outline_decomposer.h

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/*
 * This program source code file is part of KICAD, a free EDA CAD application.
 *
 * Copyright (C) 2021 Ola Rinta-Koski
 * Copyright The KiCad Developers, see AUTHORS.txt for contributors.
 *
 * Outline font class
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
#ifndef OUTLINE_DECOMPOSER_H
#define OUTLINE_DECOMPOSER_H
 
#include <vector>
#ifdef _MSC_VER
#include <ft2build.h>
#else
#include <freetype2/ft2build.h>
#endif
#include FT_FREETYPE_H
#include FT_OUTLINE_H
#include <math/box2.h>
#include <math/vector2d.h>
#include <font/glyph.h>
#include <geometry/shape_poly_set.h>
 
namespace KIFONT
{
 
constexpr int GLYPH_DEFAULT_DPI = 72;  
 
// The FreeType default of 72 DPI is not enough for outline decomposition;
// so we'll use something larger than that.
constexpr int GLYPH_RESOLUTION  = 1152;
constexpr double GLYPH_SIZE_SCALER = GLYPH_DEFAULT_DPI / (double) GLYPH_RESOLUTION;
 
struct CONTOUR
{
    std::vector<VECTOR2D> m_Points;
    int                   m_Winding = 0;
    FT_Orientation        m_Orientation;
};
 
struct GLYPH_DATA
{
    std::vector<CONTOUR> m_Contours;
 
    // Cache of the triangulation data.  We'll use this as a hint for triangulating the actual
    // OUTLINE_GLYPHs.
    std::vector<std::unique_ptr<SHAPE_POLY_SET::TRIANGULATED_POLYGON>> m_TriangulationData;
 
    // Glyphs with no outline (e.g. a space) legitimately decompose to zero contours, so cache
    // occupancy can't key off m_Contours alone.
    bool m_Loaded = false;
};
 
 
class OUTLINE_DECOMPOSER
{
public:
    OUTLINE_DECOMPOSER( FT_Outline& aOutline );
 
    bool OutlineToSegments( std::vector<CONTOUR>* aContours );
 
private:
    void newContour();
 
    void addContourPoint( const VECTOR2D& p );

    int winding( const std::vector<VECTOR2D>& aContour ) const;
 
    inline static unsigned int onCurve( char aTags )
    {
        return aTags & 0x1;
    }
 
    inline static unsigned int thirdOrderBezierPoint( char aTags )
    {
        return onCurve( aTags ) ? 0 : aTags & 0x2;
    }
 
    inline static unsigned int secondOrderBezierPoint( char aTags )
    {
        return onCurve( aTags ) ? 0 : !thirdOrderBezierPoint( aTags );
    }
 
    inline static unsigned int hasDropout( char aTags )
    {
        return aTags & 0x4;
    }
 
    inline static unsigned int dropoutMode( char aTags )
    {
        return hasDropout( aTags ) ? ( aTags & 0x38 ) : 0;
    }
 
    // FT_Outline_Decompose callbacks
    static int moveTo( const FT_Vector* aEndPoint, void* aCallbackData );
 
    static int lineTo( const FT_Vector* aEndPoint, void* aCallbackData );
 
    static int quadraticTo( const FT_Vector* aControlPoint, const FT_Vector* aEndPoint,
                            void* aCallbackData );
 
    static int cubicTo( const FT_Vector* aFirstControlPoint, const FT_Vector* aSecondControlPoint,
                        const FT_Vector* aEndPoint, void* aCallbackData );
 
private:
    FT_Outline&           m_outline;
    std::vector<CONTOUR>* m_contours;
 
    VECTOR2D              m_lastEndPoint;
};
 
} //namespace KIFONT
 
#endif      // OUTLINE_DECOMPOSER_H