Vertical-rl (Japanese/Chinese vertical) books read top-to-bottom with
columns progressing right-to-left, but getDirection only derived rtl from
the horizontal dir/direction, which stays ltr for these books. As a result
viewSettings.rtl was false and the reading ruler laid columns out
left-to-right, advancing the band the wrong way (reverse reading order).
Treat writing-mode: vertical-rl as RTL in getDirection so vertical-rl runs
through the same rtl paths that horizontal-rtl already uses: the reading
ruler coordinate mapping, page-turn tap mapping, footer navigation, and the
progress bar. Page-turn taps for these books now follow the vertical-rl
convention (tap left to go forward), matching horizontal-rtl behavior.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Huang Xin
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