fix: address all code review issues from PR #8

- Remove reflection (Assembly.GetExecutingAssembly) for AOT safety
- Gate diagnostics behind LayoutDiagnostics record + EnableDiagnostics flag
- Remove InternalsVisibleTo for Playground, make ResourceLoaders public
- Use ConcurrentDictionary in MemoryResourceLoader for thread safety
- Add 10MB resource size limit in MemoryResourceLoader
- Fix silent catch in FontManager.PreloadFontFromResourcesAsync
- Fix race condition with atomic AddOrUpdate in FontManager
- Add min 1px bitmap guard to all Render overloads
- Escape innerHTML in context menu for XSS safety
- Remove leftover debug variable in LayoutEngine
- Add playground link to README, wiki Home and Getting Started

Author: RoboNET

README.md

@@ -7,6 +7,8 @@
 
 A .NET library for rendering images from YAML templates with a full CSS flexbox layout engine. Perfect for generating receipts, labels, tickets, and structured documents.
 
+**[Try it in the browser](https://robonet.github.io/FlexRender/)** -- WASM playground with live preview, no installation required.
+
 ## Features
 
 - **YAML Templates** -- define complex image layouts in readable YAML format

docs/wiki/Getting-Started.md

@@ -2,6 +2,8 @@
 
 This guide walks you through installing FlexRender, creating your first template, and rendering it using code, dependency injection, or the CLI.
 
+> **Want to try without installing?** Use the [browser playground](https://robonet.github.io/FlexRender/) -- edit YAML templates and see results instantly.
+
 ## Installation
 
 ### All-in-one (recommended)

docs/wiki/Home.md

@@ -7,6 +7,8 @@
 
 A modular .NET library for rendering images from YAML templates with a full CSS flexbox layout engine. Render-backend agnostic with SkiaSharp as the default backend. Fully AOT-compatible with zero reflection.
 
+**[Try it in the browser](https://robonet.github.io/FlexRender/)** -- WASM playground with live preview, no installation required.
+
 ## Why FlexRender?
 
 - **YAML-first** -- define complex image layouts in readable YAML, no design tools needed

src/FlexRender.Core/Configuration/FlexRenderBuilder.cs

@@ -70,12 +70,14 @@ public sealed class FlexRenderBuilder
 
     /// <summary>
     /// Gets the list of configured resource loaders.
+    /// Custom loaders can be inserted before <see cref="Build"/> is called to control
+    /// resolution priority (lower index = higher priority).
     /// </summary>
     /// <remarks>
-    /// Loaders are added lazily when <see cref="Build"/> is called to ensure
-    /// they receive the fully configured <see cref="Options"/> instance.
+    /// Built-in loaders (file, base64, embedded) are added lazily when <see cref="Build"/>
+    /// is called to ensure they receive the fully configured <see cref="Options"/> instance.
     /// </remarks>
-    internal List<IResourceLoader> ResourceLoaders { get; } = [];
+    public List<IResourceLoader> ResourceLoaders { get; } = [];
 
     /// <summary>
     /// Gets the configured filter registry, or <c>null</c> if no filters have been registered.

src/FlexRender.Core/FlexRender.Core.csproj

@@ -12,7 +12,6 @@
     <InternalsVisibleTo Include="FlexRender.Skia.Render" />
     <InternalsVisibleTo Include="FlexRender.Svg.Render" />
     <InternalsVisibleTo Include="FlexRender.ImageSharp.Render" />
-    <InternalsVisibleTo Include="FlexRender.Playground" />
   </ItemGroup>
 
 </Project>

src/FlexRender.Core/Layout/LayoutDiagnostics.cs

@@ -0,0 +1,14 @@
+namespace FlexRender.Layout;
+
+/// <summary>
+/// Diagnostic data attached to a <see cref="LayoutNode"/> for debugging text layout.
+/// </summary>
+/// <param name="IntrinsicWidth">Intrinsic width from IntrinsicMeasurer (before scaling).</param>
+/// <param name="ShapedWidth">Shaped width from TextShaper at final font size.</param>
+/// <param name="ContentWidth">Final content width used in layout calculation.</param>
+/// <param name="ResolvedTypeface">Resolved typeface family name.</param>
+public sealed record LayoutDiagnostics(
+    float IntrinsicWidth,
+    float ShapedWidth,
+    float ContentWidth,
+    string? ResolvedTypeface = null);

src/FlexRender.Core/Layout/LayoutEngine.cs

@@ -53,6 +53,12 @@ public LayoutEngine(ResourceLimits limits)
     /// </summary>
     public ITextShaper? TextShaper { get; set; }
 
+    /// <summary>
+    /// When true, populates <see cref="LayoutNode.Diagnostics"/> with text measurement
+    /// details (intrinsic width, shaped width, content width). Defaults to false.
+    /// </summary>
+    public bool EnableDiagnostics { get; set; }
+
     /// <summary>
     /// Base font size in pixels used for em resolution and as fallback when text elements
     /// don't specify an explicit size. Must match the renderer's base font size for
@@ -587,9 +593,10 @@ private LayoutNode LayoutTextElement(TextElement text, LayoutContext context)
         node.ComputedLineHeight = computedLineHeight;
         node.Baseline = padding.Top + border.Top.Width + textBaseline;
         node.ComputedFontSize = resolvedFontSize;
-        node.DiagContentWidth = contentWidth;
-        node.DiagIntrinsicWidth = diagIntrinsicW;
-        node.DiagShapedWidth = diagShapedW;
+        if (EnableDiagnostics)
+        {
+            node.Diagnostics = new LayoutDiagnostics(diagIntrinsicW, diagShapedW, contentWidth);
+        }
         return node;
     }
 
@@ -875,9 +882,7 @@ private float ComputeFitContentFontSize(FlexElement flex, LayoutContext innerCon
         // Floor to 0.1px to avoid rounding errors where text barely exceeds container width
         // due to non-linear font scaling (hinting, glyph rounding)
         var computed = refSize * availableWidth / totalMeasured;
-        var floored = MathF.Floor(computed * 10f) / 10f;
-
-        return floored;
+        return MathF.Floor(computed * 10f) / 10f;
     }
 
     private float MeasureContentWidth(TemplateElement element, LayoutContext context)

src/FlexRender.Core/Layout/LayoutNode.cs

@@ -62,26 +62,10 @@ public sealed class LayoutNode
     public float ComputedFontSize { get; set; }
 
     /// <summary>
-    /// Diagnostic: intrinsic width from IntrinsicMeasurer (before scaling).
-    /// Only populated for text elements during layout when diagnostics are enabled.
+    /// Optional diagnostic data populated during layout for debugging purposes.
+    /// Only populated when <see cref="LayoutEngine.EnableDiagnostics"/> is true.
     /// </summary>
-    public float DiagIntrinsicWidth { get; set; }
-
-    /// <summary>
-    /// Diagnostic: shaped width from TextShaper at final font size.
-    /// Only populated for text elements during layout when diagnostics are enabled.
-    /// </summary>
-    public float DiagShapedWidth { get; set; }
-
-    /// <summary>
-    /// Diagnostic: final content width used in layout calculation.
-    /// </summary>
-    public float DiagContentWidth { get; set; }
-
-    /// <summary>
-    /// Diagnostic: resolved typeface family name from FontManager.
-    /// </summary>
-    public string? DiagResolvedTypeface { get; set; }
+    public LayoutDiagnostics? Diagnostics { get; set; }
 
     /// <summary>Right edge (X + Width).</summary>
     public float Right => X + Width;

src/FlexRender.Playground/FlexRender.Playground.csproj

@@ -26,8 +26,4 @@
     <NativeFileReference Include="$(NuGetPackageRoot)skiasharp.nativeassets.webassembly/3.119.2/buildTransitive/netstandard1.0/libSkiaSharp.a/3.1.56/st/*.a" />
   </ItemGroup>
 
-  <!-- Embedded default font for WASM (no system fonts available) -->
-  <ItemGroup>
-    <EmbeddedResource Include="Fonts/Inter-Regular.ttf" LogicalName="Inter-Regular.ttf" />
-  </ItemGroup>
 </Project>

src/FlexRender.Playground/MemoryResourceLoader.cs

@@ -1,3 +1,4 @@
+using System.Collections.Concurrent;
 using FlexRender.Abstractions;
 
 namespace FlexRender.Playground;
@@ -8,7 +9,9 @@ namespace FlexRender.Playground;
 /// </summary>
 internal sealed class MemoryResourceLoader : IResourceLoader
 {
-    private readonly Dictionary<string, byte[]> _resources = new(StringComparer.OrdinalIgnoreCase);
+    private const int MaxResourceSize = 10 * 1024 * 1024; // 10 MB per resource
+
+    private readonly ConcurrentDictionary<string, byte[]> _resources = new(StringComparer.OrdinalIgnoreCase);
 
     /// <inheritdoc />
     /// <remarks>Priority 10 ensures uploaded files override all other loaders.</remarks>
@@ -59,6 +62,9 @@ public void AddResource(string name, byte[] data)
         ArgumentNullException.ThrowIfNull(name);
         ArgumentNullException.ThrowIfNull(data);
 
+        if (data.Length > MaxResourceSize)
+            throw new ArgumentException($"Resource exceeds maximum size of {MaxResourceSize / 1024 / 1024} MB.", nameof(data));
+
         _resources[NormalizePath(name)] = data;
     }
 
@@ -70,15 +76,15 @@ public void RemoveResource(string name)
     {
         ArgumentNullException.ThrowIfNull(name);
 
-        _resources.Remove(NormalizePath(name));
+        _resources.TryRemove(NormalizePath(name), out _);
     }
 
     /// <summary>
     /// Removes all stored resources.
     /// </summary>
     public void Clear()
     {
-        _resources.Clear();
+        _resources.Clear(); // ConcurrentDictionary.Clear is thread-safe
     }
 
     /// <summary>