[Preview7/Release] Backport 13747 DarkMode: SystemControlButton rendering (#13748)

Fixes System Control Button rendering issues in dark mode, where a
control button is either rendering not in dark mode, or has rendering
artefacts when rendering in the context of the property grid.

These issues have been pointed out by customers, and are, among others,
one of the blockers for GitHub Extensions, which are emotionally
discussed on their GitHub issues


gitextensions/gitextensions#9191 (comment)

(and also might even save lives
gitextensions/gitextensions#11904)

Note while the latter is certainly an ironic-funny remark, those
discussions around dark mode for WinForms app shows the high
participation of the community and the desire to make this work, and
note also that other issues which have been pointed out in other
projects show us clearly, why we should accomodate rendering issues as
early as possible to unblock them: GitExtension in particular but also
other projects can provide their aspired .NET 10 based DarkMode-enabled
versions as soon as .NET 10 becomes available.

Fixes rendering issues in dark mode rendering, where a button is used in
the context of another control:

* DropDownArrow
* UpDown based controls
* Ellipse-Control in Property browsers

These buttons have not been rendered correctly in dark mode, and a new
system control button renderer (tested by CTI) fixes these issues.

Note that this PR does not change the Classic (Light Mode) code paths in
any way.

Examples:

<img width="230" height="60" alt="image"
src="https://github.com/user-attachments/assets/9bd4750b-076d-45cd-9160-997b50ff98ad"
/>

---

<img width="565" height="72" alt="image"
src="https://github.com/user-attachments/assets/26c4eba5-11cd-44ad-8964-bb3d586fee41"
/>

---

<img width="763" height="151" alt="image"
src="https://github.com/user-attachments/assets/ce4f409f-051b-422a-aa1f-26c5a8470e0f"
/>

---

Current versions have been tested by CTI and they also reassured that
the Classic mode CodePaths (LightMode rendering) remain unchanged to
minimize any risks.

###### Microsoft Reviewers: [Open in
CodeFlow](https://microsoft.github.io/open-pr/?codeflow=https://github.com/dotnet/winforms/pull/13748)

Author: KlausLoeffelmann

src/System.Windows.Forms/System/Windows/Forms/Controls/PropertyGrid/PropertyGridInternal/DropDownButton.cs

@@ -4,6 +4,7 @@
 using System.Drawing;
 using System.Windows.Forms.ButtonInternal;
 using System.Windows.Forms.VisualStyles;
+using static System.Windows.Forms.ControlPaint;
 
 namespace System.Windows.Forms.PropertyGridInternal;
 
@@ -17,7 +18,20 @@ public DropDownButton()
         SetAccessibleName();
     }
 
-    // When the holder is open, we don't fire clicks.
+    /// <summary>
+    ///  Indicates whether the control should be rendered in dark mode.
+    ///  Set this property if you use this class for a control in dark mode.
+    /// </summary>
+    public bool RequestDarkModeRendering { get; set; }
+
+    /// <summary>
+    ///  Gets or sets the style used for rendering the control button.
+    /// </summary>
+    public ModernControlButtonStyle ControlButtonStyle { get; set; }
+
+    /// <summary>
+    ///  Gets or sets a value indicating whether mouse events should be ignored when the holder is open.
+    /// </summary>
     public bool IgnoreMouse { get; set; }
 
     /// <summary>
@@ -64,52 +78,82 @@ protected override void OnMouseDown(MouseEventArgs e)
         }
     }
 
+#pragma warning disable WFO5001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
     protected override void OnPaint(PaintEventArgs pevent)
     {
-        base.OnPaint(pevent);
+        ComboBoxState state = ComboBoxState.Normal;
 
-#pragma warning disable WFO5001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
-        if (!Application.IsDarkModeEnabled
-            && (Application.RenderWithVisualStyles & _useComboBoxTheme))
+        if (MouseIsDown)
         {
-            ComboBoxState state = ComboBoxState.Normal;
-
-            if (MouseIsDown)
-            {
-                state = ComboBoxState.Pressed;
-            }
-            else if (MouseIsOver)
-            {
-                state = ComboBoxState.Hot;
-            }
+            state = ComboBoxState.Pressed;
+        }
+        else if (MouseIsOver)
+        {
+            state = ComboBoxState.Hot;
+        }
 
-            Rectangle dropDownButtonRect = new(0, 0, Width, Height);
-            if (state == ComboBoxState.Normal)
-            {
-                pevent.Graphics.FillRectangle(SystemBrushes.Window, dropDownButtonRect);
-            }
+        base.OnPaint(pevent);
 
-            using (DeviceContextHdcScope hdc = new(pevent))
+        if (Application.IsDarkModeEnabled && RequestDarkModeRendering)
+        {
+            ModernControlButtonState buttonState = state switch
             {
-                ComboBoxRenderer.DrawDropDownButtonForHandle(
-                    hdc,
-                    dropDownButtonRect,
-                    state,
-                    ScaleHelper.IsScalingRequirementMet ? HWNDInternal : HWND.Null);
-            }
+                ComboBoxState.Disabled => ModernControlButtonState.Disabled,
+                ComboBoxState.Hot => ModernControlButtonState.Hover,
+                ComboBoxState.Pressed => ModernControlButtonState.Pressed,
+                _ => ModernControlButtonState.Normal
+            };
+
+            DrawModernControlButton(
+                pevent.Graphics,
+                new Rectangle(0, 0, Width, Height),
+                ControlButtonStyle,
+                buttonState,
+                isDarkMode: true);
+
+            return;
+        }
 
-            // Redraw focus cues.
-            //
-            // For consistency with other PropertyGrid buttons, i.e. those opening system dialogs ("..."), that
-            // always show visual cues when focused, we need to do the same for this custom button, painted as
-            // a ComboBox control part (drop-down).
-            if (Focused)
-            {
-                dropDownButtonRect.Inflate(-1, -1);
-                ControlPaint.DrawFocusRectangle(pevent.Graphics, dropDownButtonRect, ForeColor, BackColor);
-            }
+        if (Application.RenderWithVisualStyles & _useComboBoxTheme)
+        {
+            RenderComboBoxButtonWithVisualStyles(pevent, state);
         }
+    }
 #pragma warning restore WFO5001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
+    private void RenderComboBoxButtonWithVisualStyles(PaintEventArgs pevent, ComboBoxState state)
+    {
+        Rectangle dropDownButtonRect = new(0, 0, Width, Height);
+
+        if (state == ComboBoxState.Normal)
+        {
+            pevent.Graphics.FillRectangle(
+                SystemBrushes.Window,
+                dropDownButtonRect);
+        }
+
+        using (DeviceContextHdcScope hdc = new(pevent))
+        {
+            ComboBoxRenderer.DrawDropDownButtonForHandle(
+                hdc,
+                dropDownButtonRect,
+                state,
+                ScaleHelper.IsScalingRequirementMet ? HWNDInternal : HWND.Null);
+        }
+
+        // Redraw focus cues.
+        //
+        // For consistency with other PropertyGrid buttons, i.e. those opening system dialogs ("..."), that
+        // always show visual cues when focused, we need to do the same for this custom button, painted as
+        // a ComboBox control part (drop-down).
+        if (Focused)
+        {
+            dropDownButtonRect.Inflate(-1, -1);
+            DrawFocusRectangle(
+                pevent.Graphics,
+                dropDownButtonRect,
+                ForeColor,
+                BackColor);
+        }
     }
 
     internal void PerformButtonClick()

src/System.Windows.Forms/System/Windows/Forms/Controls/PropertyGrid/PropertyGridInternal/PropertyGridView.cs

@@ -11,6 +11,7 @@
 using Microsoft.Win32;
 using Windows.Win32.System.Variant;
 using Windows.Win32.UI.Accessibility;
+using static System.Windows.Forms.ControlPaint;
 
 namespace System.Windows.Forms.PropertyGridInternal;
 
@@ -190,33 +191,44 @@ public bool CanUndo
     ///   the selected row's <see cref="GridEntry"/>.
     ///  </para>
     /// </remarks>
+#pragma warning disable WFO5001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
     internal DropDownButton DropDownButton
     {
         get
         {
-            if (_dropDownButton is null)
+            if (_dropDownButton is not null)
             {
-                OwnerGrid.CheckInCreate();
+                return _dropDownButton;
+            }
 
-                _dropDownButton = new()
-                {
-                    UseComboBoxTheme = true
-                };
+            OwnerGrid.CheckInCreate();
 
-                Bitmap bitmap = CreateResizedBitmap("Arrow", DownArrowIconWidth, DownArrowIconHeight);
-                _dropDownButton.Image = bitmap;
-                _dropDownButton.BackColor = SystemColors.Control;
-                _dropDownButton.ForeColor = SystemColors.ControlText;
-                _dropDownButton.Click += OnButtonClick;
-                _dropDownButton.GotFocus += OnDropDownButtonGotFocus;
-                _dropDownButton.LostFocus += OnChildLostFocus;
-                _dropDownButton.TabIndex = 2;
+            _dropDownButton = new()
+            {
+                UseComboBoxTheme = true,
+                RequestDarkModeRendering = Application.IsDarkModeEnabled,
+                ControlButtonStyle = ModernControlButtonStyle.OpenDropDown | ModernControlButtonStyle.RoundedBorder
+            };
 
-                CommonEditorSetup(_dropDownButton);
-                _dropDownButton.Size = ScaleHelper.IsScalingRequirementMet
-                    ? new(SystemInformation.VerticalScrollBarArrowHeightForDpi(DeviceDpiInternal), RowHeight)
-                    : new(SystemInformation.VerticalScrollBarArrowHeight, RowHeight);
-            }
+            Bitmap bitmap = CreateResizedBitmap(
+                "Arrow",
+                DownArrowIconWidth,
+                DownArrowIconHeight);
+
+            // For classic mode/backwards compatibility.
+            _dropDownButton.Image = bitmap;
+            _dropDownButton.BackColor = SystemColors.Control;
+            _dropDownButton.ForeColor = SystemColors.ControlText;
+            _dropDownButton.Click += OnButtonClick;
+            _dropDownButton.GotFocus += OnDropDownButtonGotFocus;
+            _dropDownButton.LostFocus += OnChildLostFocus;
+            _dropDownButton.TabIndex = 2;
+
+            CommonEditorSetup(_dropDownButton);
+
+            _dropDownButton.Size = ScaleHelper.IsScalingRequirementMet
+                ? new(SystemInformation.VerticalScrollBarArrowHeightForDpi(DeviceDpiInternal), RowHeight)
+                : new(SystemInformation.VerticalScrollBarArrowHeight, RowHeight);
 
             return _dropDownButton;
         }
@@ -235,32 +247,42 @@ internal Button DialogButton
     {
         get
         {
-            if (_dialogButton is null)
+            if (_dialogButton is not null)
             {
-                OwnerGrid.CheckInCreate();
+                return _dialogButton;
+            }
 
-                _dialogButton = new DropDownButton
-                {
-                    BackColor = SystemColors.Control,
-                    ForeColor = SystemColors.ControlText,
-                    TabIndex = 3,
-                    Image = CreateResizedBitmap("dotdotdot", DotDotDotIconWidth, DotDotDotIconHeight)
-                };
+            OwnerGrid.CheckInCreate();
 
-                _dialogButton.Click += OnButtonClick;
-                _dialogButton.KeyDown += OnButtonKeyDown;
-                _dialogButton.GotFocus += OnDropDownButtonGotFocus;
-                _dialogButton.LostFocus += OnChildLostFocus;
-                _dialogButton.Size = ScaleHelper.IsScalingRequirementMet
-                    ? new Size(SystemInformation.VerticalScrollBarArrowHeightForDpi(DeviceDpiInternal), RowHeight)
-                    : new Size(SystemInformation.VerticalScrollBarArrowHeight, RowHeight);
+            _dialogButton = new DropDownButton
+            {
+                RequestDarkModeRendering = Application.IsDarkModeEnabled,
+                ControlButtonStyle = ModernControlButtonStyle.Ellipse | ModernControlButtonStyle.RoundedBorder,
+                BackColor = SystemColors.Control,
+                ForeColor = SystemColors.ControlText,
+                TabIndex = 3,
 
-                CommonEditorSetup(_dialogButton);
-            }
+                // For classic mode/backwards compatibility.
+                Image = CreateResizedBitmap(
+                    "dotdotdot",
+                    DotDotDotIconWidth,
+                    DotDotDotIconHeight)
+            };
+
+            _dialogButton.Click += OnButtonClick;
+            _dialogButton.KeyDown += OnButtonKeyDown;
+            _dialogButton.GotFocus += OnDropDownButtonGotFocus;
+            _dialogButton.LostFocus += OnChildLostFocus;
+            _dialogButton.Size = ScaleHelper.IsScalingRequirementMet
+                ? new Size(SystemInformation.VerticalScrollBarArrowHeightForDpi(DeviceDpiInternal), RowHeight)
+                : new Size(SystemInformation.VerticalScrollBarArrowHeight, RowHeight);
+
+            CommonEditorSetup(_dialogButton);
 
             return _dialogButton;
         }
     }
+#pragma warning restore WFO5001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
 
     /// <summary>
     ///  The common text box for editing values.
@@ -269,30 +291,32 @@ private GridViewTextBox EditTextBox
     {
         get
         {
-            if (_editTextBox is null)
+            if (_editTextBox is not null)
             {
-                OwnerGrid.CheckInCreate();
+                return _editTextBox;
+            }
 
-                _editTextBox = new(this)
-                {
-                    BorderStyle = BorderStyle.None,
-                    AutoSize = false,
-                    TabStop = false,
-                    AcceptsReturn = true,
-                    BackColor = BackColor,
-                    ForeColor = ForeColor
-                };
+            OwnerGrid.CheckInCreate();
 
-                _editTextBox.KeyDown += OnEditKeyDown;
-                _editTextBox.KeyPress += OnEditKeyPress;
-                _editTextBox.GotFocus += OnEditGotFocus;
-                _editTextBox.LostFocus += OnEditLostFocus;
-                _editTextBox.MouseDown += OnEditMouseDown;
-                _editTextBox.TextChanged += OnEditChange;
+            _editTextBox = new(this)
+            {
+                BorderStyle = BorderStyle.None,
+                AutoSize = false,
+                TabStop = false,
+                AcceptsReturn = true,
+                BackColor = BackColor,
+                ForeColor = ForeColor
+            };
 
-                _editTextBox.TabIndex = 1;
-                CommonEditorSetup(_editTextBox);
-            }
+            _editTextBox.KeyDown += OnEditKeyDown;
+            _editTextBox.KeyPress += OnEditKeyPress;
+            _editTextBox.GotFocus += OnEditGotFocus;
+            _editTextBox.LostFocus += OnEditLostFocus;
+            _editTextBox.MouseDown += OnEditMouseDown;
+            _editTextBox.TextChanged += OnEditChange;
+
+            _editTextBox.TabIndex = 1;
+            CommonEditorSetup(_editTextBox);
 
             return _editTextBox;
         }
@@ -2210,7 +2234,7 @@ protected override void OnGotFocus(EventArgs e)
             if ((Size.Width > doubleOffset) && (Size.Height > doubleOffset))
             {
                 using Graphics g = CreateGraphicsInternal();
-                ControlPaint.DrawFocusRectangle(g, new Rectangle(_offset2Units, _offset2Units, Size.Width - doubleOffset, Size.Height - doubleOffset));
+                DrawFocusRectangle(g, new Rectangle(_offset2Units, _offset2Units, Size.Width - doubleOffset, Size.Height - doubleOffset));
             }
         }
     }