/********************************************************************
 KWin - the KDE window manager
 This file is part of the KDE project.

Copyright (C) 2006-2007 Rivo Laks <rivolaks@hot.ee>
Copyright (C) 2010, 2011 Martin Gräßlin <mgraesslin@kde.org>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*********************************************************************/

#ifndef KWIN_GLUTILS_H
#define KWIN_GLUTILS_H

// kwin
#include <kwinglutils_export.h>
#include "kwinglutils_funcs.h"
#include "kwingltexture.h"

// Qt
#include <QSize>
#include <QStack>

/** @addtogroup kwineffects */
/** @{ */

class QVector2D;
class QVector3D;
class QVector4D;
class QMatrix4x4;

template< class K, class V > class QHash;


namespace KWin
{

class GLVertexBuffer;
class GLVertexBufferPrivate;


// Initializes GLX function pointers
void KWINGLUTILS_EXPORT initGLX();
// Initializes OpenGL stuff. This includes resolving function pointers as
//  well as checking for GL version and extensions
//  Note that GL context has to be created by the time this function is called
void KWINGLUTILS_EXPORT initGL(OpenGLPlatformInterface platformInterface);
// Initializes EGL function pointers
void KWINGLUTILS_EXPORT initEGL();
// Cleans up all resources hold by the GL Context
void KWINGLUTILS_EXPORT cleanupGL();

// Number of supported texture units
extern KWINGLUTILS_EXPORT int glTextureUnitsCount;


bool KWINGLUTILS_EXPORT hasGLVersion(int major, int minor, int release = 0);
bool KWINGLUTILS_EXPORT hasGLXVersion(int major, int minor, int release = 0);
bool KWINGLUTILS_EXPORT hasEGLVersion(int major, int minor, int release = 0);
// use for both OpenGL and GLX extensions
bool KWINGLUTILS_EXPORT hasGLExtension(const QString& extension);

// detect OpenGL error (add to various places in code to pinpoint the place)
bool KWINGLUTILS_EXPORT checkGLError(const char* txt);

inline bool KWINGLUTILS_EXPORT isPowerOfTwo(int x)
{
    return ((x & (x - 1)) == 0);
}
/**
 * @return power of two integer _greater or equal to_ x.
 *  E.g. nearestPowerOfTwo(513) = nearestPowerOfTwo(800) = 1024
 **/
int KWINGLUTILS_EXPORT nearestPowerOfTwo(int x);

/**
 * Push a new matrix on the GL matrix stack.
 * In GLES this method is a noop. This method should be preferred over glPushMatrix
 * as it also handles GLES.
 * @since 4.7
 **/
KWINGLUTILS_EXPORT void pushMatrix();
/**
 * Multiplies current matrix on GL stack with @p matrix and pushes the result on the matrix stack.
 * This method is the same as pushMatrix followed by multiplyMatrix.
 * In GLES this method is a noop. This method should be preferred over glPushMatrix
 * as it also handles GLES.
 * @param matrix The matrix the current matrix on the stack should be multiplied with.
 * @see pushMatrix
 * @see multiplyMatrix
 * @since 4.7
 **/
KWINGLUTILS_EXPORT void pushMatrix(const QMatrix4x4 &matrix);
/**
 * Multiplies the current matrix on GL stack with @p matrix.
 * In GLES this method is a noop. This method should be preferred over glMultMatrix
 * as it also handles GLES.
 * @param matrix The matrix the current matrix on the stack should be multiplied with.
 * @since 4.7
 **/
KWINGLUTILS_EXPORT void multiplyMatrix(const QMatrix4x4 &matrix);
/**
 * Replaces the current matrix on GL stack with @p matrix.
 * In GLES this method is a no-op. This method should be preferred over glLoadMatrix
 * as it also handles GLES.
 * @param matrix The new matrix to replace the existing one on the GL stack.
 * @since 4.7
 **/
KWINGLUTILS_EXPORT void loadMatrix(const QMatrix4x4 &matrix);
/**
 * Pops the current matrix from the GL matrix stack.
 * In GLES this method is a noop. This method should be preferred over glPopMatrix
 * as it also handles GLES.
 * @since 4.7
 **/
KWINGLUTILS_EXPORT void popMatrix();

class KWINGLUTILS_EXPORT GLShader
{
public:
    enum Flags {
        NoFlags         = 0,
        ExplicitLinking = (1 << 0)
    };

    GLShader(const QString &vertexfile, const QString &fragmentfile, unsigned int flags = NoFlags);
    ~GLShader();

    bool isValid() const  {
        return mValid;
    }

    void bindAttributeLocation(const char *name, int index);
    void bindFragDataLocation(const char *name, int index);

    bool link();

    int uniformLocation(const char* name);

    bool setUniform(const char* name, float value);
    bool setUniform(const char* name, int value);
    bool setUniform(const char* name, const QVector2D& value);
    bool setUniform(const char* name, const QVector3D& value);
    bool setUniform(const char* name, const QVector4D& value);
    bool setUniform(const char* name, const QMatrix4x4& value);
    bool setUniform(const char* name, const QColor& color);

    bool setUniform(int location, float value);
    bool setUniform(int location, int value);
    bool setUniform(int location, const QVector2D &value);
    bool setUniform(int location, const QVector3D &value);
    bool setUniform(int location, const QVector4D &value);
    bool setUniform(int location, const QMatrix4x4 &value);
    bool setUniform(int location, const QColor &value);

    int attributeLocation(const char* name);
    bool setAttribute(const char* name, float value);
    /**
     * @return The value of the uniform as a matrix
     * @since 4.7
     **/
    QMatrix4x4 getUniformMatrix4x4(const char* name);

    enum MatrixUniform {
        TextureMatrix = 0,
        ProjectionMatrix,
        ModelViewMatrix,
        WindowTransformation,
        ScreenTransformation,
        MatrixCount
    };

    enum Vec2Uniform {
        Offset,
        Vec2UniformCount
    };

    enum Vec4Uniform {
        ModulationConstant,
        Vec4UniformCount
    };

    enum FloatUniform {
        Saturation,
        FloatUniformCount
    };

    enum IntUniform {
        AlphaToOne,     ///< @deprecated no longer used
        ColorCorrectionLookupTextureUnit,
        IntUniformCount
    };

    enum ColorUniform {
        Color,
        ColorUniformCount
    };

    bool setUniform(MatrixUniform uniform, const QMatrix4x4 &matrix);
    bool setUniform(Vec2Uniform uniform,   const QVector2D &value);
    bool setUniform(Vec4Uniform uniform,   const QVector4D &value);
    bool setUniform(FloatUniform uniform,  float value);
    bool setUniform(IntUniform uniform,    int value);
    bool setUniform(ColorUniform uniform,  const QVector4D &value);
    bool setUniform(ColorUniform uniform,  const QColor &value);

protected:
    GLShader(unsigned int flags = NoFlags);
    bool loadFromFiles(const QString& vertexfile, const QString& fragmentfile);
    bool load(const QByteArray &vertexSource, const QByteArray &fragmentSource);
    const QByteArray prepareSource(GLenum shaderType, const QByteArray &sourceCode) const;
    bool compile(GLuint program, GLenum shaderType, const QByteArray &sourceCode) const;
    void bind();
    void unbind();
    void resolveLocations();

private:
    unsigned int mProgram;
    bool mValid:1;
    bool mLocationsResolved:1;
    bool mExplicitLinking:1;
    int mMatrixLocation[MatrixCount];
    int mVec2Location[Vec2UniformCount];
    int mVec4Location[Vec4UniformCount];
    int mFloatLocation[FloatUniformCount];
    int mIntLocation[IntUniformCount];
    int mColorLocation[ColorUniformCount];

    static bool sColorCorrect;

    friend class ColorCorrection;
    friend class ColorCorrectionPrivate;
    friend class ShaderManager;
};

/**
 * @short Manager for Shaders.
 *
 * This class provides some built-in shaders to be used by both compositing scene and effects.
 * The ShaderManager provides methods to bind a built-in or a custom shader and keeps track of
 * the shaders which have been bound. When a shader is unbound the previously bound shader
 * will be rebound.
 *
 * @author Martin Gräßlin <mgraesslin@kde.org>
 * @since 4.7
 **/
class KWINGLUTILS_EXPORT ShaderManager
{
public:
    /**
     * Identifiers for built-in shaders available for effects and scene
     **/
    enum ShaderType {
        /**
         * An orthographic projection shader able to render textured geometries.
         * Expects a @c vec2 uniform @c offset describing the offset from top-left corner
         * and defaults to @c (0/0). Expects a @c vec2 uniform @c textureSize to calculate
         * normalized texture coordinates. Defaults to @c (1.0/1.0). And expects a @c vec3
         * uniform @c colorManiuplation, with @c x being opacity, @c y being brightness and
         * @c z being saturation. All three values default to @c 1.0.
         * The sampler uniform is @c sample and defaults to @c 0.
         * The shader uses two vertex attributes @c vertex and @c texCoord.
         **/
        SimpleShader = 0,
        /**
         * A generic shader able to render transformed, textured geometries.
         * This shader is mostly needed by the scene and not of much interest for effects.
         * Effects can influence this shader through @link ScreenPaintData and @link WindowPaintData.
         * The shader expects four @c mat4 uniforms @c projection, @c modelview,
         * @c screenTransformation and @c windowTransformation. The fragment shader expect the
         * same uniforms as the SimpleShader and the same vertex attributes are used.
         **/
        GenericShader,
        /**
         * An orthographic shader to render simple colored geometries without texturing.
         * Expects a @c vec2 uniform @c offset describing the offset from top-left corner
         * and defaults to @c (0/0). The fragment shader expects a single @c vec4 uniform
         * @c geometryColor, which defaults to fully opaque black.
         * The Shader uses one vertex attribute @c vertex.
         **/
        ColorShader
    };

    /**
     * @return The currently bound shader or @c null if no shader is bound.
     **/
    GLShader *getBoundShader() const;

    /**
     * @return @c true if a shader is bound, @c false otherwise
     **/
    bool isShaderBound() const;
    /**
     * Allows to query whether Shaders are supported by the compositor, that is
     * whether the Shaders compiled successfully.
     *
     * With OpenGL 1 compositing this method will always return @c false.
     *
     * Do not use this method to check whether the compositor uses OpenGL 1 or 2,
     * use @link EffectsHandler::compositingType instead.
     * @return @c true if the built-in shaders are valid, @c false otherwise
     **/
    bool isValid() const;
    /**
     * Is @c true if the environment variable KWIN_GL_DEBUG is set to 1.
     * In that case shaders are compiled with KWIN_SHADER_DEBUG defined.
     * @returns @c true if shaders are compiled with debug information
     * @since 4.8
     **/
    bool isShaderDebug() const;

    /**
     * Binds the shader of specified @p type.
     * To unbind the shader use @link popShader. A previous bound shader will be rebound.
     * @param type The built-in shader to bind
     * @param reset Whether all uniforms should be reset to their default values
     * @return The bound shader or @c NULL if shaders are not valid
     * @see popShader
     **/
    GLShader *pushShader(ShaderType type, bool reset = false);
    /**
     * Binds the @p shader.
     * To unbind the shader use @link popShader. A previous bound shader will be rebound.
     * To bind a built-in shader use the more specific method.
     * @param shader The shader to be bound
     * @see popShader
     **/
    void pushShader(GLShader *shader);

    /**
     * Unbinds the currently bound shader and rebinds a previous stored shader.
     * If there is no previous shader, no shader will be rebound.
     * It is not safe to call this method if there is no bound shader.
     * @see pushShader
     * @see getBoundShader
     **/
    void popShader();

    /**
     * Resets all shaders to the default uniform values.
     * Only built in shaders are changed.
     * @since 4.8
     **/
    void resetAllShaders();

    /**
     * Resets ShaderType @p type uniforms of a custom shader
     * @since 4.11.1
     */
    void resetShader(GLShader *shader, ShaderType type);

    /**
     * Creates a GLShader with a built-in vertex shader and a custom fragment shader.
     * @param vertex The generic vertex shader
     * @param fragmentFile The path to the source code of the fragment shader
     * @return The created shader
     **/
    GLShader *loadFragmentShader(ShaderType vertex, const QString &fragmentFile);
    /**
     * Creates a GLShader with a built-in fragment shader and a custom vertex shader.
     * @param fragment The generic fragment shader
     * @param vertexFile The path to the source code of the vertex shader
     * @return The created shader
     **/
    GLShader *loadVertexShader(ShaderType fragment, const QString &vertexFile);
    /**
     * Creates a GLShader with the specified sources.
     * The difference to GLShader is that it does not need to be loaded from files.
     * @param vertexSource The source code of the vertex shader
     * @param fragmentSource The source code of the fragment shader.
     * @return The created shader
     **/
    GLShader *loadShaderFromCode(const QByteArray &vertexSource, const QByteArray &fragmentSource);

    /**
     * @return a pointer to the ShaderManager instance
     **/
    static ShaderManager *instance();
    /**
     * @brief Ensures that the ShaderManager is disabled.
     *
     * Used only by an OpenGL 1 Scene which does not use OpenGL 2 Shaders.
     *
     * @internal
     * @since 4.10
     **/
    static void disable();

    /**
     * @internal
     **/
    static void cleanup();

private:
    ShaderManager();
    ~ShaderManager();

    void initShaders();
    void resetShader(ShaderType type);
    void bindFragDataLocations(GLShader *shader);
    void bindAttributeLocations(GLShader *shader) const;

    QStack<GLShader*> m_boundShaders;
    GLShader *m_shader[3];
    bool m_inited;
    bool m_valid;
    bool m_debug;
    QByteArray m_shaderDir;
    static ShaderManager *s_shaderManager;
};

/**
 * An helper class to push a Shader on to ShaderManager's stack and ensuring that the Shader
 * gets popped again from the stack automatically once the object goes out of life.
 *
 * How to use:
 * @code
 * {
 * GLShader *myCustomShaderIWantToPush;
 * ShaderBinder binder(myCustomShaderIWantToPush);
 * // do stuff with the shader being pushed on the stack
 * }
 * // here the Shader is automatically popped as helper does no longer exist.
 * @endcode
 *
 * This class takes care for the case that the Compositor uses OpenGL 1 and the ShaderManager is
 * not valid. In that case the helper does not do anything. So this helper can be used to simplify
 * the code to remove checks for OpenGL 1/2.
 * @since 4.10
 **/
class KWINGLUTILS_EXPORT ShaderBinder
{
public:
    /**
     * @brief Pushes the Shader of the given @p type to the ShaderManager's stack.
     *
     * @param type The built-in Shader type
     * @param reset Whether all uniforms should be reset to their default values. Defaults to false.
     * @see ShaderManager::pushShader
     **/
    explicit ShaderBinder(ShaderManager::ShaderType type, bool reset = false);
    /**
     * @brief Pushes the given @p shader to the ShaderManager's stack.
     *
     * @param shader The Shader to push on the stack
     * @see ShaderManager::pushShader
     **/
    explicit ShaderBinder(GLShader *shader);
    ~ShaderBinder();

    /**
     * @return The Shader pushed to the Stack. On OpenGL 1 this returns a @c null pointer.
     **/
    GLShader *shader();

private:
    GLShader *m_shader;
};

inline
ShaderBinder::ShaderBinder(ShaderManager::ShaderType type, bool reset)
    : m_shader(nullptr)
{
#ifdef KWIN_HAVE_OPENGL_1
    if (!ShaderManager::instance()->isValid()) {
        return;
    }
#endif
    m_shader = ShaderManager::instance()->pushShader(type, reset);
}

inline
ShaderBinder::ShaderBinder(GLShader *shader)
    : m_shader(shader)
{
#ifdef KWIN_HAVE_OPENGL_1
    if (!ShaderManager::instance()->isValid()) {
        return;
    }
#endif
    ShaderManager::instance()->pushShader(shader);
}

inline
ShaderBinder::~ShaderBinder()
{
#ifdef KWIN_HAVE_OPENGL_1
    if (!ShaderManager::instance()->isValid()) {
        return;
    }
#endif
    ShaderManager::instance()->popShader();
}

inline
GLShader* ShaderBinder::shader()
{
    return m_shader;
}

/**
 * @short Render target object
 *
 * Render target object enables you to render onto a texture. This texture can
 *  later be used to e.g. do post-processing of the scene.
 *
 * @author Rivo Laks <rivolaks@hot.ee>
 **/
class KWINGLUTILS_EXPORT GLRenderTarget
{
public:
    /**
     * Constructs a GLRenderTarget
     * @param color texture where the scene will be rendered onto
     **/
    explicit GLRenderTarget(const GLTexture& color);
    ~GLRenderTarget();

    /**
     * Enables this render target.
     * All OpenGL commands from now on affect this render target until the
     *  @ref disable method is called
     **/
    bool enable();
    /**
     * Disables this render target, activating whichever target was active
     *  when @ref enable was called.
     **/
    bool disable();

    /**
     * Sets the target texture
     * @param target texture where the scene will be rendered on
     * @since 4.8
     **/
    void attachTexture(const GLTexture& target);

    bool valid() const  {
        return mValid;
    }

    static void initStatic();
    static bool supported()  {
        return sSupported;
    }
    static void pushRenderTarget(GLRenderTarget *target);
    static GLRenderTarget *popRenderTarget();
    static bool isRenderTargetBound();
    /**
     * Whether the GL_EXT_framebuffer_blit extension is supported.
     * This functionality is not available in OpenGL ES 2.0.
     *
     * @returns whether framebuffer blitting is supported.
     * @since 4.8
     **/
    static bool blitSupported();

    /**
     * Blits the content of the current draw framebuffer into the texture attached to this FBO.
     *
     * Be aware that framebuffer blitting may not be supported on all hardware. Use @link blitSupported to check whether
     * it is supported.
     * @param source Geometry in screen coordinates which should be blitted, if not specified complete framebuffer is used
     * @param destination Geometry in attached texture, if not specified complete texture is used as destination
     * @param filter The filter to use if blitted content needs to be scaled.
     * @see blitSupported
     * @since 4.8
     **/
    void blitFromFramebuffer(const QRect &source = QRect(), const QRect &destination = QRect(), GLenum filter = GL_LINEAR);


protected:
    void initFBO();


private:
    static bool sSupported;
    static bool s_blitSupported;
    static QStack<GLRenderTarget*> s_renderTargets;

    GLTexture mTexture;
    bool mValid;

    GLuint mFramebuffer;
};

enum VertexAttributeType {
    VA_Position = 0,
    VA_TexCoord = 1,
    VertexAttributeCount = 2
};

/**
 * Describes the format of a vertex attribute stored in a buffer object.
 *
 * The attribute format consists of the attribute index, the number of
 * vector components, the data type, and the offset of the first element
 * relative to the start of the vertex data.
 */
struct GLVertexAttrib
{
    int index;            /** The attribute index */
    int size;             /** The number of components [1..4] */
    GLenum type;          /** The type (e.g. GL_FLOAT) */
    int relativeOffset;   /** The relative offset of the attribute */
};

/**
 * @short Vertex Buffer Object
 *
 * This is a short helper class to use vertex buffer objects (VBO). A VBO can be used to buffer
 * vertex data and to store them on graphics memory. It is the only allowed way to pass vertex
 * data to the GPU in OpenGL ES 2 and OpenGL 3 with forward compatible mode.
 *
 * If VBOs are not supported on the used OpenGL profile this class falls back to legacy
 * rendering using client arrays. Therefore this class should always be used for rendering geometries.
 *
 * @author Martin Gräßlin <mgraesslin@kde.org>
 * @since 4.6
 */
class KWINGLUTILS_EXPORT GLVertexBuffer
{
public:
    /**
     * Enum to define how often the vertex data in the buffer object changes.
     */
    enum UsageHint {
        Dynamic, ///< frequent changes, but used several times for rendering
        Static, ///< No changes to data
        Stream ///< Data only used once for rendering, updated very frequently
    };

    explicit GLVertexBuffer(UsageHint hint);
    ~GLVertexBuffer();

    /**
     * Specifies how interleaved vertex attributes are laid out in
     * the buffer object.
     *
     * Note that the attributes and the stride should be 32 bit aligned
     * or a performance penalty may be incurred.
     *
     * For some hardware the optimal stride is a multiple of 32 bytes.
     *
     * Example:
     *
     *     struct Vertex {
     *         QVector3D position;
     *         QVector2D texcoord;
     *     };
     *
     *     const GLVertexAttrib attribs[] = {
     *         { VA_Position, 3, GL_FLOAT, offsetof(Vertex, position) },
     *         { VA_TexCoord, 2, GL_FLOAT, offsetof(Vertex, texcoord) }
     *     };
     *
     *     Vertex vertices[6];
     *     vbo->setAttribLayout(attribs, 2, sizeof(Vertex));
     *     vbo->setData(vertices, sizeof(vertices));
     */
    void setAttribLayout(const GLVertexAttrib *attribs, int count, int stride);

    /**
     * Uploads data into the buffer object's data store.
     */
    void setData(const void *data, size_t sizeInBytes);

    /**
     * Sets the number of vertices that will be drawn by the render() method.
     */
    void setVertexCount(int count);

    /**
     * Sets the vertex data.
     * @param numberVertices The number of vertices in the arrays
     * @param dim The dimension of the vertices: 2 for x/y, 3 for x/y/z
     * @param vertices The vertices, size must equal @a numberVertices * @a dim
     * @param texcoords The texture coordinates for each vertex.
     * Size must equal 2 * @a numberVertices.
     */
    void setData(int numberVertices, int dim, const float* vertices, const float* texcoords);

    /**
     * Maps an unused range of the data store into the client's address space.
     *
     * The data store will be reallocated if it is smaller than the given size.
     *
     * The buffer object is mapped for writing, not reading. Attempts to read from
     * the mapped buffer range may result in system errors, including program
     * termination. The data in the mapped region is undefined until it has been
     * written to. If subsequent GL calls access unwritten memory, the results are
     * undefined and system errors, including program termination, may occur.
     *
     * No GL calls that access the buffer object must be made while the buffer
     * object is mapped. The returned pointer must not be passed as a parameter
     * value to any GL function.
     *
     * It is assumed that the GL_ARRAY_BUFFER_BINDING will not be changed while
     * the buffer object is mapped.
     */
    GLvoid *map(size_t size);

    /**
     * Flushes the mapped buffer range and unmaps the buffer.
     */
    void unmap();

    /**
     * Binds the vertex arrays to the context.
     */
    void bindArrays();

    /**
     * Disables the vertex arrays.
     */
    void unbindArrays();

    /**
     * Draws count vertices beginning with first.
     */
    void draw(GLenum primitiveMode, int first, int count);

    /**
     * Draws count vertices beginning with first.
     */
    void draw(const QRegion &region, GLenum primitiveMode, int first, int count, bool hardwareClipping = false);

    /**
     * Renders the vertex data in given @a primitiveMode.
     * Please refer to OpenGL documentation of glDrawArrays or glDrawElements for allowed
     * values for @a primitiveMode. Best is to use GL_TRIANGLES or similar to be future
     * compatible.
     */
    void render(GLenum primitiveMode);
    /**
     * Same as above restricting painting to @a region if @a hardwareClipping is true.
     * It's within the caller's responsibility to enable GL_SCISSOR_TEST.
     */
    void render(const QRegion& region, GLenum primitiveMode, bool hardwareClipping = false);
    /**
     * Sets the color the geometry will be rendered with.
     * For legacy rendering glColor is used before rendering the geometry.
     * For core shader a uniform "geometryColor" is expected and is set.
     * @param color The color to render the geometry
     * @param enableColor Whether the geometry should be rendered with a color or not
     * @see setUseColor
     * @see isUseColor
     * @since 4.7
     **/
    void setColor(const QColor& color, bool enableColor = true);
    /**
     * @return @c true if geometry will be painted with a color, @c false otherwise
     * @see setUseColor
     * @see setColor
     * @since 4.7
     **/
    bool isUseColor() const;
    /**
     * Enables/Disables rendering the geometry with a color.
     * If no color is set an opaque, black color is used.
     * @param enable Enable/Disable rendering with color
     * @see isUseColor
     * @see setColor
     * @since 4.7
     **/
    void setUseColor(bool enable);

    /**
     * Resets the instance to default values.
     * Useful for shared buffers.
     * @since 4.7
     **/
    void reset();

    /**
     * @internal
     */
    static void initStatic();

    /**
     * @internal
     */
    static void cleanup();

    /**
     * Returns true if VBOs are supported, it is save to use this class even if VBOs are not
     * supported.
     * @returns true if vertex buffer objects are supported
     */
    static bool isSupported();

    /**
     * Returns true if indexed quad mode is supported, and false otherwise.
     */
    static bool supportsIndexedQuads();

    /**
     * @return A shared VBO for streaming data
     * @since 4.7
     **/
    static GLVertexBuffer *streamingBuffer();

private:
    GLVertexBufferPrivate* const d;
};

} // namespace

/** @} */

#endif