Footnote area size problem

[MurakamiShinyu]

The spec CSS Generated Content for Paged Media Module Level 3 §2.4.2. Size of the footnote area says:

The max-height property on the footnote area limits the size of this area, unless the page contains only footnotes (as may happen on the last page of a document).

Since it is undesirable for a page to consist only of footnotes, user agents may set a default max-height value on the footnote area.

I found that the current implementation of Vivliostyle.js does not support this spec very well.

Test case: footnote-area-max-height.html

Test with Vivliostyle Viewer v2.41.0:

• https://vivliostyle.github.io/viewer/v2.41.0/#src=https://gist.githubusercontent.com/MurakamiShinyu/85d0e3eb9f28fdff9241a507f63b8014/raw/ea653524c66640cb4263b3f48a3b16c5ae539fdc/footnote-area-max-height.html

Problems:

• Footnote areas are not properly positioned, not at the bottom of the page but at the top of the page leaving a large blank space at the bottom of the page or body text below the footnote area.

Test with Vivliostyle Viewer canary (after PR #1877 is merged):

• https://vivliostyle.vercel.app/#src=https://gist.githubusercontent.com/MurakamiShinyu/85d0e3eb9f28fdff9241a507f63b8014/raw/ea653524c66640cb4263b3f48a3b16c5ae539fdc/footnote-area-max-height.html

Problem:

• The footnote should start at Page 1 (since PR fix: Enable footnote fragmentation across pages #1877 resolved the footnote fragmentation issue), but the footnote is defferred to the next page.

One more problem:

• box-sizing: border-box is not working properly for footnote areas.
  • Test case: footnote-area-max-height-box-sizing.html
  • Test with Vivliostyle Viewer canary:
    • https://vivliostyle.vercel.app/#src=https://gist.githubusercontent.com/MurakamiShinyu/85d0e3eb9f28fdff9241a507f63b8014/raw/ea653524c66640cb4263b3f48a3b16c5ae539fdc/footnote-area-max-height-box-sizing.html