conhost: Make screen readers announce search results

.github/actions/spelling/expect/expect.txt

@@ -1019,6 +1019,8 @@ msft
 MSGCMDLINEF
 MSGF
 MSGFILTER
+MSGFINDNORESULT
+MSGFINDRESULT
 MSGFLG
 MSGMARKMODE
 MSGSCROLLMODE

src/host/AccessibilityNotifier.cpp

@@ -4,6 +4,9 @@
 #include "precomp.h"
 #include "AccessibilityNotifier.h"
 
+#include "resource.h"
+#include "utils.hpp"
+
 #include "../types/inc/convert.hpp"
 #include "../interactivity/inc/ServiceLocator.hpp"
 
@@ -183,6 +186,69 @@ void AccessibilityNotifier::SelectionChanged() noexcept
     }
 }
 
+// Announces the state of the Find dialog's search results to screen readers.
+// `index` is the 0-based index of the current match and `count` is the total number of matches.
+//
+// Unlike the other members of this class, this is emitted synchronously and isn't batched.
+void AccessibilityNotifier::AnnounceSearchResults(ptrdiff_t index, size_t count) noexcept
+try
+{
+    const auto provider = _uiaProvider.load(std::memory_order_relaxed);
+    if (!provider)
+    {
+        return;
+    }
+
+    std::wstring format;
+    std::wstring announcement;
+
+    if (count == 0)
+    {
+        // No results found
+        _LoadString(ID_CONSOLE_MSGFINDNORESULT, announcement);
+    }
+    else
+    {
+        // Results found, announce as 1-based index of total ("2 of 5")
+        _LoadString(ID_CONSOLE_MSGFINDRESULT, format);
+
+        const auto position = std::clamp<size_t>(gsl::narrow_cast<size_t>(std::max<ptrdiff_t>(index, 0)) + 1, 1, count);
+
+        // The resource uses positional inserts (%1, %2) so that translations can reorder them
+        const DWORD_PTR args[]{
+            gsl::narrow_cast<DWORD_PTR>(position),
+            gsl::narrow_cast<DWORD_PTR>(count),
+        };
+        wil::unique_hlocal_string formatted;
+        const auto length = FormatMessageW(
+            FORMAT_MESSAGE_FROM_STRING | FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_ARGUMENT_ARRAY,
+            format.c_str(),
+            0,
+            0,
+            reinterpret_cast<LPWSTR>(formatted.addressof()),
+            0,
+            reinterpret_cast<va_list*>(const_cast<DWORD_PTR*>(&args[0])));
+        if (length == 0)
+        {
+            LOG_LAST_ERROR();
+            return;
+        }
+        announcement.assign(formatted.get(), length);
+    }
+
+    if (announcement.empty())
+    {
+        return;
+    }
+
+    if (const auto bstrAnnouncement = wil::make_bstr_nothrow(announcement.c_str()))
+    {
+        static const auto bstrActivityId = wil::make_bstr_nothrow(L"ConhostSearchResultAnnouncement");
+        LOG_IF_FAILED(UiaRaiseNotificationEvent(provider, NotificationKind_ActionCompleted, NotificationProcessing_ImportantMostRecent, bstrAnnouncement.get(), bstrActivityId.get()));
+    }
+}
+CATCH_LOG()
+
 bool AccessibilityNotifier::WantsRegionChangedEvents() const noexcept
 {
     // See RegionChanged().

src/host/AccessibilityNotifier.h

@@ -26,6 +26,7 @@ namespace Microsoft::Console
 
         void CursorChanged(til::point position, bool activeSelection) noexcept;
         void SelectionChanged() noexcept;
+        void AnnounceSearchResults(ptrdiff_t index, size_t count) noexcept;
         bool WantsRegionChangedEvents() const noexcept;
         void RegionChanged(til::point begin, til::point end) noexcept;
         void ScrollBuffer(til::CoordType delta) noexcept;

src/host/res.rc

@@ -61,6 +61,11 @@ BEGIN
 
     ID_CONSOLE_FMT_WINDOWTITLE, "%s%s"
 
+/* Find dialog screen reader announcements. %1 is the 1-based index of the current
+   match, %2 is the total number of matches. */
+    ID_CONSOLE_MSGFINDRESULT,   "%1!d! of %2!d!"
+    ID_CONSOLE_MSGFINDNORESULT, "No results"
+
 /* Menu items that replace the standard ones. These don't have the accelerators */
     SC_CLOSE,       "&Close"
 

src/host/resource.h

@@ -28,6 +28,8 @@ Author(s):
 #define ID_CONSOLE_MSGMARKMODE           0x100C
 #define ID_CONSOLE_MSGSCROLLMODE         0x100D
 #define ID_CONSOLE_FMT_WINDOWTITLE       0x100E
+#define ID_CONSOLE_MSGFINDRESULT         0x100F
+#define ID_CONSOLE_MSGFINDNORESULT       0x1010
 
 // Menu Item strings
 #define ID_CONSOLE_COPY         0xFFF0

src/interactivity/win32/find.cpp

@@ -63,6 +63,8 @@ INT_PTR CALLBACK FindDialogProc(HWND hWnd, UINT Message, WPARAM wParam, LPARAM l
                 searcher.FindNext(reverse);
             }
 
+            ServiceLocator::LocateGlobals().accessibilityNotifier.AnnounceSearchResults(searcher.CurrentMatch(), searcher.Results().size());
+
             if (searcher.SelectCurrent())
             {
                 return TRUE;

src/interactivity/win32/resource.h

@@ -25,6 +25,8 @@ Author(s):
 #define ID_CONSOLE_MSGMARKMODE           0x100C
 #define ID_CONSOLE_MSGSCROLLMODE         0x100D
 #define ID_CONSOLE_FMT_WINDOWTITLE       0x100E
+#define ID_CONSOLE_MSGFINDRESULT         0x100F
+#define ID_CONSOLE_MSGFINDNORESULT       0x1010
 
 // Menu Item strings
 #define ID_CONSOLE_COPY         0xFFF0