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React on changing window appearance

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Ok, here I am again, thinking about starting another project. You guys helped me alot the last time, and since I don't really know where to start, I thought I'd just ask a few questions here first.


It's a little tough to explain what I'm trying to do, but I'll give my best:

I want to make an application which basically does the following:

1) I want to drag and drop several windows from other applications inside my application window, so that they are stacked there (and don't take up my desktop space)

2) then I want to react to changes in the window appearance (this probably needs a fast algorithm or something). All I need to do is, once a fixed pixel inside this window changes it's color, I want to click that window.


I've never programmed anything like that before, so I really have no clue where to start and what to google for. I thought maybe you could give me a few keywords or tools with which I could achieve the above.


Thanks in advance.

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Ok, I got this somehow working. I'm able to capture window handles as children now.


I still get some weird bugs with the window handles from time to time, though. I'm capturing the handles with the following code:

/* Set as child */
HWND parent = (HWND)ui.widget->winId();
MoveWindow(handle, 0, 0, 0, 0, true); //place handle at (0,0) with a minimum size
SetParent(handle, parent);
DWORD style = GetWindowLong(handle, GWL_STYLE); //get the child style
//style &= ~(WS_POPUP | WS_CAPTION); //reset the "caption" and "popup" bits
style |= WS_CHILDWINDOW; //set the "child" bit
SetWindowLong(handle, GWL_STYLE, style); //set the new style of b
EnableWindow(handle, FALSE); // disabled the child

And I'm releasing it by:

/* Release child */
DWORD style = GetWindowLong(handle, GWL_STYLE); 
//style &= ~(WS_POPUP | WS_CAPTION); 
style &= ~WS_CHILDWINDOW; //remove the "child" bit
SetWindowLong(handle, GWL_STYLE, style);
SetParent(handle, NULL); // NULL to free it? what else should I put here?
MoveWindow(handle, 0, 0, 200, 200, true); //place at (0,0,200,200)
EnableWindow(handle, TRUE);

I'm getting the Pixel Colors with

GetPixel(GetDC(hwnd), x, y)

And here I get weird bugs from time to time. The console says:


QWindowsBackingStore::flush: GetDC failed()


In addition to that, when I move my mainwindow, containing a child, the window gets weird paint bugs, the widget just don't get repainted right anymore.

What am I doing wrong?

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