From 640fb5ec1bfcab76fe77bbd06e41ff656daaca9e Mon Sep 17 00:00:00 2001
From: AtomCrafty <atomcrafty@frucost.net>
Date: Wed, 5 Jul 2023 20:12:59 +0200
Subject: [PATCH 1/3] add AutoCompleteBox with MinimumPrefixLength=0 to control
 gallery

---
 samples/ControlCatalog/Pages/AutoCompleteBoxPage.xaml | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/samples/ControlCatalog/Pages/AutoCompleteBoxPage.xaml b/samples/ControlCatalog/Pages/AutoCompleteBoxPage.xaml
index a492808f1d..b682ebf51d 100644
--- a/samples/ControlCatalog/Pages/AutoCompleteBoxPage.xaml
+++ b/samples/ControlCatalog/Pages/AutoCompleteBoxPage.xaml
@@ -18,6 +18,10 @@
           <Setter Property="Margin" Value="8" />
         </Style>
       </UniformGrid.Styles>
+      <StackPanel>
+        <TextBlock Text="MinimumPrefixLength: 0" />
+        <AutoCompleteBox MinimumPrefixLength="0" />
+      </StackPanel>
       <StackPanel>
         <TextBlock Text="MinimumPrefixLength: 1" />
         <AutoCompleteBox MinimumPrefixLength="1" />
@@ -42,7 +46,6 @@
         <TextBlock Text="Disabled" />
         <AutoCompleteBox IsEnabled="False" />
       </StackPanel>
-
       <StackPanel>
         <TextBlock Text="ValueMemberBinding" />
         <AutoCompleteBox ValueMemberBinding="{Binding Capital, x:DataType=models:StateData}" />

From 4b5b6225f1124dfdaedb2b1cb18c997cfe0d8a4c Mon Sep 17 00:00:00 2001
From: AtomCrafty <atomcrafty@frucost.net>
Date: Wed, 5 Jul 2023 20:13:54 +0200
Subject: [PATCH 2/3] fix AutoCompleteBox dropdown not opening when the text
 box is empty

---
 .../AutoCompleteBox/AutoCompleteBox.cs                | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs b/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs
index d0b894101f..ebf66164b7 100644
--- a/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs
+++ b/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs
@@ -1320,17 +1320,14 @@ namespace Avalonia.Controls
             // Evaluate the conditions needed for completion.
             // 1. Minimum prefix length
             // 2. If a delay timer is in use, use it
-            bool populateReady = newText.Length >= MinimumPrefixLength && MinimumPrefixLength >= 0;
-            if (populateReady && MinimumPrefixLength == 0 && String.IsNullOrEmpty(newText) && String.IsNullOrEmpty(SearchText))
-            {
-                populateReady = false;
-            }
-            _userCalledPopulate = populateReady ? userInitiated : false;
+            bool minimumLengthReached = newText.Length >= MinimumPrefixLength && MinimumPrefixLength >= 0;
+
+            _userCalledPopulate = minimumLengthReached && userInitiated;
 
             // Update the interface and values only as necessary
             UpdateTextValue(newText, userInitiated);
 
-            if (populateReady)
+            if (minimumLengthReached)
             {
                 _ignoreTextSelectionChange = true;
 

From 42ad2fd46e4409874db5235efc1e838c0475f6b1 Mon Sep 17 00:00:00 2001
From: AtomCrafty <atomcrafty@frucost.net>
Date: Wed, 5 Jul 2023 20:59:18 +0200
Subject: [PATCH 3/3] add regression test for AutoCompleteBox with
 MinimumPrefixLegth=0

---
 .../AutoCompleteBoxTests.cs                   | 37 ++++++++++++++-----
 1 file changed, 27 insertions(+), 10 deletions(-)

diff --git a/tests/Avalonia.Controls.UnitTests/AutoCompleteBoxTests.cs b/tests/Avalonia.Controls.UnitTests/AutoCompleteBoxTests.cs
index acae583b5c..f31df71c0d 100644
--- a/tests/Avalonia.Controls.UnitTests/AutoCompleteBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/AutoCompleteBoxTests.cs
@@ -1,21 +1,15 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
-using System.ComponentModel;
 using System.Linq;
 using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Templates;
 using Avalonia.Data;
-using Avalonia.Markup.Data;
-using Avalonia.Platform;
 using Avalonia.Threading;
 using Avalonia.UnitTests;
-using Moq;
 using Xunit;
 using System.Collections.ObjectModel;
-using System.Reactive.Linq;
 using System.Reactive.Subjects;
+using Avalonia.Input;
 
 namespace Avalonia.Controls.UnitTests
 {
@@ -439,6 +433,29 @@ namespace Avalonia.Controls.UnitTests
             });
         }
 
+        [Fact]
+        public void Explicit_Dropdown_Open_Request_MinimumPrefixLength_0()
+        {
+            RunTest((control, textbox) =>
+            {
+                control.Text = "";
+                control.MinimumPrefixLength = 0;
+                Dispatcher.UIThread.RunJobs();
+
+                Assert.False(control.IsDropDownOpen);
+
+                control.RaiseEvent(new KeyEventArgs
+                {
+                    RoutedEvent = InputElement.KeyDownEvent,
+                    Key = Key.Down
+                });
+
+                Dispatcher.UIThread.RunJobs();
+
+                Assert.True(control.IsDropDownOpen);
+            });
+        }
+
         /// <summary>
         /// Retrieves a defined predicate filter through a new AutoCompleteBox 
         /// control instance.
@@ -1072,14 +1089,14 @@ namespace Avalonia.Controls.UnitTests
 
         private AutoCompleteBox CreateControl()
         {
-            var datePicker =
+            var autoCompleteBox =
                 new AutoCompleteBox
                 {
                     Template = CreateTemplate()
                 };
 
-            datePicker.ApplyTemplate();
-            return datePicker;
+            autoCompleteBox.ApplyTemplate();
+            return autoCompleteBox;
         }
         private TextBox GetTextBox(AutoCompleteBox control)
         {