change how byAB works

engine/actor.go

@@ -2,6 +2,8 @@ package engine
 
 import (
 	"encoding/gob"
+	"errors"
+	"log"
 
 	"drjosh.dev/gurgle/geom"
 )
@@ -12,6 +14,8 @@ var _ interface {
 	Prepper
 } = &Actor{}
 
+var errCollision = errors.New("collision detected")
+
 func init() {
 	gob.Register(&Actor{})
 }
@@ -39,12 +43,17 @@ func (a *Actor) BoundingBox() geom.Box {
 func (a *Actor) CollidesAt(p geom.Int3) bool {
 	bounds := a.Bounds.Add(p)
 	cd := a.game.Component(a.CollisionDomain)
-	for c := range a.game.Query(cd, ColliderType) {
-		if c.(Collider).CollidesWith(bounds) {
-			return true
-		}
+	if cd == nil {
+		log.Printf("collision domain %q not found in game", a.CollisionDomain)
+		return false
 	}
-	return false
+	return errCollision == a.game.Query(cd, ColliderType, func(c interface{}) error {
+		log.Printf("checking for collision with %v", c)
+		if c.(Collider).CollidesWith(bounds) {
+			return errCollision
+		}
+		return nil
+	})
 }
 
 // MoveX moves the actor x units in world space. It takes Game.VoxelScale into

engine/drawdag.go

@@ -154,15 +154,15 @@ func (d *DrawDAG) Update() error {
 // descendants of a different DrawManager.
 func (d *DrawDAG) Register(component, _ interface{}) error {
 	// *Don't* register the component if it is inside a descendant DrawManager.
-	// These queries work because component should be registered in game before
+	// Using Parent works because component should be registered in game before
 	// this call.
-	for dm := range d.game.Query(d, DrawManagerType) {
-		if dm == d {
-			continue
-		}
-		dbs := d.game.Query(dm, DrawBoxerType)
-		if _, found := dbs[component]; found {
-			return nil
+	for p := component; p != d && p != nil; p = d.game.Parent(p) {
+		if _, isDM := p.(DrawManager); isDM {
+			if p == d {
+				break
+			} else {
+				return nil
+			}
 		}
 	}
 	// Register db, and then subcomponents recursively.

engine/game.go

@@ -8,6 +8,7 @@ import (
 	"io/fs"
 	"log"
 	"reflect"
+	"strings"
 	"sync"
 	"time"
 
@@ -33,9 +34,6 @@ func init() {
 	gob.Register(&Game{})
 }
 
-// ComponentSet is a set of components.
-type ComponentSet map[interface{}]struct{}
-
 // Game implements the ebiten methods using a collection of components. One
 // component must be the designated root component.
 type Game struct {
@@ -48,7 +46,7 @@ type Game struct {
 
 	dbmu     sync.RWMutex
 	byID     map[string]Identifier        // Named components by ID
-	byAB     map[abKey]ComponentSet       // Ancestor/behaviour index
+	byAB     map[abKey]ComponentSet       // paths matching interface
 	parent   map[interface{}]interface{}  // parent[x] is parent of x
 	children map[interface{}]ComponentSet // children[x] are chilren of x
 }
@@ -101,14 +99,15 @@ func (g *Game) Component(id string) Identifier {
 }
 
 // Parent returns the parent of a given component, or nil if there is none.
-// This only returns sensible values for registered components (e.g. after
-// LoadAndPrepare).
+// This only returns sensible values for registered components.
 func (g *Game) Parent(c interface{}) interface{} {
 	g.dbmu.RLock()
 	defer g.dbmu.RUnlock()
 	return g.parent[c]
 }
 
+// Children returns the direct subcomponents of the given component, or nil if
+// there are none. This only returns sensible values for registered components.
 func (g *Game) Children(c interface{}) ComponentSet {
 	g.dbmu.RLock()
 	defer g.dbmu.RUnlock()
@@ -164,10 +163,24 @@ func (g *Game) ReversePath(component interface{}) []interface{} {
 // Query looks for components having both a given ancestor and implementing
 // a given behaviour (see Behaviors in interface.go). This only returns sensible
 // values after LoadAndPrepare. Note that every component is its own ancestor.
-func (g *Game) Query(ancestor interface{}, behaviour reflect.Type) ComponentSet {
+func (g *Game) Query(ancestor interface{}, behaviour reflect.Type, visit func(interface{}) error) error {
+	// NB: per the godoc, do not use RLock for recursive read locking.
 	g.dbmu.RLock()
 	defer g.dbmu.RUnlock()
-	return g.byAB[abKey{ancestor, behaviour}]
+	return g.queryRecursive(ancestor, behaviour, visit)
+}
+
+// Post-order visit p and descendants of p having behaviour b.
+func (g *Game) queryRecursive(p interface{}, b reflect.Type, v func(interface{}) error) error {
+	for x := range g.byAB[abKey{p, b}] {
+		if err := g.queryRecursive(x, b, v); err != nil {
+			return err
+		}
+	}
+	if reflect.TypeOf(p).Implements(b) {
+		return v(p)
+	}
+	return nil
 }
 
 // Scan visits g.Root.
@@ -301,13 +314,16 @@ func (g *Game) registerOne(component, parent interface{}) error {
 		if !ct.Implements(b) {
 			continue
 		}
-		// TODO: better than O(len(path)^2) time and memory?
-		for p := component; p != nil; p = g.parent[p] {
+		for c, p := component, g.parent[component]; p != nil; c, p = p, g.parent[p] {
 			k := abKey{p, b}
 			if g.byAB[k] == nil {
-				g.byAB[k] = make(ComponentSet)
+				g.byAB[k] = ComponentSet{c: {}}
+				continue
 			}
-			g.byAB[k][component] = struct{}{}
+			if _, exists := g.byAB[k][c]; exists {
+				break
+			}
+			g.byAB[k][c] = struct{}{}
 		}
 	}
 	return nil
@@ -336,15 +352,17 @@ func (g *Game) unregisterRecursive(component interface{}) {
 }
 
 func (g *Game) unregisterOne(component interface{}) {
-	// unregister from g.byAB, using g.par to trace the path
+	// unregister from g.byAB
 	ct := reflect.TypeOf(component)
 	for _, b := range Behaviours {
 		if !ct.Implements(b) {
 			continue
 		}
-		for p := component; p != nil; p = g.parent[p] {
-			if k := (abKey{p, b}); g.byAB[k] != nil {
-				delete(g.byAB[k], component)
+		for c, p := component, g.parent[component]; p != nil; c, p = p, g.parent[p] {
+			k := abKey{p, b}
+			delete(g.byAB[k], c)
+			if len(g.byAB[k]) > 0 {
+				break
 			}
 		}
 	}
@@ -363,11 +381,29 @@ func (g *Game) String() string { return "Game" }
 
 // --------- Helper stuff ---------
 
+// ComponentSet is a set of components.
+type ComponentSet map[interface{}]struct{}
+
+func (c ComponentSet) String() string {
+	var b strings.Builder
+	b.WriteString("{")
+	for x := range c {
+		fmt.Fprint(&b, " ", x)
+	}
+	b.WriteString(" }")
+	return b.String()
+}
+
+// abKey is the key type for game.byAB.
 type abKey struct {
-	ancestor  interface{}
+	parent    interface{}
 	behaviour reflect.Type
 }
 
+func (a abKey) String() string {
+	return fmt.Sprintf("(%v %s)", a.parent, a.behaviour.Name())
+}
+
 // concatOpts returns the combined options (as though a was applied and then b).
 func concatOpts(a, b ebiten.DrawImageOptions) ebiten.DrawImageOptions {
 	a.ColorM.Concat(b.ColorM)

engine/repl.go

@@ -128,6 +128,7 @@ func (g *Game) cmdQuery(dst io.Writer, argv []string) {
 	}
 	if behaviour == nil {
 		fmt.Fprintf(dst, "Unknown behaviour %q\n", argv[1])
+		return
 	}
 
 	var ancestor interface{} = g
@@ -135,23 +136,24 @@ func (g *Game) cmdQuery(dst io.Writer, argv []string) {
 		c := g.Component(argv[2])
 		if c == nil {
 			fmt.Fprintf(dst, "Component %q not found\n", argv[2])
+			return
 		}
 		ancestor = c
 	}
 
-	x := g.Query(ancestor, behaviour)
-	if len(x) == 0 {
-		fmt.Fprintln(dst, "No results")
-		return
-	}
-
-	for c := range x {
+	noResults := true
+	g.Query(ancestor, behaviour, func(c interface{}) error {
+		noResults = false
 		i, ok := c.(Identifier)
 		if ok {
 			fmt.Fprintf(dst, "%T %q\n", c, i.Ident())
 		} else {
 			fmt.Fprintf(dst, "%T\n", c)
 		}
+		return nil
+	})
+	if noResults {
+		fmt.Fprintln(dst, "No results")
 	}
 }