Rely solely on recyclerview for lazy loading

Closes https://github.com/FossifyOrg/Gallery/issues/136

- Remove manual lazy loading mechanism
- Disable cross fade when loading from cache

app/src/main/kotlin/org/fossify/gallery/adapters/MediaAdapter.kt

@@ -4,8 +4,6 @@ import android.content.Intent
 import android.content.pm.ShortcutInfo
 import android.content.pm.ShortcutManager
 import android.graphics.drawable.Icon
-import android.os.Handler
-import android.os.Looper
 import android.view.Menu
 import android.view.View
 import android.view.ViewGroup
@@ -38,11 +36,8 @@ import org.fossify.gallery.models.ThumbnailSection
 class MediaAdapter(
     activity: BaseSimpleActivity, var media: ArrayList<ThumbnailItem>, val listener: MediaOperationsListener?, val isAGetIntent: Boolean,
     val allowMultiplePicks: Boolean, val path: String, recyclerView: MyRecyclerView, itemClick: (Any) -> Unit
-) :
-    MyRecyclerViewAdapter(activity, recyclerView, itemClick), RecyclerViewFastScroller.OnPopupTextUpdate {
+) : MyRecyclerViewAdapter(activity, recyclerView, itemClick), RecyclerViewFastScroller.OnPopupTextUpdate {
 
-    private val INSTANT_LOAD_DURATION = 2000L
-    private val IMAGE_LOAD_DELAY = 100L
     private val ITEM_SECTION = 0
     private val ITEM_MEDIUM_VIDEO_PORTRAIT = 1
     private val ITEM_MEDIUM_PHOTO = 2
@@ -50,10 +45,7 @@ class MediaAdapter(
     private val config = activity.config
     private val viewType = config.getFolderViewType(if (config.showAll) SHOW_ALL else path)
     private val isListViewType = viewType == VIEW_TYPE_LIST
-    private var visibleItemPaths = ArrayList<String>()
     private var rotatedImagePaths = ArrayList<String>()
-    private var loadImageInstantly = false
-    private var delayHandler = Handler(Looper.getMainLooper())
     private var currentMediaHash = media.hashCode()
     private val hasOTGConnected = activity.hasOTGConnected()
 
@@ -69,7 +61,6 @@ class MediaAdapter(
 
     init {
         setupDragListener(true)
-        enableInstantLoad()
     }
 
     override fun getActionMenuId() = R.menu.cab_media
@@ -97,10 +88,6 @@ class MediaAdapter(
 
     override fun onBindViewHolder(holder: MyRecyclerViewAdapter.ViewHolder, position: Int) {
         val tmbItem = media.getOrNull(position) ?: return
-        if (tmbItem is Medium) {
-            visibleItemPaths.add(tmbItem.path)
-        }
-
         val allowLongPress = (!isAGetIntent || allowMultiplePicks) && tmbItem is Medium
         holder.bindView(tmbItem, tmbItem is Medium, allowLongPress) { itemView, adapterPosition ->
             if (tmbItem is Medium) {
@@ -197,7 +184,6 @@ class MediaAdapter(
         super.onViewRecycled(holder)
         if (!activity.isDestroyed) {
             val itemView = holder.itemView
-            visibleItemPaths.remove(itemView.allViews.firstOrNull { it.id == R.id.medium_name }?.tag)
             val tmb = itemView.allViews.firstOrNull { it.id == R.id.medium_thumbnail }
             if (tmb != null) {
                 Glide.with(activity).clear(tmb)
@@ -254,7 +240,6 @@ class MediaAdapter(
                     activity.updateDBMediaPath(firstPath, it)
 
                     activity.runOnUiThread {
-                        enableInstantLoad()
                         listener?.refreshItems()
                         finishActMode()
                     }
@@ -262,7 +247,6 @@ class MediaAdapter(
             }
         } else {
             RenameDialog(activity, getSelectedPaths(), true) {
-                enableInstantLoad()
                 listener?.refreshItems()
                 finishActMode()
             }
@@ -572,7 +556,6 @@ class MediaAdapter(
         if (thumbnailItems.hashCode() != currentMediaHash) {
             currentMediaHash = thumbnailItems.hashCode()
             media = thumbnailItems
-            enableInstantLoad()
             notifyDataSetChanged()
             finishActMode()
         }
@@ -580,7 +563,6 @@ class MediaAdapter(
 
     fun updateDisplayFilenames(displayFilenames: Boolean) {
         this.displayFilenames = displayFilenames
-        enableInstantLoad()
         notifyDataSetChanged()
     }
 
@@ -599,13 +581,6 @@ class MediaAdapter(
         notifyDataSetChanged()
     }
 
-    private fun enableInstantLoad() {
-        loadImageInstantly = true
-        delayHandler.postDelayed({
-            loadImageInstantly = false
-        }, INSTANT_LOAD_DURATION)
-    }
-
     private fun setupThumbnail(view: View, medium: Medium) {
         val isSelected = selectedKeys.contains(medium.path.hashCode())
         bindItem(view, medium).apply {
@@ -681,7 +656,6 @@ class MediaAdapter(
                 else -> ROUNDED_CORNERS_NONE
             }
 
-            if (loadImageInstantly) {
             activity.loadImage(
                 type = medium.type,
                 path = path,
@@ -697,30 +671,6 @@ class MediaAdapter(
                     mediumThumbnail.setImageDrawable(AppCompatResources.getDrawable(activity, R.drawable.ic_vector_warning_colored))
                 }
             )
-            } else {
-                mediumThumbnail.setImageDrawable(null)
-                mediumThumbnail.isHorizontalScrolling = scrollHorizontally
-                delayHandler.postDelayed({
-                    val isVisible = visibleItemPaths.contains(medium.path)
-                    if (isVisible) {
-                        activity.loadImage(
-                            type = medium.type,
-                            path = path,
-                            target = mediumThumbnail,
-                            horizontalScroll = scrollHorizontally,
-                            animateGifs = animateGifs,
-                            cropThumbnails = cropThumbnails,
-                            roundCorners = roundedCorners,
-                            signature = medium.getKey(),
-                            skipMemoryCacheAtPaths = rotatedImagePaths,
-                            onError = {
-                                mediumThumbnail.scaleType = ImageView.ScaleType.CENTER
-                                mediumThumbnail.setImageDrawable(AppCompatResources.getDrawable(activity, R.drawable.ic_vector_warning_colored))
-                            }
-                        )
-                    }
-                }, IMAGE_LOAD_DELAY)
-            }
 
             if (isListViewType) {
                 mediumName.setTextColor(textColor)

app/src/main/kotlin/org/fossify/gallery/extensions/Context.kt

@@ -28,7 +28,6 @@ import com.bumptech.glide.load.engine.GlideException
 import com.bumptech.glide.load.resource.bitmap.CenterCrop
 import com.bumptech.glide.load.resource.bitmap.FitCenter
 import com.bumptech.glide.load.resource.bitmap.RoundedCorners
-import com.bumptech.glide.load.resource.drawable.DrawableTransitionOptions
 import com.bumptech.glide.request.RequestListener
 import com.bumptech.glide.request.RequestOptions
 import com.bumptech.glide.request.target.Target
@@ -586,7 +585,7 @@ fun Context.loadImageBase(
         .load(path)
         .apply(options)
         .set(WebpDownsampler.USE_SYSTEM_DECODER, false) // CVE-2023-4863
-        .transition(DrawableTransitionOptions.withCrossFade(crossFadeDuration))
+        .transition(getOptionalCrossFadeTransition(crossFadeDuration))
 
     builder = builder.listener(object : RequestListener<Drawable> {
         override fun onLoadFailed(e: GlideException?, model: Any?, targetBitmap: Target<Drawable>, isFirstResource: Boolean): Boolean {
@@ -627,7 +626,7 @@ fun Context.loadSVG(
         .listener(SvgSoftwareLayerSetter())
         .load(path)
         .apply(options)
-        .transition(DrawableTransitionOptions.withCrossFade(crossFadeDuration))
+        .transition(getOptionalCrossFadeTransition(crossFadeDuration))
 
     if (roundCorners != ROUNDED_CORNERS_NONE) {
         val cornerSize =

app/src/main/kotlin/org/fossify/gallery/extensions/Glide.kt

@@ -0,0 +1,19 @@
+package org.fossify.gallery.extensions
+
+import com.bumptech.glide.load.DataSource
+import com.bumptech.glide.load.resource.drawable.DrawableTransitionOptions
+import com.bumptech.glide.request.transition.DrawableCrossFadeFactory
+import com.bumptech.glide.request.transition.TransitionFactory
+
+/**
+ * Cross fade transition option that disabled fading when loading from cache.
+ */
+fun getOptionalCrossFadeTransition(duration: Int): DrawableTransitionOptions {
+    return DrawableTransitionOptions.with(
+        TransitionFactory { dataSource, isFirstResource ->
+            if (dataSource == DataSource.RESOURCE_DISK_CACHE) return@TransitionFactory null
+            DrawableCrossFadeFactory.Builder(duration).build().build(dataSource, isFirstResource)
+        }
+    )
+}
+