From 46c6a72fddff78eb1292ab5bc1da6c2adb3c12b9 Mon Sep 17 00:00:00 2001
From: Josh Deprez <DrJosh9000@users.noreply.github.com>
Date: Tue, 31 Aug 2021 22:05:21 +1000
Subject: [PATCH] game does drawing

---
 engine/camera.go    | 11 ++++++++
 engine/game.go      | 65 ++++++++++++++++++++++++++-------------------
 engine/interface.go |  1 +
 engine/scene.go     | 10 ++++++-
 engine/sceneref.go  |  3 +++
 5 files changed, 62 insertions(+), 28 deletions(-)

diff --git a/engine/camera.go b/engine/camera.go
index 33463e6..2f053f5 100644
--- a/engine/camera.go
+++ b/engine/camera.go
@@ -11,6 +11,7 @@ import (
 var _ interface {
 	Identifier
 	Prepper
+	Transformer
 } = &Camera{}
 
 func init() {
@@ -37,3 +38,13 @@ func (c *Camera) Prepare(game *Game) error {
 	c.game = game
 	return nil
 }
+
+// Transform returns the camera transform.
+func (c *Camera) Transform() ebiten.DrawImageOptions {
+	var opts ebiten.DrawImageOptions
+	opts.GeoM.Translate(float2(c.Centre.Mul(-1)))
+	opts.GeoM.Scale(c.Zoom, c.Zoom)
+	opts.GeoM.Rotate(c.Rotation)
+	opts.GeoM.Translate(float64(c.game.ScreenWidth/2), float64(c.game.ScreenHeight/2))
+	return opts
+}
diff --git a/engine/game.go b/engine/game.go
index 906eb5f..ab46b18 100644
--- a/engine/game.go
+++ b/engine/game.go
@@ -13,7 +13,7 @@ import (
 	"github.com/hajimehoshi/ebiten/v2"
 )
 
-const gameDoesEverything = false
+const gameDoesEverything = true
 
 var _ interface {
 	Disabler
@@ -68,60 +68,71 @@ func (d drawers) Less(i, j int) bool { return d[i].DrawOrder() < d[j].DrawOrder(
 func (d drawers) Len() int           { return len(d) }
 func (d drawers) Swap(i, j int)      { d[i], d[j] = d[j], d[i] }
 
+func concatOpts(a, b ebiten.DrawImageOptions) ebiten.DrawImageOptions {
+	a.ColorM.Concat(b.ColorM)
+	a.GeoM.Concat(b.GeoM)
+	a.CompositeMode = b.CompositeMode
+	a.Filter = b.Filter
+	return a
+}
+
 // Draw draws the entire thing, with default draw options.
 func (g *Game) Draw(screen *ebiten.Image) {
 	if g.Hidden {
 		return
 	}
-	if !gameDoesEverything {
-		g.Root.Draw(screen, ebiten.DrawImageOptions{})
-	}
+
 	if gameDoesEverything {
-		hidden := map[interface{}]bool{
-			g: false, // g.Hidden checked above
+		type state struct {
+			hidden bool
+			opts   ebiten.DrawImageOptions
 		}
-		transform := map[interface{}]ebiten.DrawImageOptions{
-			g: {},
+		accum := map[interface{}]state{
+			g: {hidden: false},
 		}
 		// draw everything
 		for _, d := range g.drawList {
-			// directly hidden?
+			// is d directly hidden?
 			if h, ok := d.(Hider); ok && h.IsHidden() {
-				hidden[d] = true
-				continue
+				accum[d] = state{hidden: true}
+				continue // skip drawing
 			}
-			// hidden by parent?
-			// walk up the parents to find the lowest known
-			hid := false
+			// walk up g.par to find the nearest parent state in accum
+			var st state
 			stack := []interface{}{d}
-			for p := g.par[d]; p != nil; p = g.par[p] {
-				if h, found := hidden[p]; found {
-					hid = h
+			for p := g.par[d]; ; p = g.par[p] {
+				if s, found := accum[p]; found {
+					st = s
 					break
 				}
 				stack = append(stack, p)
 			}
-			// unwind the stack, setting known values
+			// unwind the stack, accumulating state along the way
 			for len(stack) > 0 {
 				l1 := len(stack) - 1
 				p := stack[l1]
 				stack = stack[:l1]
 				if h, ok := p.(Hider); ok {
-					hid = hid || h.IsHidden()
-					hidden[p] = hid
+					st.hidden = st.hidden || h.IsHidden()
 				}
+				if st.hidden {
+					accum[p] = state{hidden: true}
+					continue
+				}
+				if t, ok := p.(Transformer); ok {
+					st.opts = concatOpts(t.Transform(), st.opts)
+				}
+				accum[p] = st
 			}
 
-			// now...skip if hidden
-			if hid {
+			// now...skip drawing if hidden :P
+			if st.hidden {
 				continue
 			}
-
-			if t, ok := d.(Transformer); ok {
-				transform[t] = t.Transform() // concatted with parent transform...
-			}
-			d.Draw(screen, ebiten.DrawImageOptions{})
+			d.Draw(screen, st.opts)
 		}
+	} else { // !gameDoesEverything
+		g.Root.Draw(screen, ebiten.DrawImageOptions{})
 	}
 }
 
diff --git a/engine/interface.go b/engine/interface.go
index f5ac88a..07e9df5 100644
--- a/engine/interface.go
+++ b/engine/interface.go
@@ -156,6 +156,7 @@ type Scener interface {
 	Identifier
 	Prepper
 	Scanner
+	Transformer
 	Updater
 }
 
diff --git a/engine/scene.go b/engine/scene.go
index bdbc19b..02a5231 100644
--- a/engine/scene.go
+++ b/engine/scene.go
@@ -28,7 +28,7 @@ type Scene struct {
 
 // Draw draws all components in order.
 func (s *Scene) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
-	if s.Hidden {
+	if s.Hidden || gameDoesEverything {
 		return
 	}
 	if s.Camera == nil {
@@ -106,6 +106,14 @@ func (s *Scene) Draw(screen *ebiten.Image, opts ebiten.DrawImageOptions) {
 	}
 }
 
+// Transform returns the camera transform
+func (s *Scene) Transform() ebiten.DrawImageOptions {
+	if s.Camera == nil {
+		return ebiten.DrawImageOptions{}
+	}
+	return s.Camera.Transform()
+}
+
 // Prepare does an initial Z-order sort.
 func (s *Scene) Prepare(game *Game) error {
 	s.sortByDrawOrder()
diff --git a/engine/sceneref.go b/engine/sceneref.go
index 5cb702a..c80c425 100644
--- a/engine/sceneref.go
+++ b/engine/sceneref.go
@@ -88,5 +88,8 @@ func (r SceneRef) Prepare(g *Game) error { return r.scene.Prepare(g) }
 // Scan returns the components in the scene.
 func (r SceneRef) Scan() []interface{} { return r.scene.Scan() }
 
+// Transform returns the value of Transform from the scene.
+func (r SceneRef) Transform() ebiten.DrawImageOptions { return r.scene.Transform() }
+
 // Update updates the scene.
 func (r SceneRef) Update() error { return r.scene.Update() }