Advanced MFC Programming

Chapter 9. Font
When we cut data to the clipboard, we also need to delete the selected text. So first a new function
DeleteSelection() is declared in class CGDIDoc, it can be called to delete the currently selected text:
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class CGDIDoc : public CDocument
{
public:
}
BOOL DeleteSelection();
Function CGDIDoc::DeleteSelection() is implemented as follows:
BOOL CGDIDoc::DeleteSelection()
{
CString szStr;
int nSel;
int nNum;
if
(
m_nSelIndexEnd == -1 ||
m_nSelIndexBgn == -1 ||
m_nSelIndexEnd == m_nSelIndexBgn
)return FALSE;
if(m_nSelIndexEnd > m_nSelIndexBgn)
{
nSel=m_nSelIndexBgn;
nNum=m_nSelIndexEnd-m_nSelIndexBgn;
}
else
{
nSel=m_nSelIndexEnd;
nNum=m_nSelIndexBgn-m_nSelIndexEnd;
}
szStr=m_szText.Left(nSel);
m_szText=m_szText.Mid(nSel+nNum);
m_szText=szStr+m_szText;
m_nCaretIndex=nSel;
UpdateAllViews(NULL);
GetCGDIView()->RedrawCaret();
m_nSelIndexBgn=m_nSelIndexEnd=-1;
}
return TRUE;
When there is no currently selected text, the function does nothing. Otherwise we proceed to delete the
selected text.
Because the ending selection index may be less than the beginning selection index, first we set the
value of local variable nSel to the smaller selection index, and set the number of selected characters to
another local variable nNum. Then the unselected text is combined together, and the caret index is adjusted.
Next the caret and the client window are updated. Finally, both selection indices are set to -1, this indicates
that currently there is no text being selected.
We can call this function when DELETE key is pressed to delete the selected text, also we can call it
when the selected text is being cut to the clipboard. In the sample, function CGDIDoc::DeleteChar() is
modified as follows:
void CGDIDoc::DeleteChar(BOOL bBefore)
{
CString szStr;
if(DeleteSelection() == TRUE)return;
if(bBefore == TRUE)
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