Advanced MFC Programming

Chapter 14. Views
Another feature of this editor is Edit | Paste Special… command. Because the editor supports not only
text, but also graphic editing now, the paste command should support multiple-format data. If we execute
command Edit | Paste Special..., a dialog box will pop up indicating the available data formats contained
in the clipboard, from which we can make the selection. For example, if we paste a bitmap, we have the
choice to paste it either as bitmap format, metafile format or DIB format.
The third feature of this editor is font selection. We may want to format different portion of the text
using a different font. This is the default feature of class CRichEditView. The command ID that can be used
to format the selected text using a specific font is ID_FORMAT_FONT (class CRichEditView supports this ID).
So all we need to do is adding a Format | Font… command to menu IDR_MAINFRAME. With this simple
implementation, we are able to format the text with any font that is available in the system.
Although it is very easy to build a fully functional application with a lot of enticing features, it is
relatively difficult to make modifications. For example, the standard Wordpad application under
Windows has a ruler and a format bar, if we want to add these features, we need to add them by
ourselves.
Customizing File Open Dialog Box
Class CRichEditView and CRichEditDoc can handle not only rich text format, but also plain text
format (or ASCII format). By default, the two classes interpret input data using rich text format, if the
format is different, the file will not be loaded. To let the application also support plain text format, we need
to include multiple document types in “File Open” and “Save As” file dialog boxes, this gives the user an
option for specifying file type. Although we can register more than one type of document to implement
this, in the case of rich edit view, it is not an efficient way. This is because both formats are already
supported by class CRichEditDoc.
To implement customized “File Open” dialog box, we can override function
CWinApp::OnFileOpen(…). We need to provide “File Open” dialog box, let the user pick up a file name,
and pass this name to function CWinApp::OpenDocumentFile(…). Here we need to pay special attention to
file formats. Because we support more than one file format here, we need to implement a “File Open”
dialog box supporting multiple file filters, and inform document the file format that was selected by the
user. To customize a file open dialog box, we need the knowledge of Chapter 6; to let the document support
a different file format, we can set a Boolean type member variable of class CRichEditDoc:
CRichEditDoc::m_bRTF, which is a public member variable. If this variable is set to TRUE, the data in the
file will be treated as formatted data stream; if it is set to FALSE, the data will be treated as unformatted
data stream (plain ASCII text). We need to set this flag before function CWinApp::OpenDocumentFile(…) is
called.
The following code fragment shows how function CWordPadApp::OnFileOpen() is implemented in the
sample:
void CWordPadApp::OnFileOpen()
{
CFileDialog dlg(TRUE);
CString szName;
CRichEditDoc *pDoc;
}
dlg.m_ofn.lpstrFilter=STRING_FILTER;
dlg.m_ofn.nFilterIndex=1;
if(dlg.DoModal() == IDOK)szName=dlg.GetPathName();
pDoc=(CRichEditDoc *)(((CFrameWnd *)m_pMainWnd)->GetActiveDocument());
if(dlg.m_ofn.nFilterIndex == 1)
{
pDoc->m_bRTF=TRUE;
}
else pDoc->m_bRTF=FALSE;
OpenDocumentFile(szName);
We must map command ID_FILE_OPEN to this function in order to make it effective. In the sample,
WM_COMMAND message mapping for this command is customized as follows:
431