CGContextFillRect

CGContextFillRect is a function in the Core Graphics framework of Apple's operating systems, used for drawing and image manipulation. Its primary purpose is to fill a rectangular area within a graphics context with a specified color. The function takes two arguments: the graphics context and a rectangle. The graphics context is an abstract representation of a drawing surface, such as a view, a PDF document, or an image bitmap. The rectangle defines the boundaries of the area to be filled.

When CGContextFillRect is called, the system draws the specified rectangle and fills its interior with the current fill color set in the graphics context. The fill color can be set using other Core Graphics functions, such as CGContextSetFillColorWithColor. The rectangle itself is defined by a CGRect structure, which contains the origin (x, y coordinates of the top-left corner) and the size (width and height) of the rectangle.

This function is fundamental for many drawing operations. For instance, it can be used to clear a view by filling it with a background color, to draw solid colored shapes, or to create filled backgrounds for text or other elements. It's a low-level drawing primitive that provides direct control over the rendering process within a Core Graphics context. Developers commonly use it within their custom drawing code, often in conjunction with other Core Graphics functions for more complex graphics.