Make the SearchBox announce if it found results or not (#12301)

Basically, this is the same as #12266, but for the `SearchBoxControl`. Trickily, the ControlCore is the one that knows if there were search results, but the TermControl has to be the one to announce it.

* [x] Will take care of #11973 once a11y team confirms
* [x] Tested manually with Narrator
* [x] Resolves a part of #6319, which I'm repurposing just to displaying the number of results in general. 
* See also #3920

src/cascadia/TerminalControl/ControlCore.cpp

@@ -1316,12 +1316,18 @@ namespace winrt::Microsoft::Terminal::Control::implementation
 
         ::Search search(*GetUiaData(), text.c_str(), direction, sensitivity);
         auto lock = _terminal->LockForWriting();
-        if (search.FindNext())
+        const bool foundMatch{ search.FindNext() };
+        if (foundMatch)
         {
             _terminal->SetBlockSelection(false);
             search.Select();
             _renderer->TriggerSelection();
         }
+
+        // Raise a FoundMatch event, which the control will use to notify
+        // narrator if there was any results in the buffer
+        auto foundResults = winrt::make_self<implementation::FoundResultsArgs>(foundMatch);
+        _FoundMatchHandlers(*this, *foundResults);
     }
 
     // Method Description:

src/cascadia/TerminalControl/ControlCore.h

@@ -191,6 +191,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         TYPED_EVENT(RaiseNotice,               IInspectable, Control::NoticeEventArgs);
         TYPED_EVENT(TransparencyChanged,       IInspectable, Control::TransparencyChangedEventArgs);
         TYPED_EVENT(ReceivedOutput,            IInspectable, IInspectable);
+        TYPED_EVENT(FoundMatch,                IInspectable, Control::FoundResultsArgs);
         // clang-format on
 
     private:

src/cascadia/TerminalControl/ControlCore.idl

@@ -119,6 +119,7 @@ namespace Microsoft.Terminal.Control
         event Windows.Foundation.TypedEventHandler<Object, NoticeEventArgs> RaiseNotice;
         event Windows.Foundation.TypedEventHandler<Object, TransparencyChangedEventArgs> TransparencyChanged;
         event Windows.Foundation.TypedEventHandler<Object, Object> ReceivedOutput;
+        event Windows.Foundation.TypedEventHandler<Object, FoundResultsArgs> FoundMatch;
 
     };
 }

src/cascadia/TerminalControl/EventArgs.cpp

@@ -11,3 +11,4 @@
 #include "ScrollPositionChangedArgs.g.cpp"
 #include "RendererWarningArgs.g.cpp"
 #include "TransparencyChangedEventArgs.g.cpp"
+#include "FoundResultsArgs.g.cpp"

src/cascadia/TerminalControl/EventArgs.h

@@ -11,6 +11,7 @@
 #include "ScrollPositionChangedArgs.g.h"
 #include "RendererWarningArgs.g.h"
 #include "TransparencyChangedEventArgs.g.h"
+#include "FoundResultsArgs.g.h"
 
 namespace winrt::Microsoft::Terminal::Control::implementation
 {
@@ -133,4 +134,15 @@ namespace winrt::Microsoft::Terminal::Control::implementation
 
         WINRT_PROPERTY(double, Opacity);
     };
+
+    struct FoundResultsArgs : public FoundResultsArgsT<FoundResultsArgs>
+    {
+    public:
+        FoundResultsArgs(const bool foundMatch) :
+            _FoundMatch(foundMatch)
+        {
+        }
+
+        WINRT_PROPERTY(bool, FoundMatch);
+    };
 }

src/cascadia/TerminalControl/EventArgs.idl

@@ -68,4 +68,10 @@ namespace Microsoft.Terminal.Control
     {
         Double Opacity { get; };
     }
+
+
+    runtimeclass FoundResultsArgs
+    {
+        Boolean FoundMatch { get; };
+    }
 }

src/cascadia/TerminalControl/Resources/en-US/Resources.resw

@@ -200,4 +200,12 @@ Please either install the missing font or choose another one.</value>
   <data name="TermControlReadOnly" xml:space="preserve">
     <value>Read-only mode is enabled.</value>
   </data>
+  <data name="SearchBox_MatchesAvailable" xml:space="preserve">
+    <value>Results found</value>
+    <comment>Announced to a screen reader when the user searches for some text and there are matches for that text in the terminal.</comment>
+  </data>
+  <data name="SearchBox_NoMatches" xml:space="preserve">
+    <value>No results found</value>
+    <comment>Announced to a screen reader when the user searches for some text and there are no matches for that text in the terminal.</comment>
+  </data>
 </root>

src/cascadia/TerminalControl/TermControl.cpp

@@ -82,6 +82,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         _core.TransparencyChanged({ this, &TermControl::_coreTransparencyChanged });
         _core.RaiseNotice({ this, &TermControl::_coreRaisedNotice });
         _core.HoveredHyperlinkChanged({ this, &TermControl::_hoveredHyperlinkChanged });
+        _core.FoundMatch({ this, &TermControl::_coreFoundMatch });
         _interactivity.OpenHyperlink({ this, &TermControl::_HyperlinkHandler });
         _interactivity.ScrollPositionChanged({ this, &TermControl::_ScrollPositionChanged });
 
@@ -2747,4 +2748,28 @@ namespace winrt::Microsoft::Terminal::Control::implementation
     {
         return _core.Opacity();
     }
+
+    // Method Description:
+    // - Called when the core raises a FoundMatch event. That's done in response
+    //   to us starting a search query with ControlCore::Search.
+    // - The args will tell us if there were or were not any results for that
+    //   particular search. We'll use that to control what to announce to
+    //   Narrator. When we have more elaborate search information to report, we
+    //   may want to report that here. (see GH #3920)
+    // Arguments:
+    // - args: contains information about the results that were or were not found.
+    // Return Value:
+    // - <none>
+    void TermControl::_coreFoundMatch(const IInspectable& /*sender*/, const Control::FoundResultsArgs& args)
+    {
+        if (auto automationPeer{ Automation::Peers::FrameworkElementAutomationPeer::FromElement(*this) })
+        {
+            automationPeer.RaiseNotificationEvent(
+                Automation::Peers::AutomationNotificationKind::ActionCompleted,
+                Automation::Peers::AutomationNotificationProcessing::ImportantMostRecent,
+                args.FoundMatch() ? RS_(L"SearchBox_MatchesAvailable") : RS_(L"SearchBox_NoMatches"), // what to announce if results were found
+                L"SearchBoxResultAnnouncement" /* unique name for this group of notifications */);
+        }
+    }
+
 }

src/cascadia/TerminalControl/TermControl.h

@@ -275,6 +275,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         winrt::fire_and_forget _coreTransparencyChanged(IInspectable sender, Control::TransparencyChangedEventArgs args);
         void _coreRaisedNotice(const IInspectable& s, const Control::NoticeEventArgs& args);
         void _coreWarningBell(const IInspectable& sender, const IInspectable& args);
+        void _coreFoundMatch(const IInspectable& sender, const Control::FoundResultsArgs& args);
     };
 }