Advanced MFC Programming

Chapter 11. Sample: Simple Paint
m_bmpDraw.GetBitmap(&bm);
rectBmp=CRect(0, 0, bm.bmWidth*nRatio, bm.bmHeight*nRatio);
}
return rectBmp.PtInRect(point);
First we retrieve the current image ratio, horizontal and vertical scrolled positions of the client
window. Then function ::GetCursorPos(…) is called to obtain the current position of mouse cursor.
Because the returned value of this function (a POINT type value) is measured in the coordinate system of the
desktop window (whole screen), we need to convert it to the coordinate system of the client window before
judging if the cursor is within the bitmap image. Next, the image rectangle is stored in variable rectBmp,
and function CRect::PtInRect(…) is called to make the judgment.
This function is called in WM_SETCURSOR message handler. The following is the implementation of the
corresponding function:
BOOL CGDIView::OnSetCursor(CWnd* pWnd, UINT nHitTest, UINT message)
{
if(m_bmpDraw.GetSafeHandle() != NULL)
{
if
(
MouseWithinBitmap() == TRUE &&
HTVSCROLL != nHitTest && HTHSCROLL != nHitTest
)
{
::SetCursor(AfxGetApp()->LoadStandardCursor(IDC_CROSS));
return TRUE;
}
}
return CScrollView::OnSetCursor(pWnd, nHitTest, message);
}
If the cursor is within the bitmap image and is over neither the horizontal scroll bar nor the vertical
scroll bar, we set the cursor to IDC_CROSS (a standard cursor). Otherwise by calling the default
implementation of function OnSetCursor(…), the cursor will be set to the default arrow cursor.
11.4 Tracker
Sample 11.4\GDI is based on sample 11.3\GDI.
Tracker can be implemented to let the user select a rectangular area very easily, and is widely used in
applications supporting OLE to provide a graphical interface that lets the user interact with OLE client
items. When implementing a tracker, we can select different styles. This can let the tracker be displayed
with a variety of visual effects such as hatched borders, resize handles, etc.
Tracker can also be applied to any normal application. In a graphic editor, tracker can be used to select
a rectangular region, move and drop it anywhere within the image. It can also be used to indicate the
selected rectangular area when we implement cut, copy and paste commands (Figure 11-4).
Implementing Tracker
Tracker is supported by MFC class CRectTracker. To enable a rectangular tracker, we need to first use
this class to declare a variable, then set its style. When the window owns the tracker is being painted, we
need to call a member function of CRectTracker to draw the tracker.
We can set the tracker to different styles. The style of tracker is specified by variable CRectTracker::
m_nStyle. The following values are defined in class CRectTracker and can be used to specify the border
styles of a tracker: CRectTracker::solidLine, CRectTracker::dottedLine, CRectTracker::
hatchedBorder. The following values can also be assigned to CRectTracker::m_nStyle to specify how the
tracker can be resized: CRectTracker::resizeInside, CRectTracker::resizeOutside. Finally,
CRectTracker::hatchInside can be assigned to CRectTracker::m_nStyle to specify if the hatched border
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