Universal 64 bit GUI entry

Just thought I would share what I think to be a universal entry point to 64 bit GUI applications. There are a few things that I'm beginning to focus on, some due to response on recent posts.

You'll probably notice that I've dropped using INVOKE. It's just a personal preference that I like there to be as much a one to one correlation between object and source as possible. There shouldn't be any need to put anything else in here as what the initialization process can't handle, messages like WM_ACTIVATE and the like can.

Code:

; ============================================================================================
; Universal entry point to 64 bit GUI applications.                              ; 005D =  93
; --------------------------------------------------------------------------------------------

  Begin:
        enter   sizeof.MSG, 0                   ; frame for MSG structure.
        mov     rbx, rsp                        ; Establish base pointer to MSG.
        or      [rbx + MSG.wParam], -1          ; Set default app return value.

    ; If InitApp fails, CF = 1 and procedure will have invoked some sort of error dialog.

        call    InitApp                         ; Startup app outside event driven processes.
        jc      .Done

        sub     rsp, 32                         ; Frame for pump API's

   @@:  xor      r9,  r9                        ; wMsgFilterMax
        mov      r8,  r9                        ; wMsgFilterMin
        mov     rdx,  r9                        ; hWnd
        mov     rcx, rbx                        ; lpMsg
        call    [GetMessage]
        or      eax, eax
        jz      .Done - 4                       ; App done, leave and kill pumps frame.

        inc     eax                             ; Bump to ZF = 1 if return was -1.
        jnz     @F

    ; Extended error handling in so much as error dialog is more informative and procedure
    ; displays GetLastError.

        push    MB_OK + MB_ICONSTOP             ; MessageBox response.
        push    .Done - 4                       ; Probably don't need to cleanup proc frame.
        jmp     ExtErr                          ; Show error and bail from app.

   @@:  mov     rcx, rbx                        ; lpMsg
        call    [TranslateMessage]
        mov     rcx, rbx                        ; lpMsg
        call    [DispatchMessage]
        jmp     @B

        add     rsp, 32                         ; Kill API frame.

  .Done:
        mov     rcx, [rbx + MSG.wParam]         ; Retrieve value returned by pump.
        leave                                   ; Kill procedure frame.
        jmp     [ExitProcess]                   ; Ends calling proc and all its threads.

Subsequent posts will detail what ExtErr does, but can be eliminated quite easily by taking those lines of code out, or maybe just commenting them out.