src/view/filler.js
/**
* @license Copyright (c) 2003-2020, CKSource - Frederico Knabben. All rights reserved.
* For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
*/
import { keyCodes } from '@ckeditor/ckeditor5-utils/src/keyboard';
import isText from '@ckeditor/ckeditor5-utils/src/dom/istext';
/**
* Set of utils related to block and inline fillers handling.
*
* Browsers do not allow to put caret in elements which does not have height. Because of it, we need to fill all
* empty elements which should be selectable with elements or characters called "fillers". Unfortunately there is no one
* universal filler, this is why two types are uses:
*
* * Block filler is an element which fill block elements, like `<p>`. CKEditor uses `<br>` as a block filler during the editing,
* as browsers do natively. So instead of an empty `<p>` there will be `<p><br></p>`. The advantage of block filler is that
* it is transparent for the selection, so when the caret is before the `<br>` and user presses right arrow he will be
* moved to the next paragraph, not after the `<br>`. The disadvantage is that it breaks a block, so it can not be used
* in the middle of a line of text. The {@link module:engine/view/filler~BR_FILLER `<br>` filler} can be replaced with any other
* character in the data output, for instance {@link module:engine/view/filler~NBSP_FILLER non-breaking space}.
*
* * Inline filler is a filler which does not break a line of text, so it can be used inside the text, for instance in the empty
* `<b>` surrendered by text: `foo<b></b>bar`, if we want to put the caret there. CKEditor uses a sequence of the zero-width
* spaces as an {@link module:engine/view/filler~INLINE_FILLER inline filler} having the predetermined
* {@link module:engine/view/filler~INLINE_FILLER_LENGTH length}. A sequence is used, instead of a single character to
* avoid treating random zero-width spaces as the inline filler. Disadvantage of the inline filler is that it is not
* transparent for the selection. The arrow key moves the caret between zero-width spaces characters, so the additional
* code is needed to handle the caret.
*
* Both inline and block fillers are handled by the {@link module:engine/view/renderer~Renderer renderer} and are not present in the
* view.
*
* @module engine/view/filler
*/
/**
* Non-breaking space filler creator. This is a function which creates ` ` text node.
* It defines how the filler is created.
*
* @see module:engine/view/filler~BR_FILLER
* @function
*/
export const NBSP_FILLER = domDocument => domDocument.createTextNode( '\u00A0' );
/**
* `<br>` filler creator. This is a function which creates `<br data-cke-filler="true">` element.
* It defines how the filler is created.
*
* @see module:engine/view/filler~NBSP_FILLER
* @function
*/
export const BR_FILLER = domDocument => {
const fillerBr = domDocument.createElement( 'br' );
fillerBr.dataset.ckeFiller = true;
return fillerBr;
};
/**
* Length of the {@link module:engine/view/filler~INLINE_FILLER INLINE_FILLER}.
*/
export const INLINE_FILLER_LENGTH = 7;
/**
* Inline filler which is a sequence of the zero width spaces.
*/
export const INLINE_FILLER = ( () => {
let inlineFiller = '';
for ( let i = 0; i < INLINE_FILLER_LENGTH; i++ ) {
inlineFiller += '\u200b';
}
return inlineFiller;
} )(); // Usu IIF so the INLINE_FILLER appears as a constant in the docs.
/**
* Checks if the node is a text node which starts with the {@link module:engine/view/filler~INLINE_FILLER inline filler}.
*
* startsWithFiller( document.createTextNode( INLINE_FILLER ) ); // true
* startsWithFiller( document.createTextNode( INLINE_FILLER + 'foo' ) ); // true
* startsWithFiller( document.createTextNode( 'foo' ) ); // false
* startsWithFiller( document.createElement( 'p' ) ); // false
*
* @param {Node} domNode DOM node.
* @returns {Boolean} True if the text node starts with the {@link module:engine/view/filler~INLINE_FILLER inline filler}.
*/
export function startsWithFiller( domNode ) {
return isText( domNode ) && ( domNode.data.substr( 0, INLINE_FILLER_LENGTH ) === INLINE_FILLER );
}
/**
* Checks if the text node contains only the {@link module:engine/view/filler~INLINE_FILLER inline filler}.
*
* isInlineFiller( document.createTextNode( INLINE_FILLER ) ); // true
* isInlineFiller( document.createTextNode( INLINE_FILLER + 'foo' ) ); // false
*
* @param {Text} domText DOM text node.
* @returns {Boolean} True if the text node contains only the {@link module:engine/view/filler~INLINE_FILLER inline filler}.
*/
export function isInlineFiller( domText ) {
return domText.data.length == INLINE_FILLER_LENGTH && startsWithFiller( domText );
}
/**
* Get string data from the text node, removing an {@link module:engine/view/filler~INLINE_FILLER inline filler} from it,
* if text node contains it.
*
* getDataWithoutFiller( document.createTextNode( INLINE_FILLER + 'foo' ) ) == 'foo' // true
* getDataWithoutFiller( document.createTextNode( 'foo' ) ) == 'foo' // true
*
* @param {Text} domText DOM text node, possible with inline filler.
* @returns {String} Data without filler.
*/
export function getDataWithoutFiller( domText ) {
if ( startsWithFiller( domText ) ) {
return domText.data.slice( INLINE_FILLER_LENGTH );
} else {
return domText.data;
}
}
/**
* Assign key observer which move cursor from the end of the inline filler to the beginning of it when
* the left arrow is pressed, so the filler does not break navigation.
*
* @param {module:engine/view/view~View} view View controller instance we should inject quirks handling on.
*/
export function injectQuirksHandling( view ) {
view.document.on( 'keydown', jumpOverInlineFiller );
}
// Move cursor from the end of the inline filler to the beginning of it when, so the filler does not break navigation.
function jumpOverInlineFiller( evt, data ) {
if ( data.keyCode == keyCodes.arrowleft ) {
const domSelection = data.domTarget.ownerDocument.defaultView.getSelection();
if ( domSelection.rangeCount == 1 && domSelection.getRangeAt( 0 ).collapsed ) {
const domParent = domSelection.getRangeAt( 0 ).startContainer;
const domOffset = domSelection.getRangeAt( 0 ).startOffset;
if ( startsWithFiller( domParent ) && domOffset <= INLINE_FILLER_LENGTH ) {
domSelection.collapse( domParent, 0 );
}
}
}
}