From d62e2705dc263e86f342366a1b5aa35e3aab2579 Mon Sep 17 00:00:00 2001
From: Kimura Youichi <kim.upsilon@bucyou.net>
Date: Sat, 7 Mar 2020 23:53:21 +0900
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---
 OpenTween/DetailsListView.cs | 36 ++++++++++++++++++++++++++++++------
 OpenTween/NativeMethods.cs   |  5 +++--
 OpenTween/Tween.cs           |  5 -----
 3 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/OpenTween/DetailsListView.cs b/OpenTween/DetailsListView.cs
index cf6f1ab55..23ad4cb99 100644
--- a/OpenTween/DetailsListView.cs
+++ b/OpenTween/DetailsListView.cs
@@ -70,15 +70,39 @@ public int SelectionMark
 
         public void SelectItems(int[] indices)
         {
-            foreach (var index in indices)
-            {
-                if (index < 0 || index >= this.VirtualListSize)
-                    throw new ArgumentOutOfRangeException(nameof(indices));
+            var listSize = this.VirtualListSize;
+            if (indices.Any(x => x < 0 || x >= listSize))
+                throw new ArgumentOutOfRangeException(nameof(indices));
 
-                NativeMethods.SelectItem(this, index);
+            if (indices.Length == 0)
+            {
+                this.SelectedIndices.Clear();
             }
+            else if (indices.Length == 1)
+            {
+                this.SelectedIndices.Clear();
+                this.SelectedIndices.Add(indices[0]);
+            }
+            else
+            {
+                var currentSelectedIndices = this.SelectedIndices.Cast<int>().ToArray();
+                var selectIndices = indices.Except(currentSelectedIndices).ToArray();
+                var deselectIndices = currentSelectedIndices.Except(indices).ToArray();
 
-            this.OnSelectedIndexChanged(EventArgs.Empty);
+                if (selectIndices.Length + deselectIndices.Length > currentSelectedIndices.Length)
+                {
+                    // Clearして選択し直した方が早い場合
+                    this.SelectedIndices.Clear();
+                    selectIndices = indices;
+                    deselectIndices = Array.Empty<int>();
+                }
+
+                foreach (var index in selectIndices)
+                    NativeMethods.SelectItem(this, index, selected: true);
+
+                foreach (var index in deselectIndices)
+                    NativeMethods.SelectItem(this, index, selected: false);
+            }
         }
 
         public void SelectAllItems()
diff --git a/OpenTween/NativeMethods.cs b/OpenTween/NativeMethods.cs
index 209824ff6..6d972c62c 100644
--- a/OpenTween/NativeMethods.cs
+++ b/OpenTween/NativeMethods.cs
@@ -121,6 +121,7 @@ private struct LVITEM
         [Flags]
         private enum LVIS : uint
         {
+            None = 0,
             SELECTED = 0x02,
         }
 
@@ -130,13 +131,13 @@ private enum LVIS : uint
         /// <param name="listView">対象となる ListView</param>
         /// <param name="index">選択するアイテムのインデックス</param>
         /// <returns>成功した場合は true、それ以外の場合は false</returns>
-        public static bool SelectItem(ListView listView, int index)
+        public static bool SelectItem(ListView listView, int index, bool selected = true)
         {
             // LVM_SETITEMSTATE では stateMask, state 以外のメンバーは無視される
             var lvitem = new LVITEM
             {
                 stateMask = LVIS.SELECTED,
-                state = LVIS.SELECTED,
+                state = selected ? LVIS.SELECTED : LVIS.None,
             };
 
             var ret = (int)SendMessage(listView.Handle, SendMessageType.LVM_SETITEMSTATE, (IntPtr)index, ref lvitem);
diff --git a/OpenTween/Tween.cs b/OpenTween/Tween.cs
index 5dfc61982..024bccd0b 100644
--- a/OpenTween/Tween.cs
+++ b/OpenTween/Tween.cs
@@ -9598,11 +9598,6 @@ private void SelectListItem(DetailsListView LView , int[]? Index, int focusedInd
 
             if (Index != null)
             {
-                do
-                {
-                    LView.SelectedIndices.Clear();
-                }
-                while (LView.SelectedIndices.Count > 0);
                 LView.SelectItems(Index);
             }
             if (selectionMarkIndex > -1 && LView.VirtualListSize > selectionMarkIndex)