From 0a5bd279786d31dada8bc33d74e2a69c42fb1515 Mon Sep 17 00:00:00 2001
From: Marijn Haverbeke <marijn@haverbeke.berlin>
Date: Sat, 24 Aug 2024 10:37:55 +0200
Subject: [PATCH] Add support for clipboardInputFilter/clipboardOutputFilter

FEATURE: The new `EditorView.clipboardInputFilter` and `clipboardOutputFilter` facets
allow you to register filter functions that change text taken from or sent to the clipboard.
---
 src/editorview.ts | 10 +++++++++-
 src/extension.ts  |  3 +++
 src/input.ts      | 17 +++++++++++++----
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/editorview.ts b/src/editorview.ts
index f6b81f4..39f8ecb 100644
--- a/src/editorview.ts
+++ b/src/editorview.ts
@@ -16,7 +16,8 @@ import {ViewUpdate, styleModule,
         exceptionSink, updateListener, logException,
         viewPlugin, ViewPlugin, PluginValue, PluginInstance, decorations, outerDecorations, atomicRanges,
         scrollMargins, MeasureRequest, editable, inputHandler, focusChangeEffect, perLineTextDirection,
-        scrollIntoView, UpdateFlag, ScrollTarget, bidiIsolatedRanges, getIsolatedRanges, scrollHandler} from "./extension"
+        scrollIntoView, UpdateFlag, ScrollTarget, bidiIsolatedRanges, getIsolatedRanges, scrollHandler,
+        clipboardInputFilter, clipboardOutputFilter} from "./extension"
 import {theme, darkTheme, buildTheme, baseThemeID, baseLightID, baseDarkID, lightDarkIDs, baseTheme} from "./theme"
 import {DOMObserver} from "./domobserver"
 import {Attrs, updateAttrs, combineAttrs} from "./attributes"
@@ -966,6 +967,13 @@ export class EditorView {
   /// dispatching the custom behavior as a separate transaction.
   static inputHandler = inputHandler
 
+  /// Functions provided in this facet will be used to transform text
+  /// pasted or dropped into the editor.
+  static clipboardInputFilter = clipboardInputFilter
+
+  /// Transform text copied or dragged from the editor.
+  static clipboardOutputFilter = clipboardOutputFilter
+
   /// Scroll handlers can override how things are scrolled into view.
   /// If they return `true`, no further handling happens for the
   /// scrolling. If they return false, the default scroll behavior is
diff --git a/src/extension.ts b/src/extension.ts
index bad23a7..275ecf5 100644
--- a/src/extension.ts
+++ b/src/extension.ts
@@ -30,6 +30,9 @@ export const inputHandler = Facet.define<(view: EditorView, from: number, to: nu
 
 export const focusChangeEffect = Facet.define<(state: EditorState, focusing: boolean) => StateEffect<any> | null>()
 
+export const clipboardInputFilter = Facet.define<(text: string, state: EditorState) => string>()
+export const clipboardOutputFilter = Facet.define<(text: string, state: EditorState) => string>()
+
 export const perLineTextDirection = Facet.define<boolean, boolean>({
   combine: values => values.some(x => x)
 })
diff --git a/src/input.ts b/src/input.ts
index 6a0baba..d1b985f 100644
--- a/src/input.ts
+++ b/src/input.ts
@@ -1,9 +1,10 @@
-import {EditorSelection, EditorState, SelectionRange, RangeSet, Annotation, Text} from "@codemirror/state"
+import {EditorSelection, EditorState, SelectionRange, RangeSet, Annotation, Text, Facet} from "@codemirror/state"
 import {EditorView} from "./editorview"
 import {ContentView} from "./contentview"
 import {LineView} from "./blockview"
 import {ViewUpdate, PluginValue, clickAddsSelectionRange, dragMovesSelection as dragBehavior, atomicRanges,
-        logException, mouseSelectionStyle, PluginInstance, focusChangeEffect, getScrollMargins} from "./extension"
+        logException, mouseSelectionStyle, PluginInstance, focusChangeEffect, getScrollMargins,
+        clipboardInputFilter, clipboardOutputFilter} from "./extension"
 import browser from "./browser"
 import {groupAt, skipAtomicRanges} from "./cursor"
 import {getSelection, focusPreventScroll, Rect, dispatchKey, scrollableParents} from "./dom"
@@ -471,7 +472,13 @@ function capturePaste(view: EditorView) {
   }, 50)
 }
 
+function textFilter(state: EditorState, facet: Facet<(value: string, state: EditorState) => string>, text: string) {
+  for (let filter of state.facet(facet)) text = filter(text, state)
+  return text
+}
+
 function doPaste(view: EditorView, input: string) {
+  input = textFilter(view.state, clipboardInputFilter, input)
   let {state} = view, changes, i = 1, text = state.toText(input)
   let byLine = text.lines == state.selection.ranges.length
   let linewise = lastLinewiseCopy != null && state.selection.ranges.every(r => r.empty) && lastLinewiseCopy == text.toString()
@@ -653,7 +660,8 @@ handlers.dragstart = (view, event: DragEvent) => {
   inputState.draggedContent = range
 
   if (event.dataTransfer) {
-    event.dataTransfer.setData("Text", view.state.sliceDoc(range.from, range.to))
+    event.dataTransfer.setData("Text", textFilter(view.state, clipboardOutputFilter,
+                                                  view.state.sliceDoc(range.from, range.to)))
     event.dataTransfer.effectAllowed = "copyMove"
   }
   return false
@@ -665,6 +673,7 @@ handlers.dragend = view => {
 }
 
 function dropText(view: EditorView, event: DragEvent, text: string, direct: boolean) {
+  text = textFilter(view.state, clipboardInputFilter, text)
   if (!text) return
   let dropPos = view.posAtCoords({x: event.clientX, y: event.clientY}, false)
 
@@ -764,7 +773,7 @@ function copiedRange(state: EditorState) {
     linewise = true
   }
 
-  return {text: content.join(state.lineBreak), ranges, linewise}
+  return {text: textFilter(state, clipboardOutputFilter, content.join(state.lineBreak)), ranges, linewise}
 }
 
 let lastLinewiseCopy: string | null = null