RegisterWindowMessage and SendMessage

New to Julia
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2

Hello, I’m not exactly sure what your code should achieve and what desired output is, but I can help your from Julia side.

The code you provided isn’t self contained so I modified it a bit:

const HANDLE = Ptr{Cvoid}
const LPSTR = Vector{UInt8}

function RegisterWindowMessage(message::String)
    msg = Vector{UInt8}(message)
    return ccall((:RegisterWindowMessageA, "user32"), stdcall, Cint, (Ptr{Vector{UInt8}},), Ref(msg) )
end

function SendWindowMessage(handle::HANDLE, msg::Cint)
    buffer = LPSTR(undef, 512)
    retval = ccall((:SendMessageA, "user32"), stdcall, Cint, (HANDLE, Cint, Cint, Ptr{UInt8}), handle, msg, sizeof(buffer), buffer)
    if retval == 0     
        return "NA"
    else
        buffer[end] = 0
        return String(unsafe_string(pointer(buffer),retval))
    end
end

function main()
    hwnd = Ptr{Int32}(Int64(0xffff))

    msg = RegisterWindowMessage("WM_GETCONTROLNAME")
    @show msg

    SendWindowMessage(HANDLE(hwnd), msg)
end

This is the output I get:

julia> main()
msg = 49822
"\0"

I can give you working example with SendMessageA, but I haven’t used RegisterWindowMessageA before, so I don’t know about that.