src/pdf/SkPDFFont.h

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */


#ifndef SkPDFFont_DEFINED
#define SkPDFFont_DEFINED

#include "SkAdvancedTypefaceMetrics.h"
#include "SkBitSet.h"
#include "SkPDFTypes.h"
#include "SkTDArray.h"
#include "SkTypeface.h"

class SkPDFCanon;
class SkPDFFont;

/** \class SkPDFFont
    A PDF Object class representing a font.  The font may have resources
    attached to it in order to embed the font.  SkPDFFonts are canonicalized
    so that resource deduplication will only include one copy of a font.
    This class uses the same pattern as SkPDFGraphicState, a static weak
    reference to each instantiated class.
*/
class SkPDFFont : public SkPDFDict {

public:
    virtual ~SkPDFFont();

    /** Returns the typeface represented by this class. Returns nullptr for the
     *  default typeface.
     */
    SkTypeface* typeface() const { return fTypeface.get(); }

    /** Returns the font type represented in this font.  For Type0 fonts,
     *  returns the type of the decendant font.
     */
    SkAdvancedTypefaceMetrics::FontType getType() const { return fFontType; }

    static SkAdvancedTypefaceMetrics::FontType FontType(const SkAdvancedTypefaceMetrics&);

    static bool IsMultiByte(SkAdvancedTypefaceMetrics::FontType type) {
        return type == SkAdvancedTypefaceMetrics::kType1CID_Font ||
               type == SkAdvancedTypefaceMetrics::kTrueType_Font;
    }

    /** Returns true if this font encoding supports glyph IDs above 255.
     */
    bool multiByteGlyphs() const { return SkPDFFont::IsMultiByte(this->getType()); }

    /** Return true if this font has an encoding for the passed glyph id.
     */
    bool hasGlyph(SkGlyphID gid) {
        return (gid >= fFirstGlyphID && gid <= fLastGlyphID) || gid == 0;
    }

    /** Convert the input glyph ID into the font encoding.  */
    SkGlyphID glyphToPDFFontEncoding(SkGlyphID gid) const {
        if (this->multiByteGlyphs() || gid == 0) {
            return gid;
        }
        SkASSERT(gid >= fFirstGlyphID && gid <= fLastGlyphID);
        SkASSERT(fFirstGlyphID > 0);
        return gid - fFirstGlyphID + 1;
    }

    void noteGlyphUsage(SkGlyphID glyph) {
        SkASSERT(this->hasGlyph(glyph));
        fGlyphUsage.set(glyph);
    }

    /** Get the font resource for the passed typeface and glyphID. The
     *  reference count of the object is incremented and it is the caller's
     *  responsibility to unreference it when done.  This is needed to
     *  accommodate the weak reference pattern used when the returned object
     *  is new and has no other references.
     *  @param typeface  The typeface to find, not nullptr.
     *  @param glyphID   Specify which section of a large font is of interest.
     */
    static SkPDFFont* GetFontResource(SkPDFCanon* canon,
                                      SkTypeface* typeface,
                                      SkGlyphID glyphID);

    /** Uses (kGlyphNames_PerGlyphInfo | kToUnicode_PerGlyphInfo) to get 
     *  SkAdvancedTypefaceMetrics, and caches the result.
     *  @param typeface can not be nullptr.
     *  @return nullptr only when typeface is bad.
     */
    static const SkAdvancedTypefaceMetrics* GetMetrics(SkTypeface* typeface,
                                                       SkPDFCanon* canon);

    /** Subset the font based on current usage.
     *  Must be called before emitObject().
     */
    virtual void getFontSubset(SkPDFCanon*) = 0;

    /**
     *  Return false iff the typeface has its NotEmbeddable flag set.
     *  typeface is not nullptr
     */
    static bool CanEmbedTypeface(SkTypeface*, SkPDFCanon*);

protected:
    // Common constructor to handle common members.
    struct Info {
        sk_sp<SkTypeface> fTypeface;
        SkGlyphID fFirstGlyphID;
        SkGlyphID fLastGlyphID;
        SkAdvancedTypefaceMetrics::FontType fFontType;
    };
    SkPDFFont(Info);

    SkGlyphID firstGlyphID() const { return fFirstGlyphID; }
    SkGlyphID lastGlyphID() const { return fLastGlyphID; }
    const SkBitSet& glyphUsage() const { return fGlyphUsage; }
    sk_sp<SkTypeface> refTypeface() const { return fTypeface; }

    void drop() override;

private:
    sk_sp<SkTypeface> fTypeface;
    SkBitSet fGlyphUsage;

    // The glyph IDs accessible with this font.  For Type1 (non CID) fonts,
    // this will be a subset if the font has more than 255 glyphs.
    const SkGlyphID fFirstGlyphID;
    const SkGlyphID fLastGlyphID;
    const SkAdvancedTypefaceMetrics::FontType fFontType;

    typedef SkPDFDict INHERITED;
};

#endif