✨ Implement add_marker to add a marker to the Aladin Lite view

js/models/event_handler.js

@@ -259,6 +259,7 @@ export default class EventHandler {
     });
 
     this.eventHandlers = {
+      add_marker: this.messageHandler.handleAddMarker,
       change_fov: this.messageHandler.handleChangeFoV,
       goto_ra_dec: this.messageHandler.handleGotoRaDec,
       save_view_as_image: this.messageHandler.handleSaveViewAsImage,

js/models/message_handler.js

@@ -9,6 +9,25 @@ export default class MessageHandler {
     this.model = model;
   }
 
+  handleAddMarker(msg) {
+    const options = convertOptionNamesToCamelCase(msg["options"] || {});
+    if (!options.name) options.name = "markers";
+    const rawMarkers = msg["markers"];
+    const catalog = A.catalog(options);
+    this.aladin.addCatalog(catalog);
+    const markers = [];
+    for (const marker of rawMarkers) {
+      const position = marker["position"].split(" ");
+      markers.push(
+        A.marker(parseFloat(position[0]), parseFloat(position[1]), {
+          popupTitle: marker["title"],
+          popupDesc: marker["description"],
+        }),
+      );
+    }
+    catalog.addSources(markers);
+  }
+
   handleChangeFoV(msg) {
     this.aladin.setFoV(msg["fov"]);
   }

src/ipyaladin/utils/marker.py

@@ -0,0 +1,38 @@
+from typing import Tuple, Union
+
+from astropy.coordinates import SkyCoord
+from ipyaladin.utils._coordinate_parser import parse_coordinate_string
+
+
+class Marker:
+    """A class representing a marker in Aladin Lite."""
+
+    def __init__(
+        self,
+        position: Union[str, SkyCoord, Tuple[float, float]],
+        title: str,
+        description: str,
+    ) -> None:
+        self.title = title
+        self.description = description
+        if isinstance(position, SkyCoord):
+            self.position = f"{position.ra.deg} {position.dec.deg}"
+        elif isinstance(position, str):
+            sc = parse_coordinate_string(position)
+            self.position = f"{sc.ra.deg} {sc.dec.deg}"
+        else:
+            self.position = f"{position[0]} {position[1]}"
+
+    def to_dict(self) -> dict:
+        """Convert the marker to a dictionary.
+
+        Returns
+        -------
+        dict
+            The marker as a dictionary
+        """
+        return {
+            "position": self.position,
+            "title": self.title,
+            "description": self.description,
+        }

src/ipyaladin/widget.py

@@ -25,6 +25,7 @@
 
 from .utils.exceptions import WidgetCommunicationError
 from .utils._coordinate_parser import parse_coordinate_string
+from .utils.marker import Marker
 
 try:
     from regions import (
@@ -389,6 +390,30 @@ def target(self, target: Union[str, SkyCoord]) -> None:
             }
         )
 
+    def add_marker(
+        self, markers: Union[Marker, List[Marker]], **catalog_options: any
+    ) -> None:
+        """Add a marker to the Aladin Lite widget.
+
+        Parameters
+        ----------
+        markers : Marker or list[Marker]
+            The marker(s) to add to the widget. It can be given as a single `Marker`
+            object or as a list of `Marker` objects.
+        catalog_options : any
+            The options for the catalog. See the `Aladin Lite catalog options
+            <https://cds-astro.github.io/aladin-lite/global.html#CatalogOptions>`_
+        """
+        if not isinstance(markers, list):
+            markers = [markers]
+        self.send(
+            {
+                "event_name": "add_marker",
+                "markers": [marker.to_dict() for marker in markers],
+                "options": catalog_options,
+            }
+        )
+
     def _save_file(self, path: str, buffer: bytes) -> None:
         """Save a file from a buffer.