Store Aladin API calls if widget is not ready

observe _is_loaded traitlet for a change to run all the stored API calls in the right order

Author: bmatthieu3

examples/09_Displaying_Shapes.ipynb

@@ -54,15 +54,6 @@
    "outputs": [],
    "source": [
     "aladin = Aladin(target=\"M 51\", fov=1.2)\n",
-    "aladin"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": [
     "aladin.add_graphic_overlay_from_stcs(\n",
     "    \"\"\"Polygon ICRS 202.63748 47.24951 202.46382 47.32391 202.46379 47.32391 202.45459\n",
     "    47.32391 202.34527 47.20597 202.34527 47.20596 202.34529 47.19710 202.51870\n",
@@ -77,7 +68,9 @@
     ")\n",
     "aladin.add_graphic_overlay_from_stcs(\n",
     "    \"Circle ICRS 202.4656816 +47.1999842 0.04\", color=\"#4488ee\"\n",
-    ")"
+    ")\n",
+    "\n",
+    "aladin"
    ]
   },
   {
@@ -191,45 +184,16 @@
    "source": [
     "aladin.add_graphic_overlay_from_region([circle, ellipse, line, polygon, rectangle])"
    ]
-  }
- ],
- "metadata": {
-  "kernelspec": {
-   "display_name": "base",
-   "language": "python",
-   "name": "python3"
   },
-  "language_info": {
-   "codemirror_mode": {
-    "name": "ipython",
-    "version": 3
-   },
-   "file_extension": ".py",
-   "mimetype": "text/x-python",
-   "name": "python",
-   "nbconvert_exporter": "python",
-   "pygments_lexer": "ipython3",
-   "version": "3.11.8"
-  },
-  "toc": {
-   "base_numbering": 1,
-   "nav_menu": {},
-   "number_sections": false,
-   "sideBar": false,
-   "skip_h1_title": false,
-   "title_cell": "Table of Contents",
-   "title_sidebar": "Contents",
-   "toc_cell": false,
-   "toc_position": {},
-   "toc_section_display": false,
-   "toc_window_display": false
-  },
-  "vscode": {
-   "interpreter": {
-    "hash": "85bb43f988bdbdc027a50b6d744a62eda8a76617af1f4f9b115d38242716dbac"
-   }
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
- },
+ ],
+ "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 4
 }

src/ipyaladin/utils/call_store.py

@@ -0,0 +1,24 @@
+from traitlets import (
+    Any,
+)
+
+
+class CallStore:
+    """A simple call store.
+
+    This is used to store user calls to Aladin API in case the widget is not properly
+    loaded on the JS side. Whenever it gets loaded, then the calls are run in the
+    inserting order.
+    """
+
+    def __init__(self) -> None:
+        self.calls = []
+
+    def add(self, func: Any, *args: Any, **kwargs: Any) -> None:
+        """Add a call to the store."""
+        self.calls.append((func, args, kwargs))
+
+    def run_all(self) -> None:
+        """Run all the stored calls in the right order."""
+        for func, args, kwargs in self.calls:
+            func(*args, **kwargs)

src/ipyaladin/widget.py

@@ -11,7 +11,6 @@
 import io
 import pathlib
 from pathlib import Path
-import time
 from typing import ClassVar, Dict, Final, List, Optional, Tuple, Union
 
 try:  # drop this clause when we drop python 3.9
@@ -32,6 +31,7 @@
 
 from .utils.exceptions import WidgetReducedError, WidgetNotReadyError
 from .utils._coordinate_parser import _parse_coordinate_string
+from .utils.call_store import CallStore
 from .elements.error_shape import (
     CircleError,
     EllipseError,
@@ -87,6 +87,8 @@
 def widget_should_be_loaded(function: Callable) -> Callable:
     """Check if the widget is ready to execute a function.
 
+    Store the call for a later execution.
+
     Parameters
     ----------
     function : Callable
@@ -103,6 +105,9 @@ def widget_should_be_loaded(function: Callable) -> Callable:
     def wrapper(self: Any, *args: Any, **kwargs: Any) -> Any:
         """Check if the widget is ready to execute a function.
 
+        If not, do not exit the call and store it so that it is
+        called later when the widget is ready.
+
         Parameters
         ----------
         self : any
@@ -119,12 +124,9 @@ def wrapper(self: Any, *args: Any, **kwargs: Any) -> Any:
 
         """
         if not getattr(self, "_is_loaded", False):
-            # this is an arbitrary waiting time
-            # it should correspond to the downloading time of the npm package
-            duration = 0.1
-            time.sleep(duration)
-            # set ready to True to avoid waiting twice
-            self._is_loaded = True
+            self._call_store.add(function, self, *args, **kwargs)
+            return None
+
         return function(self, *args, **kwargs)
 
     return wrapper
@@ -140,6 +142,8 @@ class Aladin(anywidget.AnyWidget):
     _esm: Final = pathlib.Path(__file__).parent / "static" / "widget.js"
     _css: Final = pathlib.Path(__file__).parent / "static" / "widget.css"
 
+    _call_store = CallStore()
+
     # Options for the view initialization
     _init_options = traitlets.Dict().tag(sync=True)
     _height = Int(400).tag(sync=True, init_option=True)
@@ -241,6 +245,17 @@ def __init__(self, *args: any, **init_options: any) -> None:
         self._init_options = init_options
         self.on_msg(self._handle_custom_message)
 
+        def on_load_change(change: traitlets.Dict) -> None:
+            if change["new"]:
+                self._call_store.run_all()
+
+        # There can be a race condition if the JS is already load
+        # leading to _is_loaded = True before observing it.
+        # If this is the case there should not be any problem because no python commands
+        # are expected to be called on an object before the object itself
+        # is instanciated.
+        self.observe(on_load_change, names="_is_loaded")
+
     def _handle_custom_message(self, _: any, message: dict, buffers: any) -> None:
         event_type = message["event_type"]
         if (