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Diffstat (limited to 'src/line-snapper.cpp')
| -rw-r--r-- | src/line-snapper.cpp | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/src/line-snapper.cpp b/src/line-snapper.cpp new file mode 100644 index 0000000..6882132 --- /dev/null +++ b/src/line-snapper.cpp @@ -0,0 +1,172 @@ +// 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 : |