Send an updated cursor position at the end of writing a run (#12210)

I can find the commit where this regressed tomorrow if needed. In #10685 we stopped emitting these notifications while we were deferring cursor drawing. We however forgot to send the notification at the end of the defer.

This likely has a small perf impact. We however do need these cursor position events for IMEs to be able to track the cursor position (and low key for #10821)

* [x] regressed in #10685
* [x] Closes #11170
* [x] I work here
* [x] Tests added

(cherry picked from commit 01fd714)

src/cascadia/TerminalCore/Terminal.cpp

@@ -425,7 +425,21 @@ void Terminal::Write(std::wstring_view stringView)
 {
     auto lock = LockForWriting();
 
+    auto& cursor = _buffer->GetCursor();
+    const til::point cursorPosBefore{ cursor.GetPosition() };
+
     _stateMachine->ProcessString(stringView);
+
+    const til::point cursorPosAfter{ cursor.GetPosition() };
+
+    // Firing the CursorPositionChanged event is very expensive so we try not to
+    // do that when the cursor does not need to be redrawn. We don't do this
+    // inside _AdjustCursorPosition, only once we're done writing the whole run
+    // of output.
+    if (cursorPosBefore != cursorPosAfter)
+    {
+        _NotifyTerminalCursorPositionChanged();
+    }
 }
 
 void Terminal::WritePastedText(std::wstring_view stringView)
@@ -1087,13 +1101,6 @@ void Terminal::_AdjustCursorPosition(const COORD proposedPosition)
         COORD delta{ 0, -rowsPushedOffTopOfBuffer };
         _buffer->GetRenderTarget().TriggerScroll(&delta);
     }
-
-    // Firing the CursorPositionChanged event is very expensive so we try not to do that when
-    // the cursor does not need to be redrawn.
-    if (!cursor.IsDeferDrawing())
-    {
-        _NotifyTerminalCursorPositionChanged();
-    }
 }
 
 void Terminal::UserScrollViewport(const int viewTop)

src/cascadia/UnitTests_TerminalCore/TerminalBufferTests.cpp

@@ -51,6 +51,8 @@ class TerminalCoreUnitTests::TerminalBufferTests final
 
     TEST_METHOD(TestGetReverseTab);
 
+    TEST_METHOD(TestCursorNotifications);
+
     TEST_METHOD_SETUP(MethodSetup)
     {
         // STEP 1: Set up the Terminal
@@ -592,3 +594,43 @@ void TerminalBufferTests::TestGetReverseTab()
                          L"Cursor adjusted to last item in the sample list from position beyond end.");
     }
 }
+
+void TerminalBufferTests::TestCursorNotifications()
+{
+    // Test for GH#11170
+
+    // Suppress test exceptions. If they occur in the lambda, they'll just crash
+    // TAEF, which is annoying.
+    const WEX::TestExecution::DisableVerifyExceptions disableExceptionsScope;
+
+    bool callbackWasCalled = false;
+    int expectedCallbacks = 0;
+    auto cb = [&expectedCallbacks, &callbackWasCalled]() mutable {
+        Log::Comment(L"Callback triggered");
+        callbackWasCalled = true;
+        expectedCallbacks--;
+        VERIFY_IS_GREATER_THAN_OR_EQUAL(expectedCallbacks, 0);
+    };
+    term->_pfnCursorPositionChanged = cb;
+
+    // The exact number of callbacks here is fungible, if need be.
+
+    expectedCallbacks = 1;
+    callbackWasCalled = false;
+    term->Write(L"Foo");
+    VERIFY_ARE_EQUAL(0, expectedCallbacks);
+    VERIFY_IS_TRUE(callbackWasCalled);
+
+    expectedCallbacks = 1;
+    callbackWasCalled = false;
+    term->Write(L"Foo\r\nBar");
+    VERIFY_ARE_EQUAL(0, expectedCallbacks);
+    VERIFY_IS_TRUE(callbackWasCalled);
+
+    expectedCallbacks = 2; // One for each Write
+    callbackWasCalled = false;
+    term->Write(L"Foo\r\nBar");
+    term->Write(L"Foo\r\nBar");
+    VERIFY_ARE_EQUAL(0, expectedCallbacks);
+    VERIFY_IS_TRUE(callbackWasCalled);
+}