GetDC function

The GetDC function retrieves a handle to a device context (DC) for the client area of a specified window or for the entire screen.

Syntax

#include <windows.h>

HDC GetDC(
    HWND hWnd
);

Parameters

Parameter	Description
`hWnd`	Handle to the window whose DC is to be retrieved. If this parameter is `NULL`, `GetDC` returns the DC for the entire screen.

Return value

If the function succeeds, the return value is a handle to a device context for the specified window. If the function fails, the return value is NULL. To get extended error information, call GetLastError.

Remarks

The retrieved DC must be released by calling ReleaseDC when you are finished using it.
A GetDC call increments the DC's reference count. Each successful GetDC must be matched by a corresponding ReleaseDC.
Do not store the returned DC for longer than the scope of your operation; retrieve a fresh DC each time you need one.

Example

#include <windows.h>
#include <stdio.h>

int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrev, LPSTR lpCmd, int nShow)
{
    HWND hwnd = GetForegroundWindow(); // get the active window
    HDC hdc = GetDC(hwnd);
    if (!hdc) {
        MessageBox(NULL, L"Failed to get DC", L"Error", MB_ICONERROR);
        return 0;
    }

    // Draw a red rectangle in the client area
    HBRUSH hBrush = CreateSolidBrush(RGB(255,0,0));
    RECT rc;
    GetClientRect(hwnd, &rc);
    FillRect(hdc, &rc, hBrush);
    DeleteObject(hBrush);

    // Release the DC
    ReleaseDC(hwnd, hdc);
    return 0;
}