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102 lines
3.3 KiB
Go
102 lines
3.3 KiB
Go
// Package shapes2d exchanges local contours without a dependency on a physics
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// solver, Scene, the renderer or the editor. Providers belong to one world.
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package shapes2d
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import (
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"errors"
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"aego/core/ids"
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"aego/core/mathx"
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)
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const (
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ServiceID = "shapes2d.geometry"
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// These bounds apply to one reusable extraction buffer. A consumer may set
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// lower Limits; exceeding a bound returns an error without partial append.
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MaxContourPoints = 256
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MaxContours = 4096
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MaxPoints = 256 * 1024
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)
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var (
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ErrClosed = errors.New("shape provider is closed")
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ErrMissingNode = errors.New("shape source node does not exist")
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ErrMissingShape = errors.New("selected shape does not exist on the source node")
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ErrSpace = errors.New("shape source must be in 2D space")
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ErrBudget = errors.New("shape geometry exceeds its bounded buffer budget")
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ErrBuffer = errors.New("shape geometry needs an output buffer")
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)
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// ID remains stable when other shapes are inserted or removed; Part is a provider-defined slot, not a result index. IDs and Node IDs are scoped to the provider's world.
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type ID struct {
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Node ids.NodeID
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Part uint32
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}
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type Contour struct {
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ID ID
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Owner ids.NodeID // apply this node's presentation transform exactly once
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Key string // stable provider key, suitable for an explicit selection
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Revision uint64 // changes with local geometry, independently of transforms
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First int
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Count int
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Closed bool
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}
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type Limits struct {
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Contours int
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Points int
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}
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// Buffer owns its points; copied geometry never aliases a component, provider cache or physics world, and contour offsets survive Points reallocation.
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// Results remain valid until the caller resets or mutates Buffer.
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type Buffer struct {
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Contours []Contour
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Points []mathx.Vec2
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Limits Limits
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}
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func (b *Buffer) Reset() {
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clear(b.Contours)
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b.Contours = b.Contours[:0]
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b.Points = b.Points[:0]
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}
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// Vertices returns a view into the caller-owned extraction buffer.
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func (b *Buffer) Vertices(c Contour) []mathx.Vec2 {
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if c.First < 0 || c.Count < 0 || c.First > len(b.Points) || c.Count > len(b.Points)-c.First {
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return nil
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}
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return b.Points[c.First : c.First+c.Count]
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}
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// Append copies an already validated contour. It checks sizes only; validating
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// topology belongs at a geometry revision boundary, not in a warmed draw loop.
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func (b *Buffer) Append(c Contour, points []mathx.Vec2) error {
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if b == nil {
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return ErrBuffer
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}
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contours, count := b.Limits.Contours, b.Limits.Points
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if contours <= 0 || contours > MaxContours {
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contours = MaxContours
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}
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if count <= 0 || count > MaxPoints {
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count = MaxPoints
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}
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if len(points) > MaxContourPoints || len(points) < 2 || c.Closed && len(points) < 3 ||
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len(b.Contours) >= contours || len(points) > count-len(b.Points) {
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return ErrBudget
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}
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c.First, c.Count = len(b.Points), len(points)
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b.Points = append(b.Points, points...)
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b.Contours = append(b.Contours, c)
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return nil
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}
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type Provider interface {
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// Append copies node-local geometry with collider offsets but no world/body transform; an empty key selects all shapes in stable provider order.
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// Disabled nodes append nothing without error; errors leave dst unchanged, and missing nodes/explicit keys remain diagnosable.
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Append(node ids.NodeID, key string, dst *Buffer) error
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}
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