Add powerpoint support (#71)

Author: SimonCropp

src/DeterministicIoPackaging/DeterministicPackage.cs

@@ -11,6 +11,7 @@ static IReadOnlyList<IPatcher> CreatePatchers()
         var documentRelsPatcher = new DocumentRelationshipPatcher();
         var sheetRelsPatcher = new SheetRelationshipPatcher();
         var wordPartRelsPatcher = new WordPartRelationshipPatcher();
+        var pptxRelsPatcher = new PptxRelationshipPatcher();
         return
         [
             new ContentTypesPatcher(),
@@ -24,6 +25,8 @@ static IReadOnlyList<IPatcher> CreatePatchers()
             new DocumentPatcher(documentRelsPatcher),
             wordPartRelsPatcher,
             new WordPartPatcher(wordPartRelsPatcher),
+            pptxRelsPatcher,
+            new PptxContentPatcher(pptxRelsPatcher),
             new NumberingPatcher()
         ];
     }

src/DeterministicIoPackaging/Patching/PptxContentPatcher.cs

@@ -0,0 +1,22 @@
+// Patches PowerPoint content XML files (presentation.xml, slide*.xml,
+// slideLayout*.xml, slideMaster*.xml, notesSlide*.xml, etc.) to remap
+// relationship IDs that were renumbered by PptxRelationshipPatcher.
+//
+// Must be registered after PptxRelationshipPatcher so that ID mappings
+// are populated before this patcher runs.
+class PptxContentPatcher(PptxRelationshipPatcher relsPatcher) : IPatcher
+{
+    public bool IsMatch(Entry entry) =>
+        entry.FullName.StartsWith("ppt/") &&
+        !entry.FullName.Contains("/_rels/") &&
+        entry.FullName.EndsWith(".xml") &&
+        relsPatcher.IdMappings.ContainsKey(entry.FullName);
+
+    public void PatchXml(XDocument xml, string entryName)
+    {
+        if (relsPatcher.IdMappings.TryGetValue(entryName, out var mapping) && mapping.Count > 0)
+        {
+            RelationshipRenumber.RemapIds(xml, mapping);
+        }
+    }
+}

src/DeterministicIoPackaging/Patching/PptxRelationshipPatcher.cs

@@ -0,0 +1,33 @@
+// Patches relationship files for PowerPoint parts (presentation, slides,
+// slide layouts, slide masters, notes, themes, etc.). Handles any .rels file
+// under ppt/ — e.g. ppt/_rels/presentation.xml.rels,
+// ppt/slides/_rels/slide1.xml.rels, ppt/slideMasters/_rels/slideMaster1.xml.rels.
+//
+// These .rels files contain non-deterministic relationship IDs generated by
+// OpenXml SDK methods such as AddPart. This patcher renumbers them to
+// deterministic "DeterministicId{n}" values and stores the old→new mapping
+// so the corresponding content patcher (PptxContentPatcher) can remap r:id
+// references in the matching XML content file.
+class PptxRelationshipPatcher : IPatcher
+{
+    // Keyed by content file name (e.g. "ppt/slides/slide1.xml") → old-to-new ID mapping
+    internal Dictionary<string, Dictionary<string, string>> IdMappings { get; } = new(StringComparer.OrdinalIgnoreCase);
+
+    public bool IsMatch(Entry entry) =>
+        entry.FullName.StartsWith("ppt/") &&
+        entry.FullName.Contains("/_rels/") &&
+        entry.FullName.EndsWith(".xml.rels");
+
+    public void PatchXml(XDocument xml, string entryName)
+    {
+        var mapping = RelationshipRenumber.RenumberAndSort(xml, entryName);
+
+        // Derive content file path from .rels path:
+        // "ppt/slides/_rels/slide1.xml.rels" → "ppt/slides/slide1.xml"
+        // "ppt/_rels/presentation.xml.rels" → "ppt/presentation.xml"
+        var contentName = entryName
+            .Replace("/_rels/", "/")
+            .Replace(".xml.rels", ".xml");
+        IdMappings[contentName] = mapping;
+    }
+}

src/Directory.Build.props

@@ -2,7 +2,7 @@
 <Project>
   <PropertyGroup>
     <NoWarn>CS1591;CS0649;CA1416;NU1608;NU1109;NU1510</NoWarn>
-    <Version>0.24.3</Version>
+    <Version>0.25.0</Version>
     <LangVersion>preview</LangVersion>
     <AssemblyVersion>1.0.0</AssemblyVersion>
     <Description>Modify System.IO.Packaging (https://learn.microsoft.com/en-us/dotnet/api/system.io.packaging) files to ensure they are deterministic. Helpful for testing, build reproducibility, security verification, and ensuring package integrity across different build environments.</Description>

src/Directory.Packages.props

@@ -4,7 +4,7 @@
     <CentralPackageTransitivePinningEnabled>true</CentralPackageTransitivePinningEnabled>
   </PropertyGroup>
   <ItemGroup>
-    <PackageVersion Include="MarkdownSnippets.MsBuild" Version="28.0.2" />
+    <PackageVersion Include="MarkdownSnippets.MsBuild" Version="28.1.0" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.4.0" />
     <PackageVersion Include="NUnit" Version="4.5.1" />
     <PackageVersion Include="NUnit3TestAdapter" Version="6.2.0" />