From 4091abd727c6b0728e93a28ca41053711be545f7 Mon Sep 17 00:00:00 2001
From: Alvin Wong <alvinhochun@gmail.com>
Date: Sat, 6 Jul 2024 05:21:43 +0800
Subject: [PATCH] Respect integrated GPU preference in Windows Settings

---
 core/os/os.h                           |  1 +
 platform/windows/os_windows.cpp        | 48 ++++++++++++++++++++++++++
 platform/windows/os_windows.h          |  1 +
 servers/rendering/rendering_device.cpp |  5 +--
 4 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/core/os/os.h b/core/os/os.h
index 63cc6ed50e6..324867c6649 100644
--- a/core/os/os.h
+++ b/core/os/os.h
@@ -137,6 +137,7 @@ public:
 	int get_display_driver_id() const { return _display_driver_id; }
 
 	virtual Vector<String> get_video_adapter_driver_info() const = 0;
+	virtual bool get_user_prefers_integrated_gpu() const { return false; }
 
 	void print_error(const char *p_function, const char *p_file, int p_line, const char *p_code, const char *p_rationale, bool p_editor_notify = false, Logger::ErrorType p_type = Logger::ERR_ERROR);
 	void print(const char *p_format, ...) _PRINTF_FORMAT_ATTRIBUTE_2_3;
diff --git a/platform/windows/os_windows.cpp b/platform/windows/os_windows.cpp
index 9025f53f42b..bceaeea01da 100644
--- a/platform/windows/os_windows.cpp
+++ b/platform/windows/os_windows.cpp
@@ -622,6 +622,54 @@ Vector<String> OS_Windows::get_video_adapter_driver_info() const {
 	return info;
 }
 
+bool OS_Windows::get_user_prefers_integrated_gpu() const {
+	// On Windows 10, the preferred GPU configured in Windows Settings is
+	// stored in the registry under the key
+	// `HKEY_CURRENT_USER\SOFTWARE\Microsoft\DirectX\UserGpuPreferences`
+	// with the name being the EXE path. The value is in the form of
+	// `GpuPreference=1;`, with the value being 1 for integrated GPU and 2
+	// for discrete GPU. On Windows 11, there may be more flags, separated
+	// by semicolons.
+
+	WCHAR exe_path[32768];
+	if (GetModuleFileNameW(nullptr, exe_path, sizeof(exe_path) / sizeof(exe_path[0])) >= sizeof(exe_path) / sizeof(exe_path[0])) {
+		// Paths should never be longer than 32767, but just in case.
+		return false;
+	}
+
+	LPCWSTR subkey = L"SOFTWARE\\Microsoft\\DirectX\\UserGpuPreferences";
+	HKEY hkey = nullptr;
+	LSTATUS result = RegOpenKeyExW(HKEY_CURRENT_USER, subkey, 0, KEY_READ, &hkey);
+	if (result != ERROR_SUCCESS) {
+		return false;
+	}
+
+	DWORD size = 0;
+	result = RegGetValueW(hkey, nullptr, exe_path, RRF_RT_REG_SZ, nullptr, nullptr, &size);
+	if (result != ERROR_SUCCESS || size == 0) {
+		RegCloseKey(hkey);
+		return false;
+	}
+
+	Vector<WCHAR> buffer;
+	buffer.resize(size / sizeof(WCHAR));
+	result = RegGetValueW(hkey, nullptr, exe_path, RRF_RT_REG_SZ, nullptr, (LPBYTE)buffer.ptrw(), &size);
+	if (result != ERROR_SUCCESS) {
+		RegCloseKey(hkey);
+		return false;
+	}
+
+	RegCloseKey(hkey);
+	const String flags = String::utf16((const char16_t *)buffer.ptr(), size / sizeof(WCHAR));
+
+	for (const String &flag : flags.split(";", false)) {
+		if (flag == "GpuPreference=1") {
+			return true;
+		}
+	}
+	return false;
+}
+
 OS::DateTime OS_Windows::get_datetime(bool p_utc) const {
 	SYSTEMTIME systemtime;
 	if (p_utc) {
diff --git a/platform/windows/os_windows.h b/platform/windows/os_windows.h
index b6a21ed42dd..9c7b98d7fdd 100644
--- a/platform/windows/os_windows.h
+++ b/platform/windows/os_windows.h
@@ -172,6 +172,7 @@ public:
 	virtual String get_version() const override;
 
 	virtual Vector<String> get_video_adapter_driver_info() const override;
+	virtual bool get_user_prefers_integrated_gpu() const override;
 
 	virtual void initialize_joypads() override {}
 
diff --git a/servers/rendering/rendering_device.cpp b/servers/rendering/rendering_device.cpp
index c65d3bec950..27e07969762 100644
--- a/servers/rendering/rendering_device.cpp
+++ b/servers/rendering/rendering_device.cpp
@@ -82,11 +82,12 @@ static String _get_device_type_name(const RenderingContextDriver::Device &p_devi
 }
 
 static uint32_t _get_device_type_score(const RenderingContextDriver::Device &p_device) {
+	static const bool prefer_integrated = OS::get_singleton()->get_user_prefers_integrated_gpu();
 	switch (p_device.type) {
 		case RenderingContextDriver::DEVICE_TYPE_INTEGRATED_GPU:
-			return 4;
+			return prefer_integrated ? 5 : 4;
 		case RenderingContextDriver::DEVICE_TYPE_DISCRETE_GPU:
-			return 5;
+			return prefer_integrated ? 4 : 5;
 		case RenderingContextDriver::DEVICE_TYPE_VIRTUAL_GPU:
 			return 3;
 		case RenderingContextDriver::DEVICE_TYPE_CPU: