loop: Remove IsRunning

internal/loop/run.go

@@ -27,14 +27,6 @@ func CurrentFPS() float64 {
 	return currentRunContext.getCurrentFPS()
 }
 
-func IsRunning() bool {
-	// TODO: Need lock?
-	if currentRunContext == nil {
-		return false
-	}
-	return currentRunContext.isRunning()
-}
-
 type runContext struct {
 	running        bool
 	fps            int

internal/ui/ui_glfw.go

@@ -22,6 +22,7 @@ package ui
 import (
 	"errors"
 	"runtime"
+	"sync"
 	"time"
 
 	"github.com/go-gl/glfw/v3.2/glfw"
@@ -34,7 +35,9 @@ type userInterface struct {
 	height      int
 	scale       float64
 	funcs       chan func()
+	running     bool
 	sizeChanged bool
+	m           sync.Mutex
 }
 
 var currentUI *userInterface
@@ -74,6 +77,10 @@ func initialize() error {
 
 func RunMainThreadLoop(ch <-chan error) error {
 	// TODO: Check this is done on the main thread.
+	currentUI.setRunning(true)
+	defer func() {
+		currentUI.setRunning(false)
+	}()
 	for {
 		select {
 		case f := <-currentUI.funcs:
@@ -85,6 +92,18 @@ func RunMainThreadLoop(ch <-chan error) error {
 	}
 }
 
+func (u *userInterface) isRunning() bool {
+	u.m.Lock()
+	defer u.m.Unlock()
+	return u.running
+}
+
+func (u *userInterface) setRunning(running bool) {
+	u.m.Lock()
+	defer u.m.Unlock()
+	u.running = running
+}
+
 func (u *userInterface) runOnMainThread(f func() error) error {
 	if u.funcs == nil {
 		// already closed
@@ -102,6 +121,9 @@ func (u *userInterface) runOnMainThread(f func() error) error {
 
 func SetScreenSize(width, height int) (bool, error) {
 	u := currentUI
+	if !u.isRunning() {
+		return false, errors.New("ui: Run is not called yet")
+	}
 	r := false
 	if err := u.runOnMainThread(func() error {
 		var err error
@@ -118,6 +140,9 @@ func SetScreenSize(width, height int) (bool, error) {
 
 func SetScreenScale(scale float64) (bool, error) {
 	u := currentUI
+	if !u.isRunning() {
+		return false, errors.New("ui: Run is not called yet")
+	}
 	r := false
 	if err := u.runOnMainThread(func() error {
 		var err error
@@ -134,6 +159,9 @@ func SetScreenScale(scale float64) (bool, error) {
 
 func ScreenScale() float64 {
 	u := currentUI
+	if !u.isRunning() {
+		return 0
+	}
 	s := 0.0
 	_ = u.runOnMainThread(func() error {
 		s = u.scale

run.go

@@ -15,7 +15,6 @@
 package ebiten
 
 import (
-	"math"
 	"sync/atomic"
 
 	"github.com/hajimehoshi/ebiten/internal/loop"
@@ -116,9 +115,6 @@ func RunWithoutMainLoop(f func(*Image) error, width, height int, scale float64,
 //
 // This function is concurrent-safe.
 func SetScreenSize(width, height int) {
-	if !loop.IsRunning() {
-		panic("ebiten: Run is not called yet")
-	}
 	if width <= 0 || height <= 0 {
 		panic("ebiten: width and height must be positive")
 	}
@@ -131,9 +127,6 @@ func SetScreenSize(width, height int) {
 //
 // This function is concurrent-safe.
 func SetScreenScale(scale float64) {
-	if !loop.IsRunning() {
-		panic("ebiten: Run is not called yet")
-	}
 	if scale <= 0 {
 		panic("ebiten: scale must be positive")
 	}
@@ -144,13 +137,10 @@ func SetScreenScale(scale float64) {
 
 // ScreenScale returns the current screen scale.
 //
-// If Run is not called, this returns NaN.
+// If Run is not called, this returns 0.
 //
 // This function is concurrent-safe.
 func ScreenScale() float64 {
-	if !loop.IsRunning() {
-		return math.NaN()
-	}
 	return ui.ScreenScale()
 }