#2947 fixed the fade by drawing a dimmed layer inside a single opacity layer,
but left no regression test for the tone: where a header table's borders cross,
a crossed or shared rule would quietly come out darker than a rule that is not
drawn on top of anything, and the undimmed view and the PDF export would not
agree with the screen.
The test renders the same page with the header dimmed and undimmed and checks
three rules: the darkest pixel at a crossing of a cell's top and left rules,
the darkest pixel on a border two neighbouring cells share, and one on an
outer border well clear of both. With the fade done as one layer, the
crossing and the shared border keep the tone of an isolated rule; measured
against a clean full-strength render, the dimmed tone is 0.45 of the
background, not 0.45 squared.
The pane drew each heading with `Button::selectable(..).truncate()`, so a heading wider than the
pane ended in an ellipsis and its text had to be read from the hover tooltip. Word wraps the row
instead.
`nav_heading` now wraps: the button takes `Button::wrap()` and a minimum size of the available width
and one row, so the label continues on further lines inside the pane, the row grows with the text,
and the pane still keeps its width. The trailing grow atom still keeps the text flush left under its
parent (#1199). The hover tooltip goes with the ellipsis: nothing is hidden now, and a word wider
than the pane is broken by the wrap instead of overflowing.
The navigation test asserts the wrap instead of the ellipsis. For a heading well past the width and
for a single word wider than the pane, the label has more than one line, is not elided, stays inside
the pane, does not widen it, and takes a taller row than a one-line heading in the same pane.
`docs/ui-parity.md` and `ROADMAP.md` record the new behaviour.
Co-authored-by: Brandon Thomas <brandon@storyteller.ai>
Gabriel Matozo