more efficient shortest-distance pocket routing

src/geo/polygon.js

@@ -1800,7 +1800,7 @@ class Polygon {
      * print paths.
      *
      * @param {Point} target
-     * @return {Object} {point:point, distance:distance}
+     * @return {Object} {distance, point, index: point_index}
      */
     findClosestPointTo(target) {
         let dist,

src/kiri-mode/cam/ops.js

@@ -1383,7 +1383,7 @@ class OpPocket extends CamOp {
 
     prepare(ops, progress) {
         let { op, state, pockets } = this;
-        let { setTool, setSpindle, setTolerance, sliceOutput } = ops;
+        let { setTool, setSpindle, setTolerance, sliceOutput, getPrintPoint } = ops;
         let { process } = state.settings;
 
         setTool(op.tool, op.rate);
@@ -1393,13 +1393,37 @@ class OpPocket extends CamOp {
             setTolerance(this.topo.tolerance);
         }
 
-        for (let sliceOut of pockets) {
+        // eliminate empty pockets
-            sliceOutput(sliceOut, {
+        pockets = pockets.filter(p => p.length);
-                cutdir: process.camConventional,
+
-                depthFirst: process.camDepthFirst && !state.isIndexed,
+        // pockets is an [ array of an [ array of slices ] ]
-                easeDown: op.down && process.easeDown ? op.down : 0,
+        // each top level array is a pocket containing a [ z layer array of slices ]
-                progress: (n,m) => progress(n/m, "pocket")
+        // follow each pocket to the next closest one from previous exit
-            });
+        for (;;) {
+            let printPoint = getPrintPoint();
+            let min = {
+                dist: Infinity,
+                pocket: undefined
+            };
+            for (let pocket of pockets.filter(p => !p.used)) {
+                let poly = pocket[0].camLines.slice().sort((a,b) => b.area() - a.area())[0];
+                let find = poly.findClosestPointTo(printPoint);
+                if (find.distance < min.dist) {
+                    min.pocket = pocket;
+                    min.dist = find.distance;
+                }
+            }
+            if (min.pocket) {
+                min.pocket.used = true;
+                sliceOutput(min.pocket, {
+                    cutdir: process.camConventional,
+                    depthFirst: process.camDepthFirst && !state.isIndexed,
+                    easeDown: op.down && process.easeDown ? op.down : 0,
+                    progress: (n,m) => progress(n/m, "pocket")
+                });
+            } else {
+                break;
+            }
         }
     }
 }

src/kiri-mode/cam/prepare.js

@@ -437,6 +437,12 @@ function prepEach(widget, settings, print, firstPoint, update) {
         );
     }
 
+    /**
+     * output an array of slices that form a pocket
+     *
+     * @param {Slice[]} top-down Z stack of slices
+     * @param {*} opts
+     */
     function sliceOutput(sliceOut, opts = {}) {
         const { cutdir, depthFirst, easeDown, progress } = opts;
 
@@ -518,6 +524,7 @@ function prepEach(widget, settings, print, firstPoint, update) {
         setTolerance,
         setPrintPoint,
         setLasering,
+        getPrintPoint() { return printPoint },
         printPoint,
         newLayer,
         addGCode,