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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11To use st-core.fscss with Svelte in compiled mode, write an FSCSS file that defines the chart and calls st-core mixins, compile it to CSS during your app’s build, import the generated stylesheet, and have Svelte set the chart’s CSS custom properties as data changes. The key constraint is that chart geometry is generated at compile time: decide the number of points—or a maximum point count—before compiling.
How compiled st-core and Svelte fit together
st-core.fscss is described by its project README as a CSS chart and dashboard component system built on FSCSS. Its chart shapes use clip-path: polygon(); CSS custom properties supply the values that determine the rendered chart. The project lists mixins for chart fills and lines, points and dots, grids and axes, design tokens, stat cards, and category bars.
In compiled mode, the FSCSS CLI expands the mixins into ordinary CSS before the app is delivered. Svelte does not compile the FSCSS: it supplies changing values at runtime through custom properties such as --st-p0, --st-p1, and so on. The generated CSS provides the chart shape; Svelte updates its data.
The project README says compiled mode avoids the FSCSS browser runtime and a chart-layer remote request. It estimates compiled st-core at roughly 0.5 KB and the runtime at roughly 10 KB minified; those are maintainer-published estimates, not independent measurements. See the project README for current project details.
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Plan the chart’s point count first
The polygon geometry is fixed when FSCSS is compiled. Adding another custom property in Svelte at runtime does not create another polygon stop, so match the chart’s compile-time data template to the input shape you intend to support.
- Known, fixed-length series: compile the chart for that exact number of points and provide that many values.
- Variable series with a known maximum: compile for the maximum; trim longer input to that limit and pad shorter input so it has the expected number of values.
For example, a chart compiled for six points needs six values when Svelte builds its style string. Decide how padding should be represented for your chart—such as a zero value—rather than assuming missing points will alter the generated shape.
Create the FSCSS entry file
The integration tutorial uses a file such as src/styles/st-core.fscss. It imports st-core mixins, calls @st-root(), defines a chart-data array, and applies the chart-points, fill, and line mixins. Its zero-filled array acts as a compile-time shape template; set its length to the point count selected for your chart.
The exact mixin signatures and import path depend on the package’s current version. Follow the syntax in the compiled-mode Svelte integration tutorial and the current project documentation rather than treating an example’s package syntax as universal.
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Compile FSCSS as part of the app build
The tutorial’s workflow installs FSCSS as a development dependency and runs its CLI to convert the .fscss entry file into a .css stylesheet. Add that compilation to the app’s build scripts—its example uses a prebuild step—so the generated CSS is refreshed during a normal build. The tutorial’s install example uses @latest, which can change; check the current package version and CLI syntax before adopting its command.
The essential build sequence is:
- Keep the FSCSS source file in the project, for example at
src/styles/st-core.fscss. - Run the FSCSS CLI against that source to generate a CSS file.
- Run the CSS compilation step before the Svelte app build, so the stylesheet exists and reflects the current source.
Use the CLI flags and output path supported by the version installed in your project; the integration tutorial is the source for its demonstrated command and script setup.
Import the generated CSS into Svelte
Import the compiled CSS from a root layout, the application stylesheet, or the chart component—wherever best fits the app’s stylesheet organization. Import the generated .css output, not the .fscss source. FSCSS compilation expands the mixins during the build; Svelte then handles runtime data changes through the properties consumed by that CSS.
Bind reactive Svelte data to chart properties
For each input value, construct a corresponding --st-pN property, then include those properties along with any chart height or accent color in the element’s inline style. When the series changes, update the style string and the browser repaints the chart using the already-compiled CSS.
Svelte 4
The tutorial’s Svelte 4 example uses export let for component props and a $: reactive statement to rebuild the style string when its dependencies change. Keep this syntax in a Svelte 4 component rather than mixing it with Svelte 5’s runes.
Svelte 5
The tutorial’s Svelte 5 example uses $props() to receive props and $derived() to derive the style string from the current data. Use the API that matches the Svelte major version in your project; consult the official Svelte documentation for current syntax and migration details.
The examples in the integration tutorial illustrate the pattern; they are not independently tested here. Whichever version you use, make sure the derived string produces a property for each compiled chart point, and handle length limits before generating it.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When to choose compiled mode
The integration tutorial contrasts build-time compilation with loading the FSCSS runtime for a quick static demo. For an application that already has a Svelte build pipeline, it recommends compiling the stylesheet as part of that pipeline. With compiled mode, the page uses generated CSS rather than depending on the FSCSS browser runtime; changing the chart geometry requires updating and rebuilding the FSCSS source. This is the tutorial’s recommendation, not an independently benchmarked performance comparison.
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