如何用WinAPI在FASM中绘制一条彩色线？

include 'win32a.inc'

section '.data' data readable writeable
    window_title db 'FASM WinAPI Line Example',0
    class_name db 'WinAPI_Line_Example_Class',0

section '.code' code readable executable
start:
    ; 注册窗口类
    invoke GetModuleHandle, 0
    mov    [wcex.hInstance], eax
    xor    eax, eax
    invoke LoadIcon, eax, IDI_APPLICATION
    mov    [wcex.hIcon], eax
    invoke LoadCursor, eax, IDC_ARROW
    mov    [wcex.hCursor], eax
    mov    [wcex.style], CS_HREDRAW or CS_VREDRAW
    mov    [wcex.lpfnWndProc], WindowProc
    mov    [wcex.cbClsExtra], 0
    mov    [wcex.cbWndExtra], 0
    mov    [wcex.hbrBackground], COLOR_WINDOW+1
    mov    [wcex.lpszMenuName], 0
    mov    [wcex.lpszClassName], class_name
    invoke RegisterClassEx, wcex

    ; 创建窗口
    invoke CreateWindowEx, WS_EX_CLIENTEDGE, class_name, window_title, WS_OVERLAPPEDWINDOW, \
            CW_USEDEFAULT, CW_USEDEFAULT, 640, 480, 0, 0, [wcex.hInstance], 0
    mov    [hwnd], eax

    ; 显示窗口
    invoke ShowWindow, [hwnd], SW_SHOWDEFAULT
    invoke UpdateWindow, [hwnd]

    ; 消息循环
    .message_loop:
        invoke GetMessage, msg, 0, 0, 0
        cmp    eax, 1
        jle    .exit_loop
        invoke TranslateMessage, msg
        invoke DispatchMessage, msg
        jmp    .message_loop

    .exit_loop:
        invoke ExitProcess, [msg.wParam]

WindowProc:
    push    ebx esi edi
    cmp     [msg.message], WM_CLOSE
    je      .wmclose

    invoke DefWindowProc, [hwnd], [msg.message], [msg.wParam], [msg.lParam]
    jmp     .finish

    .wmclose:
        invoke DestroyWindow, [hwnd]

    .finish:
        pop     edi esi ebx
    ret

section '.idata' import data readable writeable
    library kernel32, 'kernel32.dll', \
            user32, 'user32.dll'
    import kernel32, \
           GetModuleHandle, 'GetModuleHandleA', \
           ExitProcess, 'ExitProcess'
    import user32, \
           RegisterClassEx, 'RegisterClassExA', \
           CreateWindowEx, 'CreateWindowExA', \
           ShowWindow, 'ShowWindow', \
           UpdateWindow, 'UpdateWindow', \
           GetMessage, 'GetMessageA', \
           TranslateMessage, 'TranslateMessage', \
           DispatchMessage, 'DispatchMessageA', \
           DefWindowProc, 'DefWindowProcA', \
           DestroyWindow, 'DestroyWindow', \
           LoadIcon, 'LoadIconA', \
           LoadCursor, 'LoadCursorA'

section '.edata' export data readable
    export 'user32.dll', \
           MessageBox, 'MessageBoxA'

section '.reloc' fixups data discardable