__useInternal() in Grida codebase.

In this article, we will review the __useInternal() function in Grida codebase.


function __useInternal() {
  const state = useContext(DocumentContext);
  if (!state) {
    throw new Error(
      "useDocument must be used within a StandaloneDocumentEditor"
    );
  }
 
  const dispatch = __useDispatch();
 
  return useMemo(() => [state, dispatch] as const, [state, dispatch]);
}

How did I come across this function? In the previous articles, I wrote Toolbar component and a function called setCursorMode.

In the useEventTarget function, state and dispatch are destructured from this function, __useInternal().


export function useEventTarget() {
  const [state, dispatch] = __useInternal();

DocumentContext

DocumentContext is created at line number 41 in provider.tsx.


const DocumentContext = createContext<IDocumentEditorState | null>(null);

DocumentContext.Provider

You will find DocumentContext.Provider in StandaloneDocumentEditor component at line 102.


return (
    <DocumentContext.Provider value={state}>
      <DocumentDispatcherContext.Provider value={__dispatch}>
        <ProgramDataContextHost>
          <DataProvider data={{ props: shallowRootProps }}>
            <EditorGoogleFontsManager>
              {/*  */}
              {children}
            </EditorGoogleFontsManager>
          </DataProvider>
        </ProgramDataContextHost>
      </DocumentDispatcherContext.Provider>
    </DocumentContext.Provider>
  );

This is where value is initialised to state.

state

The below code is picked from line 71 in provider.tsx


const state = useMemo(
  () => initDocumentEditorState({ ...initial, editable, debug }),
  [initial, editable, debug]
);

Let’s just follow along the code as this is about state that used in the canvas. I would find out how initDocumentEditorState looks like.

initDocumentEditorState

This function is defined in grida-react-canvas/state.ts at line 600


export function initDocumentEditorState({
  debug,
  ...init
}: Omit<IDocumentEditorInit, "debug"> & {
  debug?: boolean;
}): IDocumentEditorState {
  const s = new document.DocumentState(init.document);
 
  // console.log("i", init["transform"]);
 
  return {
    transform: cmath.transform.identity,
    debug: debug ?? false,
    selection: [],
    hovered_node_id: null,
    hovered_vertex_idx: null,
    pointer: {
      position: cmath.vector2.zero,
    },
    history: {
      future: [],
      past: [],
    },
    gesture: { type: "idle" },
    gesture_modifiers: {
      translate_with_hierarchy_change: "on",
      translate_with_clone: "off",
      tarnslate_with_axis_lock: "off",
      transform_with_center_origin: "off",
      transform_with_preserve_aspect_ratio: "off",
      rotate_with_quantize: "off",
    },
    document_ctx: document.Context.from(init.document).snapshot(),
    // history: initialHistoryState(init),
    surface_raycast_targeting: DEFAULT_RAY_TARGETING,
    surface_measurement_targeting: "off",
    surface_measurement_targeting_locked: false,
    surface_raycast_detected_node_ids: [],
    googlefonts: s.fonts().map((family) => ({ family })),
    cursor_mode: { type: "cursor" },
    ...init,
  };
}

This function is used in playground.tsx

playground.tsx


const [state, dispatch] = useReducer(
    standaloneDocumentReducer,
    initDocumentEditorState({
      editable: true,
      debug: pref.debug,
      document: {
        nodes: {
          root: {
            id: "root",
            name: "root",
            active: true,
            locked: false,
            type: "container",
            children: [],
            width: 800,
            height: 600,
            position: "relative",
            style: {},
            opacity: 1,
            zIndex: 0,
            rotation: 0,
            expanded: false,
            cornerRadius: 0,
            padding: 0,
            layout: "flow",
            direction: "horizontal",
            mainAxisAlignment: "start",
            crossAxisAlignment: "start",
            mainAxisGap: 0,
            crossAxisGap: 0,
          },
        },
        root_id: "root",
      },
    })

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