In MFC (Microsoft Foundation Class), the **Device Context (DC)** is a crucial component for handling graphical operations. The DC is an interface to the drawing surface, whether it’s a window, printer, or other output devices like bitmaps or memory.
What is Device Context (DC)?
A device context represents a set of drawing attributes, such as the pen, brush, and font, that can be used to render graphics or text. It serves as the link between the application and the output device.
Types of Device Contexts
– **Display Device Context**: Used for rendering on the screen.
– **Printer Device Context**: Used for sending output to a printer.
– **Memory Device Context**: Used for rendering in memory (bitmaps).
How to Get a Device Context in MFC
In MFC, you can obtain the device context of a window by calling `GetDC()` or using the `CDC` class. Example:
“`cpp
CDC* pDC = GetDC();
pDC->TextOut(10, 10, _T(“Hello, Device Context!”));
ReleaseDC(pDC);
“`
Basic Drawing with Device Context
You can use the `CDC` object to perform basic drawing operations such as drawing lines, rectangles, and text:
“`cpp
void CMyView::OnDraw(CDC* pDC)
{
pDC->MoveTo(0, 0);
pDC->LineTo(100, 100); // Draw a line
pDC->TextOut(50, 50, _T(“Drawing with DC”));
}
“`
Memory Device Context (Offscreen Drawing)
A memory DC allows offscreen rendering to a bitmap:
“`cpp
CDC memDC;
CBitmap bitmap;
memDC.CreateCompatibleDC(pDC);
bitmap.CreateCompatibleBitmap(pDC, width, height);
memDC.SelectObject(&bitmap);
memDC.FillSolidRect(0, 0, width, height, RGB(255, 255, 255)); // Fill background with white
“`
Release the Device Context
Always release the device context once you’re done with it:
“`cpp
ReleaseDC(pDC);
“`
Device contexts provide the necessary tools for rendering graphics in MFC applications.