svg_path/marker

Marker placement helpers.

SVG markers are full rendering objects with their own viewport, reference point, units, and content. This module only covers the part supplied by path data: marker positions and path-derived orientation angles.

Types

AspectAlign

</>

Alignment used by SVG preserveAspectRatio.

pub type AspectAlign {
  XMinYMin
  XMidYMin
  XMaxYMin
  XMinYMid
  XMidYMid
  XMaxYMid
  XMinYMax
  XMidYMax
  XMaxYMax
}

Constructors

```
XMinYMin
```
```
XMidYMin
```
```
XMaxYMin
```
```
XMinYMid
```
```
XMidYMid
```
```
XMaxYMid
```
```
XMinYMax
```
```
XMidYMax
```
```
XMaxYMax
```

Error

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Errors returned while computing marker poses.

pub type Error {
  EmptySubpath
  DegenerateTangent
  PathError(svg_path.Error)
  InvalidMarkerWidth(width: Float)
  InvalidMarkerHeight(height: Float)
  InvalidStrokeWidth(width: Float)
  InvalidViewBox(view_box: svg_path.BoundingBox)
}

Constructors

```
EmptySubpath
```
The subpath has no drawable segments.
```
DegenerateTangent
```
A marker orientation could not be computed from a zero derivative.
```
PathError(svg_path.Error)
```
An underlying path operation failed.
```
InvalidMarkerWidth(width: Float)
```
Marker viewport width must be finite and greater than zero.
```
InvalidMarkerHeight(height: Float)
```
Marker viewport height must be finite and greater than zero.
```
InvalidStrokeWidth(width: Float)
```
Stroke width must be finite and greater than zero when marker units use stroke width.
```
InvalidViewBox(view_box: svg_path.BoundingBox)
```
Marker viewBox width and height must be finite and greater than zero.

MarkerKind

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Which SVG marker slot a pose belongs to.

pub type MarkerKind {
  MarkerStart
  MarkerMid
  MarkerEnd
}

Constructors

```
MarkerStart
```
```
MarkerMid
```
```
MarkerEnd
```

MarkerLayout

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Transform-only SVG marker layout inputs.

reference corresponds to SVG refX and refY. marker_width and marker_height are the marker viewport size. If view_box is Some, the marker content coordinate system is mapped into that viewport using preserve_aspect_ratio; otherwise marker content coordinates are already viewport coordinates. stroke_width is used only with StrokeWidth units.

pub type MarkerLayout {
  MarkerLayout(
    reference: svg_path.Point,
    marker_width: Float,
    marker_height: Float,
    marker_units: MarkerUnits,
    stroke_width: Float,
    view_box: option.Option(svg_path.BoundingBox),
    preserve_aspect_ratio: PreserveAspectRatio,
  )
}

Constructors

MarkerLayout(
  reference: svg_path.Point,
  marker_width: Float,
  marker_height: Float,
  marker_units: MarkerUnits,
  stroke_width: Float,
  view_box: option.Option(svg_path.BoundingBox),
  preserve_aspect_ratio: PreserveAspectRatio,
)

MarkerOrient

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SVG-style marker orientation policy.

pub type MarkerOrient {
  Auto
  AutoStartReverse
  Fixed(Float)
}

Constructors

```
Auto
```
Use path-derived marker angles.
```
AutoStartReverse
```
Use path-derived marker angles, but rotate the start marker by 180 degrees.
```
Fixed(Float)
```
Use one fixed absolute angle for every marker.

MarkerPose

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A marker position and absolute orientation angle in degrees.

pub type MarkerPose {
  MarkerPose(
    kind: MarkerKind,
    point: svg_path.Point,
    angle: Float,
  )
}

Constructors

MarkerPose(kind: MarkerKind, point: svg_path.Point, angle: Float)

MarkerUnits

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How marker viewport units relate to the stroked path.

pub type MarkerUnits {
  StrokeWidth
  UserSpaceOnUse
}

Constructors

```
StrokeWidth
```
Marker viewport units are multiplied by the path stroke width.
```
UserSpaceOnUse
```
Marker viewport units are ordinary user-space units.

PreserveAspectRatio

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SVG preserveAspectRatio behavior for marker viewBox fitting.

pub type PreserveAspectRatio {
  Stretch
  Meet(AspectAlign)
  Slice(AspectAlign)
}

Constructors

```
Stretch
```
Scale x and y independently so the viewBox exactly fills the viewport.
```
Meet(AspectAlign)
```
Use uniform scale so the whole viewBox fits inside the viewport.
```
Slice(AspectAlign)
```
Use uniform scale so the viewBox covers the viewport.

Values

layout_transform

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pub fn layout_transform(
  point point: svg_path.Point,
  angle angle: Float,
  layout layout: MarkerLayout,
) -> Result(transform.Matrix, Error)

Return a full marker-content transform at point and angle.

pose_layout_transform

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pub fn pose_layout_transform(
  pose: MarkerPose,
  layout layout: MarkerLayout,
) -> Result(transform.Matrix, Error)

Return a full marker-content transform for a pose and marker layout.

This computes the transform-only portion of SVG marker placement. It maps marker content coordinates through optional viewBox fitting, optional strokeWidth unit scaling, reference-point placement, pose rotation, and pose translation.

pose_transform

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pub fn pose_transform(pose: MarkerPose) -> transform.Matrix

Return a transform that places marker-local coordinates at a pose.

The returned matrix rotates marker-local coordinates by the pose angle, then translates marker-local (0, 0) to the pose point.

pose_transform_with_reference

</>

pub fn pose_transform_with_reference(
  pose: MarkerPose,
  reference reference: svg_path.Point,
) -> transform.Matrix

Return a transform that places a marker-local reference point at a pose.

The returned matrix rotates marker-local coordinates by the pose angle and translates them so reference lands on the pose point. This corresponds to the geometric part of SVG’s refX and refY marker reference point.

subpath_poses

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pub fn subpath_poses(
  subpath: svg_path.Subpath,
  orient orient: MarkerOrient,
) -> Result(List(MarkerPose), Error)

Return marker poses for one subpath.

MarkerStart is placed at the first segment start, MarkerEnd at the last segment end, and MarkerMid at each join between adjacent segments. For Auto, open-subpath start and end markers use the outgoing and incoming segment directions respectively. Mid markers and closed-subpath start/end markers use the angle bisector of the incoming and outgoing directions. If that bisector is degenerate because the two directions are exactly opposite, the incoming direction is used.

transform

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pub fn transform(
  point point: svg_path.Point,
  angle angle: Float,
) -> transform.Matrix

Return a transform that places marker-local coordinates at point.

The returned matrix rotates marker-local coordinates by angle, then translates marker-local (0, 0) to point.

transform_with_reference

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pub fn transform_with_reference(
  point point: svg_path.Point,
  angle angle: Float,
  reference reference: svg_path.Point,
) -> transform.Matrix

Return a transform that places a marker-local reference point at point.