两种获取HDC的方法和TextOut输出

windows32挺好玩的，买本windows32的书，慢慢啃，理解windows32到底是怎么工作的，尤其是消息循环这一块，其实windows32最重要的就是你写的proc函数，消息循环接收任何消息,都调用你写的windowproc函数，如果有人觉得windows32入门很痛苦，建议大家看看孙鑫的c++20讲之第一讲，保证有收获。

windows32不用重头到尾都自己敲代码，可以有技巧的使用MSDN，可以复制函数原型... 写了第一遍了，第二遍就可以拷贝第一遍写的，然后改就行了。

有两种方法可以获取HDC（设备环境句柄）

1成对使用BeginPaint(hwnd,&ps),EndPaint(hwnd,&ps);

2成对使用GetDC(hwnd),ReleaseDC(hwnd,hdc);

就在刚刚，我分别用了两种方法测试了下效果：

#include<windows.h>LRESULT CALLBACK WindowProc(  HWND hwnd,      // handle to window  UINT uMsg,      // message identifier  WPARAM wParam,  // first message parameter  LPARAM lParam   // second message parameter);int WINAPI WinMain(  HINSTANCE hInstance,      // handle to current instance  HINSTANCE hPrevInstance,  // handle to previous instance  LPSTR lpCmdLine,          // command line  int nCmdShow              // show state  ){static TCHAR szAppName[]=TEXT("AppName");HWND hwnd;MSG msg;WNDCLASS wndclass;wndclass.cbClsExtra=0;wndclass.cbWndExtra=0;wndclass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);wndclass.hCursor=LoadCursor(NULL,IDC_ARROW);wndclass.hIcon=LoadIcon(NULL,IDI_APPLICATION);wndclass.hInstance=hInstance;wndclass.lpfnWndProc=WindowProc;wndclass.lpszClassName=szAppName;wndclass.lpszMenuName=NULL;wndclass.style=CS_HREDRAW|CS_VREDRAW;if(!RegisterClass(&wndclass)){MessageBox(NULL,TEXT("This program requires Windows NT"),szAppName,MB_ICONERROR);}hwnd=CreateWindow(  szAppName,  // registered class name  TEXT("This is title"), // window name  WS_OVERLAPPEDWINDOW,        // window style  CW_USEDEFAULT,                // horizontal position of window  CW_USEDEFAULT,                // vertical position of window  CW_USEDEFAULT,           // window width  CW_USEDEFAULT,          // window height  NULL,      // handle to parent or owner window  NULL,          // menu handle or child identifier  hInstance,  // handle to application instance  NULL        // window-creation data);ShowWindow(hwnd,nCmdShow);UpdateWindow(hwnd);while(GetMessage(&msg,NULL,0,0)){TranslateMessage(&msg);DispatchMessage(&msg);}return msg.wParam;}LRESULT CALLBACK WindowProc(  HWND hwnd,      // handle to window  UINT uMsg,      // message identifier  WPARAM wParam,  // first message parameter  LPARAM lParam   // second message parameter){HDC hdc;PAINTSTRUCT ps;TCHAR zsBuffer[20];switch(uMsg){case WM_CREATE://hdc=GetDC(hwnd);//TextOut(hdc,0,0,TEXT("hello,world"),strlen("hello,world"));//ReleaseDC(hwnd,hdc);return 0;case WM_PAINT:hdc=BeginPaint(hwnd,&ps);TextOut(hdc,0,0,TEXT("WM_PAINT"),strlen("WM_PAINT"));EndPaint(hwnd,&ps);return 0;case WM_DESTROY:PostQuitMessage(0);return 0;}return DefWindowProc(hwnd,uMsg,wParam,lParam);}

跟预想的效果一样。

但是：

#include<windows.h>LRESULT CALLBACK WindowProc(  HWND hwnd,      // handle to window  UINT uMsg,      // message identifier  WPARAM wParam,  // first message parameter  LPARAM lParam   // second message parameter);int WINAPI WinMain(  HINSTANCE hInstance,      // handle to current instance  HINSTANCE hPrevInstance,  // handle to previous instance  LPSTR lpCmdLine,          // command line  int nCmdShow              // show state  ){static TCHAR szAppName[]=TEXT("AppName");HWND hwnd;MSG msg;WNDCLASS wndclass;wndclass.cbClsExtra=0;wndclass.cbWndExtra=0;wndclass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);wndclass.hCursor=LoadCursor(NULL,IDC_ARROW);wndclass.hIcon=LoadIcon(NULL,IDI_APPLICATION);wndclass.hInstance=hInstance;wndclass.lpfnWndProc=WindowProc;wndclass.lpszClassName=szAppName;wndclass.lpszMenuName=NULL;wndclass.style=CS_HREDRAW|CS_VREDRAW;if(!RegisterClass(&wndclass)){MessageBox(NULL,TEXT("This program requires Windows NT"),szAppName,MB_ICONERROR);}hwnd=CreateWindow(  szAppName,  // registered class name  TEXT("This is title"), // window name  WS_OVERLAPPEDWINDOW,        // window style  CW_USEDEFAULT,                // horizontal position of window  CW_USEDEFAULT,                // vertical position of window  CW_USEDEFAULT,           // window width  CW_USEDEFAULT,          // window height  NULL,      // handle to parent or owner window  NULL,          // menu handle or child identifier  hInstance,  // handle to application instance  NULL        // window-creation data);ShowWindow(hwnd,nCmdShow);UpdateWindow(hwnd);while(GetMessage(&msg,NULL,0,0)){TranslateMessage(&msg);DispatchMessage(&msg);}return msg.wParam;}LRESULT CALLBACK WindowProc(  HWND hwnd,      // handle to window  UINT uMsg,      // message identifier  WPARAM wParam,  // first message parameter  LPARAM lParam   // second message parameter){HDC hdc;PAINTSTRUCT ps;TCHAR zsBuffer[20];switch(uMsg){case WM_CREATE://hdc=GetDC(hwnd);//TextOut(hdc,0,0,TEXT("hello,world"),strlen("hello,world"));//ReleaseDC(hwnd,hdc);return 0;case WM_PAINT:hdc=GetDC(hwnd);TextOut(hdc,0,0,TEXT("WM_PAINT"),strlen("WM_PAINT"));ReleaseDC(hwnd,hdc);return 0;case WM_DESTROY:PostQuitMessage(0);return 0;}return DefWindowProc(hwnd,uMsg,wParam,lParam);}

窗体中显示了WM_PAINT，但是明显的看到一直在闪屏。

TextOut是用来输出的：

看看它的定义：

TextOut和DrawText都是用来写的函数，这两者有什么区别呢？其实只要查查MSDN这两个函数原型，你就都清楚了，确定具体位置的用TextOut，确定区域的用DrawText

有了函数原型了，一切都迎刃而解了。

哪位仁兄帮下忙，说一下上面两种方法获取的HDC有什么不同，为什么会出现闪屏？

已经找到答案了：

case WM_PAINT:hdc=BeginPaint(hwnd,&ps);//TextOut(hdc,0,0,TEXT("WM_PAINT"),strlen("WM_PAINT"));//TextOut(hdc,200,200,TEXT("WM_PAINT"),strlen("WM_PAINT"));//SetTextAlign(hdc,TA_RIGHT);for(int i=0;i<10;++i){for(int j=0;j<10;++j){TextOut(hdc,i*50,j*50,TEXT("HELLO"),strlen("HELLO"));}}EndPaint(hwnd,&ps);return 0;

也可是使用TextOut输出变量：

case WM_PAINT:hdc=BeginPaint(hwnd,&ps);//TextOut(hdc,0,0,TEXT("WM_PAINT"),strlen("WM_PAINT"));//TextOut(hdc,200,200,TEXT("WM_PAINT"),strlen("WM_PAINT"));SetTextAlign(hdc,TA_RIGHT);for( i=0;i<10;++i){for( j=0;j<10;++j){TextOut(hdc,i*50,j*50,szBuffer,wsprintf(szBuffer,TEXT("%d"),i*j));}}//TextOut(hdc,200,200,szBuffer,wsprintf(szBuffer,TEXT("%d"),i*j));EndPaint(hwnd,&ps);return 0;

 

TEXTMERIC相关操作：

LRESULT CALLBACK WindowProc(  HWND hwnd,      // handle to window  UINT uMsg,      // message identifier  WPARAM wParam,  // first message parameter  LPARAM lParam   // second message parameter){static int cxClient,cyClient;HDC hdc;PAINTSTRUCT ps;int i=50,j=20;TCHAR szBuffer[20];TEXTMETRIC tm;switch(uMsg){case WM_CREATE://hdc=GetDC(hwnd);//TextOut(hdc,0,0,TEXT("hello,world"),strlen("hello,world"));//ReleaseDC(hwnd,hdc);return 0;case WM_PAINT:hdc=BeginPaint(hwnd,&ps);GetTextMetrics(hdc,&tm);TextOut(hdc,0,0,szBuffer,wsprintf(szBuffer,TEXT("%d"),tm.tmAveCharWidth));//字符宽度TextOut(hdc,0,50,szBuffer,wsprintf(szBuffer,TEXT("%d"),tm.tmHeight+tm.tmExternalLeading));//字符高度EndPaint(hwnd,&ps);return 0;case WM_SIZE:hdc=BeginPaint(hwnd,&ps);cxClient=LOWORD(lParam);cyClient=HIWORD(lParam);GetTextMetrics(hdc,&tm);TextOut(hdc,0,100,szBuffer,wsprintf(szBuffer,TEXT("%d"),cxClient/tm.tmAveCharWidth));//一行最多显示多少个字符TextOut(hdc,0,150,szBuffer,wsprintf(szBuffer,TEXT("%d"),cyClient/(tm.tmHeight+tm.tmExternalLeading)));//一列最多显示多少字符EndPaint(hwnd,&ps);return 0;case WM_DESTROY:PostQuitMessage(0);return 0;}return DefWindowProc(hwnd,uMsg,wParam,lParam);}