CGContextSetLineWidth

CGContextSetLineWidth is a function in the Core Graphics framework of Apple's operating systems that sets the width of the current line drawing operation. This function is part of the Quartz 2D drawing environment. When you draw lines, curves, or the outline of shapes using a Core Graphics context, the width specified by CGContextSetLineWidth determines how thick that stroke will be.

The function takes two arguments: a graphics port (CGContextRef) and a CGFloat value representing the line width. The line width is measured in coordinate system units. A value of 1.0 typically represents a single pixel on the screen or a point on a printed page. Setting a larger value will result in a thicker stroke, while a value of 0.0 or less will be treated as 1.0. It's important to note that the line width is applied centered on the path. This means half of the width will extend on either side of the geometric path.

This function is fundamental for controlling the visual appearance of stroked paths in applications built with macOS, iOS, watchOS, and tvOS. It is often used in conjunction with other Core Graphics drawing functions such as CGContextMoveToPoint, CGContextAddLineToPoint, CGContextStrokePath, and CGContextSetStrokeColorWithColor to achieve specific visual effects. Developers commonly use it to draw borders, dividers, or any other graphical element that requires a defined line thickness.