feat(events): 1-D / PlotXY double_click reports ydata (data coords)

The 1-D dblclick handler already computed xdata; add ydata by inverting the
linear y transform. draw1d caches the rendered y bounds (p._1dDMin/_1dDMax) so
the inverse uses exactly what was drawn — for a PlotXY coordinate axis the y
range is y_range, not the hidden zero-curve's data_min/max. Matches the 2-D
image path so a coordinate axis can be picked in data space.

Test: test_double_click_reports_data_coords (centre click → centre of x/y range).

Author: CSSFrancis

anyplotlib/figure_esm.js

@@ -3261,6 +3261,10 @@ fn fs(in : VsOut) -> @location(0) vec4<f32> {
     const x0=st.view_x0||0, x1=st.view_x1||1;
     let dMin=st.data_min, dMax=st.data_max;
     if (st.y_range && st.y_range.length === 2) { dMin = st.y_range[0]; dMax = st.y_range[1]; }
+    // Cache the linear y bounds so the dblclick handler inverts event y → data y
+    // using exactly what was drawn (for a PlotXY coordinate axis the y range is
+    // y_range, not the hidden zero-curve's data_min/max).
+    p._1dDMin=dMin; p._1dDMax=dMax;
     const units=st.units||'', yUnits=st.y_units||'';
 
     const isLog = st.yscale === 'log';
@@ -4588,14 +4592,20 @@ fn fs(in : VsOut) -> @location(0) vec4<f32> {
     overlayCanvas.addEventListener('dblclick',(e)=>{
       const {mx,my}=_clientPos(e,overlayCanvas,p.pw,p.ph);
       const st=p.state;
-      let xdata=null;
+      let xdata=null, ydata=null;
       if(st){
         const r=_plotRect1d(p);
         const xArr=p._1dXArr||(st.x_axis_b64?_decodeF64(st.x_axis_b64):(st.x_axis||[]));
         const frac=_canvasXToFrac1d(mx,st.view_x0,st.view_x1,r);
         xdata=xArr.length>=2?_axisFracToVal(xArr,frac):frac;
-      }
-      _emitEvent(p.id,'double_click',null,{..._pointerFields(e),button:e.button,x:mx,y:my,xdata});
+        // ydata: invert the linear y transform. Prefer the bounds draw1d cached
+        // (exactly what was rendered) — for a coordinate axis (PlotXY) data_min
+        // may be the zero-curve's range, so y_range / the cache is authoritative.
+        let dMin=(p._1dDMin!=null?p._1dDMin:st.data_min), dMax=(p._1dDMax!=null?p._1dDMax:st.data_max);
+        if(dMin==null && st.y_range && st.y_range.length===2){ dMin=st.y_range[0]; dMax=st.y_range[1]; }
+        if(dMin!=null && dMax!=null) ydata=dMin+((r.y+r.h-my)/(r.h||1))*(dMax-dMin);
+      }
+      _emitEvent(p.id,'double_click',null,{..._pointerFields(e),button:e.button,x:mx,y:my,xdata,ydata});
     });
     overlayCanvas.addEventListener('wheel',(e)=>{
       _emitEvent(p.id,'wheel',null,{

anyplotlib/tests/test_plotxy/test_plotxy.py

@@ -58,6 +58,30 @@ def test_scatter_returns_collection_with_offsets():
     assert pts["n"] == 3
 
 
+def test_double_click_reports_data_coords(interact_page):
+    """A ``double_click`` on a coordinate (PlotXY) panel reports ``xdata``/``ydata``
+    in DATA coords (like the 2-D image path) — needed for a data-coord pick such
+    as the IPF-refine mask. Clicking panel-centre ⇒ centre of the x/y range."""
+    from anyplotlib.tests.test_interactive._event_test_utils import (
+        _collect_events, _get_events, _plot_center_page,
+    )
+    fig, ax = apl.subplots(1, 1, figsize=(400, 300))
+    ax.axes2d(xlim=(0, 10), ylim=(0, 20), aspect="equal")
+    page = interact_page(fig)
+    _collect_events(page)
+
+    px, py = _plot_center_page(400, 300)
+    page.mouse.dblclick(px, py)
+    page.wait_for_timeout(100)
+
+    evs = _get_events(page, "double_click")
+    assert evs, "expected a double_click event"
+    e = evs[-1]
+    assert e.get("xdata") is not None and e.get("ydata") is not None
+    assert abs(e["xdata"] - 5.0) < 1.5         # centre of x range (0, 10)
+    assert abs(e["ydata"] - 10.0) < 3.0        # centre of y range (0, 20)
+
+
 def test_render_is_chromatic(take_screenshot):
     """End-to-end: a filled triangle + coloured scatter + labels in data coords
     must actually draw (canvas is chromatic, not blank)."""

upcoming_changes/+dblclick_1d_datacoords.new_feature.rst

@@ -0,0 +1,3 @@
+The ``double_click`` event on a 1-D / :class:`PlotXY` panel now reports
+``ydata`` alongside ``xdata`` (data coordinates), matching the 2-D image path —
+so a coordinate axis can be picked in data space (e.g. an IPF / pole-figure mask).