From b99e3346a3bb30d1c2b4179bed403de0693b9253 Mon Sep 17 00:00:00 2001
From: Yevhenii Viazovskyi <yevhenii.viazovskyi@gmail.com>
Date: Tue, 26 May 2026 13:21:56 +0000
Subject: [PATCH] fix: adjust trackpad detection and wheel zoom scaling

---
 core/src/helpers.ts   | 16 ++++++++--------
 core/src/zoompinch.ts |  6 +++++-
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/core/src/helpers.ts b/core/src/helpers.ts
index a397852..3a3c8c7 100644
--- a/core/src/helpers.ts
+++ b/core/src/helpers.ts
@@ -48,14 +48,14 @@ export function round(value: number, decimals: number) {
 }
 
 export function detectTrackpad(event: WheelEvent): boolean {
-  // deltaMode === 0 means the browser is reporting pixel-level deltas, which
-  // is the reliable cross-browser signal for trackpad (and touch) input.
-  // Mouse wheels report in line units (deltaMode === 1) or produce large
-  // discrete pixel values that don't use pixel mode.
-  // We avoid the fragile wheelDeltaY / deltaY * -3 ratio check because it
-  // breaks during high-velocity momentum scrolling on macOS, causing the
-  // canvas to jump 25x further than intended.
-  return event.deltaMode === 0;
+  // Line/page mode is always a mouse wheel.
+  if (event.deltaMode !== 0) return false;
+
+  // In pixel mode both inputs show up, so fall back to magnitude:
+  // trackpads send small deltas (usually under ~30), mouse wheels send
+  // chunks of ~100+ per notch. 50 sits comfortably between them.
+  const dominantDelta = Math.max(Math.abs(event.deltaX), Math.abs(event.deltaY));
+  return dominantDelta < 50;
 }
 export function normalizeWheelDelta(event: WheelEvent): { deltaX: number; deltaY: number } {
   let { deltaX, deltaY, deltaMode } = event;
diff --git a/core/src/zoompinch.ts b/core/src/zoompinch.ts
index 3b093e5..5a6a3c8 100644
--- a/core/src/zoompinch.ts
+++ b/core/src/zoompinch.ts
@@ -237,7 +237,11 @@ export class Zoompinch extends EventTarget {
 
     if (ctrlKey) {
       const zoomSpeed = isTrackpad ? 0.01 * this.zoomSpeedAppleTrackpad : 0.1 * this.zoomSpeed;
-      const scaleFactor = 1 + -deltaY * zoomSpeed;
+      // Cap the per-event multiplier so a single oversized wheel event
+      // cannot drive scaleFactor to 0 or negative — which would clamp newScale to
+      // minScale on the first tick and silently kill zoom.
+      const cappedDelta = clamp(-deltaY * zoomSpeed, -0.5, 0.5);
+      const scaleFactor = 1 + cappedDelta;
 
       let newScale = currScale * scaleFactor;