Add glGetError() and gluErrorString().

gl-error.c

@@ -2,6 +2,7 @@
 
    libgl/gl-error.c
    Copyright (C) 2014 Josh Pearson
+   Copyright (C) 2016 Lawrence Sebald
 
     KOS Open GL State Machine Error Code Implementation.
 */
@@ -17,12 +18,27 @@
 #define KOS_GL_INVALID_VALUE      (1<<3)
 
 static GLsizei KOS_GL_ERROR_CODE;
+static GLenum gl_last_error = GL_NO_ERROR;
 
 static char KOS_GL_ERROR_FUNCTION[64] = { '\0' };
 
+/* Quoth the GL Spec:
+    When an error occurs, the error flag is set to the appropriate error code
+    value. No other errors are recorded until glGetError is called, the error
+    code is returned, and the flag is reset to GL_NO_ERROR.
+
+   So, we only record an error here if the error code is currently unset.
+   Nothing in the spec requires recording multiple error flags, although it is
+   allowed by the spec. We take the easy way out for now. */
+static void set_err_flag(GLenum error) {
+    if(gl_last_error == GL_NO_ERROR)
+        gl_last_error = error;
+}
+
 void _glKosThrowError(GLenum error, char *function) {
 
     sprintf(KOS_GL_ERROR_FUNCTION, "%s\n", function);
+    set_err_flag(error);
 
     switch(error) {
         case GL_INVALID_ENUM:
@@ -70,3 +86,32 @@ void _glKosPrintError() {
 
     _glKosResetError();
 }
+
+GLenum glGetError(void) {
+    GLenum rv = gl_last_error;
+
+    gl_last_error = GL_NO_ERROR;
+    return rv;
+}
+
+const GLubyte *gluErrorString(GLenum error) {
+    switch(error) {
+        case GL_NO_ERROR:
+            return (GLubyte *)"no error";
+
+        case GL_INVALID_ENUM:
+            return (GLubyte *)"invalid enumerant";
+
+        case GL_INVALID_OPERATION:
+            return (GLubyte *)"invalid operation";
+
+        case GL_INVALID_VALUE:
+            return (GLubyte *)"invalid value";
+
+        case GL_OUT_OF_MEMORY:
+            return (GLubyte *)"out of memory";
+
+        default:
+            return (GLubyte *)"unknown error";
+    }
+}

include/gl.h

@@ -2,7 +2,7 @@
 
    libgl/gl.h
    Copyright (C) 2013-2014 Josh "PH3NOM" Pearson
-   Copyright (C) 2014 Lawrence Sebald
+   Copyright (C) 2014, 2016 Lawrence Sebald
 
    Some functionality adapted from the original KOS libgl:
    Copyright (C) 2001 Dan Potter
@@ -659,6 +659,9 @@ GLAPI void APIENTRY glFramebufferTexture2D(GLenum target, GLenum attachment,
         GLenum textarget, GLuint texture, GLint level);
 GLAPI GLenum APIENTRY glCheckFramebufferStatus(GLenum target);
 
+/* Error handling */
+GLAPI GLenum APIENTRY glGetError(void);
+
 /* Non Operational Stubs for portability */
 GLAPI void APIENTRY glAlphaFunc(GLenum func, GLclampf ref);
 GLAPI void APIENTRY glLineWidth(GLfloat width);

include/glu.h

@@ -2,6 +2,7 @@
 
    libgl/glu.h
    Copyright (C) 2013-2014 Josh "PH3NOM" Pearson
+   Copyright (C) 2016 Lawrence Sebald
 
    Some functionality adapted from the original KOS libgl:
    Copyright (C) 2001 Dan Potter
@@ -42,6 +43,8 @@ GLAPI void APIENTRY glhLookAtf2(GLfloat *eyePosition3D,
                                 GLfloat *center3D,
                                 GLfloat *upVector3D);
 
+GLAPI const GLubyte* APIENTRY gluErrorString(GLenum error);
+
 __END_DECLS
 
 #endif /* !__GL_GLU_H */