VC++编程常见问题解答二十二.docx

VC+编程常见问题解答二十二问：CDC中的竖排文本?在OnDraw成员函数中我想让文本竖直对齐,但CDC类似乎不支持该处理答：如果你的竖直对齐是指旋转文本的话,下面的代码会对你有帮助: 该代码检查一个Check box控制,查看文本是否需要旋转./ m_pcfYTitle is a CFont* to the selected font./ m_bTotateYTitle is a bool (=TRUE if rotated)void CPage1:OnRotateytitle()LOGFONT lgf;m_pcfYTitle-GetLogFont(&lgf);m_bRotateYTitle= (CButton*)GetDlgItem(IDC_ROTATEYTITLE)-GetCheck()0;/ escapement is reckoned clockwise in 1/10ths of a degree:lgf.lfEscapement=-(m_bRotateYTitle*900);m_pcfYTitle-DeleteObject();m_pcfYTitle-CreateFontIndirect(&lgf);DrawSampleChart();注意如果你从CFontDialog中选择了不同的字体,你应该自己设定LOGFONT的lfEscapement成员.将初始化后的lfEscapement值传到CFontDialog中.A2:还有一段代码可参考:LOGFONT LocalLogFont;strcpy(LocalLogFont.lfFaceName, TypeFace);LocalLogFont.lfWeight = fWeight;LocalLogFont.lfEscapement = Orient;LocalLogFont.lfOrientation = Orient;if (MyFont.CreateFontIndirect(&LocalLogFont) cMyOldFont = cdc-SelectObject(&MyFont); 问：如何激活变灰的弹出菜单? 在设计菜单时设定为GRAYED的菜单项,如何在运行时激活它?答：请看下面的示例代码: void CMyView:OnRButtonDown(UINT nFlags, CPoint point) CScrollView:OnRButtonDown(nFlags, point); CMenu *menu, *popup; menu = new CMenu(); / load menu from resource file menu-LoadMenu( IDR_POPUPMENU ); popup = menu-GetSubMenu(0); / item 0 is DUMMY UINT nEnable; nEnable = MF_BYCOMMAND|MF_GRAYED; if( your test ) nEnable = MF_BYCOMMAND|MF_ENABLED; popup-EnableMenuItem( ID_YOUR_ID, nEnable ); /display menu ClientToScreen(&point); popup-TrackPopupMenu( TPM_LEFTALIGN | TPM_RIGHTBUTTON, point.x, point.y, this ); delete menu; 问：线程消息? 如何正确地在线程之间传送消息?答：下面的代码将会帮你的忙:void CThread:OnUserOpen( WPARAM wParm, LPARAM lParm ) UNUSED( wParm ) ; UNUSED( lParm ) ; AfxMessageBox(User Open, MB_OK|MB_ICONEXCLAMATION);当然,也别忘了以下声明:class CThread : public CWinThread DECLARE_DYNCREATE(CThread)protected: CThread(); / protected constructor used by dynamic creation afx_msg void OnUserOpen( WPARAM wParm, LPARAM lParm ); 问：TreeCtrl控制的显示速度太慢? 我从CTreeCtrl继承了一个TREE控制类,重载主要是为了改写每个节点的文本.我在 OnPaint函数中写了一些代码,但这严重地影响了TREE控制的滚动速度.答：OnPaint函数1.可见节点,对于GetFirstVisibleItem和GetNextVisibleItem来讲,是: a.根节点;b.父节点已展开的节点;因此,可见意味着没有被未展开的父节点隐藏.当节点滚动到客户外时,它对上述两 个函数来讲仍是可见的.2.当TREE的内容改变时,它默认只将变为可见的节点重绘.另外其它已经是可见的节点 没有必要重绘,TREE只是滚动DC的位图而已.上面的意思是不要绘制你不需要看的节点,那会导致速度降低.建议,测试节点矩形是否 在客户区,使得只有需要绘制的节点才会被绘制.void CIndentTree:OnPaint() CPaintDC dc(this); / device context for painting HTREEITEM hItem = NULL; DRAWITEMSTRUCT dis; CRect rc; / redraw only visible items with indentation for( hItem = GetFirstVisibleItem(); hItem; hItem = GetNextVisibleItem( hItem ) ) if( !GetItemRect( hItem, rc, FALSE ) ) continue; if( rc.top dc.m_ps.rcPaint.top &=20 rc.left dc.m_ps.rcPaint.left ) dis.hwndItem = (HWND)hItem; dis.rcItem = rc; OnDrawItem(0, &dis, &dc); OnDrawItem函数1.删掉如下代码: IMAGEINFO*