From 0e7a945f3bb155e6b9843f15a3c08acdf45a5b5d Mon Sep 17 00:00:00 2001
From: Jim O'Donnell <james.odonnell@dtc.ox.ac.uk>
Date: Fri, 6 Dec 2024 13:00:09 +0000
Subject: [PATCH] revert changes to SingleImageViewer

---
 .../components/SingleImageViewer/SingleImageViewer.js        | 5 ++++-
 .../plugins/drawingTools/components/draggable/draggable.js   | 5 +++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/packages/lib-classifier/src/components/Classifier/components/SubjectViewer/components/SingleImageViewer/SingleImageViewer.js b/packages/lib-classifier/src/components/Classifier/components/SubjectViewer/components/SingleImageViewer/SingleImageViewer.js
index b8d2547abef..6829d078a2c 100644
--- a/packages/lib-classifier/src/components/Classifier/components/SubjectViewer/components/SingleImageViewer/SingleImageViewer.js
+++ b/packages/lib-classifier/src/components/Classifier/components/SubjectViewer/components/SingleImageViewer/SingleImageViewer.js
@@ -34,10 +34,12 @@ function SingleImageViewer({
   zoomControlFn = null,
   zooming = false
 }) {
+  const canvasLayer = useRef()
+  const canvas = canvasLayer.current
   const transform = `rotate(${rotate} ${width / 2} ${height / 2})`
 
   return (
-    <SVGContext.Provider value={{ viewBox, rotate, width, height }}>
+    <SVGContext.Provider value={{ canvas, viewBox, rotate, width, height }}>
       {zoomControlFn && (
         <ZoomControlButton
           onClick={zoomControlFn}
@@ -66,6 +68,7 @@ function SingleImageViewer({
             transform={transform}
           >
             <SVGImageCanvas
+              ref={canvasLayer}
               viewBox={viewBox}
             >
               {children}
diff --git a/packages/lib-classifier/src/plugins/drawingTools/components/draggable/draggable.js b/packages/lib-classifier/src/plugins/drawingTools/components/draggable/draggable.js
index 35e142e7c60..ee56d721af4 100644
--- a/packages/lib-classifier/src/plugins/drawingTools/components/draggable/draggable.js
+++ b/packages/lib-classifier/src/plugins/drawingTools/components/draggable/draggable.js
@@ -16,8 +16,9 @@ function createPoint(event) {
 
 function getEventOffset(event, canvas) {
   const svgPoint = createPoint(event)
-  const svgEventOffset = svgPoint.matrixTransform
-    ? svgPoint.matrixTransform(canvas.getScreenCTM().inverse())
+  const ctm = canvas?.getScreenCTM()
+  const svgEventOffset = ctm && svgPoint.matrixTransform
+    ? svgPoint.matrixTransform(ctm.inverse())
     : svgPoint
   return svgEventOffset
 }