Debug mode: forward/back navigation through completed steps in Variable changes mode

[NikitaShchienko]

Feature Description

Extend the existing Variable changes mode on the process instance diagram: add "forward / back" buttons for switching between the completed steps of the process in their execution order. On each switch: the selected step is highlighted on the BPMN diagram (with auto-scroll to the element), and the variable values at that stage are displayed next to it. Currently the mode requires manually clicking on an activity — button navigation will allow stepping through the process execution sequentially. The feature is purely informational and does not affect process execution.

Scope

• "Forward / back" buttons in the Variable changes mode panel; step order is based on activity instance history (startTime/endTime)
• Highlighting of the current step + auto-scroll (existing markers and ScrollToElementCmd).
• Displaying variable values for the selected step (based on the existing process variable change history, History of changes in process variables #254); decide whether to show the changes made at the step or the full set of values as of that step.
• Position indicator (e.g. "step 3 of 12") and edge states (first/last step).

[m-orlova]

Results of R&D: step-by-step navigation through activities

Where: Process instance → diagram → Variable changes mode.

What it does

Before, each element had to be clicked on the diagram to see its variable changes. Now there is an ability to step through the process one activity at a time.

Next to the Variable changes tab there is a row of arrows: first activity, previous, next, last. Between them there is a counter, for example "Activity 3 of 12".

How to use it

1. Open a process instance and switch the diagram to Variable changes mode.
2. Click any element on the diagram, or press the forward arrow to start from the first activity.
3. Each press moves you one activity forward or back, in the order the activities were executed. The diagram highlights the activity, and the panel below shows its variable changes.
4. The double arrows jump to the first or the last activity.
5. Arrows that lead nowhere are disabled. At the first activity you can only go forward, at the last one only back.
6. The activity details now show the End time as well as the Start time.

Good to know

• The arrows and clicks on the diagram work together. The counter, the highlighted element, the selected row in the activity list and the variable changes always show the same activity.
• An element executed several times (multi-instance) counts as one activity, so the navigation is not filled with repeated iterations.
• Activities that are still running and have no history yet are placed at the end. Pressing the last arrow brings you to where the process is now.