gjrichter/create-ixmap

Create ixMap Skill

Creates complete HTML files with interactive ixMaps visualizations for geographic data.

⚠️ CRITICAL RULES (Never Skip)

1. ixmaps.Map() returns a Promise — capture the instance in .then()

   // ✅ correct
   var mapInstance = null;
   ixmaps.Map("map", { ... })
       .view({ ... })
       .options({ ... })
       .then(function(map) {
           mapInstance = map;
           // use mapInstance.layer(...) here or later
       });
   
   // ❌ WRONG — ixmaps.Map() returns a Promise, not the map instance
   const myMap = ixmaps.Map("map", { ... });
   myMap.layer(...);  // fails silently — myMap is a Promise
   

2. ALWAYS include .binding() with geo and value

3. ALWAYS include showdata: "true" in .style()

4. ALWAYS include .meta() with tooltip (default: { tooltip: "{{theme.item.chart}}{{theme.item.data}}" })

   • Also include name whenever you plan to use changeThemeStyle at runtime (see rule 21)

5. NEVER use .tooltip() — doesn't exist

6. NEVER combine CHART and CHOROPLETH in one type string — mutually exclusive

7. NEVER use |EXACT classification — deprecated; use CATEGORICAL

8. NEVER use map as variable name — conflicts with internals; use myMap 8a. NEVER use reserved HTML element IDs — ixMaps owns loading-div, tooltip, contextmenu. Using them causes visible artifacts (a white box stuck on the map). Use app-loading or any other non-conflicting name for your own overlays.

9. Prefer fillopacity over opacity in .style() — both work, but fillopacity is the recommended form

10. NEVER use fillcolor — use colorscheme: ["#hex"]

11. NEVER add .legend("string") unless user explicitly requests it — destroys the default color legend

12. ALWAYS use CDN https://cdn.jsdelivr.net/gh/gjrichter/ixmaps-flat@master/ixmaps.js

    • data.js (https://cdn.jsdelivr.net/gh/gjrichter/data.js@master/data.js) is already loaded by ixmaps — Data.* functions are available inside query: and process: callbacks without any extra <script> tag
    • Only include the data.js CDN explicitly when you need Data.* functions outside ixmaps theme realization (e.g. pre-processing data in your own <script> block before defining layers)

13. NEVER use info from ixmaps.ca or ixmaps.com — only github.com/gjrichter/ixmaps-flat

14. ONE .data() per layer — never chain two .data() calls on the same layer

15. 🔑 SAME LAYER NAME = GEOMETRY REUSE — see § Geometry Reuse Pre-flight Checklist below for the authoritative rules. Quick example:

    // ✅ Both named "regions" → overlay binds onto regions' geometry
    myMap.layer("regions").data({url:geo}).type("FEATURE").define();
    myMap.layer("regions").data({url:csv}).binding({lookup:"code",value:"pct"})
                          .type("CHOROPLETH|QUANTILE").define();
    
    // ❌ Different names → overlay has nothing to draw on, silently broken
    myMap.layer("stats").type("CHOROPLETH").define();
    

    For runtime theme swapping (sidebar picker, time slider) → see § Multi-Layer Join Pattern · B. Swappable themes for the full setTheme / removeTheme pattern.

16. NO FEATURE on overlay layers — base layer gets FEATURE; choropleth/chart overlays do not:

    • ✅ myMap.layer("x").type("FEATURE") → myMap.layer("x").type("CHOROPLETH|CATEGORICAL")
    • ❌ myMap.layer("x").type("FEATURE") → myMap.layer("x").type("FEATURE|CHOROPLETH|CATEGORICAL")

17. objectscaling: "dynamic" requires normalSizeScale — set to map scale denominator: zoom 4→30M · 5→15M · 6→8M · 8→2M · 10→500k · 12→100k

18. lookup goes in .binding(), not in .data()

19. values: for CATEGORICAL must be strings — ixMaps bug: numeric values silently ignored

20. To make a fill invisible use colorscheme: ["none"] — NOT fillopacity: 0. ⚠️ ixMaps bug: fillopacity: 0 is silently coerced to 1 (fully opaque), so it does the opposite of hiding the fill

21. FEATURE layer styling depends on geometry type:

    • Line features — colorscheme sets the line/stroke color; linecolor is overridden by colorscheme and has no effect. Use colorscheme: ["none"] to make lines invisible. Color classes (multi-value array) apply as line-color classes. Data-driven colorization (CHOROPLETH|QUANTILE, CHOROPLETH|CATEGORICAL, etc.) works symmetrically with polygon features — colorscheme drives stroke color instead of fill.
    • Polygon features — colorscheme sets the fill color (single value or array for color classes); linecolor sets the border/outline color of the polygon. fillopacity controls fill transparency; linewidth controls border thickness.

22. changeThemeStyle requires name in .meta() — it finds themes by name, NOT by the string in myMap.layer("name"). Without name, calls silently have no effect:

    .meta({ name: "punti", tooltip: "..." })   // ✅ — changeThemeStyle("punti", ...) will work
    .meta({ tooltip: "..." })                   // ❌ — theme is invisible to changeThemeStyle
    

23. hideTheme/showTheme also resolve themes by name in .meta() — same rule as changeThemeStyle. Once name is set, use ixmaps.hideTheme(name) / ixmaps.showTheme(name) for layer visibility. CSS injection ([id*=":name:"] { display: none !important }) remains a reliable fallback if hideTheme behaves unexpectedly for a given layer type.

24. NEVER use the same string for a layer name and a meta.name — reusing one string for both has caused failures. They are different identifiers:

    • Layer name (myMap.layer("comuni")) = geometry bucket; shared by a FEATURE base and the overlays that reuse its geometry, and not unique. A standalone CHART layer with its own geo data can use any arbitrary name (even "generic").
    • meta.name = the unique theme id used by changeThemeStyle / hideTheme / showTheme / removeTheme. Keep them distinct — e.g. layer "comuni" + meta.name: "comuni-choropleth".

---

🔴 Silent Failure Hotspots

These produce no error, no warning, no console message — the map just silently renders wrong. Check these first when something looks broken.

| # | What you did | What happens | Fix | |---|---|---|---| | 1 | Omitted showdata: "true" | Layer loads, data processes, nothing renders — completely invisible | Add showdata: "true" to every .style() | | 2 | Used different layer name for overlay vs FEATURE base | Overlay renders nothing; no error | Overlay name must exactly match the FEATURE base name | | 3 | Omitted the ixmaps.Map() assignment (var myMap = …) | Map may partially init; further calls fail or do nothing | Always capture the instance in a variable named myMap (never map). Use var/outer scope if it's reassigned in buildMap() or shared across functions; const is fine for a single self-contained block | | 4 | Omitted name in .meta() | changeThemeStyle / hideTheme / showTheme silently no-op | Add name: "themeName" to every .meta() you'll reference at runtime | | 5 | Called changeThemeStyle via ixmaps.map() or fluent chain | Returns {szMap: null}; no update | Use myMap.then(api => api.changeThemeStyle(...)) | | 6 | Missing .binding() | Layer skipped entirely | .binding() with geo + value is required on every layer | | 7 | Missing .define() | Layer never registered | .define() must close every layer chain | | 8 | objectscaling: "dynamic" without normalSizeScale | All symbols invisible or wildly oversized | Add normalSizeScale: "8000000" (match to zoom level) | | 9 | Overlay layer named differently from FEATURE base | No geometry to draw on → blank | Always check: overlay name == base name | | 10 | FEATURE\|SILENT on base + overlay needs tooltips | Overlay renders but tooltip never fires | Drop \|SILENT from any base that has overlays needing hover | | 11 | values: for CATEGORICAL contains numbers | Categories silently unmatched; no color applied | Cast all values: entries to strings: ["1","2","3"] | | 12 | fillopacity: 0 to hide a fill | Silently coerced to 1 (fully opaque) — fill shows at full strength, the opposite of intended | Use colorscheme: ["none"] (array) to hide a fill; never fillopacity: 0 | | 13 | Redefining an overlay under a new meta.name without removeTheme(prev) | Old theme stays — themes stack | Reuse the same meta.name (auto-replaces) or call api.removeTheme(prev) before .define() | | 14 | Geometry branch mismatch (main=2026 codes vs data=2024) | Some regions silently unjoined (Sardinia etc.) | Pin geometry to commit 0153a0e for 2024-compatible ISTAT codes |

---

Geometry Reuse Pre-flight Checklist

Run this mental check before writing any overlay layer (CHOROPLETH, CHART on polygons):

[ ] Is this overlay's myMap.layer("NAME") identical to the FEATURE base layer name?
    → If NO: rename it. A different name = no geometry = nothing renders.

[ ] Does this overlay need to be swappable at runtime (sidebar picker, time slider)?
    → If YES: add name to .meta(). Reuse the SAME meta.name on each swap → auto-replaces.
              (Or use a different name per theme + api.removeTheme(prev) before each .define().)
    → If NO: no meta.name required (unless changeThemeStyle is needed)

---

Choosing Visualization Type

Is your data...

├─ Points (lat/lon)?
│  ├─ Just locations?                    → CHART|DOT
│  ├─ Colored by category (legend-selectable)? → CHART|BUBBLE|CATEGORICAL  ⚠️ NOT DOT|CATEGORICAL
│  ├─ Sized by value?                    → CHART|BUBBLE|SIZE|VALUES
│  ├─ Density heatmap (circles)?         → CHART|BUBBLE|SIZE|AGGREGATE  + gridwidth:"5px"
│  ├─ Density heatmap (squares)?         → CHART|SYMBOL|GRIDSIZE|AGGREGATE|RECT|SUM|DOPACITY|VALUES  + symbols:["square"] + gridwidth:"80px"
│  ├─ Sparklines per grid cell?          → CHART|SYMBOL|PLOT|LINES  (see Sparklines below)
│  ├─ Flows origin→destination?          → CHART|VECTOR|BEZIER|POINTER
│  ├─ Multi-value per point?             → CHART|SYMBOL|SEQUENCE  (|STAR for 5+ categories)
│  └─ Stacked/grouped bars per location? → CHART|BAR|STACKED  (add |SIZE|GRID|BOX|VALUES for full display)
│     gridx:N in .style() = values per bar group (gridx:2 → 2 segments per bar; gridx:3 → 3 separate bars)
│
└─ Polygons (GeoJSON/TopoJSON)?
   ├─ Boundaries only?                   → FEATURE
   ├─ Colored by data (geometry+data)?   → FEATURE|CHOROPLETH  (|QUANTILE | |EQUIDISTANT | |CATEGORICAL)
   └─ Data joined to pre-loaded geometry?→ CHOROPLETH only — NEVER FEATURE|CHOROPLETH

Key type modifiers:

• |GLOW — glow effect on any CHART type
• |DOPACITYMAX — dynamic opacity (high values prominent); add alpha: "field" to .binding()
• |DOPACITYMINMAX — dynamic opacity (extremes prominent)
• |CATEGORICAL — discrete category coloring; values: array in style maps to colorscheme in order
• |SILENT — excludes layer from legend, statistics and suppresses tooltips on its items
• |NOLEGEND — excludes layer from legend only (tooltips still work)
• |NOOUTLIER — removes extreme outliers from classification calculations
• |ZEROISNOTVALUE — suppresses rendering where value ≤ 0 (useful for sparse/incomplete time series)
• |NOSCALE — disables dynamic zoom scaling; flows/symbols stay constant size regardless of zoom
• |GRADIENT — gradient color along flow lines (origin color → destination color); use with CHART|VECTOR|BEZIER — gradient must be defined via linecolor: ["#from","#to"] array, NOT colorscheme
• |CLIPTOGEOBOUNDS — clips chart rendering to the containing polygon boundary
• |DOMINANT|PERCENTOFMEAN — colors by which of multiple piped fields is above-mean dominant; useful for showing "winner" category per region
• |DTEXT — makes VALUES-generated text labels on CHOROPLETH themes properly sized (always pair with |VALUES on choropleth layers that show value labels)
• |SMOOTH — smoothing interpolation on sparkline curves
• |SORT / |SORT|DOWN — sort sparkline categories ascending / descending
• |TEXTLEGEND — renders category labels directly on chart symbols instead of in the legend box
• |TEXTONLY — text labels only, no chart symbol (combine with CHART|LABEL|VALUES|FIXSIZE|NOLEGEND)

Aggregation modifiers (replace the value of each cell with the aggregate):

| Modifier | Computes | |---|---| | SUM | Sum of all values in cell | | COUNT | Count of rows in cell | | MEAN | Arithmetic mean | | MIN | Minimum value | | MAX | Maximum value |

Classification methods (used with CHOROPLETH and CHART):

| Method | Description | |---|---| | EQUIDISTANT | Equal-width intervals across the data range | | QUANTILE | Equal-count intervals — each class has the same number of features | | HEADTAIL | Head/tail breaks — iteratively splits at the mean; best for heavy-tailed distributions | | NATURAL | Jenks natural breaks — minimises within-class variance | | LOG | Logarithmic intervals — useful when values span several orders of magnitude |

VECTOR sub-modifiers:

• |DASH — animated flowing dashes along flow direction (combine freely with BEZIER|POINTER|FADEIN)
• |GRADIENT — gradient color from origin to destination along each flow line

Deprecated modifiers — do NOT use:

• ~~SIZEP1~~ → use SIZE + sizepow: 1 in .style() instead
• ~~EXACT~~ → use CATEGORICAL instead

For full type-string reference and all modifiers → API_REFERENCE.md § Visualization Types

---

Workflow

1. Parse the user's request: data source, visualization goal, styling preferences

2. Ask if key info is missing (data format? geographic scope?)

3. Choose template:

   • template-points.html — CSV/JSON with lat/lon
   • template-geojson.html — GeoJSON/TopoJSON
   • template-multi-layer.html — multiple layers with join
   • template.html — general purpose

4. Write the HTML file

5. Validate before writing:

   • [ ] myMap = ixmaps.Map(...) — instance captured in a variable (var if reassigned/shared, const for a single block; never name it map)
   • [ ] .binding() has geo + value
   • [ ] .style() has showdata: "true"
   • [ ] .meta() present with tooltip
   • [ ] If objectscaling:"dynamic" → normalSizeScale set
   • [ ] Start with scale: 1 — let user request size adjustments

   Optional programmatic check — for parameter-driven maps, validate a JSON config against skill-ui.yaml before generating:

   node validate-config.js config.json    # checks types, ranges, valid options, deps
   # one-time setup if missing: npm install js-yaml
   

6. Confirm file created; explain what it shows; offer to enhance

Hosting local data — if the user's data is a local file but a layer needs a data({url:…}) (CORS blocks file://), upload it to get a CDN URL:

./upload-helper.sh data.csv [project-name]   # GitHub API → git → manual fallback

Needs IXMAPS_GITHUB_TOKEN + IXMAPS_REPO_USER env vars for automated upload; otherwise it prints manual steps. Full setup → DATA_HOSTING_GUIDE.md. (Or skip hosting entirely and inline the data via obj: — see § Data Configuration.)

---

Defaults

| Setting | Default | |---------|---------| | filename | ixmap.html | | mapType | "VT_TONER_LITE" ← always use unless user asks otherwise | | center | { lat: 42.5, lng: 12.5 } (Italy) | | zoom | 6 | | colorscheme | ["#0066cc"] | | basemapopacity | 0.6 | | flushChartDraw | 1000000 | | flushPaintShape | (not set) — set to 1000000 when rendering large polygon datasets (municipalities, communes) to avoid rendering hangs | | zoomAnimation | true — smooth zoom transitions; set false to disable | | tools | true |

Valid basemaps (case-sensitive): "VT_TONER_LITE" · "white" · "CartoDB - Dark matter" · "CartoDB - Positron" · "Stamen Terrain" · "OpenStreetMap - Osmarenderer" ❌ NOT: "OpenStreetMap" · "OSM" · "CartoDB Positron" → See MAP_TYPES_GUIDE.md for full list

---

Map Init Pattern

⚠️ Scrollbar pitfall — never use width: 100vw; height: 100vh on the map <div>. When a scrollbar appears, vw/vh exceed the viewport and trigger a feedback loop. Always use:

html, body { width: 100%; height: 100%; overflow: hidden; }
#map { width: 100%; height: 100%; }

const myMap = ixmaps.Map("map", {
    mapType: "VT_TONER_LITE",
    mode:    "info",
    legend:  "closed",   // or "open"
    tools:   true
})
.view({ center: { lat: 42.5, lng: 12.5 }, zoom: 6 })
.options({
    objectscaling:   "dynamic",
    normalSizeScale: "8000000",   // match to zoom (zoom6≈8M, zoom12≈100k)
    basemapopacity:  0.6,
    flushChartDraw:  1000000
});

Projections

All projections use SVG-based rendering. Omit mapProjection for the default Web Mercator / Leaflet tile setup.

| mapProjection value | Also accepted | Projection | |---|---|---| | (omit) | — | Default Web Mercator (Leaflet tiles) | | "mercator" | — | Mercator (SVG, no tile layer) | | "winkel" | — | Winkel Tripel | | "equalearth" | — | Equal Earth | | "albersequalarea" | "albers" | Albers Equal-Area Conic | | "lambertazimuthalequalarea" | "lambert" | Lambert Azimuthal Equal-Area (EPSG:3035) | | "orthographic" | — | Orthographic (globe view) |

• Lookup is case-insensitive; unknown values fall back to Mercator
• For any projected map: use array .view([lat, lng], zoom) — object {center,zoom} does NOT work with projections
• Set mapType to the background/sea color instead of using CSS: mapType: "#0a1929" (dark), mapType: "black", mapType: "dark", mapType: "white", or any hex color. Do not use mapType: "white" + CSS background on #map — set it directly in mapType.
• Add a graticule layer before data layers for smooth curves (see Graticule below)
• Albers only: pass projectionParams in map options to set custom standard parallels / center for conic tuning

Lambert projection (Eurostat style — Europe)

var myMap = ixmaps.Map("map", {
  mapType:       "white",
  mapProjection: "lambert",      // Lambert Azimuthal Equal-Area — EPSG:3035
  mode:          "pan",
  legend:        "closed",
  tools:         false
})
.view([53.4, 16.9], 3.7)
.options({ basemapopacity: 0, flushChartDraw: 1000000 });

Equal Earth projection (world maps)

var myMap = ixmaps.Map("map", {
  mapType:       "#0a1929",      // dark ocean — set background directly in mapType, not CSS
  mapProjection: "equalearth",
  mode:          "info",
  legend:        "closed",
  tools:         false
})
.view([0, 0], 1)                // zoom: 0–1 for world-scale projections
.options({ basemapopacity: 0, flushChartDraw: 1000000 });

Graticule (world grid lines)

(function() {
  var step = 10, features = [];
  for (var lon = -180; lon <= 180; lon += step) {
    var coords = [];
    for (var lat = -90; lat <= 90; lat += 2) coords.push([lon, lat]);
    features.push({ type:"Feature", geometry:{ type:"LineString", coordinates:coords }, properties:{} });
  }
  for (var lat = -80; lat <= 80; lat += step) {
    var coords = [];
    for (var lon = -180; lon <= 180; lon += 2) coords.push([lon, lat]);
    features.push({ type:"Feature", geometry:{ type:"LineString", coordinates:coords }, properties:{} });
  }
  myMap.layer("graticule")
    .data({ obj: { type:"FeatureCollection", features:features }, type: "geojson" })
    .binding({ geo: "geometry" })
    .type("FEATURE|SILENT")
    .style({ colorscheme: ["#7aaabb"], linewidth: 0.6 })
    .define();
})();

Note: FEATURE|SILENT layers do not need value in .binding() or showdata in .style() — omit both to avoid 'type not found' load errors.

Intermediate points every 2° ensure smooth curves in Lambert projection. Define graticule before the countries layer so it renders underneath.

---

Layer chain (order matters):

myMap.layer("name")
    .data({ url: "…", type: "csv" })   // OR obj: myArray
    .binding({ geo: "lat|lon", value: "fieldname", title: "label" })
    .filter('WHERE field == "value"')   // optional; use AND/OR not && /||
    .type("CHART|BUBBLE|SIZE|VALUES")
    .style({ colorscheme: ["#0066cc"], fillopacity: 0.7, showdata: "true" })
    .meta({ tooltip: "{{label}}: {{fieldname}}" })
    .title("Legend label")
    .define();

Full .options() / .style() property reference → API_REFERENCE.md § Map Constructor and § Style Properties

---

Tooltip Mustache Reference

Tooltips in .meta({ tooltip: "..." }) use {{…}} placeholders. Two prefixes control formatting:

| Syntax | Behaviour | |--------|-----------| | {{fieldname}} | ixmaps-formatted value — may apply number formatting, units, rounding | | {{raw.fieldname}} | Raw unformatted value — bypasses all ixmaps formatting; use this when you want pre-formatted strings (e.g. "1.234.567" from .toLocaleString()) or exact string values | | {{theme.item.chart}} | Renders the built-in chart SVG/HTML for this item | | {{theme.item.data}} | Renders the built-in data table for this item |

raw. is the escape hatch — whenever ixmaps mangles a value (reformats numbers, truncates strings, adds units), use {{raw.field}} to get the original data value unchanged.

⚠️ raw. bypasses auto-formatting — use it only when you do NOT want ixmaps to format the value (e.g. a year 2025 that should not become 2.025). For everything else use {{field}}.

⚠️ datafields is only for restricting {{theme.item.data}} — it filters which fields appear in the built-in data table. All data fields are automatically available as {{field}} in custom tooltip templates; no need to list them in datafields.

| Goal | Syntax | Example output | |---|---|---| | Auto-formatted number | {{freq}} | "8.519" | | String field | {{provincia}} | "PD" | | Raw unformatted number (special cases only) | {{raw.anno}} | 2025 | | Built-in value+label display | {{theme.item.data}} | ixmaps default table |

Pattern for CHOROPLETH tooltips:

.binding({ lookup: "istat", value: "media", title: "comune" })
.style({ showdata: "true" })   // no datafields needed for custom tooltip fields
.meta({ tooltip: "<b>{{comune}}</b> ({{provincia}} — {{regione}})<br>N: {{freq}}<br>Tot: {{ammk}} k€<br>{{theme.item.data}}" })
// string/number fields via {{field}}; use {{theme.item.data}} for the bound value display

---

Geometry Sources

geo: "geometry" for GeoJSON point data — works correctly with all CHART types. ixmaps extracts full-precision coordinates directly from Point.coordinates[lon,lat]. The .type() call (CHART|DOT, CHART|BUBBLE, etc.) controls the renderer — NOT the geo binding. Use geo: "geometry" when source GeoJSON has Point geometry (preferred over property lat/lon fields which may be truncated). Only use geo: "lat|lon" when the data has separate lat/lon columns (CSV, non-geometry JSON).

World countries (GISCO — preferred over world-atlas)

.data({ url: "https://gisco-services.ec.europa.eu/distribution/v2/countries/topojson/CNTR_RG_60M_2020_4326.json", type: "topojson" })
.binding({ geo: "geometry", id: "CNTR_ID", title: "NAME_ENGL" })
// ⚠️ Join field is CNTR_ID (ISO-2) — NOT CNTR_CODE

Scales: 60M (default/world) · 20M · 10M · 3M · 1M (country zoom)

Germany municipalities (LAU 2021)

.data({ url: "https://cdn.jsdelivr.net/gh/gjrichter/geo@028b3fe/lau/germany_lau_2021_4326.topojson", type: "topojson" })
.binding({ geo: "geometry", id: "LAU_ID", title: "LAU_NAME" })
// LAU_ID = 8-digit AGS · LAU_NAME = name · POP_DENS_2021 = density (useful for alpha/DOPACITYMAX)

NUTS1 Germany

.data({ url: "https://gisco-services.ec.europa.eu/distribution/v2/nuts/topojson/NUTS_RG_60M_2021_4326_LEVL_1.json", type: "topojson" })
.filter('WHERE CNTR_CODE == "DE"')
.binding({ geo: "geometry", id: "NUTS_ID", title: "NUTS_NAME" })
// NUTS_ID examples: "DE1", "DEA"  (CNTR_CODE works for NUTS, unlike country data which uses CNTR_ID)

Italy geometry sources (gjrichter/geo)

Municipalities (comuni) — ISTAT, ~8 000 polygons, 500m simplified:

.data({ url: "https://raw.githubusercontent.com/gjrichter/geo/main/italy/boundaries/italy_istat_municipalities_4326_500m.topojson", type: "topojson" })
.binding({ geo: "geometry", id: "com_istat_code_num", title: "name" })
// com_istat_code     = zero-padded STRING "028001"  ← do NOT use for joins unless your data also has zero-padded strings
// com_istat_code_num = plain INTEGER    28001       ← use this for joins with ISTAT CSV data
// Useful properties: com_istat_code_num, com_istat_code, name, prov_istat_code_num, reg_istat_code_num

⚠️ Geometry version pitfall — the main branch of gjrichter/geo was updated to 2026 ISTAT codes on 2026-03-24. Official data sources (MEF IRPEF, ISTAT CSVs) still use 2024 codes. Using main will silently break the join for all Sardinian municipalities and any others renumbered in 2026. Pin to commit 0153a0e14da5dae877b8c94d6deb11f210d4660a for 2024-compatible codes:

https://raw.githubusercontent.com/gjrichter/geo/0153a0e14da5dae877b8c94d6deb11f210d4660a/italy/boundaries/italy_istat_municipalities_4326_500m.topojson

⚠️ ISTAT code join pitfall — the geometry exposes two variants of the municipality code:

• com_istat_code is a zero-padded string ("028001") — it will not match integers or un-padded strings from CSV data
• com_istat_code_num is a plain integer (28001) — use this when your lookup data comes from ISTAT CSVs where codes are stored as numbers

Always verify which variant matches your data before writing the join. Mismatching types silently renders only a fraction of features (those whose string representation happens to match).

⚠️ Use flushPaintShape: 1000000 in .options() when rendering all 8 000 polygons to avoid hangs.

⚠️ Local file:// URLs are blocked by browser CORS — always use CDN or inline obj: Full geometry sources list → API_REFERENCE.md § Data Configuration

---

Multi-Layer Join Pattern

When joining external data to geometry (e.g. TopoJSON + CSV statistics), the overlay layer must reuse the FEATURE base's name so it joins onto its geometry (see critical rule 15).

A. Static overlay (base + one data-driven layer)

// Step 1 — FEATURE base (geometry + id field for join)
myMap.layer("regions")
    .data({ url: "regions.topojson", type: "topojson" })
    .binding({ geo: "geometry", id: "reg_code", title: "reg_name" })
    .type("FEATURE")
    .style({ colorscheme: ["#ccc"], fillopacity: 0.1, linecolor: "#666", linewidth: 0.5, showdata: "true" })
    .define();

// Step 2 — CHOROPLETH overlay (SAME layer name "regions", NO FEATURE flag, lookup joins to id)
myMap.layer("regions")
    .data({ url: "data.csv", type: "csv" })
    .binding({ lookup: "csv_code_col", value: "metric" })
    .type("CHOROPLETH|QUANTILE")
    .style({ colorscheme: ["#eee", "#00468b"], fillopacity: 0.75, showdata: "true" })
    .meta({ tooltip: "{{reg_name}}: {{metric}}" })
    .define();

Critical: id values in geometry must match lookup values in CSV exactly (case-sensitive). Always inspect both sources to confirm field names before writing the join.

B. Swappable themes on the same base (remove-then-define)

For apps where the user flips between multiple visualizations of the same geometry (choropleth / dominant / sparkline / arrows / etc.), use one FEATURE base plus a single swappable overlay always redefined under the same layer name as the base. Do not create a separate layer per theme.

Two identifiers — don't confuse them:

• Layer name (myMap.layer("comuni")) = GEOMETRY bucket — must equal the FEATURE base's name (not unique).
• meta.name (.meta({name: "pie-theme-rd"})) = THEME identity — unique, and the key that drives replacement.
• ⚠️ Never make these two the same string (see Rule 24) — reusing one string for both has caused failures. Keep the meta.name distinct from the layer name.

Replacement is automatic by meta.name. Adding a theme whose meta.name already exists on the map replaces the existing one in place. So there are two ways to swap:

• Same meta.name on every swap → automatic replace (simplest; no removeTheme needed).
• Different meta.name per theme (e.g. one per year/category) → each .define() ADDS a new theme, so you must track the previous name and call api.removeTheme(prev) before defining the next, or they stack. The example below uses this form.

The "direct" flag (aliases "fast", "silent"), passed as the 2nd argument to .layer(...), makes the add/replace fluent — it suppresses the loading spinner and status messages and skips the intermediate render flash during a replace. It does not decide whether a replace happens (that's meta.name); it only makes the transition smooth. The same flag also works as a mode on changeThemeStyle.

// ONE FEATURE base — defined once, no meta.name so it's never removed
myMap.layer("comuni")
    .data({ url: GEO_URL, type: "topojson" })
    .binding({ geo: "geometry", id: "com_istat_code_num", title: "name" })
    .filter("WHERE reg_istat_code_num == 1")
    .type("FEATURE|SILENT")
    .style({ colorscheme: ["#d9e4dc"], fillopacity: 0.55, linecolor: "#8a9d8c", linewidth: 0.2, showdata: "true" })
    .define();

// Remove-then-define swapper.
// removeTheme lives on the embedded Api (not the MapBuilder shim), so the call
// goes through myMap.then(api => ...). Defining the new layer INSIDE the same
// callback guarantees remove-before-add ordering.
let ACTIVE_THEME_NAME = null;

function setTheme({ id, value, value100, type, style, tooltip }) {
  const themeName = "theme-" + id;
  const prev      = ACTIVE_THEME_NAME;
  const bind = { lookup: "ISTAT", title: "COMUNE", value };
  if (value100) bind.value100 = value100;

  myMap.then(api => {
    if (prev) { try { api.removeTheme(prev); } catch(e){} }

    const meta = { name: themeName };
    if (tooltip) meta.tooltip = tooltip;

    myMap.layer("comuni")                                 // ← same name as FEATURE base
      .data({ obj: DATA, type: "json", cache: "true" })
      .binding(bind)
      .type(type)
      .style(Object.assign({ showdata: "true" }, style))
      .meta(meta)                                         // ← meta.name = theme handle
      .define();

    ACTIVE_THEME_NAME = themeName;
  });
}

// Each sidebar click = one setTheme({id, ...}) call — overlays REPLACE, not stack.
setTheme({ id: "rd",        value: "% di RD [RD/RT]",
           type: "CHOROPLETH|QUANTILE|VALUES",
           style:{ colorscheme:["5","#FF4800","#7CB832","auto","#F7FA7A"], title:"% RD" }});
setTheme({ id: "sparkline", value: "% RD 2011|% RD 2012|% RD 2013|% RD 2014",
           type: "CHART|SYMBOL|PLOT|LINES|AREA|AGGREGATE|RECT|GRIDSIZE|MEAN",
           style:{ gridwidthpx:"150", xaxis:["2011","2012","2013","2014"] }});

Common mistakes — DO NOT DO THIS:

// ❌ Different layer names → overlay has no geometry to bind to
myMap.layer("comuni").type("FEATURE").define();
myMap.layer("theme").type("CHOROPLETH")...   // blank / error

// ❌ No meta.name + no removeTheme → every click STACKS a new theme on the map
function setTheme(opts) {
  myMap.layer("comuni").type(opts.type)....define();   // stacks forever
}

// ⚠️ "direct"/"fast"/"silent" is a FLUENCY flag, NOT the replace mechanism.
// Replacement is keyed on meta.name; the flag only suppresses spinner/messages
// and the intermediate render flash. With NO meta.name it still stacks.
myMap.layer("comuni", "direct")...   // smooth, but only replaces if meta.name matches

For replacement, give each swap a stable meta.name (automatic replace) — or use different names plus an explicit removeTheme(prev). Either way the layer name stays "comuni" so the overlay reuses the base geometry.

---

Sparklines (CHART|SYMBOL|PLOT|LINES)

Two distinct patterns depending on data shape:

Pattern A — single column, year as category (raw events)

.binding({ geo: "lat|lon", value: "year" })   // year field = categorical x-axis
.type("CHART|SYMBOL|PLOT|LINES|AREA|FADE|LASTARROW|NOCLIP|GRIDSIZE|CATEGORICAL|AGGREGATE|RECT|SUM|FIXSIZE")
.style({
  gridwidth: "100px", normalsizevalue: "30", markersize: 2,
  colorscheme: ["#00e5ff"], fillopacity: 0.5,
  values: ["2020","2021","2022","2023"],  // ordered x-axis categories (also controls sort)
  showdata: "true"
})
// CATEGORICAL+AGGREGATE+RECT+SUM = aggregation semantics (NOT style)
// AREA|FADE|LASTARROW|FIXSIZE = visual style only
// FIXSIZE: all sparks same size; normalsizevalue controls chart scale (larger = smaller sparks)
// markersize: controls LASTARROW arrow head size (default ~8; use 1–3 for smaller arrows)
// ⚠️ normalsizevalue does NOT control arrow size — use markersize for that
// LASTARROW = arrow marker on last point  |  LASTPOP = dot/pop marker on last point (use one or the other)
// MAX/MIN/MEAN/COUNT/SUM = aggregation modifiers — compute cell aggregate value; NOT sparkline visual markers

BOX|GRID and XAXIS — only add on explicit user request:

• Default (no BOX|GRID): sparkline appears as a lightweight curve/arrow on the map; xaxis/chart still visible in tooltip via {{theme.item.chart}}
• BOX|GRID|XAXIS + label:[]+xaxis:[] in style: renders grid boxes + x-axis labels ON the map — heavier, less performant; use only when user wants to see the grid/axes directly on the map
• BOX alone (without GRID): adds a background box; can be combined with TITLE or BOTTOMTITLE for chart titles; scale-dependent via boxupper/boxlower and titleupper/titlelower style params

// Only when user explicitly wants grid + axis labels on map:
.type("...NOCLIP|BOX|GRID|GRIDSIZE|XAXIS|CATEGORICAL|AGGREGATE|RECT|SUM|FIXSIZE")
.style({
  values: ["2020","2021","2022","2023"],
  label:  ["2020","2021","2022","2023"],
  xaxis:  ["2020","2021","2022","2023"],
})

Pattern B — multiple pre-aggregated columns

.binding({ geo: "lat|lon", value: "val2020|val2021|val2022|val2023" })  // chain columns
.type("CHART|SYMBOL|PLOT|LINES|AREA|FADE|LASTARROW|NOCLIP|GRIDSIZE|FIXSIZE")
// No CATEGORICAL or SUM — data already aggregated

Full sparkline reference, FIXSIZE/normalsizevalue details, point-anchored variant → API_REFERENCE.md § CHART|SYMBOL|PLOT|LINES

---

Animated / Timeseries Maps

⚠️ mapInstance must be captured inside .then(function(map) { mapInstance = map; }) — it is NOT the return value of ixmaps.Map(), which is a Promise.

Remove-then-define (needed only when meta.name varies)

// This example gives each year a DIFFERENT meta.name ("year-2023", "year-2024"),
// so each showYear() would ADD a new theme — removeTheme(prev) tears down the
// previous one first. Simpler alternative: use ONE stable meta.name for all years;
// then each define auto-replaces and no removeTheme is needed.
let ACTIVE = null;   // meta.name of the currently-drawn theme

function showYear(year) {
    const themeName = "year-" + year;
    const prev = ACTIVE;
    myMap.then(api => {
        if (prev) { try { api.removeTheme(prev); } catch(e){} }
        myMap.layer("countries")                                   // SAME name as FEATURE base
            .data({ obj: yearData[year], type: "json" })
            .binding({ geo: "lat|lon", value: "metric" })
            .type("CHART|BUBBLE|SIZE|VALUES")
            .style({ colorscheme: ["#0066cc"], fillopacity: 0.7, showdata: "true" })
            .meta({ name: themeName, tooltip: "{{label}}: {{metric}}" })
            .define();
        ACTIVE = themeName;
    });
}
showYear("2023");

Key: replacement is automatic when the new theme's meta.name matches one already on the map; removeTheme is only needed when the names differ (as above). removeTheme lives on the embedded Api — reach it via myMap.then(api => api.removeTheme(name)). The "direct"/"fast"/"silent" flag (2nd arg to .layer(...)) just makes the swap fluent (no spinner / no intermediate render flash); it is not itself the upsert. Theme name in .meta() is the replace key; layer name ("countries") is the geometry bucket.

Time slider (timefield in .binding()), setThemeTimeFrame() → API_REFERENCE.md § Time Slider

---

Key Style Properties (quick ref)

| Property | Notes | |----------|-------| | colorscheme | Array of hex colors. ["100","tableau"] for auto-palette. A bare string (colorscheme: "#0066cc") is accepted only for a single color — always use the array form (["#0066cc"], ["none"]) as best practice | | fillopacity | 0–1. NEVER use opacity | | linecolor / linewidth | NEVER strokecolor / strokewidth; linecolor accepts a single string or an array ["#c1","#c2"] — array form required for VECTOR\|GRADIENT | | scale | Uniform size multiplier (start at 1) | | normalsizevalue | Data value that maps to "normal" display size. Higher = SMALLER bubbles — a larger reference value means most real data values fall below it, so bubbles render smaller. E.g. "1000" → smaller bubbles than "300". | | gridwidth | Grid cell size for aggregate layers (e.g. "5px") | | rangecentervalue | Diverging center; requires EVEN number of colors | | ranges | Explicit class breaks (n+1 values for n colors) | | values | Category list for CATEGORICAL (must be strings) | | align | Chart anchor: "left" "right" "top" "bottom" "above" "below" | | sizepow | Power for size scaling: radius ∝ value^(1/sizepow). 1 = linear (width ∝ value); 2 = area proportional to value (cartographic standard, flattens apparent contrast); 3 = volume proportional to value (even flatter). Higher = smaller arrows for small values appear relatively larger | | rotation | Rotate chart symbol in degrees (e.g. 35 for a tilted arrow) | | rangescale | Scale factor applied after range computation | | aggregationfield | Field used as aggregation key when AGGREGATE is set | | titlefield | Field used as chart title label (overrides binding title) | | datafields | Array of extra fields carried through to tooltip: ["field1","field2"] — access as {{raw.field1}} | | textscale | Scale factor for label text rendered on the chart | | boxupper / boxlower | Scale-dependent box visibility threshold, e.g. "1:250000" — box shown only when map scale ≤ 1:250k | | valuesupper / valueslower | Scale-dependent value label visibility threshold | | valuedecimals | Decimal places for rendered value labels | | minvaluesize | Minimum pixel size below which no chart symbol is drawn | | units | String appended to rendered value labels, e.g. "%", "€", "km" | | sizefield | Data column that drives symbol SIZE independently from the value (color) field — use with CATEGORICAL to combine category color + numeric size on one layer | | dopacitypow | Power curve exponent for DOPACITY opacity mapping (default ≈ 1; 2 = quadratic, exaggerates contrast) | | dopacityscale | Multiplier applied after opacity calculation — stretches the opacity range | | gridwidthpx | Grid cell width in pixels; supports "factor" mode in changeThemeStyle for runtime zoom-scaling |

Trees (street-level) sizing baseline with |GLOW:

• Use this as a reliable starting point for urban tree inventories (diameter in cm):
  • objectscaling: "dynamic"
  • normalSizeScale: "5000" (street-detail zoom reference)
  • normalsizevalue: "220" (higher value keeps bubbles controlled)
  • scale: 0.32 (reduce apparent size added by |GLOW)
• Rule of thumb: with |GLOW, start with a smaller scale than non-glow bubbles.

Complete style properties, dynamic opacity, diverging scales, categorical color binding → API_REFERENCE.md § Style Properties

---

Runtime Controls (Filters & Layer Toggles)

Interactive controls that modify the map after load. What's available:

• Filter across layers — changeThemeStyle(themeName, "filter:WHERE …", "set") via myMap.then(map => …); aggregate layers (grids, sparklines) re-aggregate. Every responsive layer needs name in .meta().
• Region selector + zoom — a <select> that filters all named themes and pans/zooms via myMap.view(); <option value=""> is the "show all" sentinel.
• Toggle visibility — ixmaps.hideTheme(name) / ixmaps.showTheme(name); start a layer hidden with visible: false in .style() (never call hideTheme from myMap.then()).
• Isolate categories — ixmaps.markThemeClass(name, idx) / unmarkThemeClass(name, idx) for clickable legends (idx = position in the values: array).
• React to zoom/pan/click — myMap.on("zoomend moveend click mouseover …", handler). ixmaps.getZoom() / getCenter() are global (no .then()); getBounds() returns a flat [swLat, swLng, neLat, neLng] array.
• Persist view in URL — read lat/lng/zoom params on init, write back with history.replaceState (debounced); wrap (don't overwrite) an existing htmlgui_onZoomAndPan.

⚠️ ixmaps.map().changeThemeStyle() returns {szMap:null} and silently no-ops — always go through myMap.then(map => …). Full patterns + copy-paste code (filter helper, region selector + overlay CSS, hide/show, mark/unmark, .on() event tables, URL-sync wrapper) → RUNTIME_CONTROLS.md

---

Special Patterns (quick ref)

Categorical color binding (pin specific colors to values):

.type("CHART|BUBBLE|CATEGORICAL")
.style({ colorscheme: ["#4fc3f7","#ffb300","#ef5350"], values: ["C","F","R"], showdata: "true" })

⚠️ Always use values with CATEGORICAL — without it, ixMaps assigns colors by order of first occurrence in the dataset, not by category name. This means color assignments change depending on data order and are unpredictable. values is the only reliable way to pin a specific color to a specific category.

CATEGORICAL + bubble size from a numeric field (color by category AND size by value — single layer):

.binding({ geo: "lat|lon", value: "categoryField", title: "label", size: "numericField" })
.type("CHART|BUBBLE|CATEGORICAL|GLOW")
.style({ colorscheme: ["#4fc3f7","#ffb300","#ef5350"], values: ["C","F","R"], normalsizevalue: "80", showdata: "true" })

Add size: "numericField" to .binding() to drive bubble radius from a numeric column independently from the category value field. This avoids needing a separate SIZE|VALUES layer when you want both category color and numeric sizing.

Urban trees preset (species color + diameter size + GLOW):

.binding({ geo: "lat|lon", value: "SPECIE", size: "DIAMETRO", title: "LUOGO" })
.type("CHART|BUBBLE|CATEGORICAL|GLOW")
.style({
  colorscheme: [...],
  values: [...],               // species list, fixed order
  normalsizevalue: "220",
  scale: 0.32,
  fillopacity: 0.8,
  showdata: "true"
})
// map options: objectscaling:"dynamic", normalSizeScale:"5000"

Dynamic opacity from a field:

.type("CHART|BUBBLE|SIZE|DOPACITYMAX")
.binding({ geo: "lat|lon", value: "count", alpha: "density" })

Glow effect: add |GLOW to any CHART type

Flows with animated dashes: CHART|VECTOR|BEZIER|POINTER|DASH

CHART|USER — custom draw functions (pinnacleChart, arrowChart):

Scripts required — load after ixmaps.js, order between them does not matter:

| Draw function | Scripts needed | |---|---| | arrowChart | d3.v3.min.js + arrow_chart.js | | pinnacleChart | d3.v3.min.js + chart.js + arrow_chart.js |

<!-- arrowChart only -->
<script src="https://d3js.org/d3.v3.min.js"></script>
<script src="https://cdn.jsdelivr.net/gh/gjrichter/ixmaps-flat@master/usercharts/d3/arrow_chart.js"></script>

<!-- pinnacleChart (also needs chart.js) -->
<script src="https://cdn.jsdelivr.net/gh/gjrichter/ixmaps-flat@master/usercharts/d3/chart.js"></script>

The userdraw style property names the draw function ("pinnacleChart" or "arrowChart"). Key type modifiers used with USER charts:

| Modifier | Role | |---|---| | DIFFERENCE | computes value[1] − value[0] from a "a\|b" binding | | NONEGATIVE | render flag — suppresses drawing the chart symbol where the computed value ≤ 0 (data row is still processed; only rendering is skipped) | | RELOCATE | relocates the chart symbol to the geometry centroid | | BOX | adds a background box behind the label | | BOTTOMTITLE | places title below the chart symbol | | NOLEGEND | excludes this layer from the map legend |

Split-winner pattern — two layers from one dataset, no pre-filtering needed:

// Layer A — shows only communes where Sì wins (voti_si − voti_no > 0)
myMap.layer("comuni")
    .data({ url: DATA_URL, type: "csv" })
    .binding({ lookup: "cod_istat", value: "voti_no|voti_si", title: "desc_com" })
    .type("CHART|USER|3D|DIFFERENCE|AGGREGATE|RECT|RELOCATE|SUM|VALUES|NONEGATIVE|BOX|BOTTOMTITLE|NOLEGEND")
    .style({
        name:             "chart_si",
        userdraw:         "pinnacleChart",
        colorscheme:      SI_COLORS,
        sizepow:          2,
        normalsizevalue:  1000000,
        aggregationfield: "desc_com",
        titlefield:       "desc_com",
        datafields:       ["desc_com","desc_prov","margin_f"],
        showdata:         "true"
    })
    .meta({ name: "chart_si", tooltip: "{{desc_com}}<br>voti in più Sì: {{raw.margin_f}}" })
    .define();

// Layer B — shows only communes where No wins: swap binding order, NONEGATIVE drops the rest
myMap.layer("comuni")
    .data({ url: DATA_URL, type: "csv" })
    .binding({ lookup: "cod_istat", value: "voti_si|voti_no", title: "desc_com" })  // ← swapped
    .type("CHART|USER|3D|DIFFERENCE|HEADTAIL|AGGREGATE|RECT|RELOCATE|SUM|VALUES|NONEGATIVE|NOLEGEND")
    .style({ name: "chart_no", userdraw: "pinnacleChart", /* ... */ showdata: "true" })
    .meta({ name: "chart_no", tooltip: "..." })
    .define();

Binding order determines sign: "a|b" → b − a. With NONEGATIVE, only locations where the result > 0 get a chart drawn. Swapping a and b between two layers gives "A wins" vs "B wins" without any data pre-processing. {{raw.fieldname}} in tooltip accesses fields listed in datafields — useful for pre-formatted strings (e.g. "12.345" from .toLocaleString()).

Rotated arrowChart wrapper — tilt arrows left/right to distinguish two groups visually:

Redirect args.target to a rotated child <g> before calling the standard arrowChart, then restore it. The outer group keeps its ixmaps-assigned translate; only the drawn shapes rotate.

window.ixmaps = window.ixmaps || {};

function makeRotatedArrowChart(angle) {
  return function(SVGDocument, args) {
    var origTarget = args.target;
    var rotG = d3.select(origTarget)
                 .append("g")
                 .attr("transform", "rotate(" + angle + ")")
                 .node();
    args.target = rotG;
    var result = ixmaps.arrowChart(SVGDocument, args);
    args.target = origTarget;
    return result;
  };
}
ixmaps.arrowChartLeft_init  = function(s,a) { if (typeof ixmaps.arrowChart_init === "function") ixmaps.arrowChart_init(s,a); };
ixmaps.arrowChartRight_init = function(s,a) { if (typeof ixmaps.arrowChart_init === "function") ixmaps.arrowChart_init(s,a); };
ixmaps.arrowChartLeft  = makeRotatedArrowChart(-15);   // ← tilts left  (e.g. CS/left bloc)
ixmaps.arrowChartRight = makeRotatedArrowChart(+15);   // → tilts right (e.g. CDX/right bloc)

Then use userdraw: "arrowChartLeft" / userdraw: "arrowChartRight" in .style().

Simultaneous theme stacking on one layer — two themes rendered at the same position:

Calling .define() multiple times on the same layer name adds themes (they stack). Use this when you need two independent visual signals at the same geo-coordinates (e.g. one red arrow group + one blue arrow group). Each theme must have a distinct name in .meta() so they can be removed independently.

// Both themes render simultaneously on layer "sedi"
// Pre-filtered: csWins has only sedes where CS leads; cdWins only where CDX leads
myMap.layer("sedi")
  .data({ obj: csWins, type: "json" })
  .binding({ geo: "sez_da", value: "margin" })
  .type("CHART|USER|SIZE|VALUES")
  .style({ userdraw: "arrowChartLeft", colorscheme: ["#e74c3c","#e74c3c"],
           normalsizevalue: 100, rangescale: 0.5, fillopacity: 0.85,
           showdata: "true", units: " voti", valuedecimals: 0 })
  .meta({ name: "cs_dom", title: "CS in testa", tooltip: "..." })
  .define();                               // ← adds theme, does NOT replace

myMap.layer("sedi")
  .data({ obj: cdWins, type: "json" })
  .binding({ geo: "sez_da", value: "margin" })
  .type("CHART|USER|SIZE|VALUES")
  .style({ userdraw: "arrowChartRight", colorscheme: ["#2980b9","#2980b9"],
           normalsizevalue: 100, rangescale: 0.5, fillopacity: 0.85,
           showdata: "true", units: " voti", valuedecimals: 0 })
  .meta({ name: "cd_dom", title: "CDX in testa", tooltip: "..." })
  .define();                               // ← stacks on top of cs_dom

// To refresh: remove both by name, then redefine
myMap.then(function(api) {
  try { api.removeTheme("cs_dom"); } catch(e) {}
  try { api.removeTheme("cd_dom"); } catch(e) {}
  // ... redefine both
});

⚠️ Stacking only works correctly when the two datasets are mutually exclusive per feature (e.g. pre-filtered so each sede appears in at most one theme). If the same sez_da id appears in both, both themes draw at that location and visually overlap.

Invisible point anchor layer — load centroid geometry without rendering anything:

// Required when CHART|USER layers need to snap to precise urban centroids
// For POINT geometry: colorscheme:["none"] + scale:0 suppress the dot completely.
// (Do NOT rely on fillopacity:0 — ixMaps coerces it to 1, so it never hides anything.)
myMap.layer("centroids")
    .data({ url: CENTROIDS_URL, type: "geojson" })
    .binding({ geo: "geometry", id: "PRO_COM", title: "PRO_COM" })
    .type("FEATURE|NOLEGEND")
    .style({
        colorscheme: ["none"],
        scale:       0,         // ← required for point geometry
        linecolor:   "none",
        linewidth:   0,
        showdata:    "true"
    })
    .define();

Diverging scales, density patterns, road-tracing, SEQUENCE charts → API_REFERENCE.md § Special Cases Complete working examples → EXAMPLES.md Data preprocessing (data.js) → DATA_JS_GUIDE.md Symbols/icons → SYMBOLS_GUIDE.md Troubleshooting → TROUBLESHOOTING.md

---

Facet Sidebar (filter panel updated on zoom/pan)

A clickable facet panel that auto-updates on every zoom/pan/filter. Requires three CDN plugins (format.js, facet.js, show_facets.js), a sidebar <div id="show-facets-div">, an override of ixmaps.statistics (calls ixmaps.data.getFacets → showFacets), wired via myMap.on("layerdraw", …). Pass "NONUMERIC" to getFacets for numeric-looking category fields; a facet field matching the theme's value binding auto-picks up theme colors.

Full sidebar HTML/CSS, ixmaps.statistics hook, layerdraw wiring, clear-filter, button-style overrides → FACETS_GUIDE.md

---

Overlay Indicator Layer (small status dot on top of main bubbles)

A second CHART|BUBBLE|CATEGORICAL|NOLEGEND layer drawn over the main bubbles to show a per-item status flag (risk class, alert state) without touching the primary colors. Add a constant _dot size field, filter to only meaningful states, use scale: ~0.1 + align: "bottom". NOLEGEND must be in the type string so the layerdraw/statistics handler skips it.

Full pattern, key rules, define-then-add (ixmaps.layer(...).define() + myMap.layer(theme, "direct")) → FACETS_GUIDE.md § Overlay Indicator Layer

---

CSS Conflicts with External Frameworks (Bootstrap etc.)

Never load Bootstrap 3 alongside ixmaps — its .hidden { display:none !important } silently hides ixmaps' toolbar / tooltip / contextmenu (ixmaps toggles them via inline style.display, which !important beats). Ship the ~35-line standalone facet CSS instead. On dark basemaps, force #tooltip text color. Always run the tooltip/contextmenu class-cleanup inside myMap.then().

Standalone facet CSS, dark-basemap tooltip fix, tooltip/contextmenu cleanup, attribute-selector fallback → CSS_INTEROP.md