Advanced MFC Programming

Chapter 7. Common Dialog Boxes
DWORD nMaxFile;
LPTSTR lpstrFileTitle;
DWORD nMaxFileTitle;
LPCTSTR lpstrInitialDir;
LPCTSTR lpstrTitle;
DWORD Flags;
WORD nFileOffset;
WORD nFileExtension;
LPCTSTR lpstrDefExt;
DWORD lCustData;
LPOFNHOOKPROC lpfnHook;
LPCTSTR lpTemplateName;
} OPENFILENAME;
It has 20 members, which can all be used to customize the dialog box. In this and the following
sections, we are going to see how to use them to change the default behavior of the file dialog box.
File Extension Filter
One of the most important members in this structure is lpstrFilter, which lets us specify a user
defined filter for displaying files. Only those files whose extensions match one of the filters will be
displayed in the dialog box. We can specify as many filters as we want. Each filter is made up of two parts:
the text description and the filter string. The text description is used to give the user an idea about the type
of the files, the filter string usually contains wildcard characters that can be used to specify file types. For
example, if we want to display only bitmap files, the description could be “Bitmap File (*.bmp)” and the
filter string should be “*.bmp”. Filters are separated by zeros. Within a filter, the description text and the
filter string are also separated by a zero. For example, if we want to specify two filters, one is “*.cpp”,
another is for “*.htm”, we should set the filter like this:
lpstrFilter=“CPP File(*.cpp)\0*.cpp\0HTML File(*.htm)\0*.htm\0”;
In the above statement, “CPP File(*.cpp)\0*.cpp\0” is the first filter and “HTML File(*.htm)
\0*.htm\0” is the second filter.
A filter can select more than one type of files. If we specify this type of filter, the different file types
should be separated by a ‘;’ character. For example, in the above example, if we want the first filter to
select both “*.cpp” and “*.h” file, its filter string should be “*.cpp;*.h”.
Besides the standard filter, we can also specify a custom filter. In the file dialog boxes, the custom
filter will always be displayed in the first place of the filter list. To specify a custom filter, we can store the
filter string in a buffer, use member lpstrCustomFilter to store the buffer’s address, and use member
nMaxCustFilter to store the buffer’s size.
If we have a list of filters, we can use only one of them at any time. Member nFilterIndex lets us
specify which filter will be used as the initial one. Here the index to the first file filter is 1.
Retrieving File Names
After function CFileDialog::DoModal() is called, we can use CFileDialog::GetFileName() or
CFileDialog::GetPathName() to retrieve the file name selected by the user. The difference between the
two functions is that CFileDialog::GetFileName() returns full file name (including extension), and
CFileDialog::GetFilePath() returns full path name (file name plus directory names). There are some
other member functions that we can call to retrieve file extension, file title, etc.
File Open
Sample 7.1\CDB demonstrates how to use file dialog box and how to customize its standard styles. It
is a standard SDI application generated by Application Wizard. After the application is generated, a new
sub- menu File Dialog Box is added to mainframe menu IDR_MAINFRAME between View and Help. Two
new commands File Dialog Box | File Open and File Dialog Box | File Save are added to this sub-menu,
whose IDs are ID_FILEDIALOGBOX_FILEOPEN and ID_FILEDIALOGBOX_FILESAVE respectively. Two
WM_COMMAND message handlers are added to class CCDBDoc (the document class) for the new commands
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