sl0ppty: minimised panes get one row between them, and ASCII marks

The strip was a row per minimised pane, which let putting things away cost more
room than leaving them out. It is one row now, shaped like the tab strip and
for the same reason: a list of names you click to go somewhere. Three panes put
away leave the survivor exactly as tall as one did, and there is a test that
says so, because that is the whole change.

The panes on it are no longer laid out at all — the bar draws them, so they
have no rect. The row the bar occupies is worked out by the layout and stored,
rather than by the drawing working it out again from the same inputs; two
copies of that sum is how a click lands somewhere the eye did not.

The frame's marks are plain ASCII now. Spacing has been reported twice and the
cells were even both times: what is uneven is the glyphs. A light character
floating in a mostly empty cell hands that space to the gap beside it, and the
fix of picking heavier glyphs only holds for fonts I can see. ASCII has neither
that problem nor the double-width one, and "[]" and "][" say maximise and
restore about as clearly as anything.

That needed the button width measured rather than assumed. It was hardcoded to
three cells, which was fine while every mark was one character and silently
wrong the moment one was two: the mark would have been drawn over its
neighbour, and the neighbour's hit would have covered a cell it did not draw.

Also fixes a case that could not happen with a row each: when there is no room
for the bar at all, the tab flattens rather than leaving minimised panes with
no rect and nobody drawing them.

1 files changed, 5 insertions, 5 deletions

diff --git a/README.md b/README.md
index b203b2b..4f6b2cf 100644
--- a/README.md
+++ b/README.md
@@ -78,14 +78,14 @@ rewrites its title cannot undo it; clear the name and the pane goes back to the
 program's title. The name is only the title *text*: the rest of the top border
 is still the top edge, and still splits upward when clicked.
 
-**Zoom a pane** with `C-a z` or the `□` button in its top-right corner, and it
+**Zoom a pane** with `C-a z` or the `[]` button in its top-right corner, and it
 fills the tab until you put it back; the other panes keep running, they are
-just not drawn. `×` beside it closes the pane. `pane_buttons false` takes both
+just not drawn. `x` beside it closes the pane. `pane_buttons false` takes both
 buttons off without touching the keybindings.
 
-**Minimise a pane** with `C-a m` or the `▁` button and it leaves the layout for
-a strip along the bottom, one row each, still running — the panes it leaves
-behind take the space back. Click its row to bring it back. Once a tab is too
+**Minimise a pane** with `C-a m` or the `_` button and it leaves the layout for
+a single row along the bottom listing everything put away, still running — the panes it leaves
+behind take the space back. Click its name to bring it back. Once a tab is too
 small and has flattened into a list, being minimised means nothing: every pane
 is a row down there already.