Add HtmlRenderer.Test project, port applicable tests from PeachPDF

PeachPDF forked from HTML-Renderer and has since built out a much
larger CSS engine, SVG support, and PDF pipeline, with a large xUnit
test suite covering it. This adds a new HtmlRenderer.Test project
(MSTest, matching this repo's existing test style) and ports the
subset of PeachPDF.Tests that HTML-Renderer's current feature set can
actually exercise, routing tests to the appropriate project:

- HtmlRenderer.Test: CSS parsing/property and Core Dom/Utils unit
  tests, using a new lightweight mock RAdapter/RGraphics test harness
  (no dependency on any UI framework).
- HtmlRenderer.IntegrationTest: end-to-end layout/paint behavior
  tests, using a similar harness backed by the real WinForms adapter.
- HtmlRenderer.PdfSharp.Test: PDF-generation and PdfSharp-adapter
  tests.

Of the ~483 candidate test files, the large majority test PeachPDF
features HTML-Renderer doesn't have at all (its own CSS engine, SVG,
flexbox/grid, shadows/gradients, WOFF fonts, bidi text shaping, etc.)
and were left out. Where a ported test exercises a feature that does
exist in HTML-Renderer but whose current implementation isn't spec
compliant, the test is still ported (full assertions intact, so it
documents the real target behavior) but marked
[Ignore("not yet spec compliant")] rather than dropped or forced to
pass.

InternalsVisibleTo grants were added to HtmlRenderer/HtmlRenderer.WinForms/
HtmlRenderer.PdfSharp for their respective test projects, matching the
same grants PeachPDF's own csproj already declares for PeachPDF.Tests.

More tests will be ported incrementally from PeachPDF as HTML-Renderer
backports more of its standard/spec support.

Author: jhaygood86

Source/HtmlRenderer.PdfSharp/HtmlRenderer.PdfSharp.csproj

@@ -29,6 +29,9 @@ Features and Benefits:
   <ItemGroup>
     <ProjectReference Include="..\HtmlRenderer\HtmlRenderer.csproj" />
   </ItemGroup>
+  <ItemGroup>
+    <InternalsVisibleTo Include="HtmlRenderer.PdfSharp.Test" />
+  </ItemGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.Win32.Registry" Version="5.0.0" />
     <PackageReference Include="PDFsharp" Version="6.2.4" />

Source/HtmlRenderer.WinForms/HtmlRenderer.WinForms.csproj

@@ -45,4 +45,7 @@ Features and Benefits:
   <ItemGroup>
     <ProjectReference Include="..\HtmlRenderer\HtmlRenderer.csproj" />
   </ItemGroup>
+  <ItemGroup>
+    <InternalsVisibleTo Include="HtmlRenderer.IntegrationTest" />
+  </ItemGroup>
 </Project>

Source/HtmlRenderer.sln

@@ -23,7 +23,9 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Test", "Test", "{E508FA78-D
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "HtmlRenderer.PdfSharp.Test", "Test\HtmlRenderer.PdfSharp.Test\HtmlRenderer.PdfSharp.Test.csproj", "{AF39851E-37B9-409E-A34D-CE091A098C86}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "HtmlRenderer.Test", "Test\HtmlRenderer.IntegrationTest\HtmlRenderer.IntegrationTest.csproj", "{A12F4432-337B-4030-B834-5D312A9FB16C}"
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "HtmlRenderer.IntegrationTest", "Test\HtmlRenderer.IntegrationTest\HtmlRenderer.IntegrationTest.csproj", "{A12F4432-337B-4030-B834-5D312A9FB16C}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "HtmlRenderer.Test", "Test\HtmlRenderer.Test\HtmlRenderer.Test.csproj", "{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -129,6 +131,18 @@ Global
 		{A12F4432-337B-4030-B834-5D312A9FB16C}.Release|Mixed Platforms.Build.0 = Release|Any CPU
 		{A12F4432-337B-4030-B834-5D312A9FB16C}.Release|x86.ActiveCfg = Release|Any CPU
 		{A12F4432-337B-4030-B834-5D312A9FB16C}.Release|x86.Build.0 = Release|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Debug|Mixed Platforms.ActiveCfg = Debug|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Debug|Mixed Platforms.Build.0 = Debug|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Debug|x86.Build.0 = Debug|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Release|Any CPU.Build.0 = Release|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Release|Mixed Platforms.Build.0 = Release|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Release|x86.ActiveCfg = Release|Any CPU
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -139,6 +153,7 @@ Global
 		{F02E0216-4AE3-474F-9381-FCB93411CDB0} = {E263EA16-2E6A-4269-A319-AA2F97ADA8E1}
 		{AF39851E-37B9-409E-A34D-CE091A098C86} = {E508FA78-D57E-492F-9BF7-23640001848A}
 		{A12F4432-337B-4030-B834-5D312A9FB16C} = {E508FA78-D57E-492F-9BF7-23640001848A}
+		{7427E12F-1524-4405-AAD1-5AF8ACB3BBBC} = {E508FA78-D57E-492F-9BF7-23640001848A}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {902788D6-3165-491D-B860-DF2F74E66C1D}

Source/HtmlRenderer/HtmlRenderer.csproj

@@ -22,6 +22,10 @@ For existing implementations see: HtmlRenderer.WinForms, HtmlRenderer.WPF and Ht
     <EmbeddedResource Include="Core\Utils\ImageError.png" />
     <EmbeddedResource Include="Core\Utils\ImageLoad.png" />
   </ItemGroup>
+  <ItemGroup>
+    <InternalsVisibleTo Include="HtmlRenderer.Test" />
+    <InternalsVisibleTo Include="HtmlRenderer.IntegrationTest" />
+  </ItemGroup>
   <ItemGroup>
     <None Include="..\..\README.md" Pack="true" PackagePath="\" />
   </ItemGroup>

Source/Test/HtmlRenderer.IntegrationTest/BoxModel/AtomicInlineLevelBoxCorrectionTests.cs

@@ -0,0 +1,85 @@
+using HtmlRenderer.IntegrationTest.TestSupport;
+
+namespace HtmlRenderer.IntegrationTest.BoxModel;
+
+/// <summary>
+/// DomParser's "block inside inline" DOM-correction pass (CorrectBlockInsideInline) should never look through an
+/// inline-level box that establishes its own independent formatting context (inline-block/inline-table both do)
+/// when deciding whether an ANCESTOR box needs splitting - DomUtils.ContainsInlinesOnly is meant to make such a
+/// box opaque for that purpose. A child whose own resolved display is "none" (not "inline") should not make the
+/// correction pass misclassify the box's content as containing a "block", incorrectly splitting the child out of
+/// its real parent entirely.
+/// </summary>
+/// <remarks>
+/// The triage note for this file claimed both cases already pass on this fork. Direct testing shows otherwise
+/// for the inline-block case: dumping the box tree for the &lt;select&gt;/&lt;option&gt; markup below shows
+/// <c>opt1</c> (the FIRST display:none &lt;option&gt;) gets hoisted out from under &lt;select&gt; entirely and
+/// becomes a sibling of the anonymous block box CorrectInlineBoxesParent wraps &lt;select&gt; in, while
+/// <c>opt2</c> (the second, otherwise-identical &lt;option&gt;) correctly stays nested. That first-child-only
+/// asymmetry is exactly the atomic-inline-level gap the class doc describes - it just was not caught by the
+/// triage pass. The inline-table case genuinely does pass, so only the inline-block test method is ignored
+/// (with the real, faithfully-ported assertions kept, to document the target behavior).
+/// </remarks>
+[DoNotParallelize]
+[TestClass]
+public sealed class AtomicInlineLevelBoxCorrectionTests
+{
+    [Ignore("Confirmed real bug on this fork, not a porting mistake: dumping the box tree shows opt1 (the " +
+            "FIRST display:none <option> child of an inline-block <select>) gets hoisted out from under " +
+            "<select> and becomes a sibling of the anonymous block wrapper CorrectInlineBoxesParent creates, " +
+            "while opt2 (second, otherwise-identical child) stays correctly nested. DomUtils.ContainsInlinesOnly " +
+            "does not treat inline-block as opaque the way an atomic-inline-level check should.")]
+    [TestMethod]
+    public void DisplayNoneChildOfInlineBlockBox_StaysNestedUnderItsRealParent()
+    {
+        var html = LayoutHarness.Wrap(
+            "<select id='sel'>" +
+            "<option id='opt1' style='display:none'>Red</option>" +
+            "<option id='opt2' style='display:none'>Green</option>" +
+            "</select>");
+
+        var (root, _) = LayoutHarness.Layout(html);
+        var select = LayoutHarness.FindById(root, "sel")!;
+        var opt1 = LayoutHarness.FindById(root, "opt1")!;
+        var opt2 = LayoutHarness.FindById(root, "opt2")!;
+
+        Assert.IsTrue(IsDescendantOf(opt1, select), "opt1 (display:none) must stay nested under its real <select> parent.");
+        Assert.IsTrue(IsDescendantOf(opt2, select), "opt2 must stay nested under its real <select> parent.");
+    }
+
+    [TestMethod]
+    public void DisplayNoneChildOfInlineTableBox_StaysNestedUnderItsRealParent()
+    {
+        var html = LayoutHarness.Wrap(
+            "<div id='wrap'>" +
+            "<div id='it' style='display:inline-table'>" +
+            "<div style='display:table-row'><div id='cell' style='display:table-cell'>cell</div></div>" +
+            "<div id='hidden' style='display:none'>hidden</div>" +
+            "</div>" +
+            "</div>");
+
+        var (root, _) = LayoutHarness.Layout(html);
+        var inlineTable = LayoutHarness.FindById(root, "it")!;
+        var hidden = LayoutHarness.FindById(root, "hidden")!;
+
+        Assert.IsTrue(IsDescendantOf(hidden, inlineTable), "a display:none sibling inside an inline-table must stay nested under it.");
+    }
+
+    // PeachPDF's source file also has a "DisplayNoneChildOfInlineFlexBox_StillStaysNestedUnderItsRealParent"
+    // regression case, guarding pre-existing display:inline-flex handling. HTML-Renderer (this fork) implements
+    // no flexbox layout at all - "flex"/"inline-flex" are not recognized display values anywhere in
+    // TheArtOfDev.HtmlRenderer.Core (confirmed: no "flex" hits in the Core source tree) - so there is no such
+    // pre-existing handling to guard, and porting that case would document a feature this fork doesn't have.
+    // Intentionally dropped rather than ported under a false premise.
+
+    private static bool IsDescendantOf(TheArtOfDev.HtmlRenderer.Core.Dom.CssBox box, TheArtOfDev.HtmlRenderer.Core.Dom.CssBox ancestor)
+    {
+        var current = box.ParentBox;
+        while (current != null)
+        {
+            if (ReferenceEquals(current, ancestor)) return true;
+            current = current.ParentBox;
+        }
+        return false;
+    }
+}