From 13d9c2c9080372df75466c8de349fdd21452bedf Mon Sep 17 00:00:00 2001
From: mace <safemind@posteo.net>
Date: Wed, 26 Aug 2026 21:14:52 +0200
Subject: [PATCH] Add swipe navigation and slide transition to article view

Swiping left/right in the single-article view now pages to the
next/previous article, same as the up/down nav buttons. Touch handlers
live on .article-single: a swipe needs >=50px horizontal travel and
<=75px vertical travel to count (so scrolling/diagonal drags don't
trigger it), and multi-touch or swipes starting inside a horizontally
scrollable <pre> block are ignored so code blocks keep their own
scroll behavior.

Also adds a direction-aware slide/fade transition (via Vue's
<Transition>, keyed on currentIndex) when paging between articles,
triggered by both the swipe gesture and the nav buttons.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
---
 vue/src/components/RssFeeds.vue               | 126 ++++++++++--
 vue/src/components/__tests__/RssFeeds.spec.js | 189 ++++++++++++++++++
 2 files changed, 301 insertions(+), 14 deletions(-)

diff --git a/vue/src/components/RssFeeds.vue b/vue/src/components/RssFeeds.vue
index 55c7adc..1821b22 100644
--- a/vue/src/components/RssFeeds.vue
+++ b/vue/src/components/RssFeeds.vue
@@ -1,5 +1,5 @@
 <script setup>
-import { onMounted, onBeforeUnmount, computed, nextTick, watch } from 'vue';
+import { ref, onMounted, onBeforeUnmount, computed, nextTick, watch } from 'vue';
 import { useFeeds } from '@/composables/useFeeds';
 
 const {
@@ -34,6 +34,61 @@ function scrollToNextArticle() {
   }
 }
 
+// Swipe-to-navigate in article view. Transient per-gesture state, not shared
+// app state, so it's kept as plain component-local variables rather than in
+// useFeeds() — nothing outside this component needs it.
+let touchStartX = null
+let touchStartY = null
+
+const SWIPE_THRESHOLD_X = 50 // min horizontal travel (px) to count as a swipe
+const SWIPE_RESTRAINT_Y = 75 // max vertical travel (px) before it's treated as a scroll, not a swipe
+
+// Drives which slide-in/slide-out transition ('slide-next' / 'slide-prev') the
+// article view uses — set right before the index actually changes, by both
+// the nav buttons and the swipe handler below, so the two triggers animate
+// identically.
+const slideDirection = ref('next')
+
+function navigateToNextArticle() {
+  slideDirection.value = 'next'
+  nextArticle()
+}
+
+function navigateToPrevArticle() {
+  slideDirection.value = 'prev'
+  prevArticle()
+}
+
+function onArticleTouchStart(event) {
+  // Ignore multi-touch (pinch-zoom) and swipes starting inside a
+  // horizontally-scrollable code block (.article-feature__content :deep(pre))
+  // — those should scroll the block, not page the article.
+  if (event.touches.length !== 1 || event.target.closest('pre')) {
+    touchStartX = null
+    touchStartY = null
+    return
+  }
+  touchStartX = event.touches[0].clientX
+  touchStartY = event.touches[0].clientY
+}
+
+function onArticleTouchEnd(event) {
+  if (touchStartX === null) return
+  const touch = event.changedTouches[0]
+  const deltaX = touch.clientX - touchStartX
+  const deltaY = touch.clientY - touchStartY
+  touchStartX = null
+  touchStartY = null
+
+  if (Math.abs(deltaX) < SWIPE_THRESHOLD_X || Math.abs(deltaY) > SWIPE_RESTRAINT_Y) return
+
+  if (deltaX < 0) {
+    navigateToNextArticle()
+  } else {
+    navigateToPrevArticle()
+  }
+}
+
 // Small images (icons, logos, ...) look bad stretched to the full-bleed
 // width used for readable article images — leave them at their natural size
 // instead. Intrinsic size is only known once the image has loaded, so check
@@ -126,7 +181,7 @@ onMounted(async () => {
       >&darr;</button>
     </div>
 
-    <div v-else class="article-single">
+    <div v-else class="article-single" @touchstart.passive="onArticleTouchStart" @touchend.passive="onArticleTouchEnd">
       <div v-if="feeds.length == 0" class="empty-state">
         <svg class="empty-state__icon" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
           <circle cx="12" cy="12" r="10"/>
@@ -135,16 +190,18 @@ onMounted(async () => {
         <p class="empty-state__label">All caught up</p>
       </div>
       <template v-else>
-        <article class="article-feature">
-          <p class="article-feature__source">{{ feeds[currentIndex].feedTitle }}</p>
-          <h2 @click="loadReadable(feeds[currentIndex], currentIndex)" class="article-feature__title">{{ feeds[currentIndex].title }}</h2>
-          <h3 class="article-feature__meta">{{ feeds[currentIndex].timestamp }}</h3>
-          <p class="feed-original-link">
-            <a :href="feeds[currentIndex].url" target="_blank" rel="noopener noreferrer">Read original article &#8599;</a>
-            <button type="button" class="feed-share-btn" :title="shareLabel" @click="shareUrl(feeds[currentIndex].url)">{{ shareLabel }}</button>
-          </p>
-          <p class="article-feature__content" :class="{ 'article-feature__content--readable': feeds[currentIndex].readable }" v-html="feeds[currentIndex].content"></p>
-        </article>
+        <Transition :name="`slide-${slideDirection}`">
+          <article class="article-feature" :key="currentIndex">
+            <p class="article-feature__source">{{ feeds[currentIndex].feedTitle }}</p>
+            <h2 @click="loadReadable(feeds[currentIndex], currentIndex)" class="article-feature__title">{{ feeds[currentIndex].title }}</h2>
+            <h3 class="article-feature__meta">{{ feeds[currentIndex].timestamp }}</h3>
+            <p class="feed-original-link">
+              <a :href="feeds[currentIndex].url" target="_blank" rel="noopener noreferrer">Read original article &#8599;</a>
+              <button type="button" class="feed-share-btn" :title="shareLabel" @click="shareUrl(feeds[currentIndex].url)">{{ shareLabel }}</button>
+            </p>
+            <p class="article-feature__content" :class="{ 'article-feature__content--readable': feeds[currentIndex].readable }" v-html="feeds[currentIndex].content"></p>
+          </article>
+        </Transition>
       </template>
 
       <div class="article-nav">
@@ -153,14 +210,14 @@ onMounted(async () => {
           class="article-nav__btn"
           :disabled="currentIndex === 0"
           aria-label="Previous article"
-          @click="prevArticle"
+          @click="navigateToPrevArticle"
         >&uarr;</button>
         <button
           type="button"
           class="article-nav__btn"
           :disabled="feeds.length === 0 || currentIndex === feeds.length - 1"
           aria-label="Next article"
-          @click="nextArticle"
+          @click="navigateToNextArticle"
         >&darr;</button>
       </div>
     </div>
@@ -310,6 +367,7 @@ onMounted(async () => {
   align-items: center;
   padding-top: 1em;
   padding-bottom: 5rem;
+  overflow-x: hidden;
 }
 
 .article-feature {
@@ -317,6 +375,46 @@ onMounted(async () => {
   max-width: 720px;
 }
 
+/* Slide-in/out when paging between articles (swipe or nav buttons). The
+   outgoing article is pulled out of flex flow during its leave transition so
+   the incoming one can take its place immediately, instead of the two
+   stacking and doubling the page height for the transition's duration. */
+.slide-next-enter-active,
+.slide-next-leave-active,
+.slide-prev-enter-active,
+.slide-prev-leave-active {
+  transition: transform 0.28s ease, opacity 0.28s ease;
+}
+
+.slide-next-leave-active,
+.slide-prev-leave-active {
+  position: absolute;
+  left: 0;
+  right: 0;
+  margin-left: auto;
+  margin-right: auto;
+}
+
+.slide-next-enter-from {
+  transform: translateX(100%);
+  opacity: 0;
+}
+
+.slide-next-leave-to {
+  transform: translateX(-100%);
+  opacity: 0;
+}
+
+.slide-prev-enter-from {
+  transform: translateX(-100%);
+  opacity: 0;
+}
+
+.slide-prev-leave-to {
+  transform: translateX(100%);
+  opacity: 0;
+}
+
 .article-feature__source {
   margin: 0 0 0.5em;
   padding: 0 1rem;
diff --git a/vue/src/components/__tests__/RssFeeds.spec.js b/vue/src/components/__tests__/RssFeeds.spec.js
index 11c8a07..e912511 100644
--- a/vue/src/components/__tests__/RssFeeds.spec.js
+++ b/vue/src/components/__tests__/RssFeeds.spec.js
@@ -15,6 +15,20 @@ class FakeIntersectionObserver {
 }
 vi.stubGlobal('IntersectionObserver', FakeIntersectionObserver)
 
+// Shared by the swipe-navigation tests below, which all start from the same
+// two-article article view.
+function twoArticleFeed() {
+  return [
+    {
+      title: 'My Feed',
+      items: [
+        { id: 1, title: 'Article one', content: '<p>one</p>', url: 'https://example.test/1', timestamp: '2026-02-01 10:00:00' },
+        { id: 2, title: 'Article two', content: '<p>two</p>', url: 'https://example.test/2', timestamp: '2026-01-01 10:00:00' },
+      ],
+    },
+  ]
+}
+
 describe('RssFeeds', () => {
   beforeEach(() => {
     localStorage.setItem('user-token', 'test-token')
@@ -345,4 +359,179 @@ describe('RssFeeds', () => {
     const titles = wrapper.findAll('.feed-title').map(el => el.text())
     expect(titles).toEqual(['Article three'])
   })
+
+  it('swipes left to navigate to the next article', async () => {
+    axios.get.mockResolvedValueOnce({ data: { feeds: twoArticleFeed() } })
+    axios.put.mockResolvedValue({ status: 200 })
+
+    const wrapper = mount(RssFeeds)
+    await flushPromises()
+
+    useFeeds().toggleViewMode()
+    await flushPromises()
+
+    const article = wrapper.find('.article-single')
+    await article.trigger('touchstart', { touches: [{ clientX: 200, clientY: 100 }] })
+    await article.trigger('touchend', { changedTouches: [{ clientX: 130, clientY: 100 }] })
+    await flushPromises()
+
+    expect(wrapper.find('.article-single .article-feature__title').text()).toBe('Article two')
+
+    wrapper.unmount()
+  })
+
+  it('swipes right to navigate to the previous article', async () => {
+    axios.get.mockResolvedValueOnce({ data: { feeds: twoArticleFeed() } })
+    axios.put.mockResolvedValue({ status: 200 })
+
+    const wrapper = mount(RssFeeds)
+    await flushPromises()
+
+    useFeeds().toggleViewMode()
+    await flushPromises()
+    await wrapper.findAll('.article-nav__btn')[1].trigger('click')
+    await flushPromises()
+    expect(wrapper.find('.article-single .article-feature__title').text()).toBe('Article two')
+
+    const article = wrapper.find('.article-single')
+    await article.trigger('touchstart', { touches: [{ clientX: 130, clientY: 100 }] })
+    await article.trigger('touchend', { changedTouches: [{ clientX: 200, clientY: 100 }] })
+    await flushPromises()
+
+    expect(wrapper.find('.article-single .article-feature__title').text()).toBe('Article one')
+
+    wrapper.unmount()
+  })
+
+  it('does not navigate on a swipe shorter than the horizontal threshold', async () => {
+    axios.get.mockResolvedValueOnce({ data: { feeds: twoArticleFeed() } })
+    axios.put.mockResolvedValue({ status: 200 })
+
+    const wrapper = mount(RssFeeds)
+    await flushPromises()
+
+    useFeeds().toggleViewMode()
+    await flushPromises()
+
+    const article = wrapper.find('.article-single')
+    await article.trigger('touchstart', { touches: [{ clientX: 200, clientY: 100 }] })
+    await article.trigger('touchend', { changedTouches: [{ clientX: 180, clientY: 100 }] })
+    await flushPromises()
+
+    expect(wrapper.find('.article-single .article-feature__title').text()).toBe('Article one')
+
+    wrapper.unmount()
+  })
+
+  it('does not navigate on a mostly-vertical drag', async () => {
+    axios.get.mockResolvedValueOnce({ data: { feeds: twoArticleFeed() } })
+    axios.put.mockResolvedValue({ status: 200 })
+
+    const wrapper = mount(RssFeeds)
+    await flushPromises()
+
+    useFeeds().toggleViewMode()
+    await flushPromises()
+
+    const article = wrapper.find('.article-single')
+    await article.trigger('touchstart', { touches: [{ clientX: 200, clientY: 100 }] })
+    await article.trigger('touchend', { changedTouches: [{ clientX: 190, clientY: 250 }] })
+    await flushPromises()
+
+    expect(wrapper.find('.article-single .article-feature__title').text()).toBe('Article one')
+
+    wrapper.unmount()
+  })
+
+  it('does not navigate on a diagonal drag that exceeds the vertical restraint, even with a qualifying horizontal delta', async () => {
+    axios.get.mockResolvedValueOnce({ data: { feeds: twoArticleFeed() } })
+    axios.put.mockResolvedValue({ status: 200 })
+
+    const wrapper = mount(RssFeeds)
+    await flushPromises()
+
+    useFeeds().toggleViewMode()
+    await flushPromises()
+
+    const article = wrapper.find('.article-single')
+    await article.trigger('touchstart', { touches: [{ clientX: 200, clientY: 100 }] })
+    await article.trigger('touchend', { changedTouches: [{ clientX: 130, clientY: 200 }] })
+    await flushPromises()
+
+    expect(wrapper.find('.article-single .article-feature__title').text()).toBe('Article one')
+
+    wrapper.unmount()
+  })
+
+  it('ignores a multi-touch gesture (pinch-zoom)', async () => {
+    axios.get.mockResolvedValueOnce({ data: { feeds: twoArticleFeed() } })
+    axios.put.mockResolvedValue({ status: 200 })
+
+    const wrapper = mount(RssFeeds)
+    await flushPromises()
+
+    useFeeds().toggleViewMode()
+    await flushPromises()
+
+    const article = wrapper.find('.article-single')
+    await article.trigger('touchstart', {
+      touches: [{ clientX: 200, clientY: 100 }, { clientX: 50, clientY: 100 }],
+    })
+    await article.trigger('touchend', { changedTouches: [{ clientX: 130, clientY: 100 }] })
+    await flushPromises()
+
+    expect(wrapper.find('.article-single .article-feature__title').text()).toBe('Article one')
+
+    wrapper.unmount()
+  })
+
+  it('does not navigate when a swipe starts inside a code block', async () => {
+    axios.get.mockResolvedValueOnce({
+      data: {
+        feeds: [
+          {
+            title: 'My Feed',
+            items: [
+              { id: 1, title: 'Article one', content: '<pre>some code</pre>', url: 'https://example.test/1', timestamp: '2026-02-01 10:00:00' },
+              { id: 2, title: 'Article two', content: '<p>two</p>', url: 'https://example.test/2', timestamp: '2026-01-01 10:00:00' },
+            ],
+          },
+        ],
+      },
+    })
+    axios.put.mockResolvedValue({ status: 200 })
+
+    const wrapper = mount(RssFeeds)
+    await flushPromises()
+
+    useFeeds().toggleViewMode()
+    await flushPromises()
+
+    await wrapper.find('pre').trigger('touchstart', { touches: [{ clientX: 200, clientY: 100 }] })
+    await wrapper.find('.article-single').trigger('touchend', { changedTouches: [{ clientX: 130, clientY: 100 }] })
+    await flushPromises()
+
+    expect(wrapper.find('.article-single .article-feature__title').text()).toBe('Article one')
+
+    wrapper.unmount()
+  })
+
+  it('does not throw when swiping with an empty feed list', async () => {
+    axios.get.mockResolvedValueOnce({ data: { feeds: [] } })
+
+    const wrapper = mount(RssFeeds)
+    await flushPromises()
+
+    useFeeds().toggleViewMode()
+    await flushPromises()
+
+    const article = wrapper.find('.article-single')
+    await article.trigger('touchstart', { touches: [{ clientX: 200, clientY: 100 }] })
+    await article.trigger('touchend', { changedTouches: [{ clientX: 130, clientY: 100 }] })
+    await flushPromises()
+
+    expect(wrapper.text()).toContain('All caught up')
+
+    wrapper.unmount()
+  })
 })