From 4f438205f3c5b972092d47aaaafafdcaafbd50d5 Mon Sep 17 00:00:00 2001
From: Robert Collar <robert.collar@koboldmetals.com>
Date: Tue, 5 May 2026 21:36:22 -0400
Subject: [PATCH] dragbox: sync ax._input.range when mutating ax.range during
 pan and scroll-zoom
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

scaleZoom() consistently writes both `ax.range` and `ax._input.range`
(scale_zoom.js:13), but several mutation sites in dragbox.js only wrote
`ax.range`:

  * zoomWheelOneAxis  (mousewheel zoom)
  * dz                (corner-handle zoom on drag)
  * updateMatchedAxRange  (linked-axis update during drag)
  * dragAxList        (pan)

`ax._input.range` is what `gd.layout.<axis>.range` references. Leaving it
stale means user code reading `gd.layout` from a `plotly_relayouting`
handler sees the *previous* range while `gd._fullLayout` already reflects
the in-progress gesture. Any work that handler does (recomputing
positions, fetching new tiles, updating annotations) is therefore
computed against an out-of-date viewport, and only "catches up" once
dragTail eventually runs a full relayout.

This is reproducible by attaching a relayouting handler that compares
gd.layout.xaxis.range to gd._fullLayout.xaxis.range during a wheel zoom
- before the fix the two diverge; after the fix they stay in sync.

The change is the minimal extension of the existing `ax.range = …`
assignments to also set `ax._input.range`, matching the pattern already
used by scaleZoom and Plotly.relayout.
---
 src/plots/cartesian/dragbox.js | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/plots/cartesian/dragbox.js b/src/plots/cartesian/dragbox.js
index 0aa0caceee2..123edb2efce 100644
--- a/src/plots/cartesian/dragbox.js
+++ b/src/plots/cartesian/dragbox.js
@@ -499,7 +499,7 @@ function makeDragBox(gd, plotinfo, x, y, w, h, ns, ew) {
             var axRange = Lib.simpleMap(ax.range, ax.r2l);
             var v0 = axRange[0] + (axRange[1] - axRange[0]) * centerFraction;
             function doZoom(v) { return ax.l2r(v0 + (v - v0) * zoom); }
-            ax.range = axRange.map(doZoom);
+            ax.range = ax._input.range = axRange.map(doZoom);
         }
 
         if(editX) {
@@ -613,7 +613,12 @@ function makeDragBox(gd, plotinfo, x, y, w, h, ns, ew) {
 
                 // if l2r comes back false or undefined, it means we've dragged off
                 // the end of valid ranges - so stop.
-                if(newEnd !== false && newEnd !== undefined) axi.range[end] = newEnd;
+                if(newEnd !== false && newEnd !== undefined) {
+                    axi.range[end] = newEnd;
+                    // keep ax._input.range (the user-facing layout) in sync so
+                    // plotly_relayouting handlers reading gd.layout see fresh values
+                    axi._input.range = axi.range.slice();
+                }
             }
             return movedAx._length * (movedAx._rl[end] - newLinearizedEnd) /
                 (movedAx._rl[end] - movedAx._rl[otherEnd]);
@@ -710,7 +715,7 @@ function makeDragBox(gd, plotinfo, x, y, w, h, ns, ew) {
                     out[ax._name + '.range[0]'] = out[ax2._name + '.range[0]'];
                     out[ax._name + '.range[1]'] = out[ax2._name + '.range[1]'];
                 } else {
-                    ax.range = ax2.range.slice();
+                    ax.range = ax._input.range = ax2.range.slice();
                 }
             }
         }
@@ -1120,12 +1125,12 @@ function dragAxList(axList, pix) {
                 var d1 = axi.p2l(p1 + pix) - axi.p2l(p1);
                 var delta = (d0 + d1) / 2;
 
-                axi.range = [
+                axi.range = axi._input.range = [
                     axi.l2r(axi._rl[0] - delta),
                     axi.l2r(axi._rl[1] - delta)
                 ];
             } else {
-                axi.range = [
+                axi.range = axi._input.range = [
                     axi.l2r(axi._rl[0] - pix / axi._m),
                     axi.l2r(axi._rl[1] - pix / axi._m)
                 ];