Add visible_callback

examples/markers_or_density.ipynb

@@ -0,0 +1,134 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "15eefe2f-7d1b-4814-9a5b-3b57df451fd7",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from ipyleaflet import GeoData, Map, basemaps, LayersControl, WidgetControl\n",
+    "from ipywidgets import FloatSlider\n",
+    "import xarray_leaflet\n",
+    "import geopandas as gpd\n",
+    "import matplotlib.pyplot as plt"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "30114fbe-e6ef-4547-98ab-28686f8980b1",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "!wget https://raw.githubusercontent.com/drei01/geojson-world-cities/master/cities.geojson"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "ab8cd637-be46-4953-96a8-edd918aeccf8",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "df = gpd.read_file(\"cities.geojson\")\n",
+    "df.geometry = df.geometry.centroid\n",
+    "measurement = \"mask\"\n",
+    "df[measurement] = 1"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "55a78adf",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "m = Map(center=(34.36519854648025, -47.3743535773436), zoom=3, basemap=basemaps.CartoDB.DarkMatter, interpolation='nearest')\n",
+    "m"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "6180d7f5-05e5-4f56-b179-78cc8f581f1a",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "class LayerManager:\n",
+    "\n",
+    "    def __init__(self, df, measurement):\n",
+    "        self.df = df\n",
+    "        self.measurement = measurement\n",
+    "        self.marker_layer = None\n",
+    "\n",
+    "    def visible_callback(self, m, da, bbox):\n",
+    "        # show density if there are too many points\n",
+    "        # otherwise show individual markers\n",
+    "        density_visible = da.sum() > 500\n",
+    "        if self.marker_layer:\n",
+    "            # remove markers\n",
+    "            m.remove(self.marker_layer)\n",
+    "            self.marker_layer = None\n",
+    "        if not density_visible:\n",
+    "            # only show markers that are on the map view\n",
+    "            self.marker_layer = GeoData(geo_dataframe=self.df.clip(bbox))\n",
+    "            m.add(self.marker_layer)\n",
+    "        return density_visible\n",
+    "\n",
+    "layer_manager = LayerManager(df, measurement)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "2ab54311-d960-4b51-9623-e8d91b97ad75",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "l = df.leaflet.plot(m, measurement=\"mask\", colormap=plt.cm.inferno, visible_callback=layer_manager.visible_callback)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "fe1ea3ac-7c1b-4443-8f82-2bffe819b27c",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "layers_control = LayersControl(position='topright')\n",
+    "m.add_control(layers_control)\n",
+    "\n",
+    "opacity_slider = FloatSlider(description='Opacity:', min=0, max=1, value=1)\n",
+    "\n",
+    "def set_opacity(change):\n",
+    "    l.opacity = change['new']\n",
+    "\n",
+    "opacity_slider.observe(set_opacity, names='value')\n",
+    "slider_control = WidgetControl(widget=opacity_slider, position='bottomleft')\n",
+    "m.add_control(slider_control)"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "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": "3.10.5"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}

xarray_leaflet/xarray_leaflet.py

@@ -1,7 +1,7 @@
 import asyncio
 import os
 import tempfile
-from typing import Optional
+from typing import Callable, Optional
 
 import geopandas as gpd
 import matplotlib as mpl
@@ -62,6 +62,7 @@ def plot(
         resampling=Resampling.nearest,
         get_base_url=None,
         measurement: Optional[str] = None,
+        visible_callback: Optional[Callable] = None,
     ):
         """Display an array as an interactive map.
 
@@ -114,6 +115,13 @@ def plot(
             A function taking the window URL and returning the base URL to use.
         measurement: str, optional
             The geocube measurement.
+        visible_callback: callable, optional
+            A callable taking the following arguments:
+            - the ipyleaflet.Map
+            - the xarray.DataArray of the visible region
+            - the mercantile.LngLatBbox of the visible region
+
+            and returning True if the layer should be shown, False otherwise.
 
         Returns
         -------
@@ -125,6 +133,7 @@ def plot(
 
         if self.is_vector:
             # source is a GeoDataFrame (vector)
+            self.visible_callback = visible_callback
             if measurement is None:
                 raise RuntimeError("You must provide a 'measurement'.")
             self.measurement = measurement
@@ -365,6 +374,12 @@ def _get_vector_tiles(self, change=None):
         if self.dynamic:
             llbbox = mercantile.LngLatBbox(west, south, east, north)
             da_visible = self.zvect.get_da_llbbox(llbbox, z)
+            # check if we must show the layer
+            if self.visible_callback and not self.visible_callback(
+                self.m, da_visible, llbbox
+            ):
+                self.m.remove_control(self.spinner_control)
+                return
             if da_visible is None:
                 self.max_value = 0
             else:
@@ -600,7 +615,7 @@ async def async_fit_bounds(self):
 class DataArrayLeaflet(Leaflet):
     """A DataArraye extension for tiled map plotting, based on (ipy)leaflet."""
 
-    def __init__(self, da: xr.DataArray = None):
+    def __init__(self, da: xr.DataArray):
         self._da = da
         self._da_selected = None
         self.is_vector = False
@@ -610,6 +625,6 @@ def __init__(self, da: xr.DataArray = None):
 class GeoDataFrameLeaflet(Leaflet):
     """A GeoDataFrame extension for tiled map plotting, based on (ipy)leaflet."""
 
-    def __init__(self, df: gpd.GeoDataFrame = None):
+    def __init__(self, df: gpd.GeoDataFrame):
         self._df = df
         self.is_vector = True