* White bar is shown in a KryptonForm Sizable without buttons and text

Documents/Changelog/Changelog.md

@@ -4,6 +4,7 @@
 
 ## 2026-11-xx - Build 2611 (V110 Nightly) - November 2026
 
+* Resolved [#2914](https://github.com/Krypton-Suite/Standard-Toolkit/issues/2914), White bar is shown in a `KryptonForm` Sizable without buttons and text
 * Resolved [#2862](https://github.com/Krypton-Suite/Standard-Toolkit/issues/2862), Form border resize flicker
 * Implemented [#595](https://github.com/Krypton-Suite/Standard-Toolkit/issues/595), Detachable Ribbons - Added ability to detach `KryptonRibbon` into a floating window with `AllowDetach` property, `Detach()` and `Reattach()` methods, and `RibbonDetached`/`RibbonReattached` events. See [Detachable Ribbons Documentation](Detachable-Ribbons-Feature.md) for comprehensive details.
 * Implemented [#2898](https://github.com/Krypton-Suite/Standard-Toolkit/issues/2898), `KryptonHScrollBar` & `KryptonVScrollBar` - Part of #2658

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

@@ -2193,6 +2193,38 @@ protected override bool WindowChromeLeftMouseDown(Point windowPoint)
         return ret;
     }
 
+    /// <inheritdoc />
+    protected override bool OnWM_NCCALCSIZE(ref Message m)
+    {
+        // Does the LParam contain a RECT or an NCCALCSIZE_PARAMS
+        if (m.WParam != IntPtr.Zero)
+        {
+            // Get the border sizing needed around the client area
+            Padding borders = RealWindowBorders;
+
+            // If caption should be hidden, set top border to 0 to prevent white band
+            if (ShouldHideCaption())
+            {
+                borders = new Padding(borders.Left, 0, borders.Right, borders.Bottom);
+            }
+
+            // Extract the Win32 NCCALCSIZE_PARAMS structure from LPARAM
+            PI.NCCALCSIZE_PARAMS calcsize = (PI.NCCALCSIZE_PARAMS)m.GetLParam(typeof(PI.NCCALCSIZE_PARAMS))!;
+
+            // Reduce provided RECT by the borders
+            calcsize.rectProposed.left += borders.Left;
+            calcsize.rectProposed.top += borders.Top;
+            calcsize.rectProposed.right -= borders.Right;
+            calcsize.rectProposed.bottom -= borders.Bottom;
+
+            // Put back the modified structure
+            Marshal.StructureToPtr(calcsize, m.LParam, false);
+        }
+
+        // Message processed, do not pass onto base class for processing
+        return true;
+    }
+
     protected override void OnMove(EventArgs e)
     {
         base.OnMove(e);
@@ -2260,6 +2292,30 @@ private void OnFormBorderStyleChanged()
         return null;
     }
 
+    /// <summary>
+    /// Determines if the caption area should be hidden (no text, no icon, no control box, no visible buttons).
+    /// </summary>
+    /// <returns>True if caption should be hidden; otherwise false.</returns>
+    private bool ShouldHideCaption()
+    {
+        // Check if there are any visible buttons
+        bool hasVisibleButtons = false;
+        foreach (ButtonSpecView bsv in _buttonManager.ButtonSpecViews)
+        {
+            if (bsv.ViewCenter.Visible && bsv.ViewButton.Enabled)
+            {
+                hasVisibleButtons = true;
+                break;
+            }
+        }
+
+        // Hide caption if no control box, no text, no icon, and no visible buttons
+        return !ControlBox
+               && string.IsNullOrEmpty(GetShortText())
+               && GetDefinedIcon() == null
+               && !hasVisibleButtons;
+    }
+
     private void SetHeaderStyle(ViewDrawDocker drawDocker,
         PaletteTripleMetricRedirect palette,
         HeaderStyle style)
@@ -2369,15 +2425,29 @@ private bool CheckViewLayout()
                 }
 
                 // Update the heading to enforce a fixed Material-like caption height when Material renderer is active
-                if (Renderer is RenderMaterial)
+                bool shouldHideCaption = ShouldHideCaption();
+
+                if (shouldHideCaption)
                 {
-                    const int materialCaptionHeight = 44; // px
-                    _headingFixedSize.FixedSize = new Size(materialCaptionHeight, materialCaptionHeight);
+                    // Hide the caption area when there's nothing to display
+                    _headingFixedSize.FixedSize = Size.Empty;
+                    _headingFixedSize.Visible = false;
                 }
                 else
                 {
-                    Padding windowBorders = RealWindowBorders;
-                    _headingFixedSize.FixedSize = new Size(windowBorders.Top, windowBorders.Top);
+                    // Ensure the heading is visible
+                    _headingFixedSize.Visible = true;
+
+                    if (Renderer is RenderMaterial)
+                    {
+                        const int materialCaptionHeight = 44; // px
+                        _headingFixedSize.FixedSize = new Size(materialCaptionHeight, materialCaptionHeight);
+                    }
+                    else
+                    {
+                        Padding windowBorders = RealWindowBorders;
+                        _headingFixedSize.FixedSize = new Size(windowBorders.Top, windowBorders.Top);
+                    }
                 }
 
                 // A change in window state since last time requires a layout

Source/Krypton Components/TestForm/Bug2914Test.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Data;
+using System.Drawing;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Forms;
+
+namespace TestForm;
+
+public partial class Bug2914Test : KryptonForm
+{
+    public Bug2914Test()
+    {
+        InitializeComponent();
+    }
+}

Source/Krypton Components/TestForm/Bug2914Test.resx

@@ -0,0 +1,120 @@
+<?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>
+</root>

Source/Krypton Components/TestForm/StartScreen.cs

@@ -61,6 +61,7 @@ private void AddButtons()
         CreateButton("Accessibility Test (UIA Providers)", "Comprehensive demo and test for UIA Provider implementation (Issue #762). Tests all 10 controls with accessibility support, organized by category with detailed results.", typeof(AccessibilityTest));
         CreateButton("Badge Test", "Comprehensive badge functionality demonstration for KryptonButton and KryptonCheckButton.", typeof(ButtonBadgeTest));
         CreateButton("Buttons Test", "All the buttons you want to test.", typeof(ButtonsTest));
+        CreateButton("Bug 2914 Test", "Tests the fix for 2914.", typeof(Bug2914Test));
         CreateButton("BugReportingTool", "Easily report bugs with this tool.", typeof(BugReportingDialogTest));
         CreateButton("Code Editor", "Native code editor with syntax highlighting, line numbering, code folding, and auto-completion.", typeof(CodeEditorTest));
         CreateButton("Countdown Button", "Comprehensive demonstration of KryptonCountdownButton features with customizable duration, format, and enable-at-zero options.", typeof(CountdownButtonTest));