qgis源码学习3之core模块的qgis.h文件

这是文件是整个软件的基础文件。里面主要定义了一个QGis这个类。类里面定义了版本信息、各种基础的类型例如：图元类型、单位类型、几何类型、基础的数据类型、event类型。和一些基础的函数，例如double转字符串函数。下面对qgis.h进行了注释。

/***************************************************************************                          qgis.h - QGIS namespace                             -------------------    begin                : Sat Jun 30 2002    copyright            : (C) 2002 by Gary E.Sherman    email                : sherman at mrcc.com ***************************************************************************//*************************************************************************** *                                                                         * *   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.                                   * *                                                                         * ***************************************************************************/#ifndef QGIS_H#define QGIS_H#include <QEvent>#include <QString>#include <QRegExp>#include <QMetaType>#include <QVariant>#include <stdlib.h>#include <cfloat>#include <cmath>#include <qnumeric.h>/** \ingroup core * The QGis class provides global constants for use throughout the application. */class CORE_EXPORT QGis{  public:    // Version constants    //    // Version string版本信息    static const char* QGIS_VERSION;    // Version number used for comparing versions using the "Check QGIS Version" function    static const int QGIS_VERSION_INT;    // Release name    static const char* QGIS_RELEASE_NAME;    // The development version    static const char* QGIS_DEV_VERSION;    // Enumerations    //    //! Used for symbology operations    // Feature types图元的类型    enum WkbType    {      WKBUnknown = 0,      WKBPoint = 1,//点      WKBLineString,      WKBPolygon,      WKBMultiPoint,      WKBMultiLineString,      WKBMultiPolygon,      WKBNoGeometry = 100, //attributes only      WKBPoint25D = 0x80000001,      WKBLineString25D,      WKBPolygon25D,      WKBMultiPoint25D,      WKBMultiLineString25D,      WKBMultiPolygon25D,    };    static WkbType singleType( WkbType type )//图元的多个类型对应的单类型    {      switch ( type )      {        case WKBMultiPoint:         return WKBPoint;//例如这个，多个点自然是由很多单个点组成的。        case WKBMultiLineString:    return WKBLineString;        case WKBMultiPolygon:       return WKBPolygon;        case WKBMultiPoint25D:      return WKBPoint25D;        case WKBMultiLineString25D: return WKBLineString25D;        case WKBMultiPolygon25D:    return WKBPolygon25D;        default:                    return type;      }    }    static WkbType multiType( WkbType type )//图元的单类型对应的多类型    {      switch ( type )      {        case WKBPoint:         return WKBMultiPoint;        case WKBLineString:    return WKBMultiLineString;        case WKBPolygon:       return WKBMultiPolygon;        case WKBPoint25D:      return WKBMultiPoint25D;        case WKBLineString25D: return WKBMultiLineString25D;        case WKBPolygon25D:    return WKBMultiPolygon25D;        default:               return type;      }    }    static WkbType flatType( WkbType type )//没有用过这个函数，暂时不知道    {      switch ( type )      {        case WKBPoint25D:           return WKBPoint;        case WKBLineString25D:      return WKBLineString;        case WKBPolygon25D:         return WKBPolygon;        case WKBMultiPoint25D:      return WKBMultiPoint;        case WKBMultiLineString25D: return WKBMultiLineString;        case WKBMultiPolygon25D:    return WKBMultiPolygon;        default:                    return type;      }    }    static bool isSingleType( WkbType type )//是不是单类型    {      switch ( flatType( type ) )      {        case WKBPoint:        case WKBLineString:        case WKBPolygon:          return true;        default:          return false;      }    }    static bool isMultiType( WkbType type )//是不是多类型    {      switch ( flatType( type ) )      {        case WKBMultiPoint:        case WKBMultiLineString:        case WKBMultiPolygon:          return true;        default:          return false;      }    }    static int wkbDimensions( WkbType type )//这个图元对应的是几维的    {      switch ( type )      {        case WKBUnknown:            return 0;        case WKBNoGeometry:         return 0;        case WKBPoint25D:           return 3;//这种类型的是3维的        case WKBLineString25D:      return 3;        case WKBPolygon25D:         return 3;        case WKBMultiPoint25D:      return 3;        case WKBMultiLineString25D: return 3;        case WKBMultiPolygon25D:    return 3;        default:                    return 2;      }    }    enum GeometryType//几何类型。图元中包含几何这个成员。    {      Point,      Line,      Polygon,//多边形      UnknownGeometry,      NoGeometry    };    //! description strings for geometry types    static const char *vectorGeometryType( GeometryType type )//几何类型的描述，这个函数应该不支持国际化吧    {      switch ( type )      {        case Point:           return "Point";        case Line:            return "Line";        case Polygon:         return "Polygon";        case UnknownGeometry: return "Unknown geometry";        case NoGeometry:      return "No geometry";        default:              return "Invalid type";      }    }    //! description strings for feature types    static const char *featureType( WkbType type )//得到图元的描述字符串    {      switch ( type )      {        case WKBUnknown:            return "WKBUnknown";        case WKBPoint:              return "WKBPoint";        case WKBLineString:         return "WKBLineString";        case WKBPolygon:            return "WKBPolygon";        case WKBMultiPoint:         return "WKBMultiPoint";        case WKBMultiLineString:    return "WKBMultiLineString";        case WKBMultiPolygon:       return "WKBMultiPolygon";        case WKBNoGeometry:         return "WKBNoGeometry";        case WKBPoint25D:           return "WKBPoint25D";        case WKBLineString25D:      return "WKBLineString25D";        case WKBPolygon25D:         return "WKBPolygon25D";        case WKBMultiPoint25D:      return "WKBMultiPoint25D";        case WKBMultiLineString25D: return "WKBMultiLineString25D";        case WKBMultiPolygon25D:    return "WKBMultiPolygon25D";        default:                    return "invalid wkbtype";      }    }    /** Raster data types.     *  This is modified and extended copy of GDALDataType.     */    enum DataType//数据类型。相当重要。    {      /*! Unknown or unspecified type */                UnknownDataType = 0,      /*! Eight bit unsigned integer (quint8) */        Byte = 1,      /*! Sixteen bit unsigned integer (quint16) */     UInt16 = 2,      /*! Sixteen bit signed integer (qint16) */        Int16 = 3,      /*! Thirty two bit unsigned integer (quint32) */  UInt32 = 4,      /*! Thirty two bit signed integer (qint32) */     Int32 = 5,      /*! Thirty two bit floating point (float) */      Float32 = 6,      /*! Sixty four bit floating point (double) */     Float64 = 7,      /*! Complex Int16 */                              CInt16 = 8,      /*! Complex Int32 */                              CInt32 = 9,      /*! Complex Float32 */                            CFloat32 = 10,      /*! Complex Float64 */                            CFloat64 = 11,      /*! Color, alpha, red, green, blue, 4 bytes the same as          QImage::Format_ARGB32 */                      ARGB32 = 12,      /*! Color, alpha, red, green, blue, 4 bytes  the same as          QImage::Format_ARGB32_Premultiplied */        ARGB32_Premultiplied = 13    };    /** Map units that qgis supports     * @note that QGIS < 1.4 api had only Meters, Feet, Degrees and UnknownUnit     * @note and QGIS >1.8 returns to that     */    enum UnitType//单位类型    {      Meters = 0,//米      Feet = 1,//英尺      Degrees = 2, //for 1.0 api backwards compatibility      UnknownUnit = 3,      // for [1.4;1.8] api compatibility      DecimalDegrees = 2,         // was 2      DegreesMinutesSeconds = 2,  // was 4      DegreesDecimalMinutes = 2,  // was 5      NauticalMiles = 7    };    //! Provides the canonical name of the type value    // Added in version 2.0把对应的单位转换为可以显示的字符串，内部的实现是通过查一个数组qgisUnitTypes[]    //来实现的。    static QString toLiteral( QGis::UnitType unit );    //! Converts from the canonical name to the type value    // Added in version 2.0把字符串转换为对应的单位类型。同样是通过查找qgisUnitTypes[]实现的    static UnitType fromLiteral( QString  literal, QGis::UnitType defaultType = UnknownUnit );    //! Provides translated version of the type value    // Added in version 2.0    static QString tr( QGis::UnitType unit );    //! Returns the conversion factor between the specified units    static double fromUnitToUnitFactor( QGis::UnitType fromUnit, QGis::UnitType toUnit );    //! User defined event types    enum UserEvent    {      // These first two are useful for threads to alert their parent data providers      //! The extents have been calculated by a provider of a layer      ProviderExtentCalcEvent = ( QEvent::User + 1 ),//计算完毕图层的延展（显示用的），可以简单的认为是缩放。      //! The row count has been calculated by a provider of a layer      ProviderCountCalcEvent//这里耍了个小技巧，enum类型可以自动++。没有用过这个event    };    /** Old search radius in % of canvas width     *  @deprecated since 2.3, use DEFAULT_SEARCH_RADIUS_MM */    static const double DEFAULT_IDENTIFY_RADIUS;    /** Identify search radius in mm     *  @note added in 2.3 */    static const double DEFAULT_SEARCH_RADIUS_MM;    //! Default threshold between map coordinates and device coordinates for map2pixel simplification    static const float DEFAULT_MAPTOPIXEL_THRESHOLD;    /** Default highlight color.  The transparency is expected to only be applied to polygon     *  fill. Lines and outlines are rendered opaque.     *  @note added in 2.3 */    static const QColor DEFAULT_HIGHLIGHT_COLOR;    /** Default highlight buffer in mm.     *  @note added in 2.3 */    static double DEFAULT_HIGHLIGHT_BUFFER_MM;    /** Default highlight line/outline minimum width in mm.     *  @note added in 2.3 */    static double DEFAULT_HIGHLIGHT_MIN_WIDTH_MM;  private:    // String representation of unit types (set in qgis.cpp)    static const char *qgisUnitTypes[];};// hack to workaround warnings when casting void pointers// retrieved from QLibrary::resolve to function pointers.// It's assumed that this works on all systems supporting// QLibraryinline void ( *cast_to_fptr( void *p ) )(){  union  {    void *p;    void ( *f )();  } u;  u.p = p;  return u.f;}//// return a string representation of a double//inline QString qgsDoubleToString( const double &a )//把double类型转换为字符串{  return QString::number( a, 'f', 17 ).remove( QRegExp( "\\.?0+$" ) );}//// compare two doubles (but allow some difference)//inline bool qgsDoubleNear( double a, double b, double epsilon = 4 * DBL_EPSILON ){  const double diff = a - b;  return diff > -epsilon && diff <= epsilon;}//// compare two doubles using specified number of significant digits//inline bool qgsDoubleNearSig( double a, double b, int significantDigits = 10 ){  // The most simple would be to print numbers as %.xe and compare as strings  // but that is probably too costly  // Then the fastest would be to set some bits directly, but little/big endian  // has to be considered (maybe TODO)  // Is there a better way?  int aexp, bexp;  double ar = frexp( a, &aexp );  double br = frexp( b, &bexp );  return aexp == bexp &&         qRound( ar * pow( 10.0, significantDigits ) ) == qRound( br * pow( 10.0, significantDigits ) ) ;}bool qgsVariantLessThan( const QVariant& lhs, const QVariant& rhs );bool qgsVariantGreaterThan( const QVariant& lhs, const QVariant& rhs );QString qgsVsiPrefix( QString path );/** Allocates size bytes and returns a pointer to the allocated  memory.    Works like C malloc() but prints debug message by QgsLogger if allocation fails.    @param size size in bytes */void CORE_EXPORT *qgsMalloc( size_t size );/** Allocates  memory for an array of nmemb elements of size bytes each and returns    a pointer to the allocated memory. Works like C calloc() but prints debug message    by QgsLogger if allocation fails.    @param nmemb number of elements    @param size size of element in bytes */void CORE_EXPORT *qgsCalloc( size_t nmemb, size_t size );/** Frees the memory space  pointed  to  by  ptr. Works like C free().    @param ptr pointer to memory space */void CORE_EXPORT qgsFree( void *ptr );/** Wkt string that represents a geographic coord sys * @note added in 1.8 to replace GEOWkt */extern CORE_EXPORT const QString GEOWKT;extern CORE_EXPORT const QString PROJECT_SCALES;/** PROJ4 string that represents a geographic coord sys */extern CORE_EXPORT const QString GEOPROJ4;/** Magic number for a geographic coord sys in POSTGIS SRID */const long GEOSRID = 4326;/** Magic number for a geographic coord sys in QGIS srs.db tbl_srs.srs_id */const long GEOCRS_ID = 3452;/** Magic number for a geographic coord sys in EpsgCrsId ID format */const long GEO_EPSG_CRS_ID = 4326;/** Geographic coord sys from EPSG authority */extern CORE_EXPORT const QString GEO_EPSG_CRS_AUTHID;/** The length of the string "+proj=" */const int PROJ_PREFIX_LEN = 6;/** The length of the string "+ellps=" */const int ELLPS_PREFIX_LEN = 7;/** The length of the string "+lat_1=" */const int LAT_PREFIX_LEN = 7;/** Magick number that determines whether a projection crsid is a system (srs.db) *  or user (~/.qgis.qgis.db) defined projection. */const int USER_CRS_START_ID = 100000;//! Constant that holds the string representation for "No ellips/No CRS"// Added in version 2.0extern CORE_EXPORT const QString GEO_NONE;//// Constants for point symbols///** Magic number that determines the minimum allowable point size for point symbols */const double MINIMUM_POINT_SIZE = 0.1;/** Magic number that determines the default point size for point symbols */const double DEFAULT_POINT_SIZE = 2.0;const double DEFAULT_LINE_WIDTH = 0.26;/** default snapping tolerance for segments (@note added in 1.8) */const double DEFAULT_SEGMENT_EPSILON = 1e-8;typedef QMap<QString, QString> QgsStringMap;/** qgssize is used instead of size_t, because size_t is stdlib type, unknown *  by SIP, and it would be hard to define size_t correctly in SIP. *  Currently used "unsigned long long" was introduced in C++11 (2011) *  but it was supported already before C++11 on common platforms. *  "unsigned long long int" gives syntax error in SIP. *  KEEP IN SYNC WITH qgssize defined in SIP! */typedef unsigned long long qgssize;#if (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)) || defined(__clang__)#define Q_NOWARN_DEPRECATED_PUSH \  _Pragma("GCC diagnostic push") \  _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"")#define Q_NOWARN_DEPRECATED_POP \  _Pragma("GCC diagnostic pop")#elif defined(_MSC_VER)#define Q_NOWARN_DEPRECATED_PUSH \  __pragma(warning(push)) \  __pragma(warning(disable:4996))#define Q_NOWARN_DEPRECATED_POP \  __pragma(warning(pop))#else#define Q_NOWARN_DEPRECATED_PUSH#define Q_NOWARN_DEPRECATED_POP#endif// FIXME: also in qgisinterface.h#ifndef QGISEXTERN#ifdef WIN32#  define QGISEXTERN extern "C" __declspec( dllexport )#  ifdef _MSC_VER// do not warn about C bindings returing QString#    pragma warning(disable:4190)#  endif#else#  define QGISEXTERN extern "C"#endif#endif#endif