windows程序在现实方式上属于图形方式，和文字方式的显示，有显著的不同。

什么是设备句柄，如何获取

使用统一的数据结构表示某一设备，这个结构就是设备句柄。

源码

 #include<Windows.h>

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)

 {

     WNDCLASS WndClass;

     TCHAR* ClassName = TEXT("MyClass");

     HWND hwnd;

     MSG msg;

     WndClass.cbClsExtra = ;

     WndClass.cbWndExtra = ;

     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + );

     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);

     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);

     WndClass.hInstance = hInst;

     WndClass.lpfnWndProc = WindProc;

     WndClass.lpszClassName = ClassName;

     WndClass.lpszMenuName = NULL;

     WndClass.style = CS_VREDRAW | CS_HREDRAW;

     if (!RegisterClass(&WndClass))

     {

         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, , , CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);

     if (hwnd == NULL)

     {

         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     ShowWindow(hwnd, nShow);

     UpdateWindow(hwnd);

     while (GetMessage(&msg,NULL,,))

     {

         TranslateMessage(&msg);

         DispatchMessage(&msg);

     }

     return ;

 }

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

 {

     HDC hdc;

     PAINTSTRUCT pt;

     TCHAR* str = TEXT("hello");

     switch (message)

     {

         case WM_DESTROY:

             PostQuitMessage();//发送WM_QUIT消息

             return ;

         case WM_PAINT:

             hdc = BeginPaint(hwnd, &pt);

             TextOut(hdc, , , str, _tcslen(str));

             EndPaint(hwnd, &pt);

             return ;

         default:

             break;

     }

     return DefWindowProc(hwnd, message, wParam, lParam);

 }

对WM_PAINT消息的处理几乎总是从调用BeginPaint函数开始：hdc = BeginPaint(hwnd, &pt)

而以调用EndPaint函数结束：EndPaint(hwnd, &pt);

在这两个函数调用中，第一个参数均为程序的窗口句柄，而第二个参数均为指向一个类型为PAINTSTRUCT结构的指针。PAINTSTRUCT结构包含一些窗口过程用来对客户区进行绘制的信息。

BeginPaint 调用将使整个客户区有效，并返回一个“设备环境句柄”。

如何知道客户区呢？

该函数的第一个参数是程序的窗口句柄。第二个参数为指向类型为RECT的矩形结构的指针。该结构具有4个类型为LONG的字段，名称分别为left、top、right 和botom。GetclientRect函数将依据窗口尺寸来对这4个字段进行设置。其中，left和top字段总是会被赋为0，这样right和bottom字段就分别表示以像素为单位的客户区的宽度和高度。

BOOL GetClientRect(

    HWND hWnd, // 窗口句柄

    LPRECT lpRect // 客户区坐标

);

也可以这样

 #include<Windows.h>

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)

 {

     WNDCLASS WndClass;

     TCHAR* ClassName = TEXT("MyClass");

     HWND hwnd;

     MSG msg;

     WndClass.cbClsExtra = ;

     WndClass.cbWndExtra = ;

     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + );

     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);

     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);

     WndClass.hInstance = hInst;

     WndClass.lpfnWndProc = WindProc;

     WndClass.lpszClassName = ClassName;

     WndClass.lpszMenuName = NULL;

     WndClass.style = CS_VREDRAW | CS_HREDRAW;

     if (!RegisterClass(&WndClass))

     {

         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, , , CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);

     if (hwnd == NULL)

     {

         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     ShowWindow(hwnd, nShow);

     UpdateWindow(hwnd);

     while (GetMessage(&msg,NULL,,))

     {

         TranslateMessage(&msg);

         DispatchMessage(&msg);

     }

     return ;

 }

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

 {

     HDC hdc;

     PAINTSTRUCT pt;

     TCHAR* str = TEXT("hello");

     switch (message)

     {

         case WM_DESTROY:

             PostQuitMessage();//发送WM_QUIT消息

             return ;

         case WM_PAINT:

             /*hdc = BeginPaint(hwnd, &pt);

             TextOut(hdc, 0, 0, str, _tcslen(str));

             EndPaint(hwnd, &pt);*/

             hdc = GetDC(hwnd);

             TextOut(hdc, , , str, _tcslen(str));

             ReleaseDC(hwnd, hdc);

             ValidateRect(hwnd, NULL);

             return ;

         default:

             break;

     }

     return DefWindowProc(hwnd, message, wParam, lParam);

 }

使用EndPaint，直接就会使pt指向的区域变成有效区域。而ReleaseDC不会，WM_PAINT会一直存在，需要手动调用函数ValidateRect释放无效区。使无效客户区有效。

第三种做法

 #include<Windows.h>

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)

 {

     WNDCLASS WndClass;

     TCHAR* ClassName = TEXT("MyClass");

     HWND hwnd;

     MSG msg;

     WndClass.cbClsExtra = ;

     WndClass.cbWndExtra = ;

     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + );

     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);

     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);

     WndClass.hInstance = hInst;

     WndClass.lpfnWndProc = WindProc;

     WndClass.lpszClassName = ClassName;

     WndClass.lpszMenuName = NULL;

     WndClass.style = CS_VREDRAW | CS_HREDRAW;

     if (!RegisterClass(&WndClass))

     {

         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, , , CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);

     if (hwnd == NULL)

     {

         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     ShowWindow(hwnd, nShow);

     UpdateWindow(hwnd);

     while (GetMessage(&msg,NULL,,))

     {

         TranslateMessage(&msg);

         DispatchMessage(&msg);

     }

     return ;

 }

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

 {

     HDC hdc;

     PAINTSTRUCT pt;

     TCHAR* str = TEXT("hello");

     switch (message)

     {

         case WM_DESTROY:

             PostQuitMessage();//发送WM_QUIT消息

             return ;

         case WM_PAINT:

             /* 第一种

             hdc = BeginPaint(hwnd, &pt);

             TextOut(hdc, 0, 0, str, _tcslen(str));

             EndPaint(hwnd, &pt);

             */

             /* 第二种

             hdc = GetDC(hwnd);

             TextOut(hdc, 0, 0, str, _tcslen(str));

             ReleaseDC(hwnd, hdc);

             ValidateRect(hwnd, NULL);

             */

             hdc = GetWindowDC(hwnd);

             TextOut(hdc, , , str, _tcslen(str));

             ReleaseDC(hwnd, hdc);

             ValidateRect(hwnd, NULL);

             return ;

         default:

             break;

     }

     return DefWindowProc(hwnd, message, wParam, lParam);

 }

GetWindowDC、ReleaseDC操作窗口句柄，在绘制时不是以有效区作为参考，而是以整个窗口做参考，所以需要在TextOut里面调整输出文字的位置

代码里TextOut只在pt这个无效区显示输出文字。

HDC BeginPaint( HWND hWnd, LPPAINTSTRUCT lpPaint );

hWnd：窗口句柄

lpPaint：包含了用来重画客户区的程序信息
typedef struct tagPAINTSTRUCT {

HDC hdc;             //用来在客户去画图的设备表

BOOL fErase;      //客户背景区是否需要重绘（stru=是）

RECT rcPaint;     //无效客户区

BOOL fRestore;   //保留

BOOL fIncUpdate;//保留

BYTE rgbReserved[];//保留

} PAINTSTRUCT;

前面3段代码主要围绕设备句柄处理WM_PAINT消息。

如果使用TextOut在输出一段文字，调整不好位置的话容易遮挡之前输出的文字。代码如下

 #include<Windows.h>

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)

 {

     WNDCLASS WndClass;

     TCHAR* ClassName = TEXT("MyClass");

     HWND hwnd;

     MSG msg;

     WndClass.cbClsExtra = ;

     WndClass.cbWndExtra = ;

     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + );

     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);

     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);

     WndClass.hInstance = hInst;

     WndClass.lpfnWndProc = WindProc;

     WndClass.lpszClassName = ClassName;

     WndClass.lpszMenuName = NULL;

     WndClass.style = CS_VREDRAW | CS_HREDRAW;

     if (!RegisterClass(&WndClass))

     {

         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, , , CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);

     if (hwnd == NULL)

     {

         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     ShowWindow(hwnd, nShow);

     UpdateWindow(hwnd);

     while (GetMessage(&msg,NULL,,))

     {

         TranslateMessage(&msg);

         DispatchMessage(&msg);

     }

     return ;

 }

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

 {

     HDC hdc;

     PAINTSTRUCT pt;

     TCHAR* str = TEXT("hello");

     TCHAR* str1 = TEXT("World");

     switch (message)

     {

         case WM_DESTROY:

             PostQuitMessage();//发送WM_QUIT消息

             return ;

         case WM_PAINT:

             hdc = BeginPaint(hwnd, &pt);

             TextOut(hdc, , , str, _tcslen(str));

             TextOut(hdc, , , str1, _tcslen(str1));

             EndPaint(hwnd, &pt);

             /* 第二种

             hdc = GetDC(hwnd);

             TextOut(hdc, 0, 0, str, _tcslen(str));

             ReleaseDC(hwnd, hdc);

             ValidateRect(hwnd, NULL);

             */

             /* 第三种

             hdc = GetWindowDC(hwnd);

             TextOut(hdc, 100, 100, str, _tcslen(str));

             ReleaseDC(hwnd, hdc);

             ValidateRect(hwnd, NULL);

             */

             return ;

         default:

             break;

     }

     return DefWindowProc(hwnd, message, wParam, lParam);

 }

输出结果

获得字体高度的函数：BOOL GetTextMetrics( HDC hdc, LPTEXTMETRIC lptm );

 #include<Windows.h>

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)

 {

     WNDCLASS WndClass;

     TCHAR* ClassName = TEXT("MyClass");

     HWND hwnd;

     MSG msg;

     WndClass.cbClsExtra = ;

     WndClass.cbWndExtra = ;

     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + );

     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);

     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);

     WndClass.hInstance = hInst;

     WndClass.lpfnWndProc = WindProc;

     WndClass.lpszClassName = ClassName;

     WndClass.lpszMenuName = NULL;

     WndClass.style = CS_VREDRAW | CS_HREDRAW;

     if (!RegisterClass(&WndClass))

     {

         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, , , CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);

     if (hwnd == NULL)

     {

         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     ShowWindow(hwnd, nShow);

     UpdateWindow(hwnd);

     while (GetMessage(&msg,NULL,,))

     {

         TranslateMessage(&msg);

         DispatchMessage(&msg);

     }

     return ;

 }

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

 {

     HDC hdc;

     PAINTSTRUCT pt;

     TEXTMETRIC ts;

     TCHAR* str = TEXT("hello");

     TCHAR* str1 = TEXT("World");

     switch (message)

     {

         case WM_DESTROY:

             PostQuitMessage();//发送WM_QUIT消息

             return ;

         case WM_PAINT:

             hdc = BeginPaint(hwnd, &pt);

             TextOut(hdc, , , str, _tcslen(str));

             GetTextMetrics(hdc, &ts);

             TextOut(hdc, , ts.tmHeight, str1, _tcslen(str1));

             EndPaint(hwnd, &pt);

             /* 第二种

             hdc = GetDC(hwnd);

             TextOut(hdc, 0, 0, str, _tcslen(str));

             ReleaseDC(hwnd, hdc);

             ValidateRect(hwnd, NULL);

             */

             /* 第三种

             hdc = GetWindowDC(hwnd);

             TextOut(hdc, 100, 100, str, _tcslen(str));

             ReleaseDC(hwnd, hdc);

             ValidateRect(hwnd, NULL);

             */

             return ;

         default:

             break;

     }

     return DefWindowProc(hwnd, message, wParam, lParam);

 }

前面讲到3中获取hdc的方式，第一种 BeginPaint  &  EndPaint，在EndPaint之后，原来的无效区就成为有效区，不在发送WM_PAINT重绘

而第二三种方法，在ReleaseDC后，并不能使原来的无效区成为有效区，一直是无效区。需要使用ValidateRect(hwnd, NULL);来使原来的无效区变成有效区，但是这种方法效率太低，是整个窗口的重回。可以先获取窗口无效区，在针对这个无效区进行重绘

BOOL ValidateRect(

    HWND hWnd,          // 窗口的句柄

    CONST RECT *lpRect  // 指向RECT结构的指针

);

也就是代码顺序

GetUpdateRect

ValidateRect    //让某一个矩形区域变得有效

如果只用第一种方法，就不必写上面2个函数了。

获取窗口无效区域： BOOL GetUpdateRect( HWND hWnd, LPRECT lpRect, BOOL bErase );

bErase ：如果不想擦除背景，这个值就为false.

BOOL GetUpdateRect(

      HWND   hWnd,

      LPRECT lpRect,

      BOOL   bErase

);

改变hdc设备句柄中字体颜色

COLORREF SetTextColor( HDC hdc, COLORREF color );

 #include<Windows.h>

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)

 {

     WNDCLASS WndClass;

     TCHAR* ClassName = TEXT("MyClass");

     HWND hwnd;

     MSG msg;

     WndClass.cbClsExtra = ;

     WndClass.cbWndExtra = ;

     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + );

     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);

     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);

     WndClass.hInstance = hInst;

     WndClass.lpfnWndProc = WindProc;

     WndClass.lpszClassName = ClassName;

     WndClass.lpszMenuName = NULL;

     WndClass.style = CS_VREDRAW | CS_HREDRAW;

     if (!RegisterClass(&WndClass))

     {

         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, , , CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);

     if (hwnd == NULL)

     {

         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     ShowWindow(hwnd, nShow);

     UpdateWindow(hwnd);

     while (GetMessage(&msg,NULL,,))

     {

         TranslateMessage(&msg);

         DispatchMessage(&msg);

     }

     return ;

 }

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

 {

     HDC hdc;

     PAINTSTRUCT pt;

     TEXTMETRIC ts;

     TCHAR* str = TEXT("hello");

     TCHAR* str1 = TEXT("World");

     switch (message)

     {

         case WM_DESTROY:

             PostQuitMessage();//发送WM_QUIT消息

             return ;

         case WM_PAINT:

             hdc = BeginPaint(hwnd, &pt);

             SetTextColor(hdc, RGB(0x0, 0xFF, ));

             TextOut(hdc, , , str, _tcslen(str));

             GetTextMetrics(hdc, &ts);

             TextOut(hdc, , ts.tmHeight, str1, _tcslen(str1));

             EndPaint(hwnd, &pt);

             /* 第二种

             hdc = GetDC(hwnd);

             TextOut(hdc, 0, 0, str, _tcslen(str));

             ReleaseDC(hwnd, hdc);

             ValidateRect(hwnd, NULL);

             */

             /* 第三种

             hdc = GetWindowDC(hwnd);

             TextOut(hdc, 100, 100, str, _tcslen(str));

             ReleaseDC(hwnd, hdc);

             ValidateRect(hwnd, NULL);

             */

             return ;

         default:

             break;

     }

     return DefWindowProc(hwnd, message, wParam, lParam);

 }

可以在Win10上选好颜色，然后初始化RGB

桌面->右键->个性化->颜色->自定义颜色

创建画刷函数

HBRUSH CreateSolidBrush( COLORREF color );

 #include<Windows.h>

 #include<tchar.h>

 #define NUM 1000

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)

 {

     WNDCLASS WndClass;

     TCHAR* ClassName = TEXT("MyClass");

     HWND hwnd;

     MSG msg;

     HBRUSH hBrush;

     hBrush = CreateSolidBrush(RGB(0xFF, , ));

     WndClass.cbClsExtra = ;

     WndClass.cbWndExtra = ;

     WndClass.hbrBackground = hBrush;

     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);

     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);

     WndClass.hInstance = hInst;

     WndClass.lpfnWndProc = WindProc;

     WndClass.lpszClassName = ClassName;

     WndClass.lpszMenuName = NULL;

     WndClass.style = CS_VREDRAW | CS_HREDRAW;

     if (!RegisterClass(&WndClass))

     {

         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, , , , , NULL, NULL, hInst, NULL);

     if (hwnd == NULL)

     {

         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     ShowWindow(hwnd, nShow);

     UpdateWindow(hwnd);

     while (GetMessage(&msg, NULL, , ))

     {

         TranslateMessage(&msg);

         DispatchMessage(&msg);

     }

     return ;

 }

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

 {

     HDC hdc;

     PAINTSTRUCT pt;

     TEXTMETRIC ts;

     TCHAR* str = TEXT("hello");

     TCHAR* str1 = TEXT("World");

     switch (message)

     {

     case WM_DESTROY:

         PostQuitMessage();//发送WM_QUIT消息

         return ;

     case WM_PAINT:

         hdc = BeginPaint(hwnd, &pt);

         SetTextColor(hdc, RGB(0x0, 0xFF, ));

         TextOut(hdc, , , str, _tcslen(str));

         GetTextMetrics(hdc, &ts);

         TextOut(hdc, , ts.tmHeight, str1, _tcslen(str1));

         EndPaint(hwnd, &pt);

         /* 第二种

         hdc = GetDC(hwnd);

         TextOut(hdc, 0, 0, str, _tcslen(str));

         ReleaseDC(hwnd, hdc);

         ValidateRect(hwnd, NULL);

         */

         /* 第三种

         hdc = GetWindowDC(hwnd);

         TextOut(hdc, 100, 100, str, _tcslen(str));

         ReleaseDC(hwnd, hdc);

         ValidateRect(hwnd, NULL);

         */

         return ;

     default:

         break;

     }

     return DefWindowProc(hwnd, message, wParam, lParam);

 }

改变字体大小

 #include<Windows.h>

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)

 {

     WNDCLASS WndClass;

     TCHAR* ClassName = TEXT("MyClass");

     HWND hwnd;

     MSG msg;

     WndClass.cbClsExtra = ;

     WndClass.cbWndExtra = ;

     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + );

     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);

     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);

     WndClass.hInstance = hInst;

     WndClass.lpfnWndProc = WindProc;

     WndClass.lpszClassName = ClassName;

     WndClass.lpszMenuName = NULL;

     WndClass.style = CS_VREDRAW | CS_HREDRAW;

     if (!RegisterClass(&WndClass))

     {

         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, , , CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);

     if (hwnd == NULL)

     {

         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);

         return ;

     }

     ShowWindow(hwnd, nShow);

     UpdateWindow(hwnd);

     while (GetMessage(&msg, NULL, , ))

     {

         TranslateMessage(&msg);

         DispatchMessage(&msg);

     }

     return ;

 }

 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

 {

     TEXTMETRIC ts;

     TCHAR* str1 = TEXT("World");

     HDC hdc;

     PAINTSTRUCT pt;

     TCHAR* str = TEXT("hello");

     HFONT hFont;

     hFont = CreateFont(, , , , , , , , , , , , , NULL);

     switch (message)

     {

     case WM_DESTROY:

         PostQuitMessage();//发送WM_QUIT消息

         return ;

     case WM_PAINT:

         hdc = BeginPaint(hwnd, &pt);

         SelectObject(hdc, hFont);

         SetTextColor(hdc, RGB(0x0, 0xFF, ));

         TextOut(hdc, , , str, _tcslen(str));

         GetTextMetrics(hdc, &ts);

         TextOut(hdc, , ts.tmHeight, str1, _tcslen(str1));

         EndPaint(hwnd, &pt);

         /* 第二种

         hdc = GetDC(hwnd);

         TextOut(hdc, 0, 0, str, _tcslen(str));

         ReleaseDC(hwnd, hdc);

         ValidateRect(hwnd, NULL);

         */

         /* 第三种

         hdc = GetWindowDC(hwnd);

         TextOut(hdc, 100, 100, str, _tcslen(str));

         ReleaseDC(hwnd, hdc);

         ValidateRect(hwnd, NULL);

         */

         return ;

     default:

         break;

     }

     return DefWindowProc(hwnd, message, wParam, lParam);

 }

WM_PAINT消息的来源和处理方式

客户区：客户区是一块应用程序可以自由绘图并向用户传达可视输出的区域。

WM_PAINT何时产生？

当窗口的客户区的部分或全部“无效”且必须“更新”时，应用程序将得到此通知。这也就意味着窗口必须被“重绘”。

何种情况下客户区会变为无效？

①当窗口被首次创建时，整个客户区都是无效的，因为此时应用程序尚未在该窗口上绘制任何东西。第一条WM_PAINT消息（通常在应用程序调用WinMain中的UpdateWindow时出现）将指示窗口过程在窗口客户区进行绘制。
②在调整窗口的尺寸时，客户区也会变为无效。你可能还记得在前面的程序中，我们将窗口类结构的style字段设为了标记CS_HREDRAW和CSVREDRAW。这就指示Windows当窗口尺寸发生变化时，整个窗口都应宣布无效。在此之后，窗口过程将接收到一条WM_PAINT消息。
③如果先最小化窗口，然后再将窗口恢复到原先的尺寸，Windows并不会保存客户区的内容。在图形环境中，这种情况下需要保存的数据太多了。对此，Windows采取的策略是宣布窗口无效。窗口过程接收到WM_PAINT消息后，会自行恢复窗口的内容。
④在屏幕中拖动窗口导致窗口之间发生重叠时，Windows并不负责保存被另一个窗口覆盖的区域。当被覆盖的区域在后来不再被遮挡时，窗口被标记为无效。窗口过程会收到一条WM_PAINT消息，并对窗口的内容进行重绘。

例外情况？

鼠标滑过窗口，此时不发送WM_PAINT消息。这个重绘，由系统完成。

强制窗口重绘的函数：InvalidateRect和InvalidateRgn。

强制制定某一区域无效，需要重绘

BOOL InvalidateRect(HWND hWnd, CONST RECT *lpRect, BOOL bErase);

hWnd：想让哪个窗口的客户区无效

lpRect：客户无效区域

bErase：窗口背景是否需要重新绘制，如果是TRUE，那么窗口背景被擦去，需要重新绘制。

BOOL InvalidateRgn( HWND hWnd, HRGN hRgn, BOOL bErase );

hWnd：想让哪个窗口的客户区无效

hRgn：客户无效区域

bErase：窗口背景是否需要重新绘制，如果是TRUE，那么窗口背景被擦去，需要重新绘制。

HRGN和RECT之间的相互转换：CreateRectRgnIndirect

HRGN CreateRectRgnIndirect( CONST RECT *lprect )；

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