Adding upstream version 1.2.2.upstream/1.2.2upstream

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

1 files changed, 827 insertions, 0 deletions

diff --git a/src/ui/tool/transform-handle-set.cpp b/src/ui/tool/transform-handle-set.cpp
new file mode 100644
index 0000000..875429a
--- /dev/null
+++ b/src/ui/tool/transform-handle-set.cpp
@@ -0,0 +1,827 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * Affine transform handles component
+ */
+/* Authors:
+ *   Krzysztof Kosiński <tweenk.pl@gmail.com>
+ *   Jon A. Cruz <jon@joncruz.org>
+ *
+ * Copyright (C) 2009 Authors
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include <cmath>
+#include <algorithm>
+
+#include <glib/gi18n.h>
+
+#include <2geom/transforms.h>
+
+#include "control-point.h"
+#include "desktop.h"
+#include "pure-transform.h"
+#include "seltrans.h"
+#include "snap.h"
+
+#include "display/control/canvas-item-rect.h"
+
+#include "object/sp-namedview.h"
+
+#include "ui/tool/commit-events.h"
+#include "ui/tool/control-point-selection.h"
+#include "ui/tool/event-utils.h"
+#include "ui/tool/node.h"
+#include "ui/tool/selectable-control-point.h"
+#include "ui/tool/transform-handle-set.h"
+#include "ui/tools/node-tool.h"
+
+
+GType sp_select_context_get_type();
+
+namespace Inkscape {
+namespace UI {
+
+namespace {
+
+SPAnchorType corner_to_anchor(unsigned c) {
+    switch (c % 4) {
+    case 0: return SP_ANCHOR_NE;
+    case 1: return SP_ANCHOR_NW;
+    case 2: return SP_ANCHOR_SW;
+    default: return SP_ANCHOR_SE;
+    }
+}
+
+SPAnchorType side_to_anchor(unsigned s) {
+    switch (s % 4) {
+    case 0: return SP_ANCHOR_N;
+    case 1: return SP_ANCHOR_W;
+    case 2: return SP_ANCHOR_S;
+    default: return SP_ANCHOR_E;
+    }
+}
+
+// TODO move those two functions into a common place
+double snap_angle(double a) {
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    int snaps = prefs->getIntLimited("/options/rotationsnapsperpi/value", 12, 1, 1000);
+    double unit_angle = M_PI / snaps;
+    return CLAMP(unit_angle * round(a / unit_angle), -M_PI, M_PI);
+}
+
+double snap_increment_degrees() {
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    int snaps = prefs->getIntLimited("/options/rotationsnapsperpi/value", 12, 1, 1000);
+    return 180.0 / snaps;
+}
+
+} // anonymous namespace
+
+ControlPoint::ColorSet TransformHandle::thandle_cset = {
+    {0x000000ff, 0x000000ff},  // normal fill, stroke
+    {0x00ff66ff, 0x000000ff},  // mouseover fill, stroke
+    {0x00ff66ff, 0x000000ff},  // clicked fill, stroke
+    //
+    {0x000000ff, 0x000000ff},  // normal fill, stroke when selected
+    {0x00ff66ff, 0x000000ff},  // mouseover fill, stroke when selected
+    {0x00ff66ff, 0x000000ff}   // clicked fill, stroke when selected
+};
+
+TransformHandle::TransformHandle(TransformHandleSet &th, SPAnchorType anchor, Inkscape::CanvasItemCtrlType type)
+    : ControlPoint(th._desktop, Geom::Point(), anchor, type, thandle_cset, th._transform_handle_group)
+    , _th(th)
+{
+    _canvas_item_ctrl->set_name("CanvasItemCtrl:TransformHandle");
+    setVisible(false);
+}
+
+// TODO: This code is duplicated in seltrans.cpp; fix this!
+void TransformHandle::getNextClosestPoint(bool reverse)
+{
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    if (prefs->getBool("/options/snapclosestonly/value", false)) {
+        if (!_all_snap_sources_sorted.empty()) {
+            if (reverse) { // Shift-tab will find a closer point
+                if (_all_snap_sources_iter == _all_snap_sources_sorted.begin()) {
+                    _all_snap_sources_iter = _all_snap_sources_sorted.end();
+                }
+                --_all_snap_sources_iter;
+            } else { // Tab will find a point further away
+                ++_all_snap_sources_iter;
+                if (_all_snap_sources_iter == _all_snap_sources_sorted.end()) {
+                    _all_snap_sources_iter = _all_snap_sources_sorted.begin();
+                }
+            }
+
+            _snap_points.clear();
+            _snap_points.push_back(*_all_snap_sources_iter);
+
+            // Show the updated snap source now; otherwise it won't be shown until the selection is being moved again
+            SnapManager &m = _desktop->namedview->snap_manager;
+            m.setup(_desktop);
+            m.displaySnapsource(*_all_snap_sources_iter);
+            m.unSetup();
+        }
+    }
+}
+
+bool TransformHandle::grabbed(GdkEventMotion *)
+{
+    _origin = position();
+    _last_transform.setIdentity();
+    startTransform();
+
+    _th._setActiveHandle(this);
+    _setLurking(true);
+    _setState(_state);
+
+    // Collect the snap-candidates, one for each selected node. These will be stored in the _snap_points vector.
+    Inkscape::UI::Tools::NodeTool *nt = INK_NODE_TOOL(_th._desktop->event_context);
+    //ControlPointSelection *selection = nt->_selected_nodes.get();
+    ControlPointSelection* selection = nt->_selected_nodes;
+
+    selection->setOriginalPoints();
+    selection->getOriginalPoints(_snap_points);
+    selection->getUnselectedPoints(_unselected_points);
+
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    if (prefs->getBool("/options/snapclosestonly/value", false)) {
+        // Find the closest snap source candidate
+        _all_snap_sources_sorted = _snap_points;
+
+        // Calculate and store the distance to the reference point for each snap candidate point
+        for(auto & i : _all_snap_sources_sorted) {
+            i.setDistance(Geom::L2(i.getPoint() - _origin));
+        }
+
+        // Sort them ascending, using the distance calculated above as the single criteria
+        std::sort(_all_snap_sources_sorted.begin(), _all_snap_sources_sorted.end());
+
+        // Now get the closest snap source
+        _snap_points.clear();
+        if (!_all_snap_sources_sorted.empty()) {
+            _all_snap_sources_iter = _all_snap_sources_sorted.begin();
+            _snap_points.push_back(_all_snap_sources_sorted.front());
+        }
+    }
+
+    return false;
+}
+
+void TransformHandle::dragged(Geom::Point &new_pos, GdkEventMotion *event)
+{
+    Geom::Affine t = computeTransform(new_pos, event);
+    // protect against degeneracies
+    if (t.isSingular()) return;
+    Geom::Affine incr = _last_transform.inverse() * t;
+    if (incr.isSingular()) return;
+    _th.signal_transform.emit(incr);
+    _last_transform = t;
+}
+
+void TransformHandle::ungrabbed(GdkEventButton *)
+{
+    _snap_points.clear();
+    _th._clearActiveHandle();
+    _setLurking(false);
+    _setState(_state);
+    endTransform();
+    _th.signal_commit.emit(getCommitEvent());
+
+    //updates the positions of the nodes
+    Inkscape::UI::Tools::NodeTool *nt = INK_NODE_TOOL(_th._desktop->event_context);
+    ControlPointSelection* selection = nt->_selected_nodes;
+    selection->setOriginalPoints();
+}
+
+
+class ScaleHandle : public TransformHandle {
+public:
+    ScaleHandle(TransformHandleSet &th, SPAnchorType anchor, Inkscape::CanvasItemCtrlType type)
+        : TransformHandle(th, anchor, type)
+    {}
+protected:
+    Glib::ustring _getTip(unsigned state) const override {
+        if (state_held_control(state)) {
+            if (state_held_shift(state)) {
+                return C_("Transform handle tip",
+                    "<b>Shift+Ctrl</b>: scale uniformly about the rotation center");
+            }
+            return C_("Transform handle tip", "<b>Ctrl:</b> scale uniformly");
+        }
+        if (state_held_shift(state)) {
+            if (state_held_alt(state)) {
+                return C_("Transform handle tip",
+                    "<b>Shift+Alt</b>: scale using an integer ratio about the rotation center");
+            }
+            return C_("Transform handle tip", "<b>Shift</b>: scale from the rotation center");
+        }
+        if (state_held_alt(state)) {
+            return C_("Transform handle tip", "<b>Alt</b>: scale using an integer ratio");
+        }
+        return C_("Transform handle tip", "<b>Scale handle</b>: drag to scale the selection");
+    }
+
+    Glib::ustring _getDragTip(GdkEventMotion */*event*/) const override {
+        return format_tip(C_("Transform handle tip",
+            "Scale by %.2f%% x %.2f%%"), _last_scale_x * 100, _last_scale_y * 100);
+    }
+
+    bool _hasDragTips() const override { return true; }
+
+    static double _last_scale_x, _last_scale_y;
+};
+double ScaleHandle::_last_scale_x = 1.0;
+double ScaleHandle::_last_scale_y = 1.0;
+
+/**
+ * Corner scaling handle for node transforms.
+ */
+class ScaleCornerHandle : public ScaleHandle {
+public:
+
+    ScaleCornerHandle(TransformHandleSet &th, unsigned corner, unsigned d_corner) :
+        ScaleHandle(th, corner_to_anchor(d_corner), Inkscape::CANVAS_ITEM_CTRL_TYPE_ADJ_HANDLE),
+        _corner(corner)
+    {}
+
+protected:
+    void startTransform() override {
+        _sc_center = _th.rotationCenter();
+        _sc_opposite = _th.bounds().corner(_corner + 2);
+        _last_scale_x = _last_scale_y = 1.0;
+    }
+
+    Geom::Affine computeTransform(Geom::Point const &new_pos, GdkEventMotion *event) override {
+        Geom::Point scc = held_shift(*event) ? _sc_center : _sc_opposite;
+        Geom::Point vold = _origin - scc, vnew = new_pos - scc;
+        // avoid exploding the selection
+        if (Geom::are_near(vold[Geom::X], 0) || Geom::are_near(vold[Geom::Y], 0))
+            return Geom::identity();
+
+        Geom::Scale scale = Geom::Scale(vnew[Geom::X] / vold[Geom::X], vnew[Geom::Y] / vold[Geom::Y]);
+
+        if (held_alt(*event)) {
+            for (unsigned i = 0; i < 2; ++i) {
+                if (fabs(scale[i]) >= 1.0) {
+                    scale[i] = round(scale[i]);
+                } else {
+                    scale[i] = 1.0 / round(1.0 / MIN(scale[i],10));
+                }
+            }
+        } else {
+            SnapManager &m = _th._desktop->namedview->snap_manager;
+            m.setupIgnoreSelection(_th._desktop, true, &_unselected_points);
+
+            Inkscape::PureScale *ptr;
+            if (held_control(*event)) {
+                scale[0] = scale[1] = std::min(scale[0], scale[1]);
+                ptr = new Inkscape::PureScaleConstrained(Geom::Scale(scale[0], scale[1]), scc);
+            } else {
+                ptr = new Inkscape::PureScale(Geom::Scale(scale[0], scale[1]), scc, false);
+            }
+            m.snapTransformed(_snap_points, _origin, (*ptr));
+            m.unSetup();
+            if (ptr->best_snapped_point.getSnapped()) {
+                scale = ptr->getScaleSnapped();
+            }
+
+            delete ptr;
+        }
+
+        _last_scale_x = scale[0];
+        _last_scale_y = scale[1];
+        Geom::Affine t = Geom::Translate(-scc)
+            * Geom::Scale(scale[0], scale[1])
+            * Geom::Translate(scc);
+        return t;
+    }
+
+    CommitEvent getCommitEvent() override {
+        return _last_transform.isUniformScale()
+            ? COMMIT_MOUSE_SCALE_UNIFORM
+            : COMMIT_MOUSE_SCALE;
+    }
+
+private:
+
+    Geom::Point _sc_center;
+    Geom::Point _sc_opposite;
+    unsigned _corner;
+};
+
+/**
+ * Side scaling handle for node transforms.
+ */
+class ScaleSideHandle : public ScaleHandle {
+public:
+    ScaleSideHandle(TransformHandleSet &th, unsigned side, unsigned d_side)
+        : ScaleHandle(th, side_to_anchor(d_side), Inkscape::CANVAS_ITEM_CTRL_TYPE_ADJ_HANDLE)
+        , _side(side)
+    {}
+protected:
+    void startTransform() override {
+        _sc_center = _th.rotationCenter();
+        Geom::Rect b = _th.bounds();
+        _sc_opposite = Geom::middle_point(b.corner(_side + 2), b.corner(_side + 3));
+        _last_scale_x = _last_scale_y = 1.0;
+    }
+    Geom::Affine computeTransform(Geom::Point const &new_pos, GdkEventMotion *event) override {
+        Geom::Point scc = held_shift(*event) ? _sc_center : _sc_opposite;
+        Geom::Point vs;
+        Geom::Dim2 d1 = static_cast<Geom::Dim2>((_side + 1) % 2);
+        Geom::Dim2 d2 = static_cast<Geom::Dim2>(_side % 2);
+
+        // avoid exploding the selection
+        if (Geom::are_near(scc[d1], _origin[d1]))
+            return Geom::identity();
+
+        vs[d1] = (new_pos - scc)[d1] / (_origin - scc)[d1];
+        if (held_alt(*event)) {
+            if (fabs(vs[d1]) >= 1.0) {
+                vs[d1] = round(vs[d1]);
+            } else {
+                vs[d1] = 1.0 / round(1.0 / MIN(vs[d1],10));
+            }
+            vs[d2] = 1.0;
+        } else {
+            SnapManager &m = _th._desktop->namedview->snap_manager;
+            m.setupIgnoreSelection(_th._desktop, true, &_unselected_points);
+
+            bool uniform = held_control(*event);
+            Inkscape::PureStretchConstrained psc = Inkscape::PureStretchConstrained(vs[d1], scc, d1, uniform);
+            m.snapTransformed(_snap_points, _origin, psc);
+            m.unSetup();
+
+            if (psc.best_snapped_point.getSnapped()) {
+                Geom::Point result = psc.getStretchSnapped().vector(); //best_snapped_point.getTransformation();
+                vs[d1] = result[d1];
+                vs[d2] = result[d2];
+            } else {
+                // on ctrl, apply uniform scaling instead of stretching
+                // Preserve aspect ratio, but never flip in the dimension not being edited (by using fabs())
+                vs[d2] = uniform ? fabs(vs[d1]) : 1.0;
+            }
+        }
+
+        _last_scale_x = vs[Geom::X];
+        _last_scale_y = vs[Geom::Y];
+        Geom::Affine t = Geom::Translate(-scc)
+            * Geom::Scale(vs)
+            * Geom::Translate(scc);
+        return t;
+    }
+    CommitEvent getCommitEvent() override {
+        return _last_transform.isUniformScale()
+            ? COMMIT_MOUSE_SCALE_UNIFORM
+            : COMMIT_MOUSE_SCALE;
+    }
+
+private:
+
+    Geom::Point _sc_center;
+    Geom::Point _sc_opposite;
+    unsigned _side;
+};
+
+/**
+ * Rotation handle for node transforms.
+ */
+class RotateHandle : public TransformHandle {
+public:
+    RotateHandle(TransformHandleSet &th, unsigned corner, unsigned d_corner)
+        : TransformHandle(th, corner_to_anchor(d_corner), Inkscape::CANVAS_ITEM_CTRL_TYPE_ADJ_ROTATE)
+        , _corner(corner)
+    {}
+protected:
+
+    void startTransform() override {
+        _rot_center = _th.rotationCenter();
+        _rot_opposite = _th.bounds().corner(_corner + 2);
+        _last_angle = 0;
+    }
+
+    Geom::Affine computeTransform(Geom::Point const &new_pos, GdkEventMotion *event) override
+    {
+        Geom::Point rotc = held_shift(*event) ? _rot_opposite : _rot_center;
+        double angle = Geom::angle_between(_origin - rotc, new_pos - rotc);
+        if (held_control(*event)) {
+            angle = snap_angle(angle);
+        } else {
+            SnapManager &m = _th._desktop->namedview->snap_manager;
+            m.setupIgnoreSelection(_th._desktop, true, &_unselected_points);
+            Inkscape::PureRotateConstrained prc = Inkscape::PureRotateConstrained(angle, rotc);
+            m.snapTransformed(_snap_points, _origin, prc);
+            m.unSetup();
+
+            if (prc.best_snapped_point.getSnapped()) {
+                angle = prc.getAngleSnapped(); //best_snapped_point.getTransformation()[0];
+            }
+        }
+
+        _last_angle = angle;
+        Geom::Affine t = Geom::Translate(-rotc)
+            * Geom::Rotate(angle)
+            * Geom::Translate(rotc);
+        return t;
+    }
+
+    CommitEvent getCommitEvent() override { return COMMIT_MOUSE_ROTATE; }
+
+    Glib::ustring _getTip(unsigned state) const override {
+        if (state_held_shift(state)) {
+            if (state_held_control(state)) {
+                return format_tip(C_("Transform handle tip",
+                    "<b>Shift+Ctrl</b>: rotate around the opposite corner and snap "
+                    "angle to %f° increments"), snap_increment_degrees());
+            }
+            return C_("Transform handle tip", "<b>Shift</b>: rotate around the opposite corner");
+        }
+        if (state_held_control(state)) {
+            return format_tip(C_("Transform handle tip",
+                "<b>Ctrl</b>: snap angle to %f° increments"), snap_increment_degrees());
+        }
+        return C_("Transform handle tip", "<b>Rotation handle</b>: drag to rotate "
+            "the selection around the rotation center");
+    }
+
+    Glib::ustring _getDragTip(GdkEventMotion */*event*/) const override {
+        return format_tip(C_("Transform handle tip", "Rotate by %.2f°"),
+            _last_angle * 180.0 / M_PI);
+    }
+
+    bool _hasDragTips() const override { return true; }
+
+private:
+    Geom::Point _rot_center;
+    Geom::Point _rot_opposite;
+    unsigned _corner;
+    static double _last_angle;
+};
+double RotateHandle::_last_angle = 0;
+
+class SkewHandle : public TransformHandle {
+public:
+    SkewHandle(TransformHandleSet &th, unsigned side, unsigned d_side)
+        : TransformHandle(th, side_to_anchor(d_side), Inkscape::CANVAS_ITEM_CTRL_TYPE_ADJ_SKEW)
+        , _side(side)
+    {}
+
+protected:
+
+    void startTransform() override {
+        _skew_center = _th.rotationCenter();
+        Geom::Rect b = _th.bounds();
+        _skew_opposite = Geom::middle_point(b.corner(_side + 2), b.corner(_side + 3));
+        _last_angle = 0;
+        _last_horizontal = _side % 2;
+    }
+
+    Geom::Affine computeTransform(Geom::Point const &new_pos, GdkEventMotion *event) override
+    {
+        Geom::Point scc = held_shift(*event) ? _skew_center : _skew_opposite;
+        Geom::Dim2 d1 = static_cast<Geom::Dim2>((_side + 1) % 2);
+        Geom::Dim2 d2 = static_cast<Geom::Dim2>(_side % 2);
+
+        Geom::Point const initial_delta = _origin - scc;
+
+        if (fabs(initial_delta[d1]) < 1e-15) {
+            return Geom::Affine();
+        }
+
+        // Calculate the scale factors, which can be either visual or geometric
+        // depending on which type of bbox is currently being used (see preferences -> selector tool)
+        Geom::Scale scale = calcScaleFactors(_origin, new_pos, scc, false);
+        Geom::Scale skew = calcScaleFactors(_origin, new_pos, scc, true);
+        scale[d2] = 1;
+        skew[d2] = 1;
+
+        // Skew handles allow scaling up to integer multiples of the original size
+        // in the second direction; prevent explosions
+
+        if (fabs(scale[d1]) < 1) {
+            // Prevent shrinking of the selected object, while allowing mirroring
+            scale[d1] = copysign(1.0, scale[d1]);
+        } else {
+            // Allow expanding of the selected object by integer multiples
+            scale[d1] = floor(scale[d1] + 0.5);
+        }
+
+        double angle = atan(skew[d1] / scale[d1]);
+
+        if (held_control(*event)) {
+            angle = snap_angle(angle);
+            skew[d1] = tan(angle) * scale[d1];
+        } else {
+            SnapManager &m = _th._desktop->namedview->snap_manager;
+            m.setupIgnoreSelection(_th._desktop, true, &_unselected_points);
+
+            Inkscape::PureSkewConstrained psc = Inkscape::PureSkewConstrained(skew[d1], scale[d1], scc, d2);
+            m.snapTransformed(_snap_points, _origin, psc);
+            m.unSetup();
+
+            if (psc.best_snapped_point.getSnapped()) {
+                skew[d1] = psc.getSkewSnapped(); //best_snapped_point.getTransformation()[0];
+            }
+        }
+
+        _last_angle = angle;
+
+        // Update the handle position
+        Geom::Point new_new_pos;
+        new_new_pos[d2] = initial_delta[d1] * skew[d1] + _origin[d2];
+        new_new_pos[d1] = initial_delta[d1] * scale[d1] + scc[d1];
+
+        // Calculate the relative affine
+        Geom::Affine relative_affine = Geom::identity();
+        relative_affine[2*d1 + d1] = (new_new_pos[d1] - scc[d1]) / initial_delta[d1];
+        relative_affine[2*d1 + (d2)] = (new_new_pos[d2] - _origin[d2]) / initial_delta[d1];
+        relative_affine[2*(d2) + (d1)] = 0;
+        relative_affine[2*(d2) + (d2)] = 1;
+
+        for (int i = 0; i < 2; i++) {
+            if (fabs(relative_affine[3*i]) < 1e-15) {
+                relative_affine[3*i] = 1e-15;
+            }
+        }
+
+        Geom::Affine t = Geom::Translate(-scc)
+            * relative_affine
+            * Geom::Translate(scc);
+
+        return t;
+    }
+
+    CommitEvent getCommitEvent() override {
+        return (_side % 2)
+            ? COMMIT_MOUSE_SKEW_Y
+            : COMMIT_MOUSE_SKEW_X;
+    }
+
+    Glib::ustring _getTip(unsigned state) const override {
+        if (state_held_shift(state)) {
+            if (state_held_control(state)) {
+                return format_tip(C_("Transform handle tip",
+                    "<b>Shift+Ctrl</b>: skew about the rotation center with snapping "
+                    "to %f° increments"), snap_increment_degrees());
+            }
+            return C_("Transform handle tip", "<b>Shift</b>: skew about the rotation center");
+        }
+        if (state_held_control(state)) {
+            return format_tip(C_("Transform handle tip",
+                "<b>Ctrl</b>: snap skew angle to %f° increments"), snap_increment_degrees());
+        }
+        return C_("Transform handle tip",
+            "<b>Skew handle</b>: drag to skew (shear) selection about "
+            "the opposite handle");
+    }
+
+    Glib::ustring _getDragTip(GdkEventMotion */*event*/) const override {
+        if (_last_horizontal) {
+            return format_tip(C_("Transform handle tip", "Skew horizontally by %.2f°"),
+                _last_angle * 360.0);
+        } else {
+            return format_tip(C_("Transform handle tip", "Skew vertically by %.2f°"),
+                _last_angle * 360.0);
+        }
+    }
+
+    bool _hasDragTips() const override { return true; }
+
+private:
+
+    Geom::Point _skew_center;
+    Geom::Point _skew_opposite;
+    unsigned _side;
+    static bool _last_horizontal;
+    static double _last_angle;
+};
+bool SkewHandle::_last_horizontal = false;
+double SkewHandle::_last_angle = 0;
+
+class RotationCenter : public ControlPoint {
+
+public:
+    RotationCenter(TransformHandleSet &th) :
+        ControlPoint(th._desktop, Geom::Point(), SP_ANCHOR_CENTER,
+                     Inkscape::CANVAS_ITEM_CTRL_TYPE_ADJ_CENTER,
+                     _center_cset, th._transform_handle_group),
+        _th(th)
+    {
+        setVisible(false);
+    }
+
+protected:
+    void dragged(Geom::Point &new_pos, GdkEventMotion *event) override {
+        SnapManager &sm = _th._desktop->namedview->snap_manager;
+        sm.setup(_th._desktop);
+        bool snap = !held_shift(*event) && sm.someSnapperMightSnap();
+        if (held_control(*event)) {
+            // constrain to axes
+            Geom::Point origin = _last_drag_origin();
+            std::vector<Inkscape::Snapper::SnapConstraint> constraints;
+            constraints.emplace_back(origin, Geom::Point(1, 0));
+            constraints.emplace_back(origin, Geom::Point(0, 1));
+            new_pos = sm.multipleConstrainedSnaps(Inkscape::SnapCandidatePoint(new_pos,
+                SNAPSOURCE_ROTATION_CENTER), constraints, held_shift(*event)).getPoint();
+        } else if (snap) {
+            sm.freeSnapReturnByRef(new_pos, SNAPSOURCE_ROTATION_CENTER);
+        }
+        sm.unSetup();
+    }
+    Glib::ustring _getTip(unsigned /*state*/) const override {
+        return C_("Transform handle tip",
+            "<b>Rotation center</b>: drag to change the origin of transforms");
+    }
+
+private:
+
+    static ColorSet _center_cset;
+    TransformHandleSet &_th;
+};
+
+ControlPoint::ColorSet RotationCenter::_center_cset = {
+    {0x000000ff, 0x000000ff},  // normal fill, stroke
+    {0x00ff66ff, 0x000000ff},  // mouseover fill, stroke
+    {0x00ff66ff, 0x000000ff},  // clicked fill, stroke
+    //
+    {0x000000ff, 0x000000ff},  // normal fill, stroke when selected
+    {0x00ff66ff, 0x000000ff},  // mouseover fill, stroke when selected
+    {0x00ff66ff, 0x000000ff}   // clicked fill, stroke when selected
+};
+
+
+TransformHandleSet::TransformHandleSet(SPDesktop *d, Inkscape::CanvasItemGroup *th_group)
+    : Manipulator(d)
+    , _active(nullptr)
+    , _transform_handle_group(th_group)
+    , _mode(MODE_SCALE)
+    , _in_transform(false)
+    , _visible(true)
+{
+    _trans_outline = new Inkscape::CanvasItemRect(_desktop->getCanvasControls());
+    _trans_outline->set_name("CanvasItemRect:Transform");
+    _trans_outline->hide();
+    _trans_outline->set_dashed(true);
+
+    bool y_inverted = !d->is_yaxisdown();
+    for (unsigned i = 0; i < 4; ++i) {
+        unsigned d_c = y_inverted ? i : 3 - i;
+        unsigned d_s = y_inverted ? i : 6 - i;
+        _scale_corners[i] = new ScaleCornerHandle(*this, i, d_c);
+        _scale_sides[i] = new ScaleSideHandle(*this, i, d_s);
+        _rot_corners[i] = new RotateHandle(*this, i, d_c);
+        _skew_sides[i] = new SkewHandle(*this, i, d_s);
+    }
+    _center = new RotationCenter(*this);
+    // when transforming, update rotation center position
+    signal_transform.connect(sigc::mem_fun(*_center, &RotationCenter::transform));
+}
+
+TransformHandleSet::~TransformHandleSet()
+{
+    for (auto & _handle : _handles) {
+        delete _handle;
+    }
+}
+
+void TransformHandleSet::setMode(Mode m)
+{
+    _mode = m;
+    _updateVisibility(_visible);
+}
+
+Geom::Rect TransformHandleSet::bounds() const
+{
+    return Geom::Rect(*_scale_corners[0], *_scale_corners[2]);
+}
+
+ControlPoint const &TransformHandleSet::rotationCenter() const
+{
+    return *_center;
+}
+
+ControlPoint &TransformHandleSet::rotationCenter()
+{
+    return *_center;
+}
+
+void TransformHandleSet::setVisible(bool v)
+{
+    if (_visible != v) {
+        _visible = v;
+        _updateVisibility(_visible);
+    }
+}
+
+void TransformHandleSet::setBounds(Geom::Rect const &r, bool preserve_center)
+{
+    if (_in_transform) {
+        _trans_outline->set_rect(r);
+    } else {
+        for (unsigned i = 0; i < 4; ++i) {
+            _scale_corners[i]->move(r.corner(i));
+            _scale_sides[i]->move(Geom::middle_point(r.corner(i), r.corner(i+1)));
+            _rot_corners[i]->move(r.corner(i));
+            _skew_sides[i]->move(Geom::middle_point(r.corner(i), r.corner(i+1)));
+        }
+        if (!preserve_center) _center->move(r.midpoint());
+        if (_visible) _updateVisibility(true);
+    }
+}
+
+bool TransformHandleSet::event(Inkscape::UI::Tools::ToolBase *, GdkEvent*)
+{
+    return false;
+}
+
+void TransformHandleSet::_emitTransform(Geom::Affine const &t)
+{
+    signal_transform.emit(t);
+    _center->transform(t);
+}
+
+void TransformHandleSet::_setActiveHandle(ControlPoint *th)
+{
+    _active = th;
+    if (_in_transform)
+        throw std::logic_error("Transform initiated when another transform in progress");
+    _in_transform = true;
+    // hide all handles except the active one
+    _updateVisibility(false);
+    _trans_outline->show();
+}
+
+void TransformHandleSet::_clearActiveHandle()
+{
+    // This can only be called from handles, so they had to be visible before _setActiveHandle
+    _trans_outline->hide();
+    _active = nullptr;
+    _in_transform = false;
+    _updateVisibility(_visible);
+}
+
+void TransformHandleSet::_updateVisibility(bool v)
+{
+    if (v) {
+        Geom::Rect b = bounds();
+
+        // Roughly estimate handle size.
+        Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+        int handle_index = prefs->getIntLimited("/options/grabsize/value", 3, 1, 15);
+        int handle_size = handle_index * 2 + 1; // Handle pixmaps are actually larger but that's to allow space when handle is rotated.
+
+        Geom::Point bp = b.dimensions();
+
+        // do not scale when the bounding rectangle has zero width or height
+        bool show_scale = (_mode == MODE_SCALE) && !Geom::are_near(b.minExtent(), 0);
+        // do not rotate if the bounding rectangle is degenerate
+        bool show_rotate = (_mode == MODE_ROTATE_SKEW) && !Geom::are_near(b.maxExtent(), 0);
+        bool show_scale_side[2], show_skew[2];
+
+        // show sides if:
+        // a) there is enough space between corner handles, or
+        // b) corner handles are not shown, but side handles make sense
+        // this affects horizontal and vertical scale handles; skew handles never
+        // make sense if rotate handles are not shown
+        for (unsigned i = 0; i < 2; ++i) {
+            Geom::Dim2 d = static_cast<Geom::Dim2>(i);
+            Geom::Dim2 otherd = static_cast<Geom::Dim2>((i+1)%2);
+            show_scale_side[i] = (_mode == MODE_SCALE);
+            show_scale_side[i] &= (show_scale ? bp[d] >= handle_size
+                : !Geom::are_near(bp[otherd], 0));
+            show_skew[i] = (show_rotate && bp[d] >= handle_size
+                && !Geom::are_near(bp[otherd], 0));
+        }
+
+        for (unsigned i = 0; i < 4; ++i) {
+            _scale_corners[i]->setVisible(show_scale);
+            _rot_corners[i]->setVisible(show_rotate);
+            _scale_sides[i]->setVisible(show_scale_side[i%2]);
+            _skew_sides[i]->setVisible(show_skew[i%2]);
+        }
+
+        // show rotation center
+        _center->setVisible(show_rotate);
+    } else {
+        for (auto & _handle : _handles) {
+            if (_handle != _active)
+                _handle->setVisible(false);
+        }
+    }
+    
+}
+
+} // namespace UI
+} // namespace Inkscape
+
+/*
+  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 :