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以下解读来自《Windows 程序设计》(第5版 珍藏版)P105~108
小甲鱼解读:内容比较简单,无需过多解读,看过了就懂了~
设备环境通常指的是物理的显示设备,如视频显示器或者打印机。经常需要获取这些设备的某些信息,包括显示器的大小(以像素或者物理尺寸的方式)和它的色彩能力。这些信息可以通过调用 GetDeviceCaps 函数来获取:
iValue = GetDeviceCaps(hdc, iIndex);
其中,参数 iIndex 是定义在 WINGDI.H 头文件中的 29 个标识符之一。
例如,当 iIndex 的值为 HORZRES 时,GetDeviceCaps 函数以像素为单位返回设备的宽度;使用 VERTRES 参数值会以像素为单位返回设备的高度。
如果 hdc 是一个屏幕设备环境的句柄,这里获取的信息和从 GetSystemMetrics 函数获取的信息是一样的。如果 hdc 是一个打印机设备环境,那么 GetDeviceCaps 将以像素为单位返回打印机显示区域的高度和宽度。
还可以使用 GetDeviceCaps 函数来确定设备处理各种类型图形的能力,通常这对于视频显示器并不重要,但是对于打印机却非常重要。例如,大多数的绘图仪不能绘制位图图像,通过调用 GetDeviceCaps 函数可以让你提前知道这一情况。
DEVCAPS1 程序
DEVCAPS1 程序显示了在使用视频显示器设备环境时,可从 GetDeviceCaps 函数得到的部分(并不是全部)信息。
代码如下所示:
- *---------------------------------------------------------
- DEVCAPS1.C -- Device Capabilities Display Program No. 1
- (c) Charles Petzold, 1998
- ---------------------------------------------------------*/
- #include <windows.h>
- #define NUMLINES ((int) (sizeof devcaps / sizeof devcaps [0]))
-
- struct
- {
- int iIndex ;
- TCHAR * szLabel ;
- TCHAR * szDesc ;
- }
- devcaps [] =
- {
- HORZSIZE, TEXT ("HORZSIZE"), TEXT ("Width in millimeters:"),
- VERTSIZE, TEXT ("VERTSIZE"), TEXT ("Height in millimeters:"),
- HORZRES, TEXT ("HORZRES"), TEXT ("Width in pixels:"),
- VERTRES, TEXT ("VERTRES"), TEXT ("Height in raster lines:"),
- BITSPIXEL, TEXT ("BITSPIXEL"), TEXT ("Color bits per pixel:"),
- PLANES, TEXT ("PLANES"), TEXT ("Number of color planes:"),
- NUMBRUSHES, TEXT ("NUMBRUSHES"), TEXT ("Number of device brushes:"),
- NUMPENS, TEXT ("NUMPENS"), TEXT ("Number of device pens:"),
- NUMMARKERS, TEXT ("NUMMARKERS"), TEXT ("Number of device markers:"),
- NUMFONTS, TEXT ("NUMFONTS"), TEXT ("Number of device fonts:"),
- NUMCOLORS, TEXT ("NUMCOLORS"), TEXT ("Number of device colors:"),
- PDEVICESIZE, TEXT ("PDEVICESIZE"), TEXT ("Size of device structure:"),
- ASPECTX, TEXT ("ASPECTX"), TEXT ("Relative width of pixel:"),
- ASPECTY, TEXT ("ASPECTY"), TEXT ("Relative height of pixel:"),
- ASPECTXY, TEXT ("ASPECTXY"), TEXT ("Relative diagonal of pixel:"),
- LOGPIXELSX, TEXT ("LOGPIXELSX"), TEXT ("Horizontal dots per inch:"),
- LOGPIXELSY, TEXT ("LOGPIXELSY"), TEXT ("Vertical dots per inch:"),
- SIZEPALETTE, TEXT ("SIZEPALETTE"), TEXT ("Number of palette entries:"),
- NUMRESERVED, TEXT ("NUMRESERVED"), TEXT ("Reserved palette entries:"),
- COLORRES, TEXT ("COLORRES"), TEXT ("Actual color resolution:")
- } ;
- LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
- int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
- PSTR szCmdLine, int iCmdShow)
- {
- static TCHAR szAppName[] = TEXT ("DevCaps1") ;
- HWND hwnd ;
- MSG msg ;
- WNDCLASS wndclass ;
-
- wndclass.style = CS_HREDRAW | CS_VREDRAW ;
- wndclass.lpfnWndProc = WndProc ;
- wndclass.cbClsExtra = 0 ;
- wndclass.cbWndExtra = 0 ;
- wndclass.hInstance = hInstance ;
- wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;
- wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;
- wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
- wndclass.lpszMenuName = NULL ;
- wndclass.lpszClassName = szAppName ;
-
- if (!RegisterClass (&wndclass))
- {
- MessageBox (NULL, TEXT ("This program requires Windows NT!"),
- szAppName, MB_ICONERROR) ;
- return 0 ;
- }
-
- hwnd = CreateWindow (szAppName, TEXT ("Device Capabilities"),
- WS_OVERLAPPEDWINDOW,
- CW_USEDEFAULT, CW_USEDEFAULT,
- CW_USEDEFAULT, CW_USEDEFAULT,
- NULL, NULL, hInstance, NULL) ;
-
- ShowWindow (hwnd, iCmdShow) ;
- UpdateWindow (hwnd) ;
-
- while (GetMessage (&msg, NULL, 0, 0))
- {
- TranslateMessage (&msg) ;
- DispatchMessage (&msg) ;
- }
- return msg.wParam ;
- }
- LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
- {
- static int cxChar, cxCaps, cyChar ;
- TCHAR szBuffer[10] ;
- HDC hdc ;
- int i ;
- PAINTSTRUCT ps ;
- TEXTMETRIC tm ;
-
- switch (message)
- {
- case WM_CREATE:
- hdc = GetDC (hwnd) ;
-
- GetTextMetrics (hdc, &tm) ;
- cxChar = tm.tmAveCharWidth ;
- cxCaps = (tm.tmPitchAndFamily & 1 ? 3 : 2) * cxChar / 2 ;
- cyChar = tm.tmHeight + tm.tmExternalLeading ;
-
- ReleaseDC (hwnd, hdc) ;
- return 0 ;
-
- case WM_PAINT:
- hdc = BeginPaint (hwnd, &ps) ;
-
- for (i = 0 ; i < NUMLINES ; i++)
- {
- TextOut (hdc, 0, cyChar * i,
- devcaps[i].szLabel,
- lstrlen (devcaps[i].szLabel)) ;
-
- TextOut (hdc, 14 * cxCaps, cyChar * i,
- devcaps[i].szDesc,
- lstrlen (devcaps[i].szDesc)) ;
-
- SetTextAlign (hdc, TA_RIGHT | TA_TOP) ;
-
- TextOut (hdc, 14 * cxCaps + 35 * cxChar, cyChar * i, szBuffer,
- wsprintf (szBuffer, TEXT ("%5d"),
- GetDeviceCaps (hdc, devcaps[i].iIndex))) ;
-
- SetTextAlign (hdc, TA_LEFT | TA_TOP) ;
- }
-
- EndPaint (hwnd, &ps) ;
- return 0 ;
-
- case WM_DESTROY:
- PostQuitMessage (0) ;
- return 0 ;
- }
- return DefWindowProc (hwnd, message, wParam, lParam) ;
- }
复制代码
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