sl0ppty: minimise a pane into a strip along the bottom

A pane can be put away: it leaves the layout, becomes one row at the bottom of
the tab, and keeps running. The panes it leaves behind take the space back.
Clicking its row brings it back.

Minimised is intent, so it sits beside the weight on the node rather than with
the rect and the collapsed flag — and layout_node has to be careful not to
clear it the way it clears those, or every frame would undo it. That is the
only sharp edge in the whole thing and it has a comment.

Everything else fell out of rules that already existed. A split divides among
the children that still want space, so a split with one live child is that
child, exactly as a split with one child already was. A minimised leaf returns
from layout_node before its rect is touched, which also skips the floor check —
a pane that is one row by request is not a pane that failed to fit. And the row
itself is drawn by the same code as a collapsed header, because it is the same
thing: a pane you can see the name of and click.

Restoring is not a verb. A focused pane is never minimised, checked once a
frame, so every route that ends with the pane focused restores it — clicking
the row, the control API, and anything added later that moves focus without
knowing minimising exists.

In a tab that has flattened into a list, minimising has no effect at all, which
is what was asked for and also what falls out: every pane down there is already
a row, so there is no second thing for it to be. The strip is not reserved when
it would leave too little above it to be worth looking at; the tab flattens
instead, and arrives at the same place.

Minimising the last visible pane is refused with a toast. A tab showing nothing
has no way back that can be discovered from the tab, and it is not a state
worth being able to reach by accident.

The frame's third button costs another three columns, which is why they are
drawn right to left and stop when they run out: a narrow pane keeps close and
zoom, and loses minimise first.

1 files changed, 189 insertions, 0 deletions

diff --git a/tests/test_minimize.py b/tests/test_minimize.py
new file mode 100644
index 0000000..9582ca2
--- /dev/null
+++ b/tests/test_minimize.py
@@ -0,0 +1,189 @@
+#!/usr/bin/env python3
+"""Putting a pane away.
+
+A minimised pane leaves the layout and sits in a strip along the bottom, one
+row each, still running. It is intent rather than a derived state, so the
+things worth checking are the same ones zoom needed: that it survives the
+layout being recomputed, that there is always a way back, and that it does not
+invent a state with nothing on screen.
+"""
+import os
+import sys
+import tempfile
+
+from harness import Session, check, report
+
+SH = ["/bin/sh", "-c", 'printf "\\033]2;p\\007"; stty raw -echo; cat']
+
+
+def cfg(text):
+    f = tempfile.NamedTemporaryFile("w", suffix=".kdl", delete=False)
+    f.write(text)
+    f.close()
+    return f.name
+
+
+def here(s):
+    """Panes of the current tab; another tab's are not laid out."""
+    active = [t["index"] for t in s.tabs() if t["active"]][0]
+    return [p for p in s.panes() if p["tab"] == active]
+
+
+def strip(s):
+    return [p for p in here(s) if p["h"] == 1]
+
+
+def open_panes(s):
+    return [p for p in here(s) if p["h"] > 1]
+
+
+def test_minimising_moves_a_pane_to_the_strip():
+    with Session(SH, cols=90, rows=20) as s:
+        s.settle(20)
+        s.api("split", dir="cols")
+        s.settle(20)
+        before = sorted(p["w"] for p in open_panes(s))
+
+        s.send(r"\x01m")
+        s.settle(20)
+        check("one pane is now a single row", len(strip(s)) == 1,
+              str(here(s)))
+        check("and the other still has the tab", len(open_panes(s)) == 1,
+              str(here(s)))
+        check("which is wider than it was, having taken the space back",
+              open_panes(s)[0]["w"] > max(before), str(here(s)))
+
+        row = strip(s)[0]
+        rest = open_panes(s)[0]
+        check("the strip sits under the layout, not in it",
+              row["y"] > rest["y"] + rest["h"] - 1, f"{row} vs {rest}")
+        check("and spans the width", row["w"] == rest["w"], str(here(s)))
+
+
+def test_clicking_the_row_brings_it_back():
+    with Session(SH, cols=90, rows=20) as s:
+        s.settle(20)
+        s.api("split", dir="cols")
+        s.settle(20)
+        layout_before = sorted((p["x"], p["w"]) for p in open_panes(s))
+
+        s.send(r"\x01m")
+        s.settle(20)
+        row = strip(s)[0]
+        s.click(row["x"] + 4, row["y"])
+        s.settle(20)
+        check("clicking the row restores the pane", strip(s) == [], str(here(s)))
+        check("and the layout is the one it left",
+              sorted((p["x"], p["w"]) for p in open_panes(s)) == layout_before,
+              str(here(s)))
+
+
+def test_focusing_it_by_any_route_brings_it_back():
+    """Restoring is not a special verb: a focused pane is never minimised, and
+    that is checked once a frame rather than at each place focus can move."""
+    with Session(SH, cols=90, rows=20) as s:
+        s.settle(20)
+        s.api("split", dir="cols")
+        s.settle(20)
+        s.send(r"\x01m")
+        s.settle(20)
+        gone = strip(s)[0]["id"]
+
+        s.api("focus", id=gone)
+        s.settle(20)
+        check("focusing it over the control API restores it",
+              strip(s) == [], str(here(s)))
+
+
+def test_it_will_not_leave_the_tab_empty():
+    with Session(SH, cols=90, rows=20) as s:
+        s.settle(20)
+        check("one pane to start", len(here(s)) == 1, str(here(s)))
+        s.send(r"\x01m")
+        s.settle(20)
+        check("minimising the only pane is refused", strip(s) == [],
+              str(here(s)))
+        check("and it says why", "nothing else" in s.snapshot().screen(),
+              repr(s.snapshot().screen()[-200:]))
+
+        s.api("split", dir="cols")
+        s.settle(20)
+        s.send(r"\x01m")
+        s.settle(20)
+        check("with two, one can go", len(strip(s)) == 1, str(here(s)))
+        s.send(r"\x01m")
+        s.settle(20)
+        check("but the last one standing cannot", len(strip(s)) == 1,
+              str(here(s)))
+
+
+def test_the_button_minimises_that_pane():
+    with Session(SH, cols=90, rows=20) as s:
+        s.settle(20)
+        s.api("split", dir="cols")
+        s.settle(20)
+        target = here(s)[0]["id"]
+        b = [h for h in s.snapshot().hits
+             if h["action"] == f"minimize:{target}"]
+        check("a pane's frame carries a minimise button", len(b) == 1, str(b))
+        if not b:
+            return
+        s.click(b[0]["x"] + 1, b[0]["y"])
+        s.settle(20)
+        check("clicking it puts that pane away",
+              [p["id"] for p in strip(s)] == [target], str(here(s)))
+
+
+def test_it_has_no_say_once_the_tab_is_a_list():
+    """Down there every pane is a row already, so being minimised is not a
+    different thing to be -- which is the whole reason it costs nothing."""
+    with Session(SH, cols=90, rows=20) as s:
+        s.settle(20)
+        s.api("split", dir="cols")
+        s.settle(20)
+        s.send(r"\x01m")
+        s.settle(20)
+        check("one minimised, one open", len(strip(s)) == 1, str(here(s)))
+
+        s.resize(26, 20)          # narrow enough that the tab flattens
+        s.settle(20)
+        rows = here(s)
+        check("the tab is a list", any(p["hidden"] for p in rows), str(rows))
+        check("and the minimised pane is just another row in it",
+              len([p for p in rows if p["h"] == 1]) == len(rows) - 1,
+              str(rows))
+
+        s.resize(90, 20)
+        s.settle(20)
+        check("coming back, it is minimised again and not lost",
+              len(strip(s)) == 1 and len(open_panes(s)) == 1, str(here(s)))
+
+
+def test_zoom_hides_the_strip():
+    with Session(SH, cols=90, rows=20) as s:
+        s.settle(20)
+        s.api("split", dir="cols")
+        s.api("split", dir="rows")
+        s.settle(20)
+        s.send(r"\x01m")
+        s.settle(20)
+        check("a strip to start", len(strip(s)) == 1, str(here(s)))
+        s.send(r"\x01z")
+        s.settle(20)
+        check("zooming shows one pane and nothing else, strip included",
+              len([p for p in here(s) if p["w"] > 1]) == 1, str(here(s)))
+        s.send(r"\x01z")
+        s.settle(20)
+        check("and unzooming gives the strip back", len(strip(s)) == 1,
+              str(here(s)))
+
+
+if __name__ == "__main__":
+    test_minimising_moves_a_pane_to_the_strip()
+    test_clicking_the_row_brings_it_back()
+    test_focusing_it_by_any_route_brings_it_back()
+    test_it_will_not_leave_the_tab_empty()
+    test_the_button_minimises_that_pane()
+    test_it_has_no_say_once_the_tab_is_a_list()
+    test_zoom_hides_the_strip()
+    sys.exit(report())