Force activate existing windows when running a commandline in them (#…

…9137)

This will make sure to summon the terminal window when running a
commandline in it. 
* If the window is on another desktop, the OS will switch to the desktop
  the window is on. 
* If the window is minimized, it will restore it.

This is taken from my quake mode branch. It works aggressively. 848682a,
fee6473, 342d3f2, 5052d31 all had other attempts at doing this, but they
didn't work reliably. Part of the trick is that I don't _think_ Windows
wants one process to be able to move another process into the
foreground. In this case though, we _do_ want to move ourself into the
foreground, and this `AttachThreadInput` hack seems to be the only way
to do it reliably.

References #5000
Uses code authored for #653

Closes https://github.com/microsoft/terminal/projects/5#card-54636373

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>