Force activate existing windows when running a commandline in them

src/cascadia/WindowsTerminal/AppHost.cpp

@@ -530,6 +530,7 @@ bool AppHost::HasWindow()
 void AppHost::_DispatchCommandline(winrt::Windows::Foundation::IInspectable /*sender*/,
                                    Remoting::CommandlineArgs args)
 {
+    _window->SummonWindow();
     _logic.ExecuteCommandline(args.Commandline(), args.CurrentDirectory());
 }
 

src/cascadia/WindowsTerminal/IslandWindow.cpp

@@ -844,5 +844,41 @@ void IslandWindow::_ApplyWindowSize()
                                          SWP_FRAMECHANGED | SWP_NOACTIVATE));
 }
 
+// Method Description:
+// - Force activate this window. This method will bring us to the foreground and
+//   activate us. If the window is minimized, it will restore the window. If the
+//   window is on another desktop, the OS will switch to that desktop.
+// Arguments:
+// - <none>
+// Return Value:
+// - <none>
+winrt::fire_and_forget IslandWindow::SummonWindow()
+{
+    // On the foreground thread:
+    co_await winrt::resume_foreground(_rootGrid.Dispatcher());
+
+    // From: https://stackoverflow.com/a/59659421
+    // > The trick is to make windows ‘think’ that our process and the target
+    // > window (hwnd) are related by attaching the threads (using
+    // > AttachThreadInput API) and using an alternative API: BringWindowToTop.
+    // If the window is minimized, then restore it. We don't want to do this
+    // always though, because if you SW_RESTORE a maximized window, it will
+    // restore-down the window.
+    if (IsIconic(_window.get()))
+    {
+        LOG_IF_WIN32_BOOL_FALSE(ShowWindow(_window.get(), SW_RESTORE));
+    }
+    const DWORD windowThreadProcessId = GetWindowThreadProcessId(GetForegroundWindow(), nullptr);
+    const DWORD currentThreadId = GetCurrentThreadId();
+
+    LOG_IF_WIN32_BOOL_FALSE(AttachThreadInput(windowThreadProcessId, currentThreadId, true));
+    // Just in case, add the thread detach as a scope_exit, to make _sure_ we do it.
+    auto detachThread = wil::scope_exit([windowThreadProcessId, currentThreadId]() {
+        LOG_IF_WIN32_BOOL_FALSE(AttachThreadInput(windowThreadProcessId, currentThreadId, false));
+    });
+    LOG_IF_WIN32_BOOL_FALSE(BringWindowToTop(_window.get()));
+    LOG_IF_WIN32_BOOL_FALSE(ShowWindow(_window.get(), SW_SHOW));
+}
+
 DEFINE_EVENT(IslandWindow, DragRegionClicked, _DragRegionClickedHandlers, winrt::delegate<>);
 DEFINE_EVENT(IslandWindow, WindowCloseButtonClicked, _windowCloseButtonClickedHandler, winrt::delegate<>);

src/cascadia/WindowsTerminal/IslandWindow.h

@@ -38,6 +38,8 @@ class IslandWindow :
     void FlashTaskbar();
     void SetTaskbarProgress(const size_t state, const size_t progress);
 
+    winrt::fire_and_forget SummonWindow();
+
 #pragma endregion
 
     DECLARE_EVENT(DragRegionClicked, _DragRegionClickedHandlers, winrt::delegate<>);

src/cascadia/WindowsTerminal/pch.h

@@ -56,8 +56,10 @@ Module Name:
 #include <windows.ui.xaml.hosting.desktopwindowxamlsource.h>
 
 // Additional headers for various xaml features. We need:
+//  * Core so we can resume_foreground
 //  * Controls for grid
 //  * Media for ScaleTransform
+#include <winrt/Windows.UI.Core.h>
 #include <winrt/Windows.UI.Xaml.Controls.h>
 #include <winrt/Windows.ui.xaml.media.h>