工作中总结的编程小技巧[转]

[转自：http://blog.csdn.net/GISsirclyx/archive/2009/10/29/4744325.aspx]

技巧一：int-->bool要注意的！
bool a=255;
bool b= 254;
理论上应该认为a==b，但是根据编译器的不同，结果可能完全不一样
所以更好的写法是
char ch =1; 或者0
bool a = (0 != atoi(ch));

技巧二：将std::string转int,double
先利用c_str()转成C string，再用atoi()与atof()

技巧三：const_cast操作符可以强置去除const指针的const属性

技巧四：CString读取文本的每一行
CStdioFile LogIDFile;
char* pFileName = "Log.txt ";
CString strtemp;
if( LogIDFile.Open( pFileName, CFile::modeRead ))
{
LogIDFile.SeekToBegin();
LogIDFile.ReadString(strtemp);
}
LogIDFile.Close();

技巧五：win32下给任何一个句柄添加消息处理函数：
为了简单假如在About对话框里贴了一个 IDC_STATIC_1。在IDC_STATIC_1上挂了一个 IDB_BITMAP1。
IDC_STATIC_1 控件属性，“通知”=Notify设为TRUE。
有了上面的假设后，就可以用下面的程序控制picture的全部行为。

LONG OldPicProc;
LRESULT CALLBACK PicProc( HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam )
{
switch( message )
{
case WM_RBUTTONDOWN:
{
WORD xPos = LOWORD(lParam);
WORD yPos = HIWORD(lParam);
}
break;
}
return CallWindowProc((WNDPROC)OldPicProc, hWnd, message, wParam, lParam);
}

LRESULT CALLBACK About( HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam )
{
switch( message )
{
case WM_INITDIALOG:
{
HWND hWnd = GetDlgItem(hDlg, IDC_STATIC_1);
OldPicProc = SetWindowLong(hWnd, GWL_WNDPROC, (LONG)PicProc);
}

return TRUE;

case WM_COMMAND:
if( LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL )
{
EndDialog(hDlg, LOWORD(wParam));
return TRUE;
}
break;
}
return FALSE;
}

技巧六：屏幕坐标转三维坐标（反变换的过程）
void GetOGLPos(int x, int y, double * posX, double * posY, double * posZ)
{
GLint viewport[4];
GLdouble projection[16];
GLfloat winX, winY, winZ;

glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
glGetDoublev( GL_PROJECTION_MATRIX, projection );
glGetIntegerv( GL_VIEWPORT, viewport );

winX = (float)x;
winY = (float)viewport[3] - (float)y;
glReadPixels( x, int(winY), 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ );

gluUnProject( winX, winY, winZ, modelview, projection, viewport, posX, posY, posZ);
}

技巧七 宽字符字符串转多字节字符串
//===方法1
TCHAR tcScriptName[MAX_PATH];
tcScriptName = "filename";
size_t i;
char tmp[MAX_PATH];
mbstate_t mbstate;

// Reset to initial shift state
::memset((void*)&mbstate, 0, sizeof(mbstate));

const wchar_t* wt = tcScriptName;
wcsrtombs_s(&i, tmp, MAX_PATH, &wt, MAX_PATH,&mbstate);
//===方法2
char * input = null;
wchar_t wc_input[MAX_USERNAME_LEN] = L"test";

int nLen = WideCharToMultiByte( CP_ACP, 0, wc_input, -1, NULL, 0, NULL, NULL );
int i = wcslen(wc_input)*sizeof(wchar_t);
input = (char*)realloc(input,i+1);
if (!input)
{
free(input);
input = (char*)malloc(i + 1);
}
WideCharToMultiByte( CP_ACP, 0, wc_input, -1, input, nLen, NULL, NULL );

技巧八 获得界面上所有控件
CWnd *pWnd = this->GetWindow( GW_CHILD );
while( pWnd )
{
if( pWnd->IsKindOf( RUNTIME_CLASS(CEdit) ) )
pWnd->ShowWindow(SW_SHOW);
pWnd = pWnd->GetWindow( GW_HWNDNEXT );
}

技巧九 判断基类指针指向的派生类类型

方法一：
class A
{
public:
virtual int get_type_id()
{
return 0;
}
};

class B: public A
{
public:
int get_type_id()
{
return 1;
}
};

方法二：
用RTTI
class A
{
public:
virtual ~A(){} //必须

};

class B: public A
{
};

int main()
{
A * p = new B;
bool p_is_B = (typeid(B) == typeid(*p));
std::cout<<p_is_B<<std::endl;

p_is_B = (dynamic_cast<B*>(p) != 0);
std::cout<<p_is_B<<std::endl;
}

技巧十 窗口ID，句柄，指针三者相互转换函数
ID--HANDLE--HWND三者之间的互相转换
===============
id->句柄
hWnd = ::GetDlgItem(hParentWnd,id);
===============
id->指针
CWnd::GetDlgItem();
===============
句柄->id
id = GetWindowLong(hWnd,GWL_ID);
===============
句柄->指针
CWnd *pWnd=CWnd::FromHandle(hWnd);
===============
指针->ID
id = GetWindowLong(pWnd->GetSafeHwnd,GWL_ID);
=================
指针->句柄
hWnd=cWnd.GetSafeHandle() or mywnd->m_hWnd;

（不断增加ing）