Advanced MFC Programming

Chapter 9. Font
}
szStr=szStr.Right(szStr.GetLength()-m_nCaretIndex);
m_szText+=szStr;
UpdateAllViews(NULL);
BackwardCaret();
}
}
else
{
if(m_nCaretIndex != m_szText.GetLength())
{
szStr=m_szText;
m_szText=m_szText.Left(m_nCaretIndex);
szStr=szStr.Right(szStr.GetLength()-m_nCaretIndex-1);
m_szText+=szStr;
UpdateAllViews(NULL);
}
}
To delete the character before the current caret, we divide the text into two sub-strings, delete the last
character of the first sub-string, and re-combine them. Then we update the view, and move caret one
character left. When deleting the character after the caret, we do not need to change the position of the
caret.
Message WM_CHAR
Now we need to use the above two member functions. In the sample, message WM_CHAR is handled to
implement keyboard input. The difference between WM_CHAR and WM_KEYDOWN messages is that WM_CHAR is
sent only for printable characters along with the following five keys: ESCAPE, TAB, BACK SPACE and
ENTER. Message WM_KEYDOWN will be sent for all types of key strokes.
In the sample, the message handler of WM_CHAR is CGDIView::OnChar(…), it is implemented as follows
in the sample:
void CGDIView::OnChar(UINT nChar, UINT nRepCnt, UINT nFlags)
{
CGDIDoc *ptrDoc;
}
ptrDoc=(CGDIDoc *)GetDocument();
if(nChar != VK_RETURN && nChar != VK_ESCAPE && nChar != VK_TAB)
{
if(nChar == VK_BACK)ptrDoc->DeleteChar(TRUE);
else ptrDoc->AddChar(nChar, nRepCnt);
}
CScrollView::OnChar(nChar, nRepCnt, nFlags);
We neglect the ENTER, TAB and ESCAPE key strokes. For BACK SPACE key stroke, we delete the
character before the current caret. For all other cases, we insert character at the current caret position.
The DELETE key stroke can not be detected by this message handler, we need to trap and handle it in
function CGDIView::OnKeyDown(…):
……
void CGDIView::OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags)
{
}
case VK_RIGHT:
{
ptrDoc->ForwardCaret();
break;
}
case VK_DELETE:
{
ptrDoc->DeleteChar(FALSE);
break;
}
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