Add `get_screen_refresh_rate()` to OS

This method can be used to get the refresh rate of a given screen.
It is supported on Windows, macOS, Linux, Android and iOS (but not
HTML5).

core/bind/core_bind.cpp

@@ -311,6 +311,10 @@ float _OS::get_screen_max_scale() const {
 	return OS::get_singleton()->get_screen_max_scale();
 }
 
+float _OS::get_screen_refresh_rate(int p_screen) const {
+	return OS::get_singleton()->get_screen_refresh_rate();
+}
+
 Point2 _OS::get_window_position() const {
 	return OS::get_singleton()->get_window_position();
 }
@@ -1267,6 +1271,7 @@ void _OS::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("get_screen_dpi", "screen"), &_OS::get_screen_dpi, DEFVAL(-1));
 	ClassDB::bind_method(D_METHOD("get_screen_scale", "screen"), &_OS::get_screen_scale, DEFVAL(-1));
 	ClassDB::bind_method(D_METHOD("get_screen_max_scale"), &_OS::get_screen_max_scale);
+	ClassDB::bind_method(D_METHOD("get_screen_refresh_rate", "screen"), &_OS::get_screen_refresh_rate, DEFVAL(-1));
 	ClassDB::bind_method(D_METHOD("get_window_position"), &_OS::get_window_position);
 	ClassDB::bind_method(D_METHOD("set_window_position", "position"), &_OS::set_window_position);
 	ClassDB::bind_method(D_METHOD("get_window_size"), &_OS::get_window_size);

core/bind/core_bind.h

@@ -191,6 +191,7 @@ public:
 	virtual int get_screen_dpi(int p_screen = -1) const;
 	virtual float get_screen_scale(int p_screen = -1) const;
 	virtual float get_screen_max_scale() const;
+	virtual float get_screen_refresh_rate(int p_screen = -1) const;
 	virtual Point2 get_window_position() const;
 	virtual void set_window_position(const Point2 &p_position);
 	virtual Size2 get_max_window_size() const;

core/os/os.h

@@ -209,6 +209,9 @@ public:
 	virtual void open_midi_inputs();
 	virtual void close_midi_inputs();
 
+	// Returned by get_screen_refresh_rate if the method fails.
+	const float SCREEN_REFRESH_RATE_FALLBACK = -1.0;
+
 	virtual int get_screen_count() const { return 1; }
 	virtual int get_current_screen() const { return 0; }
 	virtual void set_current_screen(int p_screen) {}
@@ -217,6 +220,7 @@ public:
 	virtual int get_screen_dpi(int p_screen = -1) const { return 72; }
 	virtual float get_screen_scale(int p_screen = -1) const { return 1.0; }
 	virtual float get_screen_max_scale() const { return 1.0; };
+	virtual float get_screen_refresh_rate(int p_screen = -1) const { return SCREEN_REFRESH_RATE_FALLBACK; };
 	virtual Point2 get_window_position() const { return Vector2(); }
 	virtual void set_window_position(const Point2 &p_position) {}
 	virtual Size2 get_max_window_size() const { return Size2(); };

doc/classes/OS.xml

@@ -408,6 +408,20 @@
 				Returns the position of the specified screen by index. If [code]screen[/code] is [code]-1[/code] (the default value), the current screen will be used.
 			</description>
 		</method>
+		<method name="get_screen_refresh_rate" qualifiers="const">
+			<return type="float" />
+			<argument index="0" name="screen" type="int" default="-1" />
+			<description>
+				Returns the current refresh rate of the specified screen. If [code]screen[/code] is [code]-1[/code] (the default value), the current screen will be used.
+				[b]Note:[/b] Returns [code]-1.0[/code] if Godot fails to find the refresh rate for the specified screen. On HTML5, [method get_screen_refresh_rate] will always return [code]-1.0[/code] as there is no way to retrieve the refresh rate on that platform.
+				To fallback to a default refresh rate if the method fails, try:
+				[codeblock]
+				var refresh_rate = OS.get_screen_refresh_rate()
+				if refresh_rate &lt; 0:
+				    refresh_rate = 60.0
+				[/codeblock]
+			</description>
+		</method>
 		<method name="get_screen_scale" qualifiers="const">
 			<return type="float" />
 			<argument index="0" name="screen" type="int" default="-1" />

platform/android/java/lib/src/org/godotengine/godot/GodotIO.java

@@ -226,6 +226,14 @@ public class GodotIO {
 		return (int)(metrics.density * 160f);
 	}
 
+	public double getScreenRefreshRate(double fallback) {
+		Display display = activity.getWindowManager().getDefaultDisplay();
+		if (display != null) {
+			return display.getRefreshRate();
+		}
+		return fallback;
+	}
+
 	public int[] getWindowSafeArea() {
 		DisplayMetrics metrics = activity.getResources().getDisplayMetrics();
 		Display display = activity.getWindowManager().getDefaultDisplay();

platform/android/java_godot_io_wrapper.cpp

@@ -53,6 +53,7 @@ GodotIOJavaWrapper::GodotIOJavaWrapper(JNIEnv *p_env, jobject p_godot_io_instanc
 		_get_locale = p_env->GetMethodID(cls, "getLocale", "()Ljava/lang/String;");
 		_get_model = p_env->GetMethodID(cls, "getModel", "()Ljava/lang/String;");
 		_get_screen_DPI = p_env->GetMethodID(cls, "getScreenDPI", "()I");
+		_get_screen_refresh_rate = p_env->GetMethodID(cls, "getScreenRefreshRate", "(D)D");
 		_get_window_safe_area = p_env->GetMethodID(cls, "getWindowSafeArea", "()[I"),
 		_get_unique_id = p_env->GetMethodID(cls, "getUniqueID", "()Ljava/lang/String;");
 		_show_keyboard = p_env->GetMethodID(cls, "showKeyboard", "(Ljava/lang/String;ZIII)V");
@@ -136,6 +137,19 @@ int GodotIOJavaWrapper::get_screen_dpi() {
 	}
 }
 
+float GodotIOJavaWrapper::get_screen_refresh_rate(float p_fallback) {
+	if (_get_screen_refresh_rate) {
+		JNIEnv *env = get_jni_env();
+		if (env == nullptr) {
+			ERR_PRINT("An error occurred while trying to get screen refresh rate.");
+			return p_fallback;
+		}
+		return (float)env->CallDoubleMethod(godot_io_instance, _get_screen_refresh_rate, (double)p_fallback);
+	}
+	ERR_PRINT("An error occurred while trying to get the screen refresh rate.");
+	return p_fallback;
+}
+
 void GodotIOJavaWrapper::get_window_safe_area(int (&p_rect_xywh)[4]) {
 	if (_get_window_safe_area) {
 		JNIEnv *env = get_jni_env();

platform/android/java_godot_io_wrapper.h

@@ -51,6 +51,7 @@ private:
 	jmethodID _get_locale = 0;
 	jmethodID _get_model = 0;
 	jmethodID _get_screen_DPI = 0;
+	jmethodID _get_screen_refresh_rate = 0;
 	jmethodID _get_window_safe_area = 0;
 	jmethodID _get_unique_id = 0;
 	jmethodID _show_keyboard = 0;
@@ -72,6 +73,7 @@ public:
 	String get_model();
 	int get_screen_dpi();
 	void get_window_safe_area(int (&p_rect_xywh)[4]);
+	float get_screen_refresh_rate(float p_fallback);
 	String get_unique_id();
 	bool has_vk();
 	void show_vk(const String &p_existing, bool p_multiline, int p_max_input_length, int p_cursor_start, int p_cursor_end);

platform/android/os_android.cpp

@@ -444,6 +444,10 @@ int OS_Android::get_screen_dpi(int p_screen) const {
 	return godot_io_java->get_screen_dpi();
 }
 
+float OS_Android::get_screen_refresh_rate(int p_screen) const {
+	return godot_io_java->get_screen_refresh_rate(OS::get_singleton()->SCREEN_REFRESH_RATE_FALLBACK);
+}
+
 String OS_Android::get_data_path() const {
 	return get_user_data_dir();
 }

platform/android/os_android.h

@@ -154,6 +154,7 @@ public:
 	virtual bool has_clipboard() const;
 	virtual String get_model_name() const;
 	virtual int get_screen_dpi(int p_screen = 0) const;
+	virtual float get_screen_refresh_rate(int p_screen = 0) const;
 
 	virtual bool get_window_per_pixel_transparency_enabled() const { return transparency_enabled; }
 	virtual void set_window_per_pixel_transparency_enabled(bool p_enabled) { ERR_FAIL_MSG("Setting per-pixel transparency is not supported at runtime, please set it in project settings instead."); }

platform/iphone/os_iphone.h

@@ -130,6 +130,7 @@ public:
 	virtual bool _check_internal_feature_support(const String &p_feature);
 
 	virtual int get_screen_dpi(int p_screen = -1) const;
+	virtual float get_screen_refresh_rate(int p_screen = -1) const;
 
 	void pencil_press(int p_idx, int p_x, int p_y, bool p_pressed, bool p_doubleclick);
 	void touch_press(int p_idx, int p_x, int p_y, bool p_pressed, bool p_doubleclick);

platform/iphone/os_iphone.mm

@@ -565,6 +565,10 @@ int OSIPhone::get_screen_dpi(int p_screen) const {
 	}
 }
 
+float OSIPhone::get_screen_refresh_rate(int p_screen) const {
+	return [UIScreen mainScreen].maximumFramesPerSecond;
+}
+
 Rect2 OSIPhone::get_window_safe_area() const {
 	if (@available(iOS 11, *)) {
 		UIEdgeInsets insets = UIEdgeInsetsZero;

platform/osx/os_osx.h

@@ -276,6 +276,7 @@ public:
 	virtual int get_screen_dpi(int p_screen = -1) const;
 	virtual float get_screen_scale(int p_screen = -1) const;
 	virtual float get_screen_max_scale() const;
+	virtual float get_screen_refresh_rate(int p_screen = -1) const;
 
 	virtual Point2 get_window_position() const;
 	virtual void set_window_position(const Point2 &p_position);

platform/osx/os_osx.mm

@@ -2564,6 +2564,22 @@ int OS_OSX::get_screen_dpi(int p_screen) const {
 	return 72;
 }
 
+float OS_OSX::get_screen_refresh_rate(int p_screen) const {
+	if (p_screen < 0) {
+		p_screen = get_current_screen();
+	}
+
+	NSArray *screenArray = [NSScreen screens];
+	if ((NSUInteger)p_screen < [screenArray count]) {
+		NSDictionary *description = [[screenArray objectAtIndex:p_screen] deviceDescription];
+		const CGDisplayModeRef displayMode = CGDisplayCopyDisplayMode([[description objectForKey:@"NSScreenNumber"] unsignedIntValue]);
+		const double displayRefreshRate = CGDisplayModeGetRefreshRate(displayMode);
+		return (float)displayRefreshRate;
+	}
+	ERR_PRINT("An error occurred while trying to get the screen refresh rate.");
+	return OS::get_singleton()->SCREEN_REFRESH_RATE_FALLBACK;
+}
+
 Size2 OS_OSX::get_screen_size(int p_screen) const {
 	if (p_screen < 0) {
 		p_screen = get_current_screen();

platform/windows/os_windows.cpp

@@ -1954,6 +1954,12 @@ typedef struct {
 	int dpi;
 } EnumDpiData;
 
+typedef struct {
+	int count;
+	int screen;
+	float rate;
+} EnumRefreshRateData;
+
 static BOOL CALLBACK _MonitorEnumProcDpi(HMONITOR hMonitor, HDC hdcMonitor, LPRECT lprcMonitor, LPARAM dwData) {
 	EnumDpiData *data = (EnumDpiData *)dwData;
 	if (data->count == data->screen) {
@@ -1964,12 +1970,46 @@ static BOOL CALLBACK _MonitorEnumProcDpi(HMONITOR hMonitor, HDC hdcMonitor, LPRE
 	return TRUE;
 }
 
+static BOOL CALLBACK _MonitorEnumProcRefreshRate(HMONITOR hMonitor, HDC hdcMonitor, LPRECT lprcMonitor, LPARAM dwData) {
+	EnumRefreshRateData *data = (EnumRefreshRateData *)dwData;
+	if (data->count == data->screen) {
+		MONITORINFOEXW minfo;
+		memset(&minfo, 0, sizeof(minfo));
+		minfo.cbSize = sizeof(minfo);
+		GetMonitorInfoW(hMonitor, &minfo);
+
+		DEVMODEW dm;
+		memset(&dm, 0, sizeof(dm));
+		dm.dmSize = sizeof(dm);
+		EnumDisplaySettingsW(minfo.szDevice, ENUM_CURRENT_SETTINGS, &dm);
+
+		data->rate = dm.dmDisplayFrequency;
+	}
+
+	data->count++;
+	return TRUE;
+}
+
 int OS_Windows::get_screen_dpi(int p_screen) const {
-	EnumDpiData data = { 0, p_screen == -1 ? get_current_screen() : p_screen, 72 };
+	EnumDpiData data = {
+		0,
+		p_screen == -1 ? get_current_screen() : p_screen,
+		72,
+	};
 	EnumDisplayMonitors(NULL, NULL, _MonitorEnumProcDpi, (LPARAM)&data);
 	return data.dpi;
 }
 
+float OS_Windows::get_screen_refresh_rate(int p_screen) const {
+	EnumRefreshRateData data = {
+		0,
+		p_screen == -1 ? get_current_screen() : p_screen,
+		OS::get_singleton()->SCREEN_REFRESH_RATE_FALLBACK,
+	};
+	EnumDisplayMonitors(nullptr, nullptr, _MonitorEnumProcRefreshRate, (LPARAM)&data);
+	return data.rate;
+}
+
 Point2 OS_Windows::get_window_position() const {
 	if (minimized) {
 		return last_pos;

platform/windows/os_windows.h

@@ -445,6 +445,7 @@ public:
 	virtual Point2 get_screen_position(int p_screen = -1) const;
 	virtual Size2 get_screen_size(int p_screen = -1) const;
 	virtual int get_screen_dpi(int p_screen = -1) const;
+	virtual float get_screen_refresh_rate(int p_screen = -1) const;
 
 	virtual Point2 get_window_position() const;
 	virtual void set_window_position(const Point2 &p_position);

platform/x11/os_x11.cpp

@@ -1323,6 +1323,65 @@ int OS_X11::get_screen_dpi(int p_screen) const {
 	return 96;
 }
 
+float OS_X11::get_screen_refresh_rate(int p_screen) const {
+	if (p_screen == -1) {
+		p_screen = get_current_screen();
+	}
+
+	//invalid screen?
+	ERR_FAIL_INDEX_V(p_screen, get_screen_count(), OS::get_singleton()->SCREEN_REFRESH_RATE_FALLBACK);
+
+	//Use xrandr to get screen refresh rate.
+	if (xrandr_ext_ok) {
+		XRRScreenResources *screen_info = XRRGetScreenResources(x11_display, x11_window);
+		if (screen_info) {
+			RRMode current_mode = 0;
+			xrr_monitor_info *monitors = nullptr;
+
+			if (xrr_get_monitors) {
+				int count = 0;
+				monitors = xrr_get_monitors(x11_display, x11_window, true, &count);
+				ERR_FAIL_INDEX_V(p_screen, count, OS::get_singleton()->SCREEN_REFRESH_RATE_FALLBACK);
+			} else {
+				ERR_PRINT("An error occurred while trying to get the screen refresh rate.");
+				return OS::get_singleton()->SCREEN_REFRESH_RATE_FALLBACK;
+			}
+
+			bool found_active_mode = false;
+			for (int crtc = 0; crtc < screen_info->ncrtc; crtc++) { // Loop through outputs to find which one is currently outputting.
+				XRRCrtcInfo *monitor_info = XRRGetCrtcInfo(x11_display, screen_info, screen_info->crtcs[crtc]);
+				if (monitor_info->x != monitors[p_screen].x || monitor_info->y != monitors[p_screen].y) { // If X and Y aren't the same as the monitor we're looking for, this isn't the right monitor. Continue.
+					continue;
+				}
+
+				if (monitor_info->mode != None) {
+					current_mode = monitor_info->mode;
+					found_active_mode = true;
+					break;
+				}
+			}
+
+			if (found_active_mode) {
+				for (int mode = 0; mode < screen_info->nmode; mode++) {
+					XRRModeInfo m_info = screen_info->modes[mode];
+					if (m_info.id == current_mode) {
+						// Snap to nearest 0.01 to stay consistent with other platforms.
+						return Math::stepify((float)m_info.dotClock / ((float)m_info.hTotal * (float)m_info.vTotal), 0.01);
+					}
+				}
+			}
+
+			ERR_PRINT("An error occurred while trying to get the screen refresh rate."); // We should have returned the refresh rate by now. An error must have occurred.
+			return OS::get_singleton()->SCREEN_REFRESH_RATE_FALLBACK;
+		} else {
+			ERR_PRINT("An error occurred while trying to get the screen refresh rate.");
+			return OS::get_singleton()->SCREEN_REFRESH_RATE_FALLBACK;
+		}
+	}
+	ERR_PRINT("An error occurred while trying to get the screen refresh rate.");
+	return OS::get_singleton()->SCREEN_REFRESH_RATE_FALLBACK;
+}
+
 Point2 OS_X11::get_window_position() const {
 	int x, y;
 	Window child;

platform/x11/os_x11.h

@@ -296,6 +296,7 @@ public:
 	virtual Point2 get_screen_position(int p_screen = -1) const;
 	virtual Size2 get_screen_size(int p_screen = -1) const;
 	virtual int get_screen_dpi(int p_screen = -1) const;
+	virtual float get_screen_refresh_rate(int p_screen = -1) const;
 	virtual Point2 get_window_position() const;
 	virtual void set_window_position(const Point2 &p_position);
 	virtual Size2 get_window_size() const;