From fb69aecb19776e7fc07bb92d9b90f27be8f3b4fe Mon Sep 17 00:00:00 2001
From: Chester Liu <skyline75489@outlook.com>
Date: Tue, 20 Jul 2021 22:05:45 +0800
Subject: [PATCH] Defer cursor winrt event triggering (#10685)

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## Summary of the Pull Request

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## References

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## PR Checklist
* [X] Supports #10563
* [ ] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [ ] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [ ] Schema updated.
* [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

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## Detailed Description of the Pull Request / Additional comments

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## Validation Steps Performed
---
 src/buffer/out/cursor.cpp              | 5 +++++
 src/buffer/out/cursor.h                | 1 +
 src/cascadia/TerminalCore/Terminal.cpp | 7 ++++++-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/buffer/out/cursor.cpp b/src/buffer/out/cursor.cpp
index 46f0208f8..1d050a215 100644
--- a/src/buffer/out/cursor.cpp
+++ b/src/buffer/out/cursor.cpp
@@ -315,6 +315,11 @@ void Cursor::StartDeferDrawing() noexcept
     _fDeferCursorRedraw = true;
 }
 
+bool Cursor::IsDeferDrawing() noexcept
+{
+    return _fDeferCursorRedraw;
+}
+
 void Cursor::EndDeferDrawing() noexcept
 {
     if (_fHaveDeferredCursorRedraw)
diff --git a/src/buffer/out/cursor.h b/src/buffer/out/cursor.h
index 7ac93359a..dbd05f535 100644
--- a/src/buffer/out/cursor.h
+++ b/src/buffer/out/cursor.h
@@ -55,6 +55,7 @@ public:
     const COLORREF GetColor() const noexcept;
 
     void StartDeferDrawing() noexcept;
+    bool IsDeferDrawing() noexcept;
     void EndDeferDrawing() noexcept;
 
     void SetHasMoved(const bool fHasMoved) noexcept;
diff --git a/src/cascadia/TerminalCore/Terminal.cpp b/src/cascadia/TerminalCore/Terminal.cpp
index 666068cb0..9cc4aea47 100644
--- a/src/cascadia/TerminalCore/Terminal.cpp
+++ b/src/cascadia/TerminalCore/Terminal.cpp
@@ -1070,7 +1070,12 @@ void Terminal::_AdjustCursorPosition(const COORD proposedPosition)
         _buffer->GetRenderTarget().TriggerScroll(&delta);
     }
 
-    _NotifyTerminalCursorPositionChanged();
+    // 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)