/**
* @license Copyright (c) 2003-2020, CKSource - Frederico Knabben. All rights reserved.
* For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
*/
/**
* @module table/converters/table-layout-post-fixer
*/
import TableWalker from './../tablewalker';
import { createEmptyTableCell, updateNumericAttribute } from '../utils/common';
/**
* Injects a table layout post-fixer into the model.
*
* The role of the table layout post-fixer is to ensure that the table rows have the correct structure
* after a {@link module:engine/model/model~Model#change `change()`} block was executed.
*
* The correct structure means that:
*
* * All table rows have the same size.
* * None of the table cells extend vertically beyond their section (either header or body).
* * A table cell has always at least one element as a child.
*
* If the table structure is not correct, the post-fixer will automatically correct it in two steps:
*
* 1. It will clip table cells that extend beyond their section.
* 2. It will add empty table cells to the rows that are narrower than the widest table row.
*
* ## Clipping overlapping table cells
*
* Such situation may occur when pasting a table (or a part of a table) to the editor from external sources.
*
* For example, see the following table which has a cell (FOO) with the rowspan attribute (2):
*
*
*
* FOO
* BAR
*
*
* BAZ
* XYZ
*
*
*
* It will be rendered in the view as:
*
*
*
*
* | FOO |
* BAR |
*
*
*
*
* | BAZ |
* XYZ |
*
*
*
*
* In the above example the table will be rendered as a table with two rows: one in the header and second one in the body.
* The table cell (FOO) cannot span over multiple rows as it would extend from the header to the body section.
* The `rowspan` attribute must be changed to (1). The value (1) is the default value of the `rowspan` attribute
* so the `rowspan` attribute will be removed from the model.
*
* The table cell with BAZ in the content will be in the first column of the table.
*
* ## Adding missing table cells
*
* The table post-fixer will insert empty table cells to equalize table row sizes (the number of columns).
* The size of a table row is calculated by counting column spans of table cells, both horizontal (from the same row) and
* vertical (from the rows above).
*
* In the above example, the table row in the body section of the table is narrower then the row from the header: it has two cells
* with the default colspan (1). The header row has one cell with colspan (1) and the second with colspan (2).
* The table cell (FOO) does not extend beyond the head section (and as such will be fixed in the first step of this post-fixer).
* The post-fixer will add a missing table cell to the row in the body section of the table.
*
* The table from the above example will be fixed and rendered to the view as below:
*
*
*
*
* | FOO |
* BAR |
*
*
*
*
* | BAZ |
* XYZ |
*
*
*
*
* ## Collaboration and undo - Expectations vs post-fixer results
*
* The table post-fixer only ensures proper structure without a deeper analysis of the nature of the change. As such, it might lead
* to a structure which was not intended by the user. In particular, it will also fix undo steps (in conjunction with collaboration)
* in which the editor content might not return to the original state.
*
* This will usually happen when one or more users change the size of the table.
*
* As an example see the table below:
*
*
*
*
* | 11 |
* 12 |
*
*
* | 21 |
* 22 |
*
*
*
*
* and the user actions:
*
* 1. Both users have a table with two rows and two columns.
* 2. User A adds a column at the end of the table. This will insert empty table cells to two rows.
* 3. User B adds a row at the end of the table. This will insert a row with two empty table cells.
* 4. Both users will have a table as below:
*
*
*
*
*
* | 11 |
* 12 |
* (empty, inserted by A) |
*
*
* | 21 |
* 22 |
* (empty, inserted by A) |
*
*
* | (empty, inserted by B) |
* (empty, inserted by B) |
*
*
*
*
* The last row is shorter then others so the table post-fixer will add an empty row to the last row:
*
*
*
*
* | 11 |
* 12 |
* (empty, inserted by A) |
*
*
* | 21 |
* 22 |
* (empty, inserted by A) |
*
*
* | (empty, inserted by B) |
* (empty, inserted by B) |
* (empty, inserted by the post-fixer) |
*
*
*
*
* Unfortunately undo does not know the nature of the changes and depending on which user applies the post-fixer changes, undoing them
* might lead to a broken table. If User B undoes inserting the column to the table, the undo engine will undo only the operations of
* inserting empty cells to rows from the initial table state (row 1 and 2) but the cell in the post-fixed row will remain:
*
*
*
*
* | 11 |
* 12 |
*
*
* | 21 |
* 22 |
*
*
* | (empty, inserted by B) |
* (empty, inserted by B) |
* (empty, inserted by a post-fixer) |
*
*
*
*
* After undo, the table post-fixer will detect that two rows are shorter than others and will fix the table to:
*
*
*
*
* | 11 |
* 12 |
* (empty, inserted by a post-fixer after undo) |
*
*
* | 21 |
* 22 |
* (empty, inserted by a post-fixer after undo) |
*
*
* | (empty, inserted by B) |
* (empty, inserted by B) |
* (empty, inserted by a post-fixer) |
*
*
*
* @param {module:engine/model/model~Model} model
*/
export default function injectTableLayoutPostFixer( model ) {
model.document.registerPostFixer( writer => tableLayoutPostFixer( writer, model ) );
}
// The table layout post-fixer.
//
// @param {module:engine/model/writer~Writer} writer
// @param {module:engine/model/model~Model} model
function tableLayoutPostFixer( writer, model ) {
const changes = model.document.differ.getChanges();
let wasFixed = false;
// Do not analyze the same table more then once - may happen for multiple changes in the same table.
const analyzedTables = new Set();
for ( const entry of changes ) {
let table;
if ( entry.name == 'table' && entry.type == 'insert' ) {
table = entry.position.nodeAfter;
}
// Fix table on adding/removing table cells and rows.
if ( entry.name == 'tableRow' || entry.name == 'tableCell' ) {
table = entry.position.findAncestor( 'table' );
}
// Fix table on any table's attribute change - including attributes of table cells.
if ( isTableAttributeEntry( entry ) ) {
table = entry.range.start.findAncestor( 'table' );
}
if ( table && !analyzedTables.has( table ) ) {
// Step 1: correct rowspans of table cells if necessary.
// The wasFixed flag should be true if any of tables in batch was fixed - might be more then one.
wasFixed = fixTableCellsRowspan( table, writer ) || wasFixed;
// Step 2: fix table rows sizes.
wasFixed = fixTableRowsSizes( table, writer ) || wasFixed;
analyzedTables.add( table );
}
}
return wasFixed;
}
// Fixes the invalid value of the `rowspan` attribute because a table cell cannot vertically extend beyond the table section it belongs to.
//
// @param {module:engine/model/element~Element} table
// @param {module:engine/model/writer~Writer} writer
// @returns {Boolean} Returns `true` if the table was fixed.
function fixTableCellsRowspan( table, writer ) {
let wasFixed = false;
const cellsToTrim = findCellsToTrim( table );
if ( cellsToTrim.length ) {
// @if CK_DEBUG_TABLE // console.log( `Post-fixing table: trimming cells row-spans (${ cellsToTrim.length }).` );
wasFixed = true;
for ( const data of cellsToTrim ) {
updateNumericAttribute( 'rowspan', data.rowspan, data.cell, writer, 1 );
}
}
return wasFixed;
}
// Makes all table rows in a table the same size.
//
// @param {module:engine/model/element~Element} table
// @param {module:engine/model/writer~Writer} writer
// @returns {Boolean} Returns `true` if the table was fixed.
function fixTableRowsSizes( table, writer ) {
let wasFixed = false;
const rowsLengths = getRowsLengths( table );
const rowsToRemove = [];
// Find empty rows.
for ( const [ rowIndex, size ] of rowsLengths.entries() ) {
if ( !size ) {
rowsToRemove.push( rowIndex );
}
}
// Remove empty rows.
if ( rowsToRemove.length ) {
// @if CK_DEBUG_TABLE // console.log( `Post-fixing table: remove empty rows (${ rowsToRemove.length }).` );
wasFixed = true;
for ( const rowIndex of rowsToRemove.reverse() ) {
writer.remove( table.getChild( rowIndex ) );
rowsLengths.splice( rowIndex, 1 );
}
}
// Verify if all the rows have the same number of columns.
const tableSize = rowsLengths[ 0 ];
const isValid = rowsLengths.every( length => length === tableSize );
if ( !isValid ) {
// @if CK_DEBUG_TABLE // console.log( 'Post-fixing table: adding missing cells.' );
// Find the maximum number of columns.
const maxColumns = rowsLengths.reduce( ( prev, current ) => current > prev ? current : prev, 0 );
for ( const [ rowIndex, size ] of rowsLengths.entries() ) {
const columnsToInsert = maxColumns - size;
if ( columnsToInsert ) {
for ( let i = 0; i < columnsToInsert; i++ ) {
createEmptyTableCell( writer, writer.createPositionAt( table.getChild( rowIndex ), 'end' ) );
}
wasFixed = true;
}
}
}
return wasFixed;
}
// Searches for table cells that extend beyond the table section to which they belong to. It will return an array of objects
// that stores table cells to be trimmed and the correct value of the `rowspan` attribute to set.
//
// @param {module:engine/model/element~Element} table
// @returns {Array.<{{cell, rowspan}}>}
function findCellsToTrim( table ) {
const headingRows = parseInt( table.getAttribute( 'headingRows' ) || 0 );
const maxRows = table.childCount;
const cellsToTrim = [];
for ( const { row, cell, cellHeight } of new TableWalker( table ) ) {
// Skip cells that do not expand over its row.
if ( cellHeight < 2 ) {
continue;
}
const isInHeader = row < headingRows;
// Row limit is either end of header section or whole table as table body is after the header.
const rowLimit = isInHeader ? headingRows : maxRows;
// If table cell expands over its limit reduce it height to proper value.
if ( row + cellHeight > rowLimit ) {
const newRowspan = rowLimit - row;
cellsToTrim.push( { cell, rowspan: newRowspan } );
}
}
return cellsToTrim;
}
// Returns an array with lengths of rows assigned to the corresponding row index.
//
// @param {module:engine/model/element~Element} table
// @returns {Array.}
function getRowsLengths( table ) {
// TableWalker will not provide items for the empty rows, we need to pre-fill this array.
const lengths = new Array( table.childCount ).fill( 0 );
for ( const { row } of new TableWalker( table, { includeAllSlots: true } ) ) {
lengths[ row ]++;
}
return lengths;
}
// Checks if the differ entry for an attribute change is one of the table's attributes.
//
// @param entry
// @returns {Boolean}
function isTableAttributeEntry( entry ) {
const isAttributeType = entry.type === 'attribute';
const key = entry.attributeKey;
return isAttributeType && ( key === 'headingRows' || key === 'colspan' || key === 'rowspan' );
}