Advanced MFC Programming

Chapter 9. Font
Function CDocument::UpdateAllViews(…)
Function CDocument::UpdateAllViews(…) has three parameters, two of which have default values:
void CDocument::UpdateAllViews(CView *pSender, LPARAM lHint=0L, CObject *pHint=NULL);
By default, the update message will be sent to view, this will cause function CView::OnUpdate(…) to
be called:
void CView::OnUpdate(CView *pSender, LPARAM lHint, CObject *pHint);
All parameters passed to CDocument::UpdateAllViews(…) will be passed to this function. This
provides us a way to know what part of the client window needs to be updated. The updating hint can be
passed through either parameter lHint or pHint.
By default, CView::OnUpdate(…) will update the whole client area. If we want only a portion of the
client window to be updated, we need to bypass the default implementation. Within the overridden
funciton, we can use the hint to form a rectangle indicating the area needs to be updated, and use it to call
function CWnd::InvalidateRect(…).
Function CWnd::InvalidateRect(…) will cause only the specified rectangular area to be updated.
Defining Hints
Our next task is to divide the updating events into different categories and calculate the rectangle for
each situation. The following is a list of situations when only a portion of the client window needs to be
updated:
Activities
Delete a character using DELETE key
Paste
Input a character
Delete a character using BACK SPACE
key
Delete selection
Select a portion of the text
Unselect the text
Area needs to be updated
From the current caret to the end of text
Same as above
Same as above
From the character before the caret to the end of text
From the beginning of the selection to the end of text
The difference between the newly selected area and previously
selected area
The whole selected area
The last two situations are a little complicated. When the user makes selections, the newly selected
area may be smaller or larger than the old selected area. In either case, we only need to update the changed
area to avoid flickering (Figure 9-5).
Because of this, we need to add new variables to remember the old selection indices. In the sample,
two new variables and some functions are declared in class CGDIDoc as follows:
……
……
……
class CGDIDoc : public CDocument
{
protected:
int m_nSelIndexBgnOld;
int m_nSelIndexEndOld;
public:
}
int GetSelIndexBgnOld(){return m_nSelIndexBgnOld;}
int GetSelIndexEndOld(){return m_nSelIndexEndOld;}
int GetCaretIndex(){return m_nCaretIndex;}
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