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#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) ; }