Add Null static field to handles

microsoft · Aug 6, 2022 · 3515d52 · 3515d52
1 parent 39757ab
commit 3515d52
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Showing 2 changed files with 22 additions and 1 deletion.
diff --git a/src/Microsoft.Windows.CsWin32/Generator.cs b/src/Microsoft.Windows.CsWin32/Generator.cs
@@ -3885,6 +3885,12 @@ private IEnumerable<MemberDeclarationSyntax> CreateCommonTypeDefMembers(Identifi
         // If this typedef struct represents a pointer, add an IsNull property.
         if (fieldType is IdentifierNameSyntax { Identifier: { Value: nameof(IntPtr) or nameof(UIntPtr) } })
         {
+            // internal static readonly HWND Null;
+            yield return FieldDeclaration(VariableDeclaration(structName.WithTrailingTrivia(TriviaList(Space)))
+                .AddVariables(VariableDeclarator(IdentifierName("Null").Identifier)))
+                .AddModifiers(TokenWithSpace(SyntaxKind.InternalKeyword), TokenWithSpace(SyntaxKind.StaticKeyword), TokenWithSpace(SyntaxKind.ReadOnlyKeyword))
+                .WithSemicolonToken(SemicolonWithLineFeed);
+
             // internal static bool IsNull => value == default;
             yield return PropertyDeclaration(PredefinedType(TokenWithSpace(SyntaxKind.BoolKeyword)), "IsNull")
                 .AddModifiers(TokenWithSpace(this.Visibility))

diff --git a/test/Microsoft.Windows.CsWin32.Tests/GeneratorTests.cs b/test/Microsoft.Windows.CsWin32.Tests/GeneratorTests.cs
@@ -587,6 +587,17 @@ public void HandleStructsHaveIsNullProperty(string handleName)
         this.AssertGeneratedMember(handleName, "IsNull", "internal bool IsNull => Value == default;");
     }
 
+    [Theory]
+    [InlineData("HANDLE")]
+    [InlineData("HGDIOBJ")]
+    [InlineData("HINSTANCE")]
+    public void HandleStructsHaveStaticNullField(string handleName)
+    {
+        // A null HGDIOBJ has a specific meaning beyond just the concept of an invalid handle:
+        // https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-selectobject#return-value
+        this.AssertGeneratedMember(handleName, "Null", "Null");
+    }
+
     [Theory]
     [InlineData("HANDLE")]
     [InlineData("HGDIOBJ")]
@@ -598,7 +609,7 @@ public void HandleTypeDefsUseIntPtrAsFieldType(string handleType)
         this.CollectGeneratedCode(this.generator);
         this.AssertNoDiagnostics();
         StructDeclarationSyntax hwnd = Assert.IsType<StructDeclarationSyntax>(this.FindGeneratedType(handleType).Single());
-        FieldDeclarationSyntax field = hwnd.Members.OfType<FieldDeclarationSyntax>().Single();
+        FieldDeclarationSyntax field = hwnd.Members.OfType<FieldDeclarationSyntax>().First();
         Assert.Equal(nameof(IntPtr), Assert.IsType<IdentifierNameSyntax>(field.Declaration.Type).Identifier.ValueText);
     }
 
@@ -1969,6 +1980,7 @@ namespace Foundation
 		{
 			internal readonly IntPtr Value;
 			internal HWND(IntPtr value) => this.Value = value;
+			internal static readonly HWND Null;
 
 			internal bool IsNull => Value == default;
 			public static implicit operator IntPtr(HWND value) => value.Value;
@@ -2075,6 +2087,7 @@ namespace Graphics.Gdi
 		{
 			internal readonly IntPtr Value;
 			internal HDC(IntPtr value) => this.Value = value;
+			internal static readonly HDC Null;
 
 			internal bool IsNull => Value == default;
 			public static implicit operator IntPtr(HDC value) => value.Value;
@@ -2117,6 +2130,7 @@ namespace Foundation
 		{
 			internal readonly IntPtr Value;
 			internal HWND(IntPtr value) => this.Value = value;
+			internal static readonly HWND Null;
 
 			internal bool IsNull => Value == default;
 			public static implicit operator IntPtr(HWND value) => value.Value;
@@ -2458,6 +2472,7 @@ namespace Foundation
 		{
 			internal readonly IntPtr Value;
 			internal HANDLE(IntPtr value) => this.Value = value;
+			internal static readonly HANDLE Null;
 
 			internal bool IsNull => Value == default;
 			public static implicit operator IntPtr(HANDLE value) => value.Value;