support trashing of annotations

- if annotation trashing is supported, do not override
key of annotations when deletion is undone
- expose annotationManager.clearInterferingHistory
so that when an annotation is erased from trash, it
is removed from reader's edits history

Author: abaevbog

src/common/annotation-manager.js

@@ -23,6 +23,7 @@ class AnnotationManager {
 		this._onSave = options.onSave;
 		this._onDelete = options.onDelete;
 		this._onChangeHistory = options.onChangeHistory;
+		this._trashesAnnotations = options.trashesAnnotations;
 		this._adjustTextAnnotationPosition = options.adjustTextAnnotationPosition;
 		this.render = () => {
 			options.onRender([...this._annotations]);
@@ -601,8 +602,10 @@ class AnnotationManager {
 			if (annotation) {
 				annotation.dateModified = (new Date()).toISOString();
 			}
-			// Assign new id when undeleting to reduce sync conflicts
-			if (!prevAnnotation) {
+			// Assign new id when undeleting to reduce sync conflicts. Clients that
+			// trash annotations keep the deleted one around, so undeleting restores
+			// it in place and the id has to stay the same for the client to find it.
+			if (!prevAnnotation && !this._trashesAnnotations) {
 				let newID = this._generateObjectKey();
 				mapping.set(annotation.id, newID);
 				annotation.id = newID;
@@ -635,8 +638,10 @@ class AnnotationManager {
 			if (annotation) {
 				annotation.dateModified = (new Date()).toISOString();
 			}
-			// Assign new id when undeleting to reduce sync conflicts
-			if (!prevAnnotation) {
+			// Assign new id when undeleting to reduce sync conflicts. Clients that
+			// trash annotations keep the deleted one around, so undeleting restores
+			// it in place and the id has to stay the same for the client to find it.
+			if (!prevAnnotation && !this._trashesAnnotations) {
 				let newID = this._generateObjectKey();
 				mapping.set(annotation.id, newID);
 				annotation.id = newID;
@@ -654,6 +659,12 @@ class AnnotationManager {
 		return true;
 	}
 
+	// Drops history points for annotations that have left the reader so
+	// that erased annotations cannot be brought back.
+	clearHistoryForAnnotations(ids) {
+		this._clearInterferingHistory(ids);
+	}
+
 	_clearInterferingHistory(affectedAnnotationIDs) {
 		for (let i = this._undoStack.length - 1; i >= 0; i--) {
 			if (affectedAnnotationIDs.some(id => this._undoStack[i].annotations.has(id))) {

src/common/reader.js

@@ -130,6 +130,7 @@ class Reader {
 		this._onSetPopupPosition = options.onSetPopupPosition;
 		this._onChangeUndoHistory = options.onChangeUndoHistory;
 		this._externalUndoHistory = !!options.onChangeUndoHistory;
+		this._trashesAnnotations = !!options.trashesAnnotations;
 
 		for (let ftl of options.ftl) {
 			addFTL(ftl);
@@ -361,6 +362,7 @@ class Reader {
 				this._updateState({ filter });
 			},
 			onChangeHistory: this._onChangeUndoHistory,
+			trashesAnnotations: this._trashesAnnotations,
 			adjustTextAnnotationPosition: (annotation, option) => {
 				return this._primaryView.adjustTextAnnotationPosition(annotation, option);
 			}
@@ -951,6 +953,13 @@ class Reader {
 		this._annotationManager.unsetAnnotations(ids);
 	}
 
+	// Called when the client permanently deletes annotations that are no longer
+	// in the view (e.g. erased from the trash), so history points referencing
+	// them can't be replayed and recreate them
+	clearAnnotationsHistory(ids) {
+		this._annotationManager.clearHistoryForAnnotations(ids);
+	}
+
 	openContextMenu(params) {
 		this._onBringReaderToFront?.(true);
 		this._updateState({ contextMenu: params });