Re: Derelict-GL3 Error

[Kevin via Digitalmars-d]

On Tuesday, 10 January 2017 at 04:34:24 UTC, Mike Parker wrote:
On Tuesday, 10 January 2017 at 01:43:50 UTC, Kevin wrote:
Using Archlinux, Derelict-gl3 1.0.18
check format (GLuint, Glenum, Glint*)
// this does not work
glGetShaderiv(program, GL_LINK_STATUS, &success);
writeln("GL_ERROR: ", glGetError());

Give me error 1282

// this one works fine.
glGetShaderiv(shader, GL_COMPILE_STATUS, &success);

This has nothing to do with Derelict. It's an error in your use 
of OpenGL, so you need to look up the OpenGL error code 1282 
and figure out what it means.

Since I'm here, I'll save you some time. 1282 is 
GL_INVALID_OPERATION. However, just because you called it 
immediately after glGetShaderiv *does not mean* that function 
caused the error. The error code may have been set any time 
before that, by any of the functions you called. Then, when you 
call glGetError, the error code is reset to 0, so your next 
call to glGetError shows no error.

Here's some psuedocode to illustrate:

// OpenGL's internal error code
errCode = 0;

// In your code:
glSomething(); // no error
glSomethingElse(); // no error
glAnotherThing();  // Oops! An error - errCode now is set to 
1282
glThisThing();  // No error, but the state is now messed up
glThatThing();  // No error
err = glGetError();  // This returns 1282, as set by 
glAnotherThing above


What you need to do is debug your OpenGL code. The simplest way 
to do that is to insert glGetError at different points, 
recompile, and run it again. This will help you narrow things 
down to the function that actually caused the error.

And for future reference, please go to opengl.org or the OpenGL 
forums at gamedev.net for help with OpenGL.

Thanks for info. I already did glGetError() above and below.
and it only from that code. At first I thought i put the wrong 
type. I set success to 1 and let code go through and shader work 
fine. The glGetShaderiv(program, GL_LINK_STATUS, &success) check 
does not work. If you still think it opengl problem I will take 
it there or maybe i made a simple mistake I can't see.

full code
import std.string : toStringz;
import std.stdio;
import std.file;

import derelict.opengl3.gl;

struct Shader {
  private GLuint program;

  @disable this(this);

  ~this() {
    glDeleteProgram(program);
  }

  void use() {
    glUseProgram(program);
  }

  bool create(string vertexName, string fragmentName, string 
geometryName=null) {
    char[512] infoLog;
    program = 0;
    GLuint vertexShader = shaderFile(vertexName, 
GL_VERTEX_SHADER);
    GLuint fragmentShader = shaderFile(fragmentName, 
GL_FRAGMENT_SHADER);
    GLuint geometryShader = 0;
    GLint success = 1;

    if(geometryName !is null)
      geometryShader = shaderFile(geometryName, 
GL_GEOMETRY_SHADER);

    if(vertexShader == 0) {
      writeln("Vertex is null");
      return false;
    }

    if(fragmentShader == 0) {
      writeln("Fragment is null");
      glDeleteShader(vertexShader);
      return false;
    }

    if(geometryName !is null) {
      if(geometryShader == 0) {
        writeln("Geometry is null");
        glDeleteShader(vertexShader);
        glDeleteShader(fragmentShader);
        return false;
      }
    }

    // create program
    program = glCreateProgram();
    glAttachShader(program, vertexShader);
    glAttachShader(program, fragmentShader);
    if(geometryName !is null)
      glAttachShader(program, geometryShader);

    glLinkProgram(program);
    writeln("Before GL_ERROR: ", glGetError());

    // this does not work
    glGetShaderiv(program, GL_LINK_STATUS, &success);
    writeln("After GL_ERROR: ", glGetError());
    if(!success) {
      writeln("GL_ERROR: ", glGetError());
      glGetShaderInfoLog(program, 512, null, infoLog.ptr);
      writeln("ERROR::Shader program linking failed");
      writeln(infoLog);
    }

    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);
    if(geometryName !is null)
      glDeleteShader(geometryShader);

    return cast(bool) success;
  }

  private GLuint shaderFile(string sourceName, GLenum flag) {
    string fileData;
    GLchar* source;
    GLint success;
    GLchar[512] infoLog;
    GLuint shader = 0;

    if(exists(sourceName) != 0)
      fileData = cast(string) read(sourceName);
    else {
      writeln("ERROR: File doesn't exist");
      return 0;
    }

    source = cast(GLchar*) (toStringz(fileData));
    shader = glCreateShader(flag);
                glShaderSource(shader, 1, &source, null);
                glCompileShader(shader);

    // this one work fine
    glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
    writeln("sh .. GL_ERROR: ", glGetError());
                if(!success)
                {
                        glGetShaderInfoLog(shader, 512, null, infoLog.ptr);
      if(flag == GL_VERTEX_SHADER)
        writeln("ERROR::Shader vertex compiltion failed ");
      else if(flag == GL_FRAGMENT_SHADER)
        writeln("ERROR::Shader fragment compiltion failed");
      else if(flag == GL_GEOMETRY_SHADER)
        writeln("ERROR::Shader geometry compiltion failed");

      writeln(infoLog);
                }

    return shader;
  }
}