Merge pull request #896 from ckeditor/t/887

Fix: Renderer should not change the native selection if the one it's about to render is visually similar to the current one. Closes #887. Closes #880.

src/view/renderer.js

@@ -9,12 +9,14 @@
 
 import ViewText from './text';
 import ViewPosition from './position';
+import Selection from './selection';
 import { INLINE_FILLER, INLINE_FILLER_LENGTH, startsWithFiller, isInlineFiller, isBlockFiller } from './filler';
 
 import mix from '@ckeditor/ckeditor5-utils/src/mix';
 import diff from '@ckeditor/ckeditor5-utils/src/diff';
 import insertAt from '@ckeditor/ckeditor5-utils/src/dom/insertat';
 import remove from '@ckeditor/ckeditor5-utils/src/dom/remove';
+import log from '@ckeditor/ckeditor5-utils/src/log';
 import ObservableMixin from '@ckeditor/ckeditor5-utils/src/observablemixin';
 import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
 
@@ -580,6 +582,17 @@ export default class Renderer {
 			return;
 		}
 
+		if ( oldViewSelection && areSimilarSelections( oldViewSelection, this.selection ) ) {
+			const data = {
+				oldSelection: oldViewSelection,
+				currentSelection: this.selection
+			};
+
+			log.warn( 'renderer-skipped-selection-rendering: The selection was not rendered due to its similarity to the current one.', data );
+
+			return;
+		}
+
 		// Multi-range selection is not available in most browsers, and, at least in Chrome, trying to
 		// set such selection, that is not continuous, throws an error. Because of that, we will just use anchor
 		// and focus of view selection.
@@ -642,3 +655,35 @@ export default class Renderer {
 }
 
 mix( Renderer, ObservableMixin );
+
+// Checks if two given selections are similar. Selections are considered similar if they are non-collapsed
+// and their trimmed (see {@link #_trimSelection}) representations are equal.
+//
+// @private
+// @param {module:engine/view/selection~Selection} selection1
+// @param {module:engine/view/selection~Selection} selection2
+// @returns {Boolean}
+function areSimilarSelections( selection1, selection2 ) {
+	return !selection1.isCollapsed && trimSelection( selection1 ).isEqual( trimSelection( selection2 ) );
+}
+
+// Creates a copy of a given selection with all of its ranges
+// trimmed (see {@link module:engine/view/range~Range#getTrimmed getTrimmed}).
+//
+// @private
+// @param {module:engine/view/selection~Selection} selection
+// @returns {module:engine/view/selection~Selection} Selection copy with all ranges trimmed.
+function trimSelection( selection ) {
+	const newSelection = Selection.createFromSelection( selection );
+	const ranges = newSelection.getRanges();
+
+	let trimmedRanges = [];
+
+	for ( let range of ranges ) {
+		trimmedRanges.push( range.getTrimmed() );
+	}
+
+	newSelection.setRanges( trimmedRanges, newSelection.isBackward );
+
+	return newSelection;
+}

tests/manual/tickets/880/1.html

@@ -0,0 +1,3 @@
+<div id="editor">
+	<p>This is an <strong>editor</strong> instance.</p>
+</div>

tests/manual/tickets/880/1.js

@@ -0,0 +1,27 @@
+/**
+ * @license Copyright (c) 2003-2017, CKSource - Frederico Knabben. All rights reserved.
+ * For licensing, see LICENSE.md.
+ */
+
+/* globals console, window, document */
+
+import ClassicEditor from '@ckeditor/ckeditor5-editor-classic/src/classic';
+import EssentialsPreset from '@ckeditor/ckeditor5-presets/src/essentials';
+import Paragraph from '@ckeditor/ckeditor5-paragraph/src/paragraph';
+import Bold from '@ckeditor/ckeditor5-basic-styles/src/bold';
+
+ClassicEditor.create( document.querySelector( '#editor' ), {
+	plugins: [ EssentialsPreset, Paragraph, Bold ],
+	toolbar: [ 'undo', 'redo' ]
+} )
+.then( editor => {
+	window.editor = editor;
+
+	editor.editing.view.on( 'selectionChange', () => {
+		editor.document.enqueueChanges( () => {} );
+		console.log( 'selectionChange', ( new Date() ).getTime() );
+	} );
+} )
+.catch( err => {
+	console.error( err.stack );
+} );

tests/manual/tickets/880/1.md

@@ -0,0 +1,14 @@
+## Renderer - infinite `selectionChange` event
+
+Place the selection like this:
+
+```
+This is {an <strong>editor}</strong> instance.
+```
+
+(it must end at the end of the inline style)
+
+**Expected**:
+
+* Every time selection is changed, console log with `selectionChange` is printed once.
+* While creating selection from **2.**, there might be `renderer-selection-similar` warning visible in the console.

tests/manual/tickets/887/1.html

@@ -0,0 +1,3 @@
+<div id="editor">
+	<p>This is an <strong>editor</strong> instance.</p>
+</div>

tests/manual/tickets/887/1.js

@@ -0,0 +1,22 @@
+/**
+ * @license Copyright (c) 2003-2017, CKSource - Frederico Knabben. All rights reserved.
+ * For licensing, see LICENSE.md.
+ */
+
+/* globals console, window, document */
+
+import ClassicEditor from '@ckeditor/ckeditor5-editor-classic/src/classic';
+import EssentialsPreset from '@ckeditor/ckeditor5-presets/src/essentials';
+import Paragraph from '@ckeditor/ckeditor5-paragraph/src/paragraph';
+import Bold from '@ckeditor/ckeditor5-basic-styles/src/bold';
+
+ClassicEditor.create( document.querySelector( '#editor' ), {
+	plugins: [ EssentialsPreset, Paragraph, Bold ],
+	toolbar: [ 'undo', 'redo' ]
+} )
+.then( editor => {
+	window.editor = editor;
+} )
+.catch( err => {
+	console.error( err.stack );
+} );

tests/manual/tickets/887/1.md

@@ -0,0 +1,10 @@
+## Renderer - MacOS accent balloon on inline element boundary
+
+1. Place the selection like this:
+
+   `This is an <strong>editor{}</strong> instance.`
+2. Open MacOS accent balloon (e.g. long `a` press).
+3. Navigate through the balloon panel using arrow keys.
+
+**Expected**: It is possible to navigate with arrow keys inside the MacOS balloon panel. While navigating, there
+might be `renderer-selection-similar` warning visible in the console.