From a94fe1c9d005267d8e73efc9c21d6f0382141c0b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Horv=C3=A1th=20B=C3=A1lint?=
 <40771359+horvbalint@users.noreply.github.com>
Date: Mon, 12 Jun 2023 20:46:53 +0200
Subject: [PATCH] feat: media preview modal  - better zoom support (#2133)

---
 components/modal/ModalMediaPreview.vue        |  24 +-
 .../modal/ModalMediaPreviewCarousel.vue       | 293 ++++++++++++++----
 2 files changed, 246 insertions(+), 71 deletions(-)

diff --git a/components/modal/ModalMediaPreview.vue b/components/modal/ModalMediaPreview.vue
index 80808775..69dca036 100644
--- a/components/modal/ModalMediaPreview.vue
+++ b/components/modal/ModalMediaPreview.vue
@@ -53,21 +53,19 @@ onUnmounted(() => locked.value = false)
       <div i-ri:arrow-left-s-line text-white />
     </button>
 
-    <div flex flex-row items-center mxa>
-      <div flex="~ col center" max-h-full max-w-full>
-        <ModalMediaPreviewCarousel v-model="index" :media="mediaPreviewList" @close="emit('close')" />
+    <div flex="~ col center" h-full w-full>
+      <ModalMediaPreviewCarousel v-model="index" :media="mediaPreviewList" @close="emit('close')" />
 
-        <div bg="black/30" dark:bg="white/10" ms-4 mb-6 mt-4 text-white rounded-full flex="~ center shrink-0" overflow-hidden>
-          <div v-if="mediaPreviewList.length > 1" p="y-1 x-3" rounded-r-0 shrink-0>
-            {{ index + 1 }} / {{ mediaPreviewList.length }}
-          </div>
-          <p
-            v-if="current.description" bg="dark/30" dark:bg="white/10" p="y-1 x-3" rounded-ie-full line-clamp-1
-            ws-pre-wrap break-all :title="current.description" w-full
-          >
-            {{ current.description }}
-          </p>
+      <div bg="black/30" dark:bg="white/10" mb-6 mt-4 text-white rounded-full flex="~ center shrink-0" overflow-hidden>
+        <div v-if="mediaPreviewList.length > 1" p="y-1 x-3" rounded-r-0 shrink-0>
+          {{ index + 1 }} / {{ mediaPreviewList.length }}
         </div>
+        <p
+          v-if="current.description" bg="dark/30" dark:bg="white/10" p="y-1 x-3" rounded-ie-full line-clamp-1
+          ws-pre-wrap break-all :title="current.description" w-full
+        >
+          {{ current.description }}
+        </p>
       </div>
     </div>
 
diff --git a/components/modal/ModalMediaPreviewCarousel.vue b/components/modal/ModalMediaPreviewCarousel.vue
index f5794c5e..84d4718c 100644
--- a/components/modal/ModalMediaPreviewCarousel.vue
+++ b/components/modal/ModalMediaPreviewCarousel.vue
@@ -1,12 +1,11 @@
 <script setup lang="ts">
+import type { Vector2 } from '@vueuse/gesture'
 import { useGesture } from '@vueuse/gesture'
-import type { PermissiveMotionProperties } from '@vueuse/motion'
 import { useReducedMotion } from '@vueuse/motion'
 import type { mastodon } from 'masto'
 
-const { media = [], threshold = 20 } = defineProps<{
+const { media = [] } = defineProps<{
   media?: mastodon.v1.MediaAttachment[]
-  threshold?: number
 }>()
 
 const emit = defineEmits<{
@@ -17,88 +16,266 @@ const { modelValue } = defineModels<{
   modelValue: number
 }>()
 
-const target = ref()
+const slideGap = 20
+const doubleTapTreshold = 250
+
+const view = ref()
+const slider = ref()
+const slide = ref()
+const image = ref()
 
-const animateTimeout = useTimeout(10)
 const reduceMotion = process.server ? ref(false) : useReducedMotion()
+const isInitialScrollDone = useTimeout(350)
+const canAnimate = computed(() => isInitialScrollDone.value && !reduceMotion.value)
 
-const canAnimate = computed(() => !reduceMotion.value && animateTimeout.value)
+const scale = ref(1)
+const x = ref(0)
+const y = ref(0)
 
-const { motionProperties } = useMotionProperties(target, {
-  cursor: 'grab',
-  scale: 1,
-  x: 0,
-  y: 0,
-})
-const { set } = useSpring(motionProperties as Partial<PermissiveMotionProperties>)
+const isDragging = ref(false)
+const isPinching = ref(false)
 
-function resetZoom() {
-  set({ scale: 1 })
+const maxZoomOut = ref(1)
+const isZoomedIn = computed(() => scale.value > 1)
+
+function goToFocusedSlide() {
+  scale.value = 1
+  x.value = slide.value[modelValue.value].offsetLeft * scale.value
+  y.value = 0
 }
 
-watch(modelValue, resetZoom)
+onMounted(() => {
+  const slideGapAsScale = slideGap / view.value.clientWidth
+  maxZoomOut.value = 1 - slideGapAsScale
 
-const { width, height } = useElementSize(target)
-const { isSwiping, lengthX, lengthY, direction } = useSwipe(target, {
-  threshold: 5,
-  passive: false,
-  onSwipeEnd(e, direction) {
-    // eslint-disable-next-line @typescript-eslint/no-use-before-define
-    if (direction === 'right' && Math.abs(distanceX.value) > threshold) {
-      modelValue.value = Math.max(0, modelValue.value - 1)
-      resetZoom()
-    }
-
-    // eslint-disable-next-line @typescript-eslint/no-use-before-define
-    if (direction === 'left' && Math.abs(distanceX.value) > threshold) {
-      modelValue.value = Math.min(media.length - 1, modelValue.value + 1)
-      resetZoom()
-    }
-
-    // eslint-disable-next-line @typescript-eslint/no-use-before-define
-    if (direction === 'up' && Math.abs(distanceY.value) > threshold)
-      emit('close')
-  },
+  goToFocusedSlide()
 })
+watch(modelValue, goToFocusedSlide)
 
+let lastOrigin = [0, 0]
+let initialScale = 0
 useGesture({
-  onPinch({ offset: [distance, _angle] }) {
-    set({ scale: Math.max(0.5, 1 + distance / 200) })
+  onPinch({ first, initial: [initialDistance], movement: [deltaDistance], da: [distance], origin, touches }) {
+    isPinching.value = true
+
+    if (first) {
+      initialScale = scale.value
+    }
+    else {
+      if (touches === 0)
+        handleMouseWheelZoom(initialScale, deltaDistance, origin)
+      else
+        handlePinchZoom(initialScale, initialDistance, distance, origin)
+    }
+
+    lastOrigin = origin
   },
-  onMove({ movement: [x, y], dragging, pinching }) {
-    if (dragging && !pinching)
-      set({ x, y })
+  onPinchEnd() {
+    isPinching.value = false
+    isDragging.value = false
+
+    if (!isZoomedIn.value)
+      goToFocusedSlide()
+  },
+  onDrag({ movement, delta, pinching, tap, last, swipe, event, xy }) {
+    event.preventDefault()
+
+    if (pinching)
+      return
+
+    if (last)
+      handleLastDrag(tap, swipe, movement, xy)
+    else
+      handleDrag(delta, movement)
   },
 }, {
-  domTarget: target,
+  domTarget: view,
   eventOptions: {
-    passive: true,
+    passive: false,
   },
 })
 
-const distanceX = computed(() => {
-  if (width.value === 0)
-    return 0
+const shiftRestrictions = computed(() => {
+  const focusedImage = image.value[modelValue.value]
+  const focusedSlide = slide.value[modelValue.value]
 
-  if (!isSwiping.value || (direction.value !== 'left' && direction.value !== 'right'))
-    return modelValue.value * 100 * -1
+  const scaledImageWidth = focusedImage.offsetWidth * scale.value
+  const scaledHorizontalOverflow = scaledImageWidth / 2 - view.value.clientWidth / 2 + slideGap
+  const horizontalOverflow = Math.max(0, scaledHorizontalOverflow / scale.value)
 
-  return (lengthX.value / width.value) * 100 * -1 + (modelValue.value * 100) * -1
+  const scaledImageHeight = focusedImage.offsetHeight * scale.value
+  const scaledVerticalOverflow = scaledImageHeight / 2 - view.value.clientHeight / 2 + slideGap
+  const verticalOverflow = Math.max(0, scaledVerticalOverflow / scale.value)
+
+  return {
+    left: focusedSlide.offsetLeft - horizontalOverflow,
+    right: focusedSlide.offsetLeft + horizontalOverflow,
+    top: focusedSlide.offsetTop - verticalOverflow,
+    bottom: focusedSlide.offsetTop + verticalOverflow,
+  }
 })
 
-const distanceY = computed(() => {
-  if (height.value === 0 || !isSwiping.value || direction.value !== 'up')
-    return 0
+function handlePinchZoom(initialScale: number, initialDistance: number, distance: number, [originX, originY]: Vector2) {
+  scale.value = initialScale * (distance / initialDistance)
+  scale.value = Math.max(maxZoomOut.value, scale.value)
 
-  return (lengthY.value / height.value) * 100 * -1
+  const deltaCenterX = originX - lastOrigin[0]
+  const deltaCenterY = originY - lastOrigin[1]
+
+  handleZoomDrag([deltaCenterX, deltaCenterY])
+}
+
+function handleMouseWheelZoom(initialScale: number, deltaDistance: number, [originX, originY]: Vector2) {
+  scale.value = initialScale + (deltaDistance / 1000)
+  scale.value = Math.max(maxZoomOut.value, scale.value)
+
+  const deltaCenterX = lastOrigin[0] - originX
+  const deltaCenterY = lastOrigin[1] - originY
+
+  handleZoomDrag([deltaCenterX, deltaCenterY])
+}
+
+function handleLastDrag(tap: boolean, swipe: Vector2, movement: Vector2, position: Vector2) {
+  isDragging.value = false
+
+  if (tap)
+    handleTap(position)
+  else if (swipe[0] || swipe[1])
+    handleSwipe(swipe, movement)
+  else if (!isZoomedIn.value)
+    slideToClosestSlide()
+}
+
+let lastTapAt = 0
+function handleTap([positionX, positionY]: Vector2) {
+  const now = Date.now()
+  const isDoubleTap = now - lastTapAt < doubleTapTreshold
+  lastTapAt = now
+
+  if (!isDoubleTap)
+    return
+
+  if (isZoomedIn.value) {
+    goToFocusedSlide()
+  }
+  else {
+    const focusedSlideBounding = slide.value[modelValue.value].getBoundingClientRect()
+    const slideCenterX = focusedSlideBounding.left + focusedSlideBounding.width / 2
+    const slideCenterY = focusedSlideBounding.top + focusedSlideBounding.height / 2
+
+    scale.value = 3
+    x.value += positionX - slideCenterX
+    y.value += positionY - slideCenterY
+    restrictShiftToInsideSlide()
+  }
+}
+
+function handleSwipe([horiz, vert]: Vector2, [movementX, movementY]: Vector2) {
+  if (isZoomedIn.value || isPinching.value)
+    return
+
+  const isHorizontalDrag = Math.abs(movementX) >= Math.abs(movementY)
+
+  if (isHorizontalDrag) {
+    if (horiz === 1) // left
+      modelValue.value = Math.max(0, modelValue.value - 1)
+    if (horiz === -1) // right
+      modelValue.value = Math.min(media.length - 1, modelValue.value + 1)
+  }
+  else if (vert === 1 || vert === -1) {
+    emit('close')
+  }
+
+  goToFocusedSlide()
+}
+
+function slideToClosestSlide() {
+  const startOfFocusedSlide = slide.value[modelValue.value].offsetLeft * scale.value
+  const slideWidth = slide.value[modelValue.value].offsetWidth * scale.value
+
+  if (x.value > startOfFocusedSlide + slideWidth / 2)
+    modelValue.value = Math.min(media.length - 1, modelValue.value + 1)
+  else if (x.value < startOfFocusedSlide - slideWidth / 2)
+    modelValue.value = Math.max(0, modelValue.value - 1)
+
+  goToFocusedSlide()
+}
+
+function handleDrag(delta: Vector2, movement: Vector2) {
+  isDragging.value = true
+
+  if (isZoomedIn.value)
+    handleZoomDrag(delta)
+  else
+    handleSlideDrag(movement)
+}
+
+function handleZoomDrag([deltaX, deltaY]: Vector2) {
+  x.value -= deltaX / scale.value
+  y.value -= deltaY / scale.value
+
+  restrictShiftToInsideSlide()
+}
+
+function handleSlideDrag([movementX, movementY]: Vector2) {
+  goToFocusedSlide()
+
+  if (Math.abs(movementY) > Math.abs(movementX)) // vertical movement is more then horizontal
+    y.value -= movementY / scale.value
+  else
+    x.value -= movementX / scale.value
+
+  if (media.length === 1)
+    x.value = 0
+}
+
+function restrictShiftToInsideSlide() {
+  x.value = Math.min(shiftRestrictions.value.right, Math.max(shiftRestrictions.value.left, x.value))
+  y.value = Math.min(shiftRestrictions.value.bottom, Math.max(shiftRestrictions.value.top, y.value))
+}
+
+const sliderStyle = computed(() => {
+  const style = {
+    transform: `scale(${scale.value}) translate(${-x.value}px, ${-y.value}px)`,
+    transition: 'none',
+    gap: `${slideGap}px`,
+  }
+
+  if (canAnimate.value && !isDragging.value && !isPinching.value)
+    style.transition = 'all 0.3s ease'
+
+  return style
 })
+
+const imageStyle = computed(() => ({
+  cursor: isDragging.value ? 'grabbing' : 'grab',
+}))
 </script>
 
 <template>
-  <div ref="target" flex flex-row max-h-full max-w-full overflow-hidden>
-    <div flex :style="{ transform: `translateX(${distanceX}%) translateY(${distanceY}%)`, transition: isSwiping ? 'none' : canAnimate ? 'all 0.5s ease' : 'none' }">
-      <div v-for="item in media" :key="item.id" p4 select-none w-full flex-shrink-0 flex flex-col items-center justify-center>
-        <img max-h-full max-w-full :draggable="false" select-none :src="item.url || item.previewUrl" :alt="item.description || ''">
+  <div ref="view" flex flex-row h-full w-full overflow-hidden>
+    <div ref="slider" :style="sliderStyle" w-full h-full flex items-center>
+      <div
+        v-for="item in media"
+        :key="item.id"
+        ref="slide"
+        flex-shrink-0
+        w-full
+        h-full
+        flex
+        items-center
+        justify-center
+      >
+        <img
+          ref="image"
+          select-none
+          max-w-full
+          max-h-full
+          :style="imageStyle"
+          :draggable="false"
+          :src="item.url || item.previewUrl"
+          :alt="item.description || ''"
+        >
       </div>
     </div>
   </div>