Tweak runahead docs.

Author: hjoliver

src/7-to-8/major-changes/scheduling.rst

@@ -23,7 +23,8 @@ Cylc can manage infinite workflows of repeating tasks:
 
 Cylc 8 has a new scheduling algorithm that:
 
-- Is much more efficient because it only has to manage :term:`active tasks`.
+- Is much more efficient because it only has to manage
+  :term:`active tasks <active task>`.
 
   - Tasks are not loaded into memory before they are needed.
   - Tasks are not retained in memory once they complete.

src/glossary.rst

@@ -982,7 +982,8 @@ Glossary
       This refers to starting a new instance of the Cylc :term:`scheduler`
       program to manage a particular :term:`workflow`. This can be from
       scratch, for installed workflows that haven't run previously, or to
-      restart one that shut down prior to :ref:`completion <workflow completion>`.
+      restart one that shut down prior to
+      :ref:`completion <workflow completion>`.
 
       .. seealso::
 
@@ -1691,7 +1692,7 @@ Glossary
 
 
    flow front
-      :term:`Active tasks <active task>`` with a common :term:`flow number`
+      :term:`Active tasks <active task>` with a common :term:`flow number`
       comprise the active front of the flow.
 
 

src/user-guide/running-workflows/reflow.rst

@@ -122,7 +122,7 @@ Triggering with No Active Flows
    task in it. The task's flow number will be the same as if you
    had triggered it just before the workflow completed.
 
-Special Case: Triggering ``n=0`` (:term:`active tasks <active task`)
+Special Case: Triggering ``n=0`` (:term:`active tasks <active task>`)
    Active tasks already have flow membership assigned.
    Flow numbers are inherited, on entering the active wndow, from parent
    (upstream) tasks in the graph.

src/user-guide/running-workflows/tasks-jobs-ui.rst

@@ -117,8 +117,8 @@ it displays all tasks a configurable :term:`n-window` around the current
 
 
 n=0:
-   The ``n=0`` window contains current :term:`active tasks`: those that are
-   near ready to run, running, or which require user intervention.
+   The ``n=0`` window contains current :term:`active tasks <active task>`: those
+   that are near ready to run, running, or which require user intervention.
 n=1:
    The ``n=1`` window contains the ``n=0`` tasks plus those out
    to *one* graph edge around them in the graph.

src/user-guide/running-workflows/workflow-completion.rst

@@ -5,7 +5,7 @@ Workflow Completion
 
 A workflow can :term:`shut down <shutdown>` once all
 :term:`active tasks <active task>` complete without spawning further
-downstream activity - i.e., when :term:`n=0 window` empties out.
+downstream activity - i.e., when :term:`n=0 window <n-window>` empties out.
 
 .. _scheduler stall:
 

src/user-guide/writing-workflows/scheduling.rst

@@ -1534,7 +1534,7 @@ So, in the cycle ``2000-01-01T00:00Z``:
 * ``foo`` would expire at ``2000-01-01T00:00Z``.
 * ``bar`` would expire at ``2000-01-01T01:00Z``.
 
-Only waiting tasks can expire, :term:`active tasks <active>` will not be
+Only waiting tasks can expire, :term:`active tasks <active task>` will not be
 killed if they pass their configured ``clock-expire`` time.
 
 When a task expires, it produces the ``expired`` :term:`output`.
@@ -2219,17 +2219,23 @@ executing, e.g:
 Runahead Limiting
 -----------------
 
-Runahead limiting prevents workflow activity from getting too far ahead of the
-earliest :term:`active cycle`, by holding back tasks in cycles beyond a
-configurable limit.
+Runahead limiting restricts workflow activity to a configurable number of
+cycles beyond the earliest :term:`active cycle`.
 
-Tasks in cycles beyond the runahead limit are called "runahead limited" and are
-displayed in the GUI/Tui with small circle above them:
+.. TODO - update this after https://github.com/cylc/cylc-flow/issues/5580:
+
+Tasks in the :term:`n=0 window <n-window>` at the runahead limit are actively
+held back, and are displayed in the GUI/Tui with a small circle above them.
 
 .. image:: ../../img/task-job-icons/task-isRunahead.png
    :width: 60px
    :height: 60px
 
+.. note::
+
+   Tasks in the :term:`n=1 window <n-window>` are not displayed as runahead
+   limited; they form the future graph and are not yet being actively limited.
+
 As the workflow advances and active cycles complete, the runahead limit moves
 forward allowing tasks in later cycles to run.