internal/graphicsdriver/opengl/gl: automatically choose OpenGL and OpenGL ES

Updates #292

.github/workflows/test.yml

@@ -134,7 +134,7 @@ jobs:
         if: runner.os == 'Linux'
         run: |
           sudo apt-get install libgles2-mesa-dev
-          env EBITENGINE_GRAPHICS_LIBRARY=opengl go test -tags=opengles -shuffle=on -v ./...
+          env EBITENGINE_GRAPHICS_LIBRARY=opengl EBITENGINE_OPENGL=es go test -shuffle=on -v ./...
 
       - name: go test (Windows 386)
         if: runner.os == 'Windows'

doc.go

@@ -84,6 +84,7 @@
 // `EBITENGINE_OPENGL` environment variable specifies various parameters for OpenGL.
 // You can specify multiple values separated by a comma. The default value is empty (i.e. no parameters).
 //
+//	"es":     Use OpenGL ES. Without this, OpenGL and OpenGL ES are automatically chosen.
 //	"webgl1": Use WebGL 1. This is valid only on browsers.
 //
 // # Build tags
@@ -99,6 +100,4 @@
 // `microsoftgdk` is for Microsoft GDK (e.g. Xbox).
 //
 // `nintendosdk` is for NintendoSDK (e.g. Nintendo Switch).
-//
-// `opengles` uses OpenGL ES (2) instead of OpenGL.
 package ebiten

internal/graphicsdriver/opengl/context_notjs.go

@@ -89,8 +89,8 @@ type contextImpl struct {
 
 func (c *context) reset() error {
 	if !c.init {
-		// Initialize OpenGL after WGL is initialized especially for Windows (#2452).
-		if err := c.ctx.Init(); err != nil {
+		// Load OpenGL functions after WGL is initialized especially for Windows (#2452).
+		if err := c.ctx.LoadFunctions(); err != nil {
 			return err
 		}
 		c.init = true

internal/graphicsdriver/opengl/gl/default_android.go

@@ -33,11 +33,11 @@ func glBool(x bool) C.GLboolean {
 
 type defaultContext struct{}
 
-func NewDefaultContext() Context {
-	return defaultContext{}
+func NewDefaultContext() (Context, error) {
+	return defaultContext{}, nil
 }
 
-func (defaultContext) Init() error {
+func (defaultContext) LoadFunctions() error {
 	return nil
 }
 

internal/graphicsdriver/opengl/gl/default_notpurego.go

@@ -393,10 +393,16 @@ type defaultContext struct {
 	gpUseProgram                 C.GPUSEPROGRAM
 	gpVertexAttribPointer        C.GPVERTEXATTRIBPOINTER
 	gpViewport                   C.GPVIEWPORT
+
+	isES bool
 }
 
-func NewDefaultContext() Context {
-	return &defaultContext{}
+func NewDefaultContext() (Context, error) {
+	ctx := &defaultContext{}
+	if err := ctx.init(); err != nil {
+		return nil, err
+	}
+	return ctx, nil
 }
 
 func boolToInt(b bool) int {
@@ -407,7 +413,7 @@ func boolToInt(b bool) int {
 }
 
 func (c *defaultContext) IsES() bool {
-	return isES
+	return c.isES
 }
 
 func (c *defaultContext) ActiveTexture(texture uint32) {
@@ -741,244 +747,244 @@ func (c *defaultContext) Viewport(x int32, y int32, width int32, height int32) {
 	C.glowViewport(c.gpViewport, (C.GLint)(x), (C.GLint)(y), (C.GLsizei)(width), (C.GLsizei)(height))
 }
 
-func (c *defaultContext) Init() error {
-	c.gpActiveTexture = (C.GPACTIVETEXTURE)(getProcAddress("glActiveTexture"))
+func (c *defaultContext) LoadFunctions() error {
+	c.gpActiveTexture = (C.GPACTIVETEXTURE)(c.getProcAddress("glActiveTexture"))
 	if c.gpActiveTexture == nil {
 		return errors.New("gl: glActiveTexture is missing")
 	}
-	c.gpAttachShader = (C.GPATTACHSHADER)(getProcAddress("glAttachShader"))
+	c.gpAttachShader = (C.GPATTACHSHADER)(c.getProcAddress("glAttachShader"))
 	if c.gpAttachShader == nil {
 		return errors.New("gl: glAttachShader is missing")
 	}
-	c.gpBindAttribLocation = (C.GPBINDATTRIBLOCATION)(getProcAddress("glBindAttribLocation"))
+	c.gpBindAttribLocation = (C.GPBINDATTRIBLOCATION)(c.getProcAddress("glBindAttribLocation"))
 	if c.gpBindAttribLocation == nil {
 		return errors.New("gl: glBindAttribLocation is missing")
 	}
-	c.gpBindBuffer = (C.GPBINDBUFFER)(getProcAddress("glBindBuffer"))
+	c.gpBindBuffer = (C.GPBINDBUFFER)(c.getProcAddress("glBindBuffer"))
 	if c.gpBindBuffer == nil {
 		return errors.New("gl: glBindBuffer is missing")
 	}
-	c.gpBindFramebufferEXT = (C.GPBINDFRAMEBUFFEREXT)(getProcAddress("glBindFramebufferEXT"))
-	c.gpBindRenderbufferEXT = (C.GPBINDRENDERBUFFEREXT)(getProcAddress("glBindRenderbufferEXT"))
-	c.gpBindTexture = (C.GPBINDTEXTURE)(getProcAddress("glBindTexture"))
+	c.gpBindFramebufferEXT = (C.GPBINDFRAMEBUFFEREXT)(c.getProcAddress("glBindFramebufferEXT"))
+	c.gpBindRenderbufferEXT = (C.GPBINDRENDERBUFFEREXT)(c.getProcAddress("glBindRenderbufferEXT"))
+	c.gpBindTexture = (C.GPBINDTEXTURE)(c.getProcAddress("glBindTexture"))
 	if c.gpBindTexture == nil {
 		return errors.New("gl: glBindTexture is missing")
 	}
-	c.gpBlendEquationSeparate = (C.GPBLENDEQUATIONSEPARATE)(getProcAddress("glBlendEquationSeparate"))
+	c.gpBlendEquationSeparate = (C.GPBLENDEQUATIONSEPARATE)(c.getProcAddress("glBlendEquationSeparate"))
 	if c.gpBlendEquationSeparate == nil {
 		return errors.New("gl: glBlendEquationSeparate is missing")
 	}
-	c.gpBlendFuncSeparate = (C.GPBLENDFUNCSEPARATE)(getProcAddress("glBlendFuncSeparate"))
+	c.gpBlendFuncSeparate = (C.GPBLENDFUNCSEPARATE)(c.getProcAddress("glBlendFuncSeparate"))
 	if c.gpBlendFuncSeparate == nil {
 		return errors.New("gl: glBlendFuncSeparate is missing")
 	}
-	c.gpBufferData = (C.GPBUFFERDATA)(getProcAddress("glBufferData"))
+	c.gpBufferData = (C.GPBUFFERDATA)(c.getProcAddress("glBufferData"))
 	if c.gpBufferData == nil {
 		return errors.New("gl: glBufferData is missing")
 	}
-	c.gpBufferSubData = (C.GPBUFFERSUBDATA)(getProcAddress("glBufferSubData"))
+	c.gpBufferSubData = (C.GPBUFFERSUBDATA)(c.getProcAddress("glBufferSubData"))
 	if c.gpBufferSubData == nil {
 		return errors.New("gl: glBufferSubData is missing")
 	}
-	c.gpCheckFramebufferStatusEXT = (C.GPCHECKFRAMEBUFFERSTATUSEXT)(getProcAddress("glCheckFramebufferStatusEXT"))
-	c.gpClear = (C.GPCLEAR)(getProcAddress("glClear"))
+	c.gpCheckFramebufferStatusEXT = (C.GPCHECKFRAMEBUFFERSTATUSEXT)(c.getProcAddress("glCheckFramebufferStatusEXT"))
+	c.gpClear = (C.GPCLEAR)(c.getProcAddress("glClear"))
 	if c.gpClear == nil {
 		return errors.New("gl: glClear is missing")
 	}
-	c.gpColorMask = (C.GPCOLORMASK)(getProcAddress("glColorMask"))
+	c.gpColorMask = (C.GPCOLORMASK)(c.getProcAddress("glColorMask"))
 	if c.gpColorMask == nil {
 		return errors.New("gl: glColorMask is missing")
 	}
-	c.gpCompileShader = (C.GPCOMPILESHADER)(getProcAddress("glCompileShader"))
+	c.gpCompileShader = (C.GPCOMPILESHADER)(c.getProcAddress("glCompileShader"))
 	if c.gpCompileShader == nil {
 		return errors.New("gl: glCompileShader is missing")
 	}
-	c.gpCreateProgram = (C.GPCREATEPROGRAM)(getProcAddress("glCreateProgram"))
+	c.gpCreateProgram = (C.GPCREATEPROGRAM)(c.getProcAddress("glCreateProgram"))
 	if c.gpCreateProgram == nil {
 		return errors.New("gl: glCreateProgram is missing")
 	}
-	c.gpCreateShader = (C.GPCREATESHADER)(getProcAddress("glCreateShader"))
+	c.gpCreateShader = (C.GPCREATESHADER)(c.getProcAddress("glCreateShader"))
 	if c.gpCreateShader == nil {
 		return errors.New("gl: glCreateShader is missing")
 	}
-	c.gpDeleteBuffers = (C.GPDELETEBUFFERS)(getProcAddress("glDeleteBuffers"))
+	c.gpDeleteBuffers = (C.GPDELETEBUFFERS)(c.getProcAddress("glDeleteBuffers"))
 	if c.gpDeleteBuffers == nil {
 		return errors.New("gl: glDeleteBuffers is missing")
 	}
-	c.gpDeleteFramebuffersEXT = (C.GPDELETEFRAMEBUFFERSEXT)(getProcAddress("glDeleteFramebuffersEXT"))
-	c.gpDeleteProgram = (C.GPDELETEPROGRAM)(getProcAddress("glDeleteProgram"))
+	c.gpDeleteFramebuffersEXT = (C.GPDELETEFRAMEBUFFERSEXT)(c.getProcAddress("glDeleteFramebuffersEXT"))
+	c.gpDeleteProgram = (C.GPDELETEPROGRAM)(c.getProcAddress("glDeleteProgram"))
 	if c.gpDeleteProgram == nil {
 		return errors.New("gl: glDeleteProgram is missing")
 	}
-	c.gpDeleteRenderbuffersEXT = (C.GPDELETERENDERBUFFERSEXT)(getProcAddress("glDeleteRenderbuffersEXT"))
-	c.gpDeleteShader = (C.GPDELETESHADER)(getProcAddress("glDeleteShader"))
+	c.gpDeleteRenderbuffersEXT = (C.GPDELETERENDERBUFFERSEXT)(c.getProcAddress("glDeleteRenderbuffersEXT"))
+	c.gpDeleteShader = (C.GPDELETESHADER)(c.getProcAddress("glDeleteShader"))
 	if c.gpDeleteShader == nil {
 		return errors.New("gl: glDeleteShader is missing")
 	}
-	c.gpDeleteTextures = (C.GPDELETETEXTURES)(getProcAddress("glDeleteTextures"))
+	c.gpDeleteTextures = (C.GPDELETETEXTURES)(c.getProcAddress("glDeleteTextures"))
 	if c.gpDeleteTextures == nil {
 		return errors.New("gl: glDeleteTextures is missing")
 	}
-	c.gpDisable = (C.GPDISABLE)(getProcAddress("glDisable"))
+	c.gpDisable = (C.GPDISABLE)(c.getProcAddress("glDisable"))
 	if c.gpDisable == nil {
 		return errors.New("gl: glDisable is missing")
 	}
-	c.gpDisableVertexAttribArray = (C.GPDISABLEVERTEXATTRIBARRAY)(getProcAddress("glDisableVertexAttribArray"))
+	c.gpDisableVertexAttribArray = (C.GPDISABLEVERTEXATTRIBARRAY)(c.getProcAddress("glDisableVertexAttribArray"))
 	if c.gpDisableVertexAttribArray == nil {
 		return errors.New("gl: glDisableVertexAttribArray is missing")
 	}
-	c.gpDrawElements = (C.GPDRAWELEMENTS)(getProcAddress("glDrawElements"))
+	c.gpDrawElements = (C.GPDRAWELEMENTS)(c.getProcAddress("glDrawElements"))
 	if c.gpDrawElements == nil {
 		return errors.New("gl: glDrawElements is missing")
 	}
-	c.gpEnable = (C.GPENABLE)(getProcAddress("glEnable"))
+	c.gpEnable = (C.GPENABLE)(c.getProcAddress("glEnable"))
 	if c.gpEnable == nil {
 		return errors.New("gl: glEnable is missing")
 	}
-	c.gpEnableVertexAttribArray = (C.GPENABLEVERTEXATTRIBARRAY)(getProcAddress("glEnableVertexAttribArray"))
+	c.gpEnableVertexAttribArray = (C.GPENABLEVERTEXATTRIBARRAY)(c.getProcAddress("glEnableVertexAttribArray"))
 	if c.gpEnableVertexAttribArray == nil {
 		return errors.New("gl: glEnableVertexAttribArray is missing")
 	}
-	c.gpFlush = (C.GPFLUSH)(getProcAddress("glFlush"))
+	c.gpFlush = (C.GPFLUSH)(c.getProcAddress("glFlush"))
 	if c.gpFlush == nil {
 		return errors.New("gl: glFlush is missing")
 	}
-	c.gpFramebufferRenderbufferEXT = (C.GPFRAMEBUFFERRENDERBUFFEREXT)(getProcAddress("glFramebufferRenderbufferEXT"))
-	c.gpFramebufferTexture2DEXT = (C.GPFRAMEBUFFERTEXTURE2DEXT)(getProcAddress("glFramebufferTexture2DEXT"))
-	c.gpGenBuffers = (C.GPGENBUFFERS)(getProcAddress("glGenBuffers"))
+	c.gpFramebufferRenderbufferEXT = (C.GPFRAMEBUFFERRENDERBUFFEREXT)(c.getProcAddress("glFramebufferRenderbufferEXT"))
+	c.gpFramebufferTexture2DEXT = (C.GPFRAMEBUFFERTEXTURE2DEXT)(c.getProcAddress("glFramebufferTexture2DEXT"))
+	c.gpGenBuffers = (C.GPGENBUFFERS)(c.getProcAddress("glGenBuffers"))
 	if c.gpGenBuffers == nil {
 		return errors.New("gl: glGenBuffers is missing")
 	}
-	c.gpGenFramebuffersEXT = (C.GPGENFRAMEBUFFERSEXT)(getProcAddress("glGenFramebuffersEXT"))
-	c.gpGenRenderbuffersEXT = (C.GPGENRENDERBUFFERSEXT)(getProcAddress("glGenRenderbuffersEXT"))
-	c.gpGenTextures = (C.GPGENTEXTURES)(getProcAddress("glGenTextures"))
+	c.gpGenFramebuffersEXT = (C.GPGENFRAMEBUFFERSEXT)(c.getProcAddress("glGenFramebuffersEXT"))
+	c.gpGenRenderbuffersEXT = (C.GPGENRENDERBUFFERSEXT)(c.getProcAddress("glGenRenderbuffersEXT"))
+	c.gpGenTextures = (C.GPGENTEXTURES)(c.getProcAddress("glGenTextures"))
 	if c.gpGenTextures == nil {
 		return errors.New("gl: glGenTextures is missing")
 	}
-	c.gpGetError = (C.GPGETERROR)(getProcAddress("glGetError"))
+	c.gpGetError = (C.GPGETERROR)(c.getProcAddress("glGetError"))
 	if c.gpGetError == nil {
 		return errors.New("gl: glGetError is missing")
 	}
-	c.gpGetIntegerv = (C.GPGETINTEGERV)(getProcAddress("glGetIntegerv"))
+	c.gpGetIntegerv = (C.GPGETINTEGERV)(c.getProcAddress("glGetIntegerv"))
 	if c.gpGetIntegerv == nil {
 		return errors.New("gl: glGetIntegerv is missing")
 	}
-	c.gpGetProgramInfoLog = (C.GPGETPROGRAMINFOLOG)(getProcAddress("glGetProgramInfoLog"))
+	c.gpGetProgramInfoLog = (C.GPGETPROGRAMINFOLOG)(c.getProcAddress("glGetProgramInfoLog"))
 	if c.gpGetProgramInfoLog == nil {
 		return errors.New("gl: glGetProgramInfoLog is missing")
 	}
-	c.gpGetProgramiv = (C.GPGETPROGRAMIV)(getProcAddress("glGetProgramiv"))
+	c.gpGetProgramiv = (C.GPGETPROGRAMIV)(c.getProcAddress("glGetProgramiv"))
 	if c.gpGetProgramiv == nil {
 		return errors.New("gl: glGetProgramiv is missing")
 	}
-	c.gpGetShaderInfoLog = (C.GPGETSHADERINFOLOG)(getProcAddress("glGetShaderInfoLog"))
+	c.gpGetShaderInfoLog = (C.GPGETSHADERINFOLOG)(c.getProcAddress("glGetShaderInfoLog"))
 	if c.gpGetShaderInfoLog == nil {
 		return errors.New("gl: glGetShaderInfoLog is missing")
 	}
-	c.gpGetShaderiv = (C.GPGETSHADERIV)(getProcAddress("glGetShaderiv"))
+	c.gpGetShaderiv = (C.GPGETSHADERIV)(c.getProcAddress("glGetShaderiv"))
 	if c.gpGetShaderiv == nil {
 		return errors.New("gl: glGetShaderiv is missing")
 	}
-	c.gpGetUniformLocation = (C.GPGETUNIFORMLOCATION)(getProcAddress("glGetUniformLocation"))
+	c.gpGetUniformLocation = (C.GPGETUNIFORMLOCATION)(c.getProcAddress("glGetUniformLocation"))
 	if c.gpGetUniformLocation == nil {
 		return errors.New("gl: glGetUniformLocation is missing")
 	}
-	c.gpIsFramebufferEXT = (C.GPISFRAMEBUFFEREXT)(getProcAddress("glIsFramebufferEXT"))
-	c.gpIsProgram = (C.GPISPROGRAM)(getProcAddress("glIsProgram"))
+	c.gpIsFramebufferEXT = (C.GPISFRAMEBUFFEREXT)(c.getProcAddress("glIsFramebufferEXT"))
+	c.gpIsProgram = (C.GPISPROGRAM)(c.getProcAddress("glIsProgram"))
 	if c.gpIsProgram == nil {
 		return errors.New("gl: glIsProgram is missing")
 	}
-	c.gpIsRenderbufferEXT = (C.GPISRENDERBUFFEREXT)(getProcAddress("glIsRenderbufferEXT"))
-	c.gpIsTexture = (C.GPISTEXTURE)(getProcAddress("glIsTexture"))
+	c.gpIsRenderbufferEXT = (C.GPISRENDERBUFFEREXT)(c.getProcAddress("glIsRenderbufferEXT"))
+	c.gpIsTexture = (C.GPISTEXTURE)(c.getProcAddress("glIsTexture"))
 	if c.gpIsTexture == nil {
 		return errors.New("gl: glIsTexture is missing")
 	}
-	c.gpLinkProgram = (C.GPLINKPROGRAM)(getProcAddress("glLinkProgram"))
+	c.gpLinkProgram = (C.GPLINKPROGRAM)(c.getProcAddress("glLinkProgram"))
 	if c.gpLinkProgram == nil {
 		return errors.New("gl: glLinkProgram is missing")
 	}
-	c.gpPixelStorei = (C.GPPIXELSTOREI)(getProcAddress("glPixelStorei"))
+	c.gpPixelStorei = (C.GPPIXELSTOREI)(c.getProcAddress("glPixelStorei"))
 	if c.gpPixelStorei == nil {
 		return errors.New("gl: glPixelStorei is missing")
 	}
-	c.gpReadPixels = (C.GPREADPIXELS)(getProcAddress("glReadPixels"))
+	c.gpReadPixels = (C.GPREADPIXELS)(c.getProcAddress("glReadPixels"))
 	if c.gpReadPixels == nil {
 		return errors.New("gl: glReadPixels is missing")
 	}
-	c.gpRenderbufferStorageEXT = (C.GPRENDERBUFFERSTORAGEEXT)(getProcAddress("glRenderbufferStorageEXT"))
-	c.gpScissor = (C.GPSCISSOR)(getProcAddress("glScissor"))
+	c.gpRenderbufferStorageEXT = (C.GPRENDERBUFFERSTORAGEEXT)(c.getProcAddress("glRenderbufferStorageEXT"))
+	c.gpScissor = (C.GPSCISSOR)(c.getProcAddress("glScissor"))
 	if c.gpScissor == nil {
 		return errors.New("gl: glScissor is missing")
 	}
-	c.gpShaderSource = (C.GPSHADERSOURCE)(getProcAddress("glShaderSource"))
+	c.gpShaderSource = (C.GPSHADERSOURCE)(c.getProcAddress("glShaderSource"))
 	if c.gpShaderSource == nil {
 		return errors.New("gl: glShaderSource is missing")
 	}
-	c.gpStencilFunc = (C.GPSTENCILFUNC)(getProcAddress("glStencilFunc"))
+	c.gpStencilFunc = (C.GPSTENCILFUNC)(c.getProcAddress("glStencilFunc"))
 	if c.gpStencilFunc == nil {
 		return errors.New("gl: glStencilFunc is missing")
 	}
-	c.gpStencilOp = (C.GPSTENCILOP)(getProcAddress("glStencilOp"))
+	c.gpStencilOp = (C.GPSTENCILOP)(c.getProcAddress("glStencilOp"))
 	if c.gpStencilOp == nil {
 		return errors.New("gl: glStencilOp is missing")
 	}
-	c.gpTexImage2D = (C.GPTEXIMAGE2D)(getProcAddress("glTexImage2D"))
+	c.gpTexImage2D = (C.GPTEXIMAGE2D)(c.getProcAddress("glTexImage2D"))
 	if c.gpTexImage2D == nil {
 		return errors.New("gl: glTexImage2D is missing")
 	}
-	c.gpTexParameteri = (C.GPTEXPARAMETERI)(getProcAddress("glTexParameteri"))
+	c.gpTexParameteri = (C.GPTEXPARAMETERI)(c.getProcAddress("glTexParameteri"))
 	if c.gpTexParameteri == nil {
 		return errors.New("gl: glTexParameteri is missing")
 	}
-	c.gpTexSubImage2D = (C.GPTEXSUBIMAGE2D)(getProcAddress("glTexSubImage2D"))
+	c.gpTexSubImage2D = (C.GPTEXSUBIMAGE2D)(c.getProcAddress("glTexSubImage2D"))
 	if c.gpTexSubImage2D == nil {
 		return errors.New("gl: glTexSubImage2D is missing")
 	}
-	c.gpUniform1fv = (C.GPUNIFORM1FV)(getProcAddress("glUniform1fv"))
+	c.gpUniform1fv = (C.GPUNIFORM1FV)(c.getProcAddress("glUniform1fv"))
 	if c.gpUniform1fv == nil {
 		return errors.New("gl: glUniform1fv is missing")
 	}
-	c.gpUniform1i = (C.GPUNIFORM1I)(getProcAddress("glUniform1i"))
+	c.gpUniform1i = (C.GPUNIFORM1I)(c.getProcAddress("glUniform1i"))
 	if c.gpUniform1i == nil {
 		return errors.New("gl: glUniform1i is missing")
 	}
-	c.gpUniform1iv = (C.GPUNIFORM1IV)(getProcAddress("glUniform1iv"))
+	c.gpUniform1iv = (C.GPUNIFORM1IV)(c.getProcAddress("glUniform1iv"))
 	if c.gpUniform1iv == nil {
 		return errors.New("gl: glUniform1iv is missing")
 	}
-	c.gpUniform2fv = (C.GPUNIFORM2FV)(getProcAddress("glUniform2fv"))
+	c.gpUniform2fv = (C.GPUNIFORM2FV)(c.getProcAddress("glUniform2fv"))
 	if c.gpUniform2fv == nil {
 		return errors.New("gl: glUniform2fv is missing")
 	}
-	c.gpUniform3fv = (C.GPUNIFORM3FV)(getProcAddress("glUniform3fv"))
+	c.gpUniform3fv = (C.GPUNIFORM3FV)(c.getProcAddress("glUniform3fv"))
 	if c.gpUniform3fv == nil {
 		return errors.New("gl: glUniform3fv is missing")
 	}
-	c.gpUniform4fv = (C.GPUNIFORM4FV)(getProcAddress("glUniform4fv"))
+	c.gpUniform4fv = (C.GPUNIFORM4FV)(c.getProcAddress("glUniform4fv"))
 	if c.gpUniform4fv == nil {
 		return errors.New("gl: glUniform4fv is missing")
 	}
-	c.gpUniformMatrix2fv = (C.GPUNIFORMMATRIX2FV)(getProcAddress("glUniformMatrix2fv"))
+	c.gpUniformMatrix2fv = (C.GPUNIFORMMATRIX2FV)(c.getProcAddress("glUniformMatrix2fv"))
 	if c.gpUniformMatrix2fv == nil {
 		return errors.New("gl: glUniformMatrix2fv is missing")
 	}
-	c.gpUniformMatrix3fv = (C.GPUNIFORMMATRIX3FV)(getProcAddress("glUniformMatrix3fv"))
+	c.gpUniformMatrix3fv = (C.GPUNIFORMMATRIX3FV)(c.getProcAddress("glUniformMatrix3fv"))
 	if c.gpUniformMatrix3fv == nil {
 		return errors.New("gl: glUniformMatrix3fv is missing")
 	}
-	c.gpUniformMatrix4fv = (C.GPUNIFORMMATRIX4FV)(getProcAddress("glUniformMatrix4fv"))
+	c.gpUniformMatrix4fv = (C.GPUNIFORMMATRIX4FV)(c.getProcAddress("glUniformMatrix4fv"))
 	if c.gpUniformMatrix4fv == nil {
 		return errors.New("gl: glUniformMatrix4fv is missing")
 	}
-	c.gpUseProgram = (C.GPUSEPROGRAM)(getProcAddress("glUseProgram"))
+	c.gpUseProgram = (C.GPUSEPROGRAM)(c.getProcAddress("glUseProgram"))
 	if c.gpUseProgram == nil {
 		return errors.New("gl: glUseProgram is missing")
 	}
-	c.gpVertexAttribPointer = (C.GPVERTEXATTRIBPOINTER)(getProcAddress("glVertexAttribPointer"))
+	c.gpVertexAttribPointer = (C.GPVERTEXATTRIBPOINTER)(c.getProcAddress("glVertexAttribPointer"))
 	if c.gpVertexAttribPointer == nil {
 		return errors.New("gl: glVertexAttribPointer is missing")
 	}
-	c.gpViewport = (C.GPVIEWPORT)(getProcAddress("glViewport"))
+	c.gpViewport = (C.GPVIEWPORT)(c.getProcAddress("glViewport"))
 	if c.gpViewport == nil {
 		return errors.New("gl: glViewport is missing")
 	}

internal/graphicsdriver/opengl/gl/default_purego.go

@@ -94,10 +94,16 @@ type defaultContext struct {
 	gpUseProgram                 uintptr
 	gpVertexAttribPointer        uintptr
 	gpViewport                   uintptr
+
+	isES bool
 }
 
-func NewDefaultContext() Context {
-	return &defaultContext{}
+func NewDefaultContext() (Context, error) {
+	ctx := &defaultContext{}
+	if err := ctx.init(); err != nil {
+		return nil, err
+	}
+	return ctx, nil
 }
 
 func boolToInt(b bool) int {
@@ -108,7 +114,7 @@ func boolToInt(b bool) int {
 }
 
 func (c *defaultContext) IsES() bool {
-	return isES
+	return c.isES
 }
 
 func (c *defaultContext) ActiveTexture(texture uint32) {
@@ -440,244 +446,244 @@ func (c *defaultContext) Viewport(x int32, y int32, width int32, height int32) {
 	purego.SyscallN(c.gpViewport, uintptr(x), uintptr(y), uintptr(width), uintptr(height))
 }
 
-func (c *defaultContext) Init() error {
-	c.gpActiveTexture = getProcAddress("glActiveTexture")
+func (c *defaultContext) LoadFunctions() error {
+	c.gpActiveTexture = c.getProcAddress("glActiveTexture")
 	if c.gpActiveTexture == 0 {
 		return errors.New("gl: glActiveTexture is missing")
 	}
-	c.gpAttachShader = getProcAddress("glAttachShader")
+	c.gpAttachShader = c.getProcAddress("glAttachShader")
 	if c.gpAttachShader == 0 {
 		return errors.New("gl: glAttachShader is missing")
 	}
-	c.gpBindAttribLocation = getProcAddress("glBindAttribLocation")
+	c.gpBindAttribLocation = c.getProcAddress("glBindAttribLocation")
 	if c.gpBindAttribLocation == 0 {
 		return errors.New("gl: glBindAttribLocation is missing")
 	}
-	c.gpBindBuffer = getProcAddress("glBindBuffer")
+	c.gpBindBuffer = c.getProcAddress("glBindBuffer")
 	if c.gpBindBuffer == 0 {
 		return errors.New("gl: glBindBuffer is missing")
 	}
-	c.gpBindFramebufferEXT = getProcAddress("glBindFramebufferEXT")
-	c.gpBindRenderbufferEXT = getProcAddress("glBindRenderbufferEXT")
-	c.gpBindTexture = getProcAddress("glBindTexture")
+	c.gpBindFramebufferEXT = c.getProcAddress("glBindFramebufferEXT")
+	c.gpBindRenderbufferEXT = c.getProcAddress("glBindRenderbufferEXT")
+	c.gpBindTexture = c.getProcAddress("glBindTexture")
 	if c.gpBindTexture == 0 {
 		return errors.New("gl: glBindTexture is missing")
 	}
-	c.gpBlendEquationSeparate = getProcAddress("glBlendEquationSeparate")
+	c.gpBlendEquationSeparate = c.getProcAddress("glBlendEquationSeparate")
 	if c.gpBlendEquationSeparate == 0 {
 		return errors.New("gl: glBlendEquationSeparate is missing")
 	}
-	c.gpBlendFuncSeparate = getProcAddress("glBlendFuncSeparate")
+	c.gpBlendFuncSeparate = c.getProcAddress("glBlendFuncSeparate")
 	if c.gpBlendFuncSeparate == 0 {
 		return errors.New("gl: glBlendFuncSeparate is missing")
 	}
-	c.gpBufferData = getProcAddress("glBufferData")
+	c.gpBufferData = c.getProcAddress("glBufferData")
 	if c.gpBufferData == 0 {
 		return errors.New("gl: glBufferData is missing")
 	}
-	c.gpBufferSubData = getProcAddress("glBufferSubData")
+	c.gpBufferSubData = c.getProcAddress("glBufferSubData")
 	if c.gpBufferSubData == 0 {
 		return errors.New("gl: glBufferSubData is missing")
 	}
-	c.gpCheckFramebufferStatusEXT = getProcAddress("glCheckFramebufferStatusEXT")
-	c.gpClear = getProcAddress("glClear")
+	c.gpCheckFramebufferStatusEXT = c.getProcAddress("glCheckFramebufferStatusEXT")
+	c.gpClear = c.getProcAddress("glClear")
 	if c.gpClear == 0 {
 		return errors.New("gl: glClear is missing")
 	}
-	c.gpColorMask = getProcAddress("glColorMask")
+	c.gpColorMask = c.getProcAddress("glColorMask")
 	if c.gpColorMask == 0 {
 		return errors.New("gl: glColorMask is missing")
 	}
-	c.gpCompileShader = getProcAddress("glCompileShader")
+	c.gpCompileShader = c.getProcAddress("glCompileShader")
 	if c.gpCompileShader == 0 {
 		return errors.New("gl: glCompileShader is missing")
 	}
-	c.gpCreateProgram = getProcAddress("glCreateProgram")
+	c.gpCreateProgram = c.getProcAddress("glCreateProgram")
 	if c.gpCreateProgram == 0 {
 		return errors.New("gl: glCreateProgram is missing")
 	}
-	c.gpCreateShader = getProcAddress("glCreateShader")
+	c.gpCreateShader = c.getProcAddress("glCreateShader")
 	if c.gpCreateShader == 0 {
 		return errors.New("gl: glCreateShader is missing")
 	}
-	c.gpDeleteBuffers = getProcAddress("glDeleteBuffers")
+	c.gpDeleteBuffers = c.getProcAddress("glDeleteBuffers")
 	if c.gpDeleteBuffers == 0 {
 		return errors.New("gl: glDeleteBuffers is missing")
 	}
-	c.gpDeleteFramebuffersEXT = getProcAddress("glDeleteFramebuffersEXT")
-	c.gpDeleteProgram = getProcAddress("glDeleteProgram")
+	c.gpDeleteFramebuffersEXT = c.getProcAddress("glDeleteFramebuffersEXT")
+	c.gpDeleteProgram = c.getProcAddress("glDeleteProgram")
 	if c.gpDeleteProgram == 0 {
 		return errors.New("gl: glDeleteProgram is missing")
 	}
-	c.gpDeleteRenderbuffersEXT = getProcAddress("glDeleteRenderbuffersEXT")
-	c.gpDeleteShader = getProcAddress("glDeleteShader")
+	c.gpDeleteRenderbuffersEXT = c.getProcAddress("glDeleteRenderbuffersEXT")
+	c.gpDeleteShader = c.getProcAddress("glDeleteShader")
 	if c.gpDeleteShader == 0 {
 		return errors.New("gl: glDeleteShader is missing")
 	}
-	c.gpDeleteTextures = getProcAddress("glDeleteTextures")
+	c.gpDeleteTextures = c.getProcAddress("glDeleteTextures")
 	if c.gpDeleteTextures == 0 {
 		return errors.New("gl: glDeleteTextures is missing")
 	}
-	c.gpDisable = getProcAddress("glDisable")
+	c.gpDisable = c.getProcAddress("glDisable")
 	if c.gpDisable == 0 {
 		return errors.New("gl: glDisable is missing")
 	}
-	c.gpDisableVertexAttribArray = getProcAddress("glDisableVertexAttribArray")
+	c.gpDisableVertexAttribArray = c.getProcAddress("glDisableVertexAttribArray")
 	if c.gpDisableVertexAttribArray == 0 {
 		return errors.New("gl: glDisableVertexAttribArray is missing")
 	}
-	c.gpDrawElements = getProcAddress("glDrawElements")
+	c.gpDrawElements = c.getProcAddress("glDrawElements")
 	if c.gpDrawElements == 0 {
 		return errors.New("gl: glDrawElements is missing")
 	}
-	c.gpEnable = getProcAddress("glEnable")
+	c.gpEnable = c.getProcAddress("glEnable")
 	if c.gpEnable == 0 {
 		return errors.New("gl: glEnable is missing")
 	}
-	c.gpEnableVertexAttribArray = getProcAddress("glEnableVertexAttribArray")
+	c.gpEnableVertexAttribArray = c.getProcAddress("glEnableVertexAttribArray")
 	if c.gpEnableVertexAttribArray == 0 {
 		return errors.New("gl: glEnableVertexAttribArray is missing")
 	}
-	c.gpFlush = getProcAddress("glFlush")
+	c.gpFlush = c.getProcAddress("glFlush")
 	if c.gpFlush == 0 {
 		return errors.New("gl: glFlush is missing")
 	}
-	c.gpFramebufferRenderbufferEXT = getProcAddress("glFramebufferRenderbufferEXT")
-	c.gpFramebufferTexture2DEXT = getProcAddress("glFramebufferTexture2DEXT")
-	c.gpGenBuffers = getProcAddress("glGenBuffers")
+	c.gpFramebufferRenderbufferEXT = c.getProcAddress("glFramebufferRenderbufferEXT")
+	c.gpFramebufferTexture2DEXT = c.getProcAddress("glFramebufferTexture2DEXT")
+	c.gpGenBuffers = c.getProcAddress("glGenBuffers")
 	if c.gpGenBuffers == 0 {
 		return errors.New("gl: glGenBuffers is missing")
 	}
-	c.gpGenFramebuffersEXT = getProcAddress("glGenFramebuffersEXT")
-	c.gpGenRenderbuffersEXT = getProcAddress("glGenRenderbuffersEXT")
-	c.gpGenTextures = getProcAddress("glGenTextures")
+	c.gpGenFramebuffersEXT = c.getProcAddress("glGenFramebuffersEXT")
+	c.gpGenRenderbuffersEXT = c.getProcAddress("glGenRenderbuffersEXT")
+	c.gpGenTextures = c.getProcAddress("glGenTextures")
 	if c.gpGenTextures == 0 {
 		return errors.New("gl: glGenTextures is missing")
 	}
-	c.gpGetError = getProcAddress("glGetError")
+	c.gpGetError = c.getProcAddress("glGetError")
 	if c.gpGetError == 0 {
 		return errors.New("gl: glGetError is missing")
 	}
-	c.gpGetIntegerv = getProcAddress("glGetIntegerv")
+	c.gpGetIntegerv = c.getProcAddress("glGetIntegerv")
 	if c.gpGetIntegerv == 0 {
 		return errors.New("gl: glGetIntegerv is missing")
 	}
-	c.gpGetProgramInfoLog = getProcAddress("glGetProgramInfoLog")
+	c.gpGetProgramInfoLog = c.getProcAddress("glGetProgramInfoLog")
 	if c.gpGetProgramInfoLog == 0 {
 		return errors.New("gl: glGetProgramInfoLog is missing")
 	}
-	c.gpGetProgramiv = getProcAddress("glGetProgramiv")
+	c.gpGetProgramiv = c.getProcAddress("glGetProgramiv")
 	if c.gpGetProgramiv == 0 {
 		return errors.New("gl: glGetProgramiv is missing")
 	}
-	c.gpGetShaderInfoLog = getProcAddress("glGetShaderInfoLog")
+	c.gpGetShaderInfoLog = c.getProcAddress("glGetShaderInfoLog")
 	if c.gpGetShaderInfoLog == 0 {
 		return errors.New("gl: glGetShaderInfoLog is missing")
 	}
-	c.gpGetShaderiv = getProcAddress("glGetShaderiv")
+	c.gpGetShaderiv = c.getProcAddress("glGetShaderiv")
 	if c.gpGetShaderiv == 0 {
 		return errors.New("gl: glGetShaderiv is missing")
 	}
-	c.gpGetUniformLocation = getProcAddress("glGetUniformLocation")
+	c.gpGetUniformLocation = c.getProcAddress("glGetUniformLocation")
 	if c.gpGetUniformLocation == 0 {
 		return errors.New("gl: glGetUniformLocation is missing")
 	}
-	c.gpIsFramebufferEXT = getProcAddress("glIsFramebufferEXT")
-	c.gpIsProgram = getProcAddress("glIsProgram")
+	c.gpIsFramebufferEXT = c.getProcAddress("glIsFramebufferEXT")
+	c.gpIsProgram = c.getProcAddress("glIsProgram")
 	if c.gpIsProgram == 0 {
 		return errors.New("gl: glIsProgram is missing")
 	}
-	c.gpIsRenderbufferEXT = getProcAddress("glIsRenderbufferEXT")
-	c.gpIsTexture = getProcAddress("glIsTexture")
+	c.gpIsRenderbufferEXT = c.getProcAddress("glIsRenderbufferEXT")
+	c.gpIsTexture = c.getProcAddress("glIsTexture")
 	if c.gpIsTexture == 0 {
 		return errors.New("gl: glIsTexture is missing")
 	}
-	c.gpLinkProgram = getProcAddress("glLinkProgram")
+	c.gpLinkProgram = c.getProcAddress("glLinkProgram")
 	if c.gpLinkProgram == 0 {
 		return errors.New("gl: glLinkProgram is missing")
 	}
-	c.gpPixelStorei = getProcAddress("glPixelStorei")
+	c.gpPixelStorei = c.getProcAddress("glPixelStorei")
 	if c.gpPixelStorei == 0 {
 		return errors.New("gl: glPixelStorei is missing")
 	}
-	c.gpReadPixels = getProcAddress("glReadPixels")
+	c.gpReadPixels = c.getProcAddress("glReadPixels")
 	if c.gpReadPixels == 0 {
 		return errors.New("gl: glReadPixels is missing")
 	}
-	c.gpRenderbufferStorageEXT = getProcAddress("glRenderbufferStorageEXT")
-	c.gpScissor = getProcAddress("glScissor")
+	c.gpRenderbufferStorageEXT = c.getProcAddress("glRenderbufferStorageEXT")
+	c.gpScissor = c.getProcAddress("glScissor")
 	if c.gpScissor == 0 {
 		return errors.New("gl: glScissor is missing")
 	}
-	c.gpShaderSource = getProcAddress("glShaderSource")
+	c.gpShaderSource = c.getProcAddress("glShaderSource")
 	if c.gpShaderSource == 0 {
 		return errors.New("gl: glShaderSource is missing")
 	}
-	c.gpStencilFunc = getProcAddress("glStencilFunc")
+	c.gpStencilFunc = c.getProcAddress("glStencilFunc")
 	if c.gpStencilFunc == 0 {
 		return errors.New("gl: glStencilFunc is missing")
 	}
-	c.gpStencilOp = getProcAddress("glStencilOp")
+	c.gpStencilOp = c.getProcAddress("glStencilOp")
 	if c.gpStencilOp == 0 {
 		return errors.New("gl: glStencilOp is missing")
 	}
-	c.gpTexImage2D = getProcAddress("glTexImage2D")
+	c.gpTexImage2D = c.getProcAddress("glTexImage2D")
 	if c.gpTexImage2D == 0 {
 		return errors.New("gl: glTexImage2D is missing")
 	}
-	c.gpTexParameteri = getProcAddress("glTexParameteri")
+	c.gpTexParameteri = c.getProcAddress("glTexParameteri")
 	if c.gpTexParameteri == 0 {
 		return errors.New("gl: glTexParameteri is missing")
 	}
-	c.gpTexSubImage2D = getProcAddress("glTexSubImage2D")
+	c.gpTexSubImage2D = c.getProcAddress("glTexSubImage2D")
 	if c.gpTexSubImage2D == 0 {
 		return errors.New("gl: glTexSubImage2D is missing")
 	}
-	c.gpUniform1fv = getProcAddress("glUniform1fv")
+	c.gpUniform1fv = c.getProcAddress("glUniform1fv")
 	if c.gpUniform1fv == 0 {
 		return errors.New("gl: glUniform1fv is missing")
 	}
-	c.gpUniform1i = getProcAddress("glUniform1i")
+	c.gpUniform1i = c.getProcAddress("glUniform1i")
 	if c.gpUniform1i == 0 {
 		return errors.New("gl: glUniform1i is missing")
 	}
-	c.gpUniform1iv = getProcAddress("glUniform1iv")
+	c.gpUniform1iv = c.getProcAddress("glUniform1iv")
 	if c.gpUniform1iv == 0 {
 		return errors.New("gl: glUniform1iv is missing")
 	}
-	c.gpUniform2fv = getProcAddress("glUniform2fv")
+	c.gpUniform2fv = c.getProcAddress("glUniform2fv")
 	if c.gpUniform2fv == 0 {
 		return errors.New("gl: glUniform2fv is missing")
 	}
-	c.gpUniform3fv = getProcAddress("glUniform3fv")
+	c.gpUniform3fv = c.getProcAddress("glUniform3fv")
 	if c.gpUniform3fv == 0 {
 		return errors.New("gl: glUniform3fv is missing")
 	}
-	c.gpUniform4fv = getProcAddress("glUniform4fv")
+	c.gpUniform4fv = c.getProcAddress("glUniform4fv")
 	if c.gpUniform4fv == 0 {
 		return errors.New("gl: glUniform4fv is missing")
 	}
-	c.gpUniformMatrix2fv = getProcAddress("glUniformMatrix2fv")
+	c.gpUniformMatrix2fv = c.getProcAddress("glUniformMatrix2fv")
 	if c.gpUniformMatrix2fv == 0 {
 		return errors.New("gl: glUniformMatrix2fv is missing")
 	}
-	c.gpUniformMatrix3fv = getProcAddress("glUniformMatrix3fv")
+	c.gpUniformMatrix3fv = c.getProcAddress("glUniformMatrix3fv")
 	if c.gpUniformMatrix3fv == 0 {
 		return errors.New("gl: glUniformMatrix3fv is missing")
 	}
-	c.gpUniformMatrix4fv = getProcAddress("glUniformMatrix4fv")
+	c.gpUniformMatrix4fv = c.getProcAddress("glUniformMatrix4fv")
 	if c.gpUniformMatrix4fv == 0 {
 		return errors.New("gl: glUniformMatrix4fv is missing")
 	}
-	c.gpUseProgram = getProcAddress("glUseProgram")
+	c.gpUseProgram = c.getProcAddress("glUseProgram")
 	if c.gpUseProgram == 0 {
 		return errors.New("gl: glUseProgram is missing")
 	}
-	c.gpVertexAttribPointer = getProcAddress("glVertexAttribPointer")
+	c.gpVertexAttribPointer = c.getProcAddress("glVertexAttribPointer")
 	if c.gpVertexAttribPointer == 0 {
 		return errors.New("gl: glVertexAttribPointer is missing")
 	}
-	c.gpViewport = getProcAddress("glViewport")
+	c.gpViewport = c.getProcAddress("glViewport")
 	if c.gpViewport == 0 {
 		return errors.New("gl: glViewport is missing")
 	}

internal/graphicsdriver/opengl/gl/gomobile.go

@@ -35,7 +35,7 @@ func NewGomobileContext(ctx gl.Context) Context {
 	return &gomobileContext{ctx}
 }
 
-func (g *gomobileContext) Init() error {
+func (g *gomobileContext) LoadFunctions() error {
 	return nil
 }
 

internal/graphicsdriver/opengl/gl/interface.go

@@ -19,7 +19,7 @@ package gl
 // Context is basically the same as gomobile's gl.Context.
 // See https://pkg.go.dev/golang.org/x/mobile/gl#Context
 type Context interface {
-	Init() error
+	LoadFunctions() error
 	IsES() bool
 
 	ActiveTexture(texture uint32)

internal/graphicsdriver/opengl/gl/procaddr_darwin.go

@@ -15,23 +15,28 @@
 package gl
 
 import (
+	"fmt"
+
 	"github.com/ebitengine/purego"
 )
 
 var (
 	opengl uintptr
-	isES   bool
 )
 
-func init() {
+func (c *defaultContext) init() error {
 	opengl = purego.Dlopen("/System/Library/Frameworks/OpenGLES.framework/Versions/Current/OpenGLES", purego.RTLD_LAZY|purego.RTLD_GLOBAL)
 	if opengl != 0 {
-		isES = true
-		return
+		c.isES = true
+		return nil
 	}
 	opengl = purego.Dlopen("/System/Library/Frameworks/OpenGL.framework/Versions/Current/OpenGL", purego.RTLD_LAZY|purego.RTLD_GLOBAL)
+	if opengl != 0 {
+		return nil
+	}
+	return fmt.Errorf("gl: failed to load OpenGL.framework and OpenGLES.framework")
 }
 
-func getProcAddress(name string) uintptr {
+func (c *defaultContext) getProcAddress(name string) uintptr {
 	return purego.Dlsym(opengl, name)
 }

internal/graphicsdriver/opengl/gl/procaddr_gl.go

@@ -1,48 +0,0 @@
-// Copyright 2022 The Ebitengine Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-//go:build !android && !darwin && !js && !nintendosdk && !windows && !opengles
-
-package gl
-
-// #cgo LDFLAGS: -ldl
-//
-// #include <dlfcn.h>
-// #include <stdlib.h>
-//
-// static void* getProcAddress(const char* name) {
-//   static void* libGL;
-//   if (!libGL) {
-//     libGL = dlopen("libGL.so", RTLD_LAZY | RTLD_GLOBAL);
-//   }
-//   static void*(*glXGetProcAddress)(const char*);
-//   if (!glXGetProcAddress) {
-//     glXGetProcAddress = dlsym(libGL, "glXGetProcAddress");
-//     if (!glXGetProcAddress) {
-//       glXGetProcAddress = dlsym(libGL, "glXGetProcAddressARB");
-//     }
-//   }
-//   return glXGetProcAddress(name);
-// }
-import "C"
-
-import "unsafe"
-
-var isES = false
-
-func getProcAddress(namea string) unsafe.Pointer {
-	cname := C.CString(namea)
-	defer C.free(unsafe.Pointer(cname))
-	return C.getProcAddress(cname)
-}

internal/graphicsdriver/opengl/gl/procaddr_gles.go

@@ -1,48 +0,0 @@
-// Copyright 2022 The Ebitengine Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-//go:build !android && !darwin && !js && !nintendosdk && !windows && opengles
-
-package gl
-
-// #cgo LDFLAGS: -ldl
-//
-// #include <dlfcn.h>
-// #include <stdlib.h>
-//
-// static void* getProcAddress(const char* name) {
-//   static void* libGLES;
-//   if (!libGLES) {
-//     libGLES = dlopen("libGLESv2.so", RTLD_LAZY | RTLD_GLOBAL);
-//   }
-//   return dlsym(libGLES, name);
-// }
-import "C"
-
-import (
-	"strings"
-	"unsafe"
-)
-
-var isES = true
-
-func getProcAddress(namea string) unsafe.Pointer {
-	const ext = "EXT"
-	if strings.HasSuffix(namea, ext) {
-		namea = namea[:len(namea)-len(ext)]
-	}
-	cname := C.CString(namea)
-	defer C.free(unsafe.Pointer(cname))
-	return C.getProcAddress(cname)
-}

internal/graphicsdriver/opengl/gl/procaddr_nintendosdk.go

@@ -28,10 +28,12 @@ import "C"
 
 import "unsafe"
 
-var isES = false
+func (c *defaultContext) init() error {
+	return nil
+}
 
-func getProcAddress(namea string) unsafe.Pointer {
-	cname := C.CString(namea)
+func (c *defaultContext) getProcAddress(name string) unsafe.Pointer {
+	cname := C.CString(name)
 	defer C.free(unsafe.Pointer(cname))
 	return C.getProcAddress(cname)
 }

internal/graphicsdriver/opengl/gl/procaddr_others.go

@@ -0,0 +1,110 @@
+// Copyright 2022 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !android && !darwin && !js && !nintendosdk && !windows
+
+package gl
+
+// #cgo LDFLAGS: -ldl
+//
+// #include <dlfcn.h>
+// #include <stdlib.h>
+//
+// static void* libGL() {
+//   static void* so;
+//   if (!so) {
+//     so = dlopen("libGL.so", RTLD_LAZY | RTLD_GLOBAL);
+//   }
+//   return so;
+// }
+//
+// static void* libGLES() {
+//   static void* so;
+//   if (!so) {
+//     so = dlopen("libGLESv2.so", RTLD_LAZY | RTLD_GLOBAL);
+//   }
+//   return so;
+// }
+//
+// static void* getProcAddressGL(const char* name) {
+//   static void*(*glXGetProcAddress)(const char*);
+//   if (!glXGetProcAddress) {
+//     glXGetProcAddress = dlsym(libGL(), "glXGetProcAddress");
+//     if (!glXGetProcAddress) {
+//       glXGetProcAddress = dlsym(libGL(), "glXGetProcAddressARB");
+//     }
+//   }
+//   return glXGetProcAddress(name);
+// }
+//
+// static void* getProcAddressGLES(const char* name) {
+//   return dlsym(libGLES(), name);
+// }
+import "C"
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"unsafe"
+)
+
+func (c *defaultContext) init() error {
+	var preferES bool
+	for _, t := range strings.Split(os.Getenv("EBITENGINE_OPENGL"), ",") {
+		switch strings.TrimSpace(t) {
+		case "es":
+			preferES = true
+			break
+		}
+	}
+
+	// Try OpenGL first. OpenGL is preferrable as this doesn't cause context losts.
+	if !preferES {
+		if C.libGL() != nil {
+			return nil
+		}
+	}
+
+	// Try OpenGL ES.
+	if C.libGLES() != nil {
+		c.isES = true
+		return nil
+	}
+
+	return fmt.Errorf("gl: failed to load libGL.so and libGLES.so")
+}
+
+func (c *defaultContext) getProcAddress(name string) unsafe.Pointer {
+	if c.isES {
+		return getProcAddressGLES(name)
+	}
+	return getProcAddressGL(name)
+}
+
+func getProcAddressGL(name string) unsafe.Pointer {
+	cname := C.CString(name)
+	defer C.free(unsafe.Pointer(cname))
+	return C.getProcAddressGL(cname)
+}
+
+func getProcAddressGLES(name string) unsafe.Pointer {
+	const ext = "EXT"
+	if strings.HasSuffix(name, ext) {
+		name = name[:len(name)-len(ext)]
+	}
+	cname := C.CString(name)
+	defer C.free(unsafe.Pointer(cname))
+	return C.getProcAddressGLES(cname)
+}

internal/graphicsdriver/opengl/gl/procaddr_windows.go

@@ -24,10 +24,13 @@ import (
 var (
 	opengl32              = windows.NewLazySystemDLL("opengl32")
 	procWglGetProcAddress = opengl32.NewProc("wglGetProcAddress")
-	isES                  = false
 )
 
-func getProcAddress(namea string) uintptr {
+func (c *defaultContext) init() error {
+	return nil
+}
+
+func (c *defaultContext) getProcAddress(namea string) uintptr {
 	cname, err := windows.BytePtrFromString(namea)
 	if err != nil {
 		panic(err)

internal/graphicsdriver/opengl/graphics_default.go

@@ -31,7 +31,12 @@ func NewGraphics() (graphicsdriver.Graphics, error) {
 		return nil, fmt.Errorf("opengl: OpenGL is not supported on Xbox")
 	}
 
+	ctx, err := gl.NewDefaultContext()
+	if err != nil {
+		return nil, err
+	}
+
 	g := &Graphics{}
-	g.context.ctx = gl.NewDefaultContext()
+	g.context.ctx = ctx
 	return g, nil
 }

internal/graphicsdriver/opengl/graphics_mobile.go

@@ -30,7 +30,11 @@ func NewGraphics(context mgl.Context) (graphicsdriver.Graphics, error) {
 	if context != nil {
 		ctx = gl.NewGomobileContext(context.(mgl.Context))
 	} else {
-		ctx = gl.NewDefaultContext()
+		var err error
+		ctx, err = gl.NewDefaultContext()
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	g := &Graphics{}