Use A Parameter In A .rs Resource File C++ Console

Question

There is a similar question here but I'm looking for a C++ version.

I want to create a .rs file with a DialogBox that uses a string as a variable instead a " " so I can change it in the program.

For example: In

DEFPUSHBUTTON   "Hello World", IDOK, 8, 24, 75, 14

the "Hello World" would become a variable name, which I can 'define' or set in the program.

Why? I'm trying to make a DialogBox, like a 'template', and make many instances around the program with different Text in but same buttons in them.

Hope my gibberish is understanded.

Answer 1

Unfortunately, this is not possible. The caption text for a control must be a constant string because the resource file is actually compiled separately from your application and has no knowledge of variables defined elsewhere in your program's code.

Resource files do support string tables, but even these require the strings to be constant values. The advantage is that you can modify the resource file without access to the rest of the source code, which makes things like localization possible, even by outside translators.

So you're stuck hard-coding the initial caption of your DEFPUSHBUTTON. It can be an empty string or whatever value you want; you just need a placeholder. And you can put all of the possible captions in a string table (which I would recommend), but you cannot link the two using any automated mechanism.

You need to write the code to do this yourself. You could certainly dynamically generate resources, but that's quite a bit of trouble. I think the simplest way of doing this is just to create the dialog (using your "template" resource file), retrieve the handle of the controls whose caption text you want to change, and send them a WM_SETTEXT message with the new string. In fact, the SetDlgItemText function will do exactly this for you.

Perhaps that would be easier to explain with some code. Assume that you have a dialog resource defined, including all of your controls. All of the controls you wish to modify will need to have a unique ID assigned to each of them so that you can distinguish between them at runtime. It doesn't matter what the initial values you assign in the resource file are, as you're going to be changing them right off the bat. It might look like this:

IDD_TEMPLATE DIALOG DISCARDABLE  0, 0, xx, xx
STYLE DS_MODALFRAME | WS_POPUP | WS_CAPTION
CAPTION "Dialog Template"
FONT 8, "MS Sans Serif"
BEGIN
    CTEXT           "Placeholder text", IDC_MESSAGE, xx, xx, xx, xx
    DEFPUSHBUTTON   "Placeholder",      IDOK,        xx, xx, xx, xx
    PUSHBUTTON      "Cancel",           IDCANCEL,    xx, xx, xx, xx
END

Then, in your dialog procedure (DialogProc), handle the WM_INITDIALOG message as follows:

INT_PTR CALLBACK TemplateDialogProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
  switch (uMsg)
  {
    case WM_INITDIALOG:
    {
      // Load the caption strings you want to use from the string table
      // in the resource file, or get them from wherever you want.
      // These are the "variables" you wanted to use in the question.
      TCHAR* pszMessage;
      LoadString(hInstance,   /* instance handle for app or resource DLL */
                 IDS_MESSAGE, /* ID of the string resource to load       */
                 reinterpret_cast<LPTSTR>(&pszMessage),
                 0);
      TCHAR* pszOkBtn;
      LoadString(hInstance, IDS_OKBUTTON, reinterpret_cast<LPTSTR>(&pszOkBtn), 0);
      // ...etc.

      // Set the caption text for each control.
      SetDlgItemText(hwndDlg,     /* handle to the dialog box window */
                     IDC_MESSAGE, /* ID of the control to modify     */
                     pszMessage); /* variable containing text to set */
      SetDlgItemText(hwndDlg, IDOK, pszOkBtn);
      // ...etc.

      // And, if you want to set some other properties, you can do that too.
      // For example, you might set the caption of the dialog itself.
      TCHAR* pszTitle;
      LoadString(hInstance, IDS_DLGCAPTION, reinterpret_cast<LPTSTR>(&pszTitle), 0);
      SetWindowText(hwndDlg, pszTitle);
      // ...etc.

      return TRUE;  // set the default focus
    }
    // ...process other messages as necessary
  }
  return FALSE;  // we did not process the message
}