include/basegfx/tools/rectcliptools.hxx

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  19
  20 #ifndef INCLUDED_BASEGFX_TOOLS_RECTCLIPTOOLS_HXX
  21 #define INCLUDED_BASEGFX_TOOLS_RECTCLIPTOOLS_HXX
  22
  23 #include <sal/types.h>
  24 #include <basegfx/range/b2ibox.hxx>
  25
  26
  27
  28 namespace basegfx
  29 {
  30     namespace tools
  31     {
  32         namespace RectClipFlags
  33         {
  34             static const sal_uInt32 LEFT   = (sal_Int32)0x01;
  35             static const sal_uInt32 RIGHT  = (sal_Int32)0x02;
  36             static const sal_uInt32 TOP    = (sal_Int32)0x04;
  37             static const sal_uInt32 BOTTOM = (sal_Int32)0x08;
  38         }
  39
  40         /** Calc clip mask for Cohen-Sutherland rectangle clip
  41
  42             This function returns a clip mask used for the
  43             Cohen-Sutherland rectangle clip method, where one or more
  44             of the lower four bits are set, if the given point is
  45             outside one or more of the four half planes defining the
  46             rectangle (see RectClipFlags for possible values)
  47          */
  48         template< class Point, class Rect > inline
  49            sal_uInt32 getCohenSutherlandClipFlags( const Point& rP,
  50                                                    const Rect&  rR )
  51         {
  52             // maxY | minY | maxX | minX
  53             sal_uInt32 clip  = (rP.getX() < rR.getMinX()) << 0;
  54                        clip |= (rP.getX() > rR.getMaxX()) << 1;
  55                        clip |= (rP.getY() < rR.getMinY()) << 2;
  56                        clip |= (rP.getY() > rR.getMaxY()) << 3;
  57             return clip;
  58         }
  59
  60         /// Cohen-Sutherland mask calculation - overload for boxes.
  61         template< class Point > inline
  62            sal_uInt32 getCohenSutherlandClipFlags( const Point&  rP,
  63                                                    const B2IBox& rB )
  64         {
  65             // maxY | minY | maxX | minX
  66             sal_uInt32 clip  = (rP.getX() <  rB.getMinX()) << 0;
  67                        clip |= (rP.getX() >= rB.getMaxX()) << 1;
  68                        clip |= (rP.getY() <  rB.getMinY()) << 2;
  69                        clip |= (rP.getY() >= rB.getMaxY()) << 3;
  70             return clip;
  71         }
  72
  73         /** Determine number of clip planes hit by given clip mask
  74
  75             This method returns the number of one bits in the four
  76             least significant bits of the argument, which amounts to
  77             the number of clip planes hit within the
  78             getCohenSutherlandClipFlags() method.
  79          */
  80         inline sal_uInt32 getNumberOfClipPlanes( sal_uInt32 nFlags )
  81         {
  82             // classic bit count algo, see e.g. Reingold, Nievergelt,
  83             // Deo: Combinatorial Algorithms, Theory and Practice,
  84             // Prentice-Hall 1977
  85             nFlags = (nFlags & 0x05) + ((nFlags >> 1) & 0x05);
  86             nFlags = (nFlags & 0x03) + (nFlags >> 2); // no need for &
  87                                                       // 0x03, can't
  88                                                       // overflow
  89             return nFlags;
  90         }
  91     }
  92 }
  93
  94 #endif // INCLUDED_BASEGFX_TOOLS_RECTCLIPTOOLS_HXX
  95
  96 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */