Advanced MFC Programming

Chapter 9. Font
We call ::GetCursorPos(…) and CWnd::ScreenToClient(…) to retrieve the current cursor position in
the client window’s coordinate system. Then functions CGDIDoc::GetTextHorSize() and CGDIDoc::
GetCaretVerSize() are called to retrieve the dimension of the text. If the mouse cursor is within this
rectangle, we call ::SetCursor(…) to change it to insertion cursor. In this case, we must return a TRUE
value to avoid this message from being further processed (by default the mouse cursor will be set to arrow
cursor).
Handling WM_LBUTTONDOWN to Move Caret
The caret can be moved when the current mouse cursor is an insertion cursor. To implement this, we
need to call function CGDIDoc::SetCaret(…) after receiving WM_LBUTTONDOWN message. In the sample, this
message handler is added through using Class Wizard, and the corresponding function CGDIView::
OnLButtonDown(…) is implemented as follows:
void CGDIView::OnLButtonDown(UINT nFlags, CPoint point)
{
CGDIDoc *ptrDoc;
}
ptrDoc=(CGDIDoc *)GetDocument();
if(::GetCursor() == m_hCur)ptrDoc->SetCaret(point);
CScrollView::OnLButtonDown(nFlags, point);
In this function, first we check if the mouse cursor is the insertion cursor. If not, it means that the
mouse is not over the text string. If so, we call function CGDIDoc::SetCaret(…) and pass current mouse
position to it. This will cause the caret to move to the new position.
9.8 One Line Text Editor, Step 5: Selection
Sample 9.8\GDI is based on sample 9.7\GDI.
Highlighting the Selected Text
The next feature we will add is to let the user select text using mouse. If this is implemented, it is easy
for us to add cut, copy and paste functionalities.
To add the selection feature, we need two new text indices: one indicates the beginning of the
selection, one indicates the end of the selection. In the sample, two variables along with two functions are
added to class CGDIView for this purpose:
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class CGDIDoc : public CDocument
{
protected:
int m_nTextHorSize;
int m_nSelIndexBgn;
int m_nSelIndexEnd;
public:
}
int GetTextHorSize(){return m_nTextHorSize;}
int GetSelIndexBgn(){return m_nSelIndexBgn;}
int GetSelIndexEnd(){return m_nSelIndexEnd;}
Here, variables m_nSelIndexBgn, m_nSelIndexEnd, functions CGDIDoc::GetSelIndexBgn() and
CGDIDoc::GetSelIndexEnd() are added to the class. Before the selection is made, there may exist two
situations: the text is currently being selected or there is no character being selected. To distiguish between
the two situations, let’s define that if any of m_nSelIndexBgn and m_nselIndexEnd is -1, or their values are
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