144 lines
5.0 KiB
Org Mode
144 lines
5.0 KiB
Org Mode
#+TITLE: Dirty Tracking
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#+STARTUP: content
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#+FILETAGS: :cl-tty:components:
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* Overview
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The dirty tracking module provides a mixin class and protocol for
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marking components as needing re-render. This is the foundation of
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the incremental rendering pipeline.
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Without dirty tracking, every frame would re-render every component.
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With it, only components that changed (and their ancestors, for layout
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recomputation) get re-processed. The makes the difference between a
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60fps terminal UI and a flickering mess.
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This module is intentionally minimal: a single mixin class and two
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generic functions. The complexity lives in the propagation logic
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(see ~render.lisp~), but the dirty state itself is trivial.
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* Contract
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** ~dirty-mixin~
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A class that adds a ~dirty~ slot. Components that need dirty tracking
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inherit from this.
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- ~(dirty-p component)~ — returns ~t~ if the component needs re-render,
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~nil~ if it's up-to-date. New instances start dirty (~t~).
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** ~mark-clean~
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- ~(mark-clean component)~ — sets dirty to ~nil~. Called after rendering.
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- Specialized on ~dirty-mixin~; default method is a no-op.
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** ~mark-dirty~
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- ~(mark-dirty component)~ — sets dirty to ~t~. Called when the component's
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state changes (user typed a character, selection changed, etc.).
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- Specialized on ~dirty-mixin~; default method is a no-op.
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* Tests
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** ~dirty-mixin-default-is-dirty~
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This test verifies that a freshly created ~dirty-mixin~ instance starts
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with ~dirty~ set to ~t~. This is the core invariant of the dirty tracking
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system — without this, the first render pass would skip new components,
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making them invisible until something explicitly marked them dirty.
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#+BEGIN_SRC lisp :tangle ~/.local/share/cl-tty/src/components/dirty-tests.lisp
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(in-package :cl-tty-box-test)
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(in-suite box-suite)
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(test dirty-mixin-default-is-dirty
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"A dirty-mixin starts as dirty"
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(let ((c (make-instance 'dirty-mixin)))
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(is-true (dirty-p c) "new component should be dirty")))
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#+END_SRC
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** ~mark-clean-clears-dirty~
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This test checks that calling ~mark-clean~ on a dirty component sets its
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~dirty-p~ to ~nil~. This is called after a component is rendered,
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signaling that it is up-to-date and does not need re-render until the
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next change. Without this, every component would be re-rendered every
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frame.
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#+BEGIN_SRC lisp :tangle ~/.local/share/cl-tty/src/components/dirty-tests.lisp
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(in-package :cl-tty-box-test)
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(in-suite box-suite)
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(test mark-clean-clears-dirty
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"mark-clean sets dirty to nil"
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(let ((c (make-instance 'dirty-mixin)))
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(mark-clean c)
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(is-false (dirty-p c) "after mark-clean, should not be dirty")))
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#+END_SRC
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** ~mark-dirty-sets-dirty~
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This test verifies that a component that has been cleaned can be
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re-marked as dirty via ~mark-dirty~. This exercises the full lifecycle:
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new (dirty) → render (mark-clean) → state change (mark-dirty) → render
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again. It ensures the dirty flag is not a one-shot toggle.
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#+BEGIN_SRC lisp :tangle ~/.local/share/cl-tty/src/components/dirty-tests.lisp
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(in-package :cl-tty-box-test)
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(in-suite box-suite)
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(test mark-dirty-sets-dirty
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"mark-dirty sets dirty to t"
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(let ((c (make-instance 'dirty-mixin)))
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(mark-clean c)
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(mark-dirty c)
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(is-true (dirty-p c) "after mark-dirty, should be dirty again")))
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#+END_SRC
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* Implementation
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The entire module is a class and two generic functions. The design
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choice: make this a separate mixin rather than part of the base
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~component~ class. This lets non-UI objects (layout nodes, render
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commands) opt into dirty tracking without inheriting from component.
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#+BEGIN_SRC lisp :tangle ~/.local/share/cl-tty/src/components/dirty.lisp
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(in-package :cl-tty.box)
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;; ── Dirty Tracking ─────────────────────────────────────────────
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(defclass dirty-mixin ()
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((dirty :initform t :accessor dirty-p)))
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#+END_SRC
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The ~initform t~ is critical: new components are dirty by default so
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the first render pass doesn't skip them. If this default were ~nil~,
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new components would be invisible until something explicitly marked
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them dirty.
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#+BEGIN_SRC lisp :tangle ~/.local/share/cl-tty/src/components/dirty.lisp
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(defgeneric mark-clean (component)
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(:method ((c dirty-mixin))
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(setf (dirty-p c) nil)))
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#+END_SRC
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~mark-clean~ is called at the end of a render cycle. The default
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method (for non-dirty-mixin components) is a no-op — they have no
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dirty state to clear.
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#+BEGIN_SRC lisp :tangle ~/.local/share/cl-tty/src/components/dirty.lisp
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(defgeneric mark-dirty (component)
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(:method ((c dirty-mixin))
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(setf (dirty-p c) t)))
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#+END_SRC
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~mark-dirty~ is called whenever the component's visual state changes.
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Together with ~propagate-dirty~ in the render pipeline, this ensures
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that when a text input gains a character, not just the input component
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but its containing box, tab, and screen all get re-rendered.
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These are generic functions (not plain functions) so other mixins or
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base classes can provide their own methods. The ~:method~ on
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~dirty-mixin~ provides the default implementation for anything that
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includes this mixin.
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