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);
}