From 3a58f98acffff81e359bd902130115934a6cf2f5 Mon Sep 17 00:00:00 2001
From: Thibaud <thibaud.gasser@gmx.com>
Date: Sat, 15 Aug 2026 13:44:15 +0200
Subject: [PATCH] spline: convert screen to canvas coordinates

---
 spline.ts | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/spline.ts b/spline.ts
index ea568b8..64d552c 100644
--- a/spline.ts
+++ b/spline.ts
@@ -65,13 +65,16 @@ function init() {
 
     canvas.onmousedown = (evt: MouseEvent) => {
         const { clientX, clientY } = evt;
+        const rect = ctx.canvas.getBoundingClientRect();
+        const click = { x: clientX - rect.left, y: clientY - rect.top };  // screen to canvas coordinates
+
         for (const p of points) {
-            if (Math.abs(p.x - clientX) < 10 && Math.abs(p.y - clientY) < 10) {
+            if (Math.abs(p.x - click.x) < 10 && Math.abs(p.y - click.y) < 10) {
                 selection = points.indexOf(p);
             }
         }
         if (selection === undefined) {
-            points.push({ x: clientX, y: clientY });
+            points.push({ x: click.x, y: click.y });
             // redraw
             ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
             draw(ctx, points);