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Obtaining a Private Display Device Context

An application performing numerous drawing operations in the client area of its window must use a private display DC. To create this type of DC, the application must specify the CS_OWNDC constant for the style member of the WNDCLASS structure when registering the window class. After registering the window class, the application obtains a handle identifying a private display DC by calling the GetDC function.

The following example shows how to create a private display DC.



#include <windows.h>    // required for all Windows-based applications  
#include <stdio.h>      // C run-time header for i/o 
#include <string.h>     // C run-time header for strtok_s  
#include "dc.h"         // specific to this program  
 
// Function prototypes. 
 
BOOL InitApplication(HINSTANCE); 
long FAR PASCAL MainWndProc(HWND, UINT, UINT, LONG); 
 
// Global variables  
 
HINSTANCE hinst;       // handle to current instance  
HDC hdc;               // display device context handle  
 
BOOL InitApplication(HINSTANCE hinstance) 
{ 
    WNDCLASS  wc; 
 
    // Fill in the window class structure with parameters  
    // describing the main window.  
 
    wc.style = CS_OWNDC;         // Private-DC constant  
    wc.lpfnWndProc = (WNDPROC) MainWndProc; 
 
    wc.cbClsExtra = 0; 
    wc.cbWndExtra = 0; 
    wc.hInstance = hinstance; 
 
    wc.hIcon = LoadIcon((HINSTANCE) NULL, 
        MAKEINTRESOURCE(IDI_APPLICATION)); 
 
    wc.hCursor = LoadCursor((HINSTANCE) NULL, 
        MAKEINTRESOURCE(IDC_ARROW)); 
 
    wc.hbrBackground = GetStockObject(WHITE_BRUSH); 
    wc.lpszMenuName =  "GenericMenu"; 
    wc.lpszClassName = "GenericWClass"; 
 
    // Register the window class and return the resulting code.  
 
    return RegisterClass(&wc); 
} 
 
LRESULT APIENTRY MainWndProc( 
        HWND hwnd,           // window handle  
        UINT message,        // type of message  
        WPARAM wParam,       // additional information  
        LPARAM lParam)       // additional information  
{ 
 
    PAINTSTRUCT ps;              // paint structure  
 
    // Retrieve a handle identifying the private DC.  
 
    hdc = GetDC(hwnd); 
 
    switch (message) 
    { 
        case WM_PAINT: 
              hdc = BeginPaint(hwnd, &ps); 
 
        // Draw and paint using private DC. 
        
        	     EndPaint(hwnd, &ps);
              
        case WM_DESTROY:
		             PostQuitMessage(0);
		             break;
        default:
		        return DefWindowProc(hWnd, message, wParam, lParam);
	}
	return 0;
}


 

 

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