問題描述
獲取背景窗口的縮略圖 (Get Thumbnail of background window)
I'm trying to get thumbnail pictures of windows that are not visible.
Here's the code I have so far
BOOL CALLBACK WindowProc(HWND hWnd, LPARAM lParam)
{
RECT WindRect;
GetWindowRect(hWnd, &WindRect)
CurrentScreenShot‑>Next = new ScreenShotList();
CurrentScreenShot = CurrentScreenShot‑>Next;
HDC SourceDC = GetDC(hWnd);
HDC TargetDC = CreateCompatibleDC(SourceDC);
CurrentScreenShot‑>ScreenShot = CreateCompatibleBitmap(SourceDC, WindRect.right ‑ WindRect.left, WindRect.bottom ‑ WindRect.top);
BitBlt(TargetDC, 0, 0, WindRect.right ‑ WindRect.left, WindRect.bottom ‑ WindRect.top, SourceDC, 0, 0, SRCCOPY);
ReleaseDC(hWnd, SourceDC);
g_iWindows++;
return TRUE;
}
For now, WindowProc is being called directly using FindWindow to get a handle, though, I eventually want to use EnumWindows to loop through all of the windows to get their thumbnails and store them in a linked list.
WindowProc(FindWindow(NULL, L"File Explorer"), 0);
This code is in a DLL, which is called from a C# Forms application. For now the C# application just takes the bitmap and saves it to a file.
The problem is that unless I use FindWindow to get the visible window (which also happens to be the C# application), the picture ends up being a black box.
Is it possible to get an picture of a background window?
EDIT: This is a Windows Mobile application
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參考解法
方法 1:
There is no redrawing going on for invisible Windows, thats why you cannot get their content from the DC. Try sending a WM_PRINT message to the target window to request that it draws its content to your DC.
Edit:
Sorry, i did not notice this was for Windows Mobile. Other than WM_PRINT, i don't know a way to get the content of an invisible window. Of course you can still show the window (and make sure it is on top / not covered by other windows) and then run the code you have, but thats probably a bit messy.