Prompting a user with an input box? [C++]

Question

My goal is to simply use a pop-up box to ask the user for an input. I\'ve searched around quite a bit and pretty much all the results say that creating a messageBox is reall

Answer 1

My answer is based on Stephen Quan's answer to How to load & call a VBScript function from within C++? Added full UTF-8 support, as you can gather from the code comments in the CPP file. Unlike using Microsoft Script Control to create the InputBox, this can be used in x86 and x64 executables, libraries, and controls.

"inputbox.h":

extern "C" char *InputBox(char *Prompt, char *Title = (char *)"", char *Default = (char *)"");
extern "C" char *PasswordBox(char *Prompt, char *Title = (char *)"", char *Default = (char *)"");

"inputbox.cpp":

#include "inputbox.h"

// Windows API
#include 

// VBScript InputBox
#include 
#include 
#include 

// UTF-8 Support
#include 
#include 
#include 

using std::string;
using std::vector;

typedef std::basic_string tstring;

static tstring StringWiden(string Str)
{
    const size_t wchar_tCount = Str.size() + 1;

    vector Buffer(wchar_tCount);

    return tstring{ Buffer.data(), (size_t)MultiByteToWideChar(CP_UTF8, 0, Str.c_str(), -1, Buffer.data(), wchar_tCount) };
}

static string StringShorten(tstring Str)
{
    int nBytes = (size_t)WideCharToMultiByte(CP_UTF8, 0, Str.c_str(), (int)Str.length(), NULL, 0, NULL, NULL);

    vector Buffer((size_t)nBytes);

    return string{ Buffer.data(), (size_t)WideCharToMultiByte(CP_UTF8, 0, Str.c_str(), (int)Str.length(), Buffer.data(), nBytes, NULL, NULL) };
}

static string StringReplaceAll(string Str, string SubStr, string NewStr)
{
    size_t Position = 0;
    const size_t SubLen = SubStr.length(), NewLen = NewStr.length();

    while ((Position = Str.find(SubStr, Position)) != string::npos)
    {
        Str.replace(Position, SubLen, NewStr);
        Position += NewLen;
    }

    return Str;
}

static string CPPNewLineToVBSNewLine(string NewLine)
{
    size_t Position = 0;

    while (Position < NewLine.length())
    {
        if (NewLine[Position] == '\n' || NewLine[Position] == '\r')
            NewLine.replace(Position, 2, "\" + vbNewLine + \"");

        Position += 1;
    }

    return NewLine;
}

class CSimpleScriptSite :
    public IActiveScriptSite,
    public IActiveScriptSiteWindow
{
public:
    CSimpleScriptSite() : m_cRefCount(1), m_hWnd(NULL) { }

    // IUnknown

    STDMETHOD_(ULONG, AddRef)();
    STDMETHOD_(ULONG, Release)();
    STDMETHOD(QueryInterface)(REFIID riid, void **ppvObject);

    // IActiveScriptSite

    STDMETHOD(GetLCID)(LCID *plcid) { *plcid = 0; return S_OK; }
    STDMETHOD(GetItemInfo)(LPCOLESTR pstrName, DWORD dwReturnMask, IUnknown **ppiunkItem, ITypeInfo **ppti) { return TYPE_E_ELEMENTNOTFOUND; }
    STDMETHOD(GetDocVersionString)(BSTR *pbstrVersion) { *pbstrVersion = SysAllocString(L"1.0"); return S_OK; }
    STDMETHOD(OnScriptTerminate)(const VARIANT *pvarResult, const EXCEPINFO *pexcepinfo) { return S_OK; }
    STDMETHOD(OnStateChange)(SCRIPTSTATE ssScriptState) { return S_OK; }
    STDMETHOD(OnScriptError)(IActiveScriptError *pIActiveScriptError) { return S_OK; }
    STDMETHOD(OnEnterScript)(void) { return S_OK; }
    STDMETHOD(OnLeaveScript)(void) { return S_OK; }

    // IActiveScriptSiteWindow

    STDMETHOD(GetWindow)(HWND *phWnd) { *phWnd = m_hWnd; return S_OK; }
    STDMETHOD(EnableModeless)(BOOL fEnable) { return S_OK; }

    // Miscellaneous

    STDMETHOD(SetWindow)(HWND hWnd) { m_hWnd = hWnd; return S_OK; }

public:
    LONG m_cRefCount;
    HWND m_hWnd;
};

STDMETHODIMP_(ULONG) CSimpleScriptSite::AddRef()
{
    return InterlockedIncrement(&m_cRefCount);
}

STDMETHODIMP_(ULONG) CSimpleScriptSite::Release()
{
    if (!InterlockedDecrement(&m_cRefCount))
    {
        delete this;
        return 0;
    }
    return m_cRefCount;
}

STDMETHODIMP CSimpleScriptSite::QueryInterface(REFIID riid, void **ppvObject)
{
    if (riid == IID_IUnknown || riid == IID_IActiveScriptSiteWindow)
    {
        *ppvObject = (IActiveScriptSiteWindow *)this;
        AddRef();
        return NOERROR;
    }
    if (riid == IID_IActiveScriptSite)
    {
        *ppvObject = (IActiveScriptSite *)this;
        AddRef();
        return NOERROR;
    }
    return E_NOINTERFACE;
}

static HHOOK hHook = 0;
static bool HideInput = false;

static LRESULT CALLBACK InputBoxProc(int nCode, WPARAM wParam, LPARAM lParam)
{
    if (nCode < HC_ACTION)
        return CallNextHookEx(hHook, nCode, wParam, lParam);

    if (nCode = HCBT_ACTIVATE)
    {
        if (HideInput == true)
        {
            HWND TextBox = FindWindowExA((HWND)wParam, NULL, "Edit", NULL);
            SendDlgItemMessage((HWND)wParam, GetDlgCtrlID(TextBox), EM_SETPASSWORDCHAR, '*', 0);
        }
    }

    if (nCode = HCBT_CREATEWND)
    {
        if (!(GetWindowLongPtr((HWND)wParam, GWL_STYLE) & WS_CHILD))
            SetWindowLongPtr((HWND)wParam, GWL_EXSTYLE, GetWindowLongPtr((HWND)wParam, GWL_EXSTYLE) | WS_EX_DLGMODALFRAME);
    }

    return CallNextHookEx(hHook, nCode, wParam, lParam);
}

static char *InputBoxHelper(char *Prompt, char *Title, char *Default)
{
    HRESULT hr = S_OK;
    hr = CoInitialize(NULL);

    // Initialize
    CSimpleScriptSite *pScriptSite = new CSimpleScriptSite();
    CComPtr spVBScript;
    CComPtr spVBScriptParse;
    hr = spVBScript.CoCreateInstance(OLESTR("VBScript"));
    hr = spVBScript->SetScriptSite(pScriptSite);
    hr = spVBScript->QueryInterface(&spVBScriptParse);
    hr = spVBScriptParse->InitNew();

    // Replace quotes with double quotes
    string strPrompt = StringReplaceAll(Prompt, "\"", "\"\"");
    string strTitle = StringReplaceAll(Title, "\"", "\"\"");
    string strDefault = StringReplaceAll(Default, "\"", "\"\"");

    // Create evaluation string
    string Evaluation = "InputBox(\"" + strPrompt + "\", \"" + strTitle + "\", \"" + strDefault + "\")";
    Evaluation = CPPNewLineToVBSNewLine(Evaluation);
    tstring WideEval = StringWiden(Evaluation);

    // Run InpuBox
    CComVariant result;
    EXCEPINFO ei = {};

    DWORD ThreadID = GetCurrentThreadId();
    HINSTANCE ModHwnd = GetModuleHandle(NULL);
    hr = pScriptSite->SetWindow(GetAncestor(GetActiveWindow(), GA_ROOTOWNER));
    hHook = SetWindowsHookEx(WH_CBT, &InputBoxProc, ModHwnd, ThreadID);
    hr = spVBScriptParse->ParseScriptText(WideEval.c_str(), NULL, NULL, NULL, 0, 0, SCRIPTTEXT_ISEXPRESSION, &result, &ei);
    UnhookWindowsHookEx(hHook);


    // Cleanup
    spVBScriptParse = NULL;
    spVBScript = NULL;
    pScriptSite->Release();
    pScriptSite = NULL;

    CoUninitialize();
    static string strResult;
    _bstr_t bstrResult = (_bstr_t)result;
    strResult = StringShorten((wchar_t *)bstrResult);
    return (char *)strResult.c_str();
}

char *InputBox(char *Prompt, char *Title, char *Default)
{
    HideInput = false;

    return InputBoxHelper(Prompt, Title, Default);
}

char *PasswordBox(char *Prompt, char *Title, char *Default)
{
    HideInput = true;

    return InputBoxHelper(Prompt, Title, Default);
}

Create the two above files and then add them to your Visual Studio project.

In any file you want the input or password box functions, (found in the header), simply include the header:

#include "inputbox.h"

// use functions here

I also got rid of the default Windows application icon in the title bar of the VBScript InputBox, because a lot of people I've seen complain about how ugly it is to see that there.

Let me know if you have any questions.