Add support for multilines labels

[Gelio]

• I have checked that this bug has not yet been reported by someone else
• I have checked that this bug appears on Chrome
• I have specified the version :

• other: 0.4.6

• I have specified my environment :

• Ubuntu 20.04 LTS

Screenshots

Sirius Desktop

Sirius Web (a long single line label)

Steps to reproduce

In the Label Expression for a node, add a newline

Expected behavior

The newline makes the rest of the text appear on a new line

Actual behavior

The text appears on a single line. The newline is turned into a space.

[pcdavid]

It looks like Sprotty might support this since 0.8.0 via eclipse-sprotty/sprotty#171
See also eclipse-elk/elk#476. Maybe we'll ask @lredor for his ELK expertise :-)

[lfasani]

Specification

Model

The model owns somewhere an entity with an attribute of type string. There is currently not the information about if the string is mono or multiline.
So let's consider that or line return is serialized with \n
The end-user '\n' string will be serialized escaped with '\n'

Representation

Every representation of a string attribute should manage the mono or multiline information based on th \n character

Form representation

By default, the form representation represents a string with a textField. But a string could also be represented by a textArea

The textField will display \n with \n and \\n with \\n

The textArea will display \n with a carriage return and \\n with \n

Sprotty

The label will display \n with a carriage return and \\n with \n
Idem when editing the text

As a second step, we could configure a maximum text length for the label display. That means that if the label is longer than the maximum length, a line is cut and returned as many times to comply with the maximum length

backend layout

The ELK and incremental layout should adapt to mange the fact the a label can be displayed on many lines.
The is necessary so that the parent node have the right size and so that the children nodes will not overlap the parent node label