From 87fc91477250e033c8eb3717abfc0025639f5149 Mon Sep 17 00:00:00 2001
From: Leonard Hecker <lhecker@microsoft.com>
Date: Fri, 30 Aug 2024 13:59:09 +0200
Subject: [PATCH] wip

---
 src/internal/stubs.cpp              | 27 +++++++++++++++++++++++++--
 src/types/ThemeUtils.cpp            | 19 -------------------
 src/types/inc/ThemeUtils.h          |  8 --------
 src/types/lib/types.vcxproj         |  2 --
 src/types/lib/types.vcxproj.filters |  6 ------
 src/types/sources.inc               |  1 -
 6 files changed, 25 insertions(+), 38 deletions(-)
 delete mode 100644 src/types/ThemeUtils.cpp
 delete mode 100644 src/types/inc/ThemeUtils.h

diff --git a/src/internal/stubs.cpp b/src/internal/stubs.cpp
index f92f409696..224c6b1c38 100644
--- a/src/internal/stubs.cpp
+++ b/src/internal/stubs.cpp
@@ -3,6 +3,9 @@
 
 #include "precomp.h"
 
+#include <dwmapi.h>
+#include <uxtheme.h>
+
 #include "../inc/conint.h"
 
 using namespace Microsoft::Console::Internal;
@@ -21,7 +24,27 @@ using namespace Microsoft::Console::Internal;
     return S_OK;
 }
 
-[[nodiscard]] HRESULT Theming::TrySetDarkMode(HWND /*hwnd*/) noexcept
+[[nodiscard]] HRESULT Theming::TrySetDarkMode(HWND hwnd) noexcept
 {
-    return S_FALSE;
+    static constexpr auto subKey = LR"(SOFTWARE\Microsoft\Windows\CurrentVersion\Themes\Personalize)";
+    static constexpr auto get = [](HKEY key, const wchar_t* value, DWORD& data) {
+        DWORD dataType = 0;
+        DWORD size = sizeof(data);
+        return RegGetValueW(key, subKey, value, RRF_RT_REG_DWORD, &dataType, &data, &size);
+    };
+
+    // This is the approach that WinUI3 used in its initial source code release at the time of writing.
+    DWORD useLightTheme = 0;
+    if (get(HKEY_CURRENT_USER, L"AppsUseLightTheme", useLightTheme) != ERROR_SUCCESS)
+    {
+        if (get(HKEY_LOCAL_MACHINE, L"SystemUsesLightTheme", useLightTheme) != ERROR_SUCCESS)
+        {
+            useLightTheme = 0;
+        }
+    }
+
+    const BOOL useDarkMode = useLightTheme == 0;
+    LOG_IF_FAILED(SetWindowTheme(hwnd, useLightTheme ? L"" : L"DarkMode_Explorer", nullptr));
+    LOG_IF_FAILED(DwmSetWindowAttribute(hwnd, DWMWA_USE_IMMERSIVE_DARK_MODE, &useDarkMode, sizeof(useDarkMode)));
+    return S_OK;
 }
diff --git a/src/types/ThemeUtils.cpp b/src/types/ThemeUtils.cpp
deleted file mode 100644
index ecc4af6a34..0000000000
--- a/src/types/ThemeUtils.cpp
+++ /dev/null
@@ -1,19 +0,0 @@
-#include "precomp.h"
-#include "inc/ThemeUtils.h"
-
-namespace Microsoft::Console::ThemeUtils
-{
-    // Routine Description:
-    // - Attempts to enable/disable the dark mode on the frame of a window.
-    // Arguments:
-    // - hwnd: handle to the window to change
-    // - enabled: whether to enable or not the dark mode on the window's frame
-    // Return Value:
-    // - S_OK or suitable HRESULT from DWM engines.
-    [[nodiscard]] HRESULT SetWindowFrameDarkMode(HWND /* hwnd */, bool /* enabled */) noexcept
-    {
-        // TODO:GH #3425 implement the new DWM API and change
-        //  src/interactivity/win32/windowtheme.cpp to use it.
-        return S_OK;
-    }
-}
diff --git a/src/types/inc/ThemeUtils.h b/src/types/inc/ThemeUtils.h
deleted file mode 100644
index ffe972301f..0000000000
--- a/src/types/inc/ThemeUtils.h
+++ /dev/null
@@ -1,8 +0,0 @@
-#pragma once
-
-#include <Windows.h>
-
-namespace Microsoft::Console::ThemeUtils
-{
-    [[nodiscard]] HRESULT SetWindowFrameDarkMode(HWND hwnd, bool enabled) noexcept;
-}
diff --git a/src/types/lib/types.vcxproj b/src/types/lib/types.vcxproj
index 90756e2be2..62c90830ba 100644
--- a/src/types/lib/types.vcxproj
+++ b/src/types/lib/types.vcxproj
@@ -18,7 +18,6 @@
     <ClCompile Include="..\GlyphWidth.cpp" />
     <ClCompile Include="..\ScreenInfoUiaProviderBase.cpp" />
     <ClCompile Include="..\sgrStack.cpp" />
-    <ClCompile Include="..\ThemeUtils.cpp" />
     <ClCompile Include="..\UiaTextRangeBase.cpp" />
     <ClCompile Include="..\UiaTracing.cpp" />
     <ClCompile Include="..\TermControlUiaTextRange.cpp" />
@@ -38,7 +37,6 @@
     <ClInclude Include="..\inc\GlyphWidth.hpp" />
     <ClInclude Include="..\inc\IInputEvent.hpp" />
     <ClInclude Include="..\inc\sgrStack.hpp" />
-    <ClInclude Include="..\inc\ThemeUtils.h" />
     <ClInclude Include="..\inc\utils.hpp" />
     <ClInclude Include="..\inc\Viewport.hpp" />
     <ClInclude Include="..\IUiaEventDispatcher.h" />
diff --git a/src/types/lib/types.vcxproj.filters b/src/types/lib/types.vcxproj.filters
index 2ecdd122c9..84c26d80b1 100644
--- a/src/types/lib/types.vcxproj.filters
+++ b/src/types/lib/types.vcxproj.filters
@@ -42,9 +42,6 @@
     <ClCompile Include="..\UiaTextRangeBase.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
-    <ClCompile Include="..\ThemeUtils.cpp">
-      <Filter>Source Files</Filter>
-    </ClCompile>
     <ClCompile Include="..\sgrStack.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
@@ -107,9 +104,6 @@
     <ClInclude Include="..\inc\utils.hpp">
       <Filter>Header Files</Filter>
     </ClInclude>
-    <ClInclude Include="..\inc\ThemeUtils.h">
-      <Filter>Header Files</Filter>
-    </ClInclude>
     <ClInclude Include="..\inc\sgrStack.hpp">
       <Filter>Header Files</Filter>
     </ClInclude>
diff --git a/src/types/sources.inc b/src/types/sources.inc
index 44f252a2a1..afc6577456 100644
--- a/src/types/sources.inc
+++ b/src/types/sources.inc
@@ -35,7 +35,6 @@ SOURCES= \
     ..\convert.cpp \
     ..\colorTable.cpp \
     ..\utils.cpp \
-    ..\ThemeUtils.cpp \
     ..\ScreenInfoUiaProviderBase.cpp \
     ..\sgrStack.cpp \
     ..\UiaTextRangeBase.cpp \