internal/glfwwin: create a pseudo monitor for Xbox

Updates #1162

internal/glfwwin/microsoftgdk_windows.go

@@ -44,3 +44,18 @@ func isXbox() bool {
 	t := C.XSystemGetDeviceType()
 	return t != _XSystemDeviceType_Unknown && t != _XSystemDeviceType_Pc
 }
+
+func monitorResolution() (int, int) {
+	switch C.XSystemGetDeviceType() {
+	case _XSystemDeviceType_XboxOne, _XSystemDeviceType_XboxOneS:
+		return 1920, 1080
+	case _XSystemDeviceType_XboxScarlettLockhart:
+		// Series S
+		return 2560, 1440
+	case _XSystemDeviceType_XboxOneX, _XSystemDeviceType_XboxOneXDevkit, _XSystemDeviceType_XboxScarlettAnaconda, _XSystemDeviceType_XboxScarlettDevkit:
+		// Series X
+		return 3840, 2160
+	default:
+		return 1920, 1080
+	}
+}

internal/glfwwin/notmicrosoftgdk_windows.go

@@ -20,3 +20,7 @@ package glfwwin
 func isXbox() bool {
 	return false
 }
+
+func monitorResolution() (int, int) {
+	panic("glfwwin: monitorResolution is not implemented in this environment")
+}

internal/glfwwin/win32init_windows.go

@@ -259,9 +259,25 @@ func platformInit() error {
 		return err
 	}
 	if isXbox() {
-		// TODO: Create a dummy window.
+		// On Xbox, APIs to get monitors are not available.
-		// The resolution can be deterined based on a device.
+		// Create a pseudo monitor instance instead.
-		// See https://github.com/microsoft/Xbox-GDK-Samples/blob/1f44bdabed6e340170e2c7d1007500e4dff897bb/Samples/IntroGraphics/SimpleDynamicResources/Main.cpp#L118-L148
+		w, h := monitorResolution()
+		mode := &VidMode{
+			Width:       w,
+			Height:      h,
+			RedBits:     8,
+			GreenBits:   8,
+			BlueBits:    8,
+			RefreshRate: 0, // TODO: Is it possible to get an appropriate refresh rate?
+		}
+		m := &Monitor{
+			name:        "Xbox Monitor",
+			modes:       []*VidMode{mode},
+			currentMode: mode,
+		}
+		if err := inputMonitor(m, Connected, _GLFW_INSERT_LAST); err != nil {
+			return err
+		}
 	} else {
 		if err := pollMonitorsWin32(); err != nil {
 			return err