1 files changed, 36 insertions, 0 deletions
diff --git a/tools/mq_editor/utils.js b/tools/mq_editor/utils.js
new file mode 100644
index 0000000..c38b1f5
--- /dev/null
+++ b/tools/mq_editor/utils.js
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+// Shared utilities for mq_editor
+
+// Evaluate cubic bezier curve at time t (robust: handles dt<=0)
+function evalBezier(curve, t) {
+  const dt = curve.t3 - curve.t0;
+  if (dt <= 0) return curve.v0;
+  let u = (t - curve.t0) / dt;
+  u = Math.max(0, Math.min(1, u));
+  const u1 = 1.0 - u;
+  return u1*u1*u1 * curve.v0 +
+         3*u1*u1*u * curve.v1 +
+         3*u1*u*u  * curve.v2 +
+         u*u*u     * curve.v3;
+}
+
+// Get canvas-relative {x, y} from a mouse event
+function getCanvasCoords(e, canvas) {
+  const rect = canvas.getBoundingClientRect();
+  return { x: e.clientX - rect.left, y: e.clientY - rect.top };
+}
+
+// Build upper/lower band point arrays for a frequency curve.
+// factorAbove/factorBelow are fractional offsets (e.g. 0.02 = ±2%).
+// Returns { upper: [[x,y],...], lower: [[x,y],...] }
+function buildBandPoints(viewer, curve, factorAbove, factorBelow) {
+  const STEPS = 60;
+  const upper = [], lower = [];
+  for (let i = 0; i <= STEPS; ++i) {
+    const t = curve.t0 + (curve.t3 - curve.t0) * i / STEPS;
+    if (t < viewer.t_view_min - 0.01 || t > viewer.t_view_max + 0.01) continue;
+    const f = evalBezier(curve, t);
+    upper.push([viewer.timeToX(t), viewer.freqToY(f * (1 + factorAbove))]);
+    lower.push([viewer.timeToX(t), viewer.freqToY(f * (1 - factorBelow))]);
+  }
+  return { upper, lower };
+}