dwelle
164 lines
5.0 KiB
Plaintext
164 lines
5.0 KiB
Plaintext
# Flowchart Parser
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As mentioned in the previous section, we use [getDiagramFromText](https://github.com/mermaid-js/mermaid/blob/00d06c7282a701849793680c1e97da1cfdfcce62/packages/mermaid/src/Diagram.ts#L80) to parse the full defination and get the [Diagram](https://github.com/mermaid-js/mermaid/blob/00d06c7282a701849793680c1e97da1cfdfcce62/packages/mermaid/src/Diagram.ts#L15) json from it.
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In this section we will be diving into how the [flowchart parser](https://github.com/excalidraw/mermaid-to-excalidraw/blob/master/src/parser/flowchart.ts#L256) works behind the scenes.
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We use `diagram.parser.yy` attribute to parse the data. If you want to know more about how the `diagram.parse.yy` attribute looks like, you can check it [here](https://github.com/mermaid-js/mermaid/blob/00d06c7282a701849793680c1e97da1cfdfcce62/packages/mermaid/src/diagrams/flowchart/flowDb.js#L768), however for scope of flowchart we are using **3** APIs from this parser to compute `vertices`, `edges` and `clusters` as we need these data to transform to [ExcalidrawElementSkeleton](https://github.com/excalidraw/excalidraw/blob/master/packages/excalidraw/data/transform.ts#L133C13-L133C38).
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For computing `vertices` and `edge`s lets consider the below svg generated by mermaid
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## Computing the vertices
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We use `getVertices` API from `diagram.parse.yy` to get the vertices for a given flowchart.
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Considering the same example this is the response from the API
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```js
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{
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"start": {
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"id": "start",
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"labelType": "text",
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"domId": "flowchart-start-1414",
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"styles": [],
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"classes": [],
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"text": "start",
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"props": {}
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},
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"stop": {
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"id": "stop",
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"labelType": "text",
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"domId": "flowchart-stop-1415",
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"styles": [],
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"classes": [],
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"text": "stop",
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"props": {}
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}
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}
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```
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The dimensions and position is missing in this response and we need that to transform to [ExcalidrawElementSkeleton](https://github.com/excalidraw/excalidraw/blob/master/packages/excalidraw/data/transform.ts#L133C13-L133C38), for this we have our own parser [`parseVertex`](https://github.com/excalidraw/mermaid-to-excalidraw/blob/master/src/parseMermaid.ts#L178) which takes the above response and uses the `svg` together to compute position, dimensions and cleans up the response.
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The final output from `parseVertex` looks like :point_down:
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```js
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{
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"start": {
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"id": "start",
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"labelType": "text",
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"text": "start",
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"x": 0,
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"y": 0,
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"width": 67.796875,
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"height": 44,
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"containerStyle": {},
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"labelStyle": {}
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},
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"stop": {
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"id": "stop",
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"labelType": "text",
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"text": "stop",
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"x": 117.796875,
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"y": 0,
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"width": 62.3828125,
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"height": 44,
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"containerStyle": {},
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"labelStyle": {}
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}
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}
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```
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## Computing the edges
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The lines and arrows are considered as `edges` in mermaid as shown in the above diagram. We use `getEdges` API from `diagram.parse.yy` to get the edges for a given flowchart. Considering the same example this is the response from the API
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```js
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[
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{
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start: "start",
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end: "stop",
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type: "arrow_point",
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text: "",
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labelType: "text",
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stroke: "normal",
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length: 1,
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},
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];
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```
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Similarly here the dimensions and position is missing and we compute that from the svg. The [`parseEdge`](https://github.com/excalidraw/mermaid-to-excalidraw/blob/master/src/parseMermaid.ts#L245) takes the above response along with `svg` and computes the position, dimensions and cleans up the response.
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The final output from `parseEdge` looks like :point_down:
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```js
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[
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{
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start: "start",
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end: "stop",
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type: "arrow_point",
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text: "",
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labelType: "text",
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stroke: "normal",
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startX: 67.797,
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startY: 22,
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endX: 117.797,
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endY: 22,
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reflectionPoints: [
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{
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x: 67.797,
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y: 22,
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},
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{
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x: 117.797,
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y: 22,
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},
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],
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},
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];
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```
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## Computing the Subgraphs
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`Subgraphs` is collection of elements grouped together. The Subgraphs map to `grouping` elements in Excalidraw.
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Lets consider the below example :point_down:
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We use `getSubgraphs` API to get the subgraph data for a given flowchart. Considering the same example this is the response from the API
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```js
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[
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{
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id: "one",
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nodes: ["flowchart-a2-1399", "flowchart-a1-1400"],
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title: "one",
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classes: [],
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labelType: "text",
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},
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];
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```
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For position and dimensions we use the svg to compute. The [`parseSubgraph`](https://github.com/excalidraw/mermaid-to-excalidraw/blob/master/src/parseMermaid.ts#L139) takes the above response along with `svg` and computes the position, dimensions and cleans up the response.
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```js
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[
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{
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id: "one",
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nodes: ["flowchart-a2-1399", "flowchart-a1-1400"],
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title: "one",
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labelType: "text",
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nodeIds: ["a2", "a1"],
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x: 75.4921875,
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y: 0,
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width: 121.25,
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height: 188,
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text: "one",
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},
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];
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```
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