✨ Implement WCS and 2 axis FoV recovery

js/models/event_handler.js

@@ -42,6 +42,7 @@ export default class EventHandler {
       }
       jsTargetLock.lock();
       const raDec = [position.ra, position.dec];
+      this.model.set("_wcs", this.aladin.getViewWCS());
       this.model.set("_target", `${raDec[0]} ${raDec[1]}`);
       this.model.save_changes();
     });
@@ -68,7 +69,13 @@ export default class EventHandler {
       }
       jsFovLock.lock();
       // fov MUST be cast into float in order to be sent to the model
+      this.model.set("_wcs", this.aladin.getViewWCS());
       this.model.set("_fov", parseFloat(fov.toFixed(5)));
+      const fov_xy = this.aladin.getFov();
+      this.model.set("_fov_xy", {
+        x: fov_xy[0],
+        y: fov_xy[1],
+      });
       this.model.save_changes();
     });
 

js/widget.js

@@ -24,6 +24,15 @@ function initAladinLite(model, el) {
   const raDec = initOptions["target"].split(" ");
   aladin.gotoRaDec(raDec[0], raDec[1]);
 
+  // Set current FoV and WCS
+  const FoV = aladin.getFov();
+  model.set("_fov_xy", {
+    x: FoV[0],
+    y: FoV[1],
+  });
+  model.set("_wcs", aladin.getViewWCS());
+  model.save_changes();
+
   el.appendChild(aladinDiv);
   return { aladin, aladinDiv };
 }

src/ipyaladin/widget.py

@@ -7,14 +7,15 @@
 
 import pathlib
 import typing
-from typing import ClassVar, Union, Final, Optional
+from typing import ClassVar, Union, Final, Optional, Tuple
 import warnings
 
 import anywidget
 from astropy.table.table import QTable
 from astropy.table import Table
 from astropy.coordinates import SkyCoord, Angle
 import traitlets
+from astropy.wcs import WCS
 
 try:
     from regions import (
@@ -122,6 +123,10 @@ class Aladin(anywidget.AnyWidget):
     grid_opacity = Float(0.5).tag(sync=True, init_option=True)
     grid_options = traitlets.Dict().tag(sync=True, init_option=True)
 
+    # Values
+    _wcs = traitlets.Dict().tag(sync=True)
+    _fov_xy = traitlets.Dict().tag(sync=True)
+
     # content of the last click
     clicked_object = traitlets.Dict().tag(sync=True)
     # listener callback is on the python side and contains functions to link to events
@@ -161,6 +166,35 @@ def _handle_custom_message(self, _: any, message: dict, __: any) -> None:
         elif event_type == "select" and "select" in self.listener_callback:
             self.listener_callback["select"](message_content)
 
+    @property
+    def wcs(self) -> WCS:
+        """The world coordinate system of the Aladin Lite widget.
+
+        Returns
+        -------
+        WCS
+            An astropy WCS object representing the world coordinate system.
+
+        """
+        if "RADECSYS" in self._wcs:  # RADECSYS keyword is deprecated for astropy.WCS
+            self._wcs["RADESYS"] = self._wcs.pop("RADECSYS")
+        return WCS(self._wcs)
+
+    @property
+    def fov_xy(self) -> Tuple[Angle, Angle]:
+        """The field of view of the Aladin Lite along the two axis.
+
+        Returns
+        -------
+        tuple[Angle, Angle]
+            A tuple of astropy.units.Angle objects representing the field of view.
+
+        """
+        return (
+            Angle(self._fov_xy["x"], unit="deg"),
+            Angle(self._fov_xy["y"], unit="deg"),
+        )
+
     @property
     def fov(self) -> Angle:
         """The field of view of the Aladin Lite widget along the horizontal axis.