High-level requirements

Component compatibility

Attributes to support:

• min-font-size
• max-font-size

Migration Notes:

• 1.0 resizes to clientHeight and clientWidth, whereas 0.1 resize to offsetHeight and offsetWidth. The difference here is the exclusion of margins and borders from the fit-text coverage area.

Open tasks:

• Initial implementation in ✨ [amp-fit-text] Initial Bento component #28169
• Do not depend on children to resize in [amp-fit-text:1.0] Use ResizeObserver for content changes #28496
• Watch for attribute mutations in Bento mode.
  • Remove the specifically attached MutationObserver for attributes in amp-fit-text when a generic one is in place in PreactBaseElement.
  • The generic one should call mutatedAttributesCallback to handle Bento mode.
  • In AMP mode this will cause it to be doubly called -- need to fine tune this.
• Resolve infinite render issue when observing mutations on both subtree and attributes.
• Support passing in a parser callback for PreactBaseElement props
• Investigate e2e test failures for amp4ads-preset environments
• Remove constant line-height and support configuring lineHeight
• Polyfill ResizeObserver
• Make attrs media based