OpenGLState.h

#pragma once
 
#include "CommonGL20.h"
 
#include "Foundation/Logging/Logger.h"
 
namespace
{
  static Cogs::Logging::Log stateLogger = Cogs::Logging::getLogger("OpenGLState");
}
 
namespace Cogs
{
  struct StateVariable
  {
    StateVariable(GLenum name) :
      name(name)
    {
      originalValue = glIsEnabled(name);
    }
    ~StateVariable()
    {
      originalValue ? glEnable(name) : glDisable(name);
    }
    GLenum name;
    GLboolean originalValue;
  };
 
  struct StateBufferBinding
  {
    StateBufferBinding(GLenum name, GLenum bindingName) :
      name(name)
    {
      glGetIntegerv(bindingName, &binding);
    }
    ~StateBufferBinding()
    {
      glBindBuffer(name, binding);
    }
    GLenum name;
    GLint binding;
  };
 
  struct TextureBinding
  {
    TextureBinding(GLenum name, GLenum bindingName, GLint slot) :
      name(name),
      slot(slot)
    {
      glActiveTexture(GL_TEXTURE0 + slot);
      glGetIntegerv(bindingName, &binding);
    }
    ~TextureBinding()
    {
      glActiveTexture(GL_TEXTURE0 + slot);
      glBindTexture(name, binding);
    }
    GLenum name;
    GLint slot;
    GLint binding;
  };
 
  struct OpenGLState
  {
    GLenum frontFace;
    GLenum cullFace;
 
    std::vector<StateVariable> enabledStates;
    std::vector<StateBufferBinding> bindings;
    std::vector<TextureBinding> textures;
 
    float viewPort[4];
 
    GLint activeProgram;
    GLint activeTexture;
 
    void push()
    {
      glGetIntegerv(GL_CULL_FACE_MODE, (GLint *)&cullFace);
      glGetIntegerv(GL_FRONT_FACE, (GLint *)&frontFace);
 
      glGetFloatv(GL_VIEWPORT, viewPort);
 
      enabledStates.push_back(StateVariable(GL_BLEND));
      enabledStates.push_back(StateVariable(GL_DEPTH_TEST));
      enabledStates.push_back(StateVariable(GL_CULL_FACE));
      enabledStates.push_back(StateVariable(GL_POLYGON_OFFSET_FILL));
 
      bindings.push_back(StateBufferBinding(GL_ARRAY_BUFFER, GL_ARRAY_BUFFER_BINDING));
      bindings.push_back(StateBufferBinding(GL_ELEMENT_ARRAY_BUFFER, GL_ELEMENT_ARRAY_BUFFER_BINDING));
      bindings.push_back(StateBufferBinding(GL_UNIFORM_BUFFER, GL_UNIFORM_BUFFER_BINDING));
      bindings.push_back(StateBufferBinding(GL_PIXEL_PACK_BUFFER, GL_PIXEL_PACK_BUFFER_BINDING));
      bindings.push_back(StateBufferBinding(GL_PIXEL_UNPACK_BUFFER, GL_PIXEL_UNPACK_BUFFER_BINDING));
 
      // GLint maxTextureUnits;
      // glGetIntegerv(GL_MAX_TEXTURE_IMAGE_UNITS, &maxTextureUnits);
      // for (int i = 0; i < maxTextureUnits; ++i) {
      //   textures.push_back(TextureBinding(GL_TEXTURE_2D, GL_TEXTURE_BINDING_2D, i));
      // }
 
      glGetIntegerv(GL_CURRENT_PROGRAM, &activeProgram);
      glGetIntegerv(GL_ACTIVE_TEXTURE, &activeTexture);
    }
 
    void pop()
    {
      glFrontFace(frontFace);
      glCullFace(cullFace);
 
      glViewport(static_cast<GLint>(viewPort[0]), static_cast<GLint>(viewPort[1]), static_cast<GLsizei>(viewPort[2]), static_cast<GLsizei>(viewPort[3]));
 
      enabledStates.clear();
      bindings.clear();
      textures.clear();
 
      glBindFramebuffer(GL_FRAMEBUFFER, 0);
      glUseProgram(activeProgram);
      glActiveTexture(activeTexture);
    }
  };
}