Reduce panics (#196)

affine.go

@@ -38,7 +38,7 @@ func isIdentity(ebiten affine) bool {
 func add(lhs, rhs, result affine) {
 	dim := lhs.dim()
 	if dim != rhs.dim() {
-		panic("diffrent-sized matrices can't be multiplied")
+		panic("ebiten: diffrent-sized matrices can't be multiplied")
 	}
 
 	for i := 0; i < dim-1; i++ {
@@ -52,7 +52,7 @@ func add(lhs, rhs, result affine) {
 func mul(lhs, rhs, result affine) {
 	dim := lhs.dim()
 	if dim != rhs.dim() {
-		panic("diffrent-sized matrices can't be multiplied")
+		panic("ebiten: diffrent-sized matrices can't be multiplied")
 	}
 
 	for i := 0; i < dim-1; i++ {

imageparts.go

@@ -86,7 +86,7 @@ type textureQuads struct {
 func (t *textureQuads) vertices(vertices []int16) int {
 	l := t.parts.Len()
 	if len(vertices) < l*16 {
-		panic(fmt.Sprintf("graphics: vertices size must be greater than %d but %d", l*16, len(vertices)))
+		panic(fmt.Sprintf("ebiten: vertices size must be greater than %d but %d", l*16, len(vertices)))
 	}
 	p := t.parts
 	w, h := t.width, t.height

init.go

@@ -22,5 +22,9 @@ import (
 var glContext *opengl.Context
 
 func init() {
-	glContext = ui.Init()
+	var err error
+	glContext, err = ui.Init()
+	if err != nil {
+		panic(err)
+	}
 }

internal/graphics/opengl/context_desktop.go

@@ -52,7 +52,7 @@ type context struct {
 	lastCompositeMode CompositeMode
 }
 
-func NewContext() *Context {
+func NewContext() (*Context, error) {
 	c := &Context{
 		Nearest:            gl.NEAREST,
 		Linear:             gl.LINEAR,
@@ -74,7 +74,7 @@ func NewContext() *Context {
 	c.locationCache = newLocationCache()
 	c.funcs = make(chan func())
 	c.lastCompositeMode = CompositeModeUnknown
-	return c
+	return c, nil
 }
 
 func (c *Context) Loop() {
@@ -96,18 +96,24 @@ func (c *Context) RunOnContextThread(f func()) {
 	return
 }
 
-func (c *Context) Init() {
+func (c *Context) Init() error {
+	var err error
 	c.RunOnContextThread(func() {
 		// This initialization must be done after Loop is called.
 		// This is why Init is separated from NewContext.
 
 		if err := gl.Init(); err != nil {
-			panic(fmt.Sprintf("opengl: initializing error %v", err))
+			err = fmt.Errorf("opengl: initializing error %v", err)
+			return
 		}
 		// Textures' pixel formats are alpha premultiplied.
 		gl.Enable(gl.BLEND)
 	})
+	if err != nil {
+		return err
+	}
 	c.BlendFunc(CompositeModeSourceOver)
+	return nil
 }
 
 func (c *Context) BlendFunc(mode CompositeMode) {
@@ -121,14 +127,6 @@ func (c *Context) BlendFunc(mode CompositeMode) {
 	})
 }
 
-func (c *Context) Check() {
-	c.RunOnContextThread(func() {
-		if e := gl.GetError(); e != gl.NO_ERROR {
-			panic(fmt.Sprintf("check failed: %d", e))
-		}
-	})
-}
-
 func (c *Context) NewTexture(width, height int, pixels []uint8, filter Filter) (texture Texture, err error) {
 	c.RunOnContextThread(func() {
 		var t uint32
@@ -364,7 +362,7 @@ func (c *Context) UniformFloats(p Program, location string, v []float32) {
 func (c *Context) getAttribLocation(p Program, location string) attribLocation {
 	attrib := attribLocation(gl.GetAttribLocation(uint32(p), gl.Str(location+"\x00")))
 	if attrib == -1 {
-		panic("invalid attrib location: " + location)
+		panic("opengl: invalid attrib location: " + location)
 	}
 	return attrib
 }

internal/graphics/opengl/context_js.go

@@ -70,7 +70,7 @@ type context struct {
 	lastCompositeMode CompositeMode
 }
 
-func NewContext() *Context {
+func NewContext() (*Context, error) {
 	var gl *webgl.Context
 
 	if js.Global.Get("require") == js.Undefined {
@@ -82,7 +82,7 @@ func NewContext() *Context {
 			PremultipliedAlpha: true,
 		})
 		if err != nil {
-			panic(err)
+			return nil, err
 		}
 	} else {
 		// TODO: Now Ebiten with headless-gl doesn't work well (#141).
@@ -117,7 +117,7 @@ func NewContext() *Context {
 	c.locationCache = newLocationCache()
 	c.lastCompositeMode = CompositeModeUnknown
 	c.init()
-	return c
+	return c, nil
 }
 
 func (c *Context) init() {
@@ -138,13 +138,6 @@ func (c *Context) BlendFunc(mode CompositeMode) {
 	gl.BlendFunc(int(s), int(d))
 }
 
-func (c *Context) Check() {
-	gl := c.gl
-	if e := gl.GetError(); e != gl.NO_ERROR {
-		panic(fmt.Sprintf("opengl: check failed: %d", e))
-	}
-}
-
 func (c *Context) NewTexture(width, height int, pixels []uint8, filter Filter) (Texture, error) {
 	gl := c.gl
 	t := gl.CreateTexture()

internal/graphics/opengl/context_mobile.go

@@ -107,12 +107,6 @@ func (c *Context) RunOnContextThread(f func()) {
 	return
 }
 
-func (c *Context) Check() {
-	if e := gl.GetError(); e != mgl.NO_ERROR {
-		panic(fmt.Sprintf("check failed: %d", e))
-	}
-}
-
 func (c *Context) NewTexture(width, height int, pixels []uint8, filter Filter) (Texture, error) {
 	t := gl.CreateTexture()
 	if t.Value <= 0 {

internal/ui/ui_glfw.go

@@ -18,7 +18,6 @@ package ui
 
 import (
 	"errors"
-	"fmt"
 	"runtime"
 	"sync"
 	"time"
@@ -48,12 +47,12 @@ func CurrentUI() *UserInterface {
 	return currentUI
 }
 
-func Init() *opengl.Context {
+func Init() (*opengl.Context, error) {
 	runtime.LockOSThread()
 
 	err := glfw.Init()
 	if err != nil {
-		panic(fmt.Sprintf("glfw.Init() fails: %v", err))
+		return nil, err
 	}
 	glfw.WindowHint(glfw.Visible, glfw.False)
 	glfw.WindowHint(glfw.Resizable, glfw.False)
@@ -63,26 +62,34 @@ func Init() *opengl.Context {
 	// As start, create an window with temporary size to create OpenGL context thread.
 	window, err := glfw.CreateWindow(16, 16, "", nil, nil)
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 
 	u := &UserInterface{
 		window: window,
 	}
-	ch := make(chan struct{})
+	ch := make(chan error)
 	go func() {
 		runtime.LockOSThread()
 		u.window.MakeContextCurrent()
 		glfw.SwapInterval(1)
-		u.context = opengl.NewContext()
+		var err error
+		u.context, err = opengl.NewContext()
+		if err != nil {
+			ch <- err
+		}
 		close(ch)
 		u.context.Loop()
 	}()
 	currentUI = u
-	<-ch
+	if err := <-ch; err != nil {
-	u.context.Init()
+		return nil, err
+	}
+	if err := u.context.Init(); err != nil {
+		return nil, err
+	}
 
-	return u.context
+	return u.context, nil
 }
 
 func (u *UserInterface) SetScreenSize(width, height int) bool {

internal/ui/ui_js.go

@@ -102,7 +102,7 @@ func (u *UserInterface) SwapBuffers() {
 	}
 }
 
-func Init() *opengl.Context {
+func Init() (*opengl.Context, error) {
 	// Do nothing in node.js.
 	if js.Global.Get("require") != js.Undefined {
 		return opengl.NewContext()

run.go

@@ -15,6 +15,7 @@
 package ebiten
 
 import (
+	"errors"
 	"sync"
 	"time"
 
@@ -104,29 +105,31 @@ func (c *runContext) updateScreenSize(g *graphicsContext) error {
 	return nil
 }
 
-func (c *runContext) SetScreenSize(width, height int) {
+func (c *runContext) SetScreenSize(width, height int) error {
 	c.m.Lock()
 	defer c.m.Unlock()
 	if !c.isRunning {
-		panic("ebiten: SetScreenSize must be called during Run")
+		return errors.New("ebiten: SetScreenSize must be called during Run")
 	}
 	if width <= 0 || height <= 0 {
-		panic("ebiten: width and height must be positive")
+		return errors.New("ebiten: width and height must be positive")
 	}
 	c.newScreenWidth = width
 	c.newScreenHeight = height
+	return nil
 }
 
-func (c *runContext) SetScreenScale(scale int) {
+func (c *runContext) SetScreenScale(scale int) error {
 	c.m.Lock()
 	defer c.m.Unlock()
 	if !c.isRunning {
-		panic("ebiten: SetScreenScale must be called during Run")
+		return errors.New("ebiten: SetScreenScale must be called during Run")
 	}
 	if scale <= 0 {
-		panic("ebiten: scale must be positive")
+		return errors.New("ebiten: scale must be positive")
 	}
 	c.newScreenScale = scale
+	return nil
 }
 
 // FPS represents how many times game updating happens in a second.
@@ -172,7 +175,6 @@ func Run(f func(*Image) error, width, height, scale int, title string) error {
 	}
 	defer ui.CurrentUI().Terminate()
 
-	glContext.Check()
 	graphicsContext, err := newGraphicsContext(width, height, ui.CurrentUI().ActualScreenScale())
 	if err != nil {
 		return err
@@ -238,14 +240,18 @@ func Run(f func(*Image) error, width, height, scale int, title string) error {
 //
 // This function is concurrent-safe.
 func SetScreenSize(width, height int) {
-	currentRunContext.SetScreenSize(width, height)
+	if err := currentRunContext.SetScreenSize(width, height); err != nil {
+		panic(err)
+	}
 }
 
 // SetScreenSize changes the scale of the screen.
 //
 // This function is concurrent-safe.
 func SetScreenScale(scale int) {
-	currentRunContext.SetScreenScale(scale)
+	if err := currentRunContext.SetScreenScale(scale); err != nil {
+		panic(err)
+	}
 }
 
 // ScreenScale returns the current screen scale.