"Contain" images with missing dimensions instead of cropping them (#6828)

* Show unknown aspect as "contain" for autosize

* Fix a flash of wrong position when opening in lightbox

* Fix last frame flash on Android

src/view/com/lightbox/ImageViewing/components/ImageItem/ImageItem.android.tsx

···
           <Animated.View style={imageCropStyle}>
             <Animated.View style={imageStyle}>
               <Image
-                contentFit="cover"
+                contentFit="contain"
                 source={{uri: imageSrc.uri}}
-                placeholderContentFit="cover"
+                placeholderContentFit="contain"
                 placeholder={{uri: imageSrc.thumbUri}}
                 accessibilityLabel={imageSrc.alt}
                 onLoad={

src/view/com/lightbox/ImageViewing/index.tsx

···
 // Original code copied and simplified from the link below as the codebase is currently not maintained:
 // https://github.com/jobtoday/react-native-image-viewing
 
-import React, {useCallback, useEffect, useState} from 'react'
+import React, {useCallback, useEffect, useMemo, useState} from 'react'
 import {
   LayoutAnimation,
   PixelRatio,
···
   restDisplacementThreshold: 0.01,
 }
 
+function canAnimate(lightbox: Lightbox): boolean {
+  return (
+    !PlatformInfo.getIsReducedMotionEnabled() &&
+    lightbox.images.every(
+      img => img.thumbRect && (img.dimensions || img.thumbDimensions),
+    )
+  )
+}
+
 export default function ImageViewRoot({
   lightbox: nextLightbox,
   onRequestClose,
···
       return
     }
 
-    const canAnimate =
-      !PlatformInfo.getIsReducedMotionEnabled() &&
-      nextLightbox.images.every(
-        img => img.thumbRect && (img.dimensions || img.thumbDimensions),
-      )
+    const isAnimated = canAnimate(nextLightbox)
 
     // https://github.com/software-mansion/react-native-reanimated/issues/6677
     rAF_FIXED(() => {
       openProgress.set(() =>
-        canAnimate ? withClampedSpring(1, SLOW_SPRING) : 1,
+        isAnimated ? withClampedSpring(1, SLOW_SPRING) : 1,
       )
     })
     return () => {
       // https://github.com/software-mansion/react-native-reanimated/issues/6677
       rAF_FIXED(() => {
         openProgress.set(() =>
-          canAnimate ? withClampedSpring(0, SLOW_SPRING) : 0,
+          isAnimated ? withClampedSpring(0, SLOW_SPRING) : 0,
         )
       })
     }
···
   openProgress: SharedValue<number>
 }) {
   const {images, index: initialImageIndex} = lightbox
+  const isAnimated = useMemo(() => canAnimate(lightbox), [lightbox])
   const [isScaled, setIsScaled] = useState(false)
   const [isDragging, setIsDragging] = useState(false)
   const [imageIndex, setImageIndex] = useState(initialImageIndex)
···
   const isFlyingAway = useSharedValue(false)
 
   const containerStyle = useAnimatedStyle(() => {
-    if (openProgress.get() < 1 || isFlyingAway.get()) {
-      return {pointerEvents: 'none'}
+    if (openProgress.get() < 1) {
+      return {
+        pointerEvents: 'none',
+        opacity: isAnimated ? 1 : 0,
+      }
     }
-    return {pointerEvents: 'auto'}
+    if (isFlyingAway.get()) {
+      return {
+        pointerEvents: 'none',
+        opacity: 1,
+      }
+    }
+    return {pointerEvents: 'auto', opacity: 1}
   })
 
   const backdropStyle = useAnimatedStyle(() => {

src/view/com/util/images/AutoSizedImage.tsx

···
     if (Number.isNaN(aspectRatio)) {
       aspectRatio = undefined
     }
-  } else {
-    // If we don't know it synchronously, treat it like a square.
-    // We won't use fetched dimensions to avoid a layout shift.
-    aspectRatio = 1
   }
 
   let constrained: number | undefined
···
 
   const cropDisabled = crop === 'none'
   const isCropped = rawIsCropped && !cropDisabled
+  const isContain = aspectRatio === undefined
   const hasAlt = !!image.alt
 
   const contents = (
     <View ref={containerRef} collapsable={false} style={{flex: 1}}>
       <Image
+        contentFit={isContain ? 'contain' : 'cover'}
         style={[a.w_full, a.h_full]}
         source={image.thumb}
         accessible={true} // Must set for `accessibilityLabel` to work
···
         accessibilityLabel={image.alt}
         accessibilityHint=""
         onLoad={e => {
-          fetchedDimsRef.current = {
-            width: e.source.width,
-            height: e.source.height,
+          if (!isContain) {
+            fetchedDimsRef.current = {
+              width: e.source.width,
+              height: e.source.height,
+            }
           }
         }}
       />