ui: Introduce ScreenSizeEvent to simplify the run loop

internal/loop/run.go

@@ -15,7 +15,6 @@
 package loop
 
 import (
-	"errors"
 	"sync"
 	"time"
 
@@ -24,10 +23,6 @@ import (
 
 const FPS = 60
 
-func Main() {
-	ui.Main()
-}
-
 func CurrentFPS() float64 {
 	return currentRunContext.currentFPS()
 }
@@ -40,24 +35,9 @@ func IsRunningSlowly() bool {
 	return currentRunContext.isRunningSlowly()
 }
 
-func SetScreenSize(width, height int) error {
-	return currentRunContext.setScreenSize(width, height)
-}
-
-func SetScreenScale(scale int) error {
-	return currentRunContext.setScreenScale(scale)
-}
-
-func ScreenScale() int {
-	return ui.CurrentUI().ScreenScale()
-}
-
 type runContext struct {
 	running       bool
 	fps           float64
-	newScreenWidth  int
-	newScreenHeight int
-	newScreenScale  int
 	runningSlowly bool
 	m             sync.RWMutex
 }
@@ -114,60 +94,6 @@ func (c *runContext) setRunningSlowly(isRunningSlowly bool) {
 	c.runningSlowly = isRunningSlowly
 }
 
-func (c *runContext) updateScreenSize(g GraphicsContext) error {
-	c.m.Lock()
-	defer c.m.Unlock()
-	if c.newScreenWidth == 0 && c.newScreenHeight == 0 && c.newScreenScale == 0 {
-		return nil
-	}
-	changed := false
-	if 0 < c.newScreenWidth || 0 < c.newScreenHeight {
-		c := ui.CurrentUI().SetScreenSize(c.newScreenWidth, c.newScreenHeight)
-		changed = changed || c
-	}
-	if 0 < c.newScreenScale {
-		c := ui.CurrentUI().SetScreenScale(c.newScreenScale)
-		changed = changed || c
-	}
-	if changed {
-		w, h := c.newScreenWidth, c.newScreenHeight
-		if err := g.SetSize(w, h, ui.CurrentUI().ActualScreenScale()); err != nil {
-			return err
-		}
-	}
-	c.newScreenWidth = 0
-	c.newScreenHeight = 0
-	c.newScreenScale = 0
-	return nil
-}
-
-func (c *runContext) setScreenSize(width, height int) error {
-	c.m.Lock()
-	defer c.m.Unlock()
-	if !c.running {
-		return errors.New("ebiten: SetScreenSize must be called during Run")
-	}
-	if width <= 0 || height <= 0 {
-		return errors.New("ebiten: width and height must be positive")
-	}
-	c.newScreenWidth = width
-	c.newScreenHeight = height
-	return nil
-}
-
-func (c *runContext) setScreenScale(scale int) error {
-	c.m.Lock()
-	defer c.m.Unlock()
-	if !c.running {
-		return errors.New("ebiten: SetScreenScale must be called during Run")
-	}
-	if scale <= 0 {
-		return errors.New("ebiten: scale must be positive")
-	}
-	c.newScreenScale = scale
-	return nil
-}
-
 type GraphicsContext interface {
 	SetSize(width, height, scale int) error
 	Update() error
@@ -182,23 +108,20 @@ func Run(g GraphicsContext, width, height, scale int, title string) error {
 	}
 	defer ui.CurrentUI().Terminate()
 
-	if err := g.SetSize(width, height, ui.CurrentUI().ActualScreenScale()); err != nil {
-		return err
-	}
-
 	frames := 0
 	n := now()
 	beforeForUpdate := n
 	beforeForFPS := n
 	for {
-		if err := currentRunContext.updateScreenSize(g); err != nil {
-			return err
-		}
 		e, err := ui.CurrentUI().Update()
 		if err != nil {
 			return err
 		}
-		switch e.(type) {
+		switch e := e.(type) {
+		case ui.ScreenSizeEvent:
+			if err := g.SetSize(e.Width, e.Height, e.ActualScale); err != nil {
+				return err
+			}
 		case ui.CloseEvent:
 			return nil
 		case ui.RenderEvent:

internal/ui/event.go

@@ -19,3 +19,10 @@ type CloseEvent struct {
 
 type RenderEvent struct {
 }
+
+type ScreenSizeEvent struct {
+	Width       int
+	Height      int
+	Scale       int
+	ActualScale int
+}

internal/ui/ui_glfw.go

@@ -35,6 +35,7 @@ type UserInterface struct {
 	framebufferScale int
 	context          *opengl.Context
 	funcs            chan func()
+	sizeChanged      bool
 }
 
 var currentUI *UserInterface
@@ -63,6 +64,7 @@ func initialize() (*opengl.Context, error) {
 	u := &UserInterface{
 		window:      window,
 		funcs:       make(chan func()),
+		sizeChanged: true,
 	}
 	ch := make(chan error)
 	go func() {
@@ -140,14 +142,6 @@ func (u *UserInterface) ScreenScale() int {
 	return s
 }
 
-func (u *UserInterface) ActualScreenScale() int {
-	s := 0
-	u.runOnMainThread(func() {
-		s = u.actualScreenScale()
-	})
-	return s
-}
-
 func (u *UserInterface) Start(width, height, scale int, title string) error {
 	var err error
 	u.runOnMainThread(func() {
@@ -200,6 +194,24 @@ func (u *UserInterface) Update() (interface{}, error) {
 	if shouldClose {
 		return CloseEvent{}, nil
 	}
+
+	var screenSizeEvent *ScreenSizeEvent
+	u.runOnMainThread(func() {
+		if !u.sizeChanged {
+			return
+		}
+		u.sizeChanged = false
+		screenSizeEvent = &ScreenSizeEvent{
+			Width:       u.width,
+			Height:      u.height,
+			Scale:       u.scale,
+			ActualScale: u.actualScreenScale(),
+		}
+	})
+	if screenSizeEvent != nil {
+		return *screenSizeEvent, nil
+	}
+
 	var ferr error
 	u.runOnMainThread(func() {
 		if err := u.pollEvents(); err != nil {
@@ -291,5 +303,6 @@ event:
 	// This is usually 1, but sometimes more than 1 (e.g. Retina Mac)
 	fw, _ := window.GetFramebufferSize()
 	u.framebufferScale = fw / width / u.windowScale()
+	u.sizeChanged = true
 	return true
 }

internal/ui/ui_js.go

@@ -46,9 +46,12 @@ var canvas *js.Object
 type UserInterface struct {
 	scale       int
 	deviceScale float64
+	sizeChanged bool
 }
 
-var currentUI = &UserInterface{}
+var currentUI = &UserInterface{
+	sizeChanged: true,
+}
 
 func CurrentUI() *UserInterface {
 	return currentUI
@@ -79,6 +82,17 @@ func vsync() {
 
 func (u *UserInterface) Update() (interface{}, error) {
 	currentInput.UpdateGamepads()
+	if u.sizeChanged {
+		u.sizeChanged = false
+		w, h := u.size()
+		e := ScreenSizeEvent{
+			Width:       w,
+			Height:      h,
+			Scale:       u.ScreenScale(),
+			ActualScale: u.ActualScreenScale(),
+		}
+		return e, nil
+	}
 	return RenderEvent{}, nil
 }
 
@@ -276,5 +290,6 @@ func (u *UserInterface) setScreenSize(width, height, scale int) bool {
 	// CSS calc requires space chars.
 	canvasStyle.Set("left", "calc((100% - "+strconv.Itoa(cssWidth)+"px) / 2)")
 	canvasStyle.Set("top", "calc((100% - "+strconv.Itoa(cssHeight)+"px) / 2)")
+	u.sizeChanged = true
 	return true
 }

run.go

@@ -16,6 +16,7 @@ package ebiten
 
 import (
 	"github.com/hajimehoshi/ebiten/internal/loop"
+	"github.com/hajimehoshi/ebiten/internal/ui"
 )
 
 // FPS represents how many times game updating happens in a second.
@@ -58,7 +59,7 @@ func Run(f func(*Image) error, width, height, scale int, title string) error {
 		g := newGraphicsContext(f)
 		ch <- loop.Run(g, width, height, scale, title)
 	}()
-	loop.Main()
+	ui.Main()
 	return <-ch
 }
 
@@ -67,23 +68,25 @@ func Run(f func(*Image) error, width, height, scale int, title string) error {
 //
 // This function is concurrent-safe.
 func SetScreenSize(width, height int) {
-	if err := loop.SetScreenSize(width, height); err != nil {
+	if width <= 0 || height <= 0 {
-		panic(err)
+		panic("ebiten: width and height must be positive")
 	}
+	ui.CurrentUI().SetScreenSize(width, height)
 }
 
 // SetScreenScale changes the scale of the screen.
 //
 // This function is concurrent-safe.
 func SetScreenScale(scale int) {
-	if err := loop.SetScreenScale(scale); err != nil {
+	if scale <= 0 {
-		panic(err)
+		panic("ebiten: scale must be positive")
 	}
+	ui.CurrentUI().SetScreenScale(scale)
 }
 
 // ScreenScale returns the current screen scale.
 //
 // This function is concurrent-safe.
 func ScreenScale() int {
-	return loop.ScreenScale()
+	return ui.CurrentUI().ScreenScale()
 }