Adding upstream version 1.2.2.upstream/1.2.2upstream

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

10 files changed, 2120 insertions, 0 deletions

diff --git a/src/ui/knot/README b/src/ui/knot/README
new file mode 100644
index 0000000..7a76593
--- /dev/null
+++ b/src/ui/knot/README
@@ -0,0 +1,62 @@
+
+
+This directory contains code related to on-screen editing knots.
+
+Note that there are classes with similar functionality based on the ControlPoint class in src/ui/tool.
+
+Classes here:
+
+  * SPKnot              A class that describes a knot (size, type, position, state, etc.) with some signals.
+
+  * KnotHolderEntity    A class that has an SPKnot with some signals connections.
+
+      Derived classes:
+
+         LPEKnotHolderEntity
+         PatternKnotHolderEntity
+         HatchKnotHolderEntity
+         FilterKnotHolderEntity
+         RectKnotHolderEntityRX
+         RectKnotHolderEntityRY
+         RectKnotHolderEntityWH
+         RectKnotHolderEntityXY
+         RectKnotHolderEntityCenter
+         Box3DKnotHolderEntity
+         Box3DKnotHolderEntityCenter
+         ArcKnotHolderEntityStart
+         ArcKnotHolderEntityEnd
+         ArcKnotHolderEntityRX
+         ArcKnotHolderEntityRY
+         ArcKnotHolderEntityCenter
+         StarKnotHolderEntity1
+         StarKnotHolderEntity2
+         StarKnotHolderEntityCenter
+         SpiralKnotHolderEntityInner
+         SpiralKnotHolderEntityOuter
+         SpiralKnotHolderEntityCenter
+         OffsetKnotHolderEntity
+         TextKnotHolderEntityInlineSize
+         TextKnotHolderEntityShapeInside
+         FilletChamferKnotHolderEntity
+         TransformedPointParamKnotHolderEntity_Vector
+         PowerStrokePointArrayParamKnotHolderEntity
+         PowerStrokePointArrayParamKnotHolderEntity
+         PointParamKnotHolderEntity
+         VectorParamKnotHolderEntity_Origin
+         VectorParamKnotHolderEntity_Vector
+
+         And many classes derived from above!
+
+  * KnotHolder         A class that has one or more overlapping knots via KnotHolderEntity's.
+
+      Derived classes:
+
+         ArcKnotHolder
+         Box3DKnotHolder
+         FlowtextKnotHolder
+         MiscKnotHolder
+         OffsetKnotHolder
+         RectKnotHolder
+         SpiralKnotHolder
+         StarKnotHolder
+         TextKnotHolder
diff --git a/src/ui/knot/knot-enums.h b/src/ui/knot/knot-enums.h
new file mode 100644
index 0000000..4f12cd7
--- /dev/null
+++ b/src/ui/knot/knot-enums.h
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#ifndef SEEN_KNOT_ENUMS_H
+#define SEEN_KNOT_ENUMS_H
+
+/**
+ * @file
+ * Some enums used by SPKnot and by related types \& functions. 
+ */
+/*
+ * Authors:
+ *   Lauris Kaplinski <lauris@kaplinski.com>
+ *
+ * Copyright (C) 1999-2002 authors
+ * Copyright (C) 2001-2002 Ximian, Inc.
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+enum SPKnotStateType {
+    SP_KNOT_STATE_NORMAL,
+    SP_KNOT_STATE_MOUSEOVER,
+    SP_KNOT_STATE_DRAGGING,
+    SP_KNOT_STATE_SELECTED,
+    SP_KNOT_STATE_HIDDEN
+};
+
+#define SP_KNOT_VISIBLE_STATES 4
+
+enum {
+    SP_KNOT_VISIBLE = 1 << 0,
+    SP_KNOT_MOUSEOVER = 1 << 1,
+    SP_KNOT_DRAGGING = 1 << 2,
+    SP_KNOT_GRABBED = 1 << 3,
+    SP_KNOT_SELECTED = 1 << 4
+};
+
+
+#endif /* !SEEN_KNOT_ENUMS_H */
+
+/*
+  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 :
diff --git a/src/ui/knot/knot-holder-entity.cpp b/src/ui/knot/knot-holder-entity.cpp
new file mode 100644
index 0000000..a339539
--- /dev/null
+++ b/src/ui/knot/knot-holder-entity.cpp
@@ -0,0 +1,454 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * KnotHolderEntity definition.
+ *
+ * Authors:
+ *   Mitsuru Oka <oka326@parkcity.ne.jp>
+ *   Maximilian Albert <maximilian.albert@gmail.com>
+ *   Abhishek Sharma
+ *
+ * Copyright (C) 1999-2001 Lauris Kaplinski
+ * Copyright (C) 2000-2001 Ximian, Inc.
+ * Copyright (C) 2001 Mitsuru Oka
+ * Copyright (C) 2004 Monash University
+ * Copyright (C) 2008 Maximilian Albert
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include "knot-holder-entity.h"
+
+#include "knot-holder.h"
+
+#include "desktop.h"
+#include "inkscape.h"
+#include "preferences.h"
+#include "snap.h"
+#include "style.h"
+
+#include "live_effects/effect.h"
+#include "object/sp-hatch.h"
+#include "object/sp-item.h"
+#include "object/sp-namedview.h"
+#include "object/sp-pattern.h"
+#include "object/sp-marker.h"
+
+#include "display/control/canvas-item-ctrl.h"
+
+void KnotHolderEntity::create(SPDesktop *desktop, SPItem *item, KnotHolder *parent,
+                              Inkscape::CanvasItemCtrlType type,
+                              Glib::ustring const & name,
+                              const gchar *tip, guint32 color)
+{
+    if (!desktop) {
+        desktop = parent->getDesktop();
+    }
+
+    g_assert(item == parent->getItem());
+    g_assert(desktop && desktop == parent->getDesktop());
+    g_assert(knot == nullptr);
+
+    parent_holder = parent;
+    this->item = item; // TODO: remove the item either from here or from knotholder.cpp
+    this->desktop = desktop;
+
+    my_counter = KnotHolderEntity::counter++;
+
+    knot = new SPKnot(desktop, tip, type, name);
+    knot->fill [SP_KNOT_STATE_NORMAL] = color;
+    knot->ctrl->set_fill(color);
+    update_knot();
+    knot->show();
+
+    _mousedown_connection = knot->mousedown_signal.connect(sigc::mem_fun(*parent_holder, &KnotHolder::knot_mousedown_handler));
+    _moved_connection = knot->moved_signal.connect(sigc::mem_fun(*parent_holder, &KnotHolder::knot_moved_handler));
+    _click_connection = knot->click_signal.connect(sigc::mem_fun(*parent_holder, &KnotHolder::knot_clicked_handler));
+    _ungrabbed_connection = knot->ungrabbed_signal.connect(sigc::mem_fun(*parent_holder, &KnotHolder::knot_ungrabbed_handler));
+}
+                              
+KnotHolderEntity::~KnotHolderEntity()
+{
+    _mousedown_connection.disconnect();
+    _moved_connection.disconnect();
+    _click_connection.disconnect();
+    _ungrabbed_connection.disconnect();
+
+    /* unref should call destroy */
+    if (knot) {
+        //g_object_unref(knot);
+        knot_unref(knot);
+    } else {
+        // FIXME: This shouldn't occur. Perhaps it is caused by LPE PointParams being knotholder entities, too
+        //        If so, it will likely be fixed with upcoming refactoring efforts.
+        g_return_if_fail(knot);
+    }
+}
+
+void
+KnotHolderEntity::update_knot()
+{
+    Geom::Point knot_pos(knot_get());
+    if (knot_pos.isFinite()) {
+        Geom::Point dp(knot_pos * parent_holder->getEditTransform() * item->i2dt_affine());
+
+        _moved_connection.block();
+        knot->setPosition(dp, SP_KNOT_STATE_NORMAL);
+        _moved_connection.unblock();
+    } else {
+        // knot coords are non-finite, hide knot
+        knot->hide();
+    }
+}
+
+Geom::Point
+KnotHolderEntity::snap_knot_position(Geom::Point const &p, guint state)
+{
+    if (state & GDK_SHIFT_MASK) { // Don't snap when shift-key is held
+        return p;
+    }
+
+    Geom::Affine const i2dt (parent_holder->getEditTransform() * item->i2dt_affine());
+    Geom::Point s = p * i2dt;
+
+    if (!desktop) std::cout << "No desktop" << std::endl;
+    if (!desktop->namedview) std::cout << "No named view" << std::endl;
+    SnapManager &m = desktop->namedview->snap_manager;
+    m.setup(desktop, true, item);
+    m.freeSnapReturnByRef(s, Inkscape::SNAPSOURCE_NODE_HANDLE);
+    m.unSetup();
+
+    return s * i2dt.inverse();
+}
+
+Geom::Point
+KnotHolderEntity::snap_knot_position_constrained(Geom::Point const &p, Inkscape::Snapper::SnapConstraint const &constraint, guint state)
+{
+    if (state & GDK_SHIFT_MASK) { // Don't snap when shift-key is held
+        return p;
+    }
+
+    Geom::Affine const i2d (parent_holder->getEditTransform() * item->i2dt_affine());
+    Geom::Point s = p * i2d;
+
+    SnapManager &m = desktop->namedview->snap_manager;
+    m.setup(desktop, true, item);
+
+    // constrainedSnap() will first project the point p onto the constraint line and then try to snap along that line.
+    // This way the constraint is already enforced, no need to worry about that later on
+    Inkscape::Snapper::SnapConstraint transformed_constraint = Inkscape::Snapper::SnapConstraint(constraint.getPoint() * i2d, (constraint.getPoint() + constraint.getDirection()) * i2d - constraint.getPoint() * i2d);
+    m.constrainedSnapReturnByRef(s, Inkscape::SNAPSOURCE_NODE_HANDLE, transformed_constraint);
+    m.unSetup();
+
+    return s * i2d.inverse();
+}
+
+void
+LPEKnotHolderEntity::knot_ungrabbed(Geom::Point const &p, Geom::Point const &origin, guint state)
+{
+    Inkscape::LivePathEffect::Effect *effect = _effect;
+    if (effect) {
+        effect->refresh_widgets = true;
+        effect->writeParamsToSVG();
+    }
+}
+
+/* Pattern manipulation */
+
+/*  TODO: this pattern manipulation is not able to handle general transformation matrices. Only matrices that are the result of a pure scale times a pure rotation. */
+
+void
+PatternKnotHolderEntityXY::knot_set(Geom::Point const &p, Geom::Point const &origin, guint state)
+{
+    // FIXME: this snapping should be done together with knowing whether control was pressed. If GDK_CONTROL_MASK, then constrained snapping should be used.
+    Geom::Point p_snapped = snap_knot_position(p, state);
+
+    if ( state & GDK_CONTROL_MASK ) {
+        if (fabs((p - origin)[Geom::X]) > fabs((p - origin)[Geom::Y])) {
+            p_snapped[Geom::Y] = origin[Geom::Y];
+        } else {
+            p_snapped[Geom::X] = origin[Geom::X];
+        }
+    }
+
+    if (state)  {
+        Geom::Point const q = p_snapped - knot_get();
+        item->adjust_pattern(Geom::Translate(q), false, _fill ? TRANSFORM_FILL : TRANSFORM_STROKE);
+    }
+
+    item->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
+}
+
+static Geom::Point sp_pattern_knot_get(SPPattern const *pat, gdouble x, gdouble y)
+{
+    return Geom::Point(x, y) * pat->getTransform();
+}
+
+bool
+PatternKnotHolderEntity::knot_missing() const
+{
+    SPPattern *pat = _pattern();
+    return (pat == nullptr);
+}
+
+SPPattern*
+PatternKnotHolderEntity::_pattern() const
+{
+    return _fill ? SP_PATTERN(item->style->getFillPaintServer()) : SP_PATTERN(item->style->getStrokePaintServer());
+}
+
+Geom::Point
+PatternKnotHolderEntityXY::knot_get() const
+{
+    SPPattern *pat = _pattern();
+    return sp_pattern_knot_get(pat, 0, 0);
+}
+
+Geom::Point
+PatternKnotHolderEntityAngle::knot_get() const
+{
+    SPPattern *pat = _pattern();
+    return sp_pattern_knot_get(pat, pat->width(), 0);
+}
+
+Geom::Point
+PatternKnotHolderEntityScale::knot_get() const
+{
+    SPPattern *pat = _pattern();
+    return sp_pattern_knot_get(pat, pat->width(), pat->height());
+}
+
+void
+PatternKnotHolderEntityAngle::knot_set(Geom::Point const &p, Geom::Point const &/*origin*/, guint state)
+{
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    int const snaps = prefs->getInt("/options/rotationsnapsperpi/value", 12);
+
+    SPPattern *pat = _fill ? SP_PATTERN(item->style->getFillPaintServer()) : SP_PATTERN(item->style->getStrokePaintServer());
+
+    // get the angle from pattern 0,0 to the cursor pos
+    Geom::Point transform_origin = sp_pattern_knot_get(pat, 0, 0);
+    gdouble theta = atan2(p - transform_origin);
+    gdouble theta_old = atan2(knot_get() - transform_origin);
+
+    if ( state & GDK_CONTROL_MASK ) {
+        /* Snap theta */
+        double snaps_radian = M_PI/snaps;
+        theta = std::round(theta/snaps_radian) * snaps_radian;
+    }
+
+    Geom::Affine rot = Geom::Translate(-transform_origin)
+                     * Geom::Rotate(theta - theta_old)
+                     * Geom::Translate(transform_origin);
+    item->adjust_pattern(rot, false, _fill ? TRANSFORM_FILL : TRANSFORM_STROKE);
+    item->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
+}
+
+void
+PatternKnotHolderEntityScale::knot_set(Geom::Point const &p, Geom::Point const &origin, guint state)
+{
+    SPPattern *pat = _pattern();
+
+    // FIXME: this snapping should be done together with knowing whether control was pressed. If GDK_CONTROL_MASK, then constrained snapping should be used.
+    Geom::Point p_snapped = snap_knot_position(p, state);
+
+    // Get the new scale from the position of the knotholder
+    Geom::Affine transform = pat->getTransform();
+    Geom::Affine transform_inverse = transform.inverse();
+    Geom::Point d = p_snapped * transform_inverse;
+    Geom::Point d_origin = origin * transform_inverse;
+    Geom::Point origin_dt;
+    gdouble pat_x = pat->width();
+    gdouble pat_y = pat->height();
+    if ( state & GDK_CONTROL_MASK ) {
+        // if ctrl is pressed: use 1:1 scaling
+        d = d_origin * (d.length() / d_origin.length());
+    }
+
+    Geom::Affine rot = Geom::Translate(-origin_dt)
+                     * Geom::Scale(d.x() / pat_x, d.y() / pat_y)
+                     * Geom::Translate(origin_dt)
+                     * transform;
+
+    item->adjust_pattern(rot, true, _fill ? TRANSFORM_FILL : TRANSFORM_STROKE);
+    item->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
+}
+
+/* Hatch manipulation */
+bool HatchKnotHolderEntity::knot_missing() const
+{
+    SPHatch *hatch = _hatch();
+    return (hatch == nullptr);
+}
+
+SPHatch *HatchKnotHolderEntity::_hatch() const
+{
+    return _fill ? SP_HATCH(item->style->getFillPaintServer()) : SP_HATCH(item->style->getStrokePaintServer());
+}
+
+static Geom::Point sp_hatch_knot_get(SPHatch const *hatch, gdouble x, gdouble y)
+{
+    return Geom::Point(x, y) * hatch->hatchTransform();
+}
+
+Geom::Point HatchKnotHolderEntityXY::knot_get() const
+{
+    SPHatch *hatch = _hatch();
+    return sp_hatch_knot_get(hatch, 0, 0);
+}
+
+Geom::Point HatchKnotHolderEntityAngle::knot_get() const
+{
+    SPHatch *hatch = _hatch();
+    return sp_hatch_knot_get(hatch, hatch->pitch(), 0);
+}
+
+Geom::Point HatchKnotHolderEntityScale::knot_get() const
+{
+    SPHatch *hatch = _hatch();
+    return sp_hatch_knot_get(hatch, hatch->pitch(), hatch->pitch());
+}
+
+void HatchKnotHolderEntityXY::knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state)
+{
+    Geom::Point p_snapped = snap_knot_position(p, state);
+
+    if (state & GDK_CONTROL_MASK) {
+        if (fabs((p - origin)[Geom::X]) > fabs((p - origin)[Geom::Y])) {
+            p_snapped[Geom::Y] = origin[Geom::Y];
+        } else {
+            p_snapped[Geom::X] = origin[Geom::X];
+        }
+    }
+
+    if (state) {
+        Geom::Point const q = p_snapped - knot_get();
+        item->adjust_hatch(Geom::Translate(q), false, _fill ? TRANSFORM_FILL : TRANSFORM_STROKE);
+    }
+
+    item->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
+}
+
+void HatchKnotHolderEntityAngle::knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state)
+{
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    int const snaps = prefs->getInt("/options/rotationsnapsperpi/value", 12);
+
+    SPHatch *hatch = _hatch();
+
+    // get the angle from hatch 0,0 to the cursor pos
+    Geom::Point transform_origin = sp_hatch_knot_get(hatch, 0, 0);
+    gdouble theta = atan2(p - transform_origin);
+    gdouble theta_old = atan2(knot_get() - transform_origin);
+
+    if (state & GDK_CONTROL_MASK) {
+        /* Snap theta */
+        double snaps_radian = M_PI/snaps;
+        theta = std::round(theta/snaps_radian) * snaps_radian;
+    }
+
+    Geom::Affine rot =
+        Geom::Translate(-transform_origin) * Geom::Rotate(theta - theta_old) * Geom::Translate(transform_origin);
+    item->adjust_hatch(rot, false, _fill ? TRANSFORM_FILL : TRANSFORM_STROKE);
+    item->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
+}
+
+void HatchKnotHolderEntityScale::knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state)
+{
+    SPHatch *hatch = _hatch();
+
+    // FIXME: this snapping should be done together with knowing whether control was pressed.
+    // If GDK_CONTROL_MASK, then constrained snapping should be used.
+    Geom::Point p_snapped = snap_knot_position(p, state);
+
+    // Get the new scale from the position of the knotholder
+    Geom::Affine transform = hatch->hatchTransform();
+    Geom::Affine transform_inverse = transform.inverse();
+    Geom::Point d = p_snapped * transform_inverse;
+    Geom::Point d_origin = origin * transform_inverse;
+    Geom::Point origin_dt;
+    gdouble hatch_pitch = hatch->pitch();
+    if (state & GDK_CONTROL_MASK) {
+        // if ctrl is pressed: use 1:1 scaling
+        d = d_origin * (d.length() / d_origin.length());
+    }
+
+    Geom::Affine scale = Geom::Translate(-origin_dt) * Geom::Scale(d.x() / hatch_pitch, d.y() / hatch_pitch) *
+                         Geom::Translate(origin_dt) * transform;
+
+    item->adjust_hatch(scale, true, _fill ? TRANSFORM_FILL : TRANSFORM_STROKE);
+    item->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
+}
+
+/* Filter manipulation */
+void FilterKnotHolderEntity::knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state)
+{
+    // FIXME: this snapping should be done together with knowing whether control was pressed. If GDK_CONTROL_MASK, then constrained snapping should be used.
+    Geom::Point p_snapped = snap_knot_position(p, state);
+
+    if ( state & GDK_CONTROL_MASK ) {
+        if (fabs((p - origin)[Geom::X]) > fabs((p - origin)[Geom::Y])) {
+            p_snapped[Geom::Y] = origin[Geom::Y];
+        } else {
+            p_snapped[Geom::X] = origin[Geom::X];
+        }
+    }
+
+    if (state)  {
+        SPFilter *filter = (item->style) ? item->style->getFilter() : nullptr;
+        if(!filter) return;
+        Geom::OptRect orig_bbox = item->visualBounds();
+        std::unique_ptr<Geom::Rect> new_bbox(_topleft ? new Geom::Rect(p,orig_bbox->max()) : new Geom::Rect(orig_bbox->min(), p));
+
+        if (!filter->width._set) {
+            filter->width.set(SVGLength::PERCENT, 1.2);
+        }
+        if (!filter->height._set) {
+            filter->height.set(SVGLength::PERCENT, 1.2);
+        }
+        if (!filter->x._set) {
+            filter->x.set(SVGLength::PERCENT, -0.1);
+        }
+        if (!filter->y._set) {
+            filter->y.set(SVGLength::PERCENT, -0.1);
+        }
+
+        if(_topleft) {
+            float x_a = filter->width.computed;
+            float y_a = filter->height.computed;
+            filter->height.scale(new_bbox->height()/orig_bbox->height());
+            filter->width.scale(new_bbox->width()/orig_bbox->width());
+            float x_b = filter->width.computed;
+            float y_b = filter->height.computed;
+            filter->x.set(filter->x.unit, filter->x.computed + x_a - x_b);
+            filter->y.set(filter->y.unit, filter->y.computed + y_a - y_b);
+        } else {
+            filter->height.scale(new_bbox->height()/orig_bbox->height());
+            filter->width.scale(new_bbox->width()/orig_bbox->width());
+        }
+        filter->auto_region = false;
+        filter->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
+
+    }
+
+    item->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
+}
+
+Geom::Point FilterKnotHolderEntity::knot_get() const
+{
+    SPFilter *filter = (item->style) ? item->style->getFilter() : nullptr;
+    if(!filter) return Geom::Point(Geom::infinity(), Geom::infinity());
+    Geom::OptRect r = item->visualBounds();
+    if (_topleft) return Geom::Point(r->min());
+    else return Geom::Point(r->max());
+}
+
+/*
+  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 :
diff --git a/src/ui/knot/knot-holder-entity.h b/src/ui/knot/knot-holder-entity.h
new file mode 100644
index 0000000..3195c2a
--- /dev/null
+++ b/src/ui/knot/knot-holder-entity.h
@@ -0,0 +1,205 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#ifndef SEEN_KNOT_HOLDER_ENTITY_H
+#define SEEN_KNOT_HOLDER_ENTITY_H
+/*
+ * Authors:
+ *   Mitsuru Oka <oka326@parkcity.ne.jp>
+ *   Maximilian Albert <maximilian.albert@gmail.com>
+ *
+ * Copyright (C) 1999-2001 Lauris Kaplinski
+ * Copyright (C) 2000-2001 Ximian, Inc.
+ * Copyright (C) 2001 Mitsuru Oka
+ * Copyright (C) 2004 Monash University
+ * Copyright (C) 2008 Maximilian Albert
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include <2geom/forward.h>
+
+#include "knot.h"
+#include "snapper.h"
+
+#include "display/control/canvas-item-enums.h"
+
+class SPHatch;
+class SPItem;
+class SPKnot;
+class SPDesktop;
+class SPPattern;
+class KnotHolder;
+
+namespace Inkscape {
+namespace LivePathEffect {
+    class Effect;
+} // namespace LivePathEffect
+} // namespace Inkscape
+
+typedef void (* SPKnotHolderSetFunc) (SPItem *item, Geom::Point const &p, Geom::Point const &origin, unsigned int state);
+typedef Geom::Point (* SPKnotHolderGetFunc) (SPItem *item);
+
+/**
+ * KnotHolderEntity definition.
+ */
+class KnotHolderEntity {
+public:
+    KnotHolderEntity() {}
+    virtual ~KnotHolderEntity();
+
+    void create(SPDesktop *desktop, SPItem *item, KnotHolder *parent,
+                Inkscape::CanvasItemCtrlType type = Inkscape::CANVAS_ITEM_CTRL_TYPE_DEFAULT,
+                Glib::ustring const & name = Glib::ustring("unknown"),
+                char const *tip = "",
+                guint32 color = 0xffffff00);
+
+    /* the get/set/click handlers are virtual functions; each handler class for a knot
+       should be derived from KnotHolderEntity and override these functions */
+    virtual void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) = 0;
+    virtual void knot_ungrabbed(Geom::Point const &p, Geom::Point const &origin, unsigned int state) = 0;
+    virtual bool knot_missing() const { return false; }
+    virtual Geom::Point knot_get() const = 0;
+    virtual void knot_click(unsigned int /*state*/) {}
+
+    void update_knot();
+
+//private:
+    Geom::Point snap_knot_position(Geom::Point const &p, unsigned int state);
+    Geom::Point snap_knot_position_constrained(Geom::Point const &p, Inkscape::Snapper::SnapConstraint const &constraint, unsigned int state);
+
+    SPKnot *knot = nullptr;
+    SPItem *item = nullptr;
+    SPDesktop *desktop = nullptr;
+    KnotHolder *parent_holder = nullptr;
+
+    int my_counter = 0;
+    inline static int counter = 0;
+
+    /** Connection to \a knot's "moved" signal. */
+    unsigned int   handler_id = 0;
+    /** Connection to \a knot's "clicked" signal. */
+    unsigned int   _click_handler_id = 0;
+    /** Connection to \a knot's "ungrabbed" signal. */
+    unsigned int   _ungrab_handler_id = 0;
+
+private:
+    sigc::connection _mousedown_connection;
+    sigc::connection _moved_connection;
+    sigc::connection _click_connection;
+    sigc::connection _ungrabbed_connection;
+};
+
+// derived KnotHolderEntity class for LPEs
+class LPEKnotHolderEntity : public KnotHolderEntity {
+public:
+    LPEKnotHolderEntity(Inkscape::LivePathEffect::Effect *effect) : _effect(effect) {};
+    void knot_ungrabbed(Geom::Point const &p, Geom::Point const &origin, guint state) override;
+protected:
+    Inkscape::LivePathEffect::Effect *_effect;
+};
+
+/* pattern manipulation */
+
+class PatternKnotHolderEntity : public KnotHolderEntity {
+  public:
+    PatternKnotHolderEntity(bool fill) : KnotHolderEntity(), _fill(fill) {}
+    bool knot_missing() const override;
+    void knot_ungrabbed(Geom::Point const &p, Geom::Point const &origin, guint state) override{};
+
+  protected:
+    // true if the entity tracks fill, false for stroke
+    bool _fill;
+    SPPattern *_pattern() const;
+};
+
+class PatternKnotHolderEntityXY : public PatternKnotHolderEntity {
+public:
+    PatternKnotHolderEntityXY(bool fill) : PatternKnotHolderEntity(fill) {}
+    Geom::Point knot_get() const override;
+    void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) override;
+};
+
+class PatternKnotHolderEntityAngle : public PatternKnotHolderEntity {
+public:
+    PatternKnotHolderEntityAngle(bool fill) : PatternKnotHolderEntity(fill) {}
+    Geom::Point knot_get() const override;
+    void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) override;
+};
+
+class PatternKnotHolderEntityScale : public PatternKnotHolderEntity {
+public:
+    PatternKnotHolderEntityScale(bool fill) : PatternKnotHolderEntity(fill) {}
+    Geom::Point knot_get() const override;
+    void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) override;
+};
+
+/* Hatch manipulation */
+class HatchKnotHolderEntity : public KnotHolderEntity {
+  public:
+    HatchKnotHolderEntity(bool fill)
+        : KnotHolderEntity()
+        , _fill(fill)
+    {
+    }
+    bool knot_missing() const override;
+    void knot_ungrabbed(Geom::Point const &p, Geom::Point const &origin, guint state) override{};
+
+  protected:
+    // true if the entity tracks fill, false for stroke
+    bool _fill;
+    SPHatch *_hatch() const;
+};
+
+class HatchKnotHolderEntityXY : public HatchKnotHolderEntity {
+  public:
+    HatchKnotHolderEntityXY(bool fill)
+        : HatchKnotHolderEntity(fill)
+    {
+    }
+    Geom::Point knot_get() const override;
+    void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) override;
+};
+
+class HatchKnotHolderEntityAngle : public HatchKnotHolderEntity {
+  public:
+    HatchKnotHolderEntityAngle(bool fill)
+        : HatchKnotHolderEntity(fill)
+    {
+    }
+    Geom::Point knot_get() const override;
+    void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) override;
+};
+
+class HatchKnotHolderEntityScale : public HatchKnotHolderEntity {
+  public:
+    HatchKnotHolderEntityScale(bool fill)
+        : HatchKnotHolderEntity(fill)
+    {
+    }
+    Geom::Point knot_get() const override;
+    void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) override;
+};
+
+
+/* Filter manipulation */
+class FilterKnotHolderEntity : public KnotHolderEntity {
+  public:
+    FilterKnotHolderEntity(bool topleft) : KnotHolderEntity(), _topleft(topleft) {}
+    Geom::Point knot_get() const override;
+    void knot_ungrabbed(Geom::Point const &p, Geom::Point const &origin, guint state) override {};
+    void knot_set(Geom::Point const &p, Geom::Point const &origin, unsigned int state) override;
+private:
+    bool _topleft; // true for topleft point, false for bottomright
+};
+
+#endif /* !SEEN_KNOT_HOLDER_ENTITY_H */
+
+/*
+  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 :
diff --git a/src/ui/knot/knot-holder.cpp b/src/ui/knot/knot-holder.cpp
new file mode 100644
index 0000000..a743168
--- /dev/null
+++ b/src/ui/knot/knot-holder.cpp
@@ -0,0 +1,455 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Container for SPKnot visual handles.
+ *
+ * Authors:
+ *   Mitsuru Oka <oka326@parkcity.ne.jp>
+ *   bulia byak <buliabyak@users.sf.net>
+ *   Maximilian Albert <maximilian.albert@gmail.com>
+ *   Abhishek Sharma
+ *   Jon A. Cruz <jon@joncruz.org>
+ *
+ * Copyright (C) 2001-2008 authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include "knot-holder.h"
+
+#include "desktop.h"
+#include "document-undo.h"
+#include "document.h"
+#include "knot-holder-entity.h"
+#include "knot.h"
+
+#include "live_effects/effect.h"
+#include "live_effects/lpeobject.h"
+
+#include "object/box3d.h"
+#include "object/sp-ellipse.h"
+#include "object/sp-hatch.h"
+#include "object/sp-offset.h"
+#include "object/sp-pattern.h"
+#include "object/sp-rect.h"
+#include "object/sp-shape.h"
+#include "object/sp-spiral.h"
+#include "object/sp-star.h"
+#include "object/sp-marker.h"
+#include "style.h"
+
+#include "ui/icon-names.h"
+#include "ui/shape-editor.h"
+#include "ui/tools/arc-tool.h"
+#include "ui/tools/node-tool.h"
+#include "ui/tools/rect-tool.h"
+#include "ui/tools/spiral-tool.h"
+#include "ui/tools/tweak-tool.h"
+
+#include "display/control/snap-indicator.h"
+
+// TODO due to internal breakage in glibmm headers, this must be last:
+#include <glibmm/i18n.h>
+
+using Inkscape::DocumentUndo;
+
+class SPDesktop;
+
+KnotHolder::KnotHolder(SPDesktop *desktop, SPItem *item, SPKnotHolderReleasedFunc relhandler) :
+    desktop(desktop),
+    item(item),
+    //XML Tree being used directly for item->getRepr() while it shouldn't be...
+    repr(item ? item->getRepr() : nullptr),
+    entity(),
+    released(relhandler),
+    local_change(FALSE),
+    dragging(false),
+    _edit_transform(Geom::identity())
+{
+    if (!desktop || !item) {
+        g_print ("Error! Throw an exception, please!\n");
+    }
+
+    sp_object_ref(item);
+}
+
+KnotHolder::~KnotHolder() {
+    sp_object_unref(item);
+
+    for (auto & i : entity) {
+        delete i;
+    }
+    entity.clear(); // is this necessary?
+}
+
+void
+KnotHolder::setEditTransform(Geom::Affine edit_transform)
+{
+    _edit_transform = edit_transform;
+}
+
+void KnotHolder::update_knots()
+{
+    for (auto e = entity.begin(); e != entity.end(); ) {
+        // check if pattern was removed without deleting the knot
+        if ((*e)->knot_missing()) {
+            delete (*e);
+            e = entity.erase(e);
+        } else {
+            (*e)->update_knot();
+            ++e;
+        }
+    }
+}
+
+/**
+ * Returns true if at least one of the KnotHolderEntities has the mouse hovering above it.
+ */
+bool KnotHolder::knot_mouseover() const {
+    for (auto i : entity) {
+        const SPKnot *knot = i->knot;
+
+        if (knot && knot->is_mouseover()) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+/**
+ * Returns true if at least one of the KnotHolderEntities is selected
+ */
+bool KnotHolder::knot_selected() const {
+    for (auto i : entity) {
+        const SPKnot *knot = i->knot;
+
+        if (knot && knot->is_selected()) {
+            return true;
+        }
+    }
+    return false;
+}
+
+void
+KnotHolder::knot_mousedown_handler(SPKnot *knot, guint state)
+{
+    if (!(state & GDK_SHIFT_MASK)) {
+        unselect_knots();
+    }
+    for(auto e : this->entity) {
+        if (!(state & GDK_SHIFT_MASK)) {
+            e->knot->selectKnot(false);
+        }
+        if (e->knot == knot) {
+            if (!(e->knot->is_selected()) || !(state & GDK_SHIFT_MASK)){
+                e->knot->selectKnot(true);
+            } else {
+                e->knot->selectKnot(false);
+            }
+        }
+    }
+}
+
+void
+KnotHolder::knot_clicked_handler(SPKnot *knot, guint state)
+{
+    SPItem *saved_item = this->item;
+
+    for(auto e : this->entity) {
+        if (e->knot == knot)
+            // no need to test whether knot_click exists since it's virtual now
+            e->knot_click(state);
+    }
+
+    {
+        SPShape *savedShape = dynamic_cast<SPShape *>(saved_item);
+        if (savedShape) {
+            savedShape->set_shape();
+        }
+    }
+
+    this->update_knots();
+
+    Glib::ustring icon_name;
+
+    // TODO extract duplicated blocks;
+    if (dynamic_cast<SPRect *>(saved_item)) {
+        icon_name = INKSCAPE_ICON("draw-rectangle");
+    } else if (dynamic_cast<SPBox3D *>(saved_item)) {
+        icon_name = INKSCAPE_ICON("draw-cuboid");
+    } else if (dynamic_cast<SPGenericEllipse *>(saved_item)) {
+        icon_name = INKSCAPE_ICON("draw-ellipse");
+    } else if (dynamic_cast<SPStar *>(saved_item)) {
+        icon_name = INKSCAPE_ICON("draw-polygon-star");
+    } else if (dynamic_cast<SPSpiral *>(saved_item)) {
+        icon_name = INKSCAPE_ICON("draw-spiral");
+    } else if (dynamic_cast<SPMarker *>(saved_item)) {
+        icon_name = INKSCAPE_ICON("tool-pointer");
+    } else {
+        SPOffset *offset = dynamic_cast<SPOffset *>(saved_item);
+        if (offset) {
+            if (offset->sourceHref) {
+                icon_name = INKSCAPE_ICON("path-offset-linked");
+            } else {
+                icon_name = INKSCAPE_ICON("path-offset-dynamic");
+            }
+        }
+    }
+
+    // for drag, this is done by ungrabbed_handler, but for click we must do it here
+
+    if (saved_item) { //increasingly aggressive sanity checks
+       if (saved_item->document) {
+           DocumentUndo::done(saved_item->document, _("Change handle"), icon_name);
+       }
+    } // else { abort(); }
+}
+
+void
+KnotHolder::transform_selected(Geom::Affine transform){
+    for (auto & i : entity) {
+        SPKnot *knot = i->knot;
+        if (knot->is_selected()) {
+            knot_moved_handler(knot, knot->pos * transform , 0);
+            knot->selectKnot(true);
+        }
+    }
+}
+
+void
+KnotHolder::unselect_knots(){
+    Inkscape::UI::Tools::NodeTool *nt = dynamic_cast<Inkscape::UI::Tools::NodeTool*>(desktop->event_context);
+    if (nt) {
+        for (auto &_shape_editor : nt->_shape_editors) {
+            Inkscape::UI::ShapeEditor *shape_editor = _shape_editor.second.get();
+            if (shape_editor && shape_editor->has_knotholder()) {
+                KnotHolder * knotholder = shape_editor->knotholder;
+                if (knotholder) {
+                    for (auto e : knotholder->entity) {
+                        if (e->knot->is_selected()) {
+                            e->knot->selectKnot(false);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+void
+KnotHolder::knot_moved_handler(SPKnot *knot, Geom::Point const &p, guint state)
+{
+    if (this->dragging == false) {
+    	this->dragging = true;
+    }
+
+    // this was a local change and the knotholder does not need to be recreated:
+    this->local_change = TRUE;
+
+    for(auto e : this->entity) {
+        if (e->knot == knot) {
+            Geom::Point const q = p * item->i2dt_affine().inverse() * _edit_transform.inverse();
+            e->knot_set(q, e->knot->drag_origin * item->i2dt_affine().inverse() * _edit_transform.inverse(), state);
+            break;
+        }
+    }
+
+    SPShape *shape = dynamic_cast<SPShape *>(item);
+    if (shape) {
+        shape->set_shape();
+    }
+
+    this->update_knots();
+}
+
+void
+KnotHolder::knot_ungrabbed_handler(SPKnot *knot, guint state)
+{
+    this->dragging = false;
+    desktop->snapindicator->remove_snaptarget();
+
+    if (this->released) {
+        this->released(this->item);
+    } else {
+        // if a point is dragged while not selected, it should select itself,
+        // even if it was just unselected in the mousedown event handler.
+        if (!(knot->is_selected())) {
+            knot->selectKnot(true);
+        } else {
+            for(auto e : this->entity) {
+                if (e->knot == knot) {
+                    e->knot_ungrabbed(e->knot->position(), e->knot->drag_origin * item->i2dt_affine().inverse() * _edit_transform.inverse(), state);
+                    break;
+                }
+            }
+        }
+
+        SPObject *object = (SPObject *) this->item;
+
+        // Caution: this call involves a screen update, which may process events, and as a
+        // result the knotholder may be destructed. So, after the updateRepr, we cannot use any
+        // fields of this knotholder (such as this->item), but only values we have saved beforehand
+        // (such as object).
+        object->updateRepr();
+
+        /* do cleanup tasks (e.g., for LPE items write the parameter values
+         * that were changed by dragging the handle to SVG)
+         */
+        SPLPEItem *lpeItem = dynamic_cast<SPLPEItem *>(object);
+        if (lpeItem) {
+            // This writes all parameters to SVG. Is this sufficiently efficient or should we only
+            // write the ones that were changed?
+            Inkscape::LivePathEffect::Effect *lpe = lpeItem->getCurrentLPE();
+            if (lpe) {
+                LivePathEffectObject *lpeobj = lpe->getLPEObj();
+                lpeobj->updateRepr();
+            }
+        }
+
+        SPFilter *filter = (object->style) ? object->style->getFilter() : nullptr;
+        if (filter) {
+            filter->updateRepr();
+        }
+
+        Glib::ustring icon_name;
+
+        // TODO extract duplicated blocks;
+        if (dynamic_cast<SPRect *>(object)) {
+            icon_name = INKSCAPE_ICON("draw-rectangle");
+        } else if (dynamic_cast<SPBox3D *>(object)) {
+            icon_name = INKSCAPE_ICON("draw-cuboid");
+        } else if (dynamic_cast<SPGenericEllipse *>(object)) {
+            icon_name = INKSCAPE_ICON("draw-ellipse");
+        } else if (dynamic_cast<SPStar *>(object)) {
+            icon_name = INKSCAPE_ICON("draw-polygon-star");
+        } else if (dynamic_cast<SPSpiral *>(object)) {
+            icon_name = INKSCAPE_ICON("draw-spiral");
+        } else if (dynamic_cast<SPMarker *>(object)) {
+            icon_name = INKSCAPE_ICON("tool-pointer");
+        } else {
+            SPOffset *offset = dynamic_cast<SPOffset *>(object);
+            if (offset) {
+                if (offset->sourceHref) {
+                    icon_name = INKSCAPE_ICON("path-offset-linked");
+                } else {
+                    icon_name = INKSCAPE_ICON("path-offset-dynamic");
+                }
+            }
+        }
+        DocumentUndo::done(object->document, _("Move handle"), icon_name);
+    }
+}
+
+void KnotHolder::add(KnotHolderEntity *e)
+{
+    // g_message("Adding a knot at %p", e);
+    entity.push_back(e);
+}
+
+void KnotHolder::add_pattern_knotholder()
+{
+    if ((item->style->fill.isPaintserver()) && dynamic_cast<SPPattern *>(item->style->getFillPaintServer())) {
+        PatternKnotHolderEntityXY *entity_xy = new PatternKnotHolderEntityXY(true);
+        PatternKnotHolderEntityAngle *entity_angle = new PatternKnotHolderEntityAngle(true);
+        PatternKnotHolderEntityScale *entity_scale = new PatternKnotHolderEntityScale(true);
+        entity_xy->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_POINT, "Pattern:Fill:xy",
+                          // TRANSLATORS: This refers to the pattern that's inside the object
+                          _("<b>Move</b> the pattern fill inside the object"));
+
+        entity_scale->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_SIZER, "Pattern:Fill:scale",
+                             _("<b>Scale</b> the pattern fill; uniformly if with <b>Ctrl</b>"));
+
+        entity_angle->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_ROTATE, "Pattern:Fill:angle",
+                             _("<b>Rotate</b> the pattern fill; with <b>Ctrl</b> to snap angle"));
+
+        entity.push_back(entity_xy);
+        entity.push_back(entity_angle);
+        entity.push_back(entity_scale);
+    }
+
+    if ((item->style->stroke.isPaintserver()) && dynamic_cast<SPPattern *>(item->style->getStrokePaintServer())) {
+        PatternKnotHolderEntityXY *entity_xy = new PatternKnotHolderEntityXY(false);
+        PatternKnotHolderEntityAngle *entity_angle = new PatternKnotHolderEntityAngle(false);
+        PatternKnotHolderEntityScale *entity_scale = new PatternKnotHolderEntityScale(false);
+        entity_xy->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_POINT, "Pattern:Stroke:xy",
+                          // TRANSLATORS: This refers to the pattern that's inside the object
+                          _("<b>Move</b> the stroke's pattern inside the object"));
+
+        entity_scale->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_SIZER, "Pattern:Stroke:scale",
+                             _("<b>Scale</b> the stroke's pattern; uniformly if with <b>Ctrl</b>"));
+
+        entity_angle->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_ROTATE, "Pattern:Stroke:angle",
+                             _("<b>Rotate</b> the stroke's pattern; with <b>Ctrl</b> to snap angle"));
+
+        entity.push_back(entity_xy);
+        entity.push_back(entity_angle);
+        entity.push_back(entity_scale);
+    }
+}
+
+void KnotHolder::add_hatch_knotholder()
+{
+    if ((item->style->fill.isPaintserver()) && dynamic_cast<SPHatch *>(item->style->getFillPaintServer())) {
+        HatchKnotHolderEntityXY *entity_xy = new HatchKnotHolderEntityXY(true);
+        HatchKnotHolderEntityAngle *entity_angle = new HatchKnotHolderEntityAngle(true);
+        HatchKnotHolderEntityScale *entity_scale = new HatchKnotHolderEntityScale(true);
+        entity_xy->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_POINT, "Hatch:Fill:xy",
+                          // TRANSLATORS: This refers to the hatch that's inside the object
+                          _("<b>Move</b> the hatch fill inside the object"));
+
+        entity_scale->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_SIZER, "Hatch:Fill:scale",
+                             _("<b>Scale</b> the hatch fill; uniformly if with <b>Ctrl</b>"));
+
+        entity_angle->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_ROTATE, "Hatch:Fill:angle",
+                             _("<b>Rotate</b> the hatch fill; with <b>Ctrl</b> to snap angle"));
+
+        entity.push_back(entity_xy);
+        entity.push_back(entity_angle);
+        entity.push_back(entity_scale);
+    }
+
+    if ((item->style->stroke.isPaintserver()) && dynamic_cast<SPHatch *>(item->style->getStrokePaintServer())) {
+        HatchKnotHolderEntityXY *entity_xy = new HatchKnotHolderEntityXY(false);
+        HatchKnotHolderEntityAngle *entity_angle = new HatchKnotHolderEntityAngle(false);
+        HatchKnotHolderEntityScale *entity_scale = new HatchKnotHolderEntityScale(false);
+        entity_xy->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_POINT, "Hatch:Stroke:xy",
+                          // TRANSLATORS: This refers to the pattern that's inside the object
+                          _("<b>Move</b> the hatch stroke inside the object"));
+
+        entity_scale->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_SIZER, "Hatch:Stroke:scale",
+                             _("<b>Scale</b> the hatch stroke; uniformly if with <b>Ctrl</b>"));
+
+        entity_angle->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_ROTATE, "Hatch:Stroke:angle",
+                             _("<b>Rotate</b> the hatch stroke; with <b>Ctrl</b> to snap angle"));
+
+        entity.push_back(entity_xy);
+        entity.push_back(entity_angle);
+        entity.push_back(entity_scale);
+    }
+}
+
+void KnotHolder::add_filter_knotholder() {
+    if (!item->style->filter.set || !item->style->getFilter() || item->style->getFilter()->auto_region) {
+        return;
+    }
+
+    FilterKnotHolderEntity *entity_tl = new FilterKnotHolderEntity(true);
+    FilterKnotHolderEntity *entity_br = new FilterKnotHolderEntity(false);
+    entity_tl->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_POINT, "Filter:TopLeft",
+                      _("<b>Resize</b> the filter effect region"));
+    entity_br->create(desktop, item, this, Inkscape::CANVAS_ITEM_CTRL_TYPE_POINT, "Filter:BottomRight",
+                      _("<b>Resize</b> the filter effect region"));
+    entity.push_back(entity_tl);
+    entity.push_back(entity_br);
+}
+
+/*
+  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 :
diff --git a/src/ui/knot/knot-holder.h b/src/ui/knot/knot-holder.h
new file mode 100644
index 0000000..95c9915
--- /dev/null
+++ b/src/ui/knot/knot-holder.h
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#ifndef SEEN_SP_KNOTHOLDER_H
+#define SEEN_SP_KNOTHOLDER_H
+
+/*
+ * KnotHolder - Hold SPKnot list and manage signals
+ *
+ * Author:
+ *   Mitsuru Oka <oka326@parkcity.ne.jp>
+ *   Maximilian Albert <maximilian.albert@gmail.com>
+ *
+ * Copyright (C) 1999-2001 Lauris Kaplinski
+ * Copyright (C) 2000-2001 Ximian, Inc.
+ * Copyright (C) 2001 Mitsuru Oka
+ * Copyright (C) 2008 Maximilian Albert
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ *
+ */
+
+#include <2geom/forward.h>
+#include <2geom/affine.h>
+#include <list>
+#include <sigc++/connection.h>
+
+namespace Inkscape {
+namespace UI {
+class ShapeEditor;
+}
+namespace XML {
+class Node;
+}
+namespace LivePathEffect {
+class PowerStrokePointArrayParamKnotHolderEntity;
+class NodeSatelliteArrayParam;
+class FilletChamferKnotHolderEntity;
+}
+}
+
+class KnotHolderEntity;
+class SPItem;
+class SPDesktop;
+class SPKnot;
+
+/* fixme: Think how to make callbacks most sensitive (Lauris) */
+typedef void (* SPKnotHolderReleasedFunc) (SPItem *item);
+
+class KnotHolder {
+public:
+    KnotHolder(SPDesktop *desktop, SPItem *item, SPKnotHolderReleasedFunc relhandler);
+    virtual ~KnotHolder();
+
+    KnotHolder() = delete; // declared but not defined
+
+    void update_knots();
+    void unselect_knots();
+    void knot_mousedown_handler(SPKnot *knot, unsigned int state);
+    void knot_moved_handler(SPKnot *knot, Geom::Point const &p, unsigned int state);
+    void knot_clicked_handler(SPKnot *knot, unsigned int state);
+    void knot_ungrabbed_handler(SPKnot *knot, unsigned int state);
+    void transform_selected(Geom::Affine transform);
+    void add(KnotHolderEntity *e);
+
+    void add_pattern_knotholder();
+    void add_hatch_knotholder();
+    void add_filter_knotholder();
+
+    void setEditTransform(Geom::Affine edit_transform);
+    Geom::Affine getEditTransform() const { return _edit_transform; }
+
+    bool knot_selected() const;
+    bool knot_mouseover() const;
+
+    SPDesktop *getDesktop() { return desktop; }
+    SPItem *getItem() { return item; }
+    bool is_dragging() const { return dragging; }
+
+    friend class Inkscape::UI::ShapeEditor; // FIXME why?
+    friend class Inkscape::LivePathEffect::NodeSatelliteArrayParam;                    // why?
+    friend class Inkscape::LivePathEffect::PowerStrokePointArrayParamKnotHolderEntity; // why?
+    friend class Inkscape::LivePathEffect::FilletChamferKnotHolderEntity; // why?
+
+protected:
+
+    SPDesktop *desktop;
+    SPItem *item; // TODO: Remove this and keep the actual item (e.g., SPRect etc.) in the item-specific knotholders
+    Inkscape::XML::Node *repr; ///< repr of the item, for setting and releasing listeners.
+    std::list<KnotHolderEntity *> entity;
+
+    SPKnotHolderReleasedFunc released;
+
+    bool local_change; ///< if true, no need to recreate knotholder if repr was changed.
+
+    bool dragging;
+
+    Geom::Affine _edit_transform;
+};
+
+/**
+void knot_clicked_handler(SPKnot *knot, guint state, gpointer data);
+void knot_moved_handler(SPKnot *knot, Geom::Point const *p, guint state, gpointer data);
+void knot_ungrabbed_handler(SPKnot *knot, unsigned int state, KnotHolder *kh);
+**/
+
+#endif // SEEN_SP_KNOTHOLDER_H
+
+/*
+  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 :
diff --git a/src/ui/knot/knot-ptr.cpp b/src/ui/knot/knot-ptr.cpp
new file mode 100644
index 0000000..8e275ac
--- /dev/null
+++ b/src/ui/knot/knot-ptr.cpp
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * TODO: insert short description here
+ *//*
+ * Authors: see git history
+ *
+ * Copyright (C) 2018 Authors
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+#include <algorithm>
+#include <glib.h>
+#include <list>
+#include "knot-ptr.h"
+
+static std::list<void*> deleted_knots;
+
+void knot_deleted_callback(void* knot) {
+    if (std::find(deleted_knots.begin(), deleted_knots.end(), knot) == deleted_knots.end()) {
+        deleted_knots.push_back(knot);
+    }
+}
+
+void knot_created_callback(void* knot) {
+    std::list<void*>::iterator it = std::find(deleted_knots.begin(), deleted_knots.end(), knot);
+    if (it != deleted_knots.end()) {
+        deleted_knots.erase(it);
+    }
+}
+
+void check_if_knot_deleted(void* knot) {
+    if (std::find(deleted_knots.begin(), deleted_knots.end(), knot) != deleted_knots.end()) {
+        g_warning("Accessed knot after it was freed at %p", knot);
+    }
+}
diff --git a/src/ui/knot/knot-ptr.h b/src/ui/knot/knot-ptr.h
new file mode 100644
index 0000000..5141822
--- /dev/null
+++ b/src/ui/knot/knot-ptr.h
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * TODO: insert short description here
+ *//*
+ * Authors: see git history
+ *
+ * Copyright (C) 2014 Authors
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+#ifndef KNOT_PTR_DETECTOR
+#define KNOT_PTR_DETECTOR
+
+void knot_deleted_callback(void* knot);
+void knot_created_callback(void* knot);
+void check_if_knot_deleted(void* knot);
+
+#endif
diff --git a/src/ui/knot/knot.cpp b/src/ui/knot/knot.cpp
new file mode 100644
index 0000000..d0b2e0c
--- /dev/null
+++ b/src/ui/knot/knot.cpp
@@ -0,0 +1,520 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * SPKnot implementation
+ *
+ * Authors:
+ *   Lauris Kaplinski <lauris@kaplinski.com>
+ *   bulia byak <buliabyak@users.sf.net>
+ *   Abhishek Sharma
+ *
+ * Copyright (C) 1999-2005 authors
+ * Copyright (C) 2001-2002 Ximian, Inc.
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#ifdef HAVE_CONFIG_H
+#endif
+#include <gdk/gdkkeysyms.h>
+#include <glibmm/i18n.h>
+
+#include "desktop.h"
+
+#include "knot.h"
+#include "knot-ptr.h"
+#include "document.h"
+#include "document-undo.h"
+#include "message-stack.h"
+#include "message-context.h"
+
+#include "display/control/canvas-item-ctrl.h"
+#include "ui/tools/tool-base.h"
+#include "ui/tools/node-tool.h"
+#include "ui/widget/canvas.h"
+
+using Inkscape::DocumentUndo;
+
+Gdk::EventMask KNOT_EVENT_MASK (
+    Gdk::BUTTON_PRESS_MASK   |
+    Gdk::BUTTON_RELEASE_MASK |
+    Gdk::POINTER_MOTION_MASK |
+    Gdk::KEY_PRESS_MASK      |
+    Gdk::KEY_RELEASE_MASK);
+
+const gchar *nograbenv = getenv("INKSCAPE_NO_GRAB");
+static bool nograb = (nograbenv && *nograbenv && (*nograbenv != '0'));
+
+
+void knot_ref(SPKnot* knot) {
+    knot->ref_count++;
+}
+
+void knot_unref(SPKnot* knot) {
+    if (--knot->ref_count < 1) {
+        delete knot;
+    }
+}
+
+SPKnot::SPKnot(SPDesktop *desktop, gchar const *tip, Inkscape::CanvasItemCtrlType type, Glib::ustring const & name)
+    : desktop(desktop)
+    , ref_count(1)
+{
+    if (tip) {
+        this->tip = g_strdup (tip);
+    }
+
+    fill[SP_KNOT_STATE_NORMAL]    = 0xffffff00;
+    fill[SP_KNOT_STATE_MOUSEOVER] = 0xff0000ff;
+    fill[SP_KNOT_STATE_DRAGGING]  = 0xff0000ff;
+    fill[SP_KNOT_STATE_SELECTED]  = 0x0000ffff;
+
+    stroke[SP_KNOT_STATE_NORMAL]    = 0x01000000;
+    stroke[SP_KNOT_STATE_MOUSEOVER] = 0x01000000;
+    stroke[SP_KNOT_STATE_DRAGGING]  = 0x01000000;
+    stroke[SP_KNOT_STATE_SELECTED]  = 0x01000000;
+
+    image[SP_KNOT_STATE_NORMAL] = nullptr;
+    image[SP_KNOT_STATE_MOUSEOVER] = nullptr;
+    image[SP_KNOT_STATE_DRAGGING] = nullptr;
+    image[SP_KNOT_STATE_SELECTED] = nullptr;
+
+    ctrl = new Inkscape::CanvasItemCtrl(desktop->getCanvasControls(), type); // Shape, mode set
+    Glib::ustring ctrl_name = "CanvasItemCtrl:Knot: " + name;
+    ctrl->set_name(ctrl_name);
+
+    // Are these needed?
+    ctrl->set_fill(0xffffff00);
+    ctrl->set_stroke(0x01000000);
+
+    _event_connection = ctrl->connect_event(sigc::mem_fun(this, &SPKnot::eventHandler));
+
+    knot_created_callback(this);
+}
+
+SPKnot::~SPKnot() {
+    auto display = gdk_display_get_default();
+    auto seat    = gdk_display_get_default_seat(display);
+    auto device  = gdk_seat_get_pointer(seat);
+
+    if ((this->flags & SP_KNOT_GRABBED) && gdk_display_device_is_grabbed(display, device)) {
+        // This happens e.g. when deleting a node in node tool while dragging it
+        gdk_seat_ungrab(seat);
+    }
+
+    if (ctrl) {
+        delete ctrl;
+    }
+
+    if (this->tip) {
+        g_free(this->tip);
+        this->tip = nullptr;
+    }
+
+    // FIXME: cannot snap to destroyed knot (lp:1309050)
+    // this->desktop->event_context->discard_delayed_snap_event();
+    knot_deleted_callback(this);
+}
+
+void SPKnot::startDragging(Geom::Point const &p, gint x, gint y, guint32 etime) {
+    // save drag origin
+    xp = x;
+    yp = y;
+    within_tolerance = true;
+
+    this->grabbed_rel_pos = p - this->pos;
+    this->drag_origin = this->pos;
+
+    if (!nograb && ctrl) {
+        ctrl->grab(KNOT_EVENT_MASK, _cursors[SP_KNOT_STATE_DRAGGING]);
+    }
+    this->setFlag(SP_KNOT_GRABBED, true);
+
+    grabbed = true;
+}
+
+void SPKnot::selectKnot(bool select){
+    setFlag(SP_KNOT_SELECTED, select);
+}
+
+bool SPKnot::eventHandler(GdkEvent *event)
+{
+    /* Run client universal event handler, if present */
+    bool consumed = event_signal.emit(this, event);
+    if (consumed) {
+        return true;
+    }
+
+    bool key_press_event_unconsumed = false;
+
+    ref_count++;
+
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    tolerance = prefs->getIntLimited("/options/dragtolerance/value", 0, 0, 100);
+
+    switch (event->type) {
+    case GDK_2BUTTON_PRESS:
+        if (event->button.button == 1) {
+            doubleclicked_signal.emit(this, event->button.state);
+
+            grabbed = false;
+            moved = false;
+            consumed = true;
+        }
+        break;
+    case GDK_BUTTON_PRESS:
+        if ((event->button.button == 1) && desktop && desktop->event_context && !desktop->event_context->is_space_panning()) {
+            Geom::Point const p = desktop->w2d(Geom::Point(event->button.x, event->button.y));
+            startDragging(p, (gint) event->button.x, (gint) event->button.y, event->button.time);
+            mousedown_signal.emit(this, event->button.state);
+            consumed = true;
+        }
+        break;
+    case GDK_BUTTON_RELEASE:
+        if (event->button.button == 1    &&
+            desktop                &&
+            desktop->event_context &&
+            !desktop->event_context->is_space_panning()) {
+
+            // If we have any pending snap event, then invoke it now
+            if (desktop->event_context->_delayed_snap_event) {
+                sp_event_context_snap_watchdog_callback(desktop->event_context->_delayed_snap_event);
+            }
+            desktop->event_context->discard_delayed_snap_event();
+            pressure = 0;
+
+            if (transform_escaped) {
+                transform_escaped = false;
+                consumed = true;
+            } else {
+                setFlag(SP_KNOT_GRABBED, false);
+
+                if (!nograb && ctrl) {
+                    ctrl->ungrab();
+                }
+
+                if (moved) {
+                    setFlag(SP_KNOT_DRAGGING, false);
+                    ungrabbed_signal.emit(this, event->button.state);
+                } else {
+                    click_signal.emit(this, event->button.state);
+                }
+
+                grabbed = false;
+                moved = false;
+                consumed = true;
+            }
+        }
+        Inkscape::UI::Tools::sp_update_helperpath(desktop);
+        break;
+
+    case GDK_MOTION_NOTIFY:
+
+        if (!(event->motion.state & GDK_BUTTON1_MASK) && flags & SP_KNOT_DRAGGING) {
+            pressure = 0;
+
+            if (transform_escaped) {
+                transform_escaped = false;
+                consumed = true;
+            } else {
+                setFlag(SP_KNOT_GRABBED, false);
+
+                if (!nograb && ctrl) {
+                    ctrl->ungrab();
+                }
+
+                if (moved) {
+                    setFlag(SP_KNOT_DRAGGING, false);
+                    ungrabbed_signal.emit(this, event->motion.state);
+                } else {
+                    click_signal.emit(this, event->motion.state);
+                }
+
+                grabbed = false;
+                moved = false;
+                consumed = true;
+                Inkscape::UI::Tools::sp_update_helperpath(desktop);
+            }
+        } else if (grabbed && desktop && desktop->event_context &&
+                   !desktop->event_context->is_space_panning()) {
+            consumed = true;
+
+            if ( within_tolerance
+                 && ( abs( (gint) event->motion.x - xp ) < tolerance )
+                 && ( abs( (gint) event->motion.y - yp ) < tolerance ) ) {
+                break; // do not drag if we're within tolerance from origin
+            }
+
+            // Once the user has moved farther than tolerance from the original location
+            // (indicating they intend to move the object, not click), then always process the
+            // motion notify coordinates as given (no snapping back to origin)
+            within_tolerance = false;
+
+            if (gdk_event_get_axis (event, GDK_AXIS_PRESSURE, &pressure)) {
+                pressure = CLAMP (pressure, 0, 1);
+            } else {
+                pressure = 0.5;
+            }
+
+            if (!moved) {
+                setFlag(SP_KNOT_DRAGGING, true);
+                grabbed_signal.emit(this, event->button.state);
+            }
+
+            sp_event_context_snap_delay_handler(desktop->event_context, nullptr, this, (GdkEventMotion *)event, Inkscape::UI::Tools::DelayedSnapEvent::KNOT_HANDLER);
+            sp_knot_handler_request_position(event, this);
+            moved = true;
+        }
+        break;
+    case GDK_ENTER_NOTIFY:
+        setFlag(SP_KNOT_MOUSEOVER, true);
+        setFlag(SP_KNOT_GRABBED, false);
+
+        if (tip && desktop && desktop->event_context) {
+            desktop->event_context->defaultMessageContext()->set(Inkscape::NORMAL_MESSAGE, tip);
+        }
+        desktop->event_context->use_cursor(_cursors[SP_KNOT_STATE_MOUSEOVER]);
+
+        grabbed = false;
+        moved = false;
+        consumed = true;
+        break;
+    case GDK_LEAVE_NOTIFY:
+        setFlag(SP_KNOT_MOUSEOVER, false);
+        setFlag(SP_KNOT_GRABBED, false);
+
+        if (tip && desktop && desktop->event_context) {
+            desktop->event_context->defaultMessageContext()->clear();
+        }
+        desktop->event_context->use_cursor(_cursors[SP_KNOT_STATE_NORMAL]);
+
+        grabbed = false;
+        moved = false;
+        consumed = true;
+        break;
+    case GDK_KEY_PRESS: // keybindings for knot
+        switch (Inkscape::UI::Tools::get_latin_keyval(&event->key)) {
+            case GDK_KEY_Escape:
+                setFlag(SP_KNOT_GRABBED, false);
+
+                if (!nograb && ctrl) {
+                    ctrl->ungrab();
+                }
+
+                if (moved) {
+                    setFlag(SP_KNOT_DRAGGING, false);
+
+                    ungrabbed_signal.emit(this, event->button.state);
+
+                    DocumentUndo::undo(desktop->getDocument());
+                    desktop->messageStack()->flash(Inkscape::NORMAL_MESSAGE, _("Node or handle drag canceled."));
+                    transform_escaped = true;
+                    consumed = true;
+                }
+
+                grabbed = false;
+                moved = false;
+
+                desktop->event_context->discard_delayed_snap_event();
+                break;
+            default:
+                consumed = false;
+                key_press_event_unconsumed = true;
+                break;
+        }
+        break;
+    default:
+        break;
+    }
+
+    knot_unref(this);
+
+    if (key_press_event_unconsumed) {
+        return false; // e.g. in case "%" was pressed to toggle snapping, or Q for quick zoom (while dragging a handle)
+    } else {
+        return  consumed || grabbed;
+    }
+}
+
+void sp_knot_handler_request_position(GdkEvent *event, SPKnot *knot) {
+    Geom::Point const motion_w(event->motion.x, event->motion.y);
+    Geom::Point const motion_dt = knot->desktop->w2d(motion_w);
+    Geom::Point p = motion_dt - knot->grabbed_rel_pos;
+
+    knot->requestPosition(p, event->motion.state);
+    knot->desktop->scroll_to_point (motion_dt);
+    knot->desktop->set_coordinate_status(knot->pos); // display the coordinate of knot, not cursor - they may be different!
+
+    if (event->motion.state & GDK_BUTTON1_MASK) {
+        knot->desktop->canvas->gobble_motion_events(GDK_BUTTON1_MASK);
+    }
+}
+
+void SPKnot::show() {
+    this->setFlag(SP_KNOT_VISIBLE, true);
+}
+
+void SPKnot::hide() {
+    this->setFlag(SP_KNOT_VISIBLE, false);
+}
+
+void SPKnot::requestPosition(Geom::Point const &p, guint state) {
+    bool done = this->request_signal.emit(this, &const_cast<Geom::Point&>(p), state);
+
+    /* If user did not complete, we simply move knot to new position */
+    if (!done) {
+        this->setPosition(p, state);
+    }
+}
+
+void SPKnot::setPosition(Geom::Point const &p, guint state) {
+    this->pos = p;
+
+    if (ctrl) {
+        ctrl->set_position(p);
+    }
+
+    this->moved_signal.emit(this, p, state);
+}
+
+void SPKnot::moveto(Geom::Point const &p) {
+    this->pos = p;
+
+    if (ctrl) {
+        ctrl->set_position(p);
+    }
+}
+
+Geom::Point SPKnot::position() const {
+    return this->pos;
+}
+
+void SPKnot::setFlag(guint flag, bool set) {
+    if (set) {
+        this->flags |= flag;
+    } else {
+        this->flags &= ~flag;
+    }
+
+    switch (flag) {
+    case SP_KNOT_VISIBLE:
+            if (set) {
+                if (ctrl) {
+                    ctrl->show();
+                }
+            } else {
+                if (ctrl) {
+                    ctrl->hide();
+                }
+            }
+            break;
+    case SP_KNOT_MOUSEOVER:
+    case SP_KNOT_DRAGGING:
+    case SP_KNOT_SELECTED:
+            this->_setCtrlState();
+            break;
+    case SP_KNOT_GRABBED:
+            break;
+    default:
+            g_assert_not_reached();
+            break;
+    }
+}
+
+// TODO: Look at removing this and setting ctrl parameters directly.
+void SPKnot::updateCtrl() {
+
+    if (ctrl) {
+        if (shape_set) {
+            ctrl->set_shape(shape);
+        }
+        ctrl->set_mode(mode);
+        if (size_set) {
+            ctrl->set_size(size);
+        }
+        ctrl->set_angle(angle);
+        ctrl->set_anchor(anchor);
+        ctrl->set_pixbuf(static_cast<GdkPixbuf *>(pixbuf));
+    }
+
+    _setCtrlState();
+}
+
+void SPKnot::_setCtrlState() {
+    int state = SP_KNOT_STATE_NORMAL;
+
+    if (this->flags & SP_KNOT_DRAGGING) {
+        state = SP_KNOT_STATE_DRAGGING;
+    } else if (this->flags & SP_KNOT_MOUSEOVER) {
+        state = SP_KNOT_STATE_MOUSEOVER;
+    } else if (this->flags & SP_KNOT_SELECTED) {
+        state = SP_KNOT_STATE_SELECTED;
+    }
+    if (ctrl) {
+        ctrl->set_fill(fill[state]);
+        ctrl->set_stroke(stroke[state]);
+    }
+}
+
+
+void SPKnot::setSize(guint i) {
+    size = i;
+    size_set = true;
+}
+
+void SPKnot::setShape(Inkscape::CanvasItemCtrlShape s) {
+    shape = s;
+    shape_set = true;
+}
+
+void SPKnot::setAnchor(guint i) {
+    anchor = (SPAnchorType) i;
+}
+
+void SPKnot::setMode(Inkscape::CanvasItemCtrlMode m) {
+    mode = m;
+}
+
+void SPKnot::setPixbuf(gpointer p) {
+    pixbuf = p;
+}
+
+void SPKnot::setAngle(double i) {
+    angle = i;
+}
+
+void SPKnot::setFill(guint32 normal, guint32 mouseover, guint32 dragging, guint32 selected) {
+    fill[SP_KNOT_STATE_NORMAL] = normal;
+    fill[SP_KNOT_STATE_MOUSEOVER] = mouseover;
+    fill[SP_KNOT_STATE_DRAGGING] = dragging;
+    fill[SP_KNOT_STATE_SELECTED] = selected;
+}
+
+void SPKnot::setStroke(guint32 normal, guint32 mouseover, guint32 dragging, guint32 selected) {
+    stroke[SP_KNOT_STATE_NORMAL] = normal;
+    stroke[SP_KNOT_STATE_MOUSEOVER] = mouseover;
+    stroke[SP_KNOT_STATE_DRAGGING] = dragging;
+    stroke[SP_KNOT_STATE_SELECTED] = selected;
+}
+
+void SPKnot::setImage(guchar* normal, guchar* mouseover, guchar* dragging, guchar* selected) {
+    image[SP_KNOT_STATE_NORMAL] = normal;
+    image[SP_KNOT_STATE_MOUSEOVER] = mouseover;
+    image[SP_KNOT_STATE_DRAGGING] = dragging;
+    image[SP_KNOT_STATE_SELECTED] = selected;
+}
+
+void SPKnot::setCursor(SPKnotStateType type, Glib::RefPtr<Gdk::Cursor> cursor)
+{
+    _cursors[type] = cursor;
+}
+
+/*
+  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 :
diff --git a/src/ui/knot/knot.h b/src/ui/knot/knot.h
new file mode 100644
index 0000000..59104e7
--- /dev/null
+++ b/src/ui/knot/knot.h
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#ifndef SEEN_SP_KNOT_H
+#define SEEN_SP_KNOT_H
+
+/** \file
+ * Declarations for SPKnot: Desktop-bound visual control object.
+ */
+/*
+ * Authors:
+ *   Lauris Kaplinski <lauris@kaplinski.com>
+ *
+ * Copyright (C) 1999-2002 authors
+ * Copyright (C) 2001-2002 Ximian, Inc.
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include <2geom/point.h>
+#include <sigc++/sigc++.h>
+#include <glibmm/ustring.h>
+#include <glibmm/refptr.h>
+#include <gdkmm/cursor.h>
+
+#include "knot-enums.h"
+#include "display/control/canvas-item-enums.h"
+#include "enums.h"
+
+class SPDesktop;
+class SPItem;
+
+typedef union _GdkEvent GdkEvent;
+typedef unsigned int guint32;
+
+#define SP_KNOT(obj) (dynamic_cast<SPKnot*>(static_cast<SPKnot*>(obj)))
+#define SP_IS_KNOT(obj) (dynamic_cast<const SPKnot*>(static_cast<const SPKnot*>(obj)) != NULL)
+
+namespace Inkscape {
+class CanvasItemCtrl;
+}
+
+/**
+ * Desktop-bound visual control object.
+ *
+ * A knot is a draggable object, with callbacks to change something by
+ * dragging it, visually represented by a canvas item (mostly square).
+ *
+ * See also KnotHolderEntity.
+ * See also ControlPoint (which does the same kind of things).
+ */
+class SPKnot {
+public:
+    SPKnot(SPDesktop *desktop, char const *tip, Inkscape::CanvasItemCtrlType type, Glib::ustring const & name = Glib::ustring("unknown"));
+    virtual ~SPKnot();
+
+    SPKnot(SPKnot const&) = delete;
+    SPKnot& operator=(SPKnot const&) = delete;
+
+    int ref_count; // FIXME encapsulation
+
+    SPDesktop *desktop  = nullptr;                  /**< Desktop we are on. */
+    Inkscape::CanvasItemCtrl *ctrl = nullptr;       /**< Our CanvasItemCtrl. */
+    SPItem *owner       = nullptr;                  /**< Optional Owner Item */
+    SPItem *sub_owner   = nullptr;                  /**< Optional SubOwner Item */
+    unsigned int flags  = SP_KNOT_VISIBLE;
+
+    unsigned int size   = 9;                        /**< Always square. Must be odd. */
+    bool size_set       = false;                    /**< Use default size unless explicitly set. */
+    double angle        = 0.0;                      /**< Angle of mesh handle. */
+    Geom::Point pos;                                /**< Our desktop coordinates. */
+    Geom::Point grabbed_rel_pos;                    /**< Grabbed relative position. */
+    Geom::Point drag_origin;                        /**< Origin of drag. */
+    SPAnchorType anchor = SP_ANCHOR_CENTER;         /**< Anchor. */
+
+    bool grabbed        = false;
+    bool moved          = false;
+    int  xp             = 0.0;                      /**< Where drag started */
+    int  yp             = 0.0;                      /**< Where drag started */
+    int  tolerance      = 0;
+    bool within_tolerance = false;
+    bool transform_escaped = false; // true iff resize or rotate was cancelled by esc.
+
+    Inkscape::CanvasItemCtrlShape shape = Inkscape::CANVAS_ITEM_CTRL_SHAPE_SQUARE;   /**< Shape type. */
+    bool shape_set      = false;                    /**< Use default shape unless explicitly set. */
+    Inkscape::CanvasItemCtrlMode mode = Inkscape::CANVAS_ITEM_CTRL_MODE_XOR;
+
+    guint32 fill[SP_KNOT_VISIBLE_STATES];
+    guint32 stroke[SP_KNOT_VISIBLE_STATES];
+    unsigned char *image[SP_KNOT_VISIBLE_STATES];
+    Glib::RefPtr<Gdk::Cursor> _cursors[SP_KNOT_VISIBLE_STATES];
+
+    void* pixbuf            = nullptr;
+    char *tip               = nullptr;
+
+    sigc::connection _event_connection;
+
+    double pressure         = 0.0;    /**< The tablet pen pressure when the knot is being dragged. */
+
+    // FIXME: signals should NOT need to emit the object they came from, the callee should
+    // be able to figure that out
+    sigc::signal<void, SPKnot *, unsigned int> click_signal;
+    sigc::signal<void, SPKnot*, unsigned int> doubleclicked_signal;
+    sigc::signal<void, SPKnot*, unsigned int> mousedown_signal;
+    sigc::signal<void, SPKnot*, unsigned int> grabbed_signal;
+    sigc::signal<void, SPKnot *, unsigned int> ungrabbed_signal;
+    sigc::signal<void, SPKnot *, Geom::Point const &, unsigned int> moved_signal;
+    sigc::signal<bool, SPKnot*, GdkEvent*> event_signal;
+
+    sigc::signal<bool, SPKnot*, Geom::Point*, unsigned int> request_signal;
+
+
+    //TODO: all the members above should eventualle become private, accessible via setters/getters
+    void setSize(unsigned int i);
+    void setShape(Inkscape::CanvasItemCtrlShape s);
+    void setAnchor(unsigned int i);
+    void setMode(Inkscape::CanvasItemCtrlMode m);
+    void setPixbuf(void* p);
+    void setAngle(double i);
+
+    void setFill(guint32 normal, guint32 mouseover, guint32 dragging, guint32 selected);
+    void setStroke(guint32 normal, guint32 mouseover, guint32 dragging, guint32 selected);
+    void setImage(unsigned char* normal, unsigned char* mouseover, unsigned char* dragging, unsigned char* selected);
+
+    void setCursor(SPKnotStateType type, Glib::RefPtr<Gdk::Cursor> cursor);
+
+    /**
+     * Show knot on its canvas.
+     */
+    void show();
+
+    /**
+     * Hide knot on its canvas.
+     */
+    void hide();
+
+    /**
+     * Set flag in knot, with side effects.
+     */
+    void setFlag(unsigned int flag, bool set);
+
+    /**
+     * Update knot's pixbuf and set its control state.
+     */
+    void updateCtrl();
+
+    /**
+     * Request or set new position for knot.
+     */
+    void requestPosition(Geom::Point const &pos, unsigned int state);
+
+    /**
+     * Update knot for dragging and tell canvas an item was grabbed.
+     */
+    void startDragging(Geom::Point const &p, int x, int y, guint32 etime);
+
+    /**
+     * Move knot to new position and emits "moved" signal.
+     */
+    void setPosition(Geom::Point const &p, unsigned int state);
+
+    /**
+     * Move knot to new position, without emitting a MOVED signal.
+     */
+    void moveto(Geom::Point const &p);
+    /**
+     * Select knot.
+     */
+    void selectKnot(bool select);
+
+    /**
+     * Returns position of knot.
+     */
+    Geom::Point position() const;
+
+    /**
+     * Event handler (from CanvasItem's).
+     */
+    bool eventHandler(GdkEvent *event);
+
+    bool is_visible()   const { return (flags & SP_KNOT_VISIBLE)   != 0; }
+    bool is_selected()  const { return (flags & SP_KNOT_SELECTED)  != 0; }
+    bool is_mouseover() const { return (flags & SP_KNOT_MOUSEOVER) != 0; }
+    bool is_dragging()  const { return (flags & SP_KNOT_DRAGGING)  != 0; }
+    bool is_grabbed()   const { return (flags & SP_KNOT_GRABBED)   != 0; }
+
+private:
+    /**
+     * Set knot control state (dragging/mouseover/normal).
+     */
+    void _setCtrlState();
+};
+
+void knot_ref(SPKnot* knot);
+void knot_unref(SPKnot* knot);
+
+void sp_knot_handler_request_position(GdkEvent *event, SPKnot *knot);
+
+#endif // SEEN_SP_KNOT_H
+
+/*
+  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 :