A collection of pure helper functions for the graph canvas: normalizing JSON input with WeakMap memoization, composing CSS class and style objects with theme tokens, parsing JSON text into a discriminated result (ok/above-limit/error), building an edge target map for clickable edges, handling Shift+wheel horizontal panning, toggling a 'dragging' class for long-press support, and computing the graph's client rect via a multi-strategy measurement cascade (leaf union, bounding client rect, SVG screen CTM, layout fallback) with proportional padding. The `computeGraphClientRect` function is particularly well-engineered, handling real-world reaflow rendering quirks like framer-motion CSS transforms and curved edge bulges. Isolated, thoroughly tested, and could be extracted for any reaflow-based graph component.

Implements a React context for collapsible tree nodes. Provides `pathKey` (JSONPath to stable JSON string), `isPathCollapsed`, and `isNodeHidden` (prefix-matching against collapsed paths). The standout is `prunePaths`, which validates that each serialized collapsed path still resolves to an object or array in the current JSON after edits — automatically dropping stale references to primitives or missing keys. This prevents the collapse state from accumulating dead entries and keeps the rendered graph consistent. The pattern is generic and reusable for any hierarchical data collapse/expand system.

Transforms a JSON string into a flat list of nodes and edges suitable for reaflow's ELK layout. Uses jsonc-parser's `parseTree` and `getNodePath` to walk the AST without a full JSON parse, making it tolerant of syntax errors (returns partial graph plus errors). Handles all JSON value types, arrays of primitives (collapses into single parent node), nested objects, and empty containers. Each node carries metadata (path, parentKey, parentType) for downstream click and collapse interactions. The output is consistent even for deeply nested structures and edge cases like empty-string keys. Idempotent, testable, and could serve as a standalone JSON-to-graph converter.

Implements a secure handoff protocol to send the current document to ToDiagram.com via postMessage. Opens a popup with `?source=jsoncrack` query parameter, listens for a `handoff-ready` message (origin-validated), then sends the JSON content and format. Includes a 90-second timeout to handle cold loads of the target app, and returns `false` if the popup was blocked so the caller can fall back to a direct navigation. The origin validation and message structure pattern is clean and reusable for any cross-origin editor handoff.

Comprehensive unit tests for canvasHelpers covering toJsonText memoization (weakmap cache hit, different references), parseJsonGraph discriminated results (ok, above-limit, syntax errors), buildCanvasClassName (grid, custom class), buildCanvasStyle (theme tokens, overrides), buildEdgeTargetMap (empty, multiple edges), and getShiftWheelHorizontalPanDelta (key check, line/page delta scaling). Tests are well-structured, use vitest, and provide thorough coverage of edge cases, including the note that `kind: error` is intentionally untested because it's unreachable with current input. This test file demonstrates disciplined testing of pure utility functions.