feat(ios): integrate RaTeX for LaTeX math rendering, replacing iosMath

[hryhoriiK97]

What/Why?

Replace iosMath with RaTeX for iOS LaTeX math rendering, aligning iOS with the Android migration (PR #355).

iosMath only supports a limited subset of LaTeX and is no longer actively maintained. RaTeX is a modern, Rust-based, KaTeX-compatible engine that renders math natively via CoreGraphics — no WebView, no JavaScript. This gives iOS feature parity with web (KaTeX) and Android (RaTeX).

Changes

New file:

• ios/math/ENRMRaTeXBridge.swift — Swift-to-ObjC bridge exposing ENRMRaTeXBridge.parse() and ENRMRaTeXRenderResult (width, ascent, descent, draw) to existing Objective-C code.

Podspec (ReactNativeEnrichedMarkdown.podspec):

• Removed iosMath dependency.
• Added conditional spm_dependency for RaTeX v0.1.9+ (requires cocoapods-spm plugin).
• Swift source files conditionally included only when math is enabled.
• C/C++ headers marked as private to prevent module map conflicts with use_frameworks!.

Migrated ObjC files:

• ENRMMathContainerView.m — Replaced MTMathUILabel with a custom ENRMRaTeXCanvasView that draws via ENRMRaTeXRenderResult. Added alignment support (center/left/right) and correct overflow scrolling.
• ENRMMathInlineAttachment.m — Replaced MTMathUILabel with ENRMRaTeXBridge.parse(). Uses ceil() for dimension rounding to prevent sub-pixel clipping.
• ENRMMathInlineAttachment+macOS.m — Same migration for macOS. Added CTM flip since RaTeX expects top-left origin (UIKit-style) but NSImage.lockFocus uses bottom-left origin.
• ENRMMathInlineAttachmentShared.h — Replaced MTMathListDisplay ivar with ENRMRaTeXRenderResult.
• ENRMFeatureFlags.h — Auto-detection now checks for RaTeX headers instead of iosMath.

Example app & docs:

• Podfile — Sets USE_FRAMEWORKS=dynamic when math is enabled (required for SPM interop).
• LATEX_MATH.md — Updated references from iosMath to RaTeX, documented use_frameworks! requirement.

Consumer impact

• Math disabled (ENRICHED_MARKDOWN_ENABLE_MATH=0): No change — no RaTeX dependency, no dynamic frameworks required.

Testing

Screenshots

Screen.Recording.2026-05-27.at.15.28.33.mov

PR Checklist

• Code compiles and runs on iOS
• Code compiles and runs on Android
• Updated documentation/README if applicable
• Ran example app to verify changes
• E2E tests are passing
• Required E2E tests have been added (if applicable)

[eszlamczyk]

LGTM, just one nit

[eszlamczyk]

Nit: Im wondering if we shouldn't futureproof it. For example what if we add another dependency that needs swift bridge, then this code would scilently ignore this dependency when math is disabled.

Maybe something like this would be better?

Suggested change

	if enable_math
	s.source_files = "ios/**/*.{h,m,mm,cpp,swift}", "cpp/md4c/*.{c,h}", "cpp/parser/*.{hpp,cpp}"
	else
	s.source_files = "ios/**/*.{h,m,mm,cpp}", "cpp/md4c/*.{c,h}", "cpp/parser/*.{hpp,cpp}"
	end
	s.source_files = "ios/**/*.{h,m,mm,cpp,swift}", "cpp/md4c/*.{c,h}", "cpp/parser/*.{hpp,cpp}"
	if enable_math
	s.exclude_files = "ios/math/ENRMRaTeXBridge.swift"
	end