Add a fun new preview text in the SUI, enable the cursor (#15363)

Our existing preview text was not very helpful in learning how different
settings impacted the display of text in Terminal.

This new preview text contains:
* Bold text, which is controlled by intenseTextStyle
* Colors
* Emoji
* A cursor, which overlaps a single character to show inversion behavior

(cherry picked from commit fbe45fafb5)
Service-Card-Id: 89230301
Service-Version: 1.17

src/cascadia/TerminalControl/TermControl.cpp

@@ -874,7 +874,11 @@ namespace winrt::Microsoft::Terminal::Control::implementation
             // _cursorTimer doesn't exist, and it would never turn on the
             // cursor. To mitigate, we'll initialize the cursor's 'on' state
             // with `_focused` here.
-            _core.CursorOn(_focused);
+            _core.CursorOn(_focused || DisplayCursorWhileBlurred);
+            if (DisplayCursorWhileBlurred)
+            {
+                _cursorTimer->Start();
+            }
         }
         else
         {
@@ -1749,7 +1753,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
             TSFInputControl().NotifyFocusLeave();
         }
 
-        if (_cursorTimer)
+        if (_cursorTimer && !DisplayCursorWhileBlurred)
         {
             _cursorTimer->Stop();
             _core.CursorOn(false);

src/cascadia/TerminalControl/TermControl.h

@@ -165,6 +165,9 @@ namespace winrt::Microsoft::Terminal::Control::implementation
 
         WINRT_OBSERVABLE_PROPERTY(winrt::Windows::UI::Xaml::Media::Brush, BackgroundBrush, _PropertyChangedHandlers, nullptr);
 
+    public:
+        til::property<bool> DisplayCursorWhileBlurred{ false };
+
     private:
         friend struct TermControlT<TermControl>; // friend our parent so it can bind private event handlers
 

src/cascadia/TerminalControl/TermControl.idl

@@ -98,6 +98,8 @@ namespace Microsoft.Terminal.Control
         // opacity set by the settings should call this instead.
         Double BackgroundOpacity { get; };
 
+        Boolean DisplayCursorWhileBlurred;
+
         Windows.UI.Xaml.Media.Brush BackgroundBrush { get; };
 
         void ColorSelection(SelectionColor fg, SelectionColor bg, Microsoft.Terminal.Core.MatchMode matchMode);

src/cascadia/TerminalSettingsEditor/PreviewConnection.cpp

@@ -8,7 +8,17 @@
 using namespace ::winrt::Microsoft::Terminal::TerminalConnection;
 using namespace ::winrt::Windows::Foundation;
 
-static constexpr std::wstring_view PreviewText{ L"Windows Terminal\r\nCopyright (c) Microsoft Corporation\r\n\nC:\\Windows\\Terminal> " };
+// clang-format off
+static constexpr std::wstring_view PreviewText{
+    L"Windows Terminal\r\n"
+    L"C:\\> \x1b[93m" L"git\x1b[m diff \x1b[90m-w\x1b[m\r\n"
+    L"\x1b[1m" L"diff --git a/win b/win\x1b[m\r\n"
+    L"\x1b[36m@@ -1 +1 @@\x1b[m\r\n"
+    L"\x1b[31m-    Windows Console\x1b[m\r\n"
+    L"\x1b[32m-    Windows Terminal!\x1b[m\r\n"
+    L"C:\\> \x1b[93mWrite-Host \x1b[36m\"\xd83e\xde9f!\"\x1b[1D\x1b[m"
+};
+// clang-format on
 
 namespace winrt::Microsoft::Terminal::Settings::Editor::implementation
 {
@@ -16,8 +26,6 @@ namespace winrt::Microsoft::Terminal::Settings::Editor::implementation
 
     void PreviewConnection::Start() noexcept
     {
-        // First send a sequence to disable cursor blinking
-        _TerminalOutputHandlers(L"\x1b[?12l");
         // Send the preview text
         _TerminalOutputHandlers(PreviewText);
     }

src/cascadia/TerminalSettingsEditor/Profiles_Appearance.cpp

@@ -39,6 +39,7 @@ namespace winrt::Microsoft::Terminal::Settings::Editor::implementation
             _previewControl = Control::TermControl(settings, settings, make<PreviewConnection>());
             _previewControl.IsEnabled(false);
             _previewControl.AllowFocusWhenDisabled(false);
+            _previewControl.DisplayCursorWhileBlurred(true);
             ControlPreview().Child(_previewControl);
         }
 

src/cascadia/TerminalSettingsEditor/Profiles_Appearance.xaml

@@ -47,8 +47,8 @@
                 <!--  Control Preview  -->
                 <Border MaxWidth="{StaticResource StandardControlMaxWidth}">
                     <Border x:Name="ControlPreview"
-                            Width="350"
+                            Width="400"
-                            Height="160"
+                            Height="180"
                             Margin="0,0,0,12"
                             HorizontalAlignment="Left"
                             BorderBrush="{ThemeResource SystemControlForegroundBaseMediumLowBrush}"