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Doesn't work on legacy HTML documents #3

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CITguy opened this issue Mar 30, 2019 · 1 comment
Open

Doesn't work on legacy HTML documents #3

CITguy opened this issue Mar 30, 2019 · 1 comment

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@CITguy
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CITguy commented Mar 30, 2019

Specifically, it doesn't apply correctly to documents with a declared doctype that doesn't support CSS (e.g., HTML 3).

For example:
We can't reliably apply filter: grayscale(100%); if the document relies on text, bgcolor, or similar stylistic attributes used in HTML 3 or older.

Maybe provide a warning when toggling that the doctype is too old to reliably function.
@CITguy
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CITguy commented Mar 30, 2019

Doctype Reference

HTML 5 (and beyond)

<!DOCTYPE html>
  • OK - I've high confidence that the vast majority of pages with this doctype are using CSS instead of stylistic attributes.

XHTML 1.0 Strict

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
  • OK - DTD doesn't support stylistic attributes

XHTML 1.0 Transitional

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
  • WARN - DTD supports old stylistic attributes
    • <body> color attributes: text, link, vlink, alink, bgcolor
    • elements supporting bgcolor attribute: <table>, <tr>, <th>, <td>

XHTML 1.0 Frameset

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
  • WARN - Same as XHTML 1.0 Transitional

XHTML 1.1

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
  • OK - Same as XHTML 1.0 strict

XHTML 1.1 Basic

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.1//EN" "http://www.w3.org/TR/xhtml-basic/xhtml-basic11.dtd">
  • OK - Same as XHTML 1.0 Strict

HTML 4.01 Strict

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
  • OK - DTD doesn't support stylistic attributes

HTML 4.01 Transitional

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
  • WARN - DTD supports stylistic attributes
    • <body> color attributes: text, link, vlink, alink, and bgcolor (%bodycolors DTD entity)
    • bgcolor attribute: <table>, <tr>, <th>, <td>

HTML 4.01 Frameset

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">
  • WARN - Identical to HTML 4.01 Transitional

Conclusion

OK

  • XHTML 1.0 Strict
  • XHTML 1.1 (any)
  • HTML 4.01 Strict
  • HTML 5

WARN

  • XHTML 1.0 Transitional and Frameset
  • HTML 4.01 Transitional and Frameset
  • SVG
  • MathML

UNSUPPORTED

  • HTML 3 (or older)

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