From acfc47f018c3fde140658e621e43f1608b0b77a4 Mon Sep 17 00:00:00 2001
From: Patrick Simpson <p.simpson@etosis.com>
Date: Thu, 29 Jun 2017 13:37:55 +0200
Subject: [PATCH] Fixed keyboard handling in combo box

---
 .../AcaciaZPushPlugin/Controls/KComboBox.cs   | 110 +++++++-----------
 1 file changed, 43 insertions(+), 67 deletions(-)

diff --git a/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Controls/KComboBox.cs b/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Controls/KComboBox.cs
index 895a3db..38146fe 100644
--- a/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Controls/KComboBox.cs
+++ b/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Controls/KComboBox.cs
@@ -16,87 +16,49 @@ namespace Acacia.Controls
     {
         #region Drop-down list
 
+        /// <summary>
+        /// Custom list for the drop-down. Performs a few functions:
+        /// - Prevents grabbing the focus away from the edit when clicked
+        /// - Adds hover highlighting
+        /// - Only commits selection when clicked or externally (through enter in the edit).
+        ///   This prevents updating the text and associated filters when scrolling through the combo.
+        /// </summary>
         private class DropList : ListBox
         {
             private readonly KComboBox _owner;
-            private int _highlightIndex = -1;
+            private int _committedIndex = -1;
 
             public DropList(KComboBox owner)
             {
                 this._owner = owner;
                 SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
-                DrawMode = DrawMode.OwnerDrawFixed;
                 SetStyle(ControlStyles.Selectable, false);
                 BorderStyle = BorderStyle.None;
             }
 
             protected override void OnMouseMove(MouseEventArgs e)
             {
-                // Use the mouse to highlight the current item
-                int newIndex = IndexFromPoint(PointToClient(Cursor.Position));
-                if (newIndex != _highlightIndex)
-                {
-                    int oldIndex = _highlightIndex;
-                    _highlightIndex = newIndex;
-
-                    // Invalidate the affected items, which may include a previously selected one
-                    InvalidateItem(oldIndex);
-                    InvalidateItem(_highlightIndex);
-                    if (SelectedIndex != oldIndex && SelectedIndex != _highlightIndex)
-                        InvalidateItem(SelectedIndex);
-                }
+                // Perform the select to highlight
+                SelectedIndex = IndexFromPoint(PointToClient(Cursor.Position));
             }
 
             protected override void OnMouseLeave(EventArgs e)
             {
                 base.OnMouseLeave(e);
-                _highlightIndex = -1;
-            }
-
-            protected override void OnMouseDown(MouseEventArgs e)
-            {
-                base.OnMouseDown(e);
-
-                // Perform the select when the mouse is clicked
-                SelectedIndex = IndexFromPoint(PointToClient(Cursor.Position));
+                SelectedIndex = _committedIndex;
             }
 
             protected override void OnVisibleChanged(EventArgs e)
             {
                 base.OnVisibleChanged(e);
-                _highlightIndex = -1;
+                SelectedIndex = _committedIndex;
             }
 
-            private void InvalidateItem(int index)
+            protected override void OnMouseDown(MouseEventArgs e)
             {
-                if (index < 0 || index >= Items.Count)
-                    return;
-                Invalidate(GetItemRectangle(index));
-            }
-
-            protected override void OnDrawItem(DrawItemEventArgs e)
-            {
-                // Create a custom event instance to be able to set the selected state for mouse hover
-                DrawItemState state = e.State;
-                if (_highlightIndex >= 0)
-                {
-                    state = _highlightIndex == e.Index ? DrawItemState.Selected : DrawItemState.None;
-                }
-                DrawItemEventArgs draw = new DrawItemEventArgs(e.Graphics, e.Font, e.Bounds, e.Index, state);
-                draw.DrawBackground();
-
-                string text = Items[draw.Index].ToString();
-                using (StringFormat format = new StringFormat())
-                {
-                    format.LineAlignment = StringAlignment.Center;
-                    using (Brush brush = new SolidBrush(draw.ForeColor))
-                    {
-                        draw.Graphics.DrawString(text,
-                            draw.Font, brush,
-                            draw.Bounds,
-                            format);
-                    }
-                }
+                // Select the item under the mouse and commit
+                SelectedIndex = IndexFromPoint(PointToClient(Cursor.Position));
+                CommitSelection();
             }
 
             protected override void DefWndProc(ref Message m)
@@ -117,12 +79,22 @@ namespace Acacia.Controls
                 Size prefSize = base.GetPreferredSize(proposedSize);
                 return new Size(prefSize.Width, ItemHeight * Math.Min(Items.Count, _owner.MaxDropDownItems));
             }
+
+            public void CommitSelection()
+            {
+                _committedIndex = SelectedIndex;
+                base.OnSelectedIndexChanged(new EventArgs());
+            }
+
+            protected override void OnSelectedIndexChanged(EventArgs e)
+            {
+                // Don't notify until committed
+            }
         }
 
         #endregion
 
         private readonly DropList _list;
-        private int _ignoreListEvents;
 
         #region Items properties
 
@@ -162,10 +134,14 @@ namespace Acacia.Controls
 
         private void _list_SelectedIndexChanged(object sender, EventArgs e)
         {
-            if (_list.SelectedIndex >= 0 && _ignoreListEvents == 0)
+            if (_list.SelectedIndex >= 0)
             {
                 Text = _list.SelectedItem.ToString();
             }
+            else
+            {
+                Text = "";
+            }
         }
 
         public void BeginUpdate()
@@ -188,16 +164,8 @@ namespace Acacia.Controls
             set
             {
                 _list.BindingContext = new BindingContext();
-                ++_ignoreListEvents;
-                try
-                {
-                    _list.DataSource = value;
-                    _list.SelectedIndex = -1;
-                }
-                finally
-                {
-                    --_ignoreListEvents;
-                }
+                _list.DataSource = value;
+                _list.SelectedIndex = -1;
             }
         }
 
@@ -219,7 +187,15 @@ namespace Acacia.Controls
                 case Keys.Down:
                 case Keys.Up:
                     User32.SendMessage(_list.Handle, (int)WM.KEYDOWN, new IntPtr((int)e.KeyCode), IntPtr.Zero);
-                    e.IsInputKey = false;
+                    e.IsInputKey = true;
+                    break;
+
+                // Enter commits the selected index and closes the drop down
+                case Keys.Enter:
+                case Keys.Tab:
+                    _list.CommitSelection();
+                    DroppedDown = false;
+                    e.IsInputKey = e.KeyCode == Keys.Enter;
                     break;
                 default:
                     base.OnPreviewKeyDown(e);