窗体显示和 WinForms 对齐：文本框、下拉框、列表框、日期选择默认白底黑字，不沿用父控件的颜色（项目 8 白字分组框里的文本框填了字看不见）；下拉框的背景色能显示、展开的列表跟着下拉框的颜色和字体；分组框、面板禁用时里面的控件也禁用（变灰、不响应操作，Enabled 读出 false 并触发 EnabledChanged）；禁用的控件设了颜色也画灰字；窗体、文本框等设透明背景色和 WinForms 一样报错，设计器里也不提供"透明"；多行文本框按 ScrollBars 显示滚动条；标签的边框和 TextAlign、窗体的 ControlBox、复选框的不确定状态能显示；设计器里 Enabled = false 的控件和 VS 一样照常显示

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

runtime/Sim.WinForms/Forms/Control.cs

@@ -11,7 +11,7 @@ namespace System.Windows.Forms;
 
 /// <summary>
 /// 仿真控件的基类。属性保存在本进程里；控件所在窗体显示后，属性变化以 patch 消息发给浏览器渲染。
-/// Font、BackColor、ForeColor 是"环境属性"：没有显式设置时沿用父控件的值，只把显式设置的值发给浏览器。
+/// Font、BackColor、ForeColor 是"环境属性"：没有显式设置时沿用父控件的值（文本框等的颜色除外，见 OwnBackColor），只把显式设置的值发给浏览器。
 /// </summary>
 public class Control : Component, IWin32Window
 {
@@ -178,24 +178,42 @@ public class Control : Component, IWin32Window
         }
     }
 
+    /// <summary>和 WinForms 一样：父控件（分组框、面板）禁用时子控件也是禁用的，读出 false、不响应操作；浏览器按同样的规则画成灰色</summary>
     public bool Enabled
     {
-        get => _enabled;
+        get => _enabled && (_parent?.Enabled ?? true);
         set
         {
-            if (SetProp(ref _enabled, value, nameof(Enabled))) OnEnabledChanged(EventArgs.Empty);
+            var old = Enabled;
+            SetProp(ref _enabled, value, nameof(Enabled));
+            if (Enabled != old) OnEnabledChanged(EventArgs.Empty);
         }
     }
 
+    /// <summary>
+    /// 没有显式设置时控件自己的颜色；null 表示沿用父控件。文本框、列表框、下拉框、日期选择是白底黑字（SystemColors.Window / WindowText），
+    /// 不沿用父控件：分组框设成白字时，里面的文本框还是黑字。
+    /// </summary>
+    private protected virtual Color? OwnBackColor => null;
+
+    private protected virtual Color? OwnForeColor => null;
+
+    /// <summary>能不能把 BackColor 设成透明（含半透明）：窗体、文本框、列表框、下拉框、日期选择、数据表格不行，和 WinForms 一样报错</summary>
+    private protected virtual bool SupportsTransparentBackColor => true;
+
     public virtual Color BackColor
     {
-        get => !_backColor.IsEmpty ? _backColor : _parent?.BackColor ?? DefaultBackColor;
-        set => SetProp(ref _backColor, value, nameof(BackColor));
+        get => !_backColor.IsEmpty ? _backColor : OwnBackColor ?? _parent?.BackColor ?? DefaultBackColor;
+        set
+        {
+            if (!value.IsEmpty && value.A < 255 && !SupportsTransparentBackColor) throw new ArgumentException("控件不支持透明的背景色。");
+            SetProp(ref _backColor, value, nameof(BackColor));
+        }
     }
 
     public virtual Color ForeColor
     {
-        get => !_foreColor.IsEmpty ? _foreColor : _parent?.ForeColor ?? DefaultForeColor;
+        get => !_foreColor.IsEmpty ? _foreColor : OwnForeColor ?? _parent?.ForeColor ?? DefaultForeColor;
         set => SetProp(ref _foreColor, value, nameof(ForeColor));
     }
 
@@ -302,7 +320,14 @@ public class Control : Component, IWin32Window
     protected virtual void OnMouseLeave(EventArgs e) => MouseLeave?.Invoke(this, e);
     protected virtual void OnTextChanged(EventArgs e) => TextChanged?.Invoke(this, e);
     protected virtual void OnVisibleChanged(EventArgs e) => VisibleChanged?.Invoke(this, e);
-    protected virtual void OnEnabledChanged(EventArgs e) => EnabledChanged?.Invoke(this, e);
+    protected virtual void OnEnabledChanged(EventArgs e)
+    {
+        EnabledChanged?.Invoke(this, e);
+        // 自己没被禁用的子控件实际状态也跟着变，同样触发 EnabledChanged（WinForms 的 OnParentEnabledChanged）
+        for (var i = 0; i < Controls.Count; i++)
+            if (Controls[i]._enabled) Controls[i].OnEnabledChanged(e);
+    }
+
     protected virtual void OnGotFocus(EventArgs e) => GotFocus?.Invoke(this, e);
     protected virtual void OnLostFocus(EventArgs e) => LostFocus?.Invoke(this, e);
     protected virtual void OnPaint(PaintEventArgs e) => Paint?.Invoke(this, e);

runtime/Sim.WinForms/Forms/DataGridView.cs

@@ -468,6 +468,8 @@ public class DataGridView : Control, ISupportInitialize
     private bool _initializing;
     private bool _rowsDirty;
 
+    private protected override bool SupportsTransparentBackColor => false;
+
     public DataGridView()
     {
         Columns = new DataGridViewColumnCollection(this);

runtime/Sim.WinForms/Forms/DateTimePicker.cs

@@ -22,6 +22,10 @@ public class DateTimePicker : Control
 
     protected override Size DefaultSize => new(200, 21);
 
+    private protected override Color? OwnBackColor => SystemColors.Window;
+    private protected override Color? OwnForeColor => SystemColors.WindowText;
+    private protected override bool SupportsTransparentBackColor => false;
+
     public DateTime Value
     {
         get => _value;

runtime/Sim.WinForms/Forms/Form.cs

@@ -23,6 +23,8 @@ public class Form : ContainerControl
     private bool _modal;
     private DialogResult _dialogResult;
 
+    private protected override bool SupportsTransparentBackColor => false;
+
     public Form()
     {
         base.Visible = false;

runtime/Sim.WinForms/Forms/ListControl.cs

@@ -1,5 +1,6 @@
 using System.Collections;
 using System.Collections.Generic;
+using System.Drawing;
 using System.Linq;
 
 namespace System.Windows.Forms;
@@ -10,6 +11,10 @@ public abstract class ListControl : Control
     /// <summary>选中项的序号。列表项增删时直接调整（和 WinForms 一样不触发 SelectedIndexChanged）</summary>
     private protected int SelectedIndexValue = -1;
 
+    private protected override Color? OwnBackColor => SystemColors.Window;
+    private protected override Color? OwnForeColor => SystemColors.WindowText;
+    private protected override bool SupportsTransparentBackColor => false;
+
     public abstract int SelectedIndex { get; set; }
 
     public string DisplayMember { get; set; } = "";

runtime/Sim.WinForms/Forms/TextBox.cs

@@ -10,6 +10,10 @@ public abstract class TextBoxBase : Control
     private bool _readOnly;
     private BorderStyle _borderStyle = BorderStyle.Fixed3D;
 
+    private protected override Color? OwnBackColor => _readOnly ? SystemColors.Control : SystemColors.Window;
+    private protected override Color? OwnForeColor => SystemColors.WindowText;
+    private protected override bool SupportsTransparentBackColor => false;
+
     public bool Multiline
     {
         get => _multiline;