blender-archive/source/blender/bmesh/intern/bmesh_walkers_impl.c

/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * 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, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * Contributor(s): Joseph Eagar, Geoffrey Bantle, Levi Schooley.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/bmesh/intern/bmesh_walkers_impl.c
 *  \ingroup bmesh
 *
 * BMesh Walker Code.
 */

#include <string.h>

#include "BLI_utildefines.h"

#include "BKE_customdata.h"

#include "bmesh.h"
#include "intern/bmesh_walkers_private.h"

/* pop into stack memory (common operation) */
#define BMW_state_remove_r(walker, owalk) { \
	memcpy(owalk, BMW_current_state(walker), sizeof(*(owalk))); \
	BMW_state_remove(walker); \
} (void)0

/** \name Mask Flag Checks
 * \{ */

static bool bmw_mask_check_vert(BMWalker *walker, BMVert *v)
{
	if ((walker->flag & BMW_FLAG_TEST_HIDDEN) && BM_elem_flag_test(v, BM_ELEM_HIDDEN)) {
		return false;
	}
	else if (walker->mask_vert && !BMO_elem_flag_test(walker->bm, v, walker->mask_vert)) {
		return false;
	}
	else {
		return true;
	}
}

static bool bmw_mask_check_edge(BMWalker *walker, BMEdge *e)
{
	if ((walker->flag & BMW_FLAG_TEST_HIDDEN) && BM_elem_flag_test(e, BM_ELEM_HIDDEN)) {
		return false;
	}
	else if (walker->mask_edge && !BMO_elem_flag_test(walker->bm, e, walker->mask_edge)) {
		return false;
	}
	else {
		return true;
	}
}

static bool bmw_mask_check_face(BMWalker *walker, BMFace *f)
{
	if ((walker->flag & BMW_FLAG_TEST_HIDDEN) && BM_elem_flag_test(f, BM_ELEM_HIDDEN)) {
		return false;
	}
	else if (walker->mask_face && !BMO_elem_flag_test(walker->bm, f, walker->mask_face)) {
		return false;
	}
	else {
		return true;
	}
}

/** \} */


/** \name BMesh Queries (modified to check walker flags)
 * \{ */

/**
 * Check for a wire edge, taking ignoring hidden.
 */
static bool bmw_edge_is_wire(const BMWalker *walker, const BMEdge *e)
{
	if (walker->flag & BMW_FLAG_TEST_HIDDEN) {
		/* check if this is a wire edge, ignoring hidden faces */
		if (BM_edge_is_wire(e)) {
			return true;
		}
		else {
			return BM_edge_is_all_face_flag_test(e, BM_ELEM_HIDDEN, false);
		}
	}
	else {
		return BM_edge_is_wire(e);
	}
}
/** \} */


/** \name Shell Walker
 * \{
 *
 * Starts at a vertex on the mesh and walks over the 'shell' it belongs
 * to via visiting connected edges.
 *
 * takes an edge or vertex as an argument, and spits out edges,
 * restrict flag acts on the edges as well.
 *
 * \todo Add restriction flag/callback for wire edges.
 */
static void bmw_VertShellWalker_visitEdge(BMWalker *walker, BMEdge *e)
{
	BMwShellWalker *shellWalk = NULL;

	if (BLI_gset_haskey(walker->visit_set, e)) {
		return;
	}

	if (!bmw_mask_check_edge(walker, e)) {
		return;
	}

	shellWalk = BMW_state_add(walker);
	shellWalk->curedge = e;
	BLI_gset_insert(walker->visit_set, e);
}

static void bmw_VertShellWalker_begin(BMWalker *walker, void *data)
{
	BMIter eiter;
	BMHeader *h = data;
	BMEdge *e;
	BMVert *v;

	if (UNLIKELY(h == NULL)) {
		return;
	}

	switch (h->htype) {
		case BM_VERT:
		{
			/* starting the walk at a vert, add all the edges
			 * to the worklist */
			v = (BMVert *)h;
			BM_ITER_ELEM (e, &eiter, v, BM_EDGES_OF_VERT) {
				bmw_VertShellWalker_visitEdge(walker, e);
			}
			break;
		}

		case BM_EDGE:
		{
			/* starting the walk at an edge, add the single edge
			 * to the worklist */
			e = (BMEdge *)h;
			bmw_VertShellWalker_visitEdge(walker, e);
			break;
		}
		default:
			BLI_assert(0);
	}
}

static void *bmw_VertShellWalker_yield(BMWalker *walker)
{
	BMwShellWalker *shellWalk = BMW_current_state(walker);
	return shellWalk->curedge;
}

static void *bmw_VertShellWalker_step(BMWalker *walker)
{
	BMwShellWalker *swalk, owalk;
	BMEdge *e, *e2;
	BMVert *v;
	BMIter iter;
	int i;

	BMW_state_remove_r(walker, &owalk);
	swalk = &owalk;

	e = swalk->curedge;

	for (i = 0; i < 2; i++) {
		v = i ? e->v2 : e->v1;
		BM_ITER_ELEM (e2, &iter, v, BM_EDGES_OF_VERT) {
			bmw_VertShellWalker_visitEdge(walker, e2);
		}
	}

	return e;
}

#if 0
static void *bmw_VertShellWalker_step(BMWalker *walker)
{
	BMEdge *curedge, *next = NULL;
	BMVert *v_old = NULL;
	bool restrictpass = true;
	BMwShellWalker shellWalk = *((BMwShellWalker *)BMW_current_state(walker));
	
	if (!BLI_gset_haskey(walker->visit_set, shellWalk.base)) {
		BLI_gset_insert(walker->visit_set, shellWalk.base);
	}

	BMW_state_remove(walker);


	/* find the next edge whose other vertex has not been visite */
	curedge = shellWalk.curedge;
	do {
		if (!BLI_gset_haskey(walker->visit_set, curedge)) {
			if (!walker->restrictflag ||
			    (walker->restrictflag && BMO_elem_flag_test(walker->bm, curedge, walker->restrictflag)))
			{
				BMwShellWalker *newstate;

				v_old = BM_edge_other_vert(curedge, shellWalk.base);
				
				/* push a new state onto the stac */
				newState = BMW_state_add(walker);
				BLI_gset_insert(walker->visit_set, curedge);
				
				/* populate the new stat */

				newState->base = v_old;
				newState->curedge = curedge;
			}
		}
	} while ((curedge = bmesh_disk_edge_next(curedge, shellWalk.base)) != shellWalk.curedge);
	
	return shellWalk.curedge;
}
#endif

/** \} */

/** \name LoopShell Walker
 * \{
 *
 * Starts at any element on the mesh and walks over the 'shell' it belongs
 * to via visiting connected loops.
 *
 * \note this is mainly useful to loop over a shell delimited by edges.
 */
static void bmw_LoopShellWalker_visitLoop(BMWalker *walker, BMLoop *l)
{
	BMwLoopShellWalker *shellWalk = NULL;

	if (BLI_gset_haskey(walker->visit_set, l)) {
		return;
	}

	if (!bmw_mask_check_face(walker, l->f)) {
		return;
	}

	shellWalk = BMW_state_add(walker);
	shellWalk->curloop = l;
	BLI_gset_insert(walker->visit_set, l);
}

static void bmw_LoopShellWalker_begin(BMWalker *walker, void *data)
{
	BMIter iter;
	BMHeader *h = data;

	if (UNLIKELY(h == NULL)) {
		return;
	}

	switch (h->htype) {
		case BM_LOOP:
		{
			/* starting the walk at a vert, add all the edges
			 * to the worklist */
			BMLoop *l = (BMLoop *)h;
			bmw_LoopShellWalker_visitLoop(walker, l);
			break;
		}

		case BM_VERT:
		{
			BMVert *v = (BMVert *)h;
			BMLoop *l;
			BM_ITER_ELEM (l, &iter, v, BM_LOOPS_OF_VERT) {
				bmw_LoopShellWalker_visitLoop(walker, l);
			}
			break;
		}
		case BM_EDGE:
		{
			BMEdge *e = (BMEdge *)h;
			BMLoop *l;
			BM_ITER_ELEM (l, &iter, e, BM_LOOPS_OF_EDGE) {
				bmw_LoopShellWalker_visitLoop(walker, l);
			}
			break;
		}
		case BM_FACE:
		{
			BMFace *f = (BMFace *)h;
			BMLoop *l = BM_FACE_FIRST_LOOP(f);
			/* walker will handle other loops within the face */
			bmw_LoopShellWalker_visitLoop(walker, l);
			break;
		}
		default:
			BLI_assert(0);
	}
}

static void *bmw_LoopShellWalker_yield(BMWalker *walker)
{
	BMwLoopShellWalker *shellWalk = BMW_current_state(walker);
	return shellWalk->curloop;
}

static void bmw_LoopShellWalker_step_impl(BMWalker *walker, BMLoop *l)
{
	BMEdge *e_edj_pair[2];
	int i;

	/* seems paranoid, but one caller also walks edges */
	BLI_assert(l->head.htype == BM_LOOP);

	bmw_LoopShellWalker_visitLoop(walker, l->next);
	bmw_LoopShellWalker_visitLoop(walker, l->prev);

	e_edj_pair[0] = l->e;
	e_edj_pair[1] = l->prev->e;

	for (i = 0; i < 2; i++) {
		BMEdge *e = e_edj_pair[i];
		if (bmw_mask_check_edge(walker, e)) {
			BMLoop *l_iter, *l_first;

			l_iter = l_first = e->l;
			do {
				BMLoop *l_radial = (l_iter->v == l->v) ? l_iter : l_iter->next;
				BLI_assert(l_radial->v == l->v);
				if (l != l_radial) {
					bmw_LoopShellWalker_visitLoop(walker, l_radial);
				}
			} while ((l_iter = l_iter->radial_next) != l_first);
		}
	}
}

static void *bmw_LoopShellWalker_step(BMWalker *walker)
{
	BMwLoopShellWalker *swalk, owalk;
	BMLoop *l;

	BMW_state_remove_r(walker, &owalk);
	swalk = &owalk;

	l = swalk->curloop;
	bmw_LoopShellWalker_step_impl(walker, l);

	return l;
}

/** \} */

/** \name LoopShell & 'Wire' Walker
 * \{
 *
 * Piggyback ontop of #BMwLoopShellWalker, but also walk over wire edges
 * This isn't elegant but users expect it when selecting linked,
 * so we can support delimiters _and_ walking over wire edges.
 *
 * Details:
 * - can yield edges (as well as loops)
 * - only step over wire edges.
 * - verts and edges are stored in `visit_set_alt`.
 */

static void bmw_LoopShellWalker_visitEdgeWire(BMWalker *walker, BMEdge *e)
{
	BMwLoopShellWireWalker *shellWalk = NULL;

	BLI_assert(bmw_edge_is_wire(walker, e));

	if (BLI_gset_haskey(walker->visit_set_alt, e)) {
		return;
	}

	if (!bmw_mask_check_edge(walker, e)) {
		return;
	}

	shellWalk = BMW_state_add(walker);
	shellWalk->curelem = (BMElem *)e;
	BLI_gset_insert(walker->visit_set_alt, e);
}

static void bmw_LoopShellWireWalker_visitVert(BMWalker *walker, BMVert *v, const BMEdge *e_from)
{
	BMEdge *e;

	BLI_assert(v->head.htype == BM_VERT);

	if (BLI_gset_haskey(walker->visit_set_alt, v)) {
		return;
	}

	if (!bmw_mask_check_vert(walker, v)) {
		return;
	}

	e = v->e;
	do {
		if (bmw_edge_is_wire(walker, e) && (e != e_from)) {
			BMVert *v_other;
			BMIter iter;
			BMLoop *l;

			bmw_LoopShellWalker_visitEdgeWire(walker, e);

			/* check if we step onto a non-wire vertex */
			v_other = BM_edge_other_vert(e, v);
			BM_ITER_ELEM (l, &iter, v_other, BM_LOOPS_OF_VERT) {

				bmw_LoopShellWalker_visitLoop(walker, l);
			}
		}
	} while ((e = BM_DISK_EDGE_NEXT(e, v)) != v->e);

	BLI_gset_insert(walker->visit_set_alt, v);
}

static void bmw_LoopShellWireWalker_begin(BMWalker *walker, void *data)
{
	BMHeader *h = data;

	if (UNLIKELY(h == NULL)) {
		return;
	}

	bmw_LoopShellWalker_begin(walker, data);

	switch (h->htype) {
		case BM_LOOP:
		{
			BMLoop *l = (BMLoop *)h;
			bmw_LoopShellWireWalker_visitVert(walker, l->v, NULL);
			break;
		}

		case BM_VERT:
		{
			BMVert *v = (BMVert *)h;
			if (v->e) {
				bmw_LoopShellWireWalker_visitVert(walker, v, NULL);
			}
			break;
		}
		case BM_EDGE:
		{
			BMEdge *e = (BMEdge *)h;
			if (bmw_mask_check_edge(walker, e)) {
				bmw_LoopShellWireWalker_visitVert(walker, e->v1, NULL);
				bmw_LoopShellWireWalker_visitVert(walker, e->v2, NULL);
			}
			else if (e->l) {
				BMLoop *l_iter, *l_first;

				l_iter = l_first = e->l;
				do {
					bmw_LoopShellWalker_visitLoop(walker, l_iter);
					bmw_LoopShellWalker_visitLoop(walker, l_iter->next);
				} while ((l_iter = l_iter->radial_next) != l_first);
			}
			break;
		}
		case BM_FACE:
		{
			/* wire verts will be walked over */
			break;
		}
		default:
			BLI_assert(0);
	}
}

static void *bmw_LoopShellWireWalker_yield(BMWalker *walker)
{
	BMwLoopShellWireWalker *shellWalk = BMW_current_state(walker);
	return shellWalk->curelem;
}

static void *bmw_LoopShellWireWalker_step(BMWalker *walker)
{
	BMwLoopShellWireWalker *swalk, owalk;

	BMW_state_remove_r(walker, &owalk);
	swalk = &owalk;

	if (swalk->curelem->head.htype == BM_LOOP) {
		BMLoop *l = (BMLoop *)swalk->curelem;

		bmw_LoopShellWalker_step_impl(walker, l);

		bmw_LoopShellWireWalker_visitVert(walker, l->v, NULL);

		return l;
	}
	else {
		BMEdge *e = (BMEdge *)swalk->curelem;

		BLI_assert(e->head.htype == BM_EDGE);

		bmw_LoopShellWireWalker_visitVert(walker, e->v1, e);
		bmw_LoopShellWireWalker_visitVert(walker, e->v2, e);

		return e;
	}
}

/** \} */


/** \name FaceShell Walker
 * \{
 *
 * Starts at an edge on the mesh and walks over the 'shell' it belongs
 * to via visiting connected faces.
 */
static void bmw_FaceShellWalker_visitEdge(BMWalker *walker, BMEdge *e)
{
	BMwShellWalker *shellWalk = NULL;

	if (BLI_gset_haskey(walker->visit_set, e)) {
		return;
	}

	if (!bmw_mask_check_edge(walker, e)) {
		return;
	}

	shellWalk = BMW_state_add(walker);
	shellWalk->curedge = e;
	BLI_gset_insert(walker->visit_set, e);
}

static void bmw_FaceShellWalker_begin(BMWalker *walker, void *data)
{
	BMEdge *e = data;
	bmw_FaceShellWalker_visitEdge(walker, e);
}

static void *bmw_FaceShellWalker_yield(BMWalker *walker)
{
	BMwShellWalker *shellWalk = BMW_current_state(walker);
	return shellWalk->curedge;
}

static void *bmw_FaceShellWalker_step(BMWalker *walker)
{
	BMwShellWalker *swalk, owalk;
	BMEdge *e, *e2;
	BMIter iter;

	BMW_state_remove_r(walker, &owalk);
	swalk = &owalk;

	e = swalk->curedge;

	if (e->l) {
		BMLoop *l_iter, *l_first;

		l_iter = l_first = e->l;
		do {
			BM_ITER_ELEM (e2, &iter, l_iter->f, BM_EDGES_OF_FACE) {
				if (e2 != e) {
					bmw_FaceShellWalker_visitEdge(walker, e2);
				}
			}
		} while ((l_iter = l_iter->radial_next) != l_first);
	}

	return e;
}
/** \} */


/** \name Connected Vertex Walker
 * \{
 *
 * Similar to shell walker, but visits vertices instead of edges.
 *
 * Walk from a vertex to all connected vertices.
 *
 */
static void bmw_ConnectedVertexWalker_visitVertex(BMWalker *walker, BMVert *v)
{
	BMwConnectedVertexWalker *vwalk;

	if (BLI_gset_haskey(walker->visit_set, v)) {
		/* already visited */
		return;
	}

	if (!bmw_mask_check_vert(walker, v)) {
		/* not flagged for walk */
		return;
	}

	vwalk = BMW_state_add(walker);
	vwalk->curvert = v;
	BLI_gset_insert(walker->visit_set, v);
}

static void bmw_ConnectedVertexWalker_begin(BMWalker *walker, void *data)
{
	BMVert *v = data;
	bmw_ConnectedVertexWalker_visitVertex(walker, v);
}

static void *bmw_ConnectedVertexWalker_yield(BMWalker *walker)
{
	BMwConnectedVertexWalker *vwalk = BMW_current_state(walker);
	return vwalk->curvert;
}

static void *bmw_ConnectedVertexWalker_step(BMWalker *walker)
{
	BMwConnectedVertexWalker *vwalk, owalk;
	BMVert *v, *v2;
	BMEdge *e;
	BMIter iter;

	BMW_state_remove_r(walker, &owalk);
	vwalk = &owalk;

	v = vwalk->curvert;

	BM_ITER_ELEM (e, &iter, v, BM_EDGES_OF_VERT) {
		v2 = BM_edge_other_vert(e, v);
		if (!BLI_gset_haskey(walker->visit_set, v2)) {
			bmw_ConnectedVertexWalker_visitVertex(walker, v2);
		}
	}

	return v;
}

/** \} */


/** \name Island Boundary Walker
 * \{
 *
 * Starts at a edge on the mesh and walks over the boundary of an island it belongs to.
 *
 * \note that this doesn't work on non-manifold geometry.
 * it might be better to rewrite this to extract
 * boundary info from the island walker, rather then directly walking
 * over the boundary.  raises an error if it encounters nonmanifold geometry.
 *
 * \todo Add restriction flag/callback for wire edges.
 */
static void bmw_IslandboundWalker_begin(BMWalker *walker, void *data)
{
	BMLoop *l = data;
	BMwIslandboundWalker *iwalk = NULL;

	iwalk = BMW_state_add(walker);

	iwalk->base = iwalk->curloop = l;
	iwalk->lastv = l->v;

	BLI_gset_insert(walker->visit_set, data);

}

static void *bmw_IslandboundWalker_yield(BMWalker *walker)
{
	BMwIslandboundWalker *iwalk = BMW_current_state(walker);

	return iwalk->curloop;
}

static void *bmw_IslandboundWalker_step(BMWalker *walker)
{
	BMwIslandboundWalker *iwalk, owalk;
	BMVert *v;
	BMEdge *e;
	BMFace *f;
	BMLoop *l;
	/* int found = 0; */

	memcpy(&owalk, BMW_current_state(walker), sizeof(owalk));
	/* normally we'd remove here, but delay until after error checking */
	iwalk = &owalk;

	l = iwalk->curloop;
	e = l->e;

	v = BM_edge_other_vert(e, iwalk->lastv);
	
	/* pop off current state */
	BMW_state_remove(walker);
	
	f = l->f;
	
	while (1) {
		l = BM_loop_other_edge_loop(l, v);
		if (BM_loop_is_manifold(l)) {
			l = l->radial_next;
			f = l->f;
			e = l->e;

			if (!bmw_mask_check_face(walker, f)) {
				l = l->radial_next;
				break;
			}
		}
		else {
			/* treat non-manifold edges as boundaries */
			f = l->f;
			e = l->e;
			break;
		}
	}
	
	if (l == owalk.curloop) {
		return NULL;
	}
	else if (BLI_gset_haskey(walker->visit_set, l)) {
		return owalk.curloop;
	}

	BLI_gset_insert(walker->visit_set, l);
	iwalk = BMW_state_add(walker);
	iwalk->base = owalk.base;

	//if (!BMO_elem_flag_test(walker->bm, l->f, walker->restrictflag))
	//	iwalk->curloop = l->radial_next;
	iwalk->curloop = l; //else iwalk->curloop = l;
	iwalk->lastv = v;

	return owalk.curloop;
}


/** \name Island Walker
 * \{
 *
 * Starts at a tool flagged-face and walks over the face region
 *
 * \todo Add restriction flag/callback for wire edges.
 */
static void bmw_IslandWalker_begin(BMWalker *walker, void *data)
{
	BMwIslandWalker *iwalk = NULL;

	if (!bmw_mask_check_face(walker, data)) {
		return;
	}

	iwalk = BMW_state_add(walker);
	BLI_gset_insert(walker->visit_set, data);

	iwalk->cur = data;
}

static void *bmw_IslandWalker_yield(BMWalker *walker)
{
	BMwIslandWalker *iwalk = BMW_current_state(walker);

	return iwalk->cur;
}

static void *bmw_IslandWalker_step(BMWalker *walker)
{
	BMwIslandWalker *iwalk, owalk;
	BMLoop *l_iter, *l_first;
	
	BMW_state_remove_r(walker, &owalk);
	iwalk = &owalk;

	l_iter = l_first = BM_FACE_FIRST_LOOP(iwalk->cur);
	do {
		/* could skip loop here too, but don't add unless we need it */
		if (!bmw_mask_check_edge(walker, l_iter->e)) {
			continue;
		}

		BMLoop *l_radial_iter = l_iter;
		while ((l_radial_iter = l_radial_iter->radial_next) != l_iter) {
			BMFace *f = l_radial_iter->f;

			if (!bmw_mask_check_face(walker, f)) {
				continue;
			}

			/* saves checking BLI_gset_haskey below (manifold edges theres a 50% chance) */
			if (f == iwalk->cur) {
				continue;
			}

			if (BLI_gset_haskey(walker->visit_set, f)) {
				continue;
			}

			iwalk = BMW_state_add(walker);
			iwalk->cur = f;
			BLI_gset_insert(walker->visit_set, f);
			break;
		}
	} while ((l_iter = l_iter->next) != l_first);

	return owalk.cur;
}

/** \} */


/** \name Edge Loop Walker
 * \{
 *
 * Starts at a tool-flagged edge and walks over the edge loop
 *
 */

/* utility function to see if an edge is apart of an ngon boundary */
static bool bm_edge_is_single(BMEdge *e)
{
	return ((BM_edge_is_boundary(e)) &&
	        (e->l->f->len > 4) &&
	        (BM_edge_is_boundary(e->l->next->e) || BM_edge_is_boundary(e->l->prev->e)));
}

static void bmw_EdgeLoopWalker_begin(BMWalker *walker, void *data)
{
	BMwEdgeLoopWalker *lwalk = NULL, owalk, *owalk_pt;
	BMEdge *e = data;
	BMVert *v;
	const int vert_edge_count[2] = {
	    BM_vert_edge_count_nonwire(e->v1),
	    BM_vert_edge_count_nonwire(e->v2),
	};

	v = e->v1;

	lwalk = BMW_state_add(walker);
	BLI_gset_insert(walker->visit_set, e);

	lwalk->cur = lwalk->start = e;
	lwalk->lastv = lwalk->startv = v;
	lwalk->is_boundary = BM_edge_is_boundary(e);
	lwalk->is_single = (lwalk->is_boundary && bm_edge_is_single(e));

	/* could also check that vertex*/
	if ((lwalk->is_boundary == false) &&
	    (vert_edge_count[0] == 3 || vert_edge_count[1] == 3))
	{
		BMIter iter;
		BMFace *f_iter;
		BMFace *f_best = NULL;

		BM_ITER_ELEM (f_iter, &iter, e, BM_FACES_OF_EDGE) {
			if (f_best == NULL || f_best->len < f_iter->len) {
				f_best = f_iter;
			}
		}

		if (f_best) {
			/* only use hub selection for 5+ sides else this could
			 * conflict with normal edge loop selection. */
			lwalk->f_hub = f_best->len > 4 ? f_best : NULL;
		}
		else {
			/* edge doesn't have any faces connected to it */
			lwalk->f_hub = NULL;
		}
	}
	else {
		lwalk->f_hub = NULL;
	}

	/* rewind */
	while ((owalk_pt = BMW_current_state(walker))) {
		owalk = *((BMwEdgeLoopWalker *)owalk_pt);
		BMW_walk(walker);
	}

	lwalk = BMW_state_add(walker);
	*lwalk = owalk;

	lwalk->lastv = lwalk->startv = BM_edge_other_vert(owalk.cur, lwalk->lastv);

	BLI_gset_clear(walker->visit_set, NULL);
	BLI_gset_insert(walker->visit_set, owalk.cur);
}

static void *bmw_EdgeLoopWalker_yield(BMWalker *walker)
{
	BMwEdgeLoopWalker *lwalk = BMW_current_state(walker);

	return lwalk->cur;
}

static void *bmw_EdgeLoopWalker_step(BMWalker *walker)
{
	BMwEdgeLoopWalker *lwalk, owalk;
	BMEdge *e, *nexte = NULL;
	BMLoop *l;
	BMVert *v;

	BMW_state_remove_r(walker, &owalk);
	lwalk = &owalk;

	e = lwalk->cur;
	l = e->l;

	if (owalk.f_hub) { /* NGON EDGE */
		int vert_edge_tot;

		v = BM_edge_other_vert(e, lwalk->lastv);

		vert_edge_tot = BM_vert_edge_count_nonwire(v);

		if (vert_edge_tot == 3) {
			l = BM_face_other_vert_loop(owalk.f_hub, lwalk->lastv, v);
			nexte = BM_edge_exists(v, l->v);

			if (bmw_mask_check_edge(walker, nexte) &&
			    !BLI_gset_haskey(walker->visit_set, nexte) &&
			    /* never step onto a boundary edge, this gives odd-results */
			    (BM_edge_is_boundary(nexte) == false))
			{
				lwalk = BMW_state_add(walker);
				lwalk->cur = nexte;
				lwalk->lastv = v;

				lwalk->is_boundary = owalk.is_boundary;
				lwalk->is_single = owalk.is_single;
				lwalk->f_hub = owalk.f_hub;

				BLI_gset_insert(walker->visit_set, nexte);
			}
		}
	}
	else if (l == NULL) {  /* WIRE EDGE */
		BMIter eiter;

		/* match trunk: mark all connected wire edges */
		for (int i = 0; i < 2; i++) {
			v = i ? e->v2 : e->v1;

			BM_ITER_ELEM (nexte, &eiter, v, BM_EDGES_OF_VERT) {
				if ((nexte->l == NULL) &&
				    bmw_mask_check_edge(walker, nexte) &&
				    !BLI_gset_haskey(walker->visit_set, nexte))
				{
					lwalk = BMW_state_add(walker);
					lwalk->cur = nexte;
					lwalk->lastv = v;

					lwalk->is_boundary = owalk.is_boundary;
					lwalk->is_single = owalk.is_single;
					lwalk->f_hub = owalk.f_hub;

					BLI_gset_insert(walker->visit_set, nexte);
				}
			}
		}
	}
	else if (owalk.is_boundary == false) {  /* NORMAL EDGE WITH FACES */
		int vert_edge_tot;

		v = BM_edge_other_vert(e, lwalk->lastv);

		vert_edge_tot = BM_vert_edge_count_nonwire(v);

		/* typical loopiong over edges in the middle of a mesh */
		/* however, why use 2 here at all? I guess for internal ngon loops it can be useful. Antony R. */
		if (vert_edge_tot == 4 || vert_edge_tot == 2) {
			int i_opposite = vert_edge_tot / 2;
			int i = 0;
			do {
				l = BM_loop_other_edge_loop(l, v);
				if (BM_edge_is_manifold(l->e)) {
					l = l->radial_next;
				}
				else {
					l = NULL;
					break;
				}
			} while ((++i != i_opposite));
		}
		else {
			l = NULL;
		}

		if (l != NULL) {
			if (l != e->l &&
			    bmw_mask_check_edge(walker, l->e) &&
			    !BLI_gset_haskey(walker->visit_set, l->e))
			{
				lwalk = BMW_state_add(walker);
				lwalk->cur = l->e;
				lwalk->lastv = v;

				lwalk->is_boundary = owalk.is_boundary;
				lwalk->is_single = owalk.is_single;
				lwalk->f_hub = owalk.f_hub;

				BLI_gset_insert(walker->visit_set, l->e);
			}
		}
	}
	else if (owalk.is_boundary == true) {  /* BOUNDARY EDGE WITH FACES */
		int vert_edge_tot;

		v = BM_edge_other_vert(e, lwalk->lastv);

		vert_edge_tot = BM_vert_edge_count_nonwire(v);

		/* check if we should step, this is fairly involved */
		if (
		    /* walk over boundary of faces but stop at corners */
		    (owalk.is_single == false && vert_edge_tot > 2) ||

		    /* initial edge was a boundary, so is this edge and vertex is only apart of this face
		     * this lets us walk over the boundary of an ngon which is handy */
		    (owalk.is_single == true && vert_edge_tot == 2 && BM_edge_is_boundary(e)))
		{
			/* find next boundary edge in the fan */
			do {
				l = BM_loop_other_edge_loop(l, v);
				if (BM_edge_is_manifold(l->e)) {
					l = l->radial_next;
				}
				else if (BM_edge_is_boundary(l->e)) {
					break;
				}
				else {
					l = NULL;
					break;
				}
			} while (true);
		}

		if (owalk.is_single == false && l && bm_edge_is_single(l->e)) {
			l = NULL;
		}

		if (l != NULL) {
			if (l != e->l &&
			    bmw_mask_check_edge(walker, l->e) &&
			    !BLI_gset_haskey(walker->visit_set, l->e))
			{
				lwalk = BMW_state_add(walker);
				lwalk->cur = l->e;
				lwalk->lastv = v;

				lwalk->is_boundary = owalk.is_boundary;
				lwalk->is_single = owalk.is_single;
				lwalk->f_hub = owalk.f_hub;

				BLI_gset_insert(walker->visit_set, l->e);
			}
		}
	}

	return owalk.cur;
}

/** \} */


/** \name Face Loop Walker
 * \{
 *
 * Starts at a tool-flagged face and walks over the face loop
 * Conditions for starting and stepping the face loop have been
 * tuned in an attempt to match the face loops built by EditMesh
 */

/* Check whether the face loop should includes the face specified
 * by the given BMLoop */
static bool bmw_FaceLoopWalker_include_face(BMWalker *walker, BMLoop *l)
{
	/* face must have degree 4 */
	if (l->f->len != 4) {
		return false;
	}

	if (!bmw_mask_check_face(walker, l->f)) {
		return false;
	}

	/* the face must not have been already visited */
	if (BLI_gset_haskey(walker->visit_set, l->f) && BLI_gset_haskey(walker->visit_set_alt, l->e)) {
		return false;
	}

	return true;
}

/* Check whether the face loop can start from the given edge */
static bool bmw_FaceLoopWalker_edge_begins_loop(BMWalker *walker, BMEdge *e)
{
	/* There is no face loop starting from a wire edge */
	if (BM_edge_is_wire(e)) {
		return false;
	}
	
	/* Don't start a loop from a boundary edge if it cannot
	 * be extended to cover any faces */
	if (BM_edge_is_boundary(e)) {
		if (!bmw_FaceLoopWalker_include_face(walker, e->l)) {
			return false;
		}
	}
	
	/* Don't start a face loop from non-manifold edges */
	if (!BM_edge_is_manifold(e)) {
		return false;
	}

	return true;
}

static void bmw_FaceLoopWalker_begin(BMWalker *walker, void *data)
{
	BMwFaceLoopWalker *lwalk, owalk, *owalk_pt;
	BMEdge *e = data;
	/* BMesh *bm = walker->bm; */ /* UNUSED */
	/* int fcount = BM_edge_face_count(e); */ /* UNUSED */

	if (!bmw_FaceLoopWalker_edge_begins_loop(walker, e))
		return;

	lwalk = BMW_state_add(walker);
	lwalk->l = e->l;
	lwalk->no_calc = false;
	BLI_gset_insert(walker->visit_set, lwalk->l->f);

	/* rewind */
	while ((owalk_pt = BMW_current_state(walker))) {
		owalk = *((BMwFaceLoopWalker *)owalk_pt);
		BMW_walk(walker);
	}

	lwalk = BMW_state_add(walker);
	*lwalk = owalk;
	lwalk->no_calc = false;

	BLI_gset_clear(walker->visit_set_alt, NULL);
	BLI_gset_insert(walker->visit_set_alt, lwalk->l->e);

	BLI_gset_clear(walker->visit_set, NULL);
	BLI_gset_insert(walker->visit_set, lwalk->l->f);
}

static void *bmw_FaceLoopWalker_yield(BMWalker *walker)
{
	BMwFaceLoopWalker *lwalk = BMW_current_state(walker);
	
	if (!lwalk) {
		return NULL;
	}

	return lwalk->l->f;
}

static void *bmw_FaceLoopWalker_step(BMWalker *walker)
{
	BMwFaceLoopWalker *lwalk, owalk;
	BMFace *f;
	BMLoop *l;

	BMW_state_remove_r(walker, &owalk);
	lwalk = &owalk;

	f = lwalk->l->f;
	l = lwalk->l->radial_next;
	
	if (lwalk->no_calc) {
		return f;
	}

	if (!bmw_FaceLoopWalker_include_face(walker, l)) {
		l = lwalk->l;
		l = l->next->next;
		if (!BM_edge_is_manifold(l->e)) {
			l = l->prev->prev;
		}
		l = l->radial_next;
	}

	if (bmw_FaceLoopWalker_include_face(walker, l)) {
		lwalk = BMW_state_add(walker);
		lwalk->l = l;

		if (l->f->len != 4) {
			lwalk->no_calc = true;
			lwalk->l = owalk.l;
		}
		else {
			lwalk->no_calc = false;
		}

		/* both may already exist */
		BLI_gset_add(walker->visit_set_alt, l->e);
		BLI_gset_add(walker->visit_set, l->f);
	}

	return f;
}

/** \} */


// #define BMW_EDGERING_NGON

/** \name Edge Ring Walker
 * \{
 *
 * Starts at a tool-flagged edge and walks over the edge ring
 * Conditions for starting and stepping the edge ring have been
 * tuned to match behavior users expect (dating back to v2.4x).
 */
static void bmw_EdgeringWalker_begin(BMWalker *walker, void *data)
{
	BMwEdgeringWalker *lwalk, owalk, *owalk_pt;
	BMEdge *e = data;

	lwalk = BMW_state_add(walker);
	lwalk->l = e->l;

	if (!lwalk->l) {
		lwalk->wireedge = e;
		return;
	}
	else {
		lwalk->wireedge = NULL;
	}

	BLI_gset_insert(walker->visit_set, lwalk->l->e);

	/* rewind */
	while ((owalk_pt = BMW_current_state(walker))) {
		owalk = *((BMwEdgeringWalker *)owalk_pt);
		BMW_walk(walker);
	}

	lwalk = BMW_state_add(walker);
	*lwalk = owalk;

#ifdef BMW_EDGERING_NGON
	if (lwalk->l->f->len % 2 != 0)
#else
	if (lwalk->l->f->len != 4)
#endif
	{
		lwalk->l = lwalk->l->radial_next;
	}

	BLI_gset_clear(walker->visit_set, NULL);
	BLI_gset_insert(walker->visit_set, lwalk->l->e);
}

static void *bmw_EdgeringWalker_yield(BMWalker *walker)
{
	BMwEdgeringWalker *lwalk = BMW_current_state(walker);
	
	if (!lwalk) {
		return NULL;
	}

	if (lwalk->l) {
		return lwalk->l->e;
	}
	else {
		return lwalk->wireedge;
	}
}

static void *bmw_EdgeringWalker_step(BMWalker *walker)
{
	BMwEdgeringWalker *lwalk, owalk;
	BMEdge *e;
	BMLoop *l;
#ifdef BMW_EDGERING_NGON
	int i, len;
#endif

#define EDGE_CHECK(e) (bmw_mask_check_edge(walker, e) && (BM_edge_is_boundary(e) || BM_edge_is_manifold(e)))

	BMW_state_remove_r(walker, &owalk);
	lwalk = &owalk;

	l = lwalk->l;
	if (!l)
		return lwalk->wireedge;

	e = l->e;
	if (!EDGE_CHECK(e)) {
		/* walker won't traverse to a non-manifold edge, but may
		 * be started on one, and should not traverse *away* from
		 * a non-manifold edge (non-manifold edges are never in an
		 * edge ring with manifold edges */
		return e;
	}

#ifdef BMW_EDGERING_NGON
	l = l->radial_next;

	i = len = l->f->len;
	while (i > 0) {
		l = l->next;
		i -= 2;
	}

	if ((len <= 0) || (len % 2 != 0) || !EDGE_CHECK(l->e) ||
	    !bmw_mask_check_face(walker, l->f))
	{
		l = owalk.l;
		i = len;
		while (i > 0) {
			l = l->next;
			i -= 2;
		}
	}
	/* only walk to manifold edge */
	if ((l->f->len % 2 == 0) && EDGE_CHECK(l->e) &&
	    !BLI_gset_haskey(walker->visit_set, l->e))

#else

	l = l->radial_next;
	l = l->next->next;
	
	if ((l->f->len != 4) || !EDGE_CHECK(l->e) || !bmw_mask_check_face(walker, l->f)) {
		l = owalk.l->next->next;
	}
	/* only walk to manifold edge */
	if ((l->f->len == 4) && EDGE_CHECK(l->e) &&
	    !BLI_gset_haskey(walker->visit_set, l->e))
#endif
	{
		lwalk = BMW_state_add(walker);
		lwalk->l = l;
		lwalk->wireedge = NULL;

		BLI_gset_insert(walker->visit_set, l->e);
	}

	return e;

#undef EDGE_CHECK
}

/** \} */


/** \name Boundary Edge Walker
 * \{ */

static void bmw_EdgeboundaryWalker_begin(BMWalker *walker, void *data)
{
	BMwEdgeboundaryWalker *lwalk;
	BMEdge *e = data;

	BLI_assert(BM_edge_is_boundary(e));

	if (BLI_gset_haskey(walker->visit_set, e))
		return;

	lwalk = BMW_state_add(walker);
	lwalk->e = e;
	BLI_gset_insert(walker->visit_set, e);
}

static void *bmw_EdgeboundaryWalker_yield(BMWalker *walker)
{
	BMwEdgeboundaryWalker *lwalk = BMW_current_state(walker);

	if (!lwalk) {
		return NULL;
	}

	return lwalk->e;
}

static void *bmw_EdgeboundaryWalker_step(BMWalker *walker)
{
	BMwEdgeboundaryWalker *lwalk, owalk;
	BMEdge *e, *e_other;
	BMVert *v;
	BMIter eiter;
	BMIter viter;

	BMW_state_remove_r(walker, &owalk);
	lwalk = &owalk;

	e = lwalk->e;

	if (!bmw_mask_check_edge(walker, e)) {
		return e;
	}

	BM_ITER_ELEM (v, &viter, e, BM_VERTS_OF_EDGE) {
		BM_ITER_ELEM (e_other, &eiter, v, BM_EDGES_OF_VERT) {
			if (e != e_other && BM_edge_is_boundary(e_other)) {
				if (BLI_gset_haskey(walker->visit_set, e_other)) {
					continue;
				}

				if (!bmw_mask_check_edge(walker, e_other)) {
					continue;
				}

				lwalk = BMW_state_add(walker);
				BLI_gset_insert(walker->visit_set, e_other);

				lwalk->e = e_other;
			}
		}
	}

	return e;
}

/** \} */


/** \name UV Edge Walker
 *
 * walk over uv islands; takes a loop as input.  restrict flag
 * restricts the walking to loops whose vert has restrict flag set as a
 * tool flag.
 *
 * the flag parameter to BMW_init maps to a loop customdata layer index.
 *
 * \{ */

static void bmw_UVEdgeWalker_begin(BMWalker *walker, void *data)
{
	BMwUVEdgeWalker *lwalk;
	BMLoop *l = data;

	if (BLI_gset_haskey(walker->visit_set, l))
		return;

	lwalk = BMW_state_add(walker);
	lwalk->l = l;
	BLI_gset_insert(walker->visit_set, l);
}

static void *bmw_UVEdgeWalker_yield(BMWalker *walker)
{
	BMwUVEdgeWalker *lwalk = BMW_current_state(walker);
	
	if (!lwalk) {
		return NULL;
	}

	return lwalk->l;
}

static void *bmw_UVEdgeWalker_step(BMWalker *walker)
{
	const int type = walker->bm->ldata.layers[walker->layer].type;
	const int offset = walker->bm->ldata.layers[walker->layer].offset;

	BMwUVEdgeWalker *lwalk, owalk;
	BMLoop *l;
	int i;

	BMW_state_remove_r(walker, &owalk);
	lwalk = &owalk;

	l = lwalk->l;

	if (!bmw_mask_check_edge(walker, l->e)) {
		return l;
	}

	/* go over loops around l->v and nl->v and see which ones share l and nl's
	 * mloopuv's coordinates. in addition, push on l->next if necessary */
	for (i = 0; i < 2; i++) {
		BMIter liter;
		BMLoop *l_pivot, *l_radial;

		l_pivot = i ? l->next : l;
		BM_ITER_ELEM (l_radial, &liter, l_pivot->v, BM_LOOPS_OF_VERT) {
			BMLoop *l_radial_first = l_radial;
			void *data_pivot = BM_ELEM_CD_GET_VOID_P(l_pivot, offset);

			do {
				BMLoop *l_other;
				void *data_other;

				if (BLI_gset_haskey(walker->visit_set, l_radial)) {
					continue;
				}

				if (l_radial->v != l_pivot->v) {
					if (!bmw_mask_check_edge(walker, l_radial->e)) {
						continue;
					}
				}

				l_other = (l_radial->v != l_pivot->v) ? l_radial->next : l_radial;
				data_other = BM_ELEM_CD_GET_VOID_P(l_other, offset);

				if (!CustomData_data_equals(type, data_pivot, data_other))
					continue;

				lwalk = BMW_state_add(walker);
				BLI_gset_insert(walker->visit_set, l_radial);

				lwalk->l = l_radial;

			} while ((l_radial = l_radial->radial_next) != l_radial_first);
		}
	}

	return l;
}

/** \} */


static BMWalker bmw_VertShellWalker_Type = {
	BM_VERT | BM_EDGE,
	bmw_VertShellWalker_begin,
	bmw_VertShellWalker_step,
	bmw_VertShellWalker_yield,
	sizeof(BMwShellWalker),
	BMW_BREADTH_FIRST,
	BM_EDGE, /* valid restrict masks */
};

static BMWalker bmw_LoopShellWalker_Type = {
	BM_FACE | BM_LOOP | BM_EDGE | BM_VERT,
	bmw_LoopShellWalker_begin,
	bmw_LoopShellWalker_step,
	bmw_LoopShellWalker_yield,
	sizeof(BMwLoopShellWalker),
	BMW_BREADTH_FIRST,
	BM_EDGE, /* valid restrict masks */
};

static BMWalker bmw_LoopShellWireWalker_Type = {
	BM_FACE | BM_LOOP | BM_EDGE | BM_VERT,
	bmw_LoopShellWireWalker_begin,
	bmw_LoopShellWireWalker_step,
	bmw_LoopShellWireWalker_yield,
	sizeof(BMwLoopShellWireWalker),
	BMW_BREADTH_FIRST,
	BM_EDGE, /* valid restrict masks */
};

static BMWalker bmw_FaceShellWalker_Type = {
	BM_EDGE,
	bmw_FaceShellWalker_begin,
	bmw_FaceShellWalker_step,
	bmw_FaceShellWalker_yield,
	sizeof(BMwShellWalker),
	BMW_BREADTH_FIRST,
	BM_EDGE, /* valid restrict masks */
};

static BMWalker bmw_IslandboundWalker_Type = {
	BM_LOOP,
	bmw_IslandboundWalker_begin,
	bmw_IslandboundWalker_step,
	bmw_IslandboundWalker_yield,
	sizeof(BMwIslandboundWalker),
	BMW_DEPTH_FIRST,
	BM_FACE, /* valid restrict masks */
};

static BMWalker bmw_IslandWalker_Type = {
	BM_FACE,
	bmw_IslandWalker_begin,
	bmw_IslandWalker_step,
	bmw_IslandWalker_yield,
	sizeof(BMwIslandWalker),
	BMW_BREADTH_FIRST,
	BM_EDGE | BM_FACE, /* valid restrict masks */
};

static BMWalker bmw_EdgeLoopWalker_Type = {
	BM_EDGE,
	bmw_EdgeLoopWalker_begin,
	bmw_EdgeLoopWalker_step,
	bmw_EdgeLoopWalker_yield,
	sizeof(BMwEdgeLoopWalker),
	BMW_DEPTH_FIRST,
	0, /* valid restrict masks */ /* could add flags here but so far none are used */
};

static BMWalker bmw_FaceLoopWalker_Type = {
	BM_EDGE,
	bmw_FaceLoopWalker_begin,
	bmw_FaceLoopWalker_step,
	bmw_FaceLoopWalker_yield,
	sizeof(BMwFaceLoopWalker),
	BMW_DEPTH_FIRST,
	0, /* valid restrict masks */ /* could add flags here but so far none are used */
};

static BMWalker bmw_EdgeringWalker_Type = {
	BM_EDGE,
	bmw_EdgeringWalker_begin,
	bmw_EdgeringWalker_step,
	bmw_EdgeringWalker_yield,
	sizeof(BMwEdgeringWalker),
	BMW_DEPTH_FIRST,
	BM_EDGE, /* valid restrict masks */
};

static BMWalker bmw_EdgeboundaryWalker_Type = {
	BM_EDGE,
	bmw_EdgeboundaryWalker_begin,
	bmw_EdgeboundaryWalker_step,
	bmw_EdgeboundaryWalker_yield,
	sizeof(BMwEdgeboundaryWalker),
	BMW_DEPTH_FIRST,
	0,
};

static BMWalker bmw_UVEdgeWalker_Type = {
	BM_LOOP,
	bmw_UVEdgeWalker_begin,
	bmw_UVEdgeWalker_step,
	bmw_UVEdgeWalker_yield,
	sizeof(BMwUVEdgeWalker),
	BMW_DEPTH_FIRST,
	BM_EDGE, /* valid restrict masks */
};

static BMWalker bmw_ConnectedVertexWalker_Type = {
	BM_VERT,
	bmw_ConnectedVertexWalker_begin,
	bmw_ConnectedVertexWalker_step,
	bmw_ConnectedVertexWalker_yield,
	sizeof(BMwConnectedVertexWalker),
	BMW_BREADTH_FIRST,
	BM_VERT, /* valid restrict masks */
};

BMWalker *bm_walker_types[] = {
	&bmw_VertShellWalker_Type,          /* BMW_VERT_SHELL */
	&bmw_LoopShellWalker_Type,          /* BMW_LOOP_SHELL */
	&bmw_LoopShellWireWalker_Type,      /* BMW_LOOP_SHELL_WIRE */
	&bmw_FaceShellWalker_Type,          /* BMW_FACE_SHELL */
	&bmw_EdgeLoopWalker_Type,           /* BMW_EDGELOOP */
	&bmw_FaceLoopWalker_Type,           /* BMW_FACELOOP */
	&bmw_EdgeringWalker_Type,           /* BMW_EDGERING */
	&bmw_EdgeboundaryWalker_Type,       /* BMW_EDGEBOUNDARY */
	&bmw_UVEdgeWalker_Type,             /* BMW_LOOPDATA_ISLAND */
	&bmw_IslandboundWalker_Type,        /* BMW_ISLANDBOUND */
	&bmw_IslandWalker_Type,             /* BMW_ISLAND */
	&bmw_ConnectedVertexWalker_Type,    /* BMW_CONNECTED_VERTEX */
};

const int bm_totwalkers = ARRAY_SIZE(bm_walker_types);