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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* LineSnapper class.
*
* Authors:
* Diederik van Lierop <mail@diedenrezi.nl>
* And others...
*
* Copyright (C) 1999-2012 Authors
*
* Released under GNU GPL v2+, read the file 'COPYING' for more information.
*/
#include <2geom/line.h>
#include "line-snapper.h"
#include "snap.h"
Inkscape::LineSnapper::LineSnapper(SnapManager *sm, Geom::Coord const d) : Snapper(sm, d)
{
}
void Inkscape::LineSnapper::freeSnap(IntermSnapResults &isr,
Inkscape::SnapCandidatePoint const &p,
Geom::OptRect const &/*bbox_to_snap*/,
std::vector<SPObject const *> const */*it*/,
std::vector<Inkscape::SnapCandidatePoint> */*unselected_nodes*/) const
{
if (!(_snap_enabled && _snapmanager->snapprefs.isSourceSnappable(p.getSourceType())) ) {
return;
}
/* Get the lines that we will try to snap to */
const LineList lines = _getSnapLines(p.getPoint());
for (const auto & line : lines) {
Geom::Point const p1 = line.second; // point at guide/grid line
Geom::Point const p2 = p1 + Geom::rot90(line.first); // 2nd point at guide/grid line
assert(line.first != Geom::Point(0,0)); // we cannot project on an linesegment of zero length
Geom::Point const p_proj = Geom::projection(p.getPoint(), Geom::Line(p1, p2));
Geom::Coord const dist = Geom::L2(p_proj - p.getPoint());
//Store any line that's within snapping range
if (dist < getSnapperTolerance()) {
_addSnappedLine(isr, p_proj, dist, p.getSourceType(), p.getSourceNum(), line.first, line.second);
// For any line that's within range, we will also look at it's "point on line" p1. For guides
// this point coincides with its origin; for grids this is of no use, but we cannot
// discern between grids and guides here
Geom::Coord const dist_p1 = Geom::L2(p1 - p.getPoint());
if (dist_p1 < getSnapperTolerance()) {
_addSnappedLinesOrigin(isr, p1, dist_p1, p.getSourceType(), p.getSourceNum(), false);
// Only relevant for guides; grids don't have an origin per line
// Therefore _addSnappedLinesOrigin() will only be implemented for guides
}
// Here we will try to snap either tangentially or perpendicularly to a grid/guide line
// For this we need to know where the origin is located of the line that is currently being rotated,
std::vector<std::pair<Geom::Point, bool> > const origins_and_vectors = p.getOriginsAndVectors();
// Now we will iterate over all the origins and vectors and see which of these will get use a tangential or perpendicular snap
for (const auto & origins_and_vector : origins_and_vectors) {
if (origins_and_vector.second) { // if "second" is true then "first" is a vector, otherwise it's a point
// When snapping a line with a constant vector (constant direction) to a guide or grid line,
// then either all points will be perpendicular/tangential or none at all. This is not very useful
continue;
}
//Geom::Point origin_doc = _snapmanager->getDesktop()->dt2doc((*it_origin_or_vector).first); // "first" contains a Geom::Point, denoting either a point
Geom::Point origin = origins_and_vector.first; // "first" contains a Geom::Point, denoting either a point
// We won't try to snap tangentially; a line being tangential to another line can be achieved by snapping both its endpoints
// individually to the other line. There's no need to have an explicit tangential snap here, that would be redundant
if (_snapmanager->snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_PATH_PERPENDICULAR)) { // Find the point that leads to a perpendicular snap
Geom::Point const origin_proj = Geom::projection(origin, Geom::Line(p1, p2));
Geom::Coord dist = Geom::L2(origin_proj - p.getPoint());
if (dist < getSnapperTolerance()) {
_addSnappedLinePerpendicularly(isr, origin_proj, dist, p.getSourceType(), p.getSourceNum(), false);
}
}
}
}
}
}
void Inkscape::LineSnapper::constrainedSnap(IntermSnapResults &isr,
Inkscape::SnapCandidatePoint const &p,
Geom::OptRect const &/*bbox_to_snap*/,
SnapConstraint const &c,
std::vector<SPObject 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 (const auto & line : lines) {
Geom::Point const point_on_line = c.hasPoint() ? c.getPoint() : pp;
Geom::Line gridguide_line(line.second, line.second + Geom::rot90(line.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);
}
}
}
}
}
// Will only be overridden in the guide-snapper class, because grid lines don't have an origin; the
// grid-snapper classes will use this default empty method
void Inkscape::LineSnapper::_addSnappedLinesOrigin(IntermSnapResults &/*isr*/, Geom::Point const &/*origin*/, Geom::Coord const &/*snapped_distance*/, SnapSourceType const &/*source_type*/, long /*source_num*/, bool /*constrained_snap*/) const
{
}
/*
Local Variables:
mode:c++
c-file-style:"stroustrup"
c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
indent-tabs-mode:nil
fill-column:99
End:
*/
// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :
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