fix: a passing day turns bluer in steps of two days, and the legend says a day keeps its colour

.samples/ci-svg.py

@@ -11,8 +11,9 @@
 of the site cannot be the page itself. The same data (every run of every version in the folder), the same
 rules and the same colours as site/samples.js and samples.css of DotNetSolutionKit:
 
-- a day keeps the result of the branch's last run; a pass fades to ice and a failure rots to dark red over
-  30 days without a run, the colours mixed in OKLab as the site's color-mix does;
+- a day keeps the result of the branch's last run and its colour; a day without a run shows how long ago
+  the run was: a pass a step bluer every 2 days, a failure a little darker every day, ice or dark red from
+  day 30 on, the colours mixed in OKLab as the site's color-mix does;
 - 52 weeks back, the weeks to come fading out, Monday at the top and Sunday at the bottom;
 - light and dark follow the reader's colour scheme.
 
@@ -25,6 +26,7 @@
 import sys
 
 FADE_DAYS = 30
+PASS_STEP_DAYS = 2
 PAST_WEEKS = 52
 FUTURE_WEEKS = 8
 CELL, GAP = 11, 3
@@ -117,10 +119,16 @@ def fill(cell, theme):
         return t["empty"], max(0.15, 1 - cell["future"] / (7 * FUTURE_WEEKS))
     if "ok" not in cell:
         return t["empty"], 1.0
-    fade = min(cell["age"] / FADE_DAYS, 1)
+    fade = fade_of(cell["ok"], cell["age"])
     return (mix(t["sleep"], fade, t["ok"]) if cell["ok"] else mix(t["rot"], fade, t["bad"])), 1.0
 
 
+def fade_of(ok, age):
+    """How far a day has gone from its result, 0 to 1: a pass in steps of PASS_STEP_DAYS, a failure evenly."""
+    days = age // PASS_STEP_DAYS * PASS_STEP_DAYS if ok else age
+    return min(days / FADE_DAYS, 1)
+
+
 # ---- the picture ----------------------------------------------------------------------------------------
 def svg(branch, runs, today):
     grid = cells(runs, today)
@@ -184,12 +192,16 @@ def svg(branch, runs, today):
 
 def legend():
     """What the colours of a day mean: one picture for every branch, under its days in the README."""
-    rows = (("passed", ("ok", "sleep"), f"a pass, fading to ice over {FADE_DAYS} days without a run"),
-            ("failed", ("bad", "rot"), f"a failure, rotting to dark red over {FADE_DAYS} days without a run"))
-    swatches, label_w = 5, 48
+    ages = (0, PASS_STEP_DAYS, FADE_DAYS // 4, FADE_DAYS // 2, FADE_DAYS)
+    rows = (("passed", True, f"the day of a pass, then a step bluer every {PASS_STEP_DAYS} days without a run"),
+            ("failed", False, "the day of a failure, then a little darker every day without a run"))
+    notes = (f"the squares: {', '.join(map(str, ages[:-1]))} and {ages[-1]} days after the run",
+             "a day keeps its colour; a new run makes its day green or red again")
+    swatches, label_w = len(ages), 48
     words_x = LEFT + label_w + swatches * (CELL + GAP) + 8
-    width = words_x + 330
-    height = 34 + 4 * 20 + 4
+    # 11px text averages under 6px a character: the widest line sets the width
+    width = words_x + 6 * max(len(w) for w in [r[2] for r in rows] + list(notes)) + 16
+    height = 34 + (len(rows) + len(notes) + 2) * 20 + 4
 
     css = ["text{font:11px system-ui,-apple-system,'Segoe UI',sans-serif}", ".t{font-size:13px;font-weight:600}"]
 
@@ -207,14 +219,19 @@ def cell(cls, k, y, extra=""):
         body.append(f'<rect class="{cls}" x="{x}" y="{y}" width="{CELL}" height="{CELL}" rx="2"{extra}/>')
 
     y = 34
-    for label, (start, end), words in rows:
+    for label, ok, words in rows:
+        start, end = ("ok", "sleep") if ok else ("bad", "rot")
         body.append(f'<text class="m" x="{LEFT}" y="{y + 9}">{label}</text>')
-        for k in range(swatches):
+        for k, age in enumerate(ages):
             cls = f"L{label}{k}"
-            themed(lambda t, cls=cls, k=k: f".{cls}{{fill:{mix(t[end], k / (swatches - 1), t[start])}}}")
+            fade = fade_of(ok, age)
+            themed(lambda t, cls=cls, fade=fade, start=start, end=end: f".{cls}{{fill:{mix(t[end], fade, t[start])}}}")
             cell(cls, k, y)
         body.append(f'<text class="m" x="{words_x}" y="{y + 9}">{words}</text>')
         y += 20
+    for words in notes:
+        body.append(f'<text class="m" x="{words_x}" y="{y + 9}">{words}</text>')
+        y += 20
     cell("e", 0, y)
     body.append(f'<text class="m" x="{words_x}" y="{y + 9}">no run yet</text>')
     y += 20
@@ -223,8 +240,9 @@ def cell(cls, k, y, extra=""):
     body.append(f'<text class="m" x="{words_x}" y="{y + 9}">the weeks to come</text>')
 
     return (f'<svg xmlns="http://www.w3.org/2000/svg" width="{width}" height="{height}" viewBox="0 0 {width} {height}" '
-            f'role="img" aria-label="How to read the days: a day keeps the result of the last run, a pass fades to ice '
-            f'and a failure rots to dark red over {FADE_DAYS} days without a run">\n'
+            f'role="img" aria-label="How to read the days: a day keeps the result of the last run; without a new run a '
+            f'pass turns a step bluer every {PASS_STEP_DAYS} days and a failure a little darker every day, ice or dark '
+            f'red from day {FADE_DAYS} on; a day keeps its colour">\n'
             f'<style>{chr(10).join(css)}</style>\n' + "\n".join(body) + "\n</svg>\n")
 
 

.samples/generate.sh

@@ -43,17 +43,19 @@ about=$(jq -r --arg b "$branch" '.[] | select(.branch == $b) | .about' "$here/va
 home=$(jq -r '.[] | select(.default) | .branch' "$here/variants.json")
 raw="https://raw.githubusercontent.com/${GITHUB_REPOSITORY:-sawking-tech/DotNetSolutionKit.Samples}"
 fade=$(sed -n 's/^FADE_DAYS = //p' "$here/ci-svg.py")
+step=$(sed -n 's/^PASS_STEP_DAYS = //p' "$here/ci-svg.py")
 
 # What the colours of the days mean: one legend for every branch, drawn by ci-svg.py on the default
 # branch, and the same in words.
 legend() {
     echo "![How to read the days]($raw/$home/.samples/legend.svg)"
     echo
     echo "Each square is a day in UTC, Monday at the top and Sunday at the bottom. A day shows the result of the"
-    echo "last CI run up to it: green for a pass, red for a failure. With no new run the colour changes over $fade"
-    echo "days, a pass fading to ice blue and a failure turning dark red, so an old result is told apart from a"
-    echo "fresh one. A pale square is a day before the first run; the fading squares on the right are the weeks"
-    echo "to come."
+    echo "last CI run up to it: green for a pass, red for a failure. A day without a run shows how long ago the"
+    echo "run was: after a pass it turns a step bluer every $step days, after a failure a little darker every day,"
+    echo "ice blue or dark red from day $fade on. A day keeps its colour; a new run makes its day green or red"
+    echo "again. A pale square is a day before the first run; the fading squares on the right are the weeks to"
+    echo "come."
 }
 {
     echo "# Sample: $branch"