Advanced MFC Programming

Chapter 13. Adding Special Features to Application
bottom position = top position + vertical size of the caption
If we use window DC, the coordinates of the window’s top-left corner are (0, 0), this will simplify our
calculation.
Please note that we must use class CWindowDC to create DC for painting the non-client area rather than
using class CClientDC. Class CClientDC is designed to let us paint only within a window’s client area, so
its origin is located at left-top corner of the client window. Class CWindowDC can let us paint the whole
window, including both client and non-client area.
Sample 13.5\Cap
Sample application 13.5\Cap demonstrates this technique. It is a standard SDI application generated by
Application Wizard, and its caption window is painted yellow no matter what the corresponding system
color is (The default caption bar color can be customized by the user). The modifications made to the
application are all within class CMainFrame, and there are altogether four message handlers added to the
application: CMainFrame::OnNcPaint() for message WM_NCPAINT, CMainFrame::OnNcActivate(…) for
message WM_NCACTIVATE, CMainFrame::OnSetText() for message WM_SETTEXT and CMainFrame::
OnSysCommand(…) for message WM_SYSCOMMAND.
The function implemented for drawing caption text is CMainFrame::DrawCaption(…). This function
has one COLORREF type parameter color, which will be used as the text background. Within this function,
several system metrics are obtained, which will be used to calculate caption text area later:
……
……
nCapButtonX=::GetSystemMetrics(SM_CXSIZE);
nBorderX=::GetSystemMetrics(SM_CXBORDER);
nFrameX=::GetSystemMetrics(SM_CXFRAME);
nFrameY=::GetSystemMetrics(SM_CYFRAME);
szCaption.LoadString(AFX_IDS_APP_TITLE);
szCaption=GetActiveDocument()->GetTitle()+”_”+szCaption;
The caption text is obtained by combining the name of currently opened document with the string
stored in resource AFX_IDS_APP_TITLE. Here resource AFX_IDS_APP_TITLE stores application name, and
function CDocument::GetTitle() returns the name of currently opened document.
Then the area where we can put caption text is calculated and stored in a local variable rectDraw.
Before drawing the text, we need to fill it with the background color:
……
……
GetWindowRect(rect);
rectDraw.left=nCapButtonX+nBorderX+nFrameX;
rectDraw.top=nFrameY;
rectDraw.right=rect.Width()-3*nCapButtonX-nFrameX-nBorderX;
rectDraw.bottom=rectDraw.top+::GetSystemMetrics(SM_CYSIZE);
dc.FillSolidRect(rectDraw, color);
Since the DC is created using class CWindowDC, the coordinates of the window’s origin are (0, 0).
Before drawing the text, we need to set the text background mode to transparent. Also, in the sample, when
the caption text is being drawn, it is centered instead of being aligned left:
……
……
dc.FillSolidRect(rectDraw, color);
nBkMode=dc.SetBkMode(OPAQUE);
dc.DrawText(szCaption, rectDraw, DT_CENTER);
dc.SetBkMode(nBkMode);
Function CMainFrame::DrawCaption() is called in several places. When WM_NCACTIVATE message is
received and the window state is about to become inactive, we paint the caption bar with cyan color. When
WM_NCPAINT message is received, the caption bar is painted with yellow color.
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