND hWnd = new HWND(hWnd2);
   boolean success;
   if(User32Extra.INSTANCE.IsIconic(hWnd))
   {
       success= User32Extra.INSTANCE.ShowWindow(hWnd, 4);
       System.err.println(success);
       System.err.println(wText+Native.getLastError());
   }
   // Pass GetDesktopWindow instead of target HWND to GetDC
   HDC hdcWindow2 = User32.INSTANCE.GetDC(User32.INSTANCE.GetDesktopWindow());
   HDC hdcMemDC = GDI32.INSTANCE.CreateCompatibleDC(hdcWindow2);

   RECT bounds = new RECT();
   //RECT bounds1 = new RECT();
   User32Extra.INSTANCE.GetWindowRect(hWnd, bounds);
   //User32Extra.INSTANCE.GetClientRect(hWnd, bounds1);

   //int extraGap = (bounds.right-bounds.left-bounds1.right);
   int width = bounds.right-bounds.left;
   int height = bounds.bottom-bounds.top;
   HBITMAP hBitmap = GDI32.INSTANCE.CreateCompatibleBitmap(hdcWindow2, width, height);

   HANDLE hOld = GDI32.INSTANCE.SelectObject(hdcMemDC, hBitmap);
   GDI32Extra.INSTANCE.BitBlt(hdcMemDC,0, 0, width, height, hdcWindow2, bounds.left, bounds.top, WinGDIExtra.SRCCOPY);
   GDI32.INSTANCE.SelectObject(hdcMemDC, hOld);

   BITMAPINFO bmi = new BITMAPINFO();
   bmi.bmiHeader.biWidth = width;
   bmi.bmiHeader.biHeight = -height;
   bmi.bmiHeader.biPlanes = 1;
   bmi.bmiHeader.biBitCount = 32;
   bmi.bmiHeader.biCompression = WinGDI.BI_RGB;
   Memory buffer = new Memory(width * height * 4);
   GDI32.INSTANCE.GetDIBits(hdcWindow2, hBitmap, 0, height, buffer, bmi, WinGDI.DIB_RGB_COLORS);

   BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

   GDI32.INSTANCE.DeleteObject(hBitmap);
   GDI32.INSTANCE.DeleteDC(hdcMemDC);
   User32.INSTANCE.ReleaseDC(hWnd, hdcWindow2);

   return image;
}

This method, however, will capture other window if it is overlapping our target window. It is probably sufficient if you know that window is active or have context menu opened (because it will enforce it to be foreground) .

Another approach is a bit hacky, but it works for other scenarios. We can check if there are any windows with class name #32768 (class for popup menus). If there is, we check whether our target window is foreground one, and then we can copy it to our target bitmap on top of our window.

public static BufferedImage capture(Pointer hWnd2, String wText) {
    HWND hWnd = new HWND(hWnd2);
    boolean success;
    if(User32Extra.INSTANCE.IsIconic(hWnd))
    {
        success= User32Extra.INSTANCE.ShowWindow(hWnd, 4);
        System.err.println(success);
        System.err.println(wText+Native.getLastError());
    }
    HDC hdcWindow2 = User32.INSTANCE.GetDC(hWnd);
    final HDC hdcMemDC = GDI32.INSTANCE.CreateCompatibleDC(hdcWindow2);

    RECT bounds = new RECT();
    RECT bounds1 = new RECT();
    User32Extra.INSTANCE.GetWindowRect(hWnd, bounds);
    User32Extra.INSTANCE.GetClientRect(hWnd, bounds1);

    int extraGap = (bounds.right-bounds.left-bounds1.right);
    int width = bounds.right-bounds.left-extraGap;
    int height = bounds.bottom-bounds.top-extraGap ;
    HBITMAP hBitmap = GDI32.INSTANCE.CreateCompatibleBitmap(hdcWindow2, width, height);

    HANDLE hOld = GDI32.INSTANCE.SelectObject(hdcMemDC, hBitmap);
    GDI32Extra.INSTANCE.BitBlt(hdcMemDC,0, 0, width, height, hdcWindow2, bounds.left+bounds1.right-bounds.right+extraGap, bounds.top+bounds1.bottom-bounds.bottom+extraGap, WinGDIExtra.SRCCOPY);

    // Popup menu doesn't have parent, so we could encounter situation when context menu from another window is overlapping our target window
    // Since context menu enforces our window to focus, we can check here if our window is foreground window (otherwise it is not possible to have opened context menu)
    if (User32.INSTANCE.GetForegroundWindow() == hWnd)
    {
        final RECT windowBounds = bounds;
        // Enum all windows and check if they have class #32768
        User32.INSTANCE.EnumWindows(new WNDENUMPROC() {
            @Override
            public boolean callback(HWND hMenuWnd, Pointer arg1) {
                byte[] windowClass = new byte[8];
                User32.INSTANCE.GetClassNameA(hMenuWnd, windowClass, 8);
                String wClass = Native.toString(windowClass);
                // #32768 is class name for popup menus.
                if (wClass.equals("#32768"))
                {
                    HDC hdcWindowMenu = User32.INSTANCE.GetDC(hMenuWnd);
                    RECT menuBounds = new RECT();
                    User32Extra.INSTANCE.GetWindowRect(hMenuWnd, menuBounds);
                    GDI32Extra.INSTANCE.BitBlt(hdcMemDC, menuBounds.left - windowBounds.left, menuBounds.top - windowBounds.top, menuBounds.right-menuBounds.left, menuBounds.bottom-menuBounds.top, hdcWindowMenu, 0, 0, WinGDIExtra.SRCCOPY);
                    User32.INSTANCE.ReleaseDC(hMenuWnd, hdcWindowMenu);
                }
                return true;
            }
        }, null);
    }

    GDI32.INSTANCE.SelectObject(hdcMemDC, hOld);

    BITMAPINFO bmi = new BITMAPINFO();
    bmi.bmiHeader.biWidth = width;
    bmi.bmiHeader.biHeight = -height;
    bmi.bmiHeader.biPlanes = 1;
    bmi.bmiHeader.biBitCount = 32;
    bmi.bmiHeader.biCompression = WinGDI.BI_RGB;
    Memory buffer = new Memory(width * height * 4);
    GDI32.INSTANCE.GetDIBits(hdcWindow2, hBitmap, 0, height, buffer, bmi, WinGDI.DIB_RGB_COLORS);

    BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

    GDI32.INSTANCE.DeleteObject(hBitmap);
    GDI32.INSTANCE.DeleteDC(hdcMemDC);
    User32.INSTANCE.ReleaseDC(hWnd, hdcWindow2);

    return image;
}

For EnumWindows you have to add following import:

import com.sun.jna.platform.win32.WinUser.WNDENUMPROC;

and definition:

boolean EnumWindows(WinUser.WNDENUMPROC lpEnumFunc, Pointer arg);
int GetClassNameA(HWND hWnd, byte[] lpString, int nMaxCount);