fix: Dynamically compute default zoom/center for map traces

CONTRIBUTING.md

@@ -405,8 +405,10 @@ All traces modules set:
   This object is used to generate the plot-schema JSON.
 - `_module.supplyDefaults`: Takes in input trace settings and coerces them into "full" settings
   under `gd._fullData`. This one is called during the figure-wide `Plots.supplyDefaults` routine.
-  Note that the `supplyDefaults` method performance should scale with the number of attributes (**not** the
-  number of data points - so it should not loop over any data arrays).
+  As a rule, `supplyDefaults` performance should scale with the number of attributes rather than
+  the number of data points, so avoid looping over data arrays in this function. That being said,
+  there are a few exceptions to this rule due to technical requirements (`fitbounds` on map subplots).
+  The same guidance applies to `_module.supplyLayoutDefaults`.
 - `_module.calc`: Converts inputs data into "calculated" (or sanitized) data. This one is called during
   the figure-wide `Plots.doCalcdata` routine. The `calc` method is allowed to
   scale with the number of data points and is in general more costly than `supplyDefaults`.

draftlogs/7884_fix.md

@@ -0,0 +1 @@
+ - Fix `scattermap`, `densitymap` traces not showing all points by dynamically computing `center`, `zoom` values [[#7884](https://github.com/plotly/plotly.js/pull/7884)], with thanks to @palmerusaf and @DhruvGarg111 for the contributions!

src/plots/map/constants.js

@@ -70,17 +70,15 @@ var styleValuesMap = sortObjectKeys(stylesMap);
 
 module.exports = {
     styleValueDflt: 'basic',
-    stylesMap: stylesMap,
-    styleValuesMap: styleValuesMap,
-
+    stylesMap,
+    styleValuesMap,
     traceLayerPrefix: 'plotly-trace-layer-',
     layoutLayerPrefix: 'plotly-layout-layer-',
-
     missingStyleErrorMsg: [
         'No valid maplibre style found, please set `map.style` to one of:',
         styleValuesMap.join(', '),
         'or use a tile service.'
     ].join('\n'),
-
-    mapOnErrorMsg: 'Map error.'
+    mapOnErrorMsg: 'Map error.',
+    fitBoundsPadding: 20
 };

src/plots/map/get_map_fit_bounds.ts

@@ -0,0 +1,55 @@
+import { computeBbox } from '../../lib/geo_location_utils';
+import type { MapLayout, ScattermapData } from '../../types/generated/schema';
+
+// Same shape as the user-facing `map.bounds` attribute, but with all fields required
+type LonLatBox = Required<NonNullable<MapLayout['bounds']>>;
+
+// Minimal shape of the fullData entries this helper reads
+interface FitBoundsTrace extends Pick<ScattermapData, 'subplot' | 'visible'> {
+    // Tighten lat/lon to be more specific than default
+    lat?: ArrayLike<number>;
+    lon?: ArrayLike<number>;
+    // Broaden type since this could run against multiple trace types
+    type?: string;
+}
+
+/**
+ * Compute a lon/lat bounding box from lonlat-bearing traces (`scattermap`,
+ * `densitymap`) on the given map subplot.
+ *
+ * Returns null when:
+ *   - no fittable data exists on the subplot;
+ *   - a location-based trace (`choroplethmap`) is present — those carry
+ *     `locations`/`geojson`, not raw lon/lat, and need geojson bbox handling
+ *     that isn't implemented here.
+ *
+ * @param fullData - The full data array (post supply-defaults)
+ * @param subplotId - e.g. `'map'`, `'map2'`
+ */
+export function getMapFitBounds(fullData: FitBoundsTrace[], subplotId: string): LonLatBox | null {
+    const coordinates: [number, number][] = [];
+
+    for (const trace of fullData) {
+        if (trace.subplot !== subplotId || trace.visible !== true) continue;
+
+        // choroplethmap traces carry locations/geojson, not raw lon/lat; bail
+        // out rather than frame around a subset of the subplot's data.
+        if (trace.type === 'choroplethmap') return null;
+
+        const { lat, lon } = trace;
+        if (!lon || !lat) continue;
+
+        const len = Math.min(lon.length, lat.length);
+        for (let j = 0; j < len; j++) {
+            const lo = lon[j];
+            const la = lat[j];
+            if (Number.isFinite(lo) && Number.isFinite(la)) coordinates.push([lo, la]);
+        }
+    }
+
+    const bbox = computeBbox({ type: 'MultiPoint', coordinates });
+    if (!bbox) return null;
+
+    const [west, south, east, north] = bbox;
+    return { west, east, south, north };
+}

src/plots/map/index.js

@@ -55,15 +55,6 @@ exports.plot = function plot(gd) {
             fullLayout[id]._subplot = map;
         }
 
-        if(!map.viewInitial) {
-            map.viewInitial = {
-                center: Lib.extendFlat({}, opts.center),
-                zoom: opts.zoom,
-                bearing: opts.bearing,
-                pitch: opts.pitch
-            };
-        }
-
         map.plot(subplotCalcData, fullLayout, gd._promises);
     }
 };