source: trunk/src/opengl/qglshaderprogram.cpp@ 729

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#include "qglshaderprogram.h"
#include "qglextensions_p.h"
#include "qgl_p.h"
#include <QtCore/private/qobject_p.h>
#include <QtCore/qdebug.h>
#include <QtCore/qfile.h>
#include <QtCore/qvarlengtharray.h>
#include <QtCore/qvector.h>

QT_BEGIN_NAMESPACE

#if !defined(QT_OPENGL_ES_1_CL) && !defined(QT_OPENGL_ES_1)

/*!
    \class QGLShaderProgram
    \brief The QGLShaderProgram class allows OpenGL shader programs to be linked and used.
    \since 4.6
    \ingroup painting-3D

    \section1 Introduction

    This class supports shader programs written in the OpenGL Shading
    Language (GLSL) and in the OpenGL/ES Shading Language (GLSL/ES).

    QGLShader and QGLShaderProgram shelter the programmer from the details of
    compiling and linking vertex and fragment shaders.

    The following example creates a vertex shader program using the
    supplied source \c{code}.  Once compiled and linked, the shader
    program is activated in the current QGLContext by calling
    QGLShaderProgram::bind():

    \snippet doc/src/snippets/code/src_opengl_qglshaderprogram.cpp 0

    \section1 Writing portable shaders

    Shader programs can be difficult to reuse across OpenGL implementations
    because of varying levels of support for standard vertex attributes and
    uniform variables.  In particular, GLSL/ES lacks all of the
    standard variables that are present on desktop OpenGL systems:
    \c{gl_Vertex}, \c{gl_Normal}, \c{gl_Color}, and so on.  Desktop OpenGL
    lacks the variable qualifiers \c{highp}, \c{mediump}, and \c{lowp}.

    The QGLShaderProgram class makes the process of writing portable shaders
    easier by prefixing all shader programs with the following lines on
    desktop OpenGL:

    \code
    #define highp
    #define mediump
    #define lowp
    \endcode

    This makes it possible to run most GLSL/ES shader programs
    on desktop systems.  The programmer should restrict themselves
    to just features that are present in GLSL/ES, and avoid
    standard variable names that only work on the desktop.

    \section1 Simple shader example

    \snippet doc/src/snippets/code/src_opengl_qglshaderprogram.cpp 1

    With the above shader program active, we can draw a green triangle
    as follows:

    \snippet doc/src/snippets/code/src_opengl_qglshaderprogram.cpp 2

    \section1 Binary shaders and programs

    Binary shaders may be specified using \c{glShaderBinary()} on
    the return value from QGLShader::shaderId().  The QGLShader instance
    containing the binary can then be added to the shader program with
    addShader() and linked in the usual fashion with link().

    Binary programs may be specified using \c{glProgramBinaryOES()}
    on the return value from programId().  Then the application should
    call link(), which will notice that the program has already been
    specified and linked, allowing other operations to be performed
    on the shader program.

    \sa QGLShader
*/

/*!
    \class QGLShader
    \brief The QGLShader class allows OpenGL shaders to be compiled.
    \since 4.6
    \ingroup painting-3D

    This class supports shaders written in the OpenGL Shading Language (GLSL)
    and in the OpenGL/ES Shading Language (GLSL/ES).

    QGLShader and QGLShaderProgram shelter the programmer from the details of
    compiling and linking vertex and fragment shaders.

    \sa QGLShaderProgram
*/

/*!
    \enum QGLShader::ShaderTypeBit
    This enum specifies the type of QGLShader that is being created.

    \value Vertex Vertex shader written in the OpenGL Shading Language (GLSL).
    \value Fragment Fragment shader written in the OpenGL Shading Language (GLSL).
*/

#ifndef GL_FRAGMENT_SHADER
#define GL_FRAGMENT_SHADER 0x8B30
#endif
#ifndef GL_VERTEX_SHADER
#define GL_VERTEX_SHADER 0x8B31
#endif
#ifndef GL_COMPILE_STATUS
#define GL_COMPILE_STATUS 0x8B81
#endif
#ifndef GL_LINK_STATUS
#define GL_LINK_STATUS 0x8B82
#endif
#ifndef GL_INFO_LOG_LENGTH
#define GL_INFO_LOG_LENGTH 0x8B84
#endif
#ifndef GL_ACTIVE_UNIFORMS
#define GL_ACTIVE_UNIFORMS 0x8B86
#endif
#ifndef GL_ACTIVE_UNIFORM_MAX_LENGTH
#define GL_ACTIVE_UNIFORM_MAX_LENGTH 0x8B87
#endif
#ifndef GL_ACTIVE_ATTRIBUTES
#define GL_ACTIVE_ATTRIBUTES 0x8B89
#endif
#ifndef GL_ACTIVE_ATTRIBUTE_MAX_LENGTH
#define GL_ACTIVE_ATTRIBUTE_MAX_LENGTH 0x8B8A
#endif
#ifndef GL_CURRENT_VERTEX_ATTRIB
#define GL_CURRENT_VERTEX_ATTRIB 0x8626
#endif
#ifndef GL_SHADER_SOURCE_LENGTH
#define GL_SHADER_SOURCE_LENGTH 0x8B88
#endif
#ifndef GL_SHADER_BINARY_FORMATS
#define GL_SHADER_BINARY_FORMATS          0x8DF8
#endif
#ifndef GL_NUM_SHADER_BINARY_FORMATS
#define GL_NUM_SHADER_BINARY_FORMATS      0x8DF9
#endif

class QGLShaderPrivate : public QObjectPrivate
{
    Q_DECLARE_PUBLIC(QGLShader)
public:
    QGLShaderPrivate(const QGLContext *context, QGLShader::ShaderType type)
        : shaderGuard(context)
        , shaderType(type)
        , compiled(false)
    {
    }
    ~QGLShaderPrivate();

    QGLSharedResourceGuard shaderGuard;
    QGLShader::ShaderType shaderType;
    bool compiled;
    QString log;

    bool create();
    bool compile(QGLShader *q);
    void deleteShader();
};

#define ctx shaderGuard.context()

QGLShaderPrivate::~QGLShaderPrivate()
{
    if (shaderGuard.id()) {
        QGLShareContextScope scope(shaderGuard.context());
        glDeleteShader(shaderGuard.id());
    }
}

bool QGLShaderPrivate::create()
{
    const QGLContext *context = shaderGuard.context();
    if (!context)
        return false;
    if (qt_resolve_glsl_extensions(const_cast<QGLContext *>(context))) {
        GLuint shader;
        if (shaderType == QGLShader::Vertex)
            shader = glCreateShader(GL_VERTEX_SHADER);
        else
            shader = glCreateShader(GL_FRAGMENT_SHADER);
        if (!shader) {
            qWarning() << "QGLShader: could not create shader";
            return false;
        }
        shaderGuard.setId(shader);
        return true;
    } else {
        return false;
    }
}

bool QGLShaderPrivate::compile(QGLShader *q)
{
    GLuint shader = shaderGuard.id();
    if (!shader)
        return false;
    glCompileShader(shader);
    GLint value = 0;
    glGetShaderiv(shader, GL_COMPILE_STATUS, &value);
    compiled = (value != 0);
    value = 0;
    glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &value);
    if (!compiled && value > 1) {
        char *logbuf = new char [value];
        GLint len;
        glGetShaderInfoLog(shader, value, &len, logbuf);
        log = QString::fromLatin1(logbuf);
        QString name = q->objectName();
        if (name.isEmpty())
            qWarning() << "QGLShader::compile:" << log;
        else
            qWarning() << "QGLShader::compile[" << name << "]:" << log;
        delete [] logbuf;
    }
    return compiled;
}

void QGLShaderPrivate::deleteShader()
{
    if (shaderGuard.id()) {
        glDeleteShader(shaderGuard.id());
        shaderGuard.setId(0);
    }
}

#undef ctx
#define ctx d->shaderGuard.context()

/*!
    Constructs a new QGLShader object of the specified \a type
    and attaches it to \a parent.  If shader programs are not supported,
    QGLShaderProgram::hasOpenGLShaderPrograms() will return false.

    This constructor is normally followed by a call to compileSourceCode()
    or compileSourceFile().

    The shader will be associated with the current QGLContext.

    \sa compileSourceCode(), compileSourceFile()
*/
QGLShader::QGLShader(QGLShader::ShaderType type, QObject *parent)
    : QObject(*new QGLShaderPrivate(QGLContext::currentContext(), type), parent)
{
    Q_D(QGLShader);
    d->create();
}

/*!
    Constructs a new QGLShader object of the specified \a type
    and attaches it to \a parent.  If shader programs are not supported,
    then QGLShaderProgram::hasOpenGLShaderPrograms() will return false.

    This constructor is normally followed by a call to compileSourceCode()
    or compileSourceFile().

    The shader will be associated with \a context.

    \sa compileSourceCode(), compileSourceFile()
*/
QGLShader::QGLShader(QGLShader::ShaderType type, const QGLContext *context, QObject *parent)
    : QObject(*new QGLShaderPrivate(context ? context : QGLContext::currentContext(), type), parent)
{
    Q_D(QGLShader);
#ifndef QT_NO_DEBUG
    if (context && !QGLContext::areSharing(context, QGLContext::currentContext())) {
        qWarning("QGLShader::QGLShader: \'context\' must be the current context or sharing with it.");
        return;
    }
#endif
    d->create();
}

/*!
    Deletes this shader.  If the shader has been attached to a
    QGLShaderProgram object, then the actual shader will stay around
    until the QGLShaderProgram is destroyed.
*/
QGLShader::~QGLShader()
{
}

/*!
    Returns the type of this shader.
*/
QGLShader::ShaderType QGLShader::shaderType() const
{
    Q_D(const QGLShader);
    return d->shaderType;
}

// The precision qualifiers are useful on OpenGL/ES systems,
// but usually not present on desktop systems.  Define the
// keywords to empty strings on desktop systems.
#ifndef QT_OPENGL_ES
#define QGL_DEFINE_QUALIFIERS 1
static const char qualifierDefines[] =
    "#define lowp\n"
    "#define mediump\n"
    "#define highp\n";
#endif

// The "highp" qualifier doesn't exist in fragment shaders
// on all ES platforms.  When it doesn't exist, use "mediump".
#ifdef QT_OPENGL_ES
#define QGL_REDEFINE_HIGHP 1
static const char redefineHighp[] =
    "#ifndef GL_FRAGMENT_PRECISION_HIGH\n"
    "#define highp mediump\n"
    "#endif\n";
#endif

/*!
    Sets the \a source code for this shader and compiles it.
    Returns true if the source was successfully compiled, false otherwise.

    \sa compileSourceFile()
*/
bool QGLShader::compileSourceCode(const char *source)
{
    Q_D(QGLShader);
    if (d->shaderGuard.id()) {
        QVarLengthArray<const char *, 4> src;
        QVarLengthArray<GLint, 4> srclen;
        int headerLen = 0;
        while (source && source[headerLen] == '#') {
            // Skip #version and #extension directives at the start of
            // the shader code.  We need to insert the qualifierDefines
            // and redefineHighp just after them.
            if (qstrncmp(source + headerLen, "#version", 8) != 0 &&
                    qstrncmp(source + headerLen, "#extension", 10) != 0) {
                break;
            }
            while (source[headerLen] != '\0' && source[headerLen] != '\n')
                ++headerLen;
            if (source[headerLen] == '\n')
                ++headerLen;
        }
        if (headerLen > 0) {
            src.append(source);
            srclen.append(GLint(headerLen));
        }
#ifdef QGL_DEFINE_QUALIFIERS
        src.append(qualifierDefines);
        srclen.append(GLint(sizeof(qualifierDefines) - 1));
#endif
#ifdef QGL_REDEFINE_HIGHP
        if (d->shaderType == Fragment) {
            src.append(redefineHighp);
            srclen.append(GLint(sizeof(redefineHighp) - 1));
        }
#endif
        src.append(source + headerLen);
        srclen.append(GLint(qstrlen(source + headerLen)));
        glShaderSource(d->shaderGuard.id(), src.size(), src.data(), srclen.data());
        return d->compile(this);
    } else {
        return false;
    }
}

/*!
    \overload

    Sets the \a source code for this shader and compiles it.
    Returns true if the source was successfully compiled, false otherwise.

    \sa compileSourceFile()
*/
bool QGLShader::compileSourceCode(const QByteArray& source)
{
    return compileSourceCode(source.constData());
}

/*!
    \overload

    Sets the \a source code for this shader and compiles it.
    Returns true if the source was successfully compiled, false otherwise.

    \sa compileSourceFile()
*/
bool QGLShader::compileSourceCode(const QString& source)
{
    return compileSourceCode(source.toLatin1().constData());
}

/*!
    Sets the source code for this shader to the contents of \a fileName
    and compiles it.  Returns true if the file could be opened and the
    source compiled, false otherwise.

    \sa compileSourceCode()
*/
bool QGLShader::compileSourceFile(const QString& fileName)
{
    QFile file(fileName);
    if (!file.open(QFile::ReadOnly)) {
        qWarning() << "QGLShader: Unable to open file" << fileName;
        return false;
    }

    QByteArray contents = file.readAll();
    return compileSourceCode(contents.constData());
}

/*!
    Returns the source code for this shader.

    \sa compileSourceCode()
*/
QByteArray QGLShader::sourceCode() const
{
    Q_D(const QGLShader);
    GLuint shader = d->shaderGuard.id();
    if (!shader)
        return QByteArray();
    GLint size = 0;
    glGetShaderiv(shader, GL_SHADER_SOURCE_LENGTH, &size);
    if (size <= 0)
        return QByteArray();
    GLint len = 0;
    char *source = new char [size];
    glGetShaderSource(shader, size, &len, source);
    QByteArray src(source);
    delete [] source;
    return src;
}

/*!
    Returns true if this shader has been compiled; false otherwise.

    \sa compileSourceCode(), compileSourceFile()
*/
bool QGLShader::isCompiled() const
{
    Q_D(const QGLShader);
    return d->compiled;
}

/*!
    Returns the errors and warnings that occurred during the last compile.

    \sa compileSourceCode(), compileSourceFile()
*/
QString QGLShader::log() const
{
    Q_D(const QGLShader);
    return d->log;
}

/*!
    Returns the OpenGL identifier associated with this shader.

    \sa QGLShaderProgram::programId()
*/
GLuint QGLShader::shaderId() const
{
    Q_D(const QGLShader);
    return d->shaderGuard.id();
}

#undef ctx
#define ctx programGuard.context()

class QGLShaderProgramPrivate : public QObjectPrivate
{
    Q_DECLARE_PUBLIC(QGLShaderProgram)
public:
    QGLShaderProgramPrivate(const QGLContext *context)
        : programGuard(context)
        , linked(false)
        , inited(false)
        , removingShaders(false)
        , vertexShader(0)
        , fragmentShader(0)
    {
    }
    ~QGLShaderProgramPrivate();

    QGLSharedResourceGuard programGuard;
    bool linked;
    bool inited;
    bool removingShaders;
    QString log;
    QList<QGLShader *> shaders;
    QList<QGLShader *> anonShaders;
    QGLShader *vertexShader;
    QGLShader *fragmentShader;

    bool hasShader(QGLShader::ShaderType type) const;
};

QGLShaderProgramPrivate::~QGLShaderProgramPrivate()
{
    if (programGuard.id()) {
        QGLShareContextScope scope(programGuard.context());
        glDeleteProgram(programGuard.id());
    }
}

bool QGLShaderProgramPrivate::hasShader(QGLShader::ShaderType type) const
{
    foreach (QGLShader *shader, shaders) {
        if (shader->shaderType() == type)
            return true;
    }
    return false;
}

#undef ctx
#define ctx d->programGuard.context()

/*!
    Constructs a new shader program and attaches it to \a parent.
    The program will be invalid until addShader() is called.

    The shader program will be associated with the current QGLContext.

    \sa addShader()
*/
QGLShaderProgram::QGLShaderProgram(QObject *parent)
    : QObject(*new QGLShaderProgramPrivate(QGLContext::currentContext()), parent)
{
}

/*!
    Constructs a new shader program and attaches it to \a parent.
    The program will be invalid until addShader() is called.

    The shader program will be associated with \a context.

    \sa addShader()
*/
QGLShaderProgram::QGLShaderProgram(const QGLContext *context, QObject *parent)
    : QObject(*new QGLShaderProgramPrivate(context), parent)
{
}

/*!
    Deletes this shader program.
*/
QGLShaderProgram::~QGLShaderProgram()
{
}

bool QGLShaderProgram::init()
{
    Q_D(QGLShaderProgram);
    if (d->programGuard.id() || d->inited)
        return true;
    d->inited = true;
    const QGLContext *context = d->programGuard.context();
    if (!context) {
        context = QGLContext::currentContext();
        d->programGuard.setContext(context);
    }
    if (!context)
        return false;
    if (qt_resolve_glsl_extensions(const_cast<QGLContext *>(context))) {
        GLuint program = glCreateProgram();
        if (!program) {
            qWarning() << "QGLShaderProgram: could not create shader program";
            return false;
        }
        d->programGuard.setId(program);
        return true;
    } else {
        qWarning() << "QGLShaderProgram: shader programs are not supported";
        return false;
    }
}

/*!
    Adds a compiled \a shader to this shader program.  Returns true
    if the shader could be added, or false otherwise.

    Ownership of the \a shader object remains with the caller.
    It will not be deleted when this QGLShaderProgram instance
    is deleted.  This allows the caller to add the same shader
    to multiple shader programs.

    \sa addShaderFromSourceCode(), addShaderFromSourceFile()
    \sa removeShader(), link(), removeAllShaders()
*/
bool QGLShaderProgram::addShader(QGLShader *shader)
{
    Q_D(QGLShaderProgram);
    if (!init())
        return false;
    if (d->shaders.contains(shader))
        return true;    // Already added to this shader program.
    if (d->programGuard.id() && shader) {
        if (!QGLContext::areSharing(shader->d_func()->shaderGuard.context(),
                                    d->programGuard.context())) {
            qWarning("QGLShaderProgram::addShader: Program and shader are not associated with same context.");
            return false;
        }
        if (!shader->d_func()->shaderGuard.id())
            return false;
        glAttachShader(d->programGuard.id(), shader->d_func()->shaderGuard.id());
        d->linked = false;  // Program needs to be relinked.
        d->shaders.append(shader);
        connect(shader, SIGNAL(destroyed()), this, SLOT(shaderDestroyed()));
        return true;
    } else {
        return false;
    }
}

/*!
    Compiles \a source as a shader of the specified \a type and
    adds it to this shader program.  Returns true if compilation
    was successful, false otherwise.  The compilation errors
    and warnings will be made available via log().

    This function is intended to be a short-cut for quickly
    adding vertex and fragment shaders to a shader program without
    creating an instance of QGLShader first.

    \sa addShader(), addShaderFromSourceFile()
    \sa removeShader(), link(), log(), removeAllShaders()
*/
bool QGLShaderProgram::addShaderFromSourceCode(QGLShader::ShaderType type, const char *source)
{
    Q_D(QGLShaderProgram);
    if (!init())
        return false;
    QGLShader *shader = new QGLShader(type, this);
    if (!shader->compileSourceCode(source)) {
        d->log = shader->log();
        delete shader;
        return false;
    }
    d->anonShaders.append(shader);
    return addShader(shader);
}

/*!
    \overload

    Compiles \a source as a shader of the specified \a type and
    adds it to this shader program.  Returns true if compilation
    was successful, false otherwise.  The compilation errors
    and warnings will be made available via log().

    This function is intended to be a short-cut for quickly
    adding vertex and fragment shaders to a shader program without
    creating an instance of QGLShader first.

    \sa addShader(), addShaderFromSourceFile()
    \sa removeShader(), link(), log(), removeAllShaders()
*/
bool QGLShaderProgram::addShaderFromSourceCode(QGLShader::ShaderType type, const QByteArray& source)
{
    return addShaderFromSourceCode(type, source.constData());
}

/*!
    \overload

    Compiles \a source as a shader of the specified \a type and
    adds it to this shader program.  Returns true if compilation
    was successful, false otherwise.  The compilation errors
    and warnings will be made available via log().

    This function is intended to be a short-cut for quickly
    adding vertex and fragment shaders to a shader program without
    creating an instance of QGLShader first.

    \sa addShader(), addShaderFromSourceFile()
    \sa removeShader(), link(), log(), removeAllShaders()
*/
bool QGLShaderProgram::addShaderFromSourceCode(QGLShader::ShaderType type, const QString& source)
{
    return addShaderFromSourceCode(type, source.toLatin1().constData());
}

/*!
    Compiles the contents of \a fileName as a shader of the specified
    \a type and adds it to this shader program.  Returns true if
    compilation was successful, false otherwise.  The compilation errors
    and warnings will be made available via log().

    This function is intended to be a short-cut for quickly
    adding vertex and fragment shaders to a shader program without
    creating an instance of QGLShader first.

    \sa addShader(), addShaderFromSourceCode()
*/
bool QGLShaderProgram::addShaderFromSourceFile
    (QGLShader::ShaderType type, const QString& fileName)
{
    Q_D(QGLShaderProgram);
    if (!init())
        return false;
    QGLShader *shader = new QGLShader(type, this);
    if (!shader->compileSourceFile(fileName)) {
        d->log = shader->log();
        delete shader;
        return false;
    }
    d->anonShaders.append(shader);
    return addShader(shader);
}

/*!
    Removes \a shader from this shader program.  The object is not deleted.

    \sa addShader(), link(), removeAllShaders()
*/
void QGLShaderProgram::removeShader(QGLShader *shader)
{
    Q_D(QGLShaderProgram);
    if (d->programGuard.id() && shader && shader->d_func()->shaderGuard.id()) {
        QGLShareContextScope scope(d->programGuard.context());
        glDetachShader(d->programGuard.id(), shader->d_func()->shaderGuard.id());
    }
    d->linked = false;  // Program needs to be relinked.
    if (shader) {
        d->shaders.removeAll(shader);
        d->anonShaders.removeAll(shader);
        disconnect(shader, SIGNAL(destroyed()), this, SLOT(shaderDestroyed()));
    }
}

/*!
    Returns a list of all shaders that have been added to this shader
    program using addShader().

    \sa addShader(), removeShader()
*/
QList<QGLShader *> QGLShaderProgram::shaders() const
{
    Q_D(const QGLShaderProgram);
    return d->shaders;
}

/*!
    Removes all of the shaders that were added to this program previously.
    The QGLShader objects for the shaders will not be deleted if they
    were constructed externally.  QGLShader objects that are constructed
    internally by QGLShaderProgram will be deleted.

    \sa addShader(), removeShader()
*/
void QGLShaderProgram::removeAllShaders()
{
    Q_D(QGLShaderProgram);
    d->removingShaders = true;
    foreach (QGLShader *shader, d->shaders) {
        if (d->programGuard.id() && shader && shader->d_func()->shaderGuard.id())
            glDetachShader(d->programGuard.id(), shader->d_func()->shaderGuard.id());
    }
    foreach (QGLShader *shader, d->anonShaders) {
        // Delete shader objects that were created anonymously.
        delete shader;
    }
    d->shaders.clear();
    d->anonShaders.clear();
    d->linked = false;  // Program needs to be relinked.
    d->removingShaders = false;
}

/*!
    Links together the shaders that were added to this program with
    addShader().  Returns true if the link was successful or
    false otherwise.  If the link failed, the error messages can
    be retrieved with log().

    Subclasses can override this function to initialize attributes
    and uniform variables for use in specific shader programs.

    If the shader program was already linked, calling this
    function again will force it to be re-linked.

    \sa addShader(), log()
*/
bool QGLShaderProgram::link()
{
    Q_D(QGLShaderProgram);
    GLuint program = d->programGuard.id();
    if (!program)
        return false;
    GLint value;
    if (d->shaders.isEmpty()) {
        // If there are no explicit shaders, then it is possible that the
        // application added a program binary with glProgramBinaryOES(),
        // or otherwise populated the shaders itself.  Check to see if the
        // program is already linked and bail out if so.
        value = 0;
        glGetProgramiv(program, GL_LINK_STATUS, &value);
        d->linked = (value != 0);
        if (d->linked)
            return true;
    }
    glLinkProgram(program);
    value = 0;
    glGetProgramiv(program, GL_LINK_STATUS, &value);
    d->linked = (value != 0);
    value = 0;
    glGetProgramiv(program, GL_INFO_LOG_LENGTH, &value);
    d->log = QString();
    if (value > 1) {
        char *logbuf = new char [value];
        GLint len;
        glGetProgramInfoLog(program, value, &len, logbuf);
        d->log = QString::fromLatin1(logbuf);
        QString name = objectName();
        if (name.isEmpty())
            qWarning() << "QGLShader::link:" << d->log;
        else
            qWarning() << "QGLShader::link[" << name << "]:" << d->log;
        delete [] logbuf;
    }
    return d->linked;
}

/*!
    Returns true if this shader program has been linked; false otherwise.

    \sa link()
*/
bool QGLShaderProgram::isLinked() const
{
    Q_D(const QGLShaderProgram);
    return d->linked;
}

/*!
    Returns the errors and warnings that occurred during the last link()
    or addShader() with explicitly specified source code.

    \sa link()
*/
QString QGLShaderProgram::log() const
{
    Q_D(const QGLShaderProgram);
    return d->log;
}

/*!
    Binds this shader program to the active QGLContext and makes
    it the current shader program.  Any previously bound shader program
    is released.  This is equivalent to calling \c{glUseProgram()} on
    programId().  Returns true if the program was successfully bound;
    false otherwise.  If the shader program has not yet been linked,
    or it needs to be re-linked, this function will call link().

    \sa link(), release()
*/
bool QGLShaderProgram::bind()
{
    Q_D(QGLShaderProgram);
    GLuint program = d->programGuard.id();
    if (!program)
        return false;
    if (!d->linked && !link())
        return false;
#ifndef QT_NO_DEBUG
    if (!QGLContext::areSharing(d->programGuard.context(), QGLContext::currentContext())) {
        qWarning("QGLShaderProgram::bind: program is not valid in the current context.");
        return false;
    }
#endif
    glUseProgram(program);
    return true;
}