How to Call COM Methods from Go Using syscall.LazyProc?

Using COM in Go

Problem

You want to use a Windows DLL file in your Go program, but you're encountering an error when calling a COM method.

Solution

When calling COM methods from Go using a syscall.LazyProc, you need to use the Call function provided by the LazyProc object. The Call function expects all parameters to be passed as uintptrs.

For example, let's take the DllGetClassObject function from the Direct3D9 Go wrapper example mentioned in the referenced thread. Its signature is:

HRESULT __stdcall DllGetClassObject(
  _In_  REFCLSID rclsid,
  _In_  REFIID   riid,
  _Out_ LPVOID   *ppv
);

To call this function using Call, you would need to do something like this:

// TODO set these variables to the appropriate values
var rclsid, riid, ppv uintptr
ret, _, _ := getClassObject.Call(rclsid, riid, ppv)
// ret is the HRESULT value returned by DllGetClassObject, check it for errors

In the case of your XA_Session object, you need to wrap it in a Go type and then define wrapper methods for each COM method you want to use. Here's a simplified wrapper for the ConnectServer and DisconnectServer methods:

package xasession

import "syscall"

type XASession struct {
    // ...
}

func (obj *XASession) ConnectServer(id int) int {
    // ...
}

func (obj *XASession) DisconnectServer() {
    // ...
}

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