/** * @module taffy-preview * @description Preview visualizer for Taffy Layout structures. * Intercepts Taffy tree operations to collect layout data and renders * a visual representation of the nodes. */ const colorPalette = [ "#60a5fa", "#34d399", "#fbbf24", "#f472b6", "#c084fc", "#f97316", ]; interface PreviewLayout { width: number; height: number; x: number; y: number; } interface PreviewTree { getLayout(node: unknown): PreviewLayout; __previewChildren: Map; } function getChildrenMap(tree: PreviewTree) { if (!tree.__previewChildren) tree.__previewChildren = new Map(); return tree.__previewChildren; } function wrapTree(mod: { TaffyTree: { prototype: Record }; __previewWrapped?: boolean; }) { if (!mod?.TaffyTree || mod.__previewWrapped) return; const proto = mod.TaffyTree.prototype as { newLeaf: unknown; newWithChildren: unknown; addChild: unknown; }; const originalNewLeaf = proto.newLeaf as (style: unknown) => unknown; const originalNewWithChildren = proto.newWithChildren as ( style: unknown, children: unknown[], ) => unknown; const originalAddChild = proto.addChild as ( parent: unknown, child: unknown, ) => unknown; proto.newLeaf = function (style: unknown) { const node = originalNewLeaf.call(this, style); getChildrenMap(this as unknown as PreviewTree).set(node, []); return node; }; proto.newWithChildren = function (style: unknown, children: unknown[] = []) { const node = originalNewWithChildren.call(this, style, children); getChildrenMap(this as unknown as PreviewTree).set(node, children); return node; }; if (typeof originalAddChild === "function") { proto.addChild = function (parent: unknown, child: unknown) { const result = originalAddChild.call(this, parent, child); const map = getChildrenMap(this as unknown as PreviewTree); const list = map.get(parent) || []; if (!list.includes(child)) list.push(child); map.set(parent, list); if (!map.has(child)) map.set(child, []); return result; }; } mod.__previewWrapped = true; } function collectNodesWithPositions(tree: PreviewTree, root: unknown) { const map = getChildrenMap(tree); const visited = new Set(); const result: { node: unknown; layout: PreviewLayout; x: number; y: number; isLeaf: boolean; }[] = []; const walk = (node: unknown, offsetX: number, offsetY: number) => { if (!node || visited.has(node)) return; visited.add(node); const layout = tree.getLayout(node); const x = (layout?.x ?? 0) + offsetX; const y = (layout?.y ?? 0) + offsetY; const children = map.get(node) || []; result.push({ node, layout, x, y, isLeaf: children.length === 0 }); children.forEach((child: unknown) => walk(child, x, y)); }; walk(root, 0, 0); return result; } /** * Visualizes a Taffy Layout tree. * * Renders a set of nested boxes representing the layout nodes, * displaying their dimensions and positions. * * @param props.tree - The preview-wrapped Taffy tree interface. * @param props.root - The root node of the layout to visualize. * @returns A React component rendering the layout visualization. */ export function TaffyTreePreview({ tree, root, }: { tree: PreviewTree; root: unknown; }) { if (!tree || !root || typeof tree.getLayout !== "function") { return

No layout data.

; } const nodes = collectNodesWithPositions(tree, root); const rootLayout = tree.getLayout(root); const width = rootLayout?.width ?? 0; const height = rootLayout?.height ?? 0; return (

{nodes.map(({ layout, x, y, isLeaf }, index) => { const color = index === 0 ? "var(--taffy-root-bg, rgba(255, 255, 255, 0.45))" : colorPalette[(index - 1) % colorPalette.length]; return (

{isLeaf && layout.width > 30 && layout.height > 15 ? ( {(layout.width % 1 === 0 ? layout.width : layout.width.toFixed(1)) + "×" + (layout.height % 1 === 0 ? layout.height : layout.height.toFixed(1))} ) : ( "" )}

); })}

); } /** * Registers the preview mechanism by wrapping the Taffy module. * * @param mod - The Taffy WASM module to instrument. */ export function registerPreview(mod: { TaffyTree: unknown; TaffyTreePreview?: unknown; }) { wrapTree( mod as { TaffyTree: { prototype: Record }; __previewWrapped?: boolean; }, ); if (mod) { mod.TaffyTreePreview = TaffyTreePreview; } if (typeof globalThis !== "undefined") { (globalThis as unknown as { TaffyTreePreview: unknown }).TaffyTreePreview = TaffyTreePreview; } }

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Next Steps