[FEAT] Render the Ad-Hoc Marker of a Sub-Process

[csouchet]

Is your feature request related to a problem? Please describe.

BPMN specifies five types of standard markers for Sub-Processes. The (Collapsed) Sub-Process marker, seen in Figure 10.24, can be combined with four other markers: a loop marker or a multi-instance marker, a Compensation marker, and an Ad-Hoc marker. A collapsed Sub-Process MAY have one to three of these other markers, in all combinations except that loop and multi-instance cannot be shown at the same time (see Figure 10.28).

The detection of the ad-hoc subprocess must be implemented first, see #308

Render

A Sub-Process is marked as being ad-hoc with a “tilde” symbol placed at the bottom center of the Sub-Process shape (see Figure 10.35 and Figure 10.36).
The marker for an Ad-Hoc Sub-Process MUST be a “tilde” symbol.

The Ad-Hoc Marker MAY be used in combination with any of the other markers.
All the markers that are present MUST be grouped and the whole group centered at the bottom of the Sub-Process.

Describe the solution you'd like
Modify the mxGraph shape & the internal model to add those attributes.

Decision

Decided on 2024-04-04 (see #2724)

• adhoc subprocess icon: use the icon experimented in chore: [POC] Markers rendering improvements #2724
• prior implementing this feature, some general improvements applying to markers must be implemented first. See [FEAT] Apply various Activity Markers improvements #3146

[tbouffard]

Icon proposals (see also other icons from the nounproject: https://thenounproject.com/search/?q=tilde)

https://thenounproject.com/icon/651893/ See the marker in action in #2724 (comment)

https://thenounproject.com/icon/195062/

See also stencil from draw.io: https://github.com/jgraph/drawio/blob/v21.3.5/src/main/webapp/stencils/bpmn.xml