* Small square rendered next to Close button on KryptonForm when usin…

Documents/Changelog/Changelog.md

@@ -45,6 +45,7 @@
 
 ## 2026-11-xx - Build 2611 (V110 Nightly) - November 2026
 
+* Resolved [#3183](https://github.com/Krypton-Suite/Standard-Toolkit/issues/3183), Small square rendered next to Close button on KryptonForm when using a custom theme
 * Resolved [#3225](https://github.com/Krypton-Suite/Standard-Toolkit/issues/3225), Ribbon large button image-to-text separator not DPI-scaled
 * Resolved [#3256](https://github.com/Krypton-Suite/Standard-Toolkit/issues/3256), Tree View Event is Crashing
 * Resolved [#3249](https://github.com/Krypton-Suite/Standard-Toolkit/issues/3249), `KryptonForm` shows an extra border on the secondary monitor when maximized

Source/Krypton Components/Krypton.Toolkit/Controls Toolkit/KryptonCustomPaletteBase.cs

@@ -3124,6 +3124,20 @@ private void ImportFromXmlDocument([DisallowNull] XmlDocument doc)
                 SetPaletteName(root.GetAttribute("Name"));
             }
 
+            // Import order: establish a full baseline from BasePalette, then apply the XML theme on top.
+            //
+            // PopulateFromBaseOperation resets the palette hierarchy and copies values from the current
+            // BasePalette (via each storage type's PopulateFromBase). That ensures every property that the
+            // theme file does NOT serialize still reflects inheritance from the base theme instead of
+            // leftover C# defaults or stale state from a previous load—avoiding gaps in metrics, button
+            // specs, header chrome, etc. (e.g. stray rendering next to caption buttons).
+            //
+            // The steps below (ImportImagesFromElement / ImportObjectFromElement) then overwrite only what
+            // the XML actually defines. Theme wins for anything present in the file; anything omitted keeps
+            // the values we just populated from BasePalette. Doing populate after import would fight the
+            // file and could reset explicit theme settings, so populate must run first.
+            PopulateFromBaseOperation(null);
+
             // Grab the properties and images elements
             var props = root.SelectSingleNode(nameof(Properties)) as XmlElement;
             var images = root.SelectSingleNode(nameof(Images)) as XmlElement;

Source/Krypton Components/TestForm/Bug3183SmallSquareRenderedNextToClose.cs

@@ -0,0 +1,70 @@
+#region BSD License
+/*
+ *
+ *  New BSD 3-Clause License (https://github.com/Krypton-Suite/Standard-Toolkit/blob/master/LICENSE)
+ *  Modifications by Peter Wagner (aka Wagnerp) & Simon Coghlan (aka Smurf-IV), et al. 2026 - 2026. All rights reserved.
+ *
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Data;
+using System.Drawing;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Forms;
+
+using TestForm.Properties;
+
+namespace TestForm
+{
+    /// <summary>
+    /// Manual repro harness for GitHub issue #3183: a small square or wrong caption glyph next to the
+    /// <see cref="KryptonForm"/> Close (and related) buttons when a custom XML palette is applied.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// The embedded resource <c>Microsoft365_Super_Pink</c> matches the theme attached to the issue.
+    /// Run the form, then click <b>Apply Pink Theme</b> and inspect the top-right caption buttons
+    /// (especially when maximized vs normal).
+    /// </para>
+    /// <para>
+    /// The form starts maximized to mirror the original reporter’s sample and to exercise maximize /
+    /// restore button-spec state.
+    /// </para>
+    /// </remarks>
+    public partial class Bug3183SmallSquareRenderedNextToClose : KryptonForm
+    {
+        public Bug3183SmallSquareRenderedNextToClose()
+        {
+            InitializeComponent();
+        }
+
+        /// <summary>
+        /// No startup theme load: compare default chrome first, then apply the custom palette from the button.
+        /// </summary>
+        private void Bug3183SmallSquareRenderedNextToClose_Load(object sender, EventArgs e)
+        {
+        }
+
+        /// <summary>
+        /// Loads the embedded pink theme and switches the global palette to Custom so this form’s caption
+        /// uses the same path as real apps (<see cref="KryptonManager.GlobalCustomPalette"/>).
+        /// </summary>
+        private void kryptonButton1_Click(object sender, EventArgs e)
+        {
+            // Theme XML is stored as a string resource so the repro has no dependency on disk paths.
+            byte[] contentFile = Encoding.UTF8.GetBytes(Properties.Resources.Microsoft365_Super_Pink);
+
+            KryptonCustomPaletteBase customPaletteBase = new KryptonCustomPaletteBase();
+            customPaletteBase.ImportWithUpgrade(new MemoryStream(contentFile));
+
+            this.kryptonManager1.GlobalCustomPalette = customPaletteBase;
+            this.kryptonManager1.GlobalPaletteMode = PaletteMode.Custom;
+        }
+    }
+}

Source/Krypton Components/TestForm/Bug3183SmallSquareRenderedNextToClose.resx

@@ -0,0 +1,123 @@
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!-- 
+    Microsoft ResX Schema 
+
+    Version 2.0
+
+    The primary goals of this format is to allow a simple XML format 
+    that is mostly human readable. The generation and parsing of the 
+    various data types are done through the TypeConverter classes 
+    associated with the data types.
+
+    Example:
+
+    ... ado.net/XML headers & schema ...
+    <resheader name="resmimetype">text/microsoft-resx</resheader>
+    <resheader name="version">2.0</resheader>
+    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
+    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
+    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
+        <value>[base64 mime encoded serialized .NET Framework object]</value>
+    </data>
+    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
+        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
+        <comment>This is a comment</comment>
+    </data>
+
+    There are any number of "resheader" rows that contain simple 
+    name/value pairs.
+
+    Each data row contains a name, and value. The row also contains a 
+    type or mimetype. Type corresponds to a .NET class that support 
+    text/value conversion through the TypeConverter architecture. 
+    Classes that don't support this are serialized and stored with the 
+    mimetype set.
+
+    The mimetype is used for serialized objects, and tells the 
+    ResXResourceReader how to depersist the object. This is currently not 
+    extensible. For a given mimetype the value must be set accordingly:
+
+    Note - application/x-microsoft.net.object.binary.base64 is the format 
+    that the ResXResourceWriter will generate, however the reader can 
+    read any of the formats listed below.
+
+    mimetype: application/x-microsoft.net.object.binary.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.soap.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.bytearray.base64
+    value   : The object must be serialized into a byte array 
+            : using a System.ComponentModel.TypeConverter
+            : and then encoded with base64 encoding.
+    -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <metadata name="kryptonManager1.TrayLocation" type="System.Drawing.Point, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a">
+    <value>17, 17</value>
+  </metadata>
+</root>

Source/Krypton Components/TestForm/Properties/Resources.resx

@@ -946,4 +946,7 @@
   <data name="delete" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\delete.png;System.Drawing.Bitmap, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
+  <data name="Microsoft365_Super_Pink" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\Microsoft365 Super Pink.xml;System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089;Windows-1252</value>
+  </data>
 </root>