Improved the triggering ease of edge tooltips by making invisible hov…

…erable points larger for both edges and arrows (the latter are smaller than the former to avoid overcrowding around nodes).

The documentation now also explains how to override their properties (as well as how to have different tooltips for arrows and edges).

src/altair_nx/draw_altair.py

@@ -33,7 +33,11 @@ def draw_networkx_edges(G: nx.Graph = None, pos: dict[..., tuple[float, float]]
     :param cmap: Colourmap for mapping intensities of edges (requires colour to be an edge attribute containing floats).
     :param alpha: Edge opacity.
 
-    :param tooltip: Edge attributes to show on hover.
+    :param tooltip: Edge attributes to show on hover. By default, the tooltip is only* triggered on an invisible point at the edge midpoint (or slightly off of it if the edge is curved);
+        providing any control_points overrides this default.
+        To set these hoverable points' properties, pass them under the key 'point' through edge_mark_kwargs;
+        the default is equivalent to `mark_kwargs = dict(point = alt.OverlayMarkDef(opacity = 0, size = 400))`.
+        (*: the tooltip is also shown at the base of arrows (with invisible point size of 100, overridable as above) if G is directed and arrow tooltips are not overridden through arrow_encode_kwargs).
     :param legend: Whether to show a legend for attribute-controlled edge features.
     
     :param loop_radius: The radius of self-loop edges.
@@ -132,7 +136,7 @@ def draw_networkx_edges(G: nx.Graph = None, pos: dict[..., tuple[float, float]]
 
     # ---------- Finalise the fields and construct the visualisation ------------
 
-    marker_attrs['point'] = 'transparent' # to make triggering tooltips easier
+    marker_attrs['point'] = alt.OverlayMarkDef(opacity = 0, size = 400) # to make triggering tooltips easier
     encoded_attrs = dict(x = alt.X('x').axis(None), y = alt.Y('y').axis(None), detail = 'edge', order = 'order', **encoded_attrs)
 
     # Inject custom fields without restrictions or safeguards
@@ -177,7 +181,9 @@ def draw_networkx_arrows(G: nx.Graph = None, pos: dict[..., tuple[float, float]]
     :param cmap: Colourmap for mapping intensities of arrows (requires colour to be an edge attribute containing floats).
     :param alpha: Edge opacity.
 
-    :param tooltip: Edge attributes to show on hover for arrows.
+    :param tooltip: Edge attributes to show on hover for arrows. (NOTE that draw_networkx passes edge_tooltip to this argument; to set different tooltip attributes from edges, pass them under the key 'tooltip' through arrow_encode_kwargs). The tooltip is only triggered on an invisible point at the base of the arrow;
+        to set this hoverable point's properties, pass them under the key 'point' through mark_kwargs;
+        the default is equivalent to `mark_kwargs = dict(point = alt.OverlayMarkDef(opacity = 0, size = 100))`.
     :param legend: Whether to show a legend for attribute-controlled arrow features.
 
     :param curved_edges: Whether the edges for which arrows are to be drawn are curved.
@@ -247,7 +253,7 @@ def draw_networkx_arrows(G: nx.Graph = None, pos: dict[..., tuple[float, float]]
 
     # ---------- Finalise the fields and construct the visualisation ------------
 
-    marker_attrs['point'] = 'transparent' # to make triggering tooltips easier
+    marker_attrs['point'] = alt.OverlayMarkDef(opacity = 0, size = 100) # to make triggering tooltips easier; smaller than edges' hover points to avoid overcrowding near nodes
     encoded_attrs = dict(x = alt.X('x').axis(None), y = alt.Y('y').axis(None), detail = 'edge', **encoded_attrs)
 
     # Inject custom fields without restrictions or safeguards
@@ -557,7 +563,11 @@ def draw_networkx(G: nx.Graph = None, pos: dict[..., tuple[float, float]] = None
     :param edge_cmap: Colourmap for mapping intensities of edges (requires edge_colour to be an edge attribute containing floats).
     :param edge_alpha: Edge opacity.
 
-    :param edge_tooltip: Edge attributes to show on hover.
+    :param edge_tooltip: Edge attributes to show on hover (applies to arrows as well). By default, the tooltip is only* triggered on an invisible point at the edge midpoint (or slightly off of it if the edge is curved);
+        providing any edge_control_points overrides this default.
+        To set these hoverable points' properties, pass them under the key 'point' through edge_mark_kwargs;
+        the default is equivalent to `edge_mark_kwargs = dict(point = alt.OverlayMarkDef(opacity = 0, size = 400))`.
+        (*: the tooltip is also shown at the base of arrows (with invisible point size of 100, overridable as above) if G is directed and arrow tooltips are not overridden through arrow_encode_kwargs).
     :param edge_legend: Whether to show a legend for attribute-controlled edge features.
 
     :param loop_radius: The radius of self-loop edges.