When the titlebar is clicked, dismiss the new tab flyout

  Fixes #2028.

src/cascadia/TerminalApp/App.cpp

@@ -1649,6 +1649,23 @@ namespace winrt::TerminalApp::implementation
         return connection;
     }
 
+    // Method Description:
+    // - Used to tell the app that the titlebar has been clicked. The App won't
+    //   actually recieve any clicks in the titlebar area, so this is a helper
+    //   to clue the app in that a click has happened. The App will use this as
+    //   a indicator that it needs to dismiss any open flyouts.
+    // Arguments:
+    // - <none>
+    // Return Value:
+    // - <none>
+    void App::TitlebarClicked()
+    {
+        if (_newTabButton && _newTabButton.Flyout())
+        {
+            _newTabButton.Flyout().Hide();
+        }
+    }
+
     // -------------------------------- WinRT Events ---------------------------------
     // Winrt events need a method for adding a callback to the event and removing the callback.
     // These macros will define them both for you.

src/cascadia/TerminalApp/App.h

@@ -37,6 +37,7 @@ namespace winrt::TerminalApp::implementation
         ~App() = default;
 
         hstring GetTitle();
+        void TitlebarClicked();
 
         // -------------------------------- WinRT Events ---------------------------------
         DECLARE_EVENT(TitleChanged, _titleChangeHandlers, winrt::Microsoft::Terminal::TerminalControl::TitleChangedEventArgs);

src/cascadia/TerminalApp/App.idl

@@ -30,5 +30,7 @@ namespace TerminalApp
         event Windows.Foundation.TypedEventHandler<App, Windows.UI.Xaml.ElementTheme> RequestedThemeChanged;
 
         String GetTitle();
+
+        void TitlebarClicked();
     }
 }

src/cascadia/WindowsTerminal/AppHost.cpp

@@ -68,6 +68,11 @@ void AppHost::Initialize()
         // This has to be done _before_ App::Create, as the app might set the
         // content in Create.
         _app.SetTitleBarContent({ this, &AppHost::_UpdateTitleBarContent });
+
+        // Add an event handler to plumb clicks in the titlebar area down to the
+        // application layer.
+        auto pNcWindow = static_cast<NonClientIslandWindow*>(_window.get());
+        pNcWindow->DragRegionClicked([this]() { _app.TitlebarClicked(); });
     }
     _app.RequestedThemeChanged({ this, &AppHost::_UpdateTheme });
 

src/cascadia/WindowsTerminal/NonClientIslandWindow.cpp

@@ -263,14 +263,22 @@ void NonClientIslandWindow::_UpdateDragRegion()
 // - Hit test the frame for resizing and moving.
 // Arguments:
 // - ptMouse: the mouse point being tested, in absolute (NOT WINDOW) coordinates.
+// - titlebarIsCaption: If true, we want to treat the titlebar area as
+//   HTCAPTION, otherwise we'll return HTNOWHERE for the titlebar.
 // Return Value:
 // - one of the values from
 //  https://docs.microsoft.com/en-us/windows/desktop/inputdev/wm-nchittest#return-value
 //   corresponding to the area of the window that was hit
 // NOTE:
-// Largely taken from code on:
+// - Largely taken from code on:
 // https://docs.microsoft.com/en-us/windows/desktop/dwm/customframe
-[[nodiscard]] LRESULT NonClientIslandWindow::HitTestNCA(POINT ptMouse) const noexcept
+// NOTE[2]: Concerning `titlebarIsCaption`
+// - We want HTNOWHERE as the return value for WM_NCHITTEST, so that we can get
+//   mouse presses in the titlebar area. If we return HTCAPTION there, we won't
+//   get any mouse WMs. However, when we're handling the mouse events, we need
+//   to know if the mouse was in that are or not, so we'll return HTCAPTION in
+//   that handler, to differentiate from the rest of the window.
+[[nodiscard]] LRESULT NonClientIslandWindow::HitTestNCA(POINT ptMouse, const bool titlebarIsCaption) const noexcept
 {
     // Get the window rectangle.
     RECT rcWindow = BaseWindow::GetWindowRect();
@@ -311,10 +319,11 @@ void NonClientIslandWindow::_UpdateDragRegion()
 
     // clang-format off
     // Hit test (HTTOPLEFT, ... HTBOTTOMRIGHT)
+    const auto topHt = fOnResizeBorder ? HTTOP : (titlebarIsCaption ? HTCAPTION : HTNOWHERE);
     LRESULT hitTests[3][3] = {
-        { HTTOPLEFT,    fOnResizeBorder ? HTTOP : HTCAPTION, HTTOPRIGHT },
-        { HTLEFT,       HTNOWHERE,                           HTRIGHT },
-        { HTBOTTOMLEFT, HTBOTTOM,                            HTBOTTOMRIGHT },
+        { HTTOPLEFT,    topHt,      HTTOPRIGHT },
+        { HTLEFT,       HTNOWHERE,  HTRIGHT },
+        { HTBOTTOMLEFT, HTBOTTOM,   HTBOTTOMRIGHT },
     };
     // clang-format on
 
@@ -511,8 +520,7 @@ RECT NonClientIslandWindow::GetMaxWindowRectInPixels(const RECT* const prcSugges
         // Handle hit testing in the NCA if not handled by DwmDefWindowProc.
         if (lRet == 0)
         {
-            lRet = HitTestNCA({ GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam) });
-
+            lRet = HitTestNCA({ GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam) }, false);
             if (lRet != HTNOWHERE)
             {
                 return lRet;
@@ -594,9 +602,14 @@ RECT NonClientIslandWindow::GetMaxWindowRectInPixels(const RECT* const prcSugges
     {
         POINT point1 = {};
         ::GetCursorPos(&point1);
-        const auto region = HitTestNCA(point1);
+
+        const auto region = HitTestNCA(point1, true);
         if (region == HTCAPTION)
         {
+            // If we clicked in the titlebar, raise an event so the app host can
+            // dispatch an appropriate event.
+            _DragRegionClickedHandlers();
+
             const auto longParam = MAKELPARAM(point1.x, point1.y);
             ::SetActiveWindow(_window.get());
             ::PostMessage(_window.get(), WM_SYSCOMMAND, SC_MOVE | HTCAPTION, longParam);
@@ -798,3 +811,5 @@ bool NonClientIslandWindow::_HandleWindowPosChanging(WINDOWPOS* const windowPos)
     }
     return true;
 }
+
+DEFINE_EVENT(NonClientIslandWindow, DragRegionClicked, _DragRegionClickedHandlers, winrt::delegate<>);

src/cascadia/WindowsTerminal/NonClientIslandWindow.h

@@ -23,6 +23,7 @@ Author(s):
 #include <dwmapi.h>
 #include <windowsx.h>
 #include <wil\resource.h>
+#include "../../cascadia/inc/cppwinrt_utils.h"
 
 class NonClientIslandWindow : public IslandWindow
 {
@@ -42,6 +43,8 @@ class NonClientIslandWindow : public IslandWindow
     void SetContent(winrt::Windows::UI::Xaml::UIElement content) override;
     void SetTitlebarContent(winrt::Windows::UI::Xaml::UIElement content);
 
+    DECLARE_EVENT(DragRegionClicked, _DragRegionClickedHandlers, winrt::delegate<>);
+
 private:
     winrt::TerminalApp::TitlebarControl _titlebar{ nullptr };
     winrt::Windows::UI::Xaml::UIElement _clientContent{ nullptr };
@@ -55,7 +58,7 @@ class NonClientIslandWindow : public IslandWindow
 
     RECT GetDragAreaRect() const noexcept;
 
-    [[nodiscard]] LRESULT HitTestNCA(POINT ptMouse) const noexcept;
+    [[nodiscard]] LRESULT HitTestNCA(POINT ptMouse, const bool titlebarIsCaption) const noexcept;
 
     [[nodiscard]] HRESULT _UpdateFrameMargins() const noexcept;