通过小部件获取顶层窗口

Question

I'm hooking the QPainter::drawText() function of a Qt5 application on Windows. My goal is to identify the native handle of the top-level-window to which the text is painted. First, I'm getting the associated widget.

QWidget *widget = static_cast<QWidget *>(painter->device());

So it should be possible to find the corresponding top-level window/widget. But it's harder than I thought. This is what I tried so far:

while (widget->parentWidget())
    widget = widget->parentWidget();

HWND hwnd = (HWND) widget->winId();

No success. The top-parent is never the desired window.

QApplication::topLevelWidgets()

Showed me that one single window contains several top-level-widgets (including the one I'm looking for).

I also tried QApplication::topLevelAt(widget->mapToGlobal(QPoint()))

In some cases this actually works, but not reliably. Depending on text and window position I'm getting a AccessViolationException , so this is not an option.

By testing widget->testAttribute(Qt::WA_NativeWindow) I found out that most of the widgets are non-native Alien Widgets .

This is how I get the (what I call) top-level window.

WinAPI.EnumChildWindows(
    WinAPI.GetDesktopWindow(),
    new EnumWindowsProc(this.EnumWindowsCallback), 0);

Then I check the window titles to find the handles I'm interested in.

I'm not able to find a relation from any (low-level) widget to the (top-level) widget that holds the window title.

Answer 1

For the QWidget that acts as a top level window, call QWidget::window() .

For the nearest parent with a native handle, call QWidget::nativeParentWidget() .

Calling winId() forces the widget to acquire a native window handle if it does not have one , which isn't your goal. A top level window will always have a native id, so (HWND)window()->winId() is fine. Note that this is usually the same as calling QWidget::effectiveWinId() .

Answer 2

It's done! I found a solution for my problem.

Each windows has it's own thread.

int threadId = WinApi.GetWindowThreadProcessId(wndHandle, IntPtr.Zero)

With it I use EnumThreadWindows to get a list of all window-handles created by this thread.

Finally I check wheather widget->effectiveWinId() is in the list.

So I can map each widget to its corresponding window!