improve error reporting; add GLError type

pixelgl/thread.go

@@ -1,7 +1,7 @@
 package pixelgl
 
 import (
-	"errors"
+	"fmt"
 	"runtime"
 
 	"github.com/go-gl/gl/v3.3-core/gl"
@@ -131,6 +131,28 @@ func DoValGLErr(f func() interface{}) (_ interface{}, gl error) {
 	return <-val, <-glerr
 }
 
+// GLError represents an error code generated by OpenGL.
+type GLError uint32
+
+// Error returns a human-readable textual representation of an OpenGL error.
+func (err GLError) Error() string {
+	if desc, ok := glErrors[uint32(err)]; ok {
+		return fmt.Sprintf("OpenGL error: %s", desc)
+	}
+	return fmt.Sprintf("OpenGL error: unknown error")
+}
+
+var glErrors = map[uint32]string{
+	gl.INVALID_ENUM:                  "invalid enum",
+	gl.INVALID_VALUE:                 "invalid value",
+	gl.INVALID_OPERATION:             "invalid operation",
+	gl.STACK_OVERFLOW:                "stack overflow",
+	gl.STACK_UNDERFLOW:               "stack underflow",
+	gl.OUT_OF_MEMORY:                 "out of memory",
+	gl.INVALID_FRAMEBUFFER_OPERATION: "invalid framebuffer operation",
+	gl.CONTEXT_LOST:                  "context lost",
+}
+
 // getLastGLErr returns (and consumes) the last error generated by OpenGL.
 // Don't use outside DoGLErr, DoErrGLErr and DoValGLErr.
 func getLastGLErr() error {
@@ -141,24 +163,5 @@ func getLastGLErr() error {
 	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")
-	}
+	return GLError(err)
 }