feat(Spinner): add --spinner-arc-fraction public var - #5845
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feat(Spinner): add --spinner-arc-fraction public var#5845HelloOjasMutreja wants to merge 1 commit into
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Modified ComponentsSpinner (@astryxdesign/core)
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The four existing public vars (diameter, stroke-width, color, track-color) all reach the ring's geometry or paint except one: how much of the circle the moving arc covers. That's the most visually distinctive property at a given size, and it looks explicitly permitted rather than excluded by the theming contract facebook#5771 is recording (ring geometry through the spinner target, no new target). Applies the exact precedent this component already sets for diameter: the CSS-side strokeDasharray composes the dash from the live var, and the inline attribute (the pre-stylesheet render) keeps using the compiled-in default, unchanged. A themed sweep applies once the stylesheet lands, the same way a themed diameter already does. Fixes facebook#5819.
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Fixes #5819.
What's missing
Spinnerexposes four public vars on thespinnertarget (--spinner-diameter,--spinner-stroke-width,--spinner-color,--spinner-track-color) so a theme can change size, stroke, and color. It cannot change how much of the circle the moving arc covers — that was a compiled-in constant (ARC_FRACTION = 0.375, a 135deg sweep).Why this was an issue and not immediately a PR
The catch the issue raised: the CSS side (
styles.arc.strokeDasharray) already composes its dash from acalc(), so making it themeable there is close to free. But there's also an inlinestrokeDasharraySVG attribute — the pre-stylesheet render, for SSR / no-JS — computed in JS, which can't read a CSS custom property. A themed sweep would draw the default 135deg in that frame and snap to the themed value once the stylesheet lands.Why this is safe: precedent already set
Checked how
--spinner-diameter(the var this issue explicitly compares itself to) already handles this exact split, since it's used in both places too:styles.arc,styles.circle.r, etc.): reads the live, themeableRESOLVED_DIAMETERvar.<circle r={diameter / 2}>presentation attributes, and the pre-CSSstrokeDasharray):const {diameter} = SIZES[size]— the hardcoded default, not the themed value.So a themed diameter already only takes visual effect once the stylesheet loads, and the pre-CSS frame already renders at the unthemed default. This isn't a new kind of box-vs-paint disagreement (the class of bug #5214 and #5484 dealt with) — it's applying the one this component already ships, to one more property.
Change
styles.arc.strokeDasharraynow composes the dash fromvar(--spinner-arc-fraction)(a live number multiplier) instead of the pre-multipliedARC_DASH/ARC_GAPconstants.--spinner-arc-fractiondeclares alongside--spinner-diameter/--spinner-stroke-widthinsizeStyles, same default (0.375) for every size, unregistered like the other three public vars (no length-arithmetic ambiguity to guard against — it's a pure multiplier, not summed with anything).strokeDasharrayattribute (the pre-stylesheet render) is untouched — stillARC_FRACTION, matching how the inline diameter attributes stay at their default too.Testing
npx vitest run packages/core/src/Spinner/Spinner.test.tsx— 48/48 pass, including a new test confirming a themedsize:xltarget scopes--spinner-arc-fractioncorrectly (mirroring the existing diameter/color scoping tests).@astryxdesign/coreand inspected the compileddist/astryx.cssdirectly: confirmed--spinner-arc-fraction:.375declares on the size-variant rule andstrokeDasharraycomposes fromvar(--spinner-arc-fraction)in the compiledcalc(), not just in source.Posted the precedent-based reasoning on the issue first; given how directly it settles the ambiguity the issue raised (and the reporter's own "happy to implement whichever"), opening this as the concrete proposal rather than waiting further — happy to adjust based on any maintainer feedback.