fix/enable simple html inline css

[s-brankovic]

Fix inline CSS styles not being applied (React 19 compatibility)

Problem

Inline style="" attributes in HTML content rendered by SimpleHtml are silently ignored on native devices. This means any HTML with inline styling (colors, text-align, background-color, font-size, etc.) renders without those styles.

Root Cause

react-native-render-html v6.3.4 relies on defaultProps to set default values for its TRenderEngineProvider component, including enableCSSInlineProcessing: true. React 19 (shipped with RN 0.78) completely removed support for defaultProps on function components, causing these defaults to become undefined. When enableCSSInlineProcessing is undefined (falsy), the transient render engine skips all inline style parsing.

Fix

Explicitly pass the three most impactful TRenderEngineProvider defaults in SimpleHtml's htmlProps:

• enableCSSInlineProcessing: true — required, without this all inline styles are ignored
• enableUserAgentStyles: true — ensures user-agent styles apply (e.g., <b> renders bold, <em> renders italic)
• emSize: 14 — ensures em/rem CSS units resolve correctly

The remaining defaults (classesStyles, ignoredDomTags, htmlParserOptions, fallbackFonts) have built-in fallbacks in the library's internal code (buildTREFromConfig.js) and don't require explicit overrides.

Other internal components using defaultProps (TNodeRenderer, TChildrenRenderer, TNodeChildrenRenderer) were verified safe — their compiled code uses optional chaining or JS default parameters, preventing crashes when defaultProps is stripped.

We also considered using the existing patches recommended in the issues bellow , but decided they were an overhaul for our specific use case.

References

• Issue #691: Inline style cannot be rendered — same root cause, confirmed fix with enableCSSInlineProcessing: true
• Issue #684: defaultProps warning/error — original report of defaultProps deprecation
• Issue #688: TNodeChildrenRenderer defaultProps warning — related internal component warnings
• PR #687: Fix deprecated defaultProps — community patch replacing all defaultProps with JS default parameters (9500+ line diff, unmerged)
• Issue #674: Migration to @native-html/render — react-native-render-html is being deprecated in favor of @native-html/render (alpha, co-maintained by Software Mansion) - We might consider switching to this package in the future when out of alfa.

---

[tomislav-arambasic]

GG WP