acme looks like acme; every theme gets acme's button, scroll column and 2px rules

acme takes plan9port's own colours (acme.c iconinit, draw.h): selections
#eeee9e in the body and #9eeeee in the tag, black ink; exec and look sweeps
#aa0000 and #006600, white ink; a #99994c scrollbar under a #ffffea thumb;
black rules; a #8888cc tag/body rule and column button.

Every theme: the grip is acme's button, its tag row's full height, in one
scroll column with the scrollbar (rail_px, 12 at a 17px tagline, scaled,
times GripWidth, a percent, default 150; same x0/x1 to the pixel):
focused clean = solid box; focused dirty = box_dirty filled to a box ring
(acme's modbutton); unfocused clean = a box_border ring round the tag's
ground; unfocused dirty = box_dirty a pixel inside that ring. The grid, which
has no ring, marks dirty with a bold * on box_dirty in the grip's second cell
and fills an unfocused grip halfway to its ring. Regions carry a dirty flag.
Column buttons are the same shape, solid. 2px rules between columns and
stacked panes (inside the tag band's slack), none at the window edge; a 1px
tag/body rule halfway between tag and page.

Theme data: tag_sel_bg, sweep_bg/fg, tag_rule, rule_px, rail_px, box_border,
box_dirty. Chrome: rule_px, tag_rule, rail_px, grip_border, grip_focus_ring;
a comptime guard on Chrome's layout forces a wire bump once v8 ships.
Structural rules are exempt from the focus-indicator rule (docs/effects.md).

Tests: acme widths; stacked rule in the slack at two tagline sizes; every
grip-column pixel is band, button, ring or rule, and the button shares the
scrollbar's x0/x1 (4 metrics x top/bottom x focus x dirty); the four grip
states distinct in every native theme with a non-colour dirty cue in the
grid; wire round-trip of the new fields.

Shared files: src/colors.zig, src/surface.zig, src/body_layer.zig,
src/tagline.zig, src/detached/wire.zig, docs/themes.md, docs/config.md,
docs/effects.md, 21 snapshot goldens (the grip cells only),
test/gui-goldens.txt.

Motion flavours differ by design, and drive notice drops and pane moves

1 files changed, 15 insertions, 0 deletions

diff --git a/src/surface.zig b/src/surface.zig
index f16993a8..bc0a019d 100644
--- a/src/surface.zig
+++ b/src/surface.zig
@@ -356,6 +356,8 @@ pub const Region = struct {
     rect: layout.Rect,
     /// The pane or column has the keyboard's focus.
     active: bool = false,
+    /// A grip's pane has changes it has not saved.
+    dirty: bool = false,
     /// A rail's thumb: rows from the rail's top, and how many. Zero rows is
     /// a rail with no thumb (an image). A native PDF's thumb is measured in
     /// document pixels and filled in by Pdf.draw while it paints, so read
@@ -403,6 +405,19 @@ pub const Chrome = struct {
     sel_bg: [3]u8 = .{ 0, 0, 0 },
     /// How a lifted part stands off the page (config.Runtime.LiftStyle).
     lift_style: u8 = 0,
+    /// Rule width in pixels (colors.Theme.rule_px).
+    rule_px: u8 = 2,
+    /// The ring round a grip, acme's button: unfocused, and focused.
+    grip_border: [3]u8 = .{ 0, 0, 0 },
+    grip_focus_ring: [3]u8 = .{ 0, 0, 0 },
+    /// A dirty pane's button fill.
+    grip_dirty: [3]u8 = .{ 0, 0, 0 },
+    /// The rule between a pane's tag and its body; null is halfway between
+    /// the tag's ground and the page the shell actually draws.
+    tag_rule: ?[3]u8 = null,
+    /// The scroll column's width, button and scrollbar alike, in pixels at
+    /// a 17px tagline (acme's 12 at its font); a pixel shell scales it.
+    rail_px: u8 = 12,
 };
 
 /// The canonical interface: what a frame of pardes IS. The tty shell writes