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

// Clients and Core Libraries

[<hdiagram> Clients and Core Libraries - Usage Overview|
    [<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]
]

[<vdiagram> Clients and Core Libraries - Major Modules|
  // Client

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

  [<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.
  ]

  // Editor

  [<editor> 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.
  ]
  [Dispatcher] --> Set New Bounds [<renderer> (Backchannel) To: Scheduler]
  [Dispatcher] Send Responses <-> Operations [Design Document Maintainer]
  
  [CLI Implementation] -> Send CLI Arguments [Design Document Maintainer]

  [<editor> State Stores|
    [<editor> Open Documents State Store|
        For each open document:|
        [<state> Pan and zoom canvas bounds]|
        [<state> Selected layers]
    ]

    [<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> Tool State Machine|
      List the possible operations in current context
  ]
  [Tool State Machine] <:- [State Stores]
  [Tool State Machine] -> Send Responses & Operations [Dispatcher]
  [Frontend Implementation] Send Responses <-> Send Events [Dispatcher]
  [Dispatcher] <:-> Send Actions [State Stores]
  [<renderer> (Backchannel) From: Final Render Assembler] --> Send Responses with Rendered Viewport [Dispatcher]

  // 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] -> Send Design Document Diff [Render Graph Maintainer]
  [Design Document Maintainer] <:-> Write Updated GDD [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] <:-> Write Updated GRD [Open Documents File Store]
  [Render Graph Maintainer] -> Send Render Graph [Scheduler]

  [<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] Set New Bounds <-- [<editor> (Backchannel) From: Dispatcher]
  [Scheduler] -> Rasterize Tiles [Node Rasterizer] 
  [Scheduler] <:-> Write Dirty Status [Node Cache Manager] 
  [Scheduler] -> Invoke [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] <:-> Write Tiles [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] --> Send Rendered Viewport to Client [<client> (Backchannel) To: Frontend Implementation]
]