better fib left start

docs/implementation.md

@@ -1216,3 +1216,6 @@ shares numbering, hide, delete and colour with other drawings, but it is
 not a confluence level. The chart draws native price lines at 0, 23.6,
 38.2, 50, 61.8, 78.6 and 100 between the two prices. 0% is the first
 click.
+
+Levels no longer span the full chart: they start at the first click and run
+to the right, with a vertical rail at the origin so the swing is obvious.

static/chart.js

@@ -72,6 +72,120 @@ class RthLinesPrimitive {
   }
 }
 
+class FibLevelsPrimitive {
+  constructor(locateTime) {
+    this._locate = locateTime;
+    this._fibs = [];
+    this._series = null;
+    this._requestUpdate = null;
+    this._items = [];
+    this._view = {
+      update: () => this._sync(),
+      renderer: () => this._renderer,
+    };
+    this._renderer = { draw: target => this._draw(target) };
+  }
+
+  attached(param) {
+    this._series = param.series;
+    this._requestUpdate = param.requestUpdate;
+  }
+
+  detached() {
+    this._series = null;
+    this._requestUpdate = null;
+  }
+
+  setFibs(fibs) {
+    this._fibs = fibs || [];
+    if (this._requestUpdate) this._requestUpdate();
+  }
+
+  updateAllViews() {
+    this._view.update();
+  }
+
+  paneViews() {
+    return [this._view];
+  }
+
+  _sync() {
+    const items = [];
+    if (!this._series) {
+      this._items = [];
+      return;
+    }
+    for (const fib of this._fibs) {
+      if (fib.hidden) continue;
+      const x0 = this._locate(fib.anchor_t);
+      const y0 = this._series.priceToCoordinate(Number(fib.anchor_p));
+      const endP = Number(fib.anchor_p) + Number(fib.slope || 0)
+        * (Number(fib.last_t) - Number(fib.anchor_t));
+      const y1 = this._series.priceToCoordinate(endP);
+      const width = Math.max(1, Number(fib.line_width) || 2);
+      const color = fib.color || '#c8992f';
+      if (x0 != null && y0 != null && y1 != null) {
+        items.push({
+          kind: 'rail', x: x0, y0, y1, color, width,
+        });
+      }
+      for (const level of ConfluenceChart.fibPrices(fib)) {
+        const y = this._series.priceToCoordinate(level.price);
+        if (y == null) continue;
+        const major = level.r === 0 || level.r === 0.5 || level.r === 0.618 || level.r === 1;
+        items.push({
+          kind: 'level',
+          x0,
+          y,
+          color,
+          width,
+          dashed: !major,
+          label: `${level.label}  ${level.price.toFixed(2)}`,
+        });
+      }
+    }
+    this._items = items;
+  }
+
+  _draw(target) {
+    if (!this._items.length) return;
+    target.useMediaCoordinateSpace(scope => {
+      const ctx = scope.context;
+      const right = scope.mediaSize.width;
+      ctx.save();
+      ctx.font = '10px "IBM Plex Mono", ui-monospace, monospace';
+      for (const item of this._items) {
+        if (item.kind === 'rail') {
+          ctx.strokeStyle = item.color;
+          ctx.lineWidth = item.width;
+          ctx.setLineDash([]);
+          ctx.globalAlpha = 0.85;
+          ctx.beginPath();
+          ctx.moveTo(item.x + 0.5, item.y0);
+          ctx.lineTo(item.x + 0.5, item.y1);
+          ctx.stroke();
+          continue;
+        }
+        const start = item.x0 == null ? 0 : Math.max(0, item.x0);
+        if (start > right) continue;
+        ctx.strokeStyle = item.color;
+        ctx.fillStyle = item.color;
+        ctx.lineWidth = item.width;
+        ctx.setLineDash(item.dashed ? [5, 4] : []);
+        ctx.globalAlpha = 0.9;
+        ctx.beginPath();
+        ctx.moveTo(start, item.y + 0.5);
+        ctx.lineTo(right, item.y + 0.5);
+        ctx.stroke();
+        ctx.setLineDash([]);
+        ctx.globalAlpha = 1;
+        ctx.fillText(item.label, right - ctx.measureText(item.label).width - 6, item.y - 4);
+      }
+      ctx.restore();
+    });
+  }
+}
+
 class ConfluenceChart {
   constructor() {
     this.chart = null;
@@ -135,7 +249,7 @@ class ConfluenceChart {
     this.rthPrimitive = null;
     this.rthEnabled = true;
     this.fibs = [];
-    this.fibLines = new Map();
+    this.fibPrimitive = null;
     this.fibPreview = null;
     this.futureSpace = null;
     this.snapDot = null;
@@ -327,6 +441,8 @@ class ConfluenceChart {
     // something to label and so timeToCoordinate answers out there.
     this.rthPrimitive = new RthLinesPrimitive();
     this.candles.attachPrimitive(this.rthPrimitive);
+    this.fibPrimitive = new FibLevelsPrimitive(time => this.coordinateAtTime(time));
+    this.candles.attachPrimitive(this.fibPrimitive);
     this.futureSpace = this.chart.addSeries(LightweightCharts.LineSeries, {
       priceScaleId: 'right',
       color: 'rgba(0,0,0,0)',
@@ -706,33 +822,7 @@ class ConfluenceChart {
   }
 
   syncFibLines() {
-    if (!this.candles) return;
-    const wanted = new Set();
-    for (const fib of this.fibs) {
-      if (fib.hidden) continue;
-      for (const level of ConfluenceChart.fibPrices(fib)) {
-        const id = `${fib.id}:${level.r}`;
-        wanted.add(id);
-        const width = Math.max(1, Number(fib.line_width) || 2);
-        const major = level.r === 0 || level.r === 0.5 || level.r === 0.618 || level.r === 1;
-        const options = {
-          price: level.price,
-          color: fib.color || '#c8992f',
-          lineWidth: width,
-          lineStyle: major ? LightweightCharts.LineStyle.Solid : LightweightCharts.LineStyle.Dashed,
-          axisLabelVisible: true,
-          title: `${level.label}  ${level.price.toFixed(2)}`,
-        };
-        const existing = this.fibLines.get(id);
-        if (existing) existing.applyOptions(options);
-        else this.fibLines.set(id, this.candles.createPriceLine(options));
-      }
-    }
-    for (const [id, line] of this.fibLines) {
-      if (wanted.has(id)) continue;
-      this.candles.removePriceLine(line);
-      this.fibLines.delete(id);
-    }
+    if (this.fibPrimitive) this.fibPrimitive.setFibs(this.fibs.filter(fib => !fib.hidden));
   }
 
   setComments(comments) {
@@ -1946,11 +2036,24 @@ class ConfluenceChart {
     this.fibPreview.removeAttribute('hidden');
     this.fibPreview.replaceChildren();
     const width = this.overlayLayer?.clientWidth || this.chartEl.clientWidth;
+    const originX = start.t == null ? 0 : (this.coordinateAtTime(start.t) ?? 0);
+    const yStart = this.candles.priceToCoordinate(start.p);
+    const yEnd = this.candles.priceToCoordinate(end.p);
+    if (yStart != null && yEnd != null) {
+      const rail = document.createElementNS('http://www.w3.org/2000/svg', 'line');
+      rail.setAttribute('x1', originX);
+      rail.setAttribute('x2', originX);
+      rail.setAttribute('y1', yStart);
+      rail.setAttribute('y2', yEnd);
+      rail.setAttribute('stroke', '#c8992f');
+      rail.setAttribute('stroke-width', 2);
+      this.fibPreview.appendChild(rail);
+    }
     for (const item of ConfluenceChart.FIB_RATIOS) {
       const y = this.candles.priceToCoordinate(start.p + (end.p - start.p) * item.r);
       if (y == null) continue;
       const line = document.createElementNS('http://www.w3.org/2000/svg', 'line');
-      line.setAttribute('x1', 0);
+      line.setAttribute('x1', originX);
       line.setAttribute('x2', width);
       line.setAttribute('y1', y);
       line.setAttribute('y2', y);