Advanced MFC Programming

Chapter 14. Views
used to distinguish between different type of files. However, some file types do not have registered icons
and some files contain icons within themselves (such as files with “.exe” or “.dll” extension).
Which Icon to Use
Windows always try to display a file using the appropriate icons. If a file contains icon itself, this
icon will be used. If a file doesn’t contain any icon but has registered icons (such as some special document
files like “*.bmp”, “*.doc”), the registered icons will be used. If no registered icons are found, a default
icon will be assigned to the file.
There is a shell function that can be used to retrieve the icon information for a file:
WINSHELLAPI DWORD WINAPI SHGetFileInfo
(
LPCTSTR pszPath, DWORD dwFileAttributes, SHFILEINFO FAR *psfi,
UINT cbFileInfo, UINT uFlags
);
Here parameter pszPath is a pointer to a string specifying the file path; dwFileAttributes specifies
the file attributes, and the file information can be retrieved into a SHFILEINFO type object which is pointed
by pointer psfi; cbFileInfo specifies the size of SHFILEINFO structure; uFlags specifies what information
is being retrieved. In our case, we can combine SHGFI_ICON with one of the following flags and pass the
result to parameter uFlags:
Flag
SHGFI_LARGEICON
SHGFI_SMALLICON
SHGFI_SHELLICONSIZE
SHGFI_SHELLICONSIZE | SHGFI_SMALLICON
Meaning
Retrieve large icon contained in the file
Retrieve small icon contained in the file
Retrieve shell large icon
Retrieve shell small icon
To display each file with embedded or registered icons, before adding an item to the list control, we
need to first customize the image list. If any icon is found by calling function ::SHGetFileInfo(), we will
add it to the image list. If we could not find an icon using this method, the default icon will be associated
with the corresponding file.
Sample
Sample 14.7\Explorer is based on sample 14.6\Explorer. In this sample, the embedded and registered
icons are retrieved for displaying files in the list view.
In the sample, a new member function is added for retrieving icons for a file:
HICON CExplorerView::GetIconFromFile(CString szFileName, UINT uFlags);
The returned value is an icon handle. Within this function, ::SHGetFileInfo(…) is called to get the
icon information of a file. The following is the implementation of this function:
HICON CExplorerView::GetIconFromFile(CString szFileName, UINT uFlags)
{
SHFILEINFO shfi;
::SHGetFileInfo(szFileName, 0, &shfi, sizeof(SHFILEINFO), SHGFI_ICON | uFlags);
}
return shfi.hIcon;
Function CExplorerView::ChangeDir() is modified as follows: after a file is found, function
CExplorerView::GetIconFromFile(…) is called to find its embedded or registered icons; if this is
successful, the newly obtained icons will be added to the image list and associated with the file; otherwise
the default images will be used. The following portion of function CExplorerView::ChangeDir() shows
how we try to find the embedded icons of a file:
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