Paint a body with context rows once, into its layer, and join it

joinBody replaces the second paint of a file body with compact tree-sitter
context rows: the body is painted once into its body layer (more rows than
the grid has) and the grid's body rows are copies of the layer's first
ones; the rail is the grid's alone, from its region. Which rows are context
rows is still decided by a text build before the paint, and a body without
them reuses that text and paints straight onto the grid: every other body
has no row the grid cannot show, so it gets no layer and no copy.

Each part now paints only its own rows. The tag paints the tag rows of
every pointer sweep that crosses them (the select sweep in the tag's
colours, the look-hover affordance over it, a middle or right sweep over
both in its button's tint), which the body used to paint over the tag on
the grid alone; the body paints only body rows, and a select sweep begun on
the tag marks the body rows it crossed before the text is laid down, as it
did. Grid and layers agree, the snapshot goldens are byte-identical, and a
test checks the joined grid rows and caret against a plain paint of the
same body with the tag on top and at the bottom. The GUI goldens gain a
terminal pane scene.

2 files changed, 9 insertions, 0 deletions

diff --git a/test/gui-goldens.txt b/test/gui-goldens.txt
index 73aa1f86..e52155a3 100644
--- a/test/gui-goldens.txt
+++ b/test/gui-goldens.txt
@@ -14,3 +14,4 @@
 14-theme-ink 6e733d4212373c90b860b2e41102ced8719b07480591b5da3905267c8358db18
 15-theme-acme-light e099dc1a351de8efa63ecd0ec0899636ea31b722a945eb40137a18abd87a82e2
 16-debug e97ce74b7a3d4a08f6a529b1f0de111d62e5532c829a6b1633b966dd45218f55
+17-terminal 304a84d1ef871f581d0a3fade9bc1acdcc87a3612c607548ab0d2851871753ee
diff --git a/test/gui_golden.py b/test/gui_golden.py
index 1252014c..327911cc 100644
--- a/test/gui_golden.py
+++ b/test/gui_golden.py
@@ -188,6 +188,14 @@ def run(args):
         scene('15-theme-acme-light')
         client.write('/ctl', b'Debug\n')
         scene('16-debug')
+        client.write('/ctl', b'Debug\n')
+        # A terminal pane: raw rows, ANSI colours, a hidden prompt.
+        before = set(panes(client))
+        client.write(f'/pane/{first}/exec', b'Tty\n')
+        terminal = require(wait_for(lambda: next((s for s in panes(client) if s not in before), None)), 'Tty missing')
+        client.write(f'/pane/{terminal}/pty/data', b"PS1='$ '; clear; printf '\\033[1;36mcolour\\033[0m plain \\033[32mgreen\\033[0m\\n'\r")
+        require(wait_for(lambda: b'green' in client.read(f'/pane/{terminal}/body')), 'terminal output missing')
+        scene('17-terminal')
     lines = ''.join(f'{label} {digest}\n' for label, digest in results)
     if args.update:
         GOLDENS.write_text(lines)