We recently re-wrote our selection feature for tldraw, a digital whiteboard. To make it work, we first needed to teach our whiteboard to see the canvas without first rendering it, and then to capture the (surprisingly! extraordinarily!) complex logic behind a simple click.

Ever wondered how your scribbles on Snapchat turns into a smooth line, or how the pen tool works in Figma or Procreate? In this talk we'll dive into the invisible art of line-drawing algorithms.

We'll start from the historical pixel-based methods to the tools that we use today, wrapping up with real-world examples.

The techniques described are evergreen, timeless and cross-platform.

Love linking lines? Join Steve in considering the humble arrow as both a programming problem and a user experience challenge. In this talk, he'll present the many complex problems and solutions that he has encountered when working with arrows in his open source library perfect-arrows and later in tldraw (tldraw.com). With a narrow scope and plenty of animations to guide the way, we'll look at intersections, arrow heads, arrow head angles, and all of the different user interface issues behind authoring and adjusting arrows between shapes, other shapes, and points.