visual c++编程技巧之七.htm

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<P><FONT face="Times New Roman" size=+0>VARIABLE_PITCH | FF-SWISS,_T 
("Arial"));</FONT> </P>
<P><A name=tip52></A><B><FONT size=+2><FONT 
face="Times New Roman">52</FONT><FONT face=黑体>、如何计算一个串的大小</FONT></FONT></B> </P>
<P><FONT size=+0>函数<FONT face="Times New Roman">CDC:: Det text Extent 
</FONT>根据当前选择的字体计算一个串的高度和宽度。如果使用的不是系统字体而是其他字体，则在调用<FONT 
face="Times New Roman">GetTextExtent</FONT>之前将字体选进设备上下文中是很重要的，否则计算高度和宽度时将依据系统字体，由此得出的结果当然是不正确的。下述样板程序当改变下压按钮的标题时动态调整按钮的大小，按钮的大小由按钮的字体和标题的大小而定。响应消息<FONT 
face="Times New Roman">WM_SETTEXT</FONT>时调用<FONT 
face="Times New Roman">OnSetText</FONT>，该消息使用<FONT 
face="Times New Roman">ON_MESSAE</FONT>宏指令定义的用户自定义消息。</FONT> </P>
<P><FONT face="Times New Roman" size=+0>LRESULT CMyButton:: OnSettext (WPARAM 
wParam, LPARAM lParam)</FONT> </P>
<P><FONT face="Times New Roman" size=+0>{</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Pass message to window 
procedure.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>LRESULT bResult=CallWindowProc 
(*GetSuperWndProcAddr (),</FONT> </P>
<P><FONT face="Times New Roman" size=+0>m_hWnd, GetCurrentMessage () 
-&gt;message,wParam,lParam);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Get title of push button.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CString strTitle;</FONT> </P>
<P><FONT face="Times New Roman" size=+0>GetWindowText (strTitle);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Select current font into device 
context.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CDC* pDC=GetDc ();</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CFont*pFont=GetFont ();</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CFont*pOldFont=pDC-&gt;SelectObject 
(pFont);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Calculate size of title.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CSize size=pDC-&gt;GetTextExent 
(strTitle,strTitle.GetLength ());</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Adjust the button's size based on its 
title.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Add a 5-pixel border around the 
button.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>SetWindowPos (NULL, 0, 0, size.cx+10, 
size.cy+10,</FONT> </P>
<P><FONT face="Times New Roman" size=+0>SWP_NOMOVE | SWP_NOZORDER | 
SWP_NOACTIVATE);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Clean up.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>pDC-&gt;SelectFont (pOldFont);</FONT> 
</P>
<P><FONT face="Times New Roman" size=+0>ReleaseDC (pDC);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>return bResult;</FONT> </P>
<P><FONT face="Times New Roman" size=+0>}</FONT> </P>
<P><A name=tip53></A><B><FONT size=+2><FONT 
face="Times New Roman">53</FONT><FONT face=黑体>、如何显示旋转文本</FONT></FONT></B> </P>
<P><FONT size=+0>只要用户使用<FONT face="Times New Roman">TrueType</FONT>或者<FONT 
face="Times New Roman">GDI</FONT>笔或字体就可以显示旋转文本<FONT 
face="Times New Roman">(</FONT>有些硬件设备也支持旋转光栅字体）。<FONT 
face="Times New Roman">LOGFONT</FONT>结构中的<FONT 
face="Times New Roman">ifEscapement</FONT>成员指定了文本行和<FONT 
face="Times New Roman">x</FONT>轴的角度，角度的单位是十分之一度而不是度，例如，<FONT 
face="Times New Roman">ifEscapement</FONT>为<FONT 
face="Times New Roman">450</FONT>表示字体旋转<FONT 
face="Times New Roman">45</FONT>度。为确保所有的字体沿坐标系统的同一方向旋转，一定要设置<FONT 
face="Times New Roman">ifEscapement</FONT>成员的<FONT 
face="Times New Roman">CLIP_LH_ANGLES</FONT>位，否则，有些字体可能反向旋转。下例使用了<FONT 
face="Times New Roman">14</FONT>点<FONT 
face="Times New Roman">Arial</FONT>字体每间隔<FONT 
face="Times New Roman">15</FONT>度画一个串。</FONT> </P>
<P><FONT face="Times New Roman" size=+0>void CSampleView:: OnDraw (CDC* 
pDC)</FONT> </P>
<P><FONT face="Times New Roman" size=+0>{</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Determine the size of the 
window.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CRect rcClient;</FONT> </P>
<P><FONT face="Times New Roman" size=+0>GetClientRect (rcClient);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Create sample string.</FONT> </P>
<P><FONT size=+0><FONT face="Times New Roman">CString str (_T 
("Wheeee</FONT>．．．<FONT face="Times New Roman">I am rotating!"));</FONT></FONT> 
</P>
<P><FONT face="Times New Roman" size=+0>//Draw transparent, red text.</FONT> 
</P>
<P><FONT face="Times New Roman" size=+0>pDC-&gt;SetBkMode (TRANSPARENT);</FONT> 
</P>
<P><FONT face="Times New Roman" size=+0>pDC-&gt;SetTextColor (RGB 
(255,0,0));</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CFont font; //font object</FONT> </P>
<P><FONT face="Times New Roman" size=+0>LOGFONT stFont; //font definition</FONT> 
</P>
<P><FONT face="Times New Roman" size=+0>//Set font attributes that will not 
change.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>memset (&amp;stFont, 0, sizeof 
(LOGFONT));</FONT> </P>
<P><FONT face="Times New Roman" size=+0>stFont.ifheight=MulDiv (14, 
-pDC-&gt;GetDeviceCaps (LOGPIXELSY), 72);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>stFont.ifWeight=FW_NORMAL;</FONT> </P>
<P><FONT face="Times New Roman" 
size=+0>stFont.ifClipPrecision=LCIP_LH_ANGLES;</FONT> </P>
<P><FONT face="Times New Roman" size=+0>strcpy (stFont.lfFaceName, 
"Arial");</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Draw text at 15degree 
intervals.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>for (int nAngle=0; nAngle&lt;3600; 
nAngle+=150)</FONT> </P>
<P><FONT face="Times New Roman" size=+0>{</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Specify new angle.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>stFont.lfEscapement=nAngle;</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Create and select font into dc.</FONT> 
</P>
<P><FONT face="Times New Roman" size=+0>font.CreateFontIndirect 
(&amp;stfont);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CFont* pOldFont=pDC-&gt;SelectObject 
(&amp;font);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Draw the text.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>pDC-&gt;SelectObject (pOldFont);</FONT> 
</P>
<P><FONT face="Times New Roman" size=+0>font.DelectObjext ();</FONT> </P>
<P><FONT face="Times New Roman" size=+0>}</FONT> </P>
<P><FONT face="Times New Roman" size=+0>}</FONT> </P>
<P><A name=tip54></A><FONT face=黑体 size=+2>54、如何正确显示包含标签字符的串</FONT> </P>
<P><FONT size=+0>调用<FONT 
face="Times New Roman">GDI</FONT>文本绘画函数时需要展开标签字符，这可以通过调用<FONT 
face="Times New Roman">CDC:: TabbedTextOut</FONT>或者<FONT 
face="Times New Roman">CDC:: DrawText</FONT>并指定<FONT 
face="Times New Roman">DT_EXPANDTABS</FONT>标志来完成。<FONT 
face="Times New Roman">TabbedTextOut</FONT>函数允许指定标签位的数组，下例指定每<FONT 
face="Times New Roman">20</FONT>设备单位展开一个标签：</FONT> </P>
<P><FONT face="Times New Roman" size=+0>void CSampleView:: OnDraw (CDC* 
pDC)</FONT> </P>
<P><FONT face="Times New Roman" size=+0>{</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CTestDoc* pDoc=GetDocument ();</FONT> 
</P>
<P><FONT face="Times New Roman" size=+0>ASSERT_VALID (pDoC);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CString str;</FONT> </P>
<P><FONT face="Times New Roman" size=+0>str.Format (_T 
("Cathy\tNorman\tOliver"));</FONT> </P>
<P><FONT face="Times New Roman" size=+0>int nTabStop=20; //tabs are every 20 
pixels</FONT> </P>
<P><FONT face="Times New Roman" size=+0>pDC-&gt;TabbedtextOut (10, 10, str, 1, 
&amp;nTabStop, 10);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>}</FONT> </P>
<P><A name=tip55></A><B><FONT size=+2><FONT 
face="Times New Roman">55</FONT><FONT 
face=黑体>、串太长时如何在其末尾显示一个省略号</FONT></FONT></B> </P>
<P><FONT size=+0>调用<FONT face="Times New Roman">CDC:: DrawText</FONT>并指定<FONT 
face="Times New Roman">DT_END_ELLIPSIS</FONT>标志，这样就可以用小略号取代串末尾的字符使其适合于指定的边界矩形。如果要显示路径信息，指定<FONT 
face="Times New Roman">DT_END_ELLIPSIS</FONT>标志并省略号取代串中间的字符。</FONT> </P>
<P><FONT face="Times New Roman" size=+0>void CSampleView:: OnDraw (CDC* 
pDC)</FONT> </P>
<P><FONT face="Times New Roman" size=+0>{</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CTestDoc* pDoc=GetDocument ();</FONT> 
</P>
<P><FONT face="Times New Roman" size=+0>ASSERT_VALID (pDoc);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Add ellpsis to end of string if it 
does not fit</FONT> </P>
<P><FONT face="Times New Roman" size=+0>pDC-&gt;Drawtext (CString ("This is a 
long string"),</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CRect (10, 10, 80, 30), DT_LEFT | 
DT_END_ELLIPSIS);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Add ellpsis to middle of string if it 
does not fit</FONT> </P>
<P><FONT face="Times New Roman" size=+0>pDC-&gt;DrawText (AfxgetApp () 
-&gt;m_pszhelpfilePath,</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CRect (10, 40, 200, 60), DT_LEFT | 
DT_PATH_ELLIPSIS);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>}</FONT> </P>
<P><A name=tip56></A><B><FONT size=+2><FONT 
face="Times New Roman">56</FONT><FONT face=黑体>、如何快速地格式化一个</FONT><FONT 
face="Times New Roman">CString</FONT><FONT face=黑体>对象</FONT></FONT></B> </P>
<P><FONT size=+0>调用<FONT face="Times New Roman">CString:: 
Format</FONT>，该函数和<FONT 
face="Times New Roman">printf</FONT>函数具有相同的参数，下例说明了如何使用<FONT 
face="Times New Roman">Format</FONT>函数：</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Get size of window.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CRect rcWindow;</FONT> </P>
<P><FONT face="Times New Roman" size=+0>GetWindowRect (rcWindow);</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Format message string.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>CString strMessage;</FONT> </P>
<P><FONT face="Times New Roman" size=+0>strMessage.Format (_T ("Window Size (%d, 
%d)"),</FONT> </P>
<P><FONT face="Times New Roman" size=+0>rcWindow.Width (), rcWindow.Height 
());</FONT> </P>
<P><FONT face="Times New Roman" size=+0>//Display the message.</FONT> </P>
<P><FONT face="Times New Roman" size=+0>MessageBox (strmessage);</FONT> </P>
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