Auto Placement should not put elements on top of existing flows

[romero83]

The auto placement feature may place elements on top of existing sequence flows:

We should circumvent this issue, as this particular situation is hard to grasp for users.

Tasks

• Update Auto Placement to not put elements on top of existing sequence flows

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Original Bug Report:

Hi!

I am using bpmn-js version 0.26.4.
When I want to create a new inner element from the previous element context pad (which already has an output sequence flow line), if there is enough space to the element creation but there is already an sequence flow line placed, it creates the element on the sequence flow line which is annoying and can lead to hardly interpretable and visible business flow.

Expected Behavior

• Should merge the newly created element into the already placed sequence flow.
• Can be that the new element placed beside the sequence line.
• The user cannot create element from the element context pad if it already has an outgoing sequence flow. It is still possible to create new element from the left menu.
• I don't know.

Actual Behavior
Newly created element placed on the sequence flow line.

Steps to reproduce the Behavior

1. Create a new BPMN
2. From the start event, create and end event from the element's context pad
3. Move the end event horizontally far enough to let space to the element which will be created
4. Click on the start event and from the context pad, create a new element

See

[nikku]

Thanks for reporting this issue.

From the alternatives you've provided I'd personally go with:

Expected Behavior

• Task is placed below the existing sequence flow

[romero83]

Hi!

Unfortunately I found a new major problem in this particular bug which is not anymore just an UX problem.
Stick to the example gif what I reported. When user creates the task between the start and the end event the program creates a new sequence flow from the start event to the newly created task.
However when user "merge" this task after back to the original flow it duplicates the sequence flow while on the surface you see only one sequence flow line! It cause major problem when user tries to run this kind of workflow process!
It might can be fixed also in engine side (backend) to validate proper source XML before send it into engine to filter out these kind of problems.

[nikku]

Yea, that is indeed an issue. A different one though.

[nikku]

How would you address this from the UI side of things?

[romero83]

The auto placement stuff works if the task has no out sequence flow. In that case it cannot be a problem because it will be sure that only one out sequence flow will be placed. But If a task has an out sequence flow in that case program should fall back to user side to manually drop the task.

[nikku]

[...] But If a task has an out sequence flow in that case program should fall back to user side to manually drop the task.

We cannot go with this option, as it is not gonna be understandable for the user.

However, I consider changing the drop on flow behavior to remove duplicate incoming and outgoing connections (as I cannot figure out a scenario where these would make sense).

[romero83]

Multiple outcoming sequence flows can be at start gateways.
Multiple incoming sequence flows can be at end gateways.

[romero83]

Or do not take it intolerant its just an option but please consider also to drop this kind of auto placement stuff and revert back to that method where user decided manually where to put the task in the flow.
Yes, in that case user has to do an extra click and cannot fast build a "one-liner" process, but on the other side user get extra safety and precision to build the process which I think is the most important thing in a business flow.

[nikku]

Did you try dragging out elements from the context menu? It achieves exactly what you mentioned:

• dragging out = full control where to put it (old behavior)
• clicking = placing automatically at an appropriate place

[nikku]

A small visualization regarding my previous comment:

However, I consider changing the drop on flow behavior to remove duplicate incoming and outgoing connections (as I cannot figure out a scenario where these would make sense).

As you can see, there are certain cases where sequence flows are not equivalent (i.e. because they are default or have conditions assigned). There are other cases though where it makes absolutely no sense to keep these (scenario two). From the BPMN prespective this would otherwise be equivalent to a AND gateway.

[nikku]

As mentioned, I believe both issues should be tackled / investigated separately.

I've opened #774 for the sequence flow duplication issue.

[romero83]

dragging out = full control where to put it (old behavior)
clicking = placing automatically at an appropriate place

I did not know about it. Thanks for pointing it out.

[nikku]

So I guess we can close this issue?

[romero83]

It is still a problem that the automatic placement render the task on the sequence flow (like it was merged) and hard to see what is happening.

[nikku]

Additional feedback we got convinced me that this is an actual issue.

We'll improve auto-placement to ensure elements are not being dropped on incoming or outgoing sequence flows.

[nikku]

Parts of this issue, namely the duplication of sequence flows got addressed via #774.

[nikku]

I've updated the issue description to reflect the work left to close this issue.

[christian-konrad]

This is part of refactoring actions (as it applies mostly to the "modify" phase of the developer/modeler job journey).