96 lines
4.7 KiB
Text
96 lines
4.7 KiB
Text
---
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title: sa
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---
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The `sa` macro will create seam allowance paths.
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Unlike the core [`Path.join()`](/reference/api/path/join) and
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[`Path.offset()`](/reference/api/path/offset) functions, the
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`sa` macro can extend line ends to meet in a sharp corner and
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will automatically trim useless path ends when adjacent paths
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in the array are intersecting.
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:::note
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##### Not a core-plugins macro
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The `sa` macro is not provided by the [core plugins](/reference/plugins/core),
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so you need to load the [path-utils plugin](/reference/plugins/path-utils)
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explicitly if you want to use it.
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:::
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## Signature
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```js
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macro('sa', {
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Array paths,
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number limit,
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string mode,
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string class
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})
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```
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## Example
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<Example caption="An example of the sa macro">
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```js
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;({ Point, points, Path, paths, macro, part }) => {
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paths.outline = new Path()
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.move(new Point(10, 30))
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.line(new Point(30, 30))
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.line(new Point(30, 50))
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.line(new Point(50, 50))
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.line(new Point(50, 70))
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.line(new Point(70, 70))
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.curve(new Point(55, 15), new Point(55, 15), new Point(30, 0))
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paths.outline2 = new Path().move(new Point(30, 0)).line(new Point(10, 30))
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paths.sa = macro('sa', {
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paths: ['outline', { p: 'outline2', offset: 30 }],
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sa: 10,
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}).setClass('stroke-sm mark dotted')
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paths.halfCircle = new Path().move(new Point(100, 0)).circleSegment(37, new Point(200, 0)).hide()
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paths.halfCircleClosed = paths.halfCircle.clone().line(new Point(200, 0)).unhide().close()
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paths.halfCircleSa = macro('sa', {
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paths: ['halfCircle', null],
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sa: 10,
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}).setClass('stroke-sm mark dotted')
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return part
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}
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```
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</Example>
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## Configuration
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| Property | Default | Type | Description |
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| -------: | ---------------- | -------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `paths` | | `array` | An array of paths. You can use path names in the `paths` array or reference `Path` objects directly, or insert `null` elements to create gaps. You can also override offset and visibility for individual paths in the same way as with the `offset` macro. |
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| `mode` | `'corner'` | `string` | Mode for joining paths. Either `'corner'` or `'cut'`. `'cut'` will join the paths directly (like `Path.join()`) without extending the corners. |
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| `limit` | `null` | `number` | Allows limiting the length of extended path corners in `'corner'` mode. Prevents overly long joins on very sharp angles. Ignored if `null` or `false`. |
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| `sa` | (seam allowance) | `number` | Allows you to override the seam allowance used for this macro. Defaults to the standard seam allowance (`sa` parameter in draft function). |
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| `class` | `'sa'` | `string` | CSS class that is automatically applied to the resulting path. |
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## Notes
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The `sa` macro accepts an array of `Path` objects
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(either names in the `paths` array or direct references to `Path` objects).
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This array can contain `null` values to create gaps (e.g. for cuts on the fold or for other sections that don't need seam allowance).
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By default, the `sa` macro will sa the paths in a circular fashion, joining the end
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of the last path in the array to the start of the first path, creating a full outline.
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If this is not desired, insert `null` elements where you want to create gaps.
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You can optionally override the offset and invisibility for individual paths.
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To do so, insert an object literal like `{p: 'somePath', offset: 30}` or `{p: ['path1', 'path2'], offset: sa * 3, hidden: true}` into the `paths` array.
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You can use `offset: 0` to include paths which have already build-in the seam allowance (e.g. the result of the `hem` macro).
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You can use `hidden: true` to hide path segments from the output, but still build corner joins as if they were there.
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This can be used for cut-on-fold lines, where no seam allowance is needed.
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