The example demonstrates how a D3.js v5 application sets up a full-window canvas rendering environment, showing a simple steel-blue rectangle drawn near the top-left corner. It first creates a chart container that fills the viewport, then appends a canvas element sized to match the container’s CSS dimensions. The code logs those computed width and height values to the console for debugging, then uses the Canvas 2D API to fill a fixed 200×200 pixel rectangle at offset (10,10). The visualization highlights basic canvas setup and coordinate drawing without any data binding or interaction.