The GUI draws in tiers from the regions; pane chrome moves with its pane

Stage 8 of docs/render-pipeline.md. The frame is drawn in groups: tier 0,
one per track in paint order (tiers 2 and 3), tier 4 (notices, then guides
and the debug box), tier 5 (bar cursors), each cells, images, decor. Decor
(rules, rails, thumbs, grip marks, spines, the workspace and column rules,
the bottom band, notice rules, bar cursors) is whole-pixel rects through
the new decor.frag over ui.vert, so it carries its track's transition and
clip. A closing pane's chrome comes from Surface.previous_regions.

Deleted: taglineBaseRgb, topbarPaneBorderHeight, bottomTaglinePresent,
frameChromeBg, cellBackgroundIs and the rail inference, paneGripCell's
scan, transient_on, PaintPlan. One cover map (coverFrame) is marked from
the layers and regions once a frame. New regions column, guide and debug;
Surface.chrome is the palette, carried in wire v8 (not shipped yet), so an
attached GUI draws the same chrome (test). A per-instance clip replaces the
vertical transition's scissor.

Goldens: 01-12 byte-identical. 13-17 differ only past the grid: the image
pass left its scissor at the grid's size, cutting rule ends, rail feet and
the bottom band in the leftover pixels whenever a picture was on screen.
16-debug now shows the debug box, which a context-row layer had hidden.
18-mid-transition is new: virtual clock (PARDES_TEST_CLOCK in the GUI),
PanelSlide Newcol with the picture, frame 6 of 12.

Also: the GUI sleeps when idle instead of polling every 16 ms, and a
minimized or occluded window sleeps through animation. Tracy 'gui frame
build' at 200x60: 992/1015 us median before, 989/987 us after.

Shared files touched: pardes.zig (one export), detached/client.zig,
detached/server.zig, detached/wire.zig (all additive), gui.zig. Not touched:
Messages.zig, mouse.zig, tagline.zig, colors.zig, tty.zig, host_io.zig,
dump.zig, exec.zig, panes.zig.

1 files changed, 14 insertions, 4 deletions

diff --git a/test/gui_golden.py b/test/gui_golden.py
index 327911cc..d97009c9 100644
--- a/test/gui_golden.py
+++ b/test/gui_golden.py
@@ -106,7 +106,9 @@ def run(args):
     display = Path(os.environ.get('WAYLAND_DISPLAY', 'wayland-0'))
     if not display.is_absolute():
         display = Path(os.environ.get('XDG_RUNTIME_DIR', '/run/user/%d' % os.getuid())) / display
-    inherited = {'PARDES_TEST': '1', 'PARDES_TEST_COLS': '120', 'PARDES_TEST_ROWS': '40',
+    # The virtual clock: a transition's frames are the same frames on any
+    # machine, so one partway through can be hashed too.
+    inherited = {'PARDES_TEST': '1', 'PARDES_TEST_CLOCK': '1', 'PARDES_TEST_COLS': '120', 'PARDES_TEST_ROWS': '40',
                  'PARDES_TEST_PAD': '7', 'PARDES_TEST_CAPTURE_DIR': str(root),
                  'SDL_VIDEODRIVER': 'wayland', 'WAYLAND_DISPLAY': str(display)}
     launch = ['-c', 'stty cols 120 rows 40; exec "$@"', name, str(args.binary.resolve()),
@@ -117,11 +119,12 @@ def run(args):
         first = require(wait_for(lambda: next((s for s, tag in panes(client).items()
                                                if 'shapes.zig' in tag), None)), 'source pane missing')
 
-        def scene(label):
-            results.append((label, settled(root)))
+        def scene(label, frame='latest.ppm'):
+            settled(root)
+            results.append((label, hashlib.sha256((root / frame).read_bytes()).hexdigest()))
             if args.keep:
                 args.keep.mkdir(parents=True, exist_ok=True)
-                shutil.copyfile(root / 'latest.ppm', args.keep / (label + '.ppm'))
+                shutil.copyfile(root / frame, args.keep / (label + '.ppm'))
             print(label, results[-1][1][:16], flush=True)
 
         def mouse(kind, button, x, y):
@@ -196,6 +199,13 @@ def run(args):
         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')
+        # Partway through a transition: the panes, the picture among them,
+        # sliding over for a new column, frame 6 of PanelSlide's 12. Its
+        # chrome slides with each pane.
+        client.write('/ctl', b'PanelSlide\n')
+        client.write(f'/pane/{first}/exec', b'Newcol\n')
+        require(wait_for(lambda: (root / 'transition-6.ppm').exists()), 'transition frame 6 never drawn')
+        scene('18-mid-transition', 'transition-6.ppm')
     lines = ''.join(f'{label} {digest}\n' for label, digest in results)
     if args.update:
         GOLDENS.write_text(lines)