Enhance configuration support

Sources/MarkdownView/Customizations/Block Quotes/BlockQuoteStyle.swift

@@ -41,12 +41,16 @@ public struct BlockQuoteStyleConfiguration {
             self.blockQuote = blockQuote
         }
 
+        private var children: [Markup] {
+            Array(blockQuote.children)
+        }
+
         @_documentation(visibility: internal)
         public var body: some View {
             VStack(alignment: .leading, spacing: configuration.componentSpacing) {
-                ForEach(Array(blockQuote.children.enumerated()), id: \.offset) { _, child in
+                ForEach(children.indices, id: \.self) { index in
                     CmarkNodeVisitor(configuration: configuration)
-                        .makeBody(for: child)
+                        .makeBody(for: children[index])
                 }
             }
         }

Sources/MarkdownView/Customizations/Table/Configuration/MarkdownTableStyleConfiguration.Table.swift

@@ -38,8 +38,8 @@ extension MarkdownTableStyleConfiguration.Table: View {
         if #available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *) {
             Grid(horizontalSpacing: 0, verticalSpacing: 0) {
                 header
-                ForEach(Array(rows.enumerated()), id: \.offset) { (_, row) in
-                    row
+                ForEach(rows.indices, id: \.self) { index in
+                    rows[index]
                 }
             }
         } else {

Sources/MarkdownView/Customizations/Table/DefaultMarkdownTableStyle.swift

@@ -42,11 +42,11 @@ fileprivate struct DefaultMarkdownTable: View {
             if #available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *) {
                 Grid(horizontalSpacing: 0, verticalSpacing: 0) {
                     configuration.table.header
-                    ForEach(Array(configuration.table.rows.enumerated()), id: \.offset) { (_, row) in
+                    ForEach(configuration.table.rows.indices, id: \.self) { index in
                         if showsRowSeparators {
                             Divider()
                         }
-                        row
+                        configuration.table.rows[index]
                     }
                 }
             } else {

Sources/MarkdownView/Customizations/Table/GithubMarkdownTableStyle.swift

@@ -63,9 +63,9 @@ fileprivate struct GithubMarkdownTable: View {
                 Grid(horizontalSpacing: 0, verticalSpacing: 0) {
                     configuration.table.header
 
-                    ForEach(Array(configuration.table.rows.enumerated()), id: \.offset) { (index, row) in
+                    ForEach(configuration.table.rows.indices, id: \.self) { index in
                         let backgroundStyle = index % 2 == 0 ? AnyShapeStyle(backgroundColor) : AnyShapeStyle(alternativeRowColor)
-                        row
+                        configuration.table.rows[index]
                             .markdownTableRowBackgroundStyle(backgroundStyle)
                     }
                 }

Sources/MarkdownView/MarkdownReader.swift

@@ -21,25 +21,25 @@ import SwiftUI
 /// }
 /// ```
 public struct MarkdownReader<Content: View>: View {
-    @ObservedObject private var content: MarkdownContent
+    @StateObject private var content: MarkdownContent
     private var _body: (_ markdownContent: MarkdownContent) -> Content
-    
+
     public init(
         _ text: String,
         @ViewBuilder contents: @escaping (MarkdownContent) -> Content
     ) {
-        content = MarkdownContent(text)
+        _content = StateObject(wrappedValue: MarkdownContent(text))
         self._body = contents
     }
-    
+
     public init(
         _ url: URL,
         @ViewBuilder contents: @escaping (MarkdownContent) -> Content
     ) {
-        content = MarkdownContent(url)
+        _content = StateObject(wrappedValue: MarkdownContent(url))
         self._body = contents
     }
-    
+
     public var body: some View {
         _body(content)
     }

Sources/MarkdownView/MarkdownView.swift

@@ -3,34 +3,91 @@ import Markdown
 
 /// A view that renders markdown content.
 public struct MarkdownView: View {
-    @ObservedObject private var content: MarkdownContent
-
+    /// Owned content for the string/URL inits — created once, survives parent re‑renders.
+    @StateObject private var ownedContent: MarkdownContent
+    /// External content passed via ``init(_:)-MarkdownContent``.
+    @ObservedObject private var externalContent: MarkdownContent
+    /// Which source of truth to use.
+    private var usesExternalContent: Bool
+
+    private var content: MarkdownContent {
+        usesExternalContent ? externalContent : ownedContent
+    }
+
     @Environment(\.markdownRendererConfiguration) private var configuration
     @Environment(\.markdownViewRenderer) private var renderer
-
+    @Environment(\.headingStyleGroup) private var headingStyleGroup
+
     /// Creates a view that renders given markdown string.
     /// - Parameter text: The markdown source to render.
     public init(_ text: String) {
-        self.content = MarkdownContent(text)
+        let content = MarkdownContent(text)
+        _ownedContent = StateObject(wrappedValue: content)
+        _externalContent = ObservedObject(wrappedValue: content)
+        usesExternalContent = false
     }
-    
+
     /// Creates a view that renders the markdown from a local file at given url.
     /// - Parameter url: The url to the markdown file to render.
     public init(_ url: URL) {
-        self.content =  MarkdownContent(url)
+        let content = MarkdownContent(url)
+        _ownedContent = StateObject(wrappedValue: content)
+        _externalContent = ObservedObject(wrappedValue: content)
+        usesExternalContent = false
     }
-    
+
     /// Creates an instance that renders from a ``MarkdownContent`` .
     /// - Parameter content: The ``MarkdownContent`` to render.
     public init(_ content: MarkdownContent) {
-        self.content = content
+        _ownedContent = StateObject(wrappedValue: content)
+        _externalContent = ObservedObject(wrappedValue: content)
+        usesExternalContent = true
     }
-    
+
     public var body: some View {
-        renderer
-            .makeBody(content: content, configuration: configuration)
-            .erasedToAnyView()
-            .font(configuration.fonts[.body] ?? Font.body)
+        var config = configuration
+        config.headingStyleGroup = headingStyleGroup
+        return MarkdownRenderingView(
+            content: content,
+            configuration: config
+        )
+        .font(configuration.fonts[.body] ?? Font.body)
+    }
+}
+
+/// A cache that stores the last rendered view alongside the inputs that
+/// produced it. Because this is a reference type stored in `@State`, it
+/// persists across body evaluations without triggering additional renders.
+@MainActor
+private final class RenderCache {
+    var raw: MarkdownContent.Raw?
+    var configuration: MarkdownRendererConfiguration?
+    var rendered: AnyView = AnyView(EmptyView())
+}
+
+/// An inner view that caches the rendered output.
+///
+/// Rendering is skipped when the markdown source and configuration
+/// have not changed since the last evaluation.
+private struct MarkdownRenderingView: View {
+    let content: MarkdownContent
+    let configuration: MarkdownRendererConfiguration
+
+    @Environment(\.markdownViewRenderer) private var renderer
+    @State private var cache = RenderCache()
+
+    var body: some View {
+        let currentRaw = (try? content.markdown).map { MarkdownContent.Raw.plainText($0) }
+        if currentRaw != cache.raw || configuration != cache.configuration {
+            let rendered = renderer
+                .makeBody(content: content, configuration: configuration)
+                .erasedToAnyView()
+            cache.raw = currentRaw
+            cache.configuration = configuration
+            cache.rendered = rendered
+            return rendered
+        }
+        return cache.rendered
     }
 }
 

Sources/MarkdownView/Renderers/Cmark/CmarkFirstMarkdownViewRenderer.swift

@@ -36,7 +36,7 @@ struct TextViewViewRenderer: MarkdownViewRenderer {
         if !configuration.allowedBlockDirectiveRenderers.isEmpty {
             parseOptions.insert(.parseBlockDirectives)
         }
-        
+
         let textContent = CmarkTextContentVisitor(configuration: configuration)
             .makeTextContent(for: content.document(options: parseOptions))
         return TextView {

Sources/MarkdownView/Renderers/Cmark/CmarkNodeVisitor.swift

@@ -25,23 +25,21 @@ struct CmarkNodeVisitor: @preconcurrency MarkupVisitor {
     }
 
     func visitDocument(_ document: Document) -> MarkdownNodeView {
-        var renderer = self
+        var visitor = self
         let nodeViews = document.children.map {
-            renderer.visit($0)
+            visitor.visit($0)
         }
         return MarkdownNodeView(nodeViews, layoutPolicy: .linebreak)
     }
-    
+
     func defaultVisit(_ markup: Markdown.Markup) -> MarkdownNodeView {
         descendInto(markup)
     }
-    
+
     func descendInto(_ markup: any Markup) -> MarkdownNodeView {
-        var nodeViews = [MarkdownNodeView]()
-        for child in markup.children {
-            var renderer = self
-            let nodeView = renderer.visit(child)
-            nodeViews.append(nodeView)
+        var visitor = self
+        let nodeViews = markup.children.map {
+            visitor.visit($0)
         }
         return MarkdownNodeView(nodeViews)
     }
@@ -170,11 +168,9 @@ struct CmarkNodeVisitor: @preconcurrency MarkupVisitor {
     }
 
     func visitTableCell(_ cell: Markdown.Table.Cell) -> MarkdownNodeView {
-        var cellViews = [MarkdownNodeView]()
-        for child in cell.children {
-            var renderer = CmarkNodeVisitor(configuration: configuration)
-            let cellView = renderer.visit(child)
-            cellViews.append(cellView)
+        var visitor = self
+        let cellViews = cell.children.map {
+            visitor.visit($0)
         }
         return MarkdownNodeView(
             cellViews,
@@ -193,10 +189,10 @@ struct CmarkNodeVisitor: @preconcurrency MarkupVisitor {
     }
 
     func visitEmphasis(_ emphasis: Markdown.Emphasis) -> MarkdownNodeView {
+        var visitor = self
         var attributedString = AttributedString()
         for child in emphasis.children {
-            var renderer = self
-            guard let text = renderer.visit(child).asAttributedString else { continue }
+            guard let text = visitor.visit(child).asAttributedString else { continue }
             let intent = text.inlinePresentationIntent ?? []
             attributedString += text.mergingAttributes(
                 AttributeContainer()
@@ -205,12 +201,12 @@ struct CmarkNodeVisitor: @preconcurrency MarkupVisitor {
         }
         return MarkdownNodeView(attributedString)
     }
-    
+
     func visitStrong(_ strong: Strong) -> MarkdownNodeView {
+        var visitor = self
         var attributedString = AttributedString()
         for child in strong.children {
-            var renderer = self
-            guard let text = renderer.visit(child).asAttributedString else { continue }
+            guard let text = visitor.visit(child).asAttributedString else { continue }
             let intent = text.inlinePresentationIntent ?? []
             attributedString += text.mergingAttributes(
                 AttributeContainer()
@@ -219,12 +215,12 @@ struct CmarkNodeVisitor: @preconcurrency MarkupVisitor {
         }
         return MarkdownNodeView(attributedString)
     }
-    
+
     func visitStrikethrough(_ strikethrough: Strikethrough) -> MarkdownNodeView {
+        var visitor = self
         var attributedString = AttributedString()
         for child in strikethrough.children {
-            var renderer = self
-            guard let text = renderer.visit(child).asAttributedString else { continue }
+            guard let text = visitor.visit(child).asAttributedString else { continue }
             let intent = text.inlinePresentationIntent ?? []
             attributedString += text.mergingAttributes(
                 AttributeContainer()
@@ -241,20 +237,26 @@ struct CmarkNodeVisitor: @preconcurrency MarkupVisitor {
 
         let nodeView = descendInto(link)
         let tintColor = configuration.preferredTintColors[.link] ?? .accentColor
+        let underline = configuration.underlineLinks
         return if let attributedString = nodeView.asAttributedString {
             MarkdownNodeView(
-                attributedString.mergingAttributes(
-                    AttributeContainer()
+                attributedString.mergingAttributes({
+                    var container = AttributeContainer()
                         .link(url)
                         .foregroundColor(tintColor)
-                )
+                    if underline {
+                        container.underlineStyle = .single
+                    }
+                    return container
+                }())
             )
         } else {
              MarkdownNodeView {
                 Link(destination: url) {
                     nodeView
                 }
                 .foregroundStyle(tintColor)
+                .underline(underline)
             }
         }
     }