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- /**
- * @license Copyright (c) 2003-2017, CKSource - Frederico Knabben. All rights reserved.
- * For licensing, see LICENSE.md.
- */
- /**
- * @module engine/controller/modifyselection
- */
- import Position from '../model/position';
- import TreeWalker from '../model/treewalker';
- import Range from '../model/range';
- import { isInsideSurrogatePair, isInsideCombinedSymbol } from '@ckeditor/ckeditor5-utils/src/unicode';
- /**
- * Modifies the selection. Currently, the supported modifications are:
- *
- * * Extending. The selection focus is moved in the specified `options.direction` with a step specified in `options.unit`.
- * Possible values for `unit` are:
- * * `'character'` (default) - moves selection by one user-perceived character. In most cases this means moving by one
- * character in `String` sense. However, unicode also defines "combing marks". These are special symbols, that combines
- * with a symbol before it ("base character") to create one user-perceived character. For example, `q̣̇` is a normal
- * letter `q` with two "combining marks": upper dot (`Ux0307`) and lower dot (`Ux0323`). For most actions, i.e. extending
- * selection by one position, it is correct to include both "base character" and all of it's "combining marks". That is
- * why `'character'` value is most natural and common method of modifying selection.
- * * `'codePoint'` - moves selection by one unicode code point. In contrary to, `'character'` unit, this will insert
- * selection between "base character" and "combining mark", because "combining marks" have their own unicode code points.
- * However, for technical reasons, unicode code points with values above `UxFFFF` are represented in native `String` by
- * two characters, called "surrogate pairs". Halves of "surrogate pairs" have a meaning only when placed next to each other.
- * For example `𨭎` is represented in `String` by `\uD862\uDF4E`. Both `\uD862` and `\uDF4E` do not have any meaning
- * outside the pair (are rendered as ? when alone). Position between them would be incorrect. In this case, selection
- * extension will include whole "surrogate pair".
- *
- * **Note:** if you extend a forward selection in a backward direction you will in fact shrink it.
- *
- * @param {module:engine/controller/datacontroller~DataController} dataController The data controller in context of which
- * the selection modification should be performed.
- * @param {module:engine/model/selection~Selection} selection The selection to modify.
- * @param {Object} [options]
- * @param {'forward'|'backward'} [options.direction='forward'] The direction in which the selection should be modified.
- * @param {'character'|'codePoint'} [options.unit='character'] The unit by which selection should be modified.
- */
- export default function modifySelection( dataController, selection, options = {} ) {
- const schema = dataController.model.schema;
- const isForward = options.direction != 'backward';
- const unit = options.unit ? options.unit : 'character';
- const focus = selection.focus;
- const walker = new TreeWalker( {
- boundaries: getSearchRange( focus, isForward ),
- singleCharacters: true,
- direction: isForward ? 'forward' : 'backward'
- } );
- const data = { walker, schema, isForward, unit };
- let next;
- while ( ( next = walker.next() ) ) {
- if ( next.done ) {
- return;
- }
- const position = tryExtendingTo( data, next.value );
- if ( position ) {
- selection.setFocus( position );
- return;
- }
- }
- }
- // Checks whether the selection can be extended to the the walker's next value (next position).
- function tryExtendingTo( data, value ) {
- // If found text, we can certainly put the focus in it. Let's just find a correct position
- // based on the unit.
- if ( value.type == 'text' ) {
- return getCorrectPosition( data.walker, data.unit );
- }
- // Entering an element.
- if ( value.type == ( data.isForward ? 'elementStart' : 'elementEnd' ) ) {
- // If it's an object, we can select it now.
- if ( data.schema.objects.has( value.item.name ) ) {
- return Position.createAt( value.item, data.isForward ? 'after' : 'before' );
- }
- // If text allowed on this position, extend to this place.
- if ( data.schema.check( { name: '$text', inside: value.nextPosition } ) ) {
- return value.nextPosition;
- }
- }
- // Leaving an element.
- else {
- // If leaving a limit element, stop.
- if ( data.schema.limits.has( value.item.name ) ) {
- // NOTE: Fast-forward the walker until the end.
- data.walker.skip( () => true );
- return;
- }
- // If text allowed on this position, extend to this place.
- if ( data.schema.check( { name: '$text', inside: value.nextPosition } ) ) {
- return value.nextPosition;
- }
- }
- }
- // Finds a correct position by walking in a text node and checking whether selection can be extended to given position
- // or should be extended further.
- function getCorrectPosition( walker, unit ) {
- const textNode = walker.position.textNode;
- if ( textNode ) {
- const data = textNode.data;
- let offset = walker.position.offset - textNode.startOffset;
- while ( isInsideSurrogatePair( data, offset ) || ( unit == 'character' && isInsideCombinedSymbol( data, offset ) ) ) {
- walker.next();
- offset = walker.position.offset - textNode.startOffset;
- }
- }
- return walker.position;
- }
- function getSearchRange( start, isForward ) {
- const root = start.root;
- const searchEnd = Position.createAt( root, isForward ? 'end' : 0 );
- if ( isForward ) {
- return new Range( start, searchEnd );
- } else {
- return new Range( searchEnd, start );
- }
- }
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