Key Features

1. Task bars, summary bars, and milestones — each task can be rendered as a standard bar, a collapsible summary bar (for parent tasks), or a milestone diamond.
2. Predecessor / successor dependencies — source_ids and target_ids Many2many fields on project.task are automatically mirrored to grev.gantt.link as Finish-to-Start links.
3. Critical path highlighting — the longest chain of dependent tasks is highlighted on the chart in real time.
4. Scheduling constraints — per-task constraints: As Soon As Possible, As Late As Possible, Start No Earlier Than, Finish No Earlier Than, Start No Later Than, Finish No Later Than, and Must Start On.
5. Per-task hex colour — gantt_color_hex field controls bar colour (editable from the task form).
6. Gantt progress — gantt_progress (0–100 %) shows a fill inside each bar and can be edited inline.
7. Resource histogram — allocated hours per assignee (user_ids) or per project (project_id) displayed below the Gantt grid.
8. Baseline snapshots — store named planned-start/end dates; overlaid as dashed bars.
9. Auto-schedule — drag any bar to reschedule; successors cascade automatically.

Accessing the Gantt View

After installation, the Gantt view is available from:

• :menuselection:`Project --> Gantt --> All Tasks (Gantt)`
• :menuselection:`Project --> Gantt --> My Tasks (Gantt)`

You can also switch to the Gantt view from any project's task list by clicking the :icon:`fa-tasks` :guilabel:`Gantt` button in the view switcher.

Configuring a Task

Open any task form and click the :guilabel:`Gantt` tab to access scheduling fields:

Setting Dependencies

1. Open a task form and go to the :guilabel:`Gantt` tab.
2. In the :guilabel:`Predecessor Tasks` field, add any tasks that must complete first.
3. Save the task. The mixin automatically creates the corresponding grev.gantt.link record — no manual link creation needed.
4. The dependency arrow appears on the Gantt chart immediately.

Scheduling Constraints

Set the :guilabel:`Constraint Type` on a task to control how the auto-scheduler treats it:

Tasks with a non-ASAP/ALAP constraint display an orange warning decoration on the bar.

Rescheduling Tasks

Drag any task bar on the Gantt chart. The server:

1. Updates date_start and date_deadline for the dragged task.
2. Computes the time-shift delta.
3. Cascades the shift to all successor tasks (via target_ids).
4. Returns old values for the undo action.

Click :guilabel:`Undo` in the Gantt toolbar to roll back the last reschedule.

Working with the Critical Path

Enable critical path in the toolbar to highlight the tasks that determine the project's minimum duration. Any delay to a critical task directly delays the project end date.

Using Baselines

1. Open a task and go to the :guilabel:`Gantt` tab.
2. In the :guilabel:`Baselines` list, click :guilabel:`Add a line`.
3. Enter a name (e.g. "Initial Plan"), snapshot date, planned start, planned end, and hours.
4. Save. Toggle :guilabel:`Show Baselines` in the Gantt toolbar to overlay the baseline dashed bars against the current schedule.

Fields Added to project.task

_grev_gantt_progress_bar Override

GrevProjectTaskExt overrides _grev_gantt_progress_bar() to return allocated-vs-available hours per project or assignee from the task domain.

def _grev_gantt_progress_bar(self, field, res_ids, start_date, stop_date):
    if field in ('user_ids', 'project_id'):
        for res_id in res_ids:
            # sum allocated_hours for tasks in range
            ...