void Inkscape::LineSnapper::constrainedSnap(IntermSnapResults &isr,
Inkscape::SnapCandidatePoint const &p,
Geom::OptRect const &/*bbox_to_snap*/,
SnapConstraint const &c,
std::vector<SPItem const *> const */*it*/,
std::vector<SnapCandidatePoint> */*unselected_nodes*/) const
{
if (_snap_enabled == false || _snapmanager->snapprefs.isSourceSnappable(p.getSourceType()) == false) {
return;
}
// project the mouse pointer onto the constraint. Only the projected point will be considered for snapping
Geom::Point pp = c.projection(p.getPoint());
/* Get the lines that we will try to snap to */
const LineList lines = _getSnapLines(pp);
for (LineList::const_iterator i = lines.begin(); i != lines.end(); ++i) {
Geom::Point const point_on_line = c.hasPoint() ? c.getPoint() : pp;
Geom::Line gridguide_line(i->second, i->second + Geom::rot90(i->first));
if (c.isCircular()) {
// Find the intersections between the line and the circular constraint
// First, project the origin of the circle onto the line
Geom::Point const origin = c.getPoint();
Geom::Point const p_proj = Geom::projection(origin, gridguide_line);
Geom::Coord dist = Geom::L2(p_proj - origin); // distance from circle origin to constraint line
Geom::Coord radius = c.getRadius();
if (dist == radius) {
// Only one point of intersection;
_addSnappedPoint(isr, p_proj, Geom::L2(pp - p_proj), p.getSourceType(), p.getSourceNum(), true);
} else if (dist < radius) {
// Two points of intersection, symmetrical with respect to the projected point
// Calculate half the length of the linesegment between the two points of intersection
Geom::Coord l = sqrt(radius*radius - dist*dist);
Geom::Coord d = Geom::L2(gridguide_line.versor()); // length of versor, needed to normalize the versor
if (d > 0) {
Geom::Point v = l*gridguide_line.versor()/d;
_addSnappedPoint(isr, p_proj + v, Geom::L2(p.getPoint() - (p_proj + v)), p.getSourceType(), p.getSourceNum(), true);
_addSnappedPoint(isr, p_proj - v, Geom::L2(p.getPoint() - (p_proj - v)), p.getSourceType(), p.getSourceNum(), true);
}
}
} else {
// Find the intersections between the line and the linear constraint
Geom::Line constraint_line(point_on_line, point_on_line + c.getDirection());
Geom::OptCrossing inters = Geom::OptCrossing(); // empty by default
try
{
inters = Geom::intersection(constraint_line, gridguide_line);
}
catch (Geom::InfiniteSolutions &e)
{
// We're probably dealing with parallel lines, so snapping doesn't make any sense here
continue; // jump to the next iterator in the for-loop
}
if (inters) {
Geom::Point t = constraint_line.pointAt((*inters).ta);
const Geom::Coord dist = Geom::L2(t - p.getPoint());
if (dist < getSnapperTolerance()) {
// When doing a constrained snap, we're already at an intersection.
// This snappoint is therefore fully constrained, so there's no need
// to look for additional intersections; just return the snapped point
// and forget about the line
_addSnappedPoint(isr, t, dist, p.getSourceType(), p.getSourceNum(), true);
}
}
}
}
}
void Inkscape::ObjectSnapper::_snapPathsConstrained(IntermSnapResults &isr,
SnapCandidatePoint const &p,
SnapConstraint const &c,
Geom::Point const &p_proj_on_constraint) const
{
_collectPaths(p_proj_on_constraint, p.getSourceType(), p.getSourceNum() <= 0);
// Now we can finally do the real snapping, using the paths collected above
SPDesktop const *dt = _snapmanager->getDesktop();
g_assert(dt != NULL);
Geom::Point direction_vector = c.getDirection();
if (!is_zero(direction_vector)) {
direction_vector = Geom::unit_vector(direction_vector);
}
// The intersection point of the constraint line with any path, must lie within two points on the
// SnapConstraint: p_min_on_cl and p_max_on_cl. The distance between those points is twice the snapping tolerance
Geom::Point const p_min_on_cl = dt->dt2doc(p_proj_on_constraint - getSnapperTolerance() * direction_vector);
Geom::Point const p_max_on_cl = dt->dt2doc(p_proj_on_constraint + getSnapperTolerance() * direction_vector);
Geom::Coord tolerance = getSnapperTolerance();
// PS: Because the paths we're about to snap to are all expressed relative to document coordinate system, we will have
// to convert the snapper coordinates from the desktop coordinates to document coordinates
std::vector<Geom::Path> constraint_path;
if (c.isCircular()) {
Geom::Circle constraint_circle(dt->dt2doc(c.getPoint()), c.getRadius());
constraint_circle.getPath(constraint_path);
} else {
Geom::Path constraint_line;
constraint_line.start(p_min_on_cl);
constraint_line.appendNew<Geom::LineSegment>(p_max_on_cl);
constraint_path.push_back(constraint_line);
}
// Length of constraint_path will always be one
bool strict_snapping = _snapmanager->snapprefs.getStrictSnapping();
// Find all intersections of the constrained path with the snap target candidates
std::vector<Geom::Point> intersections;
for (std::vector<SnapCandidatePath >::const_iterator k = _paths_to_snap_to->begin(); k != _paths_to_snap_to->end(); ++k) {
if (k->path_vector && _allowSourceToSnapToTarget(p.getSourceType(), (*k).target_type, strict_snapping)) {
// Do the intersection math
Geom::CrossingSet cs = Geom::crossings(constraint_path, *(k->path_vector));
// Store the results as intersection points
unsigned int index = 0;
for (Geom::CrossingSet::const_iterator i = cs.begin(); i != cs.end(); ++i) {
if (index >= constraint_path.size()) {
break;
}
// Reconstruct and store the points of intersection
for (Geom::Crossings::const_iterator m = (*i).begin(); m != (*i).end(); ++m) {
intersections.push_back(constraint_path[index].pointAt((*m).ta));
}
index++;
}
//Geom::crossings will not consider the closing segment apparently, so we'll handle that separately here
//TODO: This should have been fixed in rev. #9859, which makes this workaround obsolete
for(Geom::PathVector::iterator it_pv = k->path_vector->begin(); it_pv != k->path_vector->end(); ++it_pv) {
if (it_pv->closed()) {
// Get the closing linesegment and convert it to a path
Geom::Path cls;
cls.close(false);
cls.append(it_pv->back_closed());
// Intersect that closing path with the constrained path
Geom::Crossings cs = Geom::crossings(constraint_path.front(), cls);
// Reconstruct and store the points of intersection
index = 0; // assuming the constraint path vector has only one path
for (Geom::Crossings::const_iterator m = cs.begin(); m != cs.end(); ++m) {
intersections.push_back(constraint_path[index].pointAt((*m).ta));
}
}
}
// Convert the collected points of intersection to snapped points
for (std::vector<Geom::Point>::iterator p_inters = intersections.begin(); p_inters != intersections.end(); ++p_inters) {
// Convert to desktop coordinates
(*p_inters) = dt->doc2dt(*p_inters);
// Construct a snapped point
Geom::Coord dist = Geom::L2(p.getPoint() - *p_inters);
SnappedPoint s = SnappedPoint(*p_inters, p.getSourceType(), p.getSourceNum(), k->target_type, dist, getSnapperTolerance(), getSnapperAlwaysSnap(), true, k->target_bbox);;
// Store the snapped point
if (dist <= tolerance) { // If the intersection is within snapping range, then we might snap to it
isr.points.push_back(s);
}
}
}
}
}