CrossProcessFontLoading.h   [plain text]

/*
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#ifndef CrossProcessFontLoading_h
#define CrossProcessFontLoading_h

#import <wtf/RefCounted.h>
#import <wtf/RetainPtr.h>

typedef struct CGFont* CGFontRef;
typedef UInt32 ATSFontContainerRef;
typedef UInt32 ATSFontRef;

namespace WebCore {

// MemoryActivatedFont encapsulates a font loaded from another process and
// activated from memory.
//
// Responsibilities:
// * Holder for the CGFontRef & ATSFontRef belonging to the activated font.
// * Responsible for unloading the font container when done.
//
// Memory Management:
// The class is reference counted, with each instance of FontPlatformData that
// uses this class holding a reference to it.
// Entries are kept track of internally in a hash to allow quick lookup
// of existing instances for reuse:
// - fontCacheBySrcFontContainerRef() - key is the ATSFontContainerRef
//   corresponding to the *original in-process NSFont* whose loading was blocked
//   by the sandbox.
//   This is needed to allow lookup of a pre-existing MemoryActivatedFont when
//   creating a new FontPlatformData object.
//
// Assumptions:
// This code assumes that an ATSFontRef is a unique identifier tied to an
// activated font.  i.e. After we activate a font, its ATSFontRef doesn't
// change.
// It also assumes that the ATSFoncontainerRef for two in-memory NSFonts that
// correspond to the same on-disk font file are always the same and don't change
// with time.
//
// Flushing caches:
// When the system notifies us of a system font cache flush, all FontDataCache
// objects are destroyed.  This should in turn dereference all
// MemoryActivatedFonts and thus unload all in-memory fonts.
class MemoryActivatedFont : public RefCounted<MemoryActivatedFont> {
public:
    // Use to create a new object, see docs on constructor below.
    static PassRefPtr<MemoryActivatedFont> create(ATSFontContainerRef srcFontContainerRef, ATSFontContainerRef container);
    ~MemoryActivatedFont();
    
    // Get cached CGFontRef corresponding to the in-memory font.
    CGFontRef cgFont() { return m_cgFont.get(); }
    
    // Get cached ATSFontRef corresponding to the in-memory font.
    ATSFontRef atsFontRef() { return m_atsFontRef; }

private:
    // srcFontRef - ATSFontRef belonging to the NSFont object that failed to
    // load in-process.
    // container - a font container corresponding to an identical font that
    // we loaded cross-process.
    MemoryActivatedFont(ATSFontContainerRef srcFontContainerRef, ATSFontContainerRef container);

    ATSFontContainerRef m_fontContainer;
    WTF::RetainPtr<CGFontRef> m_cgFont;
    ATSFontRef m_atsFontRef;
    ATSFontContainerRef m_srcFontContainerRef;
};

} // namespace WebCore

#endif // CrossProcessFontLoading_h