Configurable grid + snap-to-grid in the layout system (#45)

Closes #44. Two independent grids (garden + per-bed), each with a size and a snap toggle; snapping defaults off. See PR #45 for details.

Co-authored-by: Steve Dudenhoeffer <[email protected]>

web/src/lib/geometry.test.ts

@@ -3,6 +3,9 @@ import {
   clampScale,
   localToWorld,
   screenToWorld,
+  snapLocalToBedGrid,
+  snapPoint,
+  snapValue,
   worldToLocal,
   worldToScreen,
   zoomToFitRect,
@@ -91,3 +94,37 @@ describe('zoomToFitRect', () => {
     expect(fit.scale).toBe(20)
   })
 })
+
+describe('grid snapping', () => {
+  it('snaps a scalar to the nearest multiple of the step', () => {
+    expect(snapValue(37, 30)).toBe(30)
+    expect(snapValue(46, 30)).toBe(60)
+    expect(snapValue(-46, 30)).toBe(-60)
+    expect(snapValue(15, 30)).toBe(30) // .5 rounds up
+  })
+
+  it('leaves a scalar unchanged for a non-positive step', () => {
+    expect(snapValue(37, 0)).toBe(37)
+    expect(snapValue(37, -5)).toBe(37)
+    expect(snapValue(37, NaN)).toBe(37)
+  })
+
+  it('snaps a world point to the origin-anchored garden grid', () => {
+    expect(snapPoint({ x: 37, y: -46 }, 30)).toEqual({ x: 30, y: -60 })
+  })
+
+  it('snaps a local point to the bed grid anchored at the top-left corner', () => {
+    // A 120×80 bed (halfW=60, halfH=40), 30cm grid: lines at x=-60,-30,0,30,60
+    // and y=-40,-10,20 (from the corner, then +30 while ≤ halfH).
+    expect(snapLocalToBedGrid({ x: 5, y: 2 }, 30, 60, 40)).toEqual({ x: 0, y: -10 })
+    expect(snapLocalToBedGrid({ x: 22, y: 18 }, 30, 60, 40)).toEqual({ x: 30, y: 20 })
+  })
+
+  it('clamps a snapped bed point back inside the bed bounds', () => {
+    // Near the far corner, rounding would land at x=90 (> halfW=60); clamp to 60.
+    const p = snapLocalToBedGrid({ x: 100, y: 100 }, 30, 60, 40)
+    expect(p.x).toBeLessThanOrEqual(60)
+    expect(p.y).toBeLessThanOrEqual(40)
+    expect(p.x).toBeGreaterThanOrEqual(-60)
+  })
+})