From af358b704987f3b4d370c203a5de5bef88b3f1cf Mon Sep 17 00:00:00 2001
From: Mike Griese <migrie@microsoft.com>
Date: Wed, 20 Sep 2023 15:47:25 -0500
Subject: [PATCH] Don't update the settings, unless the theme actually changed
 (#16004)
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`ImmersiveColorSet` gets sent more often than just on a theme change. It notably gets sent when the PC is locked, or the UAC prompt opens.

## Validation Steps Performed

Tested manually by setting the font to `garbo`and:
* locking, then logging back in. No dialog ✅
* UAC via run dialog + `regedit`. No dialog ✅
* Actually changing the OS theme. Dialog ✅

Closes #15732

(cherry picked from commit c1bdcf8b9732fab115275416557712878992e04a)
Service-Card-Id: 90600308
Service-Version: 1.18
---
 src/cascadia/WindowsTerminal/IslandWindow.cpp | 13 ++++++++++++-
 src/cascadia/WindowsTerminal/IslandWindow.h   |  1 +
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/cascadia/WindowsTerminal/IslandWindow.cpp b/src/cascadia/WindowsTerminal/IslandWindow.cpp
index 87ec8d5dbce..9bea05acfe9 100644
--- a/src/cascadia/WindowsTerminal/IslandWindow.cpp
+++ b/src/cascadia/WindowsTerminal/IslandWindow.cpp
@@ -199,6 +199,8 @@ void IslandWindow::_HandleCreateWindow(const WPARAM, const LPARAM lParam) noexce
     UpdateWindow(_window.get());
 
     UpdateWindowIconForActiveMetrics(_window.get());
+
+    _currentSystemThemeIsDark = Theme::IsSystemInDarkTheme();
 }
 
 // Method Description:
@@ -745,7 +747,16 @@ long IslandWindow::_calculateTotalSize(const bool isWidth, const long clientSize
             // themes, color schemes that might depend on the OS theme
             if (param == L"ImmersiveColorSet")
             {
-                _UpdateSettingsRequestedHandlers();
+                // GH#15732: Don't update the settings, unless the theme
+                // _actually_ changed. ImmersiveColorSet gets sent more often
+                // than just on a theme change. It notably gets sent when the PC
+                // is locked, or the UAC prompt opens.
+                auto isCurrentlyDark = Theme::IsSystemInDarkTheme();
+                if (isCurrentlyDark != _currentSystemThemeIsDark)
+                {
+                    _currentSystemThemeIsDark = isCurrentlyDark;
+                    _UpdateSettingsRequestedHandlers();
+                }
             }
         }
         break;
diff --git a/src/cascadia/WindowsTerminal/IslandWindow.h b/src/cascadia/WindowsTerminal/IslandWindow.h
index c0abd343e1b..eee013c529a 100644
--- a/src/cascadia/WindowsTerminal/IslandWindow.h
+++ b/src/cascadia/WindowsTerminal/IslandWindow.h
@@ -117,6 +117,7 @@ class IslandWindow :
     RECT _rcWindowBeforeFullscreen{};
     RECT _rcWorkBeforeFullscreen{};
     UINT _dpiBeforeFullscreen{ 96 };
+    bool _currentSystemThemeIsDark{ true };
 
     void _coldInitialize();
     void _warmInitialize();