st-core.fscss Charts: Dynamic Updates in Modern Frameworks
st-core.fscss draws area, line, and spider/radar charts with pure CSS — clip-path: polygon() and custom properties, no SVG path builders, no canvas, no chart runtime on the critical path. That design has a practical consequence for apps: updating a chart is rewriting CSS variables . Reactive frameworks already do that well. You do not need a JS chart instance, a virtual DOM subtree for every…
Dynamic updates in modern web frameworks are possible without the need for additional JavaScript chart instances or complex virtual DOM structures. The st-core.fscss framework utilizes pure CSS to create area, line, and spider/radar charts, employing clip-path: polygon() and custom properties. This allows for smooth transitions when values stream in, as CSS variables can be rewritten dynamically to update the chart geometry.
No SVG path builders, canvas, or chart runtime are required on the critical path, providing better performance and a more efficient implementation.
The framework supports Svelte, React, Vue, and plain JavaScript applications. To implement dynamic updates, the framework requires FSCSS version 1.2.3 or higher and st-core@v2. Linear charts write inverted Y positions on the host using variables such as --st-p1, --st-p2, ..., --st-pN, while spider/radar charts use polar coordinates like --st-sx1, --st-sy1, ..., --st-sxN, --st-syN. Multi-series charts require one host per series to prevent variable collisions.
To achieve smooth transitions, CSS transitions can be applied to the chart fill, line, and dots, such as clip-path, top, and left properties. When new data points stream in, the browser can interpolate on the compositor, ensuring native 60fps performance without the need for a JS animation loop. Optional cubic-bezier transitions can also be applied for a more customized animation effect.
Helper functions for generating CSS variables are provided for linear and spider/radar charts. Linear chart variables can be generated from score data ranging from 0 to 100, while spider/radar chart variables can be created using scores and a specified radius percentage. These functions can be called whenever the data or props change in your application, updating the chart geometry without the need for a third-party chart library or extra JavaScript setup.
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