First GSoC node tool commit to Bazaar

(bzr r8846.1.1)

1 files changed, 653 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 000000000..f3e2847e4
--- /dev/null
+++ b/src/ui/tool/transform-handle-set.cpp
@@ -0,0 +1,653 @@
+/** @file
+ * Affine transform handles component
+ */
+/* Authors:
+ *   Krzysztof Kosiński <tweenk.pl@gmail.com>
+ *
+ * Copyright (C) 2009 Authors
+ * Released under GNU GPL, read the file 'COPYING' for more information
+ */
+
+#include <math.h>
+#include <algorithm>
+#include <glib.h>
+#include <glib/gi18n.h>
+#include <gdk/gdk.h>
+#include <2geom/transforms.h>
+#include "desktop.h"
+#include "desktop-handles.h"
+#include "display/sodipodi-ctrlrect.h"
+#include "preferences.h"
+#include "ui/tool/commit-events.h"
+#include "ui/tool/control-point.h"
+#include "ui/tool/event-utils.h"
+#include "ui/tool/transform-handle-set.h"
+
+// FIXME BRAIN DAMAGE WARNING: this is a global variable in select-context.cpp
+// Should be moved to a location where it can be accessed globally
+extern GdkPixbuf *handles[];
+GType sp_select_context_get_type();
+
+namespace Inkscape {
+namespace UI {
+
+namespace {
+Gtk::AnchorType corner_to_anchor(unsigned c) {
+    switch (c % 4) {
+    case 0: return Gtk::ANCHOR_NE;
+    case 1: return Gtk::ANCHOR_NW;
+    case 2: return Gtk::ANCHOR_SW;
+    default: return Gtk::ANCHOR_SE;
+    }
+}
+Gtk::AnchorType side_to_anchor(unsigned s) {
+    switch (s % 4) {
+    case 0: return Gtk::ANCHOR_N;
+    case 1: return Gtk::ANCHOR_W;
+    case 2: return Gtk::ANCHOR_S;
+    default: return Gtk::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;
+}
+
+ControlPoint::ColorSet thandle_cset = {
+    {0x000000ff, 0x000000ff},
+    {0x00ff6600, 0x000000ff},
+    {0x00ff6600, 0x000000ff}
+};
+
+ControlPoint::ColorSet center_cset = {
+    {0x00000000, 0x000000ff},
+    {0x00000000, 0xff0000b0},
+    {0x00000000, 0xff0000b0}    
+};
+} // anonymous namespace
+
+/** Base class for node transform handles to simplify implementation */
+class TransformHandle : public ControlPoint {
+public:
+    TransformHandle(TransformHandleSet &th, Gtk::AnchorType anchor, Glib::RefPtr<Gdk::Pixbuf> pb)
+        : ControlPoint(th._desktop, Geom::Point(), anchor, pb, &thandle_cset,
+            th._transform_handle_group)
+        , _th(th)
+    {
+        setVisible(false);
+        signal_grabbed.connect(
+            sigc::bind_return(
+                sigc::hide(
+                    sigc::mem_fun(*this, &TransformHandle::_grabbedHandler)),
+                false));
+        signal_dragged.connect(
+            sigc::hide<0>(
+                sigc::mem_fun(*this, &TransformHandle::_draggedHandler)));
+        signal_ungrabbed.connect(
+            sigc::hide(
+                sigc::mem_fun(*this, &TransformHandle::_ungrabbedHandler)));
+    }
+protected:
+    virtual void startTransform() {}
+    virtual void endTransform() {}
+    virtual Geom::Matrix computeTransform(Geom::Point const &pos, GdkEventMotion *event) = 0;
+    virtual CommitEvent getCommitEvent() = 0;
+
+    Geom::Matrix _last_transform;
+    Geom::Point _origin;
+    TransformHandleSet &_th;
+private:
+    void _grabbedHandler() {
+        _origin = position();
+        _last_transform.setIdentity();
+        startTransform();
+
+        _th._setActiveHandle(this);
+        _cset = &invisible_cset;
+        _setState(_state);
+    }
+    void _draggedHandler(Geom::Point &new_pos, GdkEventMotion *event)
+    {
+        Geom::Matrix t = computeTransform(new_pos, event);
+        // protect against degeneracies
+        if (t.isSingular()) return;
+        Geom::Matrix incr = _last_transform.inverse() * t;
+        if (incr.isSingular()) return;
+        _th.signal_transform.emit(incr);
+        _last_transform = t;
+    }
+    void _ungrabbedHandler() {
+        _th._clearActiveHandle();
+        _cset = &thandle_cset;
+        _setState(_state);
+        endTransform();
+        _th.signal_commit.emit(getCommitEvent());
+    }
+};
+
+class ScaleHandle : public TransformHandle {
+public:
+    ScaleHandle(TransformHandleSet &th, Gtk::AnchorType anchor, Glib::RefPtr<Gdk::Pixbuf> pb)
+        : TransformHandle(th, anchor, pb)
+    {}
+protected:
+    virtual Glib::ustring _getTip(unsigned state) {
+        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");
+    }
+    virtual Glib::ustring _getDragTip(GdkEventMotion *event) {
+        return format_tip(C_("Transform handle tip",
+            "Scale by %.2f%% x %.2f%%"), _last_scale_x * 100, _last_scale_y * 100);
+    }
+    virtual bool _hasDragTips() { 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)
+        : ScaleHandle(th, corner_to_anchor(corner), _corner_to_pixbuf(corner))
+        , _corner(corner)
+    {}
+protected:
+    virtual void startTransform() {
+        _sc_center = _th.rotationCenter();
+        _sc_opposite = _th.bounds().corner(_corner + 2);
+        _last_scale_x = _last_scale_y = 1.0;
+    }
+    virtual Geom::Matrix computeTransform(Geom::Point const &new_pos, GdkEventMotion *event) {
+        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();
+
+        double scale[2] = { vnew[Geom::X] / vold[Geom::X], vnew[Geom::Y] / vold[Geom::Y] };
+        if (held_alt(*event)) {
+            for (unsigned i = 0; i < 2; ++i) {
+                if (scale[i] >= 1.0) scale[i] = round(scale[i]);
+                else scale[i] = 1.0 / round(1.0 / scale[i]);
+            }
+        } else if (held_control(*event)) {
+            scale[0] = scale[1] = std::min(scale[0], scale[1]);
+        }
+        _last_scale_x = scale[0];
+        _last_scale_y = scale[1];
+        Geom::Matrix t = Geom::Translate(-scc)
+            * Geom::Scale(scale[0], scale[1])
+            * Geom::Translate(scc);
+        return t;
+    }
+    virtual CommitEvent getCommitEvent() {
+        return _last_transform.isUniformScale()
+            ? COMMIT_MOUSE_SCALE_UNIFORM
+            : COMMIT_MOUSE_SCALE;
+    }
+private:
+    static Glib::RefPtr<Gdk::Pixbuf> _corner_to_pixbuf(unsigned c) {
+        sp_select_context_get_type();
+        switch (c % 2) {
+        case 0: return Glib::wrap(handles[1], true);
+        default: return Glib::wrap(handles[0], true);
+        }
+    }
+    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)
+        : ScaleHandle(th, side_to_anchor(side), _side_to_pixbuf(side))
+        , _side(side)
+    {}
+protected:
+    virtual void startTransform() {
+        _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;
+    }
+    virtual Geom::Matrix computeTransform(Geom::Point const &new_pos, GdkEventMotion *event) {
+        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 (vs[d1] >= 1.0) vs[d1] = round(vs[d1]);
+            else vs[d1] = 1.0 / round(1.0 / vs[d1]);
+        }
+        vs[d2] = held_control(*event) ? vs[d1] : 1.0;
+
+        _last_scale_x = vs[Geom::X];
+        _last_scale_y = vs[Geom::Y];
+        Geom::Matrix t = Geom::Translate(-scc)
+            * Geom::Scale(vs)
+            * Geom::Translate(scc);
+        return t;
+    }
+    virtual CommitEvent getCommitEvent() {
+        return _last_transform.isUniformScale()
+            ? COMMIT_MOUSE_SCALE_UNIFORM
+            : COMMIT_MOUSE_SCALE;
+    }
+private:
+    static Glib::RefPtr<Gdk::Pixbuf> _side_to_pixbuf(unsigned c) {
+        sp_select_context_get_type();
+        switch (c % 2) {
+        case 0: return Glib::wrap(handles[3], true);
+        default: return Glib::wrap(handles[2], true);
+        }
+    }
+    Geom::Point _sc_center;
+    Geom::Point _sc_opposite;
+    unsigned _side;
+};
+
+/** Rotation handle for nodes */
+class RotateHandle : public TransformHandle {
+public:
+    RotateHandle(TransformHandleSet &th, unsigned corner)
+        : TransformHandle(th, corner_to_anchor(corner), _corner_to_pixbuf(corner))
+        , _corner(corner)
+    {}
+protected:
+    virtual void startTransform() {
+        _rot_center = _th.rotationCenter();
+        _rot_opposite = _th.bounds().corner(_corner + 2);
+        _last_angle = 0;
+    }
+    virtual Geom::Matrix computeTransform(Geom::Point const &new_pos, GdkEventMotion *event)
+    {
+        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);
+        }
+        _last_angle = angle;
+        Geom::Matrix t = Geom::Translate(-rotc)
+            * Geom::Rotate(angle)
+            * Geom::Translate(rotc);
+        return t;
+    }
+    virtual CommitEvent getCommitEvent() { return COMMIT_MOUSE_ROTATE; }
+    virtual Glib::ustring _getTip(unsigned state) {
+        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");
+    }
+    virtual Glib::ustring _getDragTip(GdkEventMotion *event) {
+        return format_tip(C_("Transform handle tip", "Rotate by %.2f°"),
+            _last_angle * 360.0);
+    }
+    virtual bool _hasDragTips() { return true; }
+private:
+    static Glib::RefPtr<Gdk::Pixbuf> _corner_to_pixbuf(unsigned c) {
+        sp_select_context_get_type();
+        switch (c % 4) {
+        case 0: return Glib::wrap(handles[10], true);
+        case 1: return Glib::wrap(handles[8], true);
+        case 2: return Glib::wrap(handles[6], true);
+        default: return Glib::wrap(handles[4], true);
+        }
+    }
+    /*
+    static Geom::Point _corner_to_offset_unit(unsigned c) {
+        switch (c % 4) {
+        case 0: return Geom::Point(-1, 1);
+        case 1: return Geom::Point(1, 1);
+        case 2: return Geom::Point(1, -1);
+        default: return Geom::Point(-1, -1);
+        }
+    }*/
+    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)
+        : TransformHandle(th, side_to_anchor(side), _side_to_pixbuf(side))
+        , _side(side)
+    {}
+protected:
+    virtual void startTransform() {
+        _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;
+    }
+    virtual Geom::Matrix computeTransform(Geom::Point const &new_pos, GdkEventMotion *event)
+    {
+        Geom::Point scc = held_shift(*event) ? _skew_center : _skew_opposite;
+        // d1 and d2 are reversed with respect to ScaleSideHandle
+        Geom::Dim2 d1 = static_cast<Geom::Dim2>(_side % 2);
+        Geom::Dim2 d2 = static_cast<Geom::Dim2>((_side + 1) % 2);
+        Geom::Point proj, scale(1.0, 1.0);
+
+        // Skew handles allow scaling up to integer multiples of the original size
+        // in the second direction; prevent explosions
+        // TODO should the scaling part be only active with Alt?
+        if (!Geom::are_near(_origin[d2], scc[d2])) {
+            scale[d2] = (new_pos - scc)[d2] / (_origin - scc)[d2];
+        }
+
+        if (scale[d2] < 1.0) {
+            scale[d2] = copysign(1.0, scale[d2]);
+        } else {
+            scale[d2] = floor(scale[d2]);
+        }
+
+        // Calculate skew angle. The angle is calculated with regards to the point obtained
+        // by projecting the handle position on the relevant side of the bounding box.
+        // This avoids degeneracies when moving the skew angle over the rotation center
+        proj[d1] = new_pos[d1];
+        proj[d2] = scc[d2] + (_origin[d2] - scc[d2]) * scale[d2];
+        double angle = 0;
+        if (!Geom::are_near(proj[d2], scc[d2]))
+            angle = Geom::angle_between(_origin - scc, proj - scc);
+        if (held_control(*event)) angle = snap_angle(angle);
+
+        // skew matrix has the from [[1, k],[0, 1]] for horizontal skew
+        // and [[1,0],[k,1]] for vertical skew.
+        Geom::Matrix skew = Geom::identity();
+        // correct the sign of the tangent
+        skew[d2 + 1] = (d1 == Geom::X ? -1.0 : 1.0) * tan(angle);
+
+        _last_angle = angle;
+        Geom::Matrix t = Geom::Translate(-scc)
+            * Geom::Scale(scale) * skew
+            * Geom::Translate(scc);
+        return t;
+    }
+    virtual CommitEvent getCommitEvent() {
+        return _side % 2
+            ? COMMIT_MOUSE_SKEW_Y
+            : COMMIT_MOUSE_SKEW_X;
+    }
+    virtual Glib::ustring _getTip(unsigned state) {
+        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");
+    }
+    virtual Glib::ustring _getDragTip(GdkEventMotion *event) {
+        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);
+        }
+    }
+    virtual bool _hasDragTips() { return true; }
+private:
+    static Glib::RefPtr<Gdk::Pixbuf> _side_to_pixbuf(unsigned s) {
+        sp_select_context_get_type();
+        switch (s % 4) {
+        case 0: return Glib::wrap(handles[9], true);
+        case 1: return Glib::wrap(handles[7], true);
+        case 2: return Glib::wrap(handles[5], true);
+        default: return Glib::wrap(handles[11], true);
+        }
+    }
+    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(), Gtk::ANCHOR_CENTER, _get_pixbuf(),
+            &center_cset, th._transform_handle_group)
+        , _th(th)
+    {
+        setVisible(false);
+    }
+protected:
+    virtual Glib::ustring _getTip(unsigned state) {
+        return C_("Transform handle tip",
+            "<b>Rotation center:</b> drag to change the origin of transforms");
+    }
+private:
+    static Glib::RefPtr<Gdk::Pixbuf> _get_pixbuf() {
+        sp_select_context_get_type();
+        return Glib::wrap(handles[12], true);
+    }
+    TransformHandleSet &_th;
+};
+
+TransformHandleSet::TransformHandleSet(SPDesktop *d, SPCanvasGroup *th_group)
+    : Manipulator(d)
+    , _active(0)
+    , _transform_handle_group(th_group)
+    , _mode(MODE_SCALE)
+    , _in_transform(false)
+    , _visible(true)
+{
+    _trans_outline = static_cast<CtrlRect*>(sp_canvas_item_new(sp_desktop_controls(_desktop),
+        SP_TYPE_CTRLRECT, NULL));
+    sp_canvas_item_hide(_trans_outline);
+    _trans_outline->setDashed(true);
+
+    for (unsigned i = 0; i < 4; ++i) {
+        _scale_corners[i] = new ScaleCornerHandle(*this, i);
+        _scale_sides[i] = new ScaleSideHandle(*this, i);
+        _rot_corners[i] = new RotateHandle(*this, i);
+        _skew_sides[i] = new SkewHandle(*this, i);
+    }
+    _center = new RotationCenter(*this);
+    // when transforming, update rotation center position
+    signal_transform.connect(sigc::mem_fun(*_center, &RotationCenter::transform));
+}
+
+TransformHandleSet::~TransformHandleSet()
+{
+    for (unsigned i = 0; i < 17; ++i) {
+        delete _handles[i];
+    }
+}
+
+/** Sets the mode of transform handles (scale or rotate). */
+void TransformHandleSet::setMode(Mode m)
+{
+    _mode = m;
+    _updateVisibility(_visible);
+}
+
+Geom::Rect TransformHandleSet::bounds()
+{
+    return Geom::Rect(*_scale_corners[0], *_scale_corners[2]);
+}
+
+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->setRectangle(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(GdkEvent*)
+{
+    return false;
+}
+
+void TransformHandleSet::_emitTransform(Geom::Matrix 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);
+    sp_canvas_item_show(_trans_outline);
+}
+
+void TransformHandleSet::_clearActiveHandle()
+{
+    // This can only be called from handles, so they had to be visible before _setActiveHandle
+    sp_canvas_item_hide(_trans_outline);
+    _active = 0;
+    _in_transform = false;
+    _updateVisibility(_visible);
+}
+
+/** Update the visibility of transformation handles according to settings and the dimensions
+ * of the bounding box. It hides the handles that would have no effect or lead to
+ * discontinuities. Additionally, side handles for which there is no space are not shown. */
+void TransformHandleSet::_updateVisibility(bool v)
+{
+    if (v) {
+        Geom::Rect b = bounds();
+        Geom::Point handle_size(
+            gdk_pixbuf_get_width(handles[0]) / _desktop->current_zoom(),
+            gdk_pixbuf_get_height(handles[0]) / _desktop->current_zoom());
+        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[d]
+                : !Geom::are_near(bp[otherd], 0));
+            show_skew[i] = (show_rotate && bp[d] >= handle_size[d]
+                && !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 if there is enough space (?)
+        _center->setVisible(show_rotate /*&& bp[Geom::X] > handle_size[Geom::X]
+            && bp[Geom::Y] > handle_size[Geom::Y]*/);
+    } else {
+        for (unsigned i = 0; i < 17; ++i) {
+            if (_handles[i] != _active)
+                _handles[i]->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:encoding=utf-8:textwidth=99 :