Adding Multiselection to TFileOpenDialogs ADVANCED

Date: 7 February 1997
Author: Brice VIDAL
Platform: 32 bits environement
In memory of: Carcass

Overview

• As you have perhaps noticed when selecting many files and then pressing the Open button, nothing happens. Well this is due to the fact that the FileName has a size fixed to _MAX_PATH. Changing this is not very difficult, much more can be done...

• Lost in the jungle of the flags? Perhaps you want to limit the length of a file name to 64 without dropping the multiselection capabilities. You can download the code here, it is completely documented so do not hesitate.

Changing the size of the FileName member

•     The TOpensSaveDialog::TData constructor can take parameters. The size of FileName can be changed via the constructor but you'll have to decide the amount you want to attribute to FileName.

#include <owl/opensave.h>

TOpenSaveDialog::TData FileData(
    (uint32)OFN_EXPLORER | OFN_ALLOWMULTISELECT,                     // the FLAGS
    (char*)"Your App Files (*.app)|*.app| All Files (*.*)|*.*|",    // the Filter
    (char*)"*.app",                                                 // the Custom Filter
    (char*)"C:\\BC5",                                               // the Initial Dir
    (char*)"app",                                                   // the Default Extension
    (int)500,                                                       // the Size of FileName
    (int)0);                                                        // the Filter Index

•     If you prefer you can acces the size diretly accessing the int MaxPath but remember that the FileName MUST be resized, if not you will have to face a GPF or worse... Personaly I do not recommend this method but you are free to use it. Another danger appears when the TOpenSaveDialog::TData destructor will try to delete FileName...

#include <owl/opensave.h>

TOpenSaveDialog::TData FileData;

FileData.Flags = OFN_EXPLORER | OFN_ALLOWMULTISELECT;

FileData.MaxPath = 500;

if(FileData.FileName)
    delete[] FileData.FileName;

FileData.FileName = new char[FileData.MaxPath];

Most common flags 

• OFN_ALLOWMULTISELECT: allows multiselection in the dialog box. If the dialog box is created by using a private template, the  definition of the File Name list box must contain the LBS_EXTENDEDSEL value. When this flag is set thFileName string is not always formatted in the same way: when using the OFN_EXPLORER flag, as seen before, each name is separated by a null terminator and the double null terminator indicates the end of the string ; when this flag isn't set then each name is separated by a space. Here's an example showing how to deal with the space delimiter:  

#include <cstring.h>

if(TFileOpenDialog(this, FileData).Execute()==ID_OK)
{
    char* p;
    p = strtok(FileData.FileName, ' ');

    string path(p);

    while(p = strtok(NULL, ' '))
    {
        string openName(p);
        openName = path + openName;
        OpenFile(openName.c_str());
    }
} 

• OFN_CREATEPROMPT asks the user if he or she wants to create the file if it does not exist.
  
  
• OFN_EXPLORER creates a dialog box which looks like the one in the overview section. With this flag your dialog box will look like the open dialog boxes from Win95, if you don't set this flag your dialog box will look like a normal open dailog box (Win3.x).
  
  
• OFN_FILEMUSTEXIST,OFN_PATHMUSTEXIST specifies that the user must type an existing file name, if this file does not exists a warning dialog box is created.
  
  
• OFN_HIDEREADONLY hides the Read Only check box.
  
  
• OFN_LONGNAMES, OFN_NOLONGNAMES forces the dialog box to use or not long file names. Those flags are ignored if OFN_EXPLORER is set.
  
  
• OFN_NOCHANGEDIR restores the current directory to its original value if the user has moved to another directory.
  
  
• OFN_NODEREFERENCELINKS formats the FileName string with the path to the *.lnk file and not with the path of the file to which it points.
  
  
• OFN_NONETWORKBUTTON hides and disables the Network button.
  
  
• OFN_NOVALIDATE does not check for invalid characters in the file name nor adds the default extension to the text.
  
  
• OFN_OVERWRITEPROMPT generates a dialog box if the file alredy exists.
  
  
• OFN_READONLY sets the state of the Read Only check box to checked.
  
  
• OFN_SHOWHELP shows the help button.

Going further

•     If you want to go further you have to step into the OWL code. You need to create your own TOpenSaveDialog, TFileOpenDialog and TFileSaveDialog. For this derive your class privately from TOpenSaveDialog and in your Init() call thi Init member of TOpenSaveDialog and then add what ever you want. See Microsoft's help file on ONPENFILENAME to know all what you can do. You also need a copy constructor and an operator =, have a look at opensave.h and at the advmulti.zip archive for more details.

#include <owl/opensave.h>

class TYourOpenSaveDialog : private TOpenSaveDialog
{
    // all you need

    protected:
        void Init(TResId templateID);

    // all you need
};

void TYourOpenSaveDialog::Init(TResId templateId)
{
    // call the usual Init

  TOpenSaveDialog::Init(templateID);

    // all you need
}

• For your open and save dialog you then need your own TFileSaveDialog and TFileOpenDialog derived from your TOpenSaveDialog. These classes need a DoExecute() which are similar to the ones of TFileOpenDialog and TFileSaveDialog. Here to you'll need a copy constructor and an operator =, and here too have a look at opensave.h and at the advmulti.zip archive for more details.

class TYourFileOpenDialog : public TYourOpenSaveDialog
{
    // all you need

    public:
        int DoExecute();

    // all you need
};

int TYourFileOpenDialog::DoExecute()
{
    // have a look at opensave.h
}