feat(pygal): implement sunburst-basic (#9927)

## Implementation: `sunburst-basic` - python/pygal

Implements the **python/pygal** version of `sunburst-basic`.

**File:** `plots/sunburst-basic/implementations/python/pygal.py`

**Parent Issue:** #821

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/30187416978)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
Co-authored-by: Markus Neusinger <2921697+MarkusNeusinger@users.noreply.github.com>

Author: 3 people

plots/sunburst-basic/implementations/python/pygal.py

@@ -1,11 +1,13 @@
 """ anyplot.ai
 sunburst-basic: Basic Sunburst Chart
-Library: pygal 3.1.0 | Python 3.13.13
-Quality: 73/100 | Created: 2026-05-04
+Library: pygal 3.1.3 | Python 3.13.14
+Quality: 75/100 | Updated: 2026-07-26
 """
 
 import os
+import re
 
+import cairosvg
 import pygal
 from pygal.style import Style
 
@@ -15,7 +17,17 @@
 INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
 INK_MUTED = "#6B6A63" if THEME == "light" else "#A8A79F"
 
-IMPRINT = ("#009E73", "#C475FD", "#4467A3", "#BD8233", "#AE3030", "#2ABCCD", "#954477")
+# All 4 Imprint wedge hues are dark enough that pygal auto-picks BLACK
+# print_labels text (contrast-matched against the wedge fill it normally
+# sits on). But a few team labels land past the disk's outer edge on the
+# plain page background instead of on a wedge; there pygal's per-series
+# fill has no way to know it's off-wedge, so in dark theme black text goes
+# invisible on the near-black canvas. A thin light halo (independent of
+# THEME, since the black fill itself is theme-independent) keeps every
+# label legible everywhere it can land, without touching on-wedge contrast.
+LABEL_HALO = "#F0EFE8"
+
+IMPRINT = ("#009E73", "#C475FD", "#4467A3", "#BD8233")
 
 custom_style = Style(
     background=PAGE_BG,
@@ -24,58 +36,87 @@
     foreground_strong=INK,
     foreground_subtle=INK_MUTED,
     colors=IMPRINT,
-    title_font_size=72,
-    label_font_size=40,
-    major_label_font_size=36,
-    legend_font_size=40,
-    value_font_size=32,
-    stroke_width=2,
+    title_font_size=66,
+    label_font_size=56,
+    major_label_font_size=40,
+    legend_font_size=44,
+    value_font_size=36,
+    value_label_font_size=38,
+    stroke_width=3,
 )
 
-# Organizational budget breakdown (in $K)
-# Each department: (name, primary_color, [(team, team_color, value), ...])
-# Team colors are shades of their parent department color
+# Organizational budget breakdown (in $K). Each department is added as its
+# own pygal series (its teams are that series' datapoints), NOT as two
+# parallel "Departments" + "Teams" series. That distinction is what makes
+# pygal's multi-series "dual" Pie mode produce a genuine sunburst: dual mode
+# sizes each series' coarse inner wedge by that series' OWN value sum, and
+# subdivides its thin outer-ring arc by its own datapoints. With one series
+# per department, the inner disk becomes 4 wedges sized by true department
+# share, and each wedge's outer arc subdivides proportionally by that
+# department's teams. (A "Departments" + "Teams" series pair does not work:
+# both series always sum to the same grand total, so their coarse wedges
+# would always split 50/50 no matter what the real department shares are.)
+#
+# Every department lists exactly the same number of teams (3): pygal pads
+# shorter series with a trailing zero-value point to match the longest
+# series, which would silently steal the "last datapoint" slot the trick
+# below depends on.
+#
+# Within each department, the smallest team is listed last. pygal's dual
+# mode paints the coarse (department-level) wedge using the metadata of the
+# LAST datapoint drawn, so giving that entry `label=<department name>`
+# is what puts the department name on the big inner wedge. Its own outer
+# sliver stays label-free because pygal only prints a datapoint's label when
+# its angular span is at least ~17 degrees (0.3 radians), and each smallest
+# team is kept under that share by construction; its `tooltip` still
+# surfaces the real team name on hover.
 departments = [
     (
         "Technology",
-        "#009E73",
         [
-            ("Backend Engineering", "#009E73", 180),
-            ("Frontend Engineering", "#40B88E", 140),
-            ("Data Science", "#7DD3AB", 100),
+            ("Backend Engineering", "#009E73", 200),
+            ("Frontend Engineering", "#40B88E", 175),
+            ("Data Science", "#7DD3AB", 45),
         ],
     ),
-    ("Business", "#C475FD", [("Sales", "#C475FD", 150), ("Finance", "#D195FE", 100), ("Legal", "#DEB5FE", 60)]),  # imprint lavender family
-    ("Operations", "#4467A3", [("IT Support", "#4467A3", 90), ("Human Resources", "#7A93BD", 80)]),  # imprint blue family
-    ("Marketing", "#BD8233", [("Brand Design", "#BD8233", 60), ("Digital Marketing", "#D1A668", 40)]),  # imprint ochre family
+    ("Business", [("Sales", "#C475FD", 160), ("Finance", "#D195FE", 105), ("Legal", "#DEB5FE", 45)]),
+    ("Operations", [("IT Support", "#4467A3", 85), ("Human Resources", "#7A93BD", 45), ("Facilities", "#A8BFDA", 40)]),
+    (
+        "Marketing",
+        [("Brand Design", "#BD8233", 45), ("Digital Marketing", "#D1A668", 30), ("Content Marketing", "#E3C89C", 25)],
+    ),
 ]
 
-# pygal.Pie with multiple series creates concentric rings — a sunburst chart
-# inner_radius=0.4 creates a donut; first series = inner ring (departments)
 chart = pygal.Pie(
     style=custom_style,
-    width=3600,
-    height=3600,
-    title="sunburst-basic · pygal · anyplot.ai",
-    inner_radius=0.4,
-    show_legend=True,
-    legend_at_bottom=True,
-    legend_at_bottom_columns=4,
+    width=2400,
+    height=2400,
+    title="sunburst-basic · python · pygal · anyplot.ai",
+    show_legend=False,
+    print_labels=True,
     print_values=False,
+    margin=380,
 )
 
-# Inner ring: department totals — each slice color matches the department
-chart.add(
-    "Departments",
-    [{"value": sum(v for _, _, v in teams), "label": name, "color": color} for name, color, teams in departments],
-)
+for dept_name, teams in departments:
+    points = [{"value": value, "color": color, "label": name, "tooltip": name} for name, color, value in teams[:-1]]
+    carrier_name, carrier_color, carrier_value = teams[-1]
+    points.append({"value": carrier_value, "color": carrier_color, "label": dept_name, "tooltip": carrier_name})
+    chart.add(dept_name, points)
 
-# Outer ring: individual teams — shades of their parent department color
-chart.add(
-    "Teams",
-    [{"value": value, "label": name, "color": color} for _, _, teams in departments for name, color, value in teams],
+svg = chart.render(is_unicode=True)
+chart_id = re.search(r'id="(chart-[^"]+)"', svg).group(1)
+# pygal's base stylesheet ships `#chart-id text, #chart-id tspan
+# {stroke:none!important}`, which would otherwise strip the halo above -
+# match its id-scoped specificity (plus !important) to win the cascade.
+svg = svg.replace(
+    '<style type="text/css">',
+    f'<style type="text/css">#{chart_id} .text-overlay text.label '
+    f"{{stroke:{LABEL_HALO} !important;stroke-width:2px !important;"
+    f"stroke-linejoin:round !important;}}",
+    1,
 )
 
-chart.render_to_png(f"plot-{THEME}.png")
-with open(f"plot-{THEME}.html", "wb") as f:
-    f.write(chart.render())
+cairosvg.svg2png(bytestring=svg.encode("utf-8"), write_to=f"plot-{THEME}.png", dpi=72)
+with open(f"plot-{THEME}.html", "w", encoding="utf-8") as f:
+    f.write(svg)