06 Windows编程——设备句柄 和 WM_PAINT消息

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

 1 #include<Windows.h>
 2 
 3 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);
 4 
 5 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)
 6 {
 7     WNDCLASS WndClass;
 8     TCHAR* ClassName = TEXT("MyClass");
 9     HWND hwnd;
10     MSG msg;
11 
12     WndClass.cbClsExtra = 0;
13     WndClass.cbWndExtra = 0;
14     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
15     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
16     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
17     WndClass.hInstance = hInst;
18     WndClass.lpfnWndProc = WindProc;
19     WndClass.lpszClassName = ClassName;
20     WndClass.lpszMenuName = NULL;
21     WndClass.style = CS_VREDRAW | CS_HREDRAW;
22 
23     if (!RegisterClass(&WndClass))
24     {
25         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);
26         return 0;
27     }
28 
29     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, 0, 0, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);
30     if (hwnd == NULL)
31     {
32         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);
33         return 0;
34     }
35     ShowWindow(hwnd, nShow);
36     UpdateWindow(hwnd);
37 
38     while (GetMessage(&msg,NULL,0,0))
39     {
40         TranslateMessage(&msg);
41         DispatchMessage(&msg);
42     }
43 
44     return 0;
45 }
46 
47 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
48 {
49     HDC hdc;
50     PAINTSTRUCT pt;
51     TCHAR* str = TEXT("hello");
52     switch (message)
53     {
54         case WM_DESTROY:
55             PostQuitMessage(0);//发送WM_QUIT消息
56             return 0;
57         case WM_PAINT:
58             hdc = BeginPaint(hwnd, &pt);
59             TextOut(hdc, 0, 0, str, _tcslen(str));
60             EndPaint(hwnd, &pt);
61             return 0;
62         default:
63             break;
64     }
65 
66     return DefWindowProc(hwnd, message, wParam, lParam);
67 }

View Code

也可以这样

 1 #include<Windows.h>
 2 
 3 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);
 4 
 5 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)
 6 {
 7     WNDCLASS WndClass;
 8     TCHAR* ClassName = TEXT("MyClass");
 9     HWND hwnd;
10     MSG msg;
11 
12     WndClass.cbClsExtra = 0;
13     WndClass.cbWndExtra = 0;
14     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
15     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
16     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
17     WndClass.hInstance = hInst;
18     WndClass.lpfnWndProc = WindProc;
19     WndClass.lpszClassName = ClassName;
20     WndClass.lpszMenuName = NULL;
21     WndClass.style = CS_VREDRAW | CS_HREDRAW;
22 
23     if (!RegisterClass(&WndClass))
24     {
25         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);
26         return 0;
27     }
28 
29     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, 0, 0, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);
30     if (hwnd == NULL)
31     {
32         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);
33         return 0;
34     }
35     ShowWindow(hwnd, nShow);
36     UpdateWindow(hwnd);
37 
38     while (GetMessage(&msg,NULL,0,0))
39     {
40         TranslateMessage(&msg);
41         DispatchMessage(&msg);
42     }
43 
44     return 0;
45 }
46 
47 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
48 {
49     HDC hdc;
50     PAINTSTRUCT pt;
51     TCHAR* str = TEXT("hello");
52     switch (message)
53     {
54         case WM_DESTROY:
55             PostQuitMessage(0);//发送WM_QUIT消息
56             return 0;
57         case WM_PAINT:
58             /*hdc = BeginPaint(hwnd, &pt);
59             TextOut(hdc, 0, 0, str, _tcslen(str));
60             EndPaint(hwnd, &pt);*/
61             hdc = GetDC(hwnd);
62             TextOut(hdc, 0, 0, str, _tcslen(str));
63             ReleaseDC(hwnd, hdc);
64             ValidateRect(hwnd, NULL);
65             return 0;
66         default:
67             break;
68     }
69 
70     return DefWindowProc(hwnd, message, wParam, lParam);
71 }

View Code

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

 1 #include<Windows.h>
 2 
 3 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);
 4 
 5 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)
 6 {
 7     WNDCLASS WndClass;
 8     TCHAR* ClassName = TEXT("MyClass");
 9     HWND hwnd;
10     MSG msg;
11 
12     WndClass.cbClsExtra = 0;
13     WndClass.cbWndExtra = 0;
14     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
15     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
16     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
17     WndClass.hInstance = hInst;
18     WndClass.lpfnWndProc = WindProc;
19     WndClass.lpszClassName = ClassName;
20     WndClass.lpszMenuName = NULL;
21     WndClass.style = CS_VREDRAW | CS_HREDRAW;
22 
23     if (!RegisterClass(&WndClass))
24     {
25         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);
26         return 0;
27     }
28 
29     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, 0, 0, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);
30     if (hwnd == NULL)
31     {
32         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);
33         return 0;
34     }
35     ShowWindow(hwnd, nShow);
36     UpdateWindow(hwnd);
37 
38     while (GetMessage(&msg,NULL,0,0))
39     {
40         TranslateMessage(&msg);
41         DispatchMessage(&msg);
42     }
43 
44     return 0;
45 }
46 
47 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
48 {
49     HDC hdc;
50     PAINTSTRUCT pt;
51     TCHAR* str = TEXT("hello");
52     switch (message)
53     {
54         case WM_DESTROY:
55             PostQuitMessage(0);//发送WM_QUIT消息
56             return 0;
57         case WM_PAINT:
58             /* 第一种
59             hdc = BeginPaint(hwnd, &pt);
60             TextOut(hdc, 0, 0, str, _tcslen(str));
61             EndPaint(hwnd, &pt);
62             */
63 
64             /* 第二种
65             hdc = GetDC(hwnd);
66             TextOut(hdc, 0, 0, str, _tcslen(str));
67             ReleaseDC(hwnd, hdc);
68             ValidateRect(hwnd, NULL);
69             */
70 
71             hdc = GetWindowDC(hwnd);
72             TextOut(hdc, 100, 100, str, _tcslen(str));
73             ReleaseDC(hwnd, hdc);
74             ValidateRect(hwnd, NULL);
75             return 0;
76         default:
77             break;
78     }
79 
80     return DefWindowProc(hwnd, message, wParam, lParam);
81 }

View Code

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[16];//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

 1 #include<Windows.h>
 2 
 3 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);
 4 
 5 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)
 6 {
 7     WNDCLASS WndClass;
 8     TCHAR* ClassName = TEXT("MyClass");
 9     HWND hwnd;
10     MSG msg;
11 
12     WndClass.cbClsExtra = 0;
13     WndClass.cbWndExtra = 0;
14     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
15     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
16     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
17     WndClass.hInstance = hInst;
18     WndClass.lpfnWndProc = WindProc;
19     WndClass.lpszClassName = ClassName;
20     WndClass.lpszMenuName = NULL;
21     WndClass.style = CS_VREDRAW | CS_HREDRAW;
22 
23     if (!RegisterClass(&WndClass))
24     {
25         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);
26         return 0;
27     }
28 
29     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, 0, 0, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);
30     if (hwnd == NULL)
31     {
32         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);
33         return 0;
34     }
35     ShowWindow(hwnd, nShow);
36     UpdateWindow(hwnd);
37 
38     while (GetMessage(&msg,NULL,0,0))
39     {
40         TranslateMessage(&msg);
41         DispatchMessage(&msg);
42     }
43 
44     return 0;
45 }
46 
47 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
48 {
49     HDC hdc;
50     PAINTSTRUCT pt;
51     TCHAR* str = TEXT("hello");
52     TCHAR* str1 = TEXT("World");
53     switch (message)
54     {
55         case WM_DESTROY:
56             PostQuitMessage(0);//发送WM_QUIT消息
57             return 0;
58         case WM_PAINT:
59             hdc = BeginPaint(hwnd, &pt);
60             TextOut(hdc, 0, 0, str, _tcslen(str));
61             TextOut(hdc, 5, 10, str1, _tcslen(str1));
62             EndPaint(hwnd, &pt);
63             
64             /* 第二种
65             hdc = GetDC(hwnd);
66             TextOut(hdc, 0, 0, str, _tcslen(str));
67             ReleaseDC(hwnd, hdc);
68             ValidateRect(hwnd, NULL);
69             */
70 
71             /* 第三种
72             hdc = GetWindowDC(hwnd);
73             TextOut(hdc, 100, 100, str, _tcslen(str));
74             ReleaseDC(hwnd, hdc);
75             ValidateRect(hwnd, NULL);
76             */
77 
78             return 0;
79         default:
80             break;
81     }
82 
83     return DefWindowProc(hwnd, message, wParam, lParam);
84 }

View Code

输出结果

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

 1 #include<Windows.h>
 2 
 3 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);
 4 
 5 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)
 6 {
 7     WNDCLASS WndClass;
 8     TCHAR* ClassName = TEXT("MyClass");
 9     HWND hwnd;
10     MSG msg;
11 
12     WndClass.cbClsExtra = 0;
13     WndClass.cbWndExtra = 0;
14     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
15     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
16     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
17     WndClass.hInstance = hInst;
18     WndClass.lpfnWndProc = WindProc;
19     WndClass.lpszClassName = ClassName;
20     WndClass.lpszMenuName = NULL;
21     WndClass.style = CS_VREDRAW | CS_HREDRAW;
22 
23     if (!RegisterClass(&WndClass))
24     {
25         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);
26         return 0;
27     }
28 
29     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, 0, 0, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);
30     if (hwnd == NULL)
31     {
32         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);
33         return 0;
34     }
35     ShowWindow(hwnd, nShow);
36     UpdateWindow(hwnd);
37 
38     while (GetMessage(&msg,NULL,0,0))
39     {
40         TranslateMessage(&msg);
41         DispatchMessage(&msg);
42     }
43 
44     return 0;
45 }
46 
47 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
48 {
49     HDC hdc;
50     PAINTSTRUCT pt;
51     TEXTMETRIC ts;
52     TCHAR* str = TEXT("hello");
53     TCHAR* str1 = TEXT("World");
54     switch (message)
55     {
56         case WM_DESTROY:
57             PostQuitMessage(0);//发送WM_QUIT消息
58             return 0;
59         case WM_PAINT:
60             hdc = BeginPaint(hwnd, &pt);
61             TextOut(hdc, 0, 0, str, _tcslen(str));
62             GetTextMetrics(hdc, &ts);
63             TextOut(hdc, 0, ts.tmHeight, str1, _tcslen(str1));
64             EndPaint(hwnd, &pt);
65             
66             /* 第二种
67             hdc = GetDC(hwnd);
68             TextOut(hdc, 0, 0, str, _tcslen(str));
69             ReleaseDC(hwnd, hdc);
70             ValidateRect(hwnd, NULL);
71             */
72 
73             /* 第三种
74             hdc = GetWindowDC(hwnd);
75             TextOut(hdc, 100, 100, str, _tcslen(str));
76             ReleaseDC(hwnd, hdc);
77             ValidateRect(hwnd, NULL);
78             */
79 
80             return 0;
81         default:
82             break;
83     }
84 
85     return DefWindowProc(hwnd, message, wParam, lParam);
86 }

View Code

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.

改变hdc设备句柄中字体颜色

COLORREF SetTextColor( HDC hdc, COLORREF color );

 1 #include<Windows.h>
 2 
 3 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);
 4 
 5 int WinMain(HINSTANCE hInst, HINSTANCE tmp, LPSTR szCmd, int nShow)
 6 {
 7     WNDCLASS WndClass;
 8     TCHAR* ClassName = TEXT("MyClass");
 9     HWND hwnd;
10     MSG msg;
11 
12     WndClass.cbClsExtra = 0;
13     WndClass.cbWndExtra = 0;
14     WndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
15     WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
16     WndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
17     WndClass.hInstance = hInst;
18     WndClass.lpfnWndProc = WindProc;
19     WndClass.lpszClassName = ClassName;
20     WndClass.lpszMenuName = NULL;
21     WndClass.style = CS_VREDRAW | CS_HREDRAW;
22 
23     if (!RegisterClass(&WndClass))
24     {
25         MessageBox(NULL, TEXT("Gegister Class Fail!!"), TEXT("error"), MB_OK);
26         return 0;
27     }
28 
29     hwnd = CreateWindow(ClassName, TEXT("Hello"), WS_OVERLAPPEDWINDOW, 0, 0, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL);
30     if (hwnd == NULL)
31     {
32         MessageBox(NULL, TEXT("Create Window Fail!!"), TEXT("error"), MB_OK);
33         return 0;
34     }
35     ShowWindow(hwnd, nShow);
36     UpdateWindow(hwnd);
37 
38     while (GetMessage(&msg,NULL,0,0))
39     {
40         TranslateMessage(&msg);
41         DispatchMessage(&msg);
42     }
43 
44     return 0;
45 }
46 
47 LRESULT CALLBACK WindProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
48 {
49     HDC hdc;
50     PAINTSTRUCT pt;
51     TEXTMETRIC ts;
52     TCHAR* str = TEXT("hello");
53     TCHAR* str1 = TEXT("World");
54     switch (message)
55     {
56         case WM_DESTROY:
57             PostQuitMessage(0);//发送WM_QUIT消息
58             return 0;
59         case WM_PAINT:
60             hdc = BeginPaint(hwnd, &pt);
61             SetTextColor(hdc, RGB(0x0, 0xFF, 0));
62             TextOut(hdc, 0, 0, str, _tcslen(str));
63             GetTextMetrics(hdc, &ts);
64             TextOut(hdc, 0, ts.tmHeight, str1, _tcslen(str1));
65             EndPaint(hwnd, &pt);
66             
67             /* 第二种
68             hdc = GetDC(hwnd);
69             TextOut(hdc, 0, 0, str, _tcslen(str));
70             ReleaseDC(hwnd, hdc);
71             ValidateRect(hwnd, NULL);
72             */
73 
74             /* 第三种
75             hdc = GetWindowDC(hwnd);
76             TextOut(hdc, 100, 100, str, _tcslen(str));
77             ReleaseDC(hwnd, hdc);
78             ValidateRect(hwnd, NULL);
79             */
80 
81             return 0;
82         default:
83             break;
84     }
85 
86     return DefWindowProc(hwnd, message, wParam, lParam);
87 }

View Code

WM_PAINT消息的来源和处理方式

WM_PAINT系统根据用户动产生。

你自己认为，什么时候窗口应该重绘，那么此种情况下，Windows必发送WML_PAINT消息。
例如滚动条移动，窗口被覆盖区域重新显示灯
强制窗口重绘的函数：InvalidateRect和InvalidateRgn。

但也有例外：

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 )；

 

什么是客户区的有效区，什么是客户区的无效区

获取字体的高度