# Measure Measure is a temporary chart tool for checking rhumb-line range and true bearing across one or more legs. Measurements are advisory. They do not account for hazards, depth, traffic, leeway, current, restricted areas, or the vessel's maneuvering limits. ## Quick use 1. Open **Menu**, then **Measure**. The pointer becomes a crosshair, and the strip asks for a start point. 2. Tap the chart once to set the start, then tap again to make a leg. Continue tapping to add legs. 3. Read the latest leg and true bearing in the strip. The running total appears after the second leg. Individual distance labels appear on the chart at zoom 8 and above when MapLibre can place them without a collision. The final point keeps the total label. 4. Select a point by tapping its generous chart target or choosing it from **Selected point**. The strip shows its incoming and outgoing leg distances and true bearings. 5. Choose **Move point**, then drag the selected chart point or tap its new chart position. Choose **Delete point** to remove it. **Undo** reverses the latest add, completed move, or deletion. 6. Choose **Clear**, then confirm, to keep Measure active with a clean slate. Choose **Done** to end Measure and remove every temporary point. For a keyboard movement path, select the point in the strip, choose **Move point**, focus and pan the chart with MapLibre's keyboard controls, then choose **Move to chart center**. Press and hold or right-click a chart position before Measure is active, then choose **Measure from here** to start a fresh measurement at that exact position. Keyboard users can focus the chart and use the Context Menu key or Shift+F10 to open the same actions at the chart center. Selecting the already-active Measure menu item closes the menu without erasing current work. Escape cancels move mode first and preserves the measurement. A following Escape ends Measure when it is the topmost dismissible surface. Measure and route editing cannot own chart gestures at the same time. Route editing disables Measure with an explanation. Starting or editing a route while Measure is active is refused without clearing either tool. ## Geometry and units Each leg uses rhumb-line distance and rhumb bearing. The two values therefore describe the same constant-bearing geometry. Bearings are clockwise from true north and display as three digits with a `T` suffix. Values remain meters and radians in state. Range converts only at display time according to the Signal K server unit preference, using meters or feet at short range and nautical miles above the shared threshold. Longitude deltas use the short direction across the antimeridian. Overlay geometry splits at the date line into canonical east-edge and west-edge segments, so a two-degree leg does not draw a near-global line. Each distance label uses a Mercator-space rhumb midpoint with the longitude unwrapped in the short direction. An antimeridian label therefore remains beside the date line instead of appearing near Greenwich. Leg labels are distance-only to limit chart clutter. They begin at zoom 8, participate in MapLibre collision placement, avoid chart edges, and use theme paint for day, dusk, and night-red. Bearings remain in the selected-leg strip, where they are always available without covering chart detail. ## Editing, Undo, and limits Every point receives a stable, session-local id. Undo stores inverse operations: - Undo after adding removes that point. - Undo after moving restores the prior coordinate. - Undo after deleting reinserts the same point at the same index. One completed drag creates one Undo entry. A canceled or zero-distance drag creates none. Starting fresh, stopping, and clearing reset the history and selection. Clear requires confirmation because it cannot be undone. Only finite coordinates in the valid latitude and longitude ranges are accepted. Consecutive duplicate points are ignored. A move that would duplicate an adjacent point is rejected. Deleting a middle point is rejected if joining its neighbors would create a duplicate leg endpoint. A measurement is capped at 1,000 points. Add remains blocked at the limit, while selection, move, delete, and Undo remain available. The history bound retains the ability to undo all 1,000 additions. ## Interaction and accessibility The visible chart marker stays compact, but an invisible 44 px layer supplies the selection and drag target. Selection is a separate action from movement, so tapping a point does not unexpectedly steal map panning. Deliberate move mode changes the cursor, disables map drag-pan only during an active point drag, suppresses the trailing click, and restores the prior cursor and pan state after commit, cancel, interruption, or teardown. The strip provides labeled Previous, Next, Move, Delete, and chart-center movement controls with the shared 44 px action size. Its rows wrap at narrow widths. Instructions and changed readouts use polite status announcements, and Delete names the selected point for assistive technology. ## State and safety boundaries Measure is session-only. Starting fresh, selecting **Done**, or reloading clears every point. It does not write to Signal K, IndexedDB, or local storage. Moving or deleting a point changes only this temporary advisory measurement. ## Implementation and verification - `src/entities/measure/measure.svelte.ts` owns validation, stable point identity, selection, move preview, inverse operation history, derived legs, and totals. - `src/features/measure/measure-overlay.ts` builds antimeridian-safe per-leg geometry, collision-managed distance labels, the total label, selection styling, the 44 px hit layer, and drag cleanup. - `src/features/measure/MeasureStrip.svelte` owns guidance, adjacent-leg readouts, keyboard-equivalent editing, Undo, confirmed Clear, Done, and nested Escape behavior. - `src/widgets/chart-canvas/ChartCanvas.svelte` resolves vertex hits before chart additions, gives Measure one result per click, and applies the tool cursor as soon as MapLibre creates its canvas without waiting for the base style to load. - `src/features/routing/route-controller.svelte.ts` and `src/app/App.svelte` enforce route exclusion at both tool entry points. Unit coverage verifies operation Undo, invalid and duplicate edits, point limits, selection, drag commit and cancellation, pan restoration, antimeridian geometry and label midpoints, collision settings, theming, unit changes, opacity, and cleanup. The Playwright flow covers a 44 px chart selection target, pointer dragging, delete and Undo, keyboard chart-center movement, nested Escape, menu retention, route exclusion in both directions, cursor restoration, and a 320 px layout.