Enable nullability in ToolStripPanelRenderEventArgs (#6422)

Author: gpetrou

src/System.Windows.Forms/src/PublicAPI.Shipped.txt

@@ -2927,9 +2927,9 @@ System.Windows.Forms.ToolStripItemTextRenderEventArgs.ToolStripItemTextRenderEve
 ~System.Windows.Forms.ToolStripPanel.ToolStripPanelRowCollection.Remove(System.Windows.Forms.ToolStripPanelRow value) -> void
 ~System.Windows.Forms.ToolStripPanel.ToolStripPanelRowCollection.ToolStripPanelRowCollection(System.Windows.Forms.ToolStripPanel owner) -> void
 ~System.Windows.Forms.ToolStripPanel.ToolStripPanelRowCollection.ToolStripPanelRowCollection(System.Windows.Forms.ToolStripPanel owner, System.Windows.Forms.ToolStripPanelRow[] value) -> void
-~System.Windows.Forms.ToolStripPanelRenderEventArgs.Graphics.get -> System.Drawing.Graphics
-~System.Windows.Forms.ToolStripPanelRenderEventArgs.ToolStripPanel.get -> System.Windows.Forms.ToolStripPanel
-~System.Windows.Forms.ToolStripPanelRenderEventArgs.ToolStripPanelRenderEventArgs(System.Drawing.Graphics g, System.Windows.Forms.ToolStripPanel toolStripPanel) -> void
+System.Windows.Forms.ToolStripPanelRenderEventArgs.Graphics.get -> System.Drawing.Graphics!
+System.Windows.Forms.ToolStripPanelRenderEventArgs.ToolStripPanel.get -> System.Windows.Forms.ToolStripPanel!
+System.Windows.Forms.ToolStripPanelRenderEventArgs.ToolStripPanelRenderEventArgs(System.Drawing.Graphics! g, System.Windows.Forms.ToolStripPanel! toolStripPanel) -> void
 ~System.Windows.Forms.ToolStripPanelRow.CanMove(System.Windows.Forms.ToolStrip toolStripToDrag) -> bool
 ~System.Windows.Forms.ToolStripPanelRow.Controls.get -> System.Windows.Forms.Control[]
 ~System.Windows.Forms.ToolStripPanelRow.LayoutEngine.get -> System.Windows.Forms.Layout.LayoutEngine

src/System.Windows.Forms/src/System/Windows/Forms/ToolStripPanelRenderEventArgs.cs

@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-#nullable disable
-
 using System.Drawing;
 
 namespace System.Windows.Forms
@@ -15,8 +13,8 @@ public class ToolStripPanelRenderEventArgs : EventArgs
         /// </summary>
         public ToolStripPanelRenderEventArgs(Graphics g, ToolStripPanel toolStripPanel)
         {
-            Graphics = g;
-            ToolStripPanel = toolStripPanel;
+            Graphics = g.OrThrowIfNull();
+            ToolStripPanel = toolStripPanel.OrThrowIfNull();
         }
 
         /// <summary>

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/ToolStripPanelRenderEventArgsTests.cs

@@ -9,22 +9,32 @@ namespace System.Windows.Forms.Tests
 {
     public class ToolStripPanelRenderEventArgsTests : IClassFixture<ThreadExceptionFixture>
     {
-        public static IEnumerable<object[]> Ctor_Graphics_ToolStripPanel_TestData()
+        public static IEnumerable<object[]> Ctor_Null_Graphics_ToolStripPanel_TestData()
         {
             var image = new Bitmap(10, 10);
             Graphics graphics = Graphics.FromImage(image);
 
             yield return new object[] { null, null };
-            yield return new object[] { graphics, new ToolStripPanel() };
+            yield return new object[] { graphics, null };
+            yield return new object[] { null, new ToolStripPanel() };
         }
 
         [WinFormsTheory]
-        [MemberData(nameof(Ctor_Graphics_ToolStripPanel_TestData))]
-        public void Ctor_Graphics_ToolStripPanel(Graphics g, ToolStripPanel panel)
+        [MemberData(nameof(Ctor_Null_Graphics_ToolStripPanel_TestData))]
+        public void ToolStripPanelRenderEventArgs_Null_Graphics_ToolStripPanel_ThrowsArgumentNullException(Graphics g, ToolStripPanel toolStripPanel)
         {
-            var e = new ToolStripPanelRenderEventArgs(g, panel);
-            Assert.Equal(g, e.Graphics);
-            Assert.Equal(panel, e.ToolStripPanel);
+            Assert.Throws<ArgumentNullException>(() => new ToolStripPanelRenderEventArgs(g, toolStripPanel));
+        }
+
+        [WinFormsFact]
+        public void Ctor_Graphics_ToolStripPanel()
+        {
+            using var image = new Bitmap(10, 10);
+            using Graphics graphics = Graphics.FromImage(image);
+            using var toolStripPanel = new ToolStripPanel();
+            var e = new ToolStripPanelRenderEventArgs(graphics, toolStripPanel);
+            Assert.Equal(graphics, e.Graphics);
+            Assert.Equal(toolStripPanel, e.ToolStripPanel);
             Assert.False(e.Handled);
         }
 

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/ToolStripRendererTests.cs

@@ -601,11 +601,9 @@ public void ToolStripRenderer_DrawToolStripContentPanelBackground_Invoke_CallsRe
         public static IEnumerable<object[]> ToolStripPanelRenderEventArgs_TestData()
         {
             yield return new object[] { null };
-            yield return new object[] { new ToolStripPanelRenderEventArgs(null, null) };
 
             var image = new Bitmap(10, 10);
             Graphics graphics = Graphics.FromImage(image);
-            yield return new object[] { new ToolStripPanelRenderEventArgs(graphics, null) };
             yield return new object[] { new ToolStripPanelRenderEventArgs(graphics, new ToolStripPanel()) };
         }