Making Desktops Expressive: Introducing Bézier Curves to GTK

Linux desktop interfaces are typically built from rectangles and predefined transitions. While functional, these constraints make it difficult to create interfaces with the kind of expressive motion and fluid geometry commonly seen in modern design systems.

In this talk, I will demonstrate how I brought Bézier-driven animation and procedural shape generation to GTK3 using my open-source geometry library, expressive-shapes, along with a series of runtime modifications to GTK's animation pipeline.

The talk explores two complementary ideas:

1. Overriding Time: Bézier Transitions

   GTK widgets such as stacks and revealers rely on fixed interpolation models. I will begin with a quick overview of GTK's widget lifecycle (mapping, allocation, drawing, and frame clock updates) to establish where animations fit into the rendering pipeline. From there, I will show how native transition timelines can be intercepted and redirected through a custom animation manager synchronized with the display refresh cycle enabling smooth Bézier-based motion and expressive transitions.

2. Overriding Form: Geometry Engine

   Beyond animation, I wanted widgets themselves to become dynamic shapes rather than static rectangles. I will talk about the evolution of expressive-shapes into a geometry engine capable of generating rounded polygons and performing real-time shape morphing. Along the way, I will discuss the underlying algorithms, the architectural decisions that shaped the library.

Throughout the talk, I will present implementation examples and live demonstrations using PyGObject, showing how these techniques can be combined to create fluid animations, shape morphing, and visually expressive GTK3 interfaces.