AOO410/main/basegfx/inc/basegfx/polygon/b2dpolypolygoncutter.hxx

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#ifndef _BGFX_POLYGON_B2DPOLYPOLYGONCUTTER_HXX
#define _BGFX_POLYGON_B2DPOLYPOLYGONCUTTER_HXX

#include <basegfx/polygon/b2dpolypolygon.hxx>

//////////////////////////////////////////////////////////////////////////////

namespace basegfx
{
	namespace tools
	{
		// Solve all crossovers in a polyPolygon. This re-layouts all contained polygons so that the
		// result will contain only non-cutting polygons. For that reason, points will be added at
		// crossover and touch points and the single Polygons may be re-combined. The orientations
		// of the contained polygons in not changed but used as topological information.
		// Self crossovers of the contained sub-polygons are implicitely handled, but to not lose
		// the topological information, it may be necessary to remove self-intersections of the
		// contained sub-polygons in a preparing step and to explicitely correct their orientations.
		B2DPolyPolygon solveCrossovers(const B2DPolyPolygon& rCandidate);

		// Version for single polygons. This is for solving self-intersections. Result will be free of
		// crossovers. When result contains multiple polygons, it may be necessary to rearrange their
		// orientations since holes may have been created (use correctOrientations eventually).
		B2DPolyPolygon solveCrossovers(const B2DPolygon& rCandidate);

		// Neutral polygons will be stripped. Neutral polygons are ones who's orientation is
		// neutral, so normally they have no volume -> just closed paths. A polygon with the same
		// positive and negative oriented volume is also neutral, so this may not be wanted. It is
		// safe to call with crossover-free polygons, though (that's where it's mostly used).
		B2DPolyPolygon stripNeutralPolygons(const B2DPolyPolygon& rCandidate);

		// Remove not necessary polygons. Works only correct with crossover-free polygons. For each
		// polygon, the depth for the PolyPolygon is calculated. The orientation is used to identify holes.
		// Start value for holes is -1, for polygons it's zero. Ech time a polygon is contained in another one,
		// it's depth is increased when inside a polygon, decreased when inside a hole. The result is a depth
		// which e.g. is -1 for holes outside everything, 1 for a polygon covered by another polygon and zero
		// for e.g. holes in a polygon or polygons outside everythig else.
		// In the 2nd step, all polygons with depth other than zero are removed. If bKeepAboveZero is used, 
		// all polygons < 1 are removed. The bKeepAboveZero mode is useful for clipping, e.g. just append
		// one polygon to another and use this mode -> only parts where two polygons overlapped will be kept.
		// In combination with correct orientation of the input orientations and the SolveCrossover calls this
		// can be combined for logical polygon operations or polygon clipping.
		B2DPolyPolygon stripDispensablePolygons(const B2DPolyPolygon& rCandidate, bool bKeepAboveZero = false);

        // geometrically convert PolyPolygons which are proposed to use nonzero fill rule
        // to a representation where evenodd paint will give the same result. To do this
        // all intersections and self-intersections get solved (the polygons will be rearranged
        // if needed). Then all polygons which are inside another one with the same orientation
        // get deleted
        B2DPolyPolygon createNonzeroConform(const B2DPolyPolygon& rCandidate);

        // For convenience: The four basic operations OR, XOR, AND and DIFF for
        // two PolyPolygons. These are combinations of the above methods. To not be forced
        // to do evtl. already done preparations twice, You have to do the operations Yourself.
        //
        // A source preparation consists of preparing it to be seen as XOR-Rule PolyPolygon,
        // so it is freed of intersections, self-intersections and the orientations are corrected.
        // Important is that it will define the same areas as before, but is intersection-free.
        // As an example think about a single polygon looping in itself and having holes. To
        // topologically correctly handle this, it is necessary to remove all intersections and
        // to correct the orientations. The orientation of the isolated holes e.g. will be negative.
        // Topologically it is necessary to prepare each polygon which is seen as entity. It is
        // not sufficient just to concatenate them and prepare the result, this may be topologically
        // different since the simple concatenation will be seen as XOR. To work correctly, You
        // may need to OR those polygons.

        // Preparations: solve self-intersections and intersections, remove neutral
        // parts and correct orientations.
        B2DPolyPolygon prepareForPolygonOperation(const B2DPolygon& rCandidate);
        B2DPolyPolygon prepareForPolygonOperation(const B2DPolyPolygon& rCandidate);

        // OR: Return all areas where CandidateA or CandidateB exist
        B2DPolyPolygon solvePolygonOperationOr(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB);

        // XOR: Return all areas where CandidateA or CandidateB exist, but not both
        B2DPolyPolygon solvePolygonOperationXor(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB);

        // AND: Return all areas where CandidateA and CandidateB exist
        B2DPolyPolygon solvePolygonOperationAnd(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB);

        // DIFF: Return all areas where CandidateA is not covered by CandidateB (cut B out of A)
        B2DPolyPolygon solvePolygonOperationDiff(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB);

		/** merge all single PolyPolygons to a single, OR-ed PolyPolygon

			@param rInput
			The source PolyPolygons

			@return A single PolyPolygon containing the Or-merged result
		*/
		B2DPolyPolygon mergeToSinglePolyPolygon(const B2DPolyPolygonVector& rInput);

	} // end of namespace tools
} // end of namespace basegfx

//////////////////////////////////////////////////////////////////////////////


#endif /* _BGFX_POLYGON_B2DPOLYPOLYGONCUTTER_HXX */