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** Copyright (C) 2016 The Qt Company Ltd.
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#ifndef QTEXTUREGLYPHCACHE_GL_P_H
#define QTEXTUREGLYPHCACHE_GL_P_H

//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//

#include <private/qtextureglyphcache_p.h>
#include <private/qgl_p.h>
#include <qglshaderprogram.h>
#include <qglframebufferobject.h>
#include <qopenglfunctions.h>

// #define QT_GL_TEXTURE_GLYPH_CACHE_DEBUG

QT_BEGIN_NAMESPACE

class QGL2PaintEngineExPrivate;

struct QGLGlyphTexture : public QOpenGLSharedResource
{
    QGLGlyphTexture(const QGLContext *ctx)
        : QOpenGLSharedResource(ctx->contextHandle()->shareGroup())
        , m_fbo(0)
        , m_width(0)
        , m_height(0)
    {
        if (ctx && QGLFramebufferObject::hasOpenGLFramebufferObjects() && !ctx->d_ptr->workaround_brokenFBOReadBack)
            ctx->contextHandle()->functions()->glGenFramebuffers(1, &m_fbo);

#ifdef QT_GL_TEXTURE_GLYPH_CACHE_DEBUG
        qDebug(" -> QGLGlyphTexture() %p for context %p.", this, ctx);
#endif
    }

    void freeResource(QOpenGLContext *context) override
    {
        const QGLContext *ctx = QGLContext::fromOpenGLContext(context);
#ifdef QT_GL_TEXTURE_GLYPH_CACHE_DEBUG
        qDebug("~QGLGlyphTexture() %p for context %p.", this, ctx);
#else
        Q_UNUSED(ctx);
#endif
        if (ctx && m_fbo)
            ctx->contextHandle()->functions()->glDeleteFramebuffers(1, &m_fbo);
        if (m_width || m_height)
            ctx->contextHandle()->functions()->glDeleteTextures(1, &m_texture);
    }

    void invalidateResource() override
    {
        m_texture = 0;
        m_fbo = 0;
        m_width = 0;
        m_height = 0;
    }

    GLuint m_texture;
    GLuint m_fbo;
    int m_width;
    int m_height;
};

class Q_OPENGL_EXPORT QGLTextureGlyphCache : public QImageTextureGlyphCache
{
public:
    QGLTextureGlyphCache(QFontEngine::GlyphFormat format, const QTransform &matrix);
    ~QGLTextureGlyphCache();

    virtual void createTextureData(int width, int height) override;
    virtual void resizeTextureData(int width, int height) override;
    virtual void fillTexture(const Coord &c, glyph_t glyph, QFixed subPixelPosition) override;
    virtual int glyphPadding() const override;
    virtual int maxTextureWidth() const override;
    virtual int maxTextureHeight() const override;

    inline GLuint texture() const {
        QGLTextureGlyphCache *that = const_cast<QGLTextureGlyphCache *>(this);
        QGLGlyphTexture *glyphTexture = that->m_textureResource;
        return glyphTexture ? glyphTexture->m_texture : 0;
    }

    inline int width() const {
        QGLTextureGlyphCache *that = const_cast<QGLTextureGlyphCache *>(this);
        QGLGlyphTexture *glyphTexture = that->m_textureResource;
        return glyphTexture ? glyphTexture->m_width : 0;
    }
    inline int height() const {
        QGLTextureGlyphCache *that = const_cast<QGLTextureGlyphCache *>(this);
        QGLGlyphTexture *glyphTexture = that->m_textureResource;
        return glyphTexture ? glyphTexture->m_height : 0;
    }

    inline void setPaintEnginePrivate(QGL2PaintEngineExPrivate *p) { pex = p; }

    inline const QOpenGLContextGroup *contextGroup() const { return m_textureResource ? m_textureResource->group() : nullptr; }

    inline int serialNumber() const { return m_serialNumber; }

    enum FilterMode {
        Nearest,
        Linear
    };
    FilterMode filterMode() const { return m_filterMode; }
    void setFilterMode(FilterMode m) { m_filterMode = m; }

    void clear();

private:
    QGLGlyphTexture *m_textureResource;

    QGL2PaintEngineExPrivate *pex;
    QGLShaderProgram *m_blitProgram;
    FilterMode m_filterMode;

    GLfloat m_vertexCoordinateArray[8];
    GLfloat m_textureCoordinateArray[8];

    int m_serialNumber;
};

QT_END_NAMESPACE

#endif