For #3554 - Add DiffUtil to HistoryAdapter

app/src/main/java/org/mozilla/fenix/library/history/HistoryAdapter.kt

@@ -8,6 +8,7 @@ import android.content.Context
 import android.text.format.DateUtils
 import android.view.LayoutInflater
 import android.view.ViewGroup
+import androidx.recyclerview.widget.DiffUtil
 import androidx.recyclerview.widget.RecyclerView
 import io.reactivex.Observer
 import org.mozilla.fenix.R
@@ -101,11 +102,48 @@ class HistoryAdapter(
     var selected = listOf<HistoryItem>()
 
     fun updateData(items: List<HistoryItem>, mode: HistoryState.Mode) {
+        val diffUtil = DiffUtil.calculateDiff(
+            HistoryDiffUtil(
+                this.historyList,
+                HistoryList(items),
+                HistoryList(selected),
+                HistoryList((mode as? HistoryState.Mode.Editing)?.selectedItems ?: listOf()),
+                this.mode,
+                mode
+            )
+        )
+
         this.historyList = HistoryList(items)
         this.mode = mode
         this.selected = if (mode is HistoryState.Mode.Editing) mode.selectedItems else listOf()
 
-        notifyDataSetChanged()
+        diffUtil.dispatchUpdatesTo(this)
+    }
+
+    private class HistoryDiffUtil(
+        val old: HistoryList,
+        val new: HistoryList,
+        val oldSelected: HistoryList,
+        val newSelected: HistoryList,
+        val oldMode: HistoryState.Mode,
+        val newMode: HistoryState.Mode
+    ) : DiffUtil.Callback() {
+        override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean =
+            old.items[oldItemPosition] == new.items[newItemPosition]
+
+        override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
+            val modesEqual = oldMode::class == newMode::class
+            val isStillSelected =
+                oldSelected.items.contains(old.items[oldItemPosition]) &&
+                        newSelected.items.contains(new.items[newItemPosition])
+            val isStillNotSelected =
+                !oldSelected.items.contains(old.items[oldItemPosition]) &&
+                        !newSelected.items.contains(new.items[newItemPosition])
+            return modesEqual && (isStillSelected || isStillNotSelected)
+        }
+
+        override fun getOldListSize(): Int = old.items.size
+        override fun getNewListSize(): Int = new.items.size
     }
 
     override fun getItemCount(): Int = historyList.items.size

app/src/main/java/org/mozilla/fenix/library/history/viewholders/HistoryDeleteButtonViewHolder.kt

@@ -32,6 +32,7 @@ class HistoryDeleteButtonViewHolder(
             }
         }
     }
+
     fun bind(mode: HistoryState.Mode) {
         this.mode = mode
 

app/src/main/java/org/mozilla/fenix/library/history/viewholders/HistoryListItemViewHolder.kt

@@ -103,7 +103,7 @@ class HistoryListItemViewHolder(
             if (selected) {
                 favicon.setImageResource(R.drawable.mozac_ic_check)
             } else {
-                favicon.setImageResource(0)
+                updateFavIcon(item.url)
             }
         } else {
             val backgroundTint = ThemeManager.resolveAttribute(R.attr.neutral, itemView.context)

app/src/main/res/layout/delete_history_button.xml

@@ -2,12 +2,16 @@
 <!-- This Source Code Form is subject to the terms of the Mozilla Public
    - License, v. 2.0. If a copy of the MPL was not distributed with this
    - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
-<com.google.android.material.button.MaterialButton xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
-    android:id="@+id/delete_history_button"
-    style="@style/ThemeIndependentMaterialGreyButtonDestructive"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
-    android:layout_margin="16dp"
-    android:text="@string/history_delete_all"
-    app:rippleColor="?secondaryText" />
+    android:layout_margin="16dp">
+    <com.google.android.material.button.MaterialButton
+        android:id="@+id/delete_history_button"
+        style="@style/ThemeIndependentMaterialGreyButtonDestructive"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:text="@string/history_delete_all"
+        app:rippleColor="?secondaryText" />
+</FrameLayout>