feat(react-native): let surveys cap how far their text scales, per text role

[safaiyeh]

Problem

React Native surveys render every Text and TextInput with no maxFontSizeMultiplier, so survey copy scales without a ceiling under the OS text-size setting.

At the largest accessibility sizes an 18pt question headline renders roughly one word per line on a small phone, with the ? alone on its own line. Nothing clips and the card still scrolls — but in an app that caps its own text, the survey becomes the one uncapped thing on the screen.

A host app cannot fix this from the outside. React Native only inherits maxFontSizeMultiplier through nested Text, and these are siblings inside Views, so the value has to come in through the survey's own API.

What this adds

appearance.maxFontSizeMultiplier — one number for the whole survey, or an object keyed by text role:

<Questions appearance={{ ...appearance, maxFontSizeMultiplier: 1.6 }} … />

<Questions
  appearance={{
    ...appearance,
    maxFontSizeMultiplier: { question: 1.5, description: 1.8, ratingNumber: 1.2 },
  }}
  …
/>

Why per role, and not one number

One ceiling cannot serve every kind of text a survey draws. question is a headline that can wrap freely; ratingNumber sits inside a fixed-width button and has nowhere to grow; button sits in a row that has to stay one line. An app that already caps its own text by role wants to match those ceilings here rather than flatten them to a single value.

The nine roles cover all 16 text nodes the survey renders:

role	nodes
question	question headline
description	question, intro-screen and thank-you descriptions
header	intro-screen and thank-you headers
choice	choice labels
input	open-text answer, open-choice field
button	submit / next label
ratingLabel	lower- and upper-bound labels
ratingNumber	the numeral inside a rating button
validationHint	hint under an open-text answer

Because appearance is already threaded to every survey component, this needed no new prop plumbing.

Nothing changes unless it is set

• An unset appearance passes undefined, which is React Native's "no ceiling" — every existing survey renders exactly as it does today.
• A role omitted from the object is likewise uncapped.
• 0 is passed through rather than swallowed. In React Native that is a documented value meaning no maximum, not an absent one, so the resolver tests typeof … === 'number' instead of truthiness.

Two supporting type fixes the option needs

Both are places where a React Native-only appearance field could not reach the component that reads it:

• PostHogSurveyProvider's defaultSurveyAppearance was typed as the shared SurveyAppearance, so RN-only fields could not be passed — even though the provider already merges that object into a SurveyAppearanceTheme. Now Partial<SurveyAppearanceTheme>.
• getQuestionComponent's intermediate props type narrowed appearance back to the shared SurveyAppearance, dropping every RN-only field; the as any on the call below hid it. The question components themselves already declare SurveyAppearanceTheme.

Tests

New test/surveyMaxFontSizeMultiplier.spec.tsx — 9 tests covering the resolver (unset, flat number, per-role, omitted role, 0) and the wiring (no ceiling when unconfigured; headline and description getting different ceilings; the button capped independently).

One line in test/surveys-autoScroll.spec.tsx: its react-native shim renders Text as a div and spreads unknown props, so it now strips this native-only prop alongside the others it already strips.

Checks

Ran from the repo root, per packages/react-native/CONTRIBUTING.md:

• pnpm --filter=posthog-react-native lint — clean
• pnpm --filter=posthog-react-native test — 612 passed, 42 suites
• pnpm --filter=posthog-react-native build — clean

Changeset included (minor).

Deliberately left out

allowFontScaling. It would be one more field, but it turns OS text scaling off entirely rather than bounding it, which is the opposite of what this PR is for — happy to add it if you'd rather the surface be complete.

[marandaneto]

thanks @safaiyeh
i'll defer to @PostHog/team-surveys since this is a SDK configuration only

The shared SurveyAppearance type and PostHog survey API do not include this field, so it cannot currently be configured from the PostHog survey editor/API

Moving to draft until we hear from @PostHog/team-surveys

[marandaneto]

Inline review findings from the validated review.

[marandaneto]

blocking: Preserve previously accepted appearance keys

Changing this prop from SurveyAppearance to Partial<SurveyAppearanceTheme> drops widgetSelector, widgetType, widgetColor, widgetLabel, and shuffleQuestions from accepted object-literal keys, so existing TypeScript callers using them fail excess-property checks. Please extend the existing public appearance contract with the React Native-only field rather than narrowing it.

[marandaneto]

blocking: Expose the new option through a public appearance type

The package root still exports only SurveyAppearance from @posthog/core, which lacks this field, while neither SurveyAppearanceTheme nor the referenced SurveyTextRole is publicly exported. Consumers therefore cannot type reusable appearance configuration containing maxFontSizeMultiplier, and API Extractor reports forgotten exports. Please export a public React Native appearance type and its referenced role type, and use it for public props.

[marandaneto]

blocking: Apply the survey-wide cap to fallback icon text

When react-native-svg or its native view managers are unavailable, icons.tsx renders glyph fallbacks with React Native Text, but those nodes never receive this cap. A numeric whole-survey limit therefore does not cover every Text, and the glyphs can scale and clip inside their fixed dimensions. Pass the relevant cap to those fallbacks or disable font scaling for icon-only glyphs.