Graphite/docs/editor/1-overview.md

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# Overview
## Key concepts
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## Glossary of terminology
TODO: Add more to make a comprehensive list, finish writing definitions, separate into categories, alphabetize
- Asset
A *GDD* or *GRD* file. Can be shared and *embedded* in another *layer graph*. Useful for providing custom *nodes* that perform some useful functionality. Tangible examples include custom procedural effects, shape generators, and image filters. Many of the Graphite editor's built-in *layers* are also assets that provide useful functionality through a group of nodes rather than being implemented directly in code. The *Asset Manager* panel helps maintain these assets from various sources. The *Asset Store* can be used to share and sell assets for easily inclusion in projects.
- Document
A design source file created and edited in the Graphite editor. When saved to disk as *GDD files* (Graphite Design Document), they are one of the two types of *assets*. Documents can be included as *layers* inside other documents, and in doing so they take the form of *groups*. The *layer graph* contents of a *group* actually belong to the *embedded* document's *subgraph*. Because a document is a *group* which is a *layer* in the *layer graph*, documents have *properties* such as the *frames* in the *canvas*. Documents are composed of a layer graph, a defined set of properties of set *data types* that are *imported* and *exported*, and the *properties* of the *root layer*.
- Render graph
A read-only "compiled" *document* in a format that is immediately ready for rendering. When saved to disk as *GRD files* (Graphite Render Data), they are one of the two types of *assets*. The Graphite editor internally maintains a render graph based on the open document in order to display the *canvas* live in the *viewport*, but this can also be saved to disk for the purposes of sharing as an *asset*.
- GDD file
Graphite Design Document. A binary serialization of a *document* source file. The format includes a chain of *operations* that describe changes to the *layer graph* and the *properties* of *layers* throughout the history of the document since its creation. It also stores certain metadata and *embedded* file data. GDD files, along with *GRD files*, represent *assets* when shared. Because GDD files are editable (unlike *GRD files*), the *layers* of GDD *assets* may be expanded in the layer graph to reveal and modify their contents using a copy-on-write scheme stored to the *asset's* *layer*.
- GRD file
Graphite Render Data. A binary serialization of a *render graph* file. The format includes a single directed acyclic graph (DAG) compiled from the *layer graph* of a *document* as well as certain *properties* of set *data types* that are *imported* and *exported*. GRD files, along with *GDD files*, represent *assets* when shared. Because GRD files are read-only and can't be edited (unlike *GDD files*), the *layers* of GRD *assets* do not offer an ability to be expanded in the layer graph. GRD files are useful for sharing *assets* when their authors do not wish to provide the source *documents* used for their authoring. They are also the input format included in games that utilize the *Graphite Renderer Core Library* to render graphical content at runtime, as well as similar applications like headless renderers on web servers and image processing pipelines.
- Window
- Main window
- Popout window
- Title bar
- Status bar
- Workspace
The part of the Graphite editor's UI that houses the *panels* in a *window*. The workspace occupies the large space below the *title bar* and above the *status bar* of the *main window*. It occupies the entirety of *popout windows* (window buttons are added in the *tab bar*).
- Workspace layout
The specific configuration of panels in the *main window* and any *popout windows*. Workspace layout presets are provided by the Graphite editor and users may customize and save their own.
- Tab bar
The bar at the top of a *panel group* which includes a clickable tab for each panel that is docked there. Each tab bar has at least one tab and one active tab.
- Active tab
The one tab in a *tab bar* that is currently active. The user can click any inactive tab to make it become the active tab. The active tab shows the *panel content* beneath it unless it is a *folded panel*.
- Folded panel
A shrunken *panel* showing only the *tab bar*. A *panel* consists of the *tab bar* and *panel body* except when the latter is folded away. The user may click the *active tab* to fold and restore a panel, however a panel cannot be folded if there are no other unfolded panels in its column.
- Panel
- Panel body
- Options bar
The bar that spans horizontally across the top of a *panel* (located under the *tab bar*) which displays options related to the *panel*.
- Viewport
The area that takes up the main space in a *panel* (located beneath the *options bar*) which displays the primary content of the *panel*.
- Toolbar
The bar that spans vertically across the left side of some *panels* (located left of the *viewport*) which displays a catalog of available items, such as document editing *tools* or common *nodes*.
- Tool
An instrument for interactively editing *documents* through a collection of related behavior. Each tool puts the editor into a mode that provides the ability to perform certain *operations* on the document interactively. Each *operation* is run based on the current context of mouse and modifier buttons, key presses, tool options, selected layers, editor state, and document state. The *operations* that get run are appended to the document history and update the underlying *layer graph* in real time.
- Canvas
The infinite coordinate system that shows the visual output of an open *document* at the current zoom level and pan position. It is drawn in the document panel's *viewport* within the area inside the scroll bars on the bottom/right edges and the *rulers* on the top/left edges. The canvas can be panned and zoomed in order to display all or part of the artwork in any *frames*. A canvas has a coordinate system spanning infinitely in all directions with an origin always located at the top left of the primary *frame*. The purpose of an infinite canvas is to offer a convenient editing experience when there is no logical edge to the artwork, for example a loosely-arranged board of logo design concepts, a mood board, or whiteboard-style notes.
- Frame
An area inside a *canvas* that provides rectangular bounds to the artwork contained within, as well as default bounds for an exported image. This is also called an "artboard" in some other software. The *crop tool* adjusts the bounds and placement of frames in the *document* and each frame is stored in a "frame list" property of the *root layer*. When there is at least one frame, the infinite *canvas* area outside any frame displays a configurable background color. Artwork can be placed outside of a frame but it will appear mostly transparent. The purpose of using one frame is to provide convenient cropping to the edges of the artwork, such as a single digital painting or photograph. The purpose of using multiple frames is to work on related artwork with separate bounds, such as the layout for a book.
- Layer graph
A (directed acyclic) graph structure composed of *layers* with *connections* between their input and output *ports*. This is commonly referred to as a "node graph" in other software, but Graphite's layer graph is more suited towards layer-based compositing compared to traditional compositor node graphs.
- Node
A definition of a *layer*. A node is a graph "operation" or "function" that receives input and generates deterministic output.
- Layer
Any instance of a *node* that lives in the *layer graph*. Layers (usually) take input data, then they transform it or synthesize new data, then they provide it as output. Layers have *properties* as well as exposed input and output *ports* for sending and receiving data.
- Root layer
- Group
- Raster
- Vector
- Mask
- Data type
- Subgraph
- Port
- Connection
- Core Libraries
- Editor Core Library
- Document Core Library
- Renderer Core Library
- Trace
- Path
- Shape