From c8e3241bc48e190fccd715d5bda5bd158e08f2c5 Mon Sep 17 00:00:00 2001
From: Jim O'Donnell <james.odonnell@dtc.ox.ac.uk>
Date: Mon, 6 Jan 2025 17:06:34 +0000
Subject: [PATCH] fix(lib-classifier): canvas context for SVG drawing tools
 (#6491)

* fix(lib-classifier): canvas context for SVG drawing tools

Make sure that `SVGContext.canvas` is a reference to the SVG `rect` element that's used as a drawing canvas, so that creating new drawing marks and editing existing marks both use the same screen CTM when calculating the pointer position.

This fixes a bug in Firefox where the `draggable` decorator doesn't correctly track the active pointer, in the context of a zoomed SVG image.

* DRY up SVG event-handling functions

* revert changes to SingleImageViewer
---
 .../InteractionLayer/InteractionLayer.js      | 55 ++++---------------
 .../components/draggable/draggable.js         |  7 ++-
 2 files changed, 16 insertions(+), 46 deletions(-)

diff --git a/packages/lib-classifier/src/components/Classifier/components/SubjectViewer/components/InteractionLayer/InteractionLayer.js b/packages/lib-classifier/src/components/Classifier/components/SubjectViewer/components/InteractionLayer/InteractionLayer.js
index 1ec9ee978b..0fbc578b18 100644
--- a/packages/lib-classifier/src/components/Classifier/components/SubjectViewer/components/InteractionLayer/InteractionLayer.js
+++ b/packages/lib-classifier/src/components/Classifier/components/SubjectViewer/components/InteractionLayer/InteractionLayer.js
@@ -1,7 +1,10 @@
 import cuid from 'cuid'
 import PropTypes from 'prop-types'
-import { useRef, useState } from 'react';
+import { useContext, useRef, useState } from 'react';
 import styled, { css } from 'styled-components'
+
+import SVGContext from '@plugins/drawingTools/shared/SVGContext'
+import { convertEvent } from '@plugins/drawingTools/components/draggable/draggable'
 import DrawingToolMarks from './components/DrawingToolMarks'
 import TranscribedLines from './components/TranscribedLines'
 import SubTaskPopup from './components/SubTaskPopup'
@@ -43,7 +46,9 @@ function InteractionLayer({
   duration
 }) {
   const [creating, setCreating] = useState(false)
-  const canvas = useRef()
+  const svgContext = useContext(SVGContext)
+  const canvasRef = useRef()
+  svgContext.canvas = canvasRef.current
 
   if (creating && !activeMark) {
     setCreating(false)
@@ -54,42 +59,6 @@ function InteractionLayer({
     setActiveMark(undefined)
   }
 
-  function convertEvent(event) {
-    const type = event.type
-
-    const svgEventOffset = getEventOffset(event)
-
-    const svgCoordinateEvent = {
-      pointerId: event.pointerId,
-      type,
-      x: svgEventOffset.x,
-      y: svgEventOffset.y
-    }
-
-    return svgCoordinateEvent
-  }
-
-  function createPoint(event) {
-    const { clientX, clientY } = event
-    // SVG 2 uses DOMPoint
-    if (window.DOMPointReadOnly) {
-      return new DOMPointReadOnly(clientX, clientY)
-    }
-    // jsdom doesn't support SVG
-    return {
-      x: clientX,
-      y: clientY
-    }
-  }
-
-  function getEventOffset(event) {
-    const svgPoint = createPoint(event)
-    const svgEventOffset = svgPoint.matrixTransform
-      ? svgPoint.matrixTransform(canvas.current?.getScreenCTM().inverse())
-      : svgPoint
-    return svgEventOffset
-  }
-
   function createMark(event) {
     const timeStamp = getFixedNumber(played, 5)
     const mark = activeTool.createMark({
@@ -99,7 +68,7 @@ function InteractionLayer({
       toolIndex: activeToolIndex
     })
 
-    mark.initialPosition(convertEvent(event))
+    mark.initialPosition(convertEvent(event, canvasRef.current))
     setActiveMark(mark)
     setCreating(true)
     mark.setSubTaskVisibility(false)
@@ -124,7 +93,7 @@ function InteractionLayer({
     }
 
     if (creating) {
-      activeTool?.handlePointerDown?.(convertEvent(event), activeMark)
+      activeTool?.handlePointerDown?.(convertEvent(event, canvasRef.current), activeMark)
       if (activeMark.finished) onFinish(event)
       return true
     }
@@ -136,7 +105,7 @@ function InteractionLayer({
   function onPointerMove(event) {
     cancelEvent(event)
     if (creating) {
-      activeTool?.handlePointerMove?.(convertEvent(event), activeMark)
+      activeTool?.handlePointerMove?.(convertEvent(event, canvasRef.current), activeMark)
     }
   }
 
@@ -149,7 +118,7 @@ function InteractionLayer({
   function onPointerUp(event) {
     cancelEvent(event)
     if (creating) {
-      activeTool?.handlePointerUp?.(convertEvent(event), activeMark)
+      activeTool?.handlePointerUp?.(convertEvent(event, canvasRef.current), activeMark)
       if (activeMark.finished) onFinish(event)
     }
   }
@@ -165,7 +134,7 @@ function InteractionLayer({
   return (
     <>
       <DrawingCanvas
-        ref={canvas}
+        ref={canvasRef}
         disabled={disabled || move}
         pointerEvents={move ? 'none' : 'all'}
         width={width}
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 b4b1fda3f4..ee56d721af 100644
--- a/packages/lib-classifier/src/plugins/drawingTools/components/draggable/draggable.js
+++ b/packages/lib-classifier/src/plugins/drawingTools/components/draggable/draggable.js
@@ -16,13 +16,14 @@ 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
 }
 
-function convertEvent(event, canvas) {
+export function convertEvent(event, canvas) {
   const svgEventOffset = getEventOffset(event, canvas)
   const svgCoordinateEvent = {
     type: event.type,