Advanced MFC Programming

Chapter 11. Sample: Simple Paint
should be drawn outside or inside the rectangle. All the above styles can be combined together using bitwise
OR operation.
Tracker
Resize button
Resize button
Moving and Resizing Tracker
Figure 11-4. Tracker
The tracker’s position and dimension are stored in variable CRectTracker::m_rect. We can modify it
at any time to move the tracker or resize it. If this variable specifies a valid rectangle, we can draw the
tracker by calling function CRectTracker::Draw(…) and display it in a window.
To let user resize the tracker through clicking and dragging tracker’s resizing buttons (See Figure 11-
4), we need to handle WM_LBUTTONDOWN message and call function CRectTracker::HitTest(…) to find out
if the current mouse cursor hits any portion of the tracker. The following is the format of this function:
int CRectTracker::HitTest(CPoint point);
The following is a list of values that can be returned from this function along their meanings:
Valure
CRectTracker::hitNothing
CRectTracker::hitTopLeft
CRectTracker::hitTopRight
CRectTracker::hitBottomRight
CRectTracker:hitBottomLeft
CRectTracker:hitTop
CRectTracker:hitRight
CRectTracker:hitBottom
CRectTracker:hitLeft
CRectTracker:hitMiddle
Meaning
The mouse cursor is not over the tracker.
The mouse cursor is over the top-left resize button.
The mouse cursor is over the top-right resize button
The mouse cursor is over the bottom-right resize button
The mouse cursor is over the bottom-left resize button
The mouse cursor is over the resize button on the top border.
The mouse cursor is over the resize button on the right border.
The mouse cursor is over the resize button on the bottom border.
The mouse cursor is over the resize button on the left border.
The mouse cursor is within the tracker rectangle.
If mouse cursor hits any of the resize buttons, we can call CRectTracker::Track() to track the mouse
moving activities from now on until the left button is released. With this function, there is no need for us to
handle other two messages WM_MOUSEMOVE and WM_LBUTTONUP, because once it is called, the function will
not return until the left button is released. Of course, we can also write code to implement right button
tracking. When we call function CRectTrack::Track(), the tracker’s owner window should not set window
capture, otherwise the mouse message will not be routed to the tracker.
Customizing Cursor Shape
To let the mouse cursor shape change automatically when it is over tracker’s region, we need to call
function CRectTracker::SetCursor(…) inside window’s CWnd::OnSetCursor(…) function (in the window
that contains the tracker). If the function returns TRUE, it means that the cursor shape has already been
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