MultiSourceHelper.java -> MultiSourceHelper.kt

Summary:
## Changelog:
[Internal] -

As in the title.

Differential Revision: D55640126

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/image/ReactImageView.java

@@ -578,8 +578,8 @@ private void setSourceImage() {
     } else if (hasMultipleSources()) {
       MultiSourceResult multiSource =
           MultiSourceHelper.getBestSourceForSize(getWidth(), getHeight(), mSources);
-      mImageSource = multiSource.getBestResult();
-      mCachedImageSource = multiSource.getBestResultInCache();
+      mImageSource = multiSource.bestResult;
+      mCachedImageSource = multiSource.bestResultInCache;
       return;
     }
 

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/imagehelper/MultiSourceHelper.kt

@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.views.imagehelper
+
+import com.facebook.imagepipeline.core.ImagePipelineFactory
+
+/** Helper class for dealing with multisource images. */
+public object MultiSourceHelper {
+  public fun getBestSourceForSize(
+      width: Int,
+      height: Int,
+      sources: List<ImageSource>
+  ): MultiSourceResult = getBestSourceForSize(width, height, sources, 1.0)
+
+  /**
+   * Chooses the image source with the size closest to the target image size.
+   *
+   * @param width the width of the view that will be used to display this image
+   * @param height the height of the view that will be used to display this image
+   * @param sources the list of potential image sources to choose from
+   * @param multiplier the area of the view will be multiplied by this number before calculating the
+   *   best source; this is useful if the image will be displayed bigger than the view (e.g. zoomed)
+   */
+  private fun getBestSourceForSize(
+      width: Int,
+      height: Int,
+      sources: List<ImageSource>,
+      multiplier: Double
+  ): MultiSourceResult {
+    // no sources
+    if (sources.isEmpty()) {
+      return MultiSourceResult(null, null)
+    }
+
+    // single source
+    if (sources.size == 1) {
+      return MultiSourceResult(sources[0], null)
+    }
+
+    // For multiple sources, we first need the view's size in order to determine the best source to
+    // load. If we haven't been measured yet, return null and wait for onSizeChanged.
+    if (width <= 0 || height <= 0) {
+      return MultiSourceResult(null, null)
+    }
+    val imagePipeline = ImagePipelineFactory.getInstance().imagePipeline
+    var best: ImageSource? = null
+    var bestCached: ImageSource? = null
+    val viewArea = width * height * multiplier
+    var bestPrecision = Double.MAX_VALUE
+    var bestCachePrecision = Double.MAX_VALUE
+    for (source in sources) {
+      val precision = Math.abs(1.0 - source.size / viewArea)
+      if (precision < bestPrecision) {
+        bestPrecision = precision
+        best = source
+      }
+      if (precision < bestCachePrecision &&
+          (imagePipeline.isInBitmapMemoryCache(source.uri) ||
+              imagePipeline.isInDiskCacheSync(source.uri))) {
+        bestCachePrecision = precision
+        bestCached = source
+      }
+    }
+    if (bestCached != null && best != null && bestCached.source == best.source) {
+      bestCached = null
+    }
+    return MultiSourceResult(best, bestCached)
+  }
+
+  class MultiSourceResult(
+      /**
+       * Get the best result overall (closest in size to the view's size). Can be null if there were
+       * no sources to choose from, or if there were more than 1 sources but width/height were 0.
+       */
+      @JvmField val bestResult: ImageSource?,
+      /**
+       * Get the best result (closest in size to the view's size) that is also in cache. If this
+       * would be the same as the source from [.getBestResult], this will return `null` instead.
+       */
+      @JvmField val bestResultInCache: ImageSource?
+  )
+}