contrib: the shadertoy presets, usable in sl0ppty

They only existed in a browser, which is a strange place for a terminal
multiplexer's shaders to live. Now each one is a file you can paste.

contrib/shaders/ holds all thirty-two, one per file, *generated* from the
presets in shadertoy.html by contrib/gen-shaders. The page stays the source:
it is where they are written, previewed and conformance-tested against the
compiler, and a hand-kept second copy would drift the day after it was
written. `gen-shaders --check` says whether the files are current, which is a
test, so the drift is a failing build rather than a stale example.

contrib/shader-tour cycles a session through them, in the shape theme-tour
already established — write the config the session watches and let the
watcher do the rest. It takes one shader, one group, or nothing for all of
them, and it resolves a short name (`torch`) as well as the whole slug
(`guides-torch`), because nobody remembers which group a shader is in. The
tour writes the theme alongside the shader: shaders resolve default-coloured
text through theme's default_fg/default_bg, so a preset judged without one is
being judged against a guess.

The new test is the one that matters. Every shipped file is loaded into a
real session and has to *change the cells of a pane* -- an example that
previews beautifully and does nothing when pasted is worse than no example,
and neither the toy's conformance test nor a config parse would notice. Three
of them are then checked for the specific thing they claim: scanlines
alternate row by row, indent guides land on every fourth column, a flat dim
is flat. One session, reloaded per preset, which is both quick and a fair
exercise of the path anyone will actually use.

Renamed the "the built-ins, as expressions" group to drop the qualifier from
its filenames; it was generating built-ins-as-expressions-scanlines.kdl,
which is a sentence rather than a name.

1 files changed, 152 insertions, 0 deletions

diff --git a/tests/test_shader_presets.py b/tests/test_shader_presets.py
new file mode 100644
index 0000000..f6a2b14
--- /dev/null
+++ b/tests/test_shader_presets.py
@@ -0,0 +1,152 @@
+#!/usr/bin/env python3
+"""Every shader in contrib/shaders/ works in sl0ppty.
+
+The toy proves the *language* matches (test_shadertoy.py). This proves the
+shipped files: that each one parses as config, is accepted by the shader
+registry, and actually changes the cells of a real pane. An example that
+previews beautifully and does nothing when you paste it is worse than no
+example, and nothing else would catch that.
+
+One session, reloaded per preset, because that is both fast and a fair
+exercise of the reload path -- which is how anyone will actually try these.
+"""
+import glob
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+
+from harness import Session, check, report
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+CONTRIB = os.path.join(HERE, "..", "contrib")
+FILES = sorted(glob.glob(os.path.join(CONTRIB, "shaders", "*.kdl")))
+
+# Prints a screenful of known-coloured text, then waits.
+SH = ["/bin/sh", "-c",
+      'printf "\\033]2;p\\007"; '
+      'i=0; while [ $i -lt 12 ]; do printf "%s\\n" ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789; '
+      'i=$((i+1)); done; read x']
+
+# Every colour in the pane's content area, so "did anything change" is a
+# question about the whole pane rather than one lucky cell.
+def cells(snap, pane):
+    out = []
+    for row in range(pane["content_h"]):
+        y = pane["content_y"] + row
+        for col in range(pane["content_w"]):
+            run = snap.style_at(pane["content_x"] + col, y)
+            out.append((run or {}).get("fg"))
+    return out
+
+
+def test_every_preset_changes_the_pane():
+    check("contrib ships shader presets", len(FILES) >= 20, str(len(FILES)))
+
+    cfg = tempfile.NamedTemporaryFile("w", suffix=".kdl", delete=False)
+    cfg.write('theme { default_fg "#ffffff" default_bg "#000000" }\n')
+    cfg.close()
+
+    with Session(SH, cols=70, rows=18, config=cfg.name) as s:
+        s.until_text("ABCDEF")
+        base = cells(s.snapshot(), s.pane())
+
+        for path in FILES:
+            name = os.path.basename(path)
+            # The theme keeps "what colour is a cell" answerable; the preset is
+            # appended so it is exactly the file a user would paste.
+            with open(cfg.name, "w") as f:
+                f.write('theme { default_fg "#ffffff" default_bg "#000000" }\n')
+                f.write(open(path).read())
+            reply = s.api("reload")
+            check(f"{name} loads", reply.get("ok") is True, str(reply))
+
+            s.settle(20)
+            now = cells(s.snapshot(), s.pane())
+            check(f"{name} changes the pane", now != base,
+                  f"identical to unshaded: {now[:3]}")
+
+    os.unlink(cfg.name)
+
+
+def test_a_few_of_them_do_the_specific_thing_they_claim():
+    """Spot checks with a known answer, so "it changed something" cannot be
+    satisfied by an effect that changed the wrong thing."""
+    cfg = tempfile.NamedTemporaryFile("w", suffix=".kdl", delete=False)
+
+    def load(basename):
+        with open(cfg.name, "w") as f:
+            f.write('theme { default_fg "#ffffff" default_bg "#000000" }\n')
+            f.write(open(os.path.join(CONTRIB, "shaders", basename)).read())
+
+    load("built-ins-scanlines.kdl")
+    with Session(SH, cols=70, rows=18, config=cfg.name) as s:
+        s.until_text("ABCDEF")
+        pane = s.pane()
+        rows = [cells(s.snapshot(), pane)[r * pane["content_w"]]
+                for r in range(4)]
+        check("scanlines alternate row by row",
+              rows[0] == rows[2] and rows[1] == rows[3] and rows[0] != rows[1],
+              str(rows))
+
+    load("guides-indent-guides.kdl")
+    with Session(SH, cols=70, rows=18, config=cfg.name) as s:
+        s.until_text("ABCDEF")
+        pane = s.pane()
+        row = cells(s.snapshot(), pane)[:9]
+        check("indent guides mark every fourth column",
+              row[0] == row[4] == row[8] and row[0] != row[1] and row[1] == row[2],
+              str(row))
+
+    load("pane-states-unfocused.kdl")
+    with Session(SH, cols=70, rows=18, config=cfg.name) as s:
+        s.until_text("ABCDEF")
+        pane = s.pane()
+        flat = cells(s.snapshot(), pane)
+        check("a flat dim is the same everywhere",
+              len({c for c in flat[:40] if c}) == 1, str(flat[:6]))
+
+    os.unlink(cfg.name)
+
+
+def test_the_tour_can_name_every_one_of_them():
+    """contrib/shader-tour resolves a short name (`torch`) as well as the whole
+    slug. A tour that cannot name a shader it ships is a broken demo."""
+    tour = os.path.join(CONTRIB, "shader-tour")
+    conf = tempfile.NamedTemporaryFile("w", suffix=".kdl", delete=False)
+    conf.close()
+    env = dict(os.environ, SL0PPTY_CONFIG=conf.name)
+
+    # Named explicitly rather than derived: a group name with a hyphen in it
+    # (built-ins) makes "the short half" ambiguous to compute and easy to get
+    # accidentally right, which is not a test.
+    for name in ("guides-torch", "torch", "matrix-rain"):
+        out = subprocess.run([tour, name], capture_output=True, text=True, env=env)
+        check(f"the tour applies {name!r}",
+              out.returncode == 0 and "shaders {" in open(conf.name).read(),
+              (out.stdout + out.stderr).strip())
+
+    out = subprocess.run([tour, "definitely-not-a-shader"],
+                         capture_output=True, text=True, env=env)
+    check("and refuses one it does not have", out.returncode != 0,
+          (out.stdout + out.stderr).strip())
+    os.unlink(conf.name)
+
+
+def test_the_files_match_the_page_they_came_from():
+    """They are generated from contrib/shadertoy.html. A hand-edit there and a
+    forgotten regeneration would leave the two disagreeing silently."""
+    if not shutil.which("node"):
+        print("SKIP no node: cannot check the generated files are current")
+        return
+    out = subprocess.run([os.path.join(CONTRIB, "gen-shaders"), "--check"],
+                         capture_output=True, text=True)
+    check("contrib/shaders is current with contrib/shadertoy.html",
+          out.returncode == 0, (out.stderr or out.stdout).strip())
+
+
+for name, fn in sorted(list(globals().items())):
+    if name.startswith("test_"):
+        fn()
+sys.exit(report())