comments, cleanups

engine/debug.go

@@ -40,8 +40,9 @@ func (d *DebugToast) Draw(screen *ebiten.Image, _ *ebiten.DrawImageOptions) {
 	ebitenutil.DebugPrintAt(screen, d.Text, d.Pos.X, d.Pos.Y)
 }
 
-func (DebugToast) DrawAfter(x Drawer) bool  { return x != Tombstone{} }
+// Draw last, but sort tombstones later.
-func (DebugToast) DrawBefore(x Drawer) bool { return x == Tombstone{} }
+func (DebugToast) DrawAfter(x Drawer) bool  { return x != tombstone{} }
+func (DebugToast) DrawBefore(x Drawer) bool { return x == tombstone{} }
 
 func (d *DebugToast) Toast(text string) {
 	d.Text = text
@@ -65,5 +66,6 @@ func (p PerfDisplay) Draw(screen *ebiten.Image, _ *ebiten.DrawImageOptions) {
 	ebitenutil.DebugPrint(screen, fmt.Sprintf("TPS: %0.2f  FPS: %0.2f", ebiten.CurrentTPS(), ebiten.CurrentFPS()))
 }
 
-func (PerfDisplay) DrawAfter(x Drawer) bool  { return x != Tombstone{} }
+// Draw last, but sort tombstones later.
-func (PerfDisplay) DrawBefore(x Drawer) bool { return x == Tombstone{} }
+func (PerfDisplay) DrawAfter(x Drawer) bool  { return x != tombstone{} }
+func (PerfDisplay) DrawBefore(x Drawer) bool { return x == tombstone{} }

engine/game.go

@@ -99,7 +99,7 @@ func (g *Game) Draw(screen *ebiten.Image) {
 			}
 			// p is not hidden, so compute its cumulative opts.
 			if tf, ok := p.(Transformer); ok {
-				st.opts = ConcatOpts(tf.Transform(), st.opts)
+				st.opts = concatOpts(tf.Transform(), st.opts)
 			}
 			accum[p] = st
 		}
@@ -176,11 +176,10 @@ func (g *Game) Update() error {
 	}
 
 	// Sort the draw list (on every frame - this isn't as bad as it sounds)
-	//sort.Stable(g.drawList)
+	sort.Stable(g.drawList)
-	sort.Sort(g.drawList)
 	// Truncate tombstones from the end.
 	for i := len(g.drawList) - 1; i >= 0; i-- {
-		if g.drawList[i] == (Tombstone{}) {
+		if g.drawList[i] == (tombstone{}) {
 			g.drawList = g.drawList[:i]
 		}
 	}
@@ -408,7 +407,7 @@ func (g *Game) unregister(component interface{}) {
 	// unregister from g.drawList
 	for i, d := range g.drawList {
 		if d == component {
-			g.drawList[i] = Tombstone{}
+			g.drawList[i] = tombstone{}
 		}
 	}
 
@@ -425,14 +424,14 @@ type abKey struct {
 	behaviour reflect.Type
 }
 
-var _ Drawer = Tombstone{}
+var _ Drawer = tombstone{}
 
-type Tombstone struct{}
+type tombstone struct{}
 
-func (Tombstone) Draw(*ebiten.Image, *ebiten.DrawImageOptions) {}
+func (tombstone) Draw(*ebiten.Image, *ebiten.DrawImageOptions) {}
 
-func (Tombstone) DrawAfter(x Drawer) bool { return x != Tombstone{} }
+func (tombstone) DrawAfter(x Drawer) bool { return x != tombstone{} }
-func (Tombstone) DrawBefore(Drawer) bool  { return false }
+func (tombstone) DrawBefore(Drawer) bool  { return false }
 
 type drawList []Drawer
 
@@ -442,8 +441,8 @@ func (d drawList) Less(i, j int) bool {
 func (d drawList) Len() int      { return len(d) }
 func (d drawList) Swap(i, j int) { d[i], d[j] = d[j], d[i] }
 
-// ConcatOpts returns the combined options (as though a was applied and then b).
+// concatOpts returns the combined options (as though a was applied and then b).
-func ConcatOpts(a, b ebiten.DrawImageOptions) ebiten.DrawImageOptions {
+func concatOpts(a, b ebiten.DrawImageOptions) ebiten.DrawImageOptions {
 	a.ColorM.Concat(b.ColorM)
 	a.GeoM.Concat(b.GeoM)
 	if b.CompositeMode != 0 {

engine/prisms.go

@@ -46,6 +46,7 @@ type PrismMap struct {
 
 	game      *Game
 	pwinverse geom.RatMatrix3
+	topext    [4]image.Point
 }
 
 // CollidesWith checks if the box collides with any prism.
@@ -106,6 +107,7 @@ func (m *PrismMap) Prepare(g *Game) error {
 		p.pos = m.PosToWorld.Apply(v)
 		p.m = m
 	}
+	m.topext = geom.PolygonExtrema(m.PrismTop)
 	return nil
 }
 
@@ -148,6 +150,7 @@ func (p *Prism) DrawAfter(x Drawer) bool {
 	pb := p.BoundingBox()
 	switch d := x.(type) {
 	case *Prism:
+		// Fast path for other prisms
 		if p.pos.Z == d.pos.Z {
 			return p.pos.Y < d.pos.Y
 		}
@@ -155,34 +158,23 @@ func (p *Prism) DrawAfter(x Drawer) bool {
 	case BoundingBoxer:
 		xb := d.BoundingBox()
 		if pb.Max.Z <= xb.Min.Z { // p is behind x
-			/*if _, ok := x.(*Sprite); ok && pb.Min.Y < 0 {
-				log.Print("p.DrawAfter: prism is behind sprite")
-			}*/
 			return false
 		}
 		if pb.Min.Z >= xb.Max.Z { // p is in front of x
-			/*if _, ok := x.(*Sprite); ok && pb.Min.Y < 0 {
-				log.Print("p.DrawAfter: prism is in front of sprite")
-			}*/
 			return true
 		}
 		if pb.Min.Y >= xb.Max.Y { // p is below x
-			/*if _, ok := x.(*Sprite); ok && pb.Min.Y < 0 {
-				log.Print("p.DrawAfter: prism is below sprite")
-			}*/
 			return false
 		}
 		if pb.Max.Y <= xb.Min.Y { // p is above x
-			/*if _, ok := x.(*Sprite); ok && pb.Min.Y < 0 {
-				log.Print("p.DrawAfter: prism is above sprite")
-			}*/
 			return true
 		}
+
 		// The hexagon special
-		if pb.Min.Z+8 <= xb.Min.Z {
+		if pb.Min.Z+8 <= xb.Min.Z { // x is in front of the front half of p
 			return false
 		}
-		if pb.Min.Z+8 >= xb.Max.Z {
+		if pb.Min.Z+8 >= xb.Max.Z { // x is behind the front half of p
 			return true
 		}
 
@@ -197,6 +189,7 @@ func (p *Prism) DrawBefore(x Drawer) bool {
 	pb := p.BoundingBox()
 	switch d := x.(type) {
 	case *Prism:
+		// Fast path for other prisms
 		if p.pos.Z == d.pos.Z {
 			return p.pos.Y > d.pos.Y
 		}
@@ -204,34 +197,22 @@ func (p *Prism) DrawBefore(x Drawer) bool {
 	case BoundingBoxer:
 		xb := d.BoundingBox()
 		if pb.Min.Z >= xb.Max.Z { // p is in front of x
-			/*if _, ok := x.(*Sprite); ok && pb.Min.Y < 0 {
-				log.Print("p.DrawBefore: prism is in front of sprite")
-			}*/
 			return false
 		}
 		if pb.Max.Z <= xb.Min.Z { // p is behind x
-			/*if _, ok := x.(*Sprite); ok && pb.Min.Y < 0 {
-				log.Print("p.DrawBefore: prism is behind sprite")
-			}*/
 			return true
 		}
 		if pb.Max.Y <= xb.Min.Y { // p is above x
-			/*if pb.Min.Y < 0 {
-				log.Print("p.DrawBefore: prism is above sprite")
-			}*/
 			return false
 		}
 		if pb.Min.Y >= xb.Max.Y { // p is below x
-			/*if pb.Min.Y < 0 {
-				log.Print("p.DrawBefore: prism is below sprite")
-			}*/
 			return true
 		}
 		// The hexagon special
-		if pb.Min.Z+8 >= xb.Max.Z {
+		if pb.Min.Z+8 >= xb.Max.Z { // x is behind the front half of p
 			return false
 		}
-		if pb.Min.Z+8 <= xb.Min.Z {
+		if pb.Min.Z+8 <= xb.Min.Z { // x is in front of the front half of p
 			return true
 		}
 	case zpositioner:

engine/sprite.go

@@ -46,27 +46,15 @@ func (s *Sprite) DrawAfter(x Drawer) bool {
 	case BoundingBoxer:
 		xb := d.BoundingBox()
 		if sb.Max.Z <= xb.Min.Z { // s is behind x
-			/*if xb.Min.Y < 0 {
-				log.Print("s.DrawAfter: sprite is behind prism")
-			}*/
 			return false
 		}
 		if sb.Min.Z >= xb.Max.Z { // s is in front of x
-			/*if xb.Min.Y < 0 {
-				log.Print("s.DrawAfter: sprite is in front of prism")
-			}*/
 			return true
 		}
 		if sb.Min.Y >= xb.Max.Y { // s is below x
-			/*if xb.Min.Y < 0 {
-				log.Print("s.DrawAfter: sprite is below prism")
-			}*/
 			return false
 		}
 		if sb.Max.Y <= xb.Min.Y { // s is above x
-			/*if xb.Min.Y < 0 {
-				log.Print("s.DrawAfter: sprite is above prism")
-			}*/
 			return true
 		}
 	case zpositioner:
@@ -82,27 +70,15 @@ func (s *Sprite) DrawBefore(x Drawer) bool {
 	case BoundingBoxer:
 		xb := d.BoundingBox()
 		if sb.Min.Z >= xb.Max.Z { // s is in front of x
-			/*if xb.Min.Y < 0 {
-				log.Print("s.DrawBefore: sprite is in front of prism")
-			}*/
 			return false
 		}
 		if sb.Max.Z <= xb.Min.Z { // s is behind x
-			/*if xb.Min.Y < 0 {
-				log.Print("s.DrawBefore: sprite is behind prism")
-			}*/
 			return true
 		}
 		if sb.Max.Y <= xb.Min.Y { // s is above x
-			/*if xb.Min.Y < 0 {
-				log.Print("s.DrawBefore: sprite is above prism")
-			}*/
 			return false
 		}
 		if sb.Min.Y >= xb.Max.Y { // s is below x
-			/*if xb.Min.Y < 0 {
-				log.Print("s.DrawBefore: sprite is below prism")
-			}*/
 			return true
 		}
 	case zpositioner:

geom/polygon.go

@@ -5,9 +5,18 @@ import (
 	"math"
 )
 
-// PolygonExtrema returns the most northerly, easterly, southerly, and westerly
+const (
-// points (north is in the -Y direction, east is in the +X direction).
+	East = iota
-func PolygonExtrema(polygon []image.Point) (e, n, w, s image.Point) {
+	North
+	West
+	South
+)
+
+// PolygonExtrema returns the most easterly, northerly, westerly, and southerly
+// points (north is in the -Y direction, east is in the +X direction, etc). If
+// there are multiple points furthest in any direction, the first one is used.
+func PolygonExtrema(polygon []image.Point) [4]image.Point {
+	var e, n, w, s image.Point
 	e.X = math.MinInt
 	n.Y = math.MaxInt
 	w.X = math.MaxInt
@@ -26,7 +35,7 @@ func PolygonExtrema(polygon []image.Point) (e, n, w, s image.Point) {
 			n = p
 		}
 	}
-	return e, n, w, s
+	return [4]image.Point{East: e, North: n, West: w, South: s}
 }
 
 // PolygonContains reports if a convex polygon contains a point. The polygon