🥅 Add error when exporting the WCS while the widget is reduced when h…

…idden

js/models/event_handler.js

@@ -160,7 +160,11 @@ export default class EventHandler {
 
     this.aladin.on("resizeChanged", (width, height) => {
       // Skip resize event when the div is hidden
-      if (width === 1 && height === 1) return;
+      if (width === 1 && height === 1) {
+        this.model.set("_is_reduced", true);
+        this.model.save_changes();
+        return;
+      } else this.model.set("_is_reduced", false);
       this.updateWCS();
       this.update2AxisFoV();
       this.model.set("_height", height);

src/ipyaladin/utils/exceptions.py

@@ -4,3 +4,11 @@ class WidgetCommunicationError(OSError):
     def __init__(self, message: str) -> None:
         self.message = message
         super(WidgetCommunicationError, self).__init__(message)
+
+
+class WidgetReducedError(ValueError):
+    """Error raised when a widget is reduced to a point when hidden."""
+
+    def __init__(self, message: str) -> None:
+        self.message = message
+        super(WidgetReducedError, self).__init__(message)

src/ipyaladin/widget.py

@@ -23,7 +23,7 @@
 import numpy as np
 import traitlets
 
-from .utils.exceptions import WidgetCommunicationError
+from .utils.exceptions import WidgetCommunicationError, WidgetReducedError
 from .utils._coordinate_parser import parse_coordinate_string
 
 
@@ -213,6 +213,13 @@ class Aladin(anywidget.AnyWidget):
         "to convert the view to an astropy.HDUList",
     ).tag(sync=True)
 
+    # Temporary traitlets for widget size problem
+    _is_reduced = Bool(
+        False,
+        help="A private trait that stores if the widget "
+        "is reduced in size when hidden.",
+    ).tag(sync=True)
+
     init_options = traitlets.List(trait=Any()).tag(sync=True)
 
     @default("init_options")
@@ -290,6 +297,10 @@ def wcs(self) -> WCS:
             An astropy WCS object representing the world coordinate system.
 
         """
+        if self._is_reduced:
+            raise WidgetReducedError(
+                "WCS might be wrong if the Aladin Lite widget is not visible"
+            )
         if self._wcs == {}:
             raise WidgetCommunicationError(
                 "The world coordinate system is not available. "