encapsulate error handling

add functions DoGLErr, DoErrGLErr and DoValGLErr to handle OpenGL errors

pixelgl/error.go

@@ -1,41 +0,0 @@
-package pixelgl
-
-import (
-	"github.com/go-gl/gl/v3.3-core/gl"
-	"github.com/pkg/errors"
-)
-
-// getLastError returns (and consumes) the last error generated by OpenGL inside the current Do, DoErr or DoVal.
-// If no error has been generated, this function returns nil.
-//
-// Call this function only inside the OpenGL thread (Do, DoErr or DoVal function). It's not guaranteed
-// to work correctly outside of it, because the thread swallows extra unchecked errors.
-func getLastError() error {
-	err := uint32(gl.NO_ERROR)
-	for e := gl.GetError(); e != gl.NO_ERROR; e = gl.GetError() {
-		err = e
-	}
-	if err == gl.NO_ERROR {
-		return nil
-	}
-	switch err {
-	case gl.INVALID_ENUM:
-		return errors.New("invalid enum")
-	case gl.INVALID_VALUE:
-		return errors.New("invalid value")
-	case gl.INVALID_OPERATION:
-		return errors.New("invalid operation")
-	case gl.STACK_OVERFLOW:
-		return errors.New("stack overflow")
-	case gl.STACK_UNDERFLOW:
-		return errors.New("stack underflow")
-	case gl.OUT_OF_MEMORY:
-		return errors.New("out of memory")
-	case gl.INVALID_FRAMEBUFFER_OPERATION:
-		return errors.New("invalid framebuffer operation")
-	case gl.CONTEXT_LOST:
-		return errors.New("context lost")
-	default:
-		return errors.New("unknown error")
-	}
-}

pixelgl/texture.go

@@ -15,7 +15,7 @@ type Texture struct {
 // The pixels must be a sequence of RGBA values.
 func NewTexture(parent BeginEnder, width, height int, pixels []uint8) (*Texture, error) {
 	texture := &Texture{parent: parent}
-	err := DoErr(func() error {
+	err := DoGLErr(func() {
 		gl.GenTextures(1, &texture.tex)
 		gl.BindTexture(gl.TEXTURE_2D, texture.tex)
 
@@ -33,8 +33,6 @@ func NewTexture(parent BeginEnder, width, height int, pixels []uint8) (*Texture,
 		gl.GenerateMipmap(gl.TEXTURE_2D)
 
 		gl.BindTexture(gl.TEXTURE_2D, 0)
-
-		return getLastError()
 	})
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to create a texture")

pixelgl/thread.go

@@ -1,6 +1,11 @@
 package pixelgl
 
-import "runtime"
+import (
+	"errors"
+	"runtime"
+
+	"github.com/go-gl/gl/v2.1/gl"
+)
 
 // Due to the existance and usage of thread-local variables by OpenGL, it's recommended to
 // execute all OpenGL calls from a single dedicated thread. This file defines functions to make
@@ -16,7 +21,7 @@ func init() {
 	go func() {
 		runtime.LockOSThread()
 		for f := range callQueue {
-			getLastError() // swallow unchecked errors
+			getLastGLErr() // swallow unchecked errors
 			f()
 		}
 	}()
@@ -58,3 +63,67 @@ func DoVal(f func() interface{}) interface{} {
 	}
 	return <-val
 }
+
+// DoGLErr is same as Do, but also return an error generated by OpenGL.
+func DoGLErr(f func()) (gl error) {
+	glerr := make(chan error)
+	callQueue <- func() {
+		f()
+		glerr <- getLastGLErr()
+	}
+	return <-glerr
+}
+
+// DoErrGLErr is same as DoErr, but also returns an error generated by OpenGL.
+func DoErrGLErr(f func() error) (_, gl error) {
+	err := make(chan error)
+	glerr := make(chan error)
+	callQueue <- func() {
+		err <- f()
+		glerr <- getLastGLErr()
+	}
+	return <-err, <-glerr
+}
+
+// DoValGLErr is same as DoVal, but also returns an error generated by OpenGL.
+func DoValGLErr(f func() interface{}) (_ interface{}, gl error) {
+	val := make(chan interface{})
+	glerr := make(chan error)
+	callQueue <- func() {
+		val <- f()
+		glerr <- getLastGLErr()
+	}
+	return <-val, <-glerr
+}
+
+// getLastGLErr returns (and consumes) the last error generated by OpenGL.
+// Don't use outside DoGLErr, DoErrGLErr and DoValGLErr.
+func getLastGLErr() error {
+	err := uint32(gl.NO_ERROR)
+	for e := gl.GetError(); e != gl.NO_ERROR; e = gl.GetError() {
+		err = e
+	}
+	if err == gl.NO_ERROR {
+		return nil
+	}
+	switch err {
+	case gl.INVALID_ENUM:
+		return errors.New("invalid enum")
+	case gl.INVALID_VALUE:
+		return errors.New("invalid value")
+	case gl.INVALID_OPERATION:
+		return errors.New("invalid operation")
+	case gl.STACK_OVERFLOW:
+		return errors.New("stack overflow")
+	case gl.STACK_UNDERFLOW:
+		return errors.New("stack underflow")
+	case gl.OUT_OF_MEMORY:
+		return errors.New("out of memory")
+	case gl.INVALID_FRAMEBUFFER_OPERATION:
+		return errors.New("invalid framebuffer operation")
+	case gl.CONTEXT_LOST:
+		return errors.New("context lost")
+	default:
+		return errors.New("unknown error")
+	}
+}

pixelgl/vertex.go

@@ -105,7 +105,7 @@ func NewVertexArray(parent BeginEnder, format VertexFormat, mode VertexDrawMode,
 		format: format,
 		mode:   mode,
 	}
-	err := DoErr(func() error {
+	err := DoGLErr(func() {
 		gl.GenVertexArrays(1, &va.vao)
 		gl.BindVertexArray(va.vao)
 
@@ -132,8 +132,6 @@ func NewVertexArray(parent BeginEnder, format VertexFormat, mode VertexDrawMode,
 
 		gl.BindBuffer(gl.ARRAY_BUFFER, 0)
 		gl.BindVertexArray(0)
-
-		return getLastError()
 	})
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to create a vertex array")
@@ -173,11 +171,10 @@ func (va *VertexArray) Draw() {
 //
 // Offset is not a number of bytes, instead, it's an index in the array.
 func (va *VertexArray) UpdateData(offset int, data []float64) error {
-	err := DoErr(func() error {
+	err := DoGLErr(func() {
 		gl.BindBuffer(gl.ARRAY_BUFFER, va.vbo)
 		gl.BufferSubData(gl.ARRAY_BUFFER, 8*offset, 8*len(data), gl.Ptr(data))
 		gl.BindBuffer(gl.ARRAY_BUFFER, 0)
-		return getLastError()
 	})
 	if err != nil {
 		return errors.Wrap(err, "failed to update vertex array")