Windows API dialogs without using resource files

Question

I'm trying to create a dialog box using C++ and the windows API, but I don't want the dialog defined in a resource file. I can't find anything good on this on the web, and none of the examples I've read seem to define the dialog programmatically.

How can I do this?

A simple example is fine. I'm not doing anything complicated with it yet.

Answer 1

Raymond Chen wrote a few posts about the dialog manager:

• The dialog manager, part 1: Warm-ups
• The dialog manager, part 2: Creating the frame window
• The dialog manager, part 3: Creating the controls
• The dialog manager, part 4: The dialog loop
• The dialog manager, part 5: Converting a non-modal dialog box to modal
• The dialog manager, part 6: Subtleties in message loops
• The dialog manager, part 7: More subtleties in message loops
• The dialog manager, part 8: Custom navigation in dialog boxes
• The dialog manager, part 9: Custom accelerators in dialog boxes

Answer 2

If all you want to do is show a window with controls, it's possible to create a window without using resource (.rc) files / scripts.

This isn't the same as a dialog, but it might be easier than creating a dialog programmatically.

First, a few notes about how this is done:

• Instead of designing the dialog in the rc file, you could manually use CreateWindow (or CreateWindowEx) to create child windows of a main window. (for .NET Windows Forms programmers, these windows are like Controls).

• This process will not be graphical at all (you will need to manually type in the location and size of each window), but I think this can be a great way to understand how dialogs are created under the hood.

• There are some disadvantages to not using a real dialog, namely that tab will not work when switching between controls.

---

About the example:

• This example features a dialog box with two buttons, an edit box (.NET Windows Forms programmers would think of it as a TextBox), and a check box.

It has been tested under the following conditions:

• x86 build
• x64 build
• Unicode build (UNICODE and _UNICODE defined)
• Non-Unicode build (UNICODE and _UNICODE not defined)
• Built with Visual Studio's C compiler
• Built with Visual Studio's C++ compiler
• OS: Windows 10 64 bit

Note: UNICODE

• As of the time of writing, UTF-8 is still in beta for Windows 10
  • If you have not enabled this setting, you should assume that any char* is ACP, not UTF-8, this applies to standard library functions too
  • Even though in Linux, that same standard library function would be UTF-8.
  • Sadly, some C++ standard library features only work with char* (e.g., exception messages).
  • You can still use UTF-8 in Windows without the option set, you will just have to encode it back to UTF-16 before calling winapi functions.
  • Here is a reddit thread with a reply from somebody who claims to have worked on UTF-8 on Windows, it has some good information.
• UNICODE in Windows means "UTF-16", not "UTF-8".
• Using Unicode of some kind is strongly recommended for any version of Windows that is not very old.
  • Be aware that if you don't use Unicode, your program may be utterly unable to open file names containing Unicode characters, handle directories (e.g., usernames) with non-ACP characters, etc.
  • Using ACP functions (SendMessageA,etc) without somehow verifying that UTF-8 is enabled (it's disabled by default) is probably a bug.
  • For max portability/flexibility, I would recommend using UTF-16 and the W version of all API functions, translating from UTF-8 to UTF-16 at the last minute. Read this page very carefully.

---

Now for the code:

Note that a large amount of comments have been added to try to document the windows functions, I recommend copy/pasting this into a text editor, for best results.

// This sample will work either with or without UNICODE, it looks like
// it's recommended now to use UNICODE for all new code, but I left
// the ANSI option in there just to get the absolute maximum amount
// of compatibility.
//
// Note that UNICODE and _UNICODE go together, unfortunately part
// of the Windows API uses _UNICODE, and part of it uses UNICODE.
//
// tchar.h, for example, makes heavy use of _UNICODE, and windows.h
// makes heavy use of UNICODE.
#define UNICODE
#define _UNICODE
//#undef UNICODE
//#undef _UNICODE

#include <windows.h>
#include <tchar.h>

// I made this struct to more conveniently store the
// positions / size of each window in the dialog
typedef struct SizeAndPos_s
{
    int x, y, width, height;
} SizeAndPos_t;

// Typically these would be #defines, but there
// is no reason to not make them constants
const WORD ID_btnHELLO = 1;
const WORD ID_btnQUIT = 2;
const WORD ID_CheckBox = 3;
const WORD ID_txtEdit = 4;
const WORD ID_btnShow = 5;

//                                    x,      y,      width,  height
const SizeAndPos_t mainWindow   =   { 150,    150,    300,    300 };

const SizeAndPos_t btnHello     =   { 20,     50,     80,     25 };
const SizeAndPos_t btnQuit      =   { 120,    50,     80,     25 };
const SizeAndPos_t chkCheck     =   { 20,     90,     185,    35 };

const SizeAndPos_t txtEdit      =   { 20,     150,    150,    20 };
const SizeAndPos_t btnShow      =   { 180,    150,    80,     25 };

HWND txtEditHandle = NULL;

// hwnd:    All window processes are passed the handle of the window
//         that they belong to in hwnd.
// msg:     Current message (e.g., WM_*) from the OS.
// wParam:  First message parameter, note that these are more or less
//          integers, but they are really just "data chunks" that
//          you are expected to memcpy as raw data to float, etc.
// lParam:  Second message parameter, same deal as above.
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{

    switch (msg)
    {

    case WM_CREATE:
        // Create the buttons
        //------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

        // Note that the "parent window" is the dialog itself. Since we are
        // in the dialog's WndProc, the dialog's handle is passed into hwnd.
        //
        //CreateWindow( lpClassName,        lpWindowName,       dwStyle,                                x,          y,          nWidth,         nHeight,            hWndParent,     hMenu,              hInstance,      lpParam
        //CreateWindow( windowClassName,    initial text,       style (flags),                          xPos,       yPos,       width,          height,             parentHandle,   menuHandle,         instanceHandle, param);
        CreateWindow(   TEXT("Button"),     TEXT("Hello"),      WS_VISIBLE | WS_CHILD,                  btnHello.x, btnHello.y, btnHello.width, btnHello.height,    hwnd,           (HMENU)ID_btnHELLO, NULL,           NULL);

        CreateWindow(   TEXT("Button"),     TEXT("Quit"),       WS_VISIBLE | WS_CHILD,                  btnQuit.x,  btnQuit.y,  btnQuit.width,  btnQuit.height,     hwnd,           (HMENU)ID_btnQUIT,  NULL,           NULL);

        // Create a checkbox
        //------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
        CreateWindow(  TEXT("button"),      TEXT("CheckBox"),   WS_VISIBLE | WS_CHILD | BS_CHECKBOX,    chkCheck.x, chkCheck.y, chkCheck.width, chkCheck.height,    hwnd,           (HMENU)ID_CheckBox, NULL,           NULL);

        // Create an edit box (single line text editing), and a button to show the text
        //------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
        //Handle        = CreateWindow(windowClassName,    windowName,           style,                              xPos,       yPos,       width,          height,             parentHandle,   menuHandle,         instanceHandle, param);
        txtEditHandle   = CreateWindow(TEXT("Edit"),       TEXT("Initial Text"), WS_CHILD | WS_VISIBLE | WS_BORDER,  txtEdit.x,  txtEdit.y,  txtEdit.width,  txtEdit.height,     hwnd,           (HMENU)ID_txtEdit,  NULL,           NULL);

        //CreateWindow( windowClassName,    windowName,         style,                                  xPos,      yPos,      width,          height,           parentHandle,   menuHandle,         instanceHandle, param);
        CreateWindow(   TEXT("Button"),     TEXT("Show"),       WS_VISIBLE | WS_CHILD,                  btnShow.x, btnShow.y, btnShow.width, btnShow.height,    hwnd,           (HMENU)ID_btnShow,  NULL,           NULL);

        // Create an Updown control. Note that this control will allow you to type in non-number characters, but it will not affect the state of the control

        break;

    // For more information about WM_COMMAND, see
    // https://msdn.microsoft.com/en-us/library/windows/desktop/ms647591(v=vs.85).aspx
    case WM_COMMAND:

        // The LOWORD of wParam identifies which control sent
        // the WM_COMMAND message. The WM_COMMAND message is
        // sent when the button has been clicked.
        if (LOWORD(wParam) == ID_btnHELLO)
        {
            MessageBox(hwnd, TEXT("Hello!"), TEXT("Hello"), MB_OK);
        }
        else if (LOWORD(wParam) == ID_btnQUIT)
        {
            PostQuitMessage(0);
        }
        else if (LOWORD(wParam) == ID_CheckBox)
        {
            UINT checked = IsDlgButtonChecked(hwnd, ID_CheckBox);

            if (checked)
            {
                CheckDlgButton(hwnd, ID_CheckBox, BST_UNCHECKED);
                MessageBox(hwnd, TEXT("The checkbox has been unchecked."), TEXT("CheckBox Event"), MB_OK);
            }
            else
            {
                CheckDlgButton(hwnd, ID_CheckBox, BST_CHECKED);
                MessageBox(hwnd, TEXT("The checkbox has been checked."), TEXT("CheckBox Event"), MB_OK);
            }
        }
        else if (LOWORD(wParam) == ID_btnShow)
        {
               int textLength_WithNUL = GetWindowTextLength(txtEditHandle) + 1;
               // WARNING: If you are compiling this for C, please remember to remove the (TCHAR*) cast.
               TCHAR* textBoxText = (TCHAR*) malloc(sizeof(TCHAR) * textLength_WithNUL);

               GetWindowText(txtEditHandle, textBoxText, textLength_WithNUL);

               MessageBox(hwnd, textBoxText, TEXT("Here's what you typed"), MB_OK);

               free(textBoxText);
        }
        break;

    case WM_DESTROY:

        PostQuitMessage(0);
        break;
    }

    return DefWindowProc(hwnd, msg, wParam, lParam);
}


// hInstance: This handle refers to the running executable
// hPrevInstance: Not used. See https://blogs.msdn.microsoft.com/oldnewthing/20040615-00/?p=38873
// lpCmdLine: Command line arguments.
// nCmdShow: a flag that says whether the main application window
//           will be minimized, maximized, or shown normally.
//
// Note that it's necessary to use _tWinMain to make it
// so that command line arguments will work, both
// with and without UNICODE / _UNICODE defined.
int APIENTRY _tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow)
{
    MSG  msg;
    WNDCLASS mainWindowClass = { 0 };

    // You can set the main window name to anything, but
    // typically you should prefix custom window classes
    // with something that makes it unique.
    mainWindowClass.lpszClassName = TEXT("JRH.MainWindow");

    mainWindowClass.hInstance = hInstance;
    mainWindowClass.hbrBackground = GetSysColorBrush(COLOR_3DFACE);
    mainWindowClass.lpfnWndProc = WndProc;
    mainWindowClass.hCursor = LoadCursor(0, IDC_ARROW);

    RegisterClass(&mainWindowClass);

    // Notes:
    // - The classname identifies the TYPE of the window. Not a C type.
    //   This is a (TCHAR*) ID that Windows uses internally.
    // - The window name is really just the window text, this is
    //   commonly used for captions, including the title
    //   bar of the window itself.
    // - parentHandle is considered the "owner" of this
    //   window. MessageBoxes can use HWND_MESSAGE to
    //   free them of any window.
    // - menuHandle: hMenu specifies the child-window identifier,
    //               an integer value used by a dialog box
    //               control to notify its parent about events.
    //               The application determines the child-window
    //               identifier; it must be unique for all
    //               child windows with the same parent window.

    //CreateWindow( windowClassName,                windowName,             style,                            xPos,         yPos,       width,              height,            parentHandle,   menuHandle,  instanceHandle, param);
    CreateWindow(   mainWindowClass.lpszClassName,  TEXT("Main Window"),    WS_OVERLAPPEDWINDOW | WS_VISIBLE, mainWindow.x, mainWindow.y, mainWindow.width, mainWindow.height, NULL,           0,           hInstance,      NULL);

    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return (int)msg.wParam;
}

// This code is based roughly on tutorial code present at  http://zetcode.com/gui/winapi/

---

Further reading

The builtin set of window classes are rather limited, so you might be curious as to how you can define your own window classes ("Controls") using the Windows API, see the articles below:

• Custom Controls in Win32 API: The Basics (Code Project)
• The WINE emulator source serves as a good example of how the Windows API could be implemented, and how you can make your own window classes that imitate the behavior of builtin classes.
• Zetcode.com's tutorials

NOTE: I originally intended this post to cover the creation of dialogs programmatically. Due to a mistake on my part I didn't realize that you can't just "show" a window as a dialog. Unfortunately I wasn't able to get the setup mentioned by Raymond Chen working. Even looking at WINE's source, it's not super clear.

Answer 3

Here you can find how to use Windows API dialogs without using resource files.

The Windows API (only the C Win32 API, no MFC) tutorial:

Windows API tutorial

Answer 4

Take a look at this toolkit that describes how to create dialogs without resource files.

It's in WTL. However, I'm sure you can pick apart the internals to achieve the same thing using the Win32 API directly.

Answer 5

Try to search MSDN for "dialog templates in memory".

See this for example: Dialog Boxes