Adding upstream version 1.2.2.upstream/1.2.2upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 999 insertions, 0 deletions

diff --git a/src/snap.cpp b/src/snap.cpp
new file mode 100644
index 0000000..cd1202d
--- /dev/null
+++ b/src/snap.cpp
@@ -0,0 +1,999 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * SnapManager class.
+ *
+ * Authors:
+ *   Lauris Kaplinski <lauris@kaplinski.com>
+ *   Frank Felfe <innerspace@iname.com>
+ *   Nathan Hurst <njh@njhurst.com>
+ *   Carl Hetherington <inkscape@carlh.net>
+ *   Diederik van Lierop <mail@diedenrezi.nl>
+ *
+ * Copyright (C) 2006-2007 Johan Engelen <johan@shouraizou.nl>
+ * Copyright (C) 2004      Nathan Hurst
+ * Copyright (C) 1999-2012 Authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include <glibmm/timer.h>
+
+#include <2geom/transforms.h>
+
+#include "snap.h"
+#include "snap-enums.h"
+#include "preferences.h"
+#include "object/sp-use.h"
+#include "object/sp-mask.h"
+#include "live_effects/effect-enum.h"
+#include "object/sp-filter.h"
+#include "object/sp-object.h"
+#include "object/sp-page.h"
+#include "object/sp-clippath.h"
+#include "object/sp-root.h"
+#include "style.h"
+
+#include "desktop.h"
+#include "inkscape.h"
+#include "pure-transform.h"
+
+#include "display/control/canvas-grid.h"
+#include "display/control/snap-indicator.h"
+
+#include "helper/mathfns.h"
+
+#include "object/sp-namedview.h"
+#include "object/sp-guide.h"
+
+#include "ui/tools/tool-base.h"
+
+using Inkscape::Util::round_to_upper_multiple_plus;
+using Inkscape::Util::round_to_lower_multiple_plus;
+
+SnapManager::SnapManager(SPNamedView const *v, Inkscape::SnapPreferences& preferences) :
+    snapprefs(preferences),
+    guide(this, 0),
+    object(this, 0),
+    alignment(this, 0),
+    distribution(this, 0),
+    _named_view(v),
+    _rotation_center_source_items(std::vector<SPItem*>()),
+    _desktop(nullptr),
+    _snapindicator(true),
+    _unselected_nodes(nullptr)
+{
+    _obj_snapper_candidates = std::make_unique<std::vector<Inkscape::SnapCandidateItem>>();
+    _align_snapper_candidates = std::make_unique<std::vector<Inkscape::SnapCandidateItem>>();
+}
+
+SnapManager::~SnapManager()
+{
+    _obj_snapper_candidates->clear();
+    _align_snapper_candidates->clear();
+}
+
+SnapManager::SnapperList SnapManager::getSnappers() const
+{
+    SnapManager::SnapperList s;
+    s.push_back(&guide);
+    s.push_back(&object);
+    s.push_back(&alignment);
+    s.push_back(&distribution);
+
+    SnapManager::SnapperList gs = getGridSnappers();
+    s.splice(s.begin(), gs);
+
+    return s;
+}
+
+SnapManager::SnapperList SnapManager::getGridSnappers() const
+{
+    SnapperList s;
+
+    if (_desktop && _desktop->gridsEnabled() && snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_GRID)) {
+        for(auto grid : _named_view->grids) {
+            s.push_back(grid->snapper);
+        }
+    }
+
+    return s;
+}
+
+bool SnapManager::someSnapperMightSnap(bool immediately) const
+{
+    if ( !snapprefs.getSnapEnabledGlobally() ) {
+        return false;
+    }
+
+    // If we're asking if some snapper might snap RIGHT NOW (without the snap being postponed)...
+    if ( immediately && snapprefs.getSnapPostponedGlobally() ) {
+        return false;
+    }
+
+    SnapperList const s = getSnappers();
+    SnapperList::const_iterator i = s.begin();
+    while (i != s.end() && (*i)->ThisSnapperMightSnap() == false) {
+        ++i;
+    }
+
+    return (i != s.end());
+}
+
+bool SnapManager::gridSnapperMightSnap() const
+{
+    if ( !snapprefs.getSnapEnabledGlobally() || snapprefs.getSnapPostponedGlobally() ) {
+        return false;
+    }
+
+    SnapperList const s = getGridSnappers();
+    SnapperList::const_iterator i = s.begin();
+    while (i != s.end() && (*i)->ThisSnapperMightSnap() == false) {
+        ++i;
+    }
+
+    return (i != s.end());
+}
+
+void SnapManager::freeSnapReturnByRef(Geom::Point &p,
+                                      Inkscape::SnapSourceType const source_type,
+                                      Geom::OptRect const &bbox_to_snap) const
+{
+    Inkscape::SnappedPoint const s = freeSnap(Inkscape::SnapCandidatePoint(p, source_type, Inkscape::SNAPTARGET_PATH), bbox_to_snap);
+    s.getPointIfSnapped(p);
+}
+
+Inkscape::SnappedPoint SnapManager::freeSnap(Inkscape::SnapCandidatePoint const &p,
+                                             Geom::OptRect const &bbox_to_snap,
+                                             bool to_paths_only) const
+{
+    if (!someSnapperMightSnap()) {
+        return Inkscape::SnappedPoint(p, Inkscape::SNAPTARGET_UNDEFINED, Geom::infinity(), 0, false, false, false);
+    }
+
+    IntermSnapResults isr;
+    SnapperList const snappers = getSnappers();
+
+    for (auto snapper : snappers) {
+        snapper->freeSnap(isr, p, bbox_to_snap, &_objects_to_ignore, _unselected_nodes);
+    }
+
+    return findBestSnap(p, isr, false, false, to_paths_only);
+}
+
+void SnapManager::preSnap(Inkscape::SnapCandidatePoint const &p, bool to_paths_only)
+{
+    // setup() must have been called before calling this method!
+
+    if (_snapindicator) {
+        _snapindicator = false; // prevent other methods from drawing a snap indicator; we want to control this here
+        Inkscape::SnappedPoint s = freeSnap(p, Geom::OptRect(), to_paths_only);
+        g_assert(_desktop != nullptr);
+        if (s.getSnapped()) {
+            _desktop->snapindicator->set_new_snaptarget(s, true);
+        } else {
+            _desktop->snapindicator->remove_snaptarget(true);
+        }
+        _snapindicator = true; // restore the original value
+    }
+}
+
+Geom::Point SnapManager::multipleOfGridPitch(Geom::Point const &t, Geom::Point const &origin)
+{
+    if (!snapprefs.getSnapEnabledGlobally() || snapprefs.getSnapPostponedGlobally())
+        return t;
+
+    if (_desktop && _desktop->gridsEnabled()) {
+        bool success = false;
+        Geom::Point nearest_multiple;
+        Geom::Coord nearest_distance = Geom::infinity();
+        Inkscape::SnappedPoint bestSnappedPoint(t);
+
+        // It will snap to the grid for which we find the closest snap. This might be a different
+        // grid than to which the objects were initially aligned. I don't see an easy way to fix
+        // this, so when using multiple grids one can get unexpected results
+
+        // Cannot use getGridSnappers() because we need both the grids AND their snappers
+        // Therefore we iterate through all grids manually
+        for (auto grid : _named_view->grids) {
+            const Inkscape::Snapper* snapper = grid->snapper;
+            if (snapper && snapper->ThisSnapperMightSnap()) {
+                // To find the nearest multiple of the grid pitch for a given translation t, we
+                // will use the grid snapper. Simply snapping the value t to the grid will do, but
+                // only if the origin of the grid is at (0,0). If it's not then compensate for this
+                // in the translation t
+                Geom::Point const t_offset = t + grid->origin;
+                IntermSnapResults isr;
+                // Only the first three parameters are being used for grid snappers
+                snapper->freeSnap(isr, Inkscape::SnapCandidatePoint(t_offset, Inkscape::SNAPSOURCE_GRID_PITCH),Geom::OptRect(), nullptr, nullptr);
+                // Find the best snap for this grid, including intersections of the grid-lines
+                bool old_val = _snapindicator;
+                _snapindicator = false;
+                Inkscape::SnappedPoint s = findBestSnap(Inkscape::SnapCandidatePoint(t_offset, Inkscape::SNAPSOURCE_GRID_PITCH), isr, false, true);
+                _snapindicator = old_val;
+                if (s.getSnapped() && (s.getSnapDistance() < nearest_distance)) {
+                    // use getSnapDistance() instead of getWeightedDistance() here because the pointer's position
+                    // doesn't tell us anything about which node to snap
+                    success = true;
+                    nearest_multiple = s.getPoint() - grid->origin;
+                    nearest_distance = s.getSnapDistance();
+                    bestSnappedPoint = s;
+                }
+            }
+        }
+
+        if (success) {
+            bestSnappedPoint.setPoint(origin + nearest_multiple);
+            _desktop->snapindicator->set_new_snaptarget(bestSnappedPoint);
+            return nearest_multiple;
+        }
+    }
+
+    return t;
+}
+
+void SnapManager::constrainedSnapReturnByRef(Geom::Point &p,
+                                             Inkscape::SnapSourceType const source_type,
+                                             Inkscape::Snapper::SnapConstraint const &constraint,
+                                             Geom::OptRect const &bbox_to_snap) const
+{
+    Inkscape::SnappedPoint const s = constrainedSnap(Inkscape::SnapCandidatePoint(p, source_type), constraint, bbox_to_snap);
+    p = s.getPoint(); // If we didn't snap, then we will return the point projected onto the constraint
+}
+
+Inkscape::SnappedPoint SnapManager::constrainedSnap(Inkscape::SnapCandidatePoint const &p,
+                                                    Inkscape::Snapper::SnapConstraint const &constraint,
+                                                    Geom::OptRect const &bbox_to_snap) const
+{
+    // First project the mouse pointer onto the constraint
+    Geom::Point pp = constraint.projection(p.getPoint());
+
+    Inkscape::SnappedPoint no_snap = Inkscape::SnappedPoint(pp, p.getSourceType(), p.getSourceNum(), Inkscape::SNAPTARGET_CONSTRAINT, Geom::infinity(), 0, false, true, false);
+
+    if (!someSnapperMightSnap()) {
+        // Always return point on constraint
+        return no_snap;
+    }
+
+    Inkscape::SnappedPoint result = no_snap;
+
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    if ((prefs->getBool("/options/snapmousepointer/value", false)) && p.isSingleHandle()) {
+        // Snapping the mouse pointer instead of the constrained position of the knot allows
+        // to snap to things which don't intersect with the constraint line; this is basically
+        // then just a freesnap with the constraint applied afterwards
+        // We'll only do this if we're dragging a single handle, and for example not when transforming an object in the selector tool
+        result = freeSnap(p, bbox_to_snap);
+        if (result.getSnapped()) {
+            // only change the snap indicator if we really snapped to something
+            if (_snapindicator && _desktop) {
+                _desktop->snapindicator->set_new_snaptarget(result);
+            }
+            // Apply the constraint
+            result.setPoint(constraint.projection(result.getPoint()));
+            return result;
+        }
+        return no_snap;
+    }
+
+    IntermSnapResults isr;
+    SnapperList const snappers = getSnappers();
+    for (auto snapper : snappers) {
+        snapper->constrainedSnap(isr, p, bbox_to_snap, constraint, &_objects_to_ignore, _unselected_nodes);
+    }
+
+    result = findBestSnap(p, isr, true);
+
+
+    if (result.getSnapped()) {
+        // only change the snap indicator if we really snapped to something
+        if (_snapindicator && _desktop) {
+            _desktop->snapindicator->set_new_snaptarget(result);
+        }
+        return result;
+    }
+    return no_snap;
+}
+
+/* See the documentation for constrainedSnap() directly above for more details.
+ * The difference is that multipleConstrainedSnaps() will take a list of constraints instead of a single one,
+ * and will try to snap the SnapCandidatePoint to only the closest constraint
+ *  \param p Source point to be snapped
+ *  \param constraints List of directions or lines along which snapping must occur
+ *  \param dont_snap If true then we will only apply the constraint, without snapping
+ *  \param bbox_to_snap Bounding box hulling the set of points, all from the same selection and having the same transformation
+ */
+
+
+Inkscape::SnappedPoint SnapManager::multipleConstrainedSnaps(Inkscape::SnapCandidatePoint const &p,
+                                                    std::vector<Inkscape::Snapper::SnapConstraint> const &constraints,
+                                                    bool dont_snap,
+                                                    Geom::OptRect const &bbox_to_snap) const
+{
+
+    Inkscape::SnappedPoint no_snap = Inkscape::SnappedPoint(p.getPoint(), p.getSourceType(), p.getSourceNum(), Inkscape::SNAPTARGET_CONSTRAINT, Geom::infinity(), 0, false, true, false);
+    if (constraints.size() == 0) {
+        return no_snap;
+    }
+
+    // We haven't tried to snap yet; we will first determine which constraint is closest to where we are now,
+    // i.e. lets find out which of the constraints yields the closest projection of point p
+
+    // Project the mouse pointer on each of the constraints
+    std::vector<Geom::Point> projections;
+    for (const auto & constraint : constraints) {
+        // Project the mouse pointer onto the constraint; In case we don't snap then we will
+        // return the projection onto the constraint, such that the constraint is always enforced
+        Geom::Point pp = constraint.projection(p.getPoint());
+        projections.push_back(pp);
+    }
+
+    // Select the closest constraint
+    no_snap.setPoint(projections.front());
+    Inkscape::Snapper::SnapConstraint cc = constraints.front(); //closest constraint
+
+    std::vector<Inkscape::Snapper::SnapConstraint>::const_iterator c = constraints.begin();
+    std::vector<Geom::Point>::iterator pp = projections.begin();
+    for (; pp != projections.end(); ++pp) {
+        if (Geom::L2(*pp - p.getPoint()) < Geom::L2(no_snap.getPoint() - p.getPoint())) {
+            no_snap.setPoint(*pp); // Remember the projection onto the closest constraint
+            cc = *c; // Remember the closest constraint itself
+        }
+        ++c;
+    }
+
+    if (!someSnapperMightSnap() || dont_snap) {
+        return no_snap;
+    }
+
+    IntermSnapResults isr;
+    SnapperList const snappers = getSnappers();
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    bool snap_mouse = prefs->getBool("/options/snapmousepointer/value", false);
+
+    Inkscape::SnappedPoint result = no_snap;
+    if (snap_mouse && p.isSingleHandle()) {
+        // Snapping the mouse pointer instead of the constrained position of the knot allows
+        // to snap to things which don't intersect with the constraint line; this is basically
+        // then just a freesnap with the constraint applied afterwards
+        // We'll only to this if we're dragging a single handle, and for example not when transforming an object in the selector tool
+        result = freeSnap(p, bbox_to_snap);
+        // Now apply the constraint afterwards
+        result.setPoint(cc.projection(result.getPoint()));
+    } else {
+        // Try to snap along the closest constraint
+        for (auto snapper : snappers) {
+            snapper->constrainedSnap(isr, p, bbox_to_snap, cc, &_objects_to_ignore,_unselected_nodes);
+        }
+        result = findBestSnap(p, isr, true);
+    }
+
+    return result.getSnapped() ? result : no_snap;
+}
+
+Inkscape::SnappedPoint SnapManager::constrainedAngularSnap(Inkscape::SnapCandidatePoint const &p,
+                                                            std::optional<Geom::Point> const &p_ref,
+                                                            Geom::Point const &o,
+                                                            unsigned const snaps) const
+{
+    Inkscape::SnappedPoint sp;
+    if (snaps > 0) { // 0 means no angular snapping
+        // p is at an arbitrary angle. Now we should snap this angle to specific increments.
+        // For this we'll calculate the closest two angles, one at each side of the current angle
+        Geom::Line y_axis(Geom::Point(0, 0), Geom::Point(0, 1));
+        Geom::Line p_line(o, p.getPoint());
+        double angle = Geom::angle_between(y_axis, p_line);
+        double angle_incr = M_PI / snaps;
+        double angle_offset = 0;
+        if (p_ref) {
+            Geom::Line p_line_ref(o, *p_ref);
+            angle_offset = Geom::angle_between(y_axis, p_line_ref);
+        }
+        double angle_ceil = round_to_upper_multiple_plus(angle, angle_incr, angle_offset);
+        double angle_floor = round_to_lower_multiple_plus(angle, angle_incr, angle_offset);
+        // We have two angles now. The constrained snapper will try each of them and return the closest
+
+        // Now do the snapping...
+        std::vector<Inkscape::Snapper::SnapConstraint> constraints;
+        constraints.emplace_back(Geom::Line(o, angle_ceil - M_PI/2));
+        constraints.emplace_back(Geom::Line(o, angle_floor - M_PI/2));
+        sp = multipleConstrainedSnaps(p, constraints); // Constraints will always be applied, even if we didn't snap
+        if (!sp.getSnapped()) { // If we haven't snapped then we only had the constraint applied;
+            sp.setTarget(Inkscape::SNAPTARGET_CONSTRAINED_ANGLE);
+        }
+    } else {
+        sp = freeSnap(p);
+    }
+    return sp;
+}
+
+void SnapManager::guideFreeSnap(Geom::Point &p, Geom::Point &origin_or_vector, bool origin, bool freeze_angle) const
+{
+    if (freeze_angle && origin) {
+        g_warning("Dear developer, when snapping guides you shouldn't ask me to freeze the guide's vector when you haven't specified one");
+        // You've supplied me with an origin instead of a vector
+    }
+
+    if (!snapprefs.getSnapEnabledGlobally() || snapprefs.getSnapPostponedGlobally() || !snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_GUIDE)) {
+        return;
+    }
+
+    Inkscape::SnapCandidatePoint candidate(p, Inkscape::SNAPSOURCE_GUIDE);
+    if (origin) {
+        candidate.addOrigin(origin_or_vector);
+    } else {
+        candidate = Inkscape::SnapCandidatePoint(p, Inkscape::SNAPSOURCE_GUIDE_ORIGIN);
+        candidate.addVector(Geom::rot90(origin_or_vector));
+    }
+
+    IntermSnapResults isr;
+    SnapperList snappers = getSnappers();
+    for (SnapperList::const_iterator i = snappers.begin(); i != snappers.end(); ++i) {
+        (*i)->freeSnap(isr, candidate, Geom::OptRect(), nullptr, nullptr);
+    }
+
+    Inkscape::SnappedPoint const s = findBestSnap(candidate, isr, false);
+
+    s.getPointIfSnapped(p);
+
+    if (!freeze_angle && s.getSnapped()) {
+        if (!Geom::are_near(s.getTangent(), Geom::Point(0,0))) { // If the tangent has been set ...
+            origin_or_vector = Geom::rot90(s.getTangent()); // then use it to update the normal of the guide
+            // PS: The tangent might not have been set if we snapped for example to a node
+        }
+    }
+}
+
+void SnapManager::guideConstrainedSnap(Geom::Point &p, SPGuide const &guideline) const
+{
+    if (!snapprefs.getSnapEnabledGlobally() || snapprefs.getSnapPostponedGlobally() || !snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_GUIDE)) {
+        return;
+    }
+
+    Inkscape::SnapCandidatePoint candidate(p, Inkscape::SNAPSOURCE_GUIDE_ORIGIN, Inkscape::SNAPTARGET_UNDEFINED);
+
+    IntermSnapResults isr;
+    Inkscape::Snapper::SnapConstraint cl(guideline.getPoint(), Geom::rot90(guideline.getNormal()));
+
+    SnapperList snappers = getSnappers();
+    for (SnapperList::const_iterator i = snappers.begin(); i != snappers.end(); ++i) {
+        (*i)->constrainedSnap(isr, candidate, Geom::OptRect(), cl, nullptr, nullptr);
+    }
+
+    Inkscape::SnappedPoint const s = findBestSnap(candidate, isr, false);
+    s.getPointIfSnapped(p);
+}
+
+void SnapManager::snapTransformed(
+    std::vector<Inkscape::SnapCandidatePoint> const &points,
+    Geom::Point const &pointer,
+    Inkscape::PureTransform &transform
+    )
+{
+    /* We have a list of points, which we are proposing to transform in some way.  We need to see
+    ** if any of these points, when transformed, snap to anything.  If they do, we return the
+    ** appropriate transformation with `true'; otherwise we return the original scale with `false'.
+    */
+
+    if (points.size() == 0) {
+        transform.best_snapped_point = Inkscape::SnappedPoint(pointer);
+        return;
+    }
+
+    // We will try to snap a set of points, but we don't want to have a snap indicator displayed
+    // for each of them. That's why it's temporarily disabled here, and re-enabled again after we
+    // have finished calling the freeSnap() and constrainedSnap() methods
+    bool _orig_snapindicator_status = _snapindicator;
+    _snapindicator = false;
+
+    transform.snap(this, points, pointer);
+
+    // Allow the snapindicator to be displayed again
+    _snapindicator = _orig_snapindicator_status;
+
+    if (_snapindicator) {
+        if (transform.best_snapped_point.getSnapped()) {
+            _desktop->snapindicator->set_new_snaptarget(transform.best_snapped_point);
+        } else {
+            _desktop->snapindicator->remove_snaptarget();
+        }
+    }
+
+    if (points.size() == 1) {
+        displaySnapsource(Inkscape::SnapCandidatePoint(transform.best_snapped_point.getPoint(), points.at(0).getSourceType()));
+    }
+}
+
+Inkscape::SnappedPoint SnapManager::findBestSnap(Inkscape::SnapCandidatePoint const &p,
+                                                 IntermSnapResults const &isr,
+                                                 bool constrained,
+                                                 bool allowOffScreen,
+                                                 bool to_path_only) const
+{
+    g_assert(_desktop != nullptr);
+
+    /*
+    std::cout << "Type and number of snapped constraints: " << std::endl;
+    std::cout << "  Points      : " << isr.points.size() << std::endl;
+    std::cout << "  Grid lines  : " << isr.grid_lines.size()<< std::endl;
+    std::cout << "  Guide lines : " << isr.guide_lines.size()<< std::endl;
+    std::cout << "  Curves      : " << isr.curves.size()<< std::endl;
+    */
+
+    /*
+    // Display all snap candidates on the canvas
+    _desktop->snapindicator->remove_debugging_points();
+    for (std::list<Inkscape::SnappedPoint>::const_iterator i = isr.points.begin(); i != isr.points.end(); i++) {
+        _desktop->snapindicator->set_new_debugging_point((*i).getPoint());
+    }
+    for (std::list<Inkscape::SnappedCurve>::const_iterator i = isr.curves.begin(); i != isr.curves.end(); i++) {
+        _desktop->snapindicator->set_new_debugging_point((*i).getPoint());
+    }
+    for (std::list<Inkscape::SnappedLine>::const_iterator i = isr.grid_lines.begin(); i != isr.grid_lines.end(); i++) {
+        _desktop->snapindicator->set_new_debugging_point((*i).getPoint());
+    }
+    for (std::list<Inkscape::SnappedLine>::const_iterator i = isr.guide_lines.begin(); i != isr.guide_lines.end(); i++) {
+        _desktop->snapindicator->set_new_debugging_point((*i).getPoint());
+    }
+    */
+
+    // Store all snappoints
+    std::list<Inkscape::SnappedPoint> sp_list;
+
+    // search for the closest snapped point
+    Inkscape::SnappedPoint closestPoint;
+    if (getClosestSP(isr.points, closestPoint)) {
+        sp_list.push_back(closestPoint);
+    }
+
+    // search for the closest snapped curve
+    Inkscape::SnappedCurve closestCurve;
+    // We might have collected the paths only to snap to their intersection, without the intention to snap to the paths themselves
+    // Therefore we explicitly check whether the paths should be considered as snap targets themselves
+    bool exclude_paths = !snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_PATH);
+    if (getClosestCurve(isr.curves, closestCurve, exclude_paths)) {
+        sp_list.emplace_back(closestCurve);
+    }
+
+    // search for the closest snapped grid line
+    Inkscape::SnappedLine closestGridLine;
+    if (getClosestSL(isr.grid_lines, closestGridLine)) {
+        sp_list.emplace_back(closestGridLine);
+    }
+
+    // search for the closest snapped guide line
+    Inkscape::SnappedLine closestGuideLine;
+    if (getClosestSL(isr.guide_lines, closestGuideLine)) {
+        sp_list.emplace_back(closestGuideLine);
+    }
+
+    // When freely snapping to a grid/guide/path, only one degree of freedom is eliminated
+    // Therefore we will try get fully constrained by finding an intersection with another grid/guide/path
+
+    // When doing a constrained snap however, we're already at an intersection of the constrained line and
+    // the grid/guide/path we're snapping to. This snappoint is therefore fully constrained, so there's
+    // no need to look for additional intersections
+    if (!constrained) {
+        if (snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_PATH_INTERSECTION)) {
+            // search for the closest snapped intersection of curves
+            Inkscape::SnappedPoint closestCurvesIntersection;
+            if (getClosestIntersectionCS(isr.curves, p.getPoint(), closestCurvesIntersection, _desktop->dt2doc())) {
+                closestCurvesIntersection.setSource(p.getSourceType());
+                sp_list.push_back(closestCurvesIntersection);
+            }
+        }
+
+        if (snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_PATH_GUIDE_INTERSECTION)) {
+            // search for the closest snapped intersection of a guide with a curve
+            Inkscape::SnappedPoint closestCurveGuideIntersection;
+            if (getClosestIntersectionCL(isr.curves, isr.guide_lines, p.getPoint(), closestCurveGuideIntersection, _desktop->dt2doc())) {
+                closestCurveGuideIntersection.setSource(p.getSourceType());
+                sp_list.push_back(closestCurveGuideIntersection);
+            }
+        }
+
+        // search for the closest snapped intersection of grid lines
+        Inkscape::SnappedPoint closestGridPoint;
+        if (getClosestIntersectionSL(isr.grid_lines, closestGridPoint)) {
+            closestGridPoint.setSource(p.getSourceType());
+            closestGridPoint.setTarget(Inkscape::SNAPTARGET_GRID_INTERSECTION);
+            sp_list.push_back(closestGridPoint);
+        }
+
+        // search for the closest snapped intersection of guide lines
+        Inkscape::SnappedPoint closestGuidePoint;
+        if (getClosestIntersectionSL(isr.guide_lines, closestGuidePoint)) {
+            closestGuidePoint.setSource(p.getSourceType());
+            closestGuidePoint.setTarget(Inkscape::SNAPTARGET_GUIDE_INTERSECTION);
+            sp_list.push_back(closestGuidePoint);
+        }
+
+        // search for the closest snapped intersection of grid with guide lines
+        if (snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_GRID_GUIDE_INTERSECTION)) {
+            Inkscape::SnappedPoint closestGridGuidePoint;
+            if (getClosestIntersectionSL(isr.grid_lines, isr.guide_lines, closestGridGuidePoint)) {
+                closestGridGuidePoint.setSource(p.getSourceType());
+                closestGridGuidePoint.setTarget(Inkscape::SNAPTARGET_GRID_GUIDE_INTERSECTION);
+                sp_list.push_back(closestGridGuidePoint);
+            }
+        }
+    }
+
+    // Filter out all snap targets that do NOT include a path; this is useful when we try to insert
+    // a node in a path (on doubleclick in the node tool). We don't want to change the shape of the
+    // path, so the snapped point must be on a path, and not e.g. on a grid intersection
+    if (to_path_only) {
+        std::list<Inkscape::SnappedPoint>::iterator i = sp_list.begin();
+
+        while (i != sp_list.end()) {
+            Inkscape::SnapTargetType t = (*i).getTarget();
+            if (t == Inkscape::SNAPTARGET_LINE_MIDPOINT ||
+                t == Inkscape::SNAPTARGET_PATH ||
+                t == Inkscape::SNAPTARGET_PATH_PERPENDICULAR ||
+                t == Inkscape::SNAPTARGET_PATH_TANGENTIAL ||
+                t == Inkscape::SNAPTARGET_PATH_INTERSECTION ||
+                t == Inkscape::SNAPTARGET_PATH_GUIDE_INTERSECTION ||
+                t == Inkscape::SNAPTARGET_PATH_CLIP ||
+                t == Inkscape::SNAPTARGET_PATH_MASK ||
+                t == Inkscape::SNAPTARGET_ELLIPSE_QUADRANT_POINT) {
+                ++i;
+            } else {
+                i = sp_list.erase(i);
+            }
+        }
+    }
+
+    // now let's see which snapped point gets a thumbs up
+    Inkscape::SnappedPoint bestSnappedPoint(p.getPoint());
+    // std::cout << "Finding the best snap..." << std::endl;
+    for (std::list<Inkscape::SnappedPoint>::const_iterator i = sp_list.begin(); i != sp_list.end(); ++i) {
+        // std::cout << "sp = " << (*i).getPoint() << " | source = " << (*i).getSource() << " | target = " << (*i).getTarget();
+        bool onScreen = _desktop->get_display_area().contains((*i).getPoint());
+        if (onScreen || allowOffScreen) { // Only snap to points which are not off the screen
+            if ((*i).getSnapDistance() <= (*i).getTolerance()) { // Only snap to points within snapping range
+                // if it's the first point, or if it is closer than the best snapped point so far
+                if (i == sp_list.begin() || bestSnappedPoint.isOtherSnapBetter(*i, false)) {
+                    // then prefer this point over the previous one
+                    bestSnappedPoint = *i;
+                }
+            }
+        }
+        // std::cout << std::endl;
+    }
+
+    // Update the snap indicator, if requested
+    if (_snapindicator) {
+        if (bestSnappedPoint.getSnapped()) {
+            _desktop->snapindicator->set_new_snaptarget(bestSnappedPoint);
+        } else {
+            _desktop->snapindicator->remove_snaptarget();
+        }
+    }
+
+    // std::cout << "findBestSnap = " << bestSnappedPoint.getPoint() << " | dist = " << bestSnappedPoint.getSnapDistance() << std::endl;
+    return bestSnappedPoint;
+}
+
+void SnapManager::setup(SPDesktop const *desktop,
+                        bool snapindicator,
+                        SPObject const *item_to_ignore,
+                        std::vector<Inkscape::SnapCandidatePoint> *unselected_nodes)
+{
+    g_assert(desktop != nullptr);
+    if (_desktop != nullptr) {
+        g_warning("The snapmanager has been set up before, but unSetup() hasn't been called afterwards. It possibly held invalid pointers");
+    }
+    _objects_to_ignore.clear();
+    if (item_to_ignore) {
+        _objects_to_ignore.push_back(item_to_ignore);
+    }
+    _desktop = desktop;
+    _snapindicator = snapindicator;
+    _unselected_nodes = unselected_nodes;
+    _rotation_center_source_items.clear();
+    _findCandidates_already_called = false;
+}
+
+void SnapManager::setup(SPDesktop const *desktop,
+                        bool snapindicator,
+                        std::vector<SPObject const *> &objects_to_ignore,
+                        std::vector<Inkscape::SnapCandidatePoint> *unselected_nodes)
+{
+    g_assert(desktop != nullptr);
+    if (_desktop != nullptr) {
+        g_warning("The snapmanager has been set up before, but unSetup() hasn't been called afterwards. It possibly held invalid pointers");
+    }
+    _objects_to_ignore = objects_to_ignore;
+    _desktop = desktop;
+    _snapindicator = snapindicator;
+    _unselected_nodes = unselected_nodes;
+    _rotation_center_source_items.clear();
+    _findCandidates_already_called = false;
+}
+
+/// Setup, taking the list of items to ignore from the desktop's selection.
+void SnapManager::setupIgnoreSelection(SPDesktop const *desktop,
+                                      bool snapindicator,
+                                      std::vector<Inkscape::SnapCandidatePoint> *unselected_nodes)
+{
+    g_assert(desktop != nullptr);
+    if (_desktop != nullptr) {
+        // Someone has been naughty here! This is dangerous
+        g_warning("The snapmanager has been set up before, but unSetup() hasn't been called afterwards. It possibly held invalid pointers");
+    }
+    _desktop = desktop;
+    _snapindicator = snapindicator;
+    _unselected_nodes = unselected_nodes;
+    _rotation_center_source_items.clear();
+    _findCandidates_already_called = false;
+    _objects_to_ignore.clear();
+
+    Inkscape::Selection *sel = _desktop->selection;
+    auto items = sel->items();
+    for (auto i=items.begin();i!=items.end();++i) {
+        _objects_to_ignore.push_back(*i);
+    }
+}
+
+SPDocument *SnapManager::getDocument() const
+{
+    return _named_view->document;
+}
+
+//Geom::Point SnapManager::_transformPoint(Inkscape::SnapCandidatePoint const &p,
+//                                        Transformation const transformation_type,
+//                                        Geom::Point const &transformation,
+//                                        Geom::Point const &origin,
+//                                        Geom::Dim2 const dim,
+//                                        bool const uniform) const
+//{
+//    /* Work out the transformed version of this point */
+//    Geom::Point transformed;
+//    switch (transformation_type) {
+//        case TRANSLATE:
+//            transformed = p.getPoint() + transformation;
+//            break;
+//        case SCALE:
+//            transformed = (p.getPoint() - origin) * Geom::Scale(transformation[Geom::X], transformation[Geom::Y]) + origin;
+//            break;
+//        case STRETCH:
+//        {
+//            Geom::Scale s(1, 1);
+//            if (uniform)
+//                s[Geom::X] = s[Geom::Y] = transformation[dim];
+//            else {
+//                s[dim] = transformation[dim];
+//                s[1 - dim] = 1;
+//            }
+//            transformed = ((p.getPoint() - origin) * s) + origin;
+//            break;
+//        }
+//        case SKEW:
+//            // Apply the skew factor
+//            transformed[dim] = (p.getPoint())[dim] + transformation[0] * ((p.getPoint())[1 - dim] - origin[1 - dim]);
+//            // While skewing, mirroring and scaling (by integer multiples) in the opposite direction is also allowed.
+//            // Apply that scale factor here
+//            transformed[1-dim] = (p.getPoint() - origin)[1 - dim] * transformation[1] + origin[1 - dim];
+//            break;
+//        case ROTATE:
+//            // for rotations: transformation[0] stores the angle in radians
+//            transformed = (p.getPoint() - origin) * Geom::Rotate(transformation[0]) + origin;
+//            break;
+//        default:
+//            g_assert_not_reached();
+//    }
+//
+//    return transformed;
+//}
+
+/**
+ * Mark the location of the snap source (not the snap target!) on the canvas by drawing a symbol.
+ *
+ * @param point_type Category of points to which the source point belongs: node, guide or bounding box
+ * @param p The transformed position of the source point, paired with an identifier of the type of the snap source.
+ */
+void SnapManager::displaySnapsource(Inkscape::SnapCandidatePoint const &p) const {
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    if (prefs->getBool("/options/snapclosestonly/value")) {
+        Inkscape::SnapSourceType t = p.getSourceType();
+        bool p_is_a_node = t & Inkscape::SNAPSOURCE_NODE_CATEGORY;
+        bool p_is_a_bbox = t & Inkscape::SNAPSOURCE_BBOX_CATEGORY;
+        bool p_is_other = (t & Inkscape::SNAPSOURCE_OTHERS_CATEGORY) || (t & Inkscape::SNAPSOURCE_DATUMS_CATEGORY);
+
+        g_assert(_desktop != nullptr);
+        if (snapprefs.getSnapEnabledGlobally() && (p_is_other || (p_is_a_node && snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_NODE_CATEGORY)) || (p_is_a_bbox && snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_BBOX_CATEGORY)))) {
+            _desktop->snapindicator->set_new_snapsource(p);
+        } else {
+            _desktop->snapindicator->remove_snapsource();
+        }
+    }
+}
+
+SPGuide const *SnapManager::getGuideToIgnore() const
+{
+    for (auto item : _objects_to_ignore) {
+        if (auto guide = dynamic_cast<SPGuide const *>(item)) {
+            return guide;
+        }
+    }
+    return nullptr;
+}
+SPPage const *SnapManager::getPageToIgnore() const
+{
+    for (auto item : _objects_to_ignore) {
+        if (auto page = dynamic_cast<SPPage const *>(item)) {
+            return page;
+        }
+    }
+    return nullptr;
+}
+
+
+void SnapManager::_findCandidates(SPObject* parent,
+                                 std::vector<SPObject const *> const *it,
+                                 Geom::Rect const &bbox_to_snap,
+                                 bool const clip_or_mask,
+                                 Geom::Affine const additional_affine)
+{
+    SPDesktop const *dt = getDesktop();
+    if (dt == nullptr) {
+        g_error("desktop == NULL, so we cannot snap; please inform the developers of this bug");
+        return;
+        // Apparently the setup() method from the SnapManager class hasn't been called before trying to snap.
+    }
+
+    static int recursion_level = 0;
+
+    if (recursion_level == 0) {
+        if (_findCandidates_already_called) { // In case we have already been called by another snapper,
+            return; // then we don't need to search for candidates again
+        }
+        _findCandidates_already_called = true;
+        _obj_snapper_candidates->clear();
+        _align_snapper_candidates->clear();
+    }
+    recursion_level++;
+
+    Geom::Rect bbox_to_snap_incl = bbox_to_snap; // _incl means: will include the snapper tolerance
+    bbox_to_snap_incl.expandBy(object.getSnapperTolerance()); // see?
+
+    for (auto& o: parent->children) {
+        SPItem *item = dynamic_cast<SPItem *>(&o);
+        if (item && !(dt->itemIsHidden(item) && !clip_or_mask)) {
+            // Fix LPE boolops self-snapping
+            bool stop = false;
+            if (item->style) {
+                SPFilter *filt = item->style->getFilter();
+                if (filt && filt->getId() && strcmp(filt->getId(), "selectable_hidder_filter") == 0) {
+                    stop = true;
+                }
+                SPLPEItem *lpeitem = dynamic_cast<SPLPEItem *>(item);
+                if (lpeitem && lpeitem->hasPathEffectOfType(Inkscape::LivePathEffect::EffectType::BOOL_OP)) {
+                    stop = true;
+                }
+            }
+            if (stop && it) {
+                stop = false;
+                for (auto skipitem : *it) {
+                    if (skipitem && skipitem->style) {
+                        SPItem *toskip = dynamic_cast<SPItem *>(const_cast<SPObject *>(skipitem));
+                        if (toskip) {
+                            SPFilter *filt = toskip->style->getFilter();
+                            if (filt && filt->getId() && strcmp(filt->getId(), "selectable_hidder_filter") == 0) {
+                                stop = true;
+                                break;
+                            }
+
+                            SPLPEItem *lpeitem = dynamic_cast<SPLPEItem *>(toskip);
+                            if (!stop && lpeitem &&
+                                lpeitem->hasPathEffectOfType(Inkscape::LivePathEffect::EffectType::BOOL_OP)) {
+                                stop = true;
+                                break;
+                            }
+                        }
+                    }
+                }
+                if (stop) {
+                    continue;
+                }
+            }
+            // Snapping to items in a locked layer is allowed
+            // Don't snap to hidden objects, unless they're a clipped path or a mask
+            /* See if this item is on the ignore list */
+            std::vector<SPObject const *>::const_iterator i;
+            if (it != nullptr) {
+                i = it->begin();
+                while (i != it->end() && *i != &o) {
+                    ++i;
+                }
+            }
+
+            if (it == nullptr || i == it->end()) {
+                if (item) {
+                    if (!clip_or_mask) { // cannot clip or mask more than once
+                        // The current item is not a clipping path or a mask, but might
+                        // still be the subject of clipping or masking itself ; if so, then
+                        // we should also consider that path or mask for snapping to
+                        SPObject *obj = item->getClipObject();
+                        if (obj && snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_PATH_CLIP)) {
+                            _findCandidates(obj, it, bbox_to_snap, true, item->i2doc_affine());
+                        }
+                        obj = item->getMaskObject();
+                        if (obj && snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_PATH_MASK)) {
+                            _findCandidates(obj, it, bbox_to_snap, true, item->i2doc_affine());
+                        }
+                    }
+
+                    if (dynamic_cast<SPGroup *>(item)) {
+                        _findCandidates(&o, it, bbox_to_snap, clip_or_mask, additional_affine);
+                    } else {
+                        Geom::OptRect bbox_of_item;
+                        Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+                        int prefs_bbox = prefs->getBool("/tools/bounding_box", false);
+                        // We'll only need to obtain the visual bounding box if the user preferences tell
+                        // us to, AND if we are snapping to the bounding box itself. If we're snapping to
+                        // paths only, then we can just as well use the geometric bounding box (which is faster)
+                        SPItem::BBoxType bbox_type = (!prefs_bbox && snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_BBOX_CATEGORY)) ?
+                            SPItem::VISUAL_BBOX : SPItem::GEOMETRIC_BBOX;
+                        if (clip_or_mask) {
+                            // Oh oh, this will get ugly. We cannot use sp_item_i2d_affine directly because we need to
+                            // insert an additional transformation in document coordinates (code copied from sp_item_i2d_affine)
+                            bbox_of_item = item->bounds(bbox_type, item->i2doc_affine() * additional_affine * dt->doc2dt());
+                        } else {
+                            bbox_of_item = item->desktopBounds(bbox_type);
+                        }
+                        if (bbox_of_item) {
+                            bool overflow = false;
+                            // See if the item is within range
+                            auto display_area = getDesktop()->get_display_area().bounds();
+                            if (display_area.intersects(*bbox_of_item)) {
+                                // Finally add the object to _candidates.
+                                _align_snapper_candidates->push_back(Inkscape::SnapCandidateItem(item, clip_or_mask, additional_affine));
+                                // For debugging: print the id of the candidate to the console
+                                // SPObject *obj = (SPObject*)item;
+                                // std::cout << "Snap candidate added: " << obj->getId() << std::endl;
+
+                                if (bbox_to_snap_incl.intersects(*bbox_of_item)
+                                        || (snapprefs.isTargetSnappable(Inkscape::SNAPTARGET_ROTATION_CENTER) && bbox_to_snap_incl.contains(item->getCenter()))) { // rotation center might be outside of the bounding box
+                                    // This item is within snapping range, so record it as a candidate
+                                    _obj_snapper_candidates->push_back(Inkscape::SnapCandidateItem(item, clip_or_mask, additional_affine));
+                                    // For debugging: print the id of the candidate to the console
+                                    // SPObject *obj = (SPObject*)item;
+                                    // std::cout << "Snap candidate added: " << obj->getId() << std::endl;
+                                }
+
+                                if (_align_snapper_candidates->size() > 200) { // This makes Inkscape crawl already
+                                    overflow = true;
+                                }
+                            }
+
+                            if (overflow) {
+                                static Glib::Timer timer;
+                                if (timer.elapsed() > 1.0) {
+                                    timer.reset();
+                                    std::cout << "Warning: limit of 200 snap target paths reached, some will be ignored" << std::endl;
+                                }
+                                break;
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    recursion_level--;
+}
+/*
+  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:fileencoding=utf-8:textwidth=99 :