Add --header-border=inline / --header-lines-border=inline / --footer-border=inline

Adds a new BorderShape, BorderInline, accepted as a value for
--header-border, --header-lines-border, and --footer-border. When the
surrounding --list-border has both top and bottom horizontals (rounded,
sharp, bold, double, thinblock, block, horizontal), the corresponding
section is rendered inside the list frame separated from the list
content by a horizontal line whose endpoints join the list border as
T-junctions. Without a compatible list border, the shape falls back to
BorderLine.

Supports:
  - All three layouts (default, reverse, reverse-list).
  - Any combination of the three inline sections, producing stacked
    separators.
  - --header-label and --footer-label rendered on their separator row.
  - Section colors: the portion of the list frame adjacent to an inline
    section (left/right verticals on the section's content rows plus the
    outer top/bottom edge + corners when the section is at the edge)
    inherits the section's --color *-border and *-bg, giving each section
    a uniform color block. The separator itself carries the section's
    colors since it acts as the section's inner edge.
  - When --color header-border / --color footer-border is not set, the
    inline section inherits --color list-border so the default palette
    stays coherent.
  - thinblock / block styles pick the horizontal char (top vs bottom)
    based on which side of the list content the separator sits on, so
    the thin line visually hugs the list content.

Rejects combinations that do not make sense:
  - --input-border=inline / --list-border=inline / --preview-border=inline
  - --header-first + (--header-border=inline | --header-lines-border=inline)
  - --header-border=inline with a non-inline --header-lines-border
    (inline has to propagate inward toward the list content).

test/lib/common.rb

@@ -130,6 +130,66 @@ class Tmux
     go(%W[capture-pane -p -J -t #{win}]).map(&:rstrip).reverse.drop_while(&:empty?).reverse
   end
 
+  # 3-bit ANSI bg code (40..47) -> color name used in --color options.
+  BG_NAMES = %w[black red green yellow blue magenta cyan white].freeze
+
+  # Parse `tmux capture-pane -e` output into per-row bg ranges. Each row is an
+  # array of [col_start, col_end, bg] tuples where bg is one of:
+  #   'default'
+  #   'red' / 'green' / 'blue' / ... (3-bit names)
+  #   'bright-red' / ...             (bright variants)
+  #   '256:<n>'                      (256-color fallback)
+  # ANSI state persists across rows, matching real terminal behavior.
+  def bg_ranges
+    raw = go(%W[capture-pane -p -J -e -t #{win}])
+    bg = 'default'
+    raw.map do |row|
+      cells = []
+      i = 0
+      len = row.length
+      while i < len
+        c = row[i]
+        if c == "\e" && row[i + 1] == '['
+          j = i + 2
+          j += 1 while j < len && row[j] != 'm'
+          parts = row[i + 2...j].split(';')
+          k = 0
+          while k < parts.length
+            p = parts[k].to_i
+            case p
+            when 0, 49 then bg = 'default'
+            when 40..47 then bg = BG_NAMES[p - 40]
+            when 100..107 then bg = "bright-#{BG_NAMES[p - 100]}"
+            when 48
+              if parts[k + 1] == '5'
+                bg = "256:#{parts[k + 2]}"
+                k += 2
+              elsif parts[k + 1] == '2'
+                bg = "rgb:#{parts[k + 2]}:#{parts[k + 3]}:#{parts[k + 4]}"
+                k += 4
+              end
+            end
+            k += 1
+          end
+          i = j + 1
+        else
+          cells << bg
+          i += 1
+        end
+      end
+      ranges = []
+      start = 0
+      cells.each_with_index do |b, idx|
+        if idx.positive? && b != cells[idx - 1]
+          ranges << [start, idx - 1, cells[idx - 1]]
+          start = idx
+        end
+      end
+      ranges << [start, cells.length - 1, cells.last] unless cells.empty?
+      ranges
+    end
+  end
+
   def until(refresh = false, timeout: DEFAULT_TIMEOUT)
     lines = nil
     begin

test/test_layout.rb

@@ -1392,5 +1392,159 @@ class TestLayout < TestInteractive
                     input: "(printf 'Xaa\\nYbb\\nZcc\\n'; seq 5)",
                     clicks: clicks)
     end
+
+    # Inline header inside a rounded list border.
+    define_method(:"test_click_header_border_inline_#{slug}") do
+      opts = %(--layout=#{layout} --style full --header $'Aaa\\nBbb\\nCcc' --header-border=inline)
+      verify_clicks(kind: :header, opts: opts, input: 'seq 5', clicks: HEADER_CLICKS)
+    end
+
+    # Inline header inside a horizontal list border (top+bottom only, no T-junctions).
+    define_method(:"test_click_header_border_inline_horizontal_list_#{slug}") do
+      opts = %(--layout=#{layout} --style full --list-border=horizontal --header $'Aaa\\nBbb\\nCcc' --header-border=inline)
+      verify_clicks(kind: :header, opts: opts, input: 'seq 5', clicks: HEADER_CLICKS)
+    end
+
+    # Inline header-lines inside a rounded list border.
+    define_method(:"test_click_header_lines_border_inline_#{slug}") do
+      clicks_hl = if layout == 'default'
+                    [%w[Xaa 3], %w[Ybb 2], %w[Zcc 1]]
+                  else
+                    [%w[Xaa 1], %w[Ybb 2], %w[Zcc 3]]
+                  end
+      opts = %(--layout=#{layout} --style full --header-lines 3 --header-lines-border=inline)
+      verify_clicks(kind: :header, opts: opts,
+                    input: "(printf 'Xaa\\nYbb\\nZcc\\n'; seq 5)",
+                    clicks: clicks_hl)
+    end
+
+    # Inline footer inside a rounded list border.
+    define_method(:"test_click_footer_border_inline_#{slug}") do
+      opts = %(--layout=#{layout} --style full --footer $'Foo\\nBar\\nBaz' --footer-border=inline)
+      verify_clicks(kind: :footer, opts: opts, input: 'seq 5',
+                    clicks: [%w[Foo 1], %w[Bar 2], %w[Baz 3]])
+    end
+  end
+
+  # An inline section requesting far more rows than the terminal can fit must not
+  # break the layout. The list frame must still render inside the pane with both
+  # corners visible and the prompt line present.
+  def test_inline_header_lines_oversized
+    tmux.send_keys %(seq 10000 | #{FZF} --style full --header-border inline --header-lines 9999), :Enter
+    tmux.until { |lines| lines.any_include?(%r{ [0-9]+/[0-9]+}) }
+    lines = tmux.capture
+    # Rounded (light) and sharp (tcell) default border glyphs.
+    top_corners = /[╭┌]/
+    bottom_corners = /[╰└]/
+    assert(lines.any? { |l| l.match?(top_corners) }, "list frame top missing: #{lines.inspect}")
+    assert(lines.any? { |l| l.match?(bottom_corners) }, "list frame bottom missing: #{lines.inspect}")
+    assert(lines.any? { |l| l.include?('>') }, "prompt missing: #{lines.inspect}")
+    tmux.send_keys 'Escape'
+  end
+
+  # A non-inline section that consumes all available rows must still render without
+  # crashing when another section is inline but has no budget. The inline section's
+  # content is clipped to 0 but the layout proceeds.
+  def test_inline_footer_starved_by_non_inline_header
+    tmux.send_keys %(seq 10000 | #{FZF} --style full --footer-border inline --footer "$(seq 1000)" --header "$(seq 1000)"), :Enter
+    tmux.until { |lines| lines.any_include?(%r{ [0-9]+/[0-9]+}) }
+    lines = tmux.capture
+    assert(lines.any? { |l| l.include?('>') }, "prompt missing: #{lines.inspect}")
+    tmux.send_keys 'Escape'
+  end
+
+  # Without a line-drawing --list-border, --header-border=inline must silently
+  # fall back to the `line` style (documented behavior).
+  def test_inline_falls_back_without_list_border
+    tmux.send_keys %(seq 5 | #{FZF} --list-border=none --header HEADER --header-border=inline), :Enter
+    tmux.until { |lines| lines.any_include?(%r{ [0-9]+/[0-9]+}) }
+    lines = tmux.capture
+    assert(lines.any? { |l| l.include?('HEADER') }, "header missing: #{lines.inspect}")
+    # Neither list frame corners (rounded/sharp) nor T-junction runes appear,
+    # since we've fallen back to a plain line separator.
+    assert(lines.none? { |l| l.match?(/[╭╮╰╯┌┐└┘├┤]/) }, "unexpected frame glyphs: #{lines.inspect}")
+    tmux.send_keys 'Escape'
+  end
+
+  # Invalid inline combinations must be rejected at startup.
+  def test_inline_rejected_on_unsupported_options
+    [
+      ['--border=inline', 'inline border is only supported'],
+      ['--list-border=inline', 'inline border is only supported'],
+      ['--input-border=inline', 'inline border is only supported'],
+      ['--preview-window=border-inline --preview :', 'invalid preview window option: border-inline'],
+      ['--header-first --header-border=inline', '--header-first is not compatible'],
+      ['--header-first --header-lines-border=inline --header-lines=1', '--header-first is not compatible'],
+      ['--header-border=inline --header-lines-border=sharp --header-lines=1',
+       '--header-border=inline requires --header-lines-border to be inline or unset']
+    ].each do |args, expected|
+      output = `#{FZF} #{args} < /dev/null 2>&1`
+      refute_equal 0, $CHILD_STATUS.exitstatus, "expected non-zero exit for: #{args}"
+      assert_includes output, expected, "wrong error for: #{args}"
+    end
+  end
+
+  private
+
+  # Count rows whose entire width is a single `color` range.
+  def count_full_rows(ranges_by_row, color)
+    ranges_by_row.count { |r| r.length == 1 && r[0][2] == color }
+  end
+
+  # Wait until `tmux.bg_ranges` has at least `count` fully-`color` rows; return them.
+  def wait_for_full_rows(color, count)
+    ranges = nil
+    tmux.until do |_|
+      ranges = tmux.bg_ranges
+      count_full_rows(ranges, color) >= count
+    end
+    ranges
+  end
+
+  public
+
+  # Inline header's entire section (outer edge + content-row verticals + separator)
+  # carries the header-bg color; list rows below carry list-bg.
+  def test_inline_header_bg_color
+    tmux.send_keys %(seq 5 | #{FZF} --list-border --reverse --header HEADER --header-border=inline --color=bg:-1,header-border:white,list-border:white,header-bg:red,list-bg:green), :Enter
+    tmux.until { |lines| lines.any_include?(%r{ [0-9]+/[0-9]+}) }
+    # 3 fully-red rows: top edge, header content, separator.
+    ranges = wait_for_full_rows('red', 3)
+    assert_equal_org(3, count_full_rows(ranges, 'red'))
+    # List rows below (>=5) are fully green.
+    assert_operator count_full_rows(ranges, 'green'), :>=, 5
+    tmux.send_keys 'Escape'
+  end
+
+  # Regression: when --header-lines-border=inline is the only inline section
+  # (no --header-border), the section must still use header-bg, not list-bg.
+  def test_inline_header_lines_bg_without_main_header
+    tmux.send_keys %(seq 5 | #{FZF} --list-border --reverse --header-lines 2 --header-lines-border=inline --color=bg:-1,header-border:white,list-border:white,header-bg:red,list-bg:green), :Enter
+    tmux.until { |lines| lines.any_include?(%r{ [0-9]+/[0-9]+}) }
+    # Top edge + 2 content rows + separator = 4 fully-red rows.
+    ranges = wait_for_full_rows('red', 4)
+    assert_equal_org(4, count_full_rows(ranges, 'red'))
+    tmux.send_keys 'Escape'
+  end
+
+  # Inline footer's entire section carries footer-bg; list rows above carry list-bg.
+  def test_inline_footer_bg_color
+    tmux.send_keys %(seq 5 | #{FZF} --list-border --footer FOOTER --footer-border=inline --color=bg:-1,footer-border:white,list-border:white,footer-bg:blue,list-bg:green), :Enter
+    tmux.until { |lines| lines.any_include?(%r{ [0-9]+/[0-9]+}) }
+    ranges = wait_for_full_rows('blue', 3)
+    assert_equal_org(3, count_full_rows(ranges, 'blue'))
+    tmux.send_keys 'Escape'
+  end
+
+  # The list-label's bg is swapped to match the adjacent inline section so it reads as
+  # part of the section frame rather than a list-colored island on a section-colored edge.
+  def test_list_label_bg_on_inline_section_edge
+    tmux.send_keys %(seq 5 | #{FZF} --list-border --reverse --header HEADER --header-border=inline --list-label=LL --color=bg:-1,header-border:white,list-border:white,header-bg:red,list-bg:green,list-label:yellow:bold), :Enter
+    tmux.until { |lines| lines.any_include?(%r{ [0-9]+/[0-9]+}) }
+    # The label sits on the header-owned top edge, so the entire row must be a
+    # single red run (no green breaks where the label cells are).
+    ranges = wait_for_full_rows('red', 3)
+    assert_operator count_full_rows(ranges, 'red'), :>=, 3
+    tmux.send_keys 'Escape'
   end
 end