Optimize Prism.js code highlighting for multiple code blocks

[ethylon]

Motivation

When displaying multiple code blocks on a single page, using Prism.js’s global highlightAll function caused excessive DOM overhead, resulting in deeply nested fragments and poor page responsiveness. This was especially problematic for pages with many code samples, where the UI could become sluggish or even unresponsive.

Real life example from my page with a dozen <CodeBlock>

Before

After

Changes

• Added a method to highlight individual code blocks (HighlightAsync(ElementReference)) in addition to the global method.
• Introduced the AutoHighlight parameter in the Blazor <CodeBlock> component, allowing each block to highlight itself after rendering, rather than triggering a global highlight.

Benefits

• Significantly reduces DOM overhead and improves performance on pages with many code blocks.
• Enhances user experience and page responsiveness, even with large numbers of code samples.

[gemini-code-assist]

Summary of Changes

Hello @ethylon, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the performance and responsiveness of pages displaying multiple code blocks by optimizing the Prism.js code highlighting mechanism. Instead of using a single global highlight function that caused excessive DOM overhead, the system now supports individual code block highlighting. This is achieved by introducing a new HighlightAsync method for specific elements and an AutoHighlight parameter in the Blazor CodeBlock component, allowing each block to manage its own highlighting efficiently.

Highlights

• Performance Improvement: Addresses significant DOM overhead and poor responsiveness when using Prism.js's global highlightAll function with multiple code blocks on a single page.
• Individual Code Block Highlighting: Introduced a new HighlightAsync(ElementReference) method in PrismJsInterop to allow highlighting of specific code elements, moving away from global highlighting.
• AutoHighlight Parameter: Added an AutoHighlight boolean parameter to the Blazor <CodeBlock> component, enabling each block to highlight itself individually after rendering, rather than relying on a global highlight call.
• JavaScript Interop Refinement: Refactored the prismInterop.js to include a waitForPrism helper and a new highlightElement function for targeted highlighting, ensuring Prism.js is ready before execution.

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[gemini-code-assist]

Code Review

This is a great pull request that addresses a significant performance issue with a clear and effective solution. The introduction of individual code block highlighting is a smart optimization that will greatly improve page responsiveness on pages with many code blocks. The changes are well-structured across the Blazor component, C# interop, and JavaScript files.

I have one minor suggestion in the JavaScript helper to prevent a potential timer leak, but overall this is excellent work. The detailed pull request description with before/after examples is also very helpful.