tabs: air before the new-tab button, and the option to do without it

The `+` is the one entry in the strip that does not mean "go here", and it
sits at the end of a list where every other entry does. Flush against them it
is what you hit when you meant the last tab -- most easily in a sidebar, where
the target is the full width of the row and the pointer only has to be one row
low. newtab_pad is the nothing in between: blank rows in a sidebar, blank
columns on top, one by default, which is enough to make the slip a miss.

It is paint rather than layout, like tab_bar_pad: the panes' rectangle is the
same at 0 as at 5, so tuning it repaints without reflowing anyone. And it is
given up before the button is -- a strip short of room drops the spacing one
cell at a time and still draws what the spacing was protecting, because
spacing must never cost you the thing it spaces.

newtab_button false removes the button outright, for people who make tabs from
the keyboard and would rather have the row (or the columns) back. Only the
place to click it goes: the chord and the palette entry still work. Setting
newtab_mark "" already did this by omission; this says it on purpose, and says
it in --dump-config.

1 files changed, 94 insertions, 11 deletions

diff --git a/tests/test_tab_bar.py b/tests/test_tab_bar.py
index 85b6c48..1fb6609 100644
--- a/tests/test_tab_bar.py
+++ b/tests/test_tab_bar.py
@@ -33,6 +33,10 @@ BARE = _cfg(f'tab_bar_side "left"\ntab_bar_width {W}\ntab_bar_chrome false\n')
 # is one edit here rather than thirty coordinates below.
 CX, CW, Y0 = 1, W - 2, 2
 
+# The default newtab_pad: one blank row between the last tab and the `+`, so
+# a pointer one row low misses the button instead of making a tab.
+NT_PAD = 1
+
 SH = ["/bin/sh", "-c", "stty raw -echo; cat"]
 
 
@@ -56,8 +60,13 @@ def test_left_sidebar_reserves_columns():
             str(snap.hit_at(CX + CW - 1, Y0)),
         )
         check(
-            "the + sits on the row after the last tab",
-            snap.hit_at(CX, Y0 + 1) == "newtab",
+            "the + sits below the last tab, a pad row clear of it",
+            snap.hit_at(CX, Y0 + 1 + NT_PAD) == "newtab",
+            str(snap.hit_at(CX, Y0 + 1 + NT_PAD)),
+        )
+        check(
+            "and the air between them is nobody's target",
+            snap.hit_at(CX, Y0 + 1) is None,
             str(snap.hit_at(CX, Y0 + 1)),
         )
         p = s.pane(0)
@@ -73,7 +82,8 @@ def test_left_sidebar_reserves_columns():
 def test_sidebar_rows_click_like_the_strip():
     with Session(SH, cols=90, rows=20, config=LEFT) as s:
         s.settle(30)
-        s.click(CX, Y0 + 1)  # the + row: a new tab, which becomes the active one
+        # the + row: a new tab, which becomes the active one
+        s.click(CX, Y0 + 1 + NT_PAD)
         s.until(lambda _: len(s.tabs()) == 2)
         check("the + row makes a tab", len(s.tabs()) == 2, str(len(s.tabs())))
         check("...and it is the one you are in", s.tabs()[1]["active"], str(s.tabs()))
@@ -290,8 +300,8 @@ def test_status_cap_spends_its_last_row_on_the_ellipsis():
         )
         check(
             "and only the cap's rows were spent",
-            snap.hit_at(CX, Y0 + 2) == "newtab",
-            str(snap.hit_at(CX, Y0 + 2)),
+            snap.hit_at(CX, Y0 + 2 + NT_PAD) == "newtab",
+            str(snap.hit_at(CX, Y0 + 2 + NT_PAD)),
         )
 
 
@@ -405,12 +415,83 @@ def test_the_sidebar_button_says_what_it_does():
     with Session(SH, cols=90, rows=20, config=LEFT) as s:
         s.settle(40)
         snap = s.snapshot()
-        row = _row(snap, Y0 + 1)
+        row = _row(snap, Y0 + 1 + NT_PAD)
         check("a row of its own spells the verb out", "new tab" in row, repr(row))
         check(
             "and the whole row is the target, like a tab's",
-            snap.hit_at(CX + CW - 1, Y0 + 1) == "newtab",
-            str(snap.hit_at(CX + CW - 1, Y0 + 1)),
+            snap.hit_at(CX + CW - 1, Y0 + 1 + NT_PAD) == "newtab",
+            str(snap.hit_at(CX + CW - 1, Y0 + 1 + NT_PAD)),
+        )
+
+
+def test_newtab_pad_is_the_air_before_the_button():
+    """The button is the one row in the list that does not mean "go here", and
+    a sidebar tab is a target the full width of the strip: flush against the
+    tabs, a pointer one row low makes a tab instead of switching to one. The
+    pad is that air, and 0 gives the old flush button back."""
+    n = 3
+    padded = _cfg(f'tab_bar_side "left"\ntab_bar_width {W}\nnewtab_pad {n}\n')
+    with Session(SH, cols=90, rows=20, config=padded) as s:
+        s.settle(30)
+        snap = s.snapshot()
+        check(
+            "the air is not a target",
+            all(snap.hit_at(CX, Y0 + 1 + k) is None for k in range(n)),
+            str([snap.hit_at(CX, Y0 + 1 + k) for k in range(n)]),
+        )
+        check(
+            "the button is that many rows down",
+            snap.hit_at(CX, Y0 + 1 + n) == "newtab",
+            str(snap.hit_at(CX, Y0 + 1 + n)),
+        )
+        p = s.pane(0)
+        check(
+            "the pad is paint, not layout: panes keep their rows",
+            p["y"] <= 2,
+            str(p["y"]),
+        )
+
+    flush = _cfg(f'tab_bar_side "left"\ntab_bar_width {W}\nnewtab_pad 0\n')
+    with Session(SH, cols=90, rows=20, config=flush) as s:
+        s.settle(30)
+        snap = s.snapshot()
+        check(
+            "0 puts it straight under the last tab",
+            snap.hit_at(CX, Y0 + 1) == "newtab",
+            str(snap.hit_at(CX, Y0 + 1)),
+        )
+
+
+def test_newtab_button_false_removes_it_everywhere():
+    """The verb keeps working from the keyboard; only the place to click it
+    goes. A sidebar that is missing it has no `newtab` hit anywhere on it --
+    including as somewhere to drop a pane."""
+    off = _cfg(f'tab_bar_side "left"\ntab_bar_width {W}\nnewtab_button false\n')
+    with Session(SH, cols=90, rows=20, config=off) as s:
+        s.settle(30)
+        snap = s.snapshot()
+        check(
+            "no button on the sidebar",
+            all(h["action"] != "newtab" for h in snap.hits),
+            str([h for h in snap.hits if h["action"] == "newtab"]),
+        )
+        check(
+            "nor the word that spells it out",
+            all("new tab" not in snap.line(y) for y in range(20)),
+            repr([snap.line(y) for y in range(20) if "new tab" in snap.line(y)]),
+        )
+        s.api("new-tab")
+        s.until(lambda _: len(s.tabs()) == 2)
+        check("the verb still makes tabs", len(s.tabs()) == 2, str(len(s.tabs())))
+
+    top = _cfg("newtab_button false\n")
+    with Session(SH, cols=90, rows=20, config=top) as s:
+        s.settle(30)
+        snap = s.snapshot()
+        check(
+            "and the top strip loses it too",
+            all(h["action"] != "newtab" for h in snap.hits),
+            str([h for h in snap.hits if h["action"] == "newtab"]),
         )
 
 
@@ -419,14 +500,14 @@ def test_a_narrow_sidebar_keeps_the_bare_mark():
     with Session(SH, cols=90, rows=20, config=narrow) as s:
         s.settle(40)
         snap = s.snapshot()
-        row = snap.line(Y0 + 1)[CX : CX + 8]
+        row = snap.line(Y0 + 1 + NT_PAD)[CX : CX + 8]
         check(
             "no room for the word, so it is not said", "new tab" not in row, repr(row)
         )
         check(
             "...but the button is still there",
-            snap.hit_at(CX, Y0 + 1) == "newtab",
-            str(snap.hit_at(CX, Y0 + 1)),
+            snap.hit_at(CX, Y0 + 1 + NT_PAD) == "newtab",
+            str(snap.hit_at(CX, Y0 + 1 + NT_PAD)),
         )
 
 
@@ -492,6 +573,8 @@ if __name__ == "__main__":
     test_compact_shares_its_lines_with_the_ring()
     test_chrome_false_gives_the_columns_back()
     test_the_sidebar_button_says_what_it_does()
+    test_newtab_pad_is_the_air_before_the_button()
+    test_newtab_button_false_removes_it_everywhere()
     test_a_narrow_sidebar_keeps_the_bare_mark()
     test_the_strip_keeps_its_bare_mark()
     test_narrow_terminal_falls_back_to_top()