Robotics Service Bus

Pruning of inactive sub-styles in formatting/style-mixins.lisp

fixes #1918

Sub-styles of monitor styles track their most recent activity via
`activity-tracking-mixin' and the monitor style prunes sub-styles via
`activity-based-sub-style-pruning-mixin'.

• formatting/protocol.lisp (style-prune-predicate): new generic
  function; return prune predicate of a style
  (setf style-prune-predicate): new generic function; set prune
  predicate of a style
  (prune-sub-styles): new generic function; remove sub-style according
  to prune predicate
• formatting/style-mixins.lisp (activity-tracking-mixin): new class;
  stores time of most recent activity
  (format-event :around t activity-tracking-mixin t): new method; update
  time of most recent activity
  (sub-style-pruning-mixin): new class; adds pruning of dynamically
  created sub-styles
  (prune-sub-styles sub-style-pruning-mixin): new method; prune
  sub-styles according to prune predicate
  (format-event :before eql :trigger sub-style-pruning-mixin t): new
  method; prune sub-styles before producing output
  (activity-based-sub-style-pruning-mixin): new class; specialized
  sub-style pruning based on time of most recent activity
  (shared-initialize :after activity-based-sub-style-pruning-mixin t):
  new method; accept pruning threshold or predicate
  (prune-after): new function; helper function for constructing
  activity-time-based pruning predicates
• formatting/event-style-monitor.lisp (basic-monitor-line-style): new
  class; statistics columns with activity tracking
  (basic-monitor-style): added superclass
  `activity-based-sub-style-pruning-mixin'
  (make-sub-style-entry basic-monitor-style t): instantiate
  `basic-monitor-line-style'
• formatting/package.lisp (package rsb.formatting): added exported
  symbols style-prune-predicate, prune-sub-styles,
  sub-style-pruning-mixin, activity-based-sub-style-pruning-mixin,
  activity-tracking-mixin and style-last-activity
• test/formatting/style-mixins.lisp
  (test suite activity-based-sub-style-pruning-mixin-root): new test
  suite; for `activity-based-sub-style-pruning-mixin' class
  (test activity-based-sub-style-pruning-mixin-root::construct): new
  test; test construction of `activity-based-sub-style-pruning-mixin'
  instances
• test/formatting/package.lisp (package rsb.formatting.test): added used
  package more-conditions