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  #ifndef QSGOPENGLDISTANCEFIELDGLYPHCACHE_H
  #define QSGOPENGLDISTANCEFIELDGLYPHCACHE_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 "qsgadaptationlayer_p.h"
  #include <QtGui/qopenglfunctions.h>
  #include <qopenglshaderprogram.h>
  #include <qopenglbuffer.h>
  #include <qopenglvertexarrayobject.h>
  #include <QtGui/private/qopenglengineshadersource_p.h>
  #include <private/qsgareaallocator_p.h>
  
  QT_BEGIN_NAMESPACE
  
  class QOpenGLSharedResourceGuard;
  #if !defined(QT_OPENGL_ES_2)
  class QOpenGLFunctions_3_2_Core;
  #endif
  
  class Q_QUICK_PRIVATE_EXPORT QSGOpenGLDistanceFieldGlyphCache : public QSGDistanceFieldGlyphCache
  {
  public:
      QSGOpenGLDistanceFieldGlyphCache(QOpenGLContext *c, const QRawFont &font);
      virtual ~QSGOpenGLDistanceFieldGlyphCache();
  
      void requestGlyphs(const QSet<glyph_t> &glyphs) override;
      void storeGlyphs(const QList<QDistanceField> &glyphs) override;
      void referenceGlyphs(const QSet<glyph_t> &glyphs) override;
      void releaseGlyphs(const QSet<glyph_t> &glyphs) override;
  
      bool useTextureResizeWorkaround() const;
      bool useTextureUploadWorkaround() const;
      bool createFullSizeTextures() const;
  
      void setMaxTextureCount(int max) { m_maxTextureCount = max; }
      int maxTextureCount() const { return m_maxTextureCount; }
  
      bool eightBitFormatIsAlphaSwizzled() const override { return !m_coreProfile; }
  
  private:
      bool loadPregeneratedCache(const QRawFont &font);
      inline bool isCoreProfile() const { return m_coreProfile; }
  
      struct TextureInfo {
          GLuint texture;
          QSize size;
          QRect allocatedArea;
          QDistanceField image;
          int padding = -1;
  
          TextureInfo(const QRect &preallocRect = QRect(0, 0, 1, 1)) : texture(0), allocatedArea(preallocRect) { }
      };
  
      void createTexture(TextureInfo * texInfo, int width, int height, const void *pixels);
      void createTexture(TextureInfo * texInfo, int width, int height);
      void resizeTexture(TextureInfo * texInfo, int width, int height);
  
      TextureInfo *textureInfo(int index)
      {
          Q_ASSERT(m_maxTextureWidth > 0 && m_maxTextureHeight > 0);
          for (int i = m_textures.count(); i <= index; ++i) {
              if (createFullSizeTextures())
                  m_textures.append(QRect(0, 0, m_maxTextureWidth, m_maxTextureWidth));
              else
                  m_textures.append(TextureInfo());
          }
  
          return &m_textures[index];
      }
  
      void createBlitProgram()
      {
          m_blitProgram = new QOpenGLShaderProgram;
          {
              const QString source = QLatin1String(qopenglslMainWithTexCoordsVertexShader)
                                   + QLatin1String(qopenglslUntransformedPositionVertexShader);
  
              m_blitProgram->addCacheableShaderFromSourceCode(QOpenGLShader::Vertex, source);
          }
          {
              const QString source = QLatin1String(qopenglslMainFragmentShader)
                                   + QLatin1String(qopenglslImageSrcFragmentShader);
  
              m_blitProgram->addCacheableShaderFromSourceCode(QOpenGLShader::Fragment, source);
          }
          m_blitProgram->bindAttributeLocation("vertexCoordsArray", QT_VERTEX_COORDS_ATTR);
          m_blitProgram->bindAttributeLocation("textureCoordArray", QT_TEXTURE_COORDS_ATTR);
          m_blitProgram->link();
      }
  
      int m_maxTextureWidth;
      int m_maxTextureHeight;
      int m_maxTextureCount;
      bool m_coreProfile;
  
      QList<TextureInfo> m_textures;
      QHash<glyph_t, TextureInfo *> m_glyphsTexture;
      QSet<glyph_t> m_unusedGlyphs;
  
      QSGAreaAllocator *m_areaAllocator;
  
      QOpenGLShaderProgram *m_blitProgram;
      QOpenGLBuffer m_blitBuffer;
      QOpenGLVertexArrayObject m_vao;
  
      QOpenGLSharedResourceGuard *m_fboGuard;
      QOpenGLFunctions *m_funcs;
  #if !defined(QT_OPENGL_ES_2)
      QOpenGLFunctions_3_2_Core *m_coreFuncs;
  #endif
  };
  
  QT_END_NAMESPACE
  
  #endif // QSGOPENGLDISTANCEFIELDGLYPHCACHE_H
  