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# glbuffers.h Example File
demos/boxes/glbuffers.h

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     ** ensure the GNU Lesser General Public License version 2.1 requirements
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     ** GNU General Public License Usage
     ** Alternatively, this file may be used under the terms of the GNU
     ** General Public License version 3.0 as published by the Free Software
     ** Foundation and appearing in the file LICENSE.GPL included in the
     ** packaging of this file.  Please review the following information to
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     #ifndef GLBUFFERS_H
     #define GLBUFFERS_H

     //#include <GL/glew.h>
     #include "glextensions.h"

     #include <QtGui>
     #include <QtOpenGL>

     #define BUFFER_OFFSET(i) ((char*)0 + (i))
     #define SIZE_OF_MEMBER(cls, member) sizeof(static_cast<cls *>(0)->member)

     #define GLBUFFERS_ASSERT_OPENGL(prefix, assertion, returnStatement)                         \
     if (m_failed || !(assertion)) {                                                             \
         if (!m_failed) qCritical(prefix ": The necessary OpenGL functions are not available."); \
         m_failed = true;                                                                        \
         returnStatement;                                                                        \
     }

     class QMatrix4x4;

     class GLTexture
     {
     public:
         GLTexture();
         virtual ~GLTexture();
         virtual void bind() = 0;
         virtual void unbind() = 0;
         virtual bool failed() const {return m_failed;}
     protected:
         GLuint m_texture;
         bool m_failed;
     };

     class GLFrameBufferObject
     {
     public:
         friend class GLRenderTargetCube;
         // friend class GLRenderTarget2D;

         GLFrameBufferObject(int width, int height);
         virtual ~GLFrameBufferObject();
         bool isComplete();
         virtual bool failed() const {return m_failed;}
     protected:
         void setAsRenderTarget(bool state = true);
         GLuint m_fbo;
         GLuint m_depthBuffer;
         int m_width, m_height;
         bool m_failed;
     };

     class GLTexture2D : public GLTexture
     {
     public:
         GLTexture2D(int width, int height);
         GLTexture2D(const QString& fileName, int width = 0, int height = 0);
         void load(int width, int height, QRgb *data);
         virtual void bind();
         virtual void unbind();
     };

     class GLTexture3D : public GLTexture
     {
     public:
         GLTexture3D(int width, int height, int depth);
         // TODO: Implement function below
         //GLTexture3D(const QString& fileName, int width = 0, int height = 0);
         void load(int width, int height, int depth, QRgb *data);
         virtual void bind();
         virtual void unbind();
     };

     class GLTextureCube : public GLTexture
     {
     public:
         GLTextureCube(int size);
         GLTextureCube(const QStringList& fileNames, int size = 0);
         void load(int size, int face, QRgb *data);
         virtual void bind();
         virtual void unbind();
     };

     // TODO: Define and implement class below
     //class GLRenderTarget2D : public GLTexture2D

     class GLRenderTargetCube : public GLTextureCube
     {
     public:
         GLRenderTargetCube(int size);
         // begin rendering to one of the cube's faces. 0 <= face < 6
         void begin(int face);
         // end rendering
         void end();
         virtual bool failed() {return m_failed || m_fbo.failed();}

         static void getViewMatrix(QMatrix4x4& mat, int face);
         static void getProjectionMatrix(QMatrix4x4& mat, float nearZ, float farZ);
     private:
         GLFrameBufferObject m_fbo;
     };

     struct VertexDescription
     {
         enum
         {
             Null = 0, // Terminates a VertexDescription array
             Position,
             TexCoord,
             Normal,
             Color,
         };
         int field; // Position, TexCoord, Normal, Color
         int type; // GL_FLOAT, GL_UNSIGNED_BYTE
         int count; // number of elements
         int offset; // field's offset into vertex struct
         int index; // 0 (unused at the moment)
     };

     // Implementation of interleaved buffers.
     // 'T' is a struct which must include a null-terminated static array
     // 'VertexDescription* description'.
     // Example:
     /*
     struct Vertex
     {
         GLfloat position[3];
         GLfloat texCoord[2];
         GLfloat normal[3];
         GLbyte color[4];
         static VertexDescription description[];
     };

     VertexDescription Vertex::description[] = {
         {VertexDescription::Position, GL_FLOAT, SIZE_OF_MEMBER(Vertex, position) / sizeof(GLfloat), offsetof(Vertex, position), 0},
         {VertexDescription::TexCoord, GL_FLOAT, SIZE_OF_MEMBER(Vertex, texCoord) / sizeof(GLfloat), offsetof(Vertex, texCoord), 0},
         {VertexDescription::Normal, GL_FLOAT, SIZE_OF_MEMBER(Vertex, normal) / sizeof(GLfloat), offsetof(Vertex, normal), 0},
         {VertexDescription::Color, GL_BYTE, SIZE_OF_MEMBER(Vertex, color) / sizeof(GLbyte), offsetof(Vertex, color), 0},
         {VertexDescription::Null, 0, 0, 0, 0},
     };
     */
     template<class T>
     class GLVertexBuffer
     {
     public:
         GLVertexBuffer(int length, const T *data = 0, int mode = GL_STATIC_DRAW)
             : m_length(0)
             , m_mode(mode)
             , m_buffer(0)
             , m_failed(false)
         {
             GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::GLVertexBuffer", glGenBuffers && glBindBuffer && glBufferData, return)

                     glGenBuffers(1, &m_buffer);
                     glBindBuffer(GL_ARRAY_BUFFER, m_buffer);
                     glBufferData(GL_ARRAY_BUFFER, (m_length = length) * sizeof(T), data, mode);
         }

         ~GLVertexBuffer()
         {
             GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::~GLVertexBuffer", glDeleteBuffers, return)

             glDeleteBuffers(1, &m_buffer);
         }

         void bind()
         {
             GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::bind", glBindBuffer, return)

             glBindBuffer(GL_ARRAY_BUFFER, m_buffer);
             for (VertexDescription *desc = T::description; desc->field != VertexDescription::Null; ++desc) {
                 switch (desc->field) {
                 case VertexDescription::Position:
                     glVertexPointer(desc->count, desc->type, sizeof(T), BUFFER_OFFSET(desc->offset));
                     glEnableClientState(GL_VERTEX_ARRAY);
                     break;
                 case VertexDescription::TexCoord:
                     glTexCoordPointer(desc->count, desc->type, sizeof(T), BUFFER_OFFSET(desc->offset));
                     glEnableClientState(GL_TEXTURE_COORD_ARRAY);
                     break;
                 case VertexDescription::Normal:
                     glNormalPointer(desc->type, sizeof(T), BUFFER_OFFSET(desc->offset));
                     glEnableClientState(GL_NORMAL_ARRAY);
                     break;
                 case VertexDescription::Color:
                     glColorPointer(desc->count, desc->type, sizeof(T), BUFFER_OFFSET(desc->offset));
                     glEnableClientState(GL_COLOR_ARRAY);
                     break;
                 default:
                     break;
                 }
             }
         }

         void unbind()
         {
             GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::unbind", glBindBuffer, return)

             glBindBuffer(GL_ARRAY_BUFFER, 0);
             for (VertexDescription *desc = T::description; desc->field != VertexDescription::Null; ++desc) {
                 switch (desc->field) {
                 case VertexDescription::Position:
                     glDisableClientState(GL_VERTEX_ARRAY);
                     break;
                 case VertexDescription::TexCoord:
                     glDisableClientState(GL_TEXTURE_COORD_ARRAY);
                     break;
                 case VertexDescription::Normal:
                     glDisableClientState(GL_NORMAL_ARRAY);
                     break;
                 case VertexDescription::Color:
                     glDisableClientState(GL_COLOR_ARRAY);
                     break;
                 default:
                     break;
                 }
             }
         }

         int length() const {return m_length;}

         T *lock()
         {
             GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::lock", glBindBuffer && glMapBuffer, return 0)

             glBindBuffer(GL_ARRAY_BUFFER, m_buffer);
             //glBufferData(GL_ARRAY_BUFFER, m_length, NULL, m_mode);
             GLvoid* buffer = glMapBuffer(GL_ARRAY_BUFFER, GL_READ_WRITE);
             m_failed = (buffer == 0);
             return reinterpret_cast<T *>(buffer);
         }

         void unlock()
         {
             GLBUFFERS_ASSERT_OPENGL("GLVertexBuffer::unlock", glBindBuffer && glUnmapBuffer, return)

             glBindBuffer(GL_ARRAY_BUFFER, m_buffer);
             glUnmapBuffer(GL_ARRAY_BUFFER);
         }

         bool failed()
         {
             return m_failed;
         }

     private:
         int m_length, m_mode;
         GLuint m_buffer;
         bool m_failed;
     };

     template<class T>
     class GLIndexBuffer
     {
     public:
         GLIndexBuffer(int length, const T *data = 0, int mode = GL_STATIC_DRAW)
             : m_length(0)
             , m_mode(mode)
             , m_buffer(0)
             , m_failed(false)
         {
             GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::GLIndexBuffer", glGenBuffers && glBindBuffer && glBufferData, return)

             glGenBuffers(1, &m_buffer);
             glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_buffer);
             glBufferData(GL_ELEMENT_ARRAY_BUFFER, (m_length = length) * sizeof(T), data, mode);
         }

         ~GLIndexBuffer()
         {
             GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::~GLIndexBuffer", glDeleteBuffers, return)

             glDeleteBuffers(1, &m_buffer);
         }

         void bind()
         {
             GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::bind", glBindBuffer, return)

             glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_buffer);
         }

         void unbind()
         {
             GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::unbind", glBindBuffer, return)

             glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
         }

         int length() const {return m_length;}

         T *lock()
         {
             GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::lock", glBindBuffer && glMapBuffer, return 0)

             glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_buffer);
             GLvoid* buffer = glMapBuffer(GL_ELEMENT_ARRAY_BUFFER, GL_READ_WRITE);
             m_failed = (buffer == 0);
             return reinterpret_cast<T *>(buffer);
         }

         void unlock()
         {
             GLBUFFERS_ASSERT_OPENGL("GLIndexBuffer::unlock", glBindBuffer && glUnmapBuffer, return)

             glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_buffer);
             glUnmapBuffer(GL_ELEMENT_ARRAY_BUFFER);
         }

         bool failed()
         {
             return m_failed;
         }

     private:
         int m_length, m_mode;
         GLuint m_buffer;
         bool m_failed;
     };

     #endif