feat: Add tooltip to Altair agent portrayal (#2795)

mesa/examples/basic/boltzmann_wealth_model/app.py

@@ -14,8 +14,9 @@
 
 def agent_portrayal(agent):
     return AgentPortrayalStyle(
-        color=agent.wealth
-    )  # we are using a colormap to translate wealth to color
+        color=agent.wealth,
+        tooltip={"Agent ID": agent.unique_id, "Wealth": agent.wealth},
+    )
 
 
 model_params = {
@@ -41,7 +42,7 @@ def post_process(chart):
     """Post-process the Altair chart to add a colorbar legend."""
     chart = chart.encode(
         color=alt.Color(
-            "color:N",
+            "original_color:Q",
             scale=alt.Scale(scheme="viridis", domain=[0, 10]),
             legend=alt.Legend(
                 title="Wealth",
@@ -63,12 +64,12 @@ def post_process(chart):
 renderer = SpaceRenderer(model, backend="altair")
 # Can customize the grid appearance.
 renderer.draw_structure(grid_color="black", grid_dash=[6, 2], grid_opacity=0.3)
-renderer.draw_agents(agent_portrayal=agent_portrayal, cmap="viridis", vmin=0, vmax=10)
-
+renderer.draw_agents(agent_portrayal=agent_portrayal)
 # The post_process function is used to modify the Altair chart after it has been created.
 # It can be used to add legends, colorbars, or other visual elements.
 renderer.post_process = post_process
 
+
 # Creates a line plot component from the model's "Gini" datacollector.
 GiniPlot = make_plot_component("Gini")
 

mesa/visualization/backends/altair_backend.py

@@ -1,4 +1,9 @@
-# noqa: D100
+"""Altair-based renderer for Mesa spaces.
+
+This module provides an Altair-based renderer for visualizing Mesa model spaces,
+agents, and property layers with interactive charting capabilities.
+"""
+
 import warnings
 from collections.abc import Callable
 from dataclasses import fields
@@ -75,6 +80,7 @@ def collect_agent_data(
             "stroke": [],  # Stroke color
             "strokeWidth": [],
             "filled": [],
+            "tooltip": [],
         }
 
         # Import here to avoid circular import issues
@@ -129,6 +135,7 @@ def collect_agent_data(
                     linewidths=dict_data.pop(
                         "linewidths", style_fields.get("linewidths")
                     ),
+                    tooltip=dict_data.pop("tooltip", None),
                 )
                 if dict_data:
                     ignored_keys = list(dict_data.keys())
@@ -184,6 +191,7 @@ def collect_agent_data(
             # FIXME: Make filled user-controllable
             filled_value = True
             arguments["filled"].append(filled_value)
+            arguments["tooltip"].append(aps.tooltip)
 
         final_data = {}
         for k, v in arguments.items():
@@ -217,79 +225,71 @@ def draw_agents(
         if arguments["loc"].size == 0:
             return None
 
-        # To get a continuous scale for color the domain should be between [0, 1]
-        # that's why changing the the domain of strokeWidth beforehand.
-        stroke_width = [data / 10 for data in arguments["strokeWidth"]]
-
-        # Agent data preparation
-        df_data = {
-            "x": arguments["loc"][:, 0],
-            "y": arguments["loc"][:, 1],
-            "size": arguments["size"],
-            "shape": arguments["shape"],
-            "opacity": arguments["opacity"],
-            "strokeWidth": stroke_width,
-            "original_color": arguments["color"],
-            "is_filled": arguments["filled"],
-            "original_stroke": arguments["stroke"],
-        }
-        df = pd.DataFrame(df_data)
-
-        # To ensure distinct shapes according to agent portrayal
-        unique_shape_names_in_data = df["shape"].unique().tolist()
-
-        fill_colors = []
-        stroke_colors = []
-        for i in range(len(df)):
-            filled = df["is_filled"][i]
-            main_color = df["original_color"][i]
-            stroke_spec = (
-                df["original_stroke"][i]
-                if isinstance(df["original_stroke"][i], str)
-                else None
-            )
-            if filled:
-                fill_colors.append(main_color)
-                stroke_colors.append(stroke_spec)
+        # Prepare a list of dictionaries, which is a robust way to create a DataFrame
+        records = []
+        for i in range(len(arguments["loc"])):
+            record = {
+                "x": arguments["loc"][i][0],
+                "y": arguments["loc"][i][1],
+                "size": arguments["size"][i],
+                "shape": arguments["shape"][i],
+                "opacity": arguments["opacity"][i],
+                "strokeWidth": arguments["strokeWidth"][i]
+                / 10,  # Scale for continuous domain
+                "original_color": arguments["color"][i],
+            }
+            # Add tooltip data if available
+            tooltip = arguments["tooltip"][i]
+            if tooltip:
+                record.update(tooltip)
+
+            # Determine fill and stroke colors
+            if arguments["filled"][i]:
+                record["viz_fill_color"] = arguments["color"][i]
+                record["viz_stroke_color"] = (
+                    arguments["stroke"][i]
+                    if isinstance(arguments["stroke"][i], str)
+                    else None
+                )
             else:
-                fill_colors.append(None)
-                stroke_colors.append(main_color)
-        df["viz_fill_color"] = fill_colors
-        df["viz_stroke_color"] = stroke_colors
+                record["viz_fill_color"] = None
+                record["viz_stroke_color"] = arguments["color"][i]
+
+            records.append(record)
+
+        df = pd.DataFrame(records)
+
+        # Ensure all columns that should be numeric are, handling potential Nones
+        numeric_cols = ["x", "y", "size", "opacity", "strokeWidth", "original_color"]
+        for col in numeric_cols:
+            if col in df.columns:
+                df[col] = pd.to_numeric(df[col], errors="coerce")
+
+        # Get tooltip keys from the first valid record
+        tooltip_list = ["x", "y"]
+        if any(t is not None for t in arguments["tooltip"]):
+            first_valid_tooltip = next(
+                (t for t in arguments["tooltip"] if t is not None), None
+            )
+            if first_valid_tooltip is not None:
+                tooltip_list.extend(first_valid_tooltip.keys())
 
         # Extract additional parameters from kwargs
-        # FIXME: Add more parameters to kwargs
         title = kwargs.pop("title", "")
         xlabel = kwargs.pop("xlabel", "")
         ylabel = kwargs.pop("ylabel", "")
+        # FIXME: Add more parameters to kwargs
 
-        # Tooltip list for interactivity
-        # FIXME: Add more fields to tooltip (preferably from agent_portrayal)
-        tooltip_list = ["x", "y"]
-
-        # Handle custom colormapping
-        cmap = kwargs.pop("cmap", "viridis")
-        vmin = kwargs.pop("vmin", None)
-        vmax = kwargs.pop("vmax", None)
-
-        color_is_numeric = np.issubdtype(df["original_color"].dtype, np.number)
-        if color_is_numeric:
-            color_min = vmin if vmin is not None else df["original_color"].min()
-            color_max = vmax if vmax is not None else df["original_color"].max()
-
-            fill_encoding = alt.Fill(
-                "original_color:Q",
-                scale=alt.Scale(scheme=cmap, domain=[color_min, color_max]),
-            )
-        else:
-            fill_encoding = alt.Fill(
-                "viz_fill_color:N",
-                scale=None,
-                title="Color",
-            )
+        color_is_numeric = pd.api.types.is_numeric_dtype(df["original_color"])
+        fill_encoding = (
+            alt.Fill("original_color:Q")
+            if color_is_numeric
+            else alt.Fill("viz_fill_color:N", scale=None, title="Color")
+        )
 
         # Determine space dimensions
         xmin, xmax, ymin, ymax = self.space_drawer.get_viz_limits()
+        unique_shape_names_in_data = df["shape"].dropna().unique().tolist()
 
         chart = (
             alt.Chart(df)

mesa/visualization/backends/matplotlib_backend.py

@@ -27,7 +27,6 @@
 OrthogonalGrid = SingleGrid | MultiGrid | OrthogonalMooreGrid | OrthogonalVonNeumannGrid
 HexGrid = HexSingleGrid | HexMultiGrid | mesa.discrete_space.HexGrid
 
-
 CORRECTION_FACTOR_MARKER_ZOOM = 0.01
 
 
@@ -141,6 +140,10 @@ def collect_agent_data(self, space, agent_portrayal, default_size=None):
                     )
             else:
                 aps = portray_input
+                if aps.tooltip is not None:
+                    raise ValueError(
+                        "The 'tooltip' attribute in AgentPortrayalStyle is only supported by the Altair backend."
+                    )
                 # Set defaults if not provided
                 if aps.x is None and aps.y is None:
                     aps.x, aps.y = self._get_agent_pos(agent, space)

mesa/visualization/components/portrayal_components.py

@@ -55,6 +55,8 @@ class AgentPortrayalStyle:
     alpha: float | None = 1.0
     edgecolors: str | tuple | None = None
     linewidths: float | int | None = 1.0
+    tooltip: dict | None = None
+    """A dictionary of data to display on hover. Note: This feature is only available with the Altair backend."""
 
     def update(self, *updates_fields: tuple[str, Any]):
         """Updates attributes from variable (field_name, new_value) tuple arguments.

tests/test_backends.py

@@ -248,6 +248,7 @@ def test_altair_backend_draw_agents():
         "color": np.array(["red", "blue"]),
         "filled": np.array([True, True]),
         "stroke": np.array(["black", "black"]),
+        "tooltip": np.array([None, None]),
     }
     ab.space_drawer.get_viz_limits = MagicMock(return_value=(0, 10, 0, 10))
     assert ab.draw_agents(arguments) is not None