Merge 1720dbc into 250f8f2

src/conversion/downcasthelpers.js

@@ -204,6 +204,19 @@ export default class DowncastHelpers extends ConversionHelpers {
 	 *			view: modelAttributeValue => ( { key: 'class', value: 'styled-' + modelAttributeValue } )
 	 *		} );
 	 *
+	 * *Note:* Downcasting to a style properties requires providing a style object as a `value`:
+	 *
+	 *		editor.conversion.for( 'downcast' ).attributeToAttribute( {
+	 *			model: 'lineHeight',
+	 *			view: modelAttributeValue => ( {
+	 *				key: 'style',
+	 *				value: {
+	 *					'line-height': modelAttributeValue,
+	 *					'border-bottom': '1px dotted #ba2'
+	 *				}
+	 *			} )
+	 *		} );
+	 *
 	 * See {@link module:engine/conversion/conversion~Conversion#for `conversion.for()`} to learn how to add a converter
 	 * to the conversion process.
 	 *

src/conversion/upcasthelpers.js

@@ -237,6 +237,33 @@ export default class UpcastHelpers extends ConversionHelpers {
 	 *			}
 	 *		} );
 	 *
+	 * Converting styles is a bit different as it requires an object to be set as a `value` and by default
+	 * a model attribute's value will be set to `true`. You can set any value by providing a `value` callback
+	 * that returns a desired value.
+	 *
+	 *		// Default conversion of font-weight style will result in setting bold attribute to true.
+	 *		editor.conversion.for( 'upcast' ).attributeToAttribute( {
+	 *			view: {
+	 *				styles: {
+	 *					'font-weight': 'bold'
+	 *				}
+	 *			},
+	 *			model: 'bold'
+	 *		} );
+	 *
+	 *		// This converter will pass any value of a style property define a callback.
+	 *		editor.conversion.for( 'upcast' ).attributeToAttribute( {
+	 *			view: {
+	 *				styles: {
+	 *					'line-height': /[\s\S]+/
+	 *				}
+	 *			},
+	 *			model: {
+	 *				key: 'lineHeight',
+	 *				value: viewElement => viewElement.getStyle( 'line-height' )
+	 *			}
+	 *		} );
+	 *
 	 * See {@link module:engine/conversion/conversion~Conversion#for `conversion.for()`} to learn how to add a converter
 	 * to the conversion process.
 	 *