Fix extra padding when tabs are outside the title bar

src/cascadia/LocalTests_TerminalApp/TabTests.cpp

@@ -86,6 +86,7 @@ namespace TerminalAppLocalTests
         TEST_METHOD(SwapPanes);
 
         TEST_METHOD(NextMRUTab);
+        TEST_METHOD(TabRowVisibilityReflectsTabCount);
         TEST_METHOD(VerifyCommandPaletteTabSwitcherOrder);
 
         TEST_METHOD(TestWindowRenameSuccessful);
@@ -1144,6 +1145,24 @@ namespace TerminalAppLocalTests
         });
     }
 
+    void TabTests::TabRowVisibilityReflectsTabCount()
+    {
+        auto page = _commonSetup();
+
+        TestOnUIThread([&page]() {
+            VERIFY_IS_FALSE(page->IsTabRowVisible(), L"Single tab with tabs hidden in title bar should not show the tab row.");
+        });
+
+        TestOnUIThread([&page]() {
+            NewTerminalArgs newTerminalArgs{ 1 };
+            page->_OpenNewTab(newTerminalArgs);
+        });
+
+        TestOnUIThread([&page]() {
+            VERIFY_IS_TRUE(page->IsTabRowVisible(), L"Multiple tabs should make the tab row visible when tabs are outside the title bar.");
+        });
+    }
+
     void TabTests::VerifyCommandPaletteTabSwitcherOrder()
     {
         // This is a test for GH#8188 - we want to make sure that the order of tabs

src/cascadia/TerminalApp/TabManagement.cpp

@@ -244,11 +244,7 @@ namespace winrt::TerminalApp::implementation
         // - we're not in focus mode
         // - we're not in full screen, or the user has enabled fullscreen tabs
         // - there is more than one tab, or the user has chosen to always show tabs
-        const auto isVisible = !_isInFocusMode &&
-                               (!_isFullscreen || _showTabsFullscreen) &&
-                               (_settings.GlobalSettings().ShowTabsInTitlebar() ||
-                                (_tabs.Size() > 1) ||
-                                _settings.GlobalSettings().AlwaysShowTabs());
+        const auto isVisible = IsTabRowVisible();
 
         if (_tabView)
         {

src/cascadia/TerminalApp/TerminalPage.cpp

@@ -4210,6 +4210,20 @@ namespace winrt::TerminalApp::implementation
         return _isAlwaysOnTop;
     }
 
+    bool TerminalPage::IsTabRowVisible() const
+    {
+        if (!_settings)
+        {
+            return false;
+        }
+
+        return !_isInFocusMode &&
+               (!_isFullscreen || _showTabsFullscreen) &&
+               (_settings.GlobalSettings().ShowTabsInTitlebar() ||
+                NumberOfTabs() > 1 ||
+                _settings.GlobalSettings().AlwaysShowTabs());
+    }
+
     // Method Description:
     // - Returns true if the tab row should be visible when we're in full screen
     //   state.

src/cascadia/TerminalApp/TerminalPage.h

@@ -130,6 +130,7 @@ namespace winrt::TerminalApp::implementation
         bool FocusMode() const;
         bool Fullscreen() const;
         bool AlwaysOnTop() const;
+        bool IsTabRowVisible() const;
         bool ShowTabsFullscreen() const;
         void SetShowTabsFullscreen(bool newShowTabsFullscreen);
         void SetFullscreen(bool);

src/cascadia/TerminalApp/TerminalPage.idl

@@ -62,6 +62,8 @@ namespace TerminalApp
         Boolean Fullscreen { get; };
         Boolean AlwaysOnTop { get; };
 
+        Boolean IsTabRowVisible();
+
         WindowProperties WindowProperties { get; };
         void IdentifyWindow();
 

src/cascadia/TerminalApp/TerminalWindow.cpp

@@ -1316,26 +1316,37 @@ namespace winrt::TerminalApp::implementation
 
         if (!FocusMode())
         {
-            if (!_settings.GlobalSettings().AlwaysShowTabs())
+            const auto tabsInTitlebar = _settings.GlobalSettings().ShowTabsInTitlebar();
+            const auto tabRowVisible = _root ? _root->IsTabRowVisible() :
+                                               (_settings.GlobalSettings().AlwaysShowTabs() || tabsInTitlebar);
+
+            if (!tabsInTitlebar)
             {
-                // Hide the title bar = off, Always show tabs = off.
-                static constexpr auto titlebarHeight = 10;
-                pixelSize.Height += (titlebarHeight)*scale;
+                if (tabRowVisible)
+                {
+                    // Hide the title bar = off, tab row visible. Account for
+                    // both the system title bar and the tab strip height.
+                    static constexpr auto titlebarAndTabBarHeight = 40;
+                    pixelSize.Height += (titlebarAndTabBarHeight)*scale;
+                }
+                else
+                {
+                    // Hide the title bar = off, tab row hidden. Only account
+                    // for the native title bar height.
+                    static constexpr auto titlebarHeight = 10;
+                    pixelSize.Height += (titlebarHeight)*scale;
+                }
             }
-            else if (!_settings.GlobalSettings().ShowTabsInTitlebar())
+            else if (tabRowVisible)
             {
-                // Hide the title bar = off, Always show tabs = on.
-                static constexpr auto titlebarAndTabBarHeight = 40;
-                pixelSize.Height += (titlebarAndTabBarHeight)*scale;
+                // Hide the title bar = on, tabs drawn in the title bar. Add
+                // the custom tab row height so the client area fits.
+                static constexpr auto titlebarHeight = 40;
+                pixelSize.Height += (titlebarHeight)*scale;
             }
-            // Hide the title bar = on, Always show tabs = on.
-            // In this case, we don't add any height because
-            // NonClientIslandWindow::GetTotalNonClientExclusiveSize() gets
-            // called in AppHost::_resizeWindow and it already takes title bar
-            // height into account.  In other cases above
-            // IslandWindow::GetTotalNonClientExclusiveSize() is called, and it
-            // doesn't take the title bar height into account, so we have to do
-            // the calculation manually.
+            // When tabs are hosted in the title bar but not visible we don't
+            // need to adjust the size – the non-client window chrome already
+            // accounts for it.
         }
 
         args.Width(static_cast<int32_t>(pixelSize.Width));