main.go

package main

import (
	"fmt"
	"syscall"
	"unsafe"
)

var (
	user32, _                          = syscall.LoadLibrary("User32.dll")
	dxva2, _                           = syscall.LoadLibrary("dxva2.dll")
	procEnumDisplayMonitors, _         = syscall.GetProcAddress(user32, "EnumDisplayMonitors")
	getPhysicalMonitorsFromHMONITOR, _ = syscall.GetProcAddress(dxva2, "GetPhysicalMonitorsFromHMONITOR")
)

type RECT struct {
	Left   int32
	Top    int32
	Right  int32
	Bottom int32
}

type DisplayMonitorInfo struct {
	Handle        syscall.Handle
	DeviceContext syscall.Handle
	Rectangle     RECT
}

type MONITORENUMPROC func(hmonitor syscall.Handle, hdc syscall.Handle, rect *RECT, lparam uintptr) int32

func EnumDisplayMonitors(hdc syscall.Handle, clip *RECT, fnEnum MONITORENUMPROC, data uintptr) bool {
	fnEnumRaw := func(hmonitor uintptr, hdc uintptr, rect uintptr, lparam uintptr) uintptr {
		return uintptr(fnEnum(
			syscall.Handle(hmonitor),
			syscall.Handle(hdc),
			(*RECT)(unsafe.Pointer(rect)),
			lparam))
	}

	r1, _, _ := syscall.Syscall6(
		procEnumDisplayMonitors,
		4,
		uintptr(hdc),
		uintptr(unsafe.Pointer(clip)),
		syscall.NewCallback(fnEnumRaw),
		uintptr(data),
		0,
		0)
	return r1 != 0
}

func GetAllDisplayMonitors() []DisplayMonitorInfo {
	var result []DisplayMonitorInfo
	EnumDisplayMonitors(
		syscall.Handle(0),
		nil,
		func(hmonitor syscall.Handle, hdc syscall.Handle, rect *RECT, lparam uintptr) int32 {
			result = append(result, DisplayMonitorInfo{Handle: hmonitor, DeviceContext: hdc, Rectangle: *rect})
			return 1
		},
		uintptr(0),
	)
	return result
}

type PhysicalMonitor struct {
	hPhysicalMonitor             syscall.Handle
	szPhysicalMonitorDescription string
}

func GetPhysicalMonitorsFromHMONITOR(handle syscall.Handle, monitorArraySize uint, array *[]PhysicalMonitor) (result uintptr) {
	ret, _, callErr := syscall.Syscall(
		getPhysicalMonitorsFromHMONITOR,
		3,
		uintptr(handle),
		uintptr(monitorArraySize), uintptr(unsafe.Pointer(array)))

	if callErr != 0 {
		fmt.Println(callErr)
		syscall.ExitProcess(13)
	}

	result = ret
	return
}

func main() {
	defer syscall.FreeLibrary(user32)
	defer syscall.FreeLibrary(dxva2)

	monitors := GetAllDisplayMonitors()

	for _, monitor := range monitors {
		fmt.Println(monitor)
		array := make([]PhysicalMonitor, 1)
		GetPhysicalMonitorsFromHMONITOR(monitor.Handle, 1, &array)
		fmt.Println(len(array))
	}

}