Graphite/docs/codebase/architecture-overview.nomnoml

#spacing: 120
#arrowSize: 0.5
#leading: 1.5
#gravity: 1
#direction: down
#bendSize: 0.2

#.dependencies: visual=note direction=right title=bold
#.client: visual=roundrect fill=lightgreen title=bold
#.editor: fill=lightblue title=bold
#.document: fill=darkorange title=bold
#.renderer: fill=gold title=bold

// Hierarchy

[<dependencies> Core Libraries|
    [<client> Frontend Editor Client]
    [<client> Headless Editor Client]
    [<client> Application Client
    (like a game engine or game that renders .grd graphs at runtime)]
    [<editor> Editor Core Library]
    [<document> Document Core Library]
    [<renderer> Renderer Core Library]
    
    [Frontend Editor Client] Depends On -> [Editor Core Library]
    [Editor Core Library] Depends On -> [Document Core Library]
    [Headless Editor Client] Depends On -> [Document Core Library]
    [Document Core Library] Depends On -> [Renderer Core Library]
    [Application Client] Depends On -> [Renderer Core Library]
]

// Client

[<client> Frontend Implementation|
    One of many possible frontend implementations,
    such as the native or web client.
]
[Frontend Implementation] -> Event [Editor Event Dispatcher]

[<client> CLI Implementation|
    A possible text-based CLI program that
    wraps Graphite Document. Users can
    pass a .gdd document and operation to
    add to the document history by saving
    to the supplied .gdd file. Users can also
    pass a .gdd document and request a
    render. Caches are saved to disk.
]
[CLI Implementation] -> [Design Document Maintainer]

// Editor

[<editor> Editor Event Dispatcher|
    Convert all events from the frontend into Actions
    and Operations. Actions are diffs to update state
    stores. Operations are history events in a .gdd
    file. Operations and document-specific Actions
    include the document ID in the call.
]
[Editor Event Dispatcher] -> Action [Editor State Store]
[Editor Event Dispatcher] -> Action [Open Documents State Store]
[Editor Event Dispatcher] -> Update Bounds [Scheduler]
[Editor Event Dispatcher] -> Operation [Design Document Maintainer]

[<editor> Editor State Store|
    [<state> Panel Layout]|
    [<state> Working Colors]|
    [<state> Active Tool]|
    [<state> Tool Options]|
    [<state> Modifier Key Input]|
    [<state> Currently Hovered Panel]
]
[Editor State Store] -> [Frontend Implementation]
[Editor State Store] -> [Tool State Machine]

[<editor> Open Documents State Store|
    For each open document:|
    [<state> Pan and zoom viewport bounds]|
    [<state> Selected layers]
]
[Open Documents State Store] -> [Tool State Machine]
[Open Documents State Store] -> [Frontend Implementation]

[<editor> Tool State Machine|
    List possible operations in current context
]
[Tool State Machine] -> [Frontend Implementation]

// Document

[<document> Design Document Maintainer|
    Process each operation and apply changes to the given document's
    operation chain. Consolidate changes where possible by modifying
    the previous operation if it's the same as this one and append partial
    updates to operations from in-progress interactive tools.
]
[Design Document Maintainer] -> Design Document Diff [Render Graph Maintainer]
[Design Document Maintainer] <-> Design Document [Open Documents File Store]

[<document> Render Graph Maintainer|
    Bake operations into a complete graph including history references.
    Starting from the beginning of document history, each operation
    modifies the graph in a specific way. If an operation creates a node
    that references this point in history, duplicate the current graph pieces
    between the live graph and each additional history reference so
    changed nodes in history are "ghost variants" living in the live graph.
]
[Render Graph Maintainer] -> Render Graph [Scheduler]
[Render Graph Maintainer] <-> Render Graph [Open Documents File Store]

[<document>Open Documents File Store|
    Kept in-memory or written to disk.|
    For each open document:|
    [<state> Design Document (.gdd)]|
    [<state> Render Graph (.grd)]
]

// Renderer

[<renderer> Scheduler|
    Manage a thread pool and GPU time. Perform progressive enhancement
    and speculative tile rendering. Request re-render of dirtied document within
    bounds and stitch them over dirty raster cache tiles. Maintain interactive
    responsiveness by targeting a minimum framerate and picking a requisite
    render quality level at all times. Precompute nodes downstream of changes
    when there is spare CPU thread pool and GPU time. Primary purpose is to
    keep the Precompute and Raster Tile caches up-to-date with minimal
    onscreen latency. Also notifies the Final Render Assembler when the cache
    tiles for the root document visible in bounds have finished being updated.
]
[Scheduler] -> [Node Rasterizer] 
[Scheduler] <-> [Node Cache Manager] 
[Scheduler] -> [Final Render Assembler] 

[<renderer> Node Cache Manager|
    Purges old or less useful cached data
    as necessary.|
    [<state> Precompute Node Cache|
        Prepare data for rasterization step.
        Evaluate algorithms (CPU or GPU).
        Changes when upstream changes.
    ]|
    [<state> Raster Tile Node Cache|
        Must be fast, fragment shader only.
        Only reevaluate downstream.
        Reuse when panning.
    ]
]
[Node Cache Manager] -> [Final Render Assembler]

[<renderer> Node Rasterizer|
    Rasterize and update the cache for a specified node
    given a preferred bounds (but it can give a different
    sized output), resolution, and quality level.
]
[Node Rasterizer] <-> [Node Cache Manager]

[<renderer> Final Render Assembler|
    Look up the rasterized cached tiles from
    the document root and assemble them into
    an image for live display by the frontend.
    Operates when woken up by the scheduler
    when root tiles or render bounds are updated.
]
[Final Render Assembler] --> Rendered Viewport [Frontend Implementation]