contentRects

The term contentRects refers to a collection of rectangles that define the layout of content within a given element on a web page. These rectangles are crucial for understanding how elements are rendered and interact with each other in the browser's rendering engine.

Each contentRect represents a distinct area of an element's layout. Typically, there are several such rectangles, including the border box, padding box, and content box. The border box encompasses the entire element, including its borders, padding, and content. The padding box includes the element's padding and content, but excludes the borders. The content box, as the name suggests, represents the actual space occupied by the element's content, such as text or images.

These rectangles are used by browsers for various purposes, such as calculating layout, handling user interactions like mouse events, and determining which parts of the page need to be repainted. For developers, understanding contentRects is essential for precise styling and layout control. For instance, when using CSS properties like `box-sizing`, developers can influence how these rectangles are calculated, affecting the overall dimensions of an element. Inspecting these rectangles using browser developer tools can help diagnose layout issues and optimize rendering performance.