From fc2128dabeaa1b9a90d5c494a6db3a7e2f45fbe9 Mon Sep 17 00:00:00 2001
From: chris <chris@chrisedwards.tech>
Date: Fri, 4 Sep 2026 11:35:03 -0400
Subject: [PATCH] Fix swipe eating scroll gestures on the detail page
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onSwipe judged horizontal-vs-vertical from a single touchmove sample
compared against the start point. A fast scroll flick's first sample is
often slightly diagonal (thumb motion), so it could get claimed as a
page-swipe and every subsequent touchmove got preventDefault()'d — the
rest of the scroll silently died, so trying to reach off-screen content
in About/Stats/Evolution/etc. would instead flip to the next Pokémon.

Now vertical intent wins by default (bails, permanently, as soon as the
drag is even mildly more vertical than horizontal) and a horizontal
page-swipe only gets claimed once the drag is unambiguous
(dx > 20 && dx > 2*dy). Deliberate left/right swipes still work.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017Ve7HLspzeG2xDPtJQ8vmu
---
 src/lib/swipe.js | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/lib/swipe.js b/src/lib/swipe.js
index dd5fa86..3037c5f 100644
--- a/src/lib/swipe.js
+++ b/src/lib/swipe.js
@@ -32,11 +32,19 @@ export function onSwipe(target, { onLeft, onRight, threshold = 60 } = {}) {
     const dx = e.touches[0].clientX - x0;
     const dy = e.touches[0].clientY - y0;
     if (!claimed) {
-      if (Math.abs(dy) > 12 && Math.abs(dy) > Math.abs(dx)) {
-        active = false; // it's a vertical scroll — let it be
+      const adx = Math.abs(dx);
+      const ady = Math.abs(dy);
+      // Scroll is the default: bail out — permanently — at the first sign of
+      // vertical intent, even a mildly diagonal one. A page full of scrolling
+      // content (tab panels, lists) means a fast flick's first sample is
+      // often diagonal; without this bias it gets misread as a page-swipe
+      // and the rest of the scroll gets eaten by preventDefault().
+      if (ady > 10 && ady > adx * 0.7) {
+        active = false;
         return;
       }
-      if (Math.abs(dx) > 10 && Math.abs(dx) > Math.abs(dy)) claimed = true;
+      // Only claim a horizontal page-swipe once the drag is unambiguous.
+      if (adx > 20 && adx > ady * 2) claimed = true;
     }
     if (claimed) e.preventDefault();
   };