CreatDC()和CreateIC()

最新推荐文章于 2021-04-28 14:02:11 发布

转载最新推荐文章于 2021-04-28 14:02:11 发布 · 131 阅读

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原文链接：http://www.cnblogs.com/lzjsky/archive/2011/01/12/1933789.html

本文探讨了CreateIC和CreateDC两个Windows API函数的区别。CreateDC不仅用于获取设备信息还能进行绘画操作，而CreateIC仅用于快速获取设备信息而不支持修改。通过示例代码展示了两者的使用场景。

CreateIC()和CreateDC()都获取设备描述表句柄，但用CreateDC()获取的能够进行绘画，而用CreateIC()获取的设备描述表，你却不能用它往设备上写东西，只能查询获取你所要的信息。测试代码如下：

#include <windows.h>

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,

PSTR szCmdLine, int iCmdShow)

{

static TCHAR szAppName[] = TEXT ("HelloWin") ;

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, // window class name

TEXT ("The Hello Program"), // window caption

WS_OVERLAPPEDWINDOW, // window style

CW_USEDEFAULT, // initial x position

CW_USEDEFAULT, // initial y position

CW_USEDEFAULT, // initial x size

CW_USEDEFAULT, // initial y size

NULL, // parent window handle

NULL, // window menu handle

hInstance, // program instance handle

NULL) ; // creation parameters

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 HDC hdcScreen ;

switch (message)

{

case WM_CREATE:

hdcScreen = CreateDC(TEXT("DISPLAY"), NULL, NULL, NULL);

//hdcScreen = CreateIC(TEXT("DISPLAY"), NULL, NULL, NULL);

return 0 ;

case WM_PAINT:

TextOut(hdcScreen, 50, 50, TEXT("xiexiufeng"), 11);

return 0 ;

case WM_DESTROY:

DeleteDC(hdcScreen);

PostQuitMessage (0) ;

return 0 ;

}

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

}

   可是，为什么要用CreateIC()呢，CreateDC()已经可以满足我们所有的需要呢！查了下msdn:
   The CreateIC function creates an information context for the specified device. The information context provides a fast way to get information about the device without creating a device context.
   从中可以看出CreateIC()函数要必CreateDC()快。至于为什么快，其原理说来起来容易。CreateDC()不仅要获取信息，还要使其能够被修改。而CreateIC()只需要其能获得信息就行了。但，真正理解其中的东西，还需要解读这两个函数的源码吧。(这好像看起来不现实)

转载于:https://www.cnblogs.com/lzjsky/archive/2011/01/12/1933789.html