[Gui] Implement raiseDialog on Windows

Issue: #7774

changelog/unreleased/7774

@@ -0,0 +1,5 @@
+Bugfix: On Windows the share dialog somtimes does not open as the top most window
+
+We now ensure that the our dialogs are correctly raised.
+
+https://github.com/owncloud/client/issues/7774

src/gui/owncloudgui.cpp

@@ -1088,6 +1088,22 @@ void ownCloudGui::raiseDialog(QWidget *raiseWidget)
             False, // propagate
             SubstructureRedirectMask | SubstructureNotifyMask,
             &e);
+
+#elif defined(Q_OS_WIN)
+        // Windows disallows raising a Window when you're not the active application.
+        // Use a common hack to attach to the active application
+        const auto activeProcessId = GetWindowThreadProcessId(GetForegroundWindow(), nullptr);
+        if (activeProcessId != qApp->applicationPid()) {
+            const auto threadId = GetCurrentThreadId();
+            // don't step here with a debugger...
+            if (AttachThreadInput(threadId, activeProcessId, true))
+            {
+                const auto hwnd = reinterpret_cast<HWND>(raiseWidget->winId());
+                SetForegroundWindow(hwnd);
+                SetWindowPos(hwnd, HWND_TOP, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
+                AttachThreadInput(threadId, activeProcessId, false);
+            }
+        }
 #endif
     }
 }