Add entity component system

component/once.go

@@ -0,0 +1,3 @@
+package component
+
+type Once struct{}

game/game.go

@@ -1,29 +1,29 @@
 package game
 
 import (
+	"log"
 	"os"
 
+	"code.rocketnine.space/tslocum/commandeuropa/component"
+	"code.rocketnine.space/tslocum/commandeuropa/system"
 	"code.rocketnine.space/tslocum/commandeuropa/world"
+	"code.rocketnine.space/tslocum/gohan"
 	"github.com/hajimehoshi/ebiten/v2"
 )
 
 type Game struct{}
 
 func NewGame() (*Game, error) {
-	return &Game{}, nil
-}
+	g := &Game{}
 
-func (g *Game) Update() error {
-	if ebiten.IsWindowBeingClosed() {
-		g.Exit()
-		return nil
-	}
+	gohan.AddSystem(&system.RenderEnvironment{})
+	gohan.AddSystem(&system.RenderDebug{})
 
-	return nil
-}
-
-func (g *Game) Draw(screen *ebiten.Image) {
+	// Create singleton entity for systems that run one time each tick.
+	once := gohan.NewEntity()
+	once.AddComponent(&component.Once{})
 
+	return g, nil
 }
 
 func (g *Game) Layout(outsideWidth, outsideHeight int) (screenWidth, screenHeight int) {
@@ -35,6 +35,22 @@ func (g *Game) Layout(outsideWidth, outsideHeight int) (screenWidth, screenHeigh
 	return outsideWidth, outsideHeight
 }
 
+func (g *Game) Update() error {
+	if ebiten.IsWindowBeingClosed() {
+		g.Exit()
+		return nil
+	}
+
+	return gohan.Update()
+}
+
+func (g *Game) Draw(screen *ebiten.Image) {
+	err := gohan.Draw(screen)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
 func (g *Game) Exit() {
 	os.Exit(0)
 }

go.mod

@@ -2,7 +2,10 @@ module code.rocketnine.space/tslocum/commandeuropa
 
 go 1.19
 
-require github.com/hajimehoshi/ebiten/v2 v2.4.12
+require (
+	code.rocketnine.space/tslocum/gohan v1.0.0
+	github.com/hajimehoshi/ebiten/v2 v2.4.12
+)
 
 require (
 	github.com/ebitengine/purego v0.1.0 // indirect

go.sum

@@ -1,3 +1,5 @@
+code.rocketnine.space/tslocum/gohan v1.0.0 h1:WBcJq7nVfmr1EB8bew6xWlB5Q1714yWJ3a9/q6aBBrY=
+code.rocketnine.space/tslocum/gohan v1.0.0/go.mod h1:12yOt5Ygl/RVwnnZSVZRuS1W6gCaHJgezcvg8+THk10=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
 github.com/ebitengine/purego v0.0.0-20220905075623-aeed57cda744/go.mod h1:Eh8I3yvknDYZeCuXH9kRNaPuHEwvXDCk378o9xszmHg=
 github.com/ebitengine/purego v0.1.0 h1:vAEo1FvmbjA050QKsbDbcHj03hhMMvh0fmr9LSehpnU=

system/renderdebug.go

@@ -0,0 +1,46 @@
+package system
+
+import (
+	"fmt"
+	"image/color"
+
+	"code.rocketnine.space/tslocum/commandeuropa/component"
+	"code.rocketnine.space/tslocum/commandeuropa/world"
+	"code.rocketnine.space/tslocum/gohan"
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
+)
+
+type RenderDebug struct {
+	Once *component.Once
+
+	op          *ebiten.DrawImageOptions
+	debugImg    *ebiten.Image
+	initialized bool
+}
+
+func (s *RenderDebug) Initialize() {
+	s.op = &ebiten.DrawImageOptions{}
+	s.op.GeoM.Scale(2, 2)
+	s.debugImg = ebiten.NewImage(80, 80)
+	s.initialized = true
+}
+
+func (s *RenderDebug) Update(_ gohan.Entity) error {
+	return gohan.ErrUnregister
+}
+
+func (s *RenderDebug) Draw(e gohan.Entity, screen *ebiten.Image) error {
+	if world.Debug <= 0 {
+		return nil
+	}
+
+	if !s.initialized {
+		s.Initialize()
+	}
+
+	s.debugImg.Fill(color.RGBA{0, 0, 0, 80})
+	ebitenutil.DebugPrintAt(s.debugImg, fmt.Sprintf("ENT %d\nUPD %d\nDRA %d\nTPS %0.0f\nFPS %0.0f", gohan.CurrentEntities(), gohan.CurrentUpdates(), gohan.CurrentDraws(), ebiten.CurrentTPS(), ebiten.CurrentFPS()), 2, 0)
+	screen.DrawImage(s.debugImg, s.op)
+	return nil
+}

system/renderenvironment.go

@@ -0,0 +1,22 @@
+package system
+
+import (
+	"image/color"
+
+	"code.rocketnine.space/tslocum/commandeuropa/component"
+	"code.rocketnine.space/tslocum/gohan"
+	"github.com/hajimehoshi/ebiten/v2"
+)
+
+type RenderEnvironment struct {
+	Once *component.Once
+}
+
+func (r *RenderEnvironment) Update(e gohan.Entity) error {
+	return gohan.ErrUnregister
+}
+
+func (r *RenderEnvironment) Draw(e gohan.Entity, screen *ebiten.Image) error {
+	screen.Fill(color.RGBA{0, 0, 255, 255})
+	return nil
+}