GetDC

GetDC is a function in the Windows API that retrieves a handle to a device context (HDC) for drawing with the Graphics Device Interface (GDI). It is declared in Wingdi.h and implemented in Gdi32.dll.

If a window handle is provided (hWnd is non-NULL), GetDC returns a DC for the client area of that window. If hWnd is NULL, GetDC returns a DC for the entire screen. The returned HDC can be used with GDI drawing functions to render graphics, text, or other visuals.

The caller is responsible for releasing the device context by calling ReleaseDC with the same window handle and the HDC returned by GetDC. Failure to release the DC can exhaust system resources. In WM_PAINT processing, BeginPaint and EndPaint are typically preferred over GetDC for painting the client area, because they validate the update region and integrate with the system's paint cycle.

GetDC is suitable for immediate drawing outside of WM_PAINT, but its DC is not suitable for persistent off-screen rendering. For off-screen or memory rendering, developers commonly create a memory DC with CreateCompatibleDC, select into it, and then Blit the result to a window DC when ready. Related functions include GetWindowDC (which retrieves a DC for the entire window, including non-client areas) and GetDCEx (which allows additional clipping and flags), as well as ReleaseDC and CreateCompatibleDC.