void Inkscape::ObjectSnapper::constrainedSnap( IntermSnapResults &isr,
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 || ThisSnapperMightSnap() == 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 a list of all the SPItems that we will try to snap to */
if (p.getSourceNum() <= 0) {
Geom::Rect const local_bbox_to_snap = bbox_to_snap ? *bbox_to_snap : Geom::Rect(pp, pp);
_findCandidates(_snapmanager->getDocument()->getRoot(), it, p.getSourceNum() <= 0, local_bbox_to_snap, false, Geom::identity());
}
// A constrained snap, is a snap in only one degree of freedom (specified by the constraint line).
// This is useful for example when scaling an object while maintaining a fixed aspect ratio. It's
// nodes are only allowed to move in one direction (i.e. in one degree of freedom).
_snapNodes(isr, p, unselected_nodes, c, pp);
if (_snapmanager->snapprefs.isTargetSnappable(SNAPTARGET_PATH, SNAPTARGET_PATH_INTERSECTION, SNAPTARGET_BBOX_EDGE, SNAPTARGET_PAGE_BORDER, SNAPTARGET_TEXT_BASELINE)) {
_snapPathsConstrained(isr, p, c, pp);
}
}
void Inkscape::ObjectSnapper::_snapNodes(IntermSnapResults &isr,
SnapCandidatePoint const &p,
std::vector<SnapCandidatePoint> *unselected_nodes,
SnapConstraint const &c,
Geom::Point const &p_proj_on_constraint) const
{
// Iterate through all nodes, find out which one is the closest to p, and snap to it!
_collectNodes(p.getSourceType(), p.getSourceNum() <= 0);
if (unselected_nodes != NULL && unselected_nodes->size() > 0) {
g_assert(_points_to_snap_to != NULL);
_points_to_snap_to->insert(_points_to_snap_to->end(), unselected_nodes->begin(), unselected_nodes->end());
}
SnappedPoint s;
bool success = false;
bool strict_snapping = _snapmanager->snapprefs.getStrictSnapping();
for (std::vector<SnapCandidatePoint>::const_iterator k = _points_to_snap_to->begin(); k != _points_to_snap_to->end(); ++k) {
if (_allowSourceToSnapToTarget(p.getSourceType(), (*k).getTargetType(), strict_snapping)) {
Geom::Point target_pt = (*k).getPoint();
Geom::Coord dist = Geom::infinity();
if (!c.isUndefined()) {
// We're snapping to nodes along a constraint only, so find out if this node
// is at the constraint, while allowing for a small margin
if (Geom::L2(target_pt - c.projection(target_pt)) > 1e-9) {
// The distance from the target point to its projection on the constraint
// is too large, so this point is not on the constraint. Skip it!
continue;
}
dist = Geom::L2(target_pt - p_proj_on_constraint);
} else {
// Free (unconstrained) snapping
dist = Geom::L2(target_pt - p.getPoint());
}
if (dist < getSnapperTolerance() && dist < s.getSnapDistance()) {
s = SnappedPoint(target_pt, p.getSourceType(), p.getSourceNum(), (*k).getTargetType(), dist, getSnapperTolerance(), getSnapperAlwaysSnap(), false, true, (*k).getTargetBBox());
success = true;
}
}
}
if (success) {
isr.points.push_back(s);
}
}
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);
}
}
}
}
}