When we use BeginPaint and EndPaint and when to use GetDC() and ReleaseDC()?

BeginPaint()- EndPaint() and GetDC() - ReleaseDC() are functions used in pair. BeginPaint() starts painting for a window and EndPaint() ends the task. BeginPaint()- EndPaint() mainly used in WP_PAINT message handling. GetDC() - ReleaseDC() pair also used for start and end drawing for a device context. This pair function is used for drawing on device context. Function reference has been included in the next paragraph.

BeginPaint: The BeginPaint function prepares the specified window for painting and fills a PAINTSTRUCT structure with information about the painting.

HDC BeginPaint(
  HWND hwnd,  // handle to window
  LPPAINTSTRUCT lpPaint
              // pointer to structure for paint information
);
 

EndPaint: The EndPaint function marks the end of painting in the specified window. This function is required for each call to the BeginPaint function, but only after painting is complete.

BOOL EndPaint(
  HWND hWnd,  // handle to window
  CONST PAINTSTRUCT *lpPaint 
              // pointer to structure for paint data
);
 

GetDC: The GetDC function retrieves a handle to a display device context for the client area of a specified window or for the entire screen. You can use the returned handle in subsequent GDI functions to draw in the device context. The GetDCEx function is an extension to GetDC, which gives an application more control over how and whether clipping occurs in the client area.

HDC GetDC(
  HWND hWnd   // handle to a window
);
 

ReleaseDC: The ReleaseDC function releases a device context (DC), freeing it for use by other applications. The effect of the ReleaseDC function depends on the type of device context. It frees only common and window device contexts. It has no effect on class or private device contexts.

int ReleaseDC(
  HWND hWnd,  // handle to window
  HDC hDC     // handle to device context
);
 

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