Adding upstream version 1.2.2.upstream/1.2.2upstream

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

1 files changed, 1649 insertions, 0 deletions

diff --git a/src/ui/tools/tool-base.cpp b/src/ui/tools/tool-base.cpp
new file mode 100644
index 0000000..30e3651
--- /dev/null
+++ b/src/ui/tools/tool-base.cpp
@@ -0,0 +1,1649 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Main event handling, and related helper functions.
+ *
+ * Authors:
+ *   Lauris Kaplinski <lauris@kaplinski.com>
+ *   Frank Felfe <innerspace@iname.com>
+ *   bulia byak <buliabyak@users.sf.net>
+ *   Jon A. Cruz <jon@joncruz.org>
+ *   Kris De Gussem <Kris.DeGussem@gmail.com>
+ *
+ * Copyright (C) 1999-2012 authors
+ * Copyright (C) 2001-2002 Ximian, Inc.
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include <gdk/gdkkeysyms.h>
+#include <gdkmm/display.h>
+#include <glibmm/i18n.h>
+
+#include <set>
+
+#include "desktop-events.h"
+#include "desktop-style.h"
+#include "desktop.h"
+#include "file.h"
+#include "gradient-drag.h"
+#include "layer-manager.h"
+#include "message-context.h"
+#include "rubberband.h"
+#include "selcue.h"
+#include "selection-chemistry.h"
+#include "selection.h"
+
+#include "actions/actions-tools.h"
+
+#include "display/control/canvas-item-catchall.h" // Grab/Ungrab
+#include "display/control/canvas-item-rotate.h"
+#include "display/control/snap-indicator.h"
+
+#include "include/gtkmm_version.h"
+#include "include/macros.h"
+
+#include "object/sp-guide.h"
+
+#include "ui/contextmenu.h"
+#include "ui/cursor-utils.h"
+#include "ui/event-debug.h"
+#include "ui/interface.h"
+#include "ui/knot/knot.h"
+#include "ui/knot/knot-holder.h"
+#include "ui/knot/knot-ptr.h"
+#include "ui/modifiers.h"
+#include "ui/shape-editor.h"
+#include "ui/shortcuts.h"
+
+#include "ui/tool/commit-events.h"
+#include "ui/tool/control-point.h"
+#include "ui/tool/event-utils.h"
+#include "ui/tool/shape-record.h"
+#include "ui/tools/calligraphic-tool.h"
+#include "ui/tools/dropper-tool.h"
+#include "ui/tools/lpe-tool.h"
+#include "ui/tools/node-tool.h"
+#include "ui/tools/select-tool.h"
+#include "ui/tools/tool-base.h"
+#include "ui/widget/canvas.h"
+
+#include "widgets/desktop-widget.h"
+
+#include "xml/node-event-vector.h"
+
+// globals for temporary switching to selector by space
+static bool selector_toggled = FALSE;
+static Glib::ustring switch_selector_to;
+
+// globals for temporary switching to dropper by 'D'
+static bool dropper_toggled = FALSE;
+static Glib::ustring switch_dropper_to;
+
+// globals for keeping track of keyboard scroll events in order to accelerate
+static guint32 scroll_event_time = 0;
+static gdouble scroll_multiply = 1;
+static guint scroll_keyval = 0;
+
+// globals for key processing
+static bool latin_keys_group_valid = FALSE;
+static gint latin_keys_group;
+static std::set<int> latin_keys_groups;
+
+namespace Inkscape {
+namespace UI {
+namespace Tools {
+
+static void set_event_location(SPDesktop * desktop, GdkEvent * event);
+
+ToolBase::ToolBase(SPDesktop *desktop, std::string prefs_path, std::string cursor_filename, bool uses_snap)
+    : _desktop(desktop)
+    , _prefs_path(std::move(prefs_path))
+    , _cursor_default(std::move(cursor_filename))
+    , _cursor_filename("none")
+    , _uses_snap(uses_snap)
+{
+    pref_observer = new ToolPrefObserver(_prefs_path, this);
+    Inkscape::Preferences::get()->addObserver(*(this->pref_observer));
+    this->set_cursor(_cursor_default);
+    _desktop->getCanvas()->grab_focus();
+
+    message_context = std::unique_ptr<Inkscape::MessageContext>(new Inkscape::MessageContext(desktop->messageStack()));
+
+    // Make sure no delayed snapping events are carried over after switching tools
+    // (this is only an additional safety measure against sloppy coding, because each
+    // tool should take care of this by itself)
+    discard_delayed_snap_event();
+}
+
+ToolBase::~ToolBase() {
+    this->enableSelectionCue(false);
+
+    if (this->pref_observer) {
+        delete this->pref_observer;
+    }
+
+    if (this->_delayed_snap_event) {
+        delete this->_delayed_snap_event;
+    }
+}
+
+/**
+ * Called by our pref_observer if a preference has been changed.
+ */
+void ToolBase::set(const Inkscape::Preferences::Entry& /*val*/) {
+}
+
+
+SPGroup *ToolBase::currentLayer() const
+{
+    return _desktop->layerManager().currentLayer();
+}
+
+/**
+ * Sets the current cursor to the given filename. Does not readload if not changed.
+ */
+void ToolBase::set_cursor(std::string filename)
+{
+    if (filename != _cursor_filename) {
+        _cursor_filename = filename;
+        use_tool_cursor();
+    }
+}
+
+/**
+ * Returns the Gdk Cursor for the given filename
+ *
+ * WARNING: currently this changes the window cursor, see load_svg_cursor
+ */
+Glib::RefPtr<Gdk::Cursor> ToolBase::get_cursor(Glib::RefPtr<Gdk::Window> window, std::string filename)
+{
+    bool fillHasColor   = false;
+    bool strokeHasColor = false;
+    guint32 fillColor = sp_desktop_get_color_tool(_desktop, getPrefsPath(), true, &fillHasColor);
+    guint32 strokeColor = sp_desktop_get_color_tool(_desktop, getPrefsPath(), false, &strokeHasColor);
+    double fillOpacity = fillHasColor ? sp_desktop_get_opacity_tool(_desktop, getPrefsPath(), true) : 1.0;
+    double strokeOpacity = strokeHasColor ? sp_desktop_get_opacity_tool(_desktop, getPrefsPath(), false) : 1.0;
+
+    return load_svg_cursor(window->get_display(), window, filename,
+                           fillColor, strokeColor, fillOpacity, strokeOpacity);
+}
+
+/**
+ * Uses the saved cursor, based on the saved filename.
+ */
+void ToolBase::use_tool_cursor() {
+    if (auto window = _desktop->getCanvas()->get_window()) {
+        _cursor = get_cursor(window, _cursor_filename);
+        window->set_cursor(_cursor);
+    }
+    _desktop->waiting_cursor = false;
+}
+
+/**
+ * Set the cursor to this specific one, don't remember it.
+ *
+ * If RefPtr is empty, sets the remembered cursor (reverting it)
+ */
+void ToolBase::use_cursor(Glib::RefPtr<Gdk::Cursor> cursor)
+{
+    if (auto window = _desktop->getCanvas()->get_window()) {
+        window->set_cursor(cursor ? cursor : _cursor);
+    }
+}
+
+/**
+ * Toggles current tool between active tool and selector tool.
+ * Subroutine of sp_event_context_private_root_handler().
+ */
+static void sp_toggle_selector(SPDesktop *dt) {
+
+    if (!dt->event_context) {
+        return;
+    }
+
+    if (dynamic_cast<Inkscape::UI::Tools::SelectTool *>(dt->event_context)) {
+        if (selector_toggled) {
+            set_active_tool(dt, switch_selector_to);
+            selector_toggled = false;
+        }
+    } else {
+        selector_toggled = TRUE;
+        switch_selector_to = get_active_tool(dt);
+        set_active_tool(dt, "Select");
+    }
+}
+
+/**
+ * Toggles current tool between active tool and dropper tool.
+ * Subroutine of sp_event_context_private_root_handler().
+ */
+void sp_toggle_dropper(SPDesktop *dt) {
+
+    if (!dt->event_context) {
+        return;
+    }
+
+    if (dynamic_cast<Inkscape::UI::Tools::DropperTool *>(dt->event_context)) {
+        if (dropper_toggled) {
+            set_active_tool(dt, switch_dropper_to);
+            dropper_toggled = FALSE;
+        }
+    } else {
+        dropper_toggled = TRUE;
+        switch_dropper_to = get_active_tool(dt);
+        set_active_tool(dt, "Dropper");
+    }
+}
+
+/**
+ * Calculates and keeps track of scroll acceleration.
+ * Subroutine of sp_event_context_private_root_handler().
+ */
+static gdouble accelerate_scroll(GdkEvent *event, gdouble acceleration)
+{
+    guint32 time_diff = ((GdkEventKey *) event)->time - scroll_event_time;
+
+    /* key pressed within 500ms ? (1/2 second) */
+    if (time_diff > 500 || event->key.keyval != scroll_keyval) {
+        scroll_multiply = 1; // abort acceleration
+    } else {
+        scroll_multiply += acceleration; // continue acceleration
+    }
+
+    scroll_event_time = ((GdkEventKey *) event)->time;
+    scroll_keyval = event->key.keyval;
+
+    return scroll_multiply;
+}
+
+/** Moves the selected points along the supplied unit vector according to
+ * the modifier state of the supplied event. */
+bool ToolBase::_keyboardMove(GdkEventKey const &event, Geom::Point const &dir)
+{
+    if (held_control(event)) return false;
+    unsigned num = 1 + gobble_key_events(shortcut_key(event), 0);
+    Geom::Point delta = dir * num;
+
+    if (held_shift(event)) {
+        delta *= 10;
+    }
+
+    if (held_alt(event)) {
+        delta /= _desktop->current_zoom();
+    } else {
+        Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+        double nudge = prefs->getDoubleLimited("/options/nudgedistance/value", 2, 0, 1000, "px");
+        delta *= nudge;
+    }
+
+    bool moved = false;
+    if (shape_editor && shape_editor->has_knotholder()) {
+        KnotHolder * knotholder = shape_editor->knotholder;
+        if (knotholder && knotholder->knot_selected()) {
+            knotholder->transform_selected(Geom::Translate(delta));
+            moved = true;
+        }
+    } else {
+        auto nt = dynamic_cast<Inkscape::UI::Tools::NodeTool *>(_desktop->event_context);
+        if (nt) {
+            for (auto &_shape_editor : nt->_shape_editors) {
+                ShapeEditor *shape_editor = _shape_editor.second.get();
+                if (shape_editor && shape_editor->has_knotholder()) {
+                    KnotHolder * knotholder = shape_editor->knotholder;
+                    if (knotholder && knotholder->knot_selected()) {
+                        knotholder->transform_selected(Geom::Translate(delta));
+                        moved = true;
+                    }
+                }
+            }
+        }
+    }
+
+    return moved;
+}
+
+
+bool ToolBase::root_handler(GdkEvent* event) {
+
+#ifdef EVENT_DUMP
+    ui_dump_event (event, "ToolBase::root_handler");
+#endif
+
+    static Geom::Point button_w;
+    static unsigned int panning_cursor = 0;
+    static unsigned int zoom_rb = 0;
+
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+
+    /// @todo REmove redundant /value in preference keys
+    tolerance = prefs->getIntLimited("/options/dragtolerance/value", 0, 0, 100);
+    bool allow_panning = prefs->getBool("/options/spacebarpans/value");
+    gint ret = FALSE;
+
+    switch (event->type) {
+    case GDK_2BUTTON_PRESS:
+        if (panning) {
+            panning = PANNING_NONE;
+            ungrabCanvasEvents();
+            ret = TRUE;
+        } else {
+            /* sp_desktop_dialog(); */
+        }
+        break;
+
+    case GDK_BUTTON_PRESS:
+        // save drag origin
+        xp = (gint) event->button.x;
+        yp = (gint) event->button.y;
+        within_tolerance = true;
+
+        button_w = Geom::Point(event->button.x, event->button.y);
+
+        switch (event->button.button) {
+        case 1:
+            // TODO Does this make sense? Panning starts on passive mouse motion while space
+            // bar is pressed, it's not necessary to press the mouse button.
+            if (this->is_space_panning()) {
+                // When starting panning, make sure there are no snap events pending because these might disable the panning again
+                if (_uses_snap) {
+                    this->discard_delayed_snap_event();
+                }
+                panning = PANNING_SPACE_BUTTON1;
+
+                grabCanvasEvents(Gdk::KEY_RELEASE_MASK    |
+                                 Gdk::BUTTON_RELEASE_MASK |
+                                 Gdk::POINTER_MOTION_MASK );
+
+                ret = TRUE;
+            }
+            break;
+
+        case 2:
+            if ((event->button.state & GDK_CONTROL_MASK) && !_desktop->get_rotation_lock()) {
+                // On screen canvas rotation preview
+
+                // Grab background before doing anything else
+                _desktop->getCanvasRotate()->start(_desktop);
+                _desktop->getCanvasRotate()->show();
+
+                // CanvasItemRotate code takes over!
+                ungrabCanvasEvents();
+
+                _desktop->getCanvasRotate()->grab(Gdk::KEY_PRESS_MASK      |
+                                                 Gdk::KEY_RELEASE_MASK    |
+                                                 Gdk::BUTTON_RELEASE_MASK |
+                                                 Gdk::POINTER_MOTION_MASK,
+                                                 nullptr);  // Cursor is null.
+
+            } else if (event->button.state & GDK_SHIFT_MASK) {
+                zoom_rb = 2;
+            } else {
+                // When starting panning, make sure there are no snap events pending because these might disable the panning again
+                if (_uses_snap) {
+                    this->discard_delayed_snap_event();
+                }
+                panning = PANNING_BUTTON2;
+
+                grabCanvasEvents(Gdk::BUTTON_RELEASE_MASK |
+                                 Gdk::POINTER_MOTION_MASK );
+            }
+
+            ret = TRUE;
+            break;
+
+        case 3:
+            if (event->button.state & (GDK_SHIFT_MASK | GDK_CONTROL_MASK)) {
+                // When starting panning, make sure there are no snap events pending because these might disable the panning again
+                if (_uses_snap) {
+                    this->discard_delayed_snap_event();
+                }
+                panning = PANNING_BUTTON3;
+
+                grabCanvasEvents(Gdk::BUTTON_RELEASE_MASK |
+                                 Gdk::POINTER_MOTION_MASK );
+                ret = TRUE;
+            } else if (!are_buttons_1_and_3_on(event)) {
+                this->menu_popup(event);
+                ret = TRUE;
+            }
+            break;
+
+        default:
+            break;
+        }
+        break;
+
+    case GDK_MOTION_NOTIFY:
+        if (panning) {
+            if (panning == 4 && !xp && !yp ) {
+                // <Space> + mouse panning started, save location and grab canvas
+                xp = event->motion.x;
+                yp = event->motion.y;
+                button_w = Geom::Point(event->motion.x, event->motion.y);
+
+                grabCanvasEvents(Gdk::KEY_RELEASE_MASK    |
+                                 Gdk::BUTTON_RELEASE_MASK |
+                                 Gdk::POINTER_MOTION_MASK );
+            }
+
+            if ((panning == 2 && !(event->motion.state & GDK_BUTTON2_MASK))
+                    || (panning == 1 && !(event->motion.state & GDK_BUTTON1_MASK))
+                    || (panning == 3 && !(event->motion.state & GDK_BUTTON3_MASK))) {
+                /* Gdk seems to lose button release for us sometimes :-( */
+                panning = PANNING_NONE;
+                ungrabCanvasEvents();
+                ret = TRUE;
+            } else {
+                // To fix https://bugs.launchpad.net/inkscape/+bug/1458200
+                // we increase the tolerance because no sensible data for panning
+                if (within_tolerance && (abs((gint) event->motion.x - xp)
+                        < tolerance * 3) && (abs((gint) event->motion.y - yp)
+                        < tolerance * 3)) {
+                    // do not drag if we're within tolerance from origin
+                    break;
+                }
+
+                // 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;
+
+                // gobble subsequent motion events to prevent "sticking"
+                // when scrolling is slow
+                gobble_motion_events(panning == 2 ? GDK_BUTTON2_MASK : (panning
+                        == 1 ? GDK_BUTTON1_MASK : GDK_BUTTON3_MASK));
+
+                if (panning_cursor == 0) {
+                    panning_cursor = 1;
+                    auto display = _desktop->getCanvas()->get_display();
+                    auto window = _desktop->getCanvas()->get_window();
+                    auto cursor = Gdk::Cursor::create(display, "move");
+                    window->set_cursor(cursor);
+                }
+
+                Geom::Point const motion_w(event->motion.x, event->motion.y);
+                Geom::Point const moved_w(motion_w - button_w);
+                _desktop->scroll_relative(moved_w, true); // we're still scrolling, do not redraw
+                ret = TRUE;
+            }
+        } else if (zoom_rb) {
+            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 (Inkscape::Rubberband::get(_desktop)->is_started()) {
+                Geom::Point const motion_w(event->motion.x, event->motion.y);
+                Geom::Point const motion_dt(_desktop->w2d(motion_w));
+
+                Inkscape::Rubberband::get(_desktop)->move(motion_dt);
+            } else {
+                // Start the box where the mouse was clicked, not where it is now
+                // because otherwise our box would be offset by the amount of tolerance.
+                Geom::Point const motion_w(xp, yp);
+                Geom::Point const motion_dt(_desktop->w2d(motion_w));
+
+                Inkscape::Rubberband::get(_desktop)->start(_desktop, motion_dt);
+            }
+
+            if (zoom_rb == 2) {
+                gobble_motion_events(GDK_BUTTON2_MASK);
+            }
+        }
+        break;
+
+    case GDK_BUTTON_RELEASE: {
+        bool middle_mouse_zoom = prefs->getBool("/options/middlemousezoom/value");
+
+        xp = yp = 0;
+
+        if (panning_cursor == 1) {
+            panning_cursor = 0;
+            _desktop->getCanvas()->get_window()->set_cursor(_cursor);
+        }
+
+        if (middle_mouse_zoom && within_tolerance && (panning || zoom_rb)) {
+            zoom_rb = 0;
+
+            if (panning) {
+                panning = PANNING_NONE;
+                ungrabCanvasEvents();
+            }
+
+            Geom::Point const event_w(event->button.x, event->button.y);
+            Geom::Point const event_dt(_desktop->w2d(event_w));
+
+            double const zoom_inc = prefs->getDoubleLimited(
+                    "/options/zoomincrement/value", M_SQRT2, 1.01, 10);
+
+            _desktop->zoom_relative(event_dt, (event->button.state & GDK_SHIFT_MASK) ? 1 / zoom_inc : zoom_inc);
+            ret = TRUE;
+        } else if (panning == event->button.button) {
+            panning = PANNING_NONE;
+            ungrabCanvasEvents();
+
+            // in slow complex drawings, some of the motion events are lost;
+            // to make up for this, we scroll it once again to the button-up event coordinates
+            // (i.e. canvas will always get scrolled all the way to the mouse release point,
+            // even if few intermediate steps were visible)
+            Geom::Point const motion_w(event->button.x, event->button.y);
+            Geom::Point const moved_w(motion_w - button_w);
+
+            _desktop->scroll_relative(moved_w);
+            ret = TRUE;
+        } else if (zoom_rb == event->button.button) {
+            zoom_rb = 0;
+
+            Geom::OptRect const b = Inkscape::Rubberband::get(_desktop)->getRectangle();
+            Inkscape::Rubberband::get(_desktop)->stop();
+
+            if (b && !within_tolerance) {
+                _desktop->set_display_area(*b, 10);
+            }
+
+            ret = TRUE;
+        }
+        }
+        break;
+
+    case GDK_KEY_PRESS: {
+        double const acceleration = prefs->getDoubleLimited(
+                "/options/scrollingacceleration/value", 0, 0, 6);
+        int const key_scroll = prefs->getIntLimited("/options/keyscroll/value",
+                10, 0, 1000);
+
+        switch (get_latin_keyval(&event->key)) {
+        // GDK insists on stealing these keys (F1 for no idea what, tab for cycling widgets
+        // in the editing window). So we resteal them back and run our regular shortcut
+        // invoker on them. Tab is hardcoded. When actions are triggered by tab,
+        // we end up stealing events from GTK widgets.
+        case GDK_KEY_F1:
+            ret = Inkscape::Shortcuts::getInstance().invoke_action(&event->key);
+            break;
+        case GDK_KEY_Tab:
+            sp_selection_item_next(_desktop);
+            ret = true;
+            break;
+        case GDK_KEY_ISO_Left_Tab:
+            sp_selection_item_prev(_desktop);
+            ret = true;
+            break;
+
+        case GDK_KEY_Q:
+        case GDK_KEY_q:
+            if (_desktop->quick_zoomed()) {
+                ret = TRUE;
+            }
+            if (!MOD__SHIFT(event) && !MOD__CTRL(event) && !MOD__ALT(event)) {
+                _desktop->zoom_quick(true);
+                ret = TRUE;
+            }
+            break;
+
+        case GDK_KEY_W:
+        case GDK_KEY_w:
+        case GDK_KEY_F4:
+            /* Close view */
+            if (MOD__CTRL_ONLY(event)) {
+                sp_ui_close_view(nullptr);
+                ret = TRUE;
+            }
+            break;
+
+        case GDK_KEY_Left: // Ctrl Left
+        case GDK_KEY_KP_Left:
+        case GDK_KEY_KP_4:
+            if (MOD__CTRL_ONLY(event)) {
+                int i = (int) floor(key_scroll * accelerate_scroll(event, acceleration));
+
+                gobble_key_events(get_latin_keyval(&event->key), GDK_CONTROL_MASK);
+                _desktop->scroll_relative(Geom::Point(i, 0));
+            } else if (!_keyboardMove(event->key, Geom::Point(-1, 0))) {
+                Inkscape::Shortcuts::getInstance().invoke_action(&event->key);
+            }
+            ret = true;
+            break;
+
+        case GDK_KEY_Up: // Ctrl Up
+        case GDK_KEY_KP_Up:
+        case GDK_KEY_KP_8:
+            if (MOD__CTRL_ONLY(event)) {
+                int i = (int) floor(key_scroll * accelerate_scroll(event, acceleration));
+
+                gobble_key_events(get_latin_keyval(&event->key), GDK_CONTROL_MASK);
+                _desktop->scroll_relative(Geom::Point(0, i));
+            } else if (!_keyboardMove(event->key, Geom::Point(0, -_desktop->yaxisdir()))) {
+                Inkscape::Shortcuts::getInstance().invoke_action(&event->key);
+            }
+            ret = true;
+            break;
+
+        case GDK_KEY_Right: // Ctrl Right
+        case GDK_KEY_KP_Right:
+        case GDK_KEY_KP_6:
+            if (MOD__CTRL_ONLY(event)) {
+                int i = (int) floor(key_scroll * accelerate_scroll(event, acceleration));
+
+                gobble_key_events(get_latin_keyval(&event->key), GDK_CONTROL_MASK);
+                _desktop->scroll_relative(Geom::Point(-i, 0));
+            } else if (!_keyboardMove(event->key, Geom::Point(1, 0))) {
+                Inkscape::Shortcuts::getInstance().invoke_action(&event->key);
+            }
+            ret = true;
+            break;
+
+        case GDK_KEY_Down: // Ctrl Down
+        case GDK_KEY_KP_Down:
+        case GDK_KEY_KP_2:
+            if (MOD__CTRL_ONLY(event)) {
+                int i = (int) floor(key_scroll * accelerate_scroll(event, acceleration));
+
+                gobble_key_events(get_latin_keyval(&event->key), GDK_CONTROL_MASK);
+                _desktop->scroll_relative(Geom::Point(0, -i));
+            } else if (!_keyboardMove(event->key, Geom::Point(0, _desktop->yaxisdir()))) {
+                Inkscape::Shortcuts::getInstance().invoke_action(&event->key);
+            }
+            ret = true;
+            break;
+
+        case GDK_KEY_Menu:
+            this->menu_popup(event);
+            ret = TRUE;
+            break;
+
+        case GDK_KEY_F10:
+            if (MOD__SHIFT_ONLY(event)) {
+                this->menu_popup(event);
+                ret = TRUE;
+            }
+            break;
+
+        case GDK_KEY_space:
+            within_tolerance = true;
+            xp = yp = 0;
+            if (!allow_panning) break;
+            panning = PANNING_SPACE;
+            this->message_context->set(Inkscape::INFORMATION_MESSAGE,
+                    _("<b>Space+mouse move</b> to pan canvas"));
+
+            ret = TRUE;
+            break;
+
+        case GDK_KEY_z:
+        case GDK_KEY_Z:
+            if (MOD__ALT_ONLY(event)) {
+                _desktop->zoom_grab_focus();
+                ret = TRUE;
+            }
+            break;
+
+        default:
+            break;
+            }
+        }
+        break;
+
+    case GDK_KEY_RELEASE:
+        // Stop panning on any key release
+        if (this->is_space_panning()) {
+            this->message_context->clear();
+        }
+
+        if (panning) {
+            panning = PANNING_NONE;
+            xp = yp = 0;
+
+            ungrabCanvasEvents();
+        }
+
+        if (panning_cursor == 1) {
+            panning_cursor = 0;
+            _desktop->getCanvas()->get_window()->set_cursor(_cursor);
+        }
+
+        switch (get_latin_keyval(&event->key)) {
+        case GDK_KEY_space:
+            if (within_tolerance) {
+                // Space was pressed, but not panned
+                sp_toggle_selector(_desktop);
+
+                // Be careful, sp_toggle_selector will delete ourselves.
+                // Thus, make sure we return immediately.
+                return true;
+            }
+
+            break;
+
+        case GDK_KEY_Q:
+        case GDK_KEY_q:
+            if (_desktop->quick_zoomed()) {
+                _desktop->zoom_quick(false);
+                ret = TRUE;
+            }
+            break;
+
+        default:
+            break;
+        }
+        break;
+
+    case GDK_SCROLL: {
+        int constexpr WHEEL_SCROLL_DEFAULT = 40;
+        
+        // previously we did two wheel_scrolls for each mouse scroll
+        int const wheel_scroll = prefs->getIntLimited(
+                "/options/wheelscroll/value", WHEEL_SCROLL_DEFAULT, 0, 1000) * 2;
+
+        // Size of smooth-scrolls (only used in GTK+ 3)
+        gdouble delta_x = 0;
+        gdouble delta_y = 0;
+
+        using Modifiers::Type;
+        using Modifiers::Triggers;
+        Type action = Modifiers::Modifier::which(Triggers::CANVAS | Triggers::SCROLL, event->scroll.state);
+
+        if (action == Type::CANVAS_ROTATE && !_desktop->get_rotation_lock()) {
+            double rotate_inc = prefs->getDoubleLimited(
+                    "/options/rotateincrement/value", 15, 1, 90, "°" );
+            rotate_inc *= M_PI/180.0;
+
+            switch (event->scroll.direction) {
+            case GDK_SCROLL_UP:
+                // Do nothing
+                break;
+
+            case GDK_SCROLL_DOWN:
+                rotate_inc = -rotate_inc;
+                break;
+
+            case GDK_SCROLL_SMOOTH: {
+                gdk_event_get_scroll_deltas(event, &delta_x, &delta_y);
+#ifdef GDK_WINDOWING_QUARTZ
+                // MacBook trackpad scroll event gives pixel delta
+                delta_y /= WHEEL_SCROLL_DEFAULT;
+#endif
+                double delta_y_clamped = CLAMP(delta_y, -1.0, 1.0); // values > 1 result in excessive rotating
+                rotate_inc = rotate_inc * -delta_y_clamped;
+                break;
+            }
+
+            default:
+                rotate_inc = 0.0;
+                break;
+            }
+
+            if (rotate_inc != 0.0) {
+                Geom::Point const scroll_dt = _desktop->point();
+                _desktop->rotate_relative_keep_point(scroll_dt, rotate_inc);
+                ret = TRUE;
+            }
+
+        } else if (action == Type::CANVAS_PAN_X) {
+           /* shift + wheel, pan left--right */
+
+            switch (event->scroll.direction) {
+            case GDK_SCROLL_UP:
+            case GDK_SCROLL_LEFT:
+                _desktop->scroll_relative(Geom::Point(wheel_scroll, 0));
+                ret = TRUE;
+                break;
+
+            case GDK_SCROLL_DOWN:
+            case GDK_SCROLL_RIGHT:
+                _desktop->scroll_relative(Geom::Point(-wheel_scroll, 0));
+                ret = TRUE;
+                break;
+
+            case GDK_SCROLL_SMOOTH: {
+                gdk_event_get_scroll_deltas(event, &delta_x, &delta_y);
+#ifdef GDK_WINDOWING_QUARTZ
+                // MacBook trackpad scroll event gives pixel delta
+                delta_y /= WHEEL_SCROLL_DEFAULT;
+#endif
+                _desktop->scroll_relative(Geom::Point(wheel_scroll * -delta_y, 0));
+                ret = TRUE;
+                break;
+            }
+
+            default:
+                break;
+            }
+
+        } else if (action == Type::CANVAS_ZOOM) {
+            /* ctrl + wheel, zoom in--out */
+            double rel_zoom;
+            double const zoom_inc = prefs->getDoubleLimited(
+                    "/options/zoomincrement/value", M_SQRT2, 1.01, 10);
+
+            switch (event->scroll.direction) {
+            case GDK_SCROLL_UP:
+                rel_zoom = zoom_inc;
+                break;
+
+            case GDK_SCROLL_DOWN:
+                rel_zoom = 1 / zoom_inc;
+                break;
+
+            case GDK_SCROLL_SMOOTH: {
+                gdk_event_get_scroll_deltas(event, &delta_x, &delta_y);
+#ifdef GDK_WINDOWING_QUARTZ
+                // MacBook trackpad scroll event gives pixel delta
+                delta_y /= WHEEL_SCROLL_DEFAULT;
+#endif
+                double delta_y_clamped = CLAMP(std::abs(delta_y), 0.0, 1.0); // values > 1 result in excessive zooming
+                double zoom_inc_scaled = (zoom_inc-1) * delta_y_clamped + 1;
+                if (delta_y < 0) {
+                    rel_zoom = zoom_inc_scaled;
+                } else {
+                    rel_zoom = 1 / zoom_inc_scaled;
+                }
+                break;
+            }
+
+            default:
+                rel_zoom = 0.0;
+                break;
+            }
+
+            if (rel_zoom != 0.0) {
+                Geom::Point const scroll_dt = _desktop->point();
+                _desktop->zoom_relative(scroll_dt, rel_zoom);
+                ret = TRUE;
+            }
+
+            /* no modifier, pan up--down (left--right on multiwheel mice?) */
+        } else if (action == Type::CANVAS_PAN_Y) {
+            switch (event->scroll.direction) {
+            case GDK_SCROLL_UP:
+                _desktop->scroll_relative(Geom::Point(0, wheel_scroll));
+                break;
+
+            case GDK_SCROLL_DOWN:
+                _desktop->scroll_relative(Geom::Point(0, -wheel_scroll));
+                break;
+
+            case GDK_SCROLL_LEFT:
+                _desktop->scroll_relative(Geom::Point(wheel_scroll, 0));
+                break;
+
+            case GDK_SCROLL_RIGHT:
+                _desktop->scroll_relative(Geom::Point(-wheel_scroll, 0));
+                break;
+
+            case GDK_SCROLL_SMOOTH:
+                gdk_event_get_scroll_deltas(event, &delta_x, &delta_y);
+#ifdef GDK_WINDOWING_QUARTZ
+                // MacBook trackpad scroll event gives pixel delta
+                delta_x /= WHEEL_SCROLL_DEFAULT;
+                delta_y /= WHEEL_SCROLL_DEFAULT;
+#endif
+                _desktop->scroll_relative(Geom::Point(-wheel_scroll * delta_x, -wheel_scroll * delta_y));
+                break;
+            }
+            ret = TRUE;
+        } else {
+            g_warning("unhandled scroll event with scroll.state=0x%x", event->scroll.state);
+        }
+        break;
+    }
+
+    default:
+        break;
+    }
+
+    return ret;
+}
+
+/**
+ * This function allows to handle global tool events if _pre function is not fully overridden.
+ */
+
+void ToolBase::set_on_buttons(GdkEvent *event)
+{
+    switch (event->type) {
+        case GDK_BUTTON_PRESS:
+            switch (event->button.button) {
+                case 1:
+                    this->_button1on = true;
+                    break;
+                case 2:
+                    this->_button2on = true;
+                    break;
+                case 3:
+                    this->_button3on = true;
+                    break;
+            }
+            break;
+        case GDK_BUTTON_RELEASE:
+            switch (event->button.button) {
+                case 1:
+                    this->_button1on = false;
+                    break;
+                case 2:
+                    this->_button2on = false;
+                    break;
+                case 3:
+                    this->_button3on = false;
+                    break;
+            }
+            break;
+        case GDK_MOTION_NOTIFY:
+            if (event->motion.state & Gdk::ModifierType::BUTTON1_MASK) {
+                this->_button1on = true;
+            } else {
+                this->_button1on = false;
+            }
+            if (event->motion.state & Gdk::ModifierType::BUTTON2_MASK) {
+                this->_button2on = true;
+            } else {
+                this->_button2on = false;
+            }
+            if (event->motion.state & Gdk::ModifierType::BUTTON3_MASK) {
+                this->_button3on = true;
+            } else {
+                this->_button3on = false;
+            }
+    }
+}
+
+bool ToolBase::are_buttons_1_and_3_on() const
+{
+    return this->_button1on && this->_button3on;
+}
+
+bool ToolBase::are_buttons_1_and_3_on(GdkEvent* event)
+{
+    set_on_buttons(event);
+    return are_buttons_1_and_3_on();
+}
+
+/**
+ * Handles item specific events. Gets called from Gdk.
+ *
+ * Only reacts to right mouse button at the moment.
+ * \todo Fixme: do context sensitive popup menu on items.
+ */
+bool ToolBase::item_handler(SPItem* item, GdkEvent* event) {
+    int ret = FALSE;
+
+    switch (event->type) {
+    case GDK_BUTTON_PRESS:
+        if (!are_buttons_1_and_3_on(event) && event->button.button == 3 &&
+            !((event->button.state & GDK_SHIFT_MASK) || (event->button.state & GDK_CONTROL_MASK))) {
+            this->menu_popup(event);
+            ret = TRUE;
+        }
+        break;
+
+    default:
+        break;
+    }
+
+    return ret;
+}
+
+/**
+ * Returns true if we're hovering above a knot (needed because we don't want to pre-snap in that case).
+ */
+bool ToolBase::sp_event_context_knot_mouseover() const {
+    if (this->shape_editor) {
+        return this->shape_editor->knot_mouseover();
+    }
+
+    return false;
+}
+
+/**
+ * Enables/disables the ToolBase's SelCue.
+ */
+void ToolBase::enableSelectionCue(bool enable) {
+    if (enable) {
+        if (!_selcue) {
+            _selcue = new Inkscape::SelCue(_desktop);
+        }
+    } else {
+        delete _selcue;
+        _selcue = nullptr;
+    }
+}
+
+/*
+ * Enables/disables the ToolBase's GrDrag.
+ */
+void ToolBase::enableGrDrag(bool enable) {
+    if (enable) {
+        if (!_grdrag) {
+            _grdrag = new GrDrag(_desktop);
+        }
+    } else {
+        if (_grdrag) {
+            delete _grdrag;
+            _grdrag = nullptr;
+        }
+    }
+}
+
+/**
+ * Delete a selected GrDrag point
+ */
+bool ToolBase::deleteSelectedDrag(bool just_one)
+{
+    if (_grdrag && !_grdrag->selected.empty()) {
+        _grdrag->deleteSelected(just_one);
+        return true;
+    }
+    return false;
+}
+
+/**
+ * Return true if there is a gradient drag.
+ */
+bool ToolBase::hasGradientDrag() const
+{
+    return _grdrag && _grdrag->isNonEmpty();
+}
+
+/**
+ * Grab events from the Canvas Catchall. (Common configuration.)
+ */
+void ToolBase::grabCanvasEvents(Gdk::EventMask mask)
+{
+    _desktop->getCanvasCatchall()->grab(mask, nullptr); // Cursor is null.
+}
+
+/**
+ * Ungrab events from the Canvas Catchall. (Common configuration.)
+ */
+void ToolBase::ungrabCanvasEvents()
+{
+    _desktop->snapindicator->remove_snaptarget();
+    _desktop->getCanvasCatchall()->ungrab();
+}
+
+/** Enable (or disable) high precision for motion events
+  *
+  * This is intended to be used by drawing tools, that need to process motion events with high accuracy
+  * and high update rate (for example free hand tools)
+  *
+  * With standard accuracy some intermediate motion events might be discarded
+  *
+  * Call this function when an operation that requires high accuracy is started (e.g. mouse button is pressed
+  * to draw a line). Make sure to call it again and restore standard precision afterwards. **/
+void ToolBase::set_high_motion_precision(bool high_precision) {
+    Glib::RefPtr<Gdk::Window> window = _desktop->getToplevel()->get_window();
+
+    if (window) {
+        window->set_event_compression(!high_precision);
+    }
+}
+
+Geom::Point ToolBase::setup_for_drag_start(GdkEvent *ev)
+{
+    this->xp = static_cast<gint>(ev->button.x);
+    this->yp = static_cast<gint>(ev->button.y);
+    this->within_tolerance = true;
+
+    Geom::Point const p(ev->button.x, ev->button.y);
+    item_to_select = Inkscape::UI::Tools::sp_event_context_find_item(_desktop, p, ev->button.state & GDK_MOD1_MASK, TRUE);
+    return _desktop->w2d(p);
+}
+
+/**
+ * Discard and count matching key events from top of event bucket.
+ * Convenience function that just passes request to canvas.
+ */
+int ToolBase::gobble_key_events(guint keyval, guint mask) const
+{
+    return _desktop->canvas->gobble_key_events(keyval, mask);
+}
+
+/**
+ * Discard matching motion events from top of event bucket.
+ * Convenience function that just passes request to canvas.
+ */
+void ToolBase::gobble_motion_events(guint mask) const
+{
+    _desktop->canvas->gobble_motion_events(mask);
+}
+
+/**
+ * Calls virtual set() function of ToolBase.
+ */
+void sp_event_context_read(ToolBase *ec, gchar const *key) {
+    g_return_if_fail(ec != nullptr);
+    g_return_if_fail(key != nullptr);
+
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    Inkscape::Preferences::Entry val = prefs->getEntry(ec->getPrefsPath() + '/' + key);
+    ec->set(val);
+}
+
+/**
+ * Handles snapping events for all tools and then passes to tool_root_handler.
+ */
+gint ToolBase::start_root_handler(GdkEvent *event)
+{
+#ifdef EVENT_DEBUG
+    ui_dump_event(reinterpret_cast<GdkEvent *>(event), "ToolBase::start_root_handler");
+#endif
+
+    if (!_uses_snap) {
+        return this->tool_root_handler(event);
+    }
+
+    switch (event->type) {
+    case GDK_MOTION_NOTIFY:
+        sp_event_context_snap_delay_handler(this, nullptr, nullptr,
+                (GdkEventMotion *) event,
+                DelayedSnapEvent::EVENTCONTEXT_ROOT_HANDLER);
+        break;
+    case GDK_BUTTON_RELEASE:
+        if (_delayed_snap_event) {
+            // If we have any pending snapping action, then invoke it now
+            sp_event_context_snap_watchdog_callback(_delayed_snap_event);
+        }
+        break;
+    case GDK_BUTTON_PRESS:
+    case GDK_2BUTTON_PRESS:
+    case GDK_3BUTTON_PRESS:
+        // Snapping will be on hold if we're moving the mouse at high speeds. When starting
+        // drawing a new shape we really should snap though.
+        _desktop->namedview->snap_manager.snapprefs.setSnapPostponedGlobally(false);
+        break;
+    default:
+        break;
+    }
+
+    return this->tool_root_handler(event);
+}
+
+/**
+ * Calls the right tool's event handler, depending on the selected tool and state.
+ */
+gint ToolBase::tool_root_handler(GdkEvent *event)
+{
+#ifdef EVENT_DEBUG
+    ui_dump_event(reinterpret_cast<GdkEvent *>(event), "tool_root_handler");
+#endif
+    gint ret = false;
+
+    // Just set the on buttons for now. later, behave as intended.
+    this->set_on_buttons(event);
+
+    // refresh coordinates UI here while 'event' is still valid
+    set_event_location(_desktop, event);
+
+    // Panning has priority over tool-specific event handling
+    if (this->is_panning()) {
+        ret = ToolBase::root_handler(event);
+    } else {
+        ret = this->root_handler(event);
+    }
+
+    // at this point 'event' could be deleted already (after ctrl+w document close)
+
+    return ret;
+}
+
+/**
+ * Starts handling item snapping and pass to virtual_item_handler afterwards.
+ */
+gint ToolBase::start_item_handler(SPItem *item, GdkEvent *event)
+{
+    if (!_uses_snap) {
+        return this->virtual_item_handler(item, event);
+    }
+
+    switch (event->type) {
+    case GDK_MOTION_NOTIFY:
+        sp_event_context_snap_delay_handler(this, (gpointer) item, nullptr, (GdkEventMotion *) event, DelayedSnapEvent::EVENTCONTEXT_ITEM_HANDLER);
+        break;
+    case GDK_BUTTON_RELEASE:
+        if (_delayed_snap_event) {
+            // If we have any pending snapping action, then invoke it now
+            sp_event_context_snap_watchdog_callback(_delayed_snap_event);
+        }
+        break;
+    case GDK_BUTTON_PRESS:
+    case GDK_2BUTTON_PRESS:
+    case GDK_3BUTTON_PRESS:
+        // Snapping will be on hold if we're moving the mouse at high speeds. When starting
+        // drawing a new shape we really should snap though.
+        _desktop->namedview->snap_manager.snapprefs.setSnapPostponedGlobally(false);
+        break;
+    default:
+        break;
+    }
+
+    return this->virtual_item_handler(item, event);
+}
+
+gint ToolBase::virtual_item_handler(SPItem *item, GdkEvent *event)
+{
+    gint ret = false;
+
+    // Just set the on buttons for now. later, behave as intended.
+    this->set_on_buttons(event);
+
+    // Panning has priority over tool-specific event handling
+    if (is_panning()) {
+        ret = ToolBase::item_handler(item, event);
+    } else {
+        ret = item_handler(item, event);
+    }
+
+    if (!ret) {
+        ret = this->tool_root_handler(event);
+    } else {
+        set_event_location(_desktop, event);
+    }
+
+    return ret;
+}
+
+/**
+ * Shows coordinates on status bar.
+ */
+static void set_event_location(SPDesktop *desktop, GdkEvent *event) {
+    if (event->type != GDK_MOTION_NOTIFY) {
+        return;
+    }
+
+    Geom::Point const button_w(event->button.x, event->button.y);
+    Geom::Point const button_dt(desktop->w2d(button_w));
+    desktop->set_coordinate_status(button_dt);
+}
+
+//-------------------------------------------------------------------
+/**
+ * Create popup menu and tell Gtk to show it.
+ */
+void ToolBase::menu_popup(GdkEvent *event, SPObject *obj) {
+
+    if (!obj) {
+        if (event->type == GDK_KEY_PRESS && !_desktop->getSelection()->isEmpty()) {
+            obj = _desktop->getSelection()->items().front();
+        } else {
+            // Using the same function call used on left click in sp_select_context_item_handler() to get top of z-order
+            // fixme: sp_canvas_arena should set the top z-order object as arena->active
+            auto p = Geom::Point(event->button.x, event->button.y);
+            obj = sp_event_context_find_item (_desktop, p, false, false);
+        }
+    }
+
+    ContextMenu* menu = new ContextMenu(_desktop, obj);
+    menu->attach_to_widget(*(_desktop->getCanvas())); // So actions work!
+    menu->show();
+
+    switch (event->type) {
+    case GDK_BUTTON_PRESS:
+    case GDK_KEY_PRESS:
+        menu->popup_at_pointer(event);
+        break;
+    default:
+        break;
+    }
+}
+
+/**
+ * Show tool context specific modifier tip.
+ */
+void sp_event_show_modifier_tip(Inkscape::MessageContext *message_context,
+        GdkEvent *event, gchar const *ctrl_tip, gchar const *shift_tip,
+        gchar const *alt_tip) {
+    guint keyval = get_latin_keyval(&event->key);
+
+    bool ctrl = ctrl_tip && (MOD__CTRL(event) || (keyval == GDK_KEY_Control_L) || (keyval
+            == GDK_KEY_Control_R));
+    bool shift = shift_tip && (MOD__SHIFT(event) || (keyval == GDK_KEY_Shift_L) || (keyval
+            == GDK_KEY_Shift_R));
+    bool alt = alt_tip && (MOD__ALT(event) || (keyval == GDK_KEY_Alt_L) || (keyval
+            == GDK_KEY_Alt_R) || (keyval == GDK_KEY_Meta_L) || (keyval == GDK_KEY_Meta_R));
+
+    gchar *tip = g_strdup_printf("%s%s%s%s%s", (ctrl ? ctrl_tip : ""), (ctrl
+            && (shift || alt) ? "; " : ""), (shift ? shift_tip : ""), ((ctrl
+            || shift) && alt ? "; " : ""), (alt ? alt_tip : ""));
+
+    if (strlen(tip) > 0) {
+        message_context->flash(Inkscape::INFORMATION_MESSAGE, tip);
+    }
+
+    g_free(tip);
+}
+
+/**
+ * Try to determine the keys group of Latin layout.
+ * Check available keymap entries for Latin 'a' key and find the minimal integer value.
+ */
+static void update_latin_keys_group() {
+    GdkKeymapKey* keys;
+    gint n_keys;
+
+    latin_keys_group_valid = FALSE;
+    latin_keys_groups.clear();
+
+    if (gdk_keymap_get_entries_for_keyval(Gdk::Display::get_default()->get_keymap(), GDK_KEY_a, &keys, &n_keys)) {
+        for (gint i = 0; i < n_keys; i++) {
+            latin_keys_groups.insert(keys[i].group);
+
+            if (!latin_keys_group_valid || keys[i].group < latin_keys_group) {
+                latin_keys_group = keys[i].group;
+                latin_keys_group_valid = TRUE;
+            }
+        }
+        g_free(keys);
+    }
+}
+
+/**
+ * Initialize Latin keys group handling.
+ */
+void init_latin_keys_group() {
+    g_signal_connect(G_OBJECT(Gdk::Display::get_default()->get_keymap()),
+            "keys-changed", G_CALLBACK(update_latin_keys_group), NULL);
+    update_latin_keys_group();
+}
+
+/**
+ * Return the keyval corresponding to the key event in Latin group.
+ *
+ * Use this instead of simply event->keyval, so that your keyboard shortcuts
+ * work regardless of layouts (e.g., in Cyrillic).
+ */
+guint get_latin_keyval(GdkEventKey const *event, guint *consumed_modifiers /*= NULL*/) {
+    guint keyval = 0;
+    GdkModifierType modifiers;
+    gint group = latin_keys_group_valid ? latin_keys_group : event->group;
+
+    if (latin_keys_groups.count(event->group)) {
+        // Keyboard group is a latin layout, so just use it.
+        group = event->group;
+    }
+
+    gdk_keymap_translate_keyboard_state(
+            Gdk::Display::get_default()->get_keymap(),
+            event->hardware_keycode, (GdkModifierType) event->state, group,
+            &keyval, nullptr, nullptr, &modifiers);
+
+    if (consumed_modifiers) {
+        *consumed_modifiers = modifiers;
+    }
+    if (keyval != event->keyval) {
+        std::cerr << "get_latin_keyval: OH OH OH keyval did change! "
+                  << "  keyval: " << keyval << " (" << (char)keyval << ")"
+                  << "  event->keyval: " << event->keyval << "(" << (char)event->keyval << ")" << std::endl;
+    }
+    return keyval;
+}
+
+/**
+ * Returns item at point p in desktop.
+ *
+ * If state includes alt key mask, cyclically selects under; honors
+ * into_groups.
+ */
+SPItem *sp_event_context_find_item(SPDesktop *desktop, Geom::Point const &p,
+                                   bool select_under, bool into_groups)
+{
+    SPItem *item = nullptr;
+
+    if (select_under) {
+        auto tmp = desktop->selection->items();
+        std::vector<SPItem *> vec(tmp.begin(), tmp.end());
+        SPItem *selected_at_point = desktop->getItemFromListAtPointBottom(vec, p);
+        item = desktop->getItemAtPoint(p, into_groups, selected_at_point);
+        if (item == nullptr) { // we may have reached bottom, flip over to the top
+            item = desktop->getItemAtPoint(p, into_groups, nullptr);
+        }
+    } else {
+        item = desktop->getItemAtPoint(p, into_groups, nullptr);
+    }
+
+    return item;
+}
+
+/**
+ * Returns item if it is under point p in desktop, at any depth; otherwise returns NULL.
+ *
+ * Honors into_groups.
+ */
+SPItem *
+sp_event_context_over_item(SPDesktop *desktop, SPItem *item,
+        Geom::Point const &p) {
+	std::vector<SPItem*> temp;
+    temp.push_back(item);
+    SPItem *item_at_point = desktop->getItemFromListAtPointBottom(temp, p);
+    return item_at_point;
+}
+
+ShapeEditor *
+sp_event_context_get_shape_editor(ToolBase *ec) {
+    return ec->shape_editor;
+}
+
+
+/**
+ * Analyses the current event, calculates the mouse speed, turns snapping off (temporarily) if the
+ * mouse speed is above a threshold, and stores the current event such that it can be re-triggered when needed
+ * (re-triggering is controlled by a watchdog timer).
+ *
+ * @param ec Pointer to the event context.
+ * @param dse_item Pointer that store a reference to a canvas or to an item.
+ * @param dse_item2 Another pointer, storing a reference to a knot or controlpoint.
+ * @param event Pointer to the motion event.
+ * @param origin Identifier (enum) specifying where the delay (and the call to this method) were initiated.
+ */
+void sp_event_context_snap_delay_handler(ToolBase *ec,
+        gpointer const dse_item, gpointer const dse_item2, GdkEventMotion *event,
+        DelayedSnapEvent::DelayedSnapEventOrigin origin)
+{
+    static guint32 prev_time;
+    static std::optional<Geom::Point> prev_pos;
+
+    if (!ec->_uses_snap || ec->_dse_callback_in_process) {
+        return;
+    }
+
+    // Snapping occurs when dragging with the left mouse button down, or when hovering e.g. in the pen tool with left mouse button up
+    bool const c1 = event->state & GDK_BUTTON2_MASK; // We shouldn't hold back any events when other mouse buttons have been
+    bool const c2 = event->state & GDK_BUTTON3_MASK; // pressed, e.g. when scrolling with the middle mouse button; if we do then
+    // Inkscape will get stuck in an unresponsive state
+    bool const c3 = dynamic_cast<Inkscape::UI::Tools::CalligraphicTool *>(ec);
+    // The snap delay will repeat the last motion event, which will lead to
+    // erroneous points in the calligraphy context. And because we don't snap
+    // in this context, we might just as well disable the snap delay all together
+    bool const c4 = ec->is_panning(); // Don't snap while panning
+
+    if (c1 || c2 || c3 || c4) {
+        // Make sure that we don't send any pending snap events to a context if we know in advance
+        // that we're not going to snap any way (e.g. while scrolling with middle mouse button)
+        // Any motion event might affect the state of the context, leading to unexpected behavior
+        ec->discard_delayed_snap_event();
+    } else if (ec->getDesktop() &&
+               ec->getDesktop()->namedview->snap_manager.snapprefs.getSnapEnabledGlobally()) {
+        // Snap when speed drops below e.g. 0.02 px/msec, or when no motion events have occurred for some period.
+        // i.e. snap when we're at stand still. A speed threshold enforces snapping for tablets, which might never
+        // be fully at stand still and might keep spitting out motion events.
+        ec->getDesktop()->namedview->snap_manager.snapprefs.setSnapPostponedGlobally(true); // put snapping on hold
+
+        Geom::Point event_pos(event->x, event->y);
+        guint32 event_t = gdk_event_get_time((GdkEvent *) event);
+
+        if (prev_pos) {
+            Geom::Coord dist = Geom::L2(event_pos - *prev_pos);
+            guint32 delta_t = event_t - prev_time;
+            gdouble speed = delta_t > 0 ? dist / delta_t : 1000;
+            //std::cout << "Mouse speed = " << speed << " px/msec " << std::endl;
+            if (speed > 0.02) { // Jitter threshold, might be needed for tablets
+                // We're moving fast, so postpone any snapping until the next GDK_MOTION_NOTIFY event. We
+                // will keep on postponing the snapping as long as the speed is high.
+                // We must snap at some point in time though, so set a watchdog timer at some time from
+                // now, just in case there's no future motion event that drops under the speed limit (when
+                // stopping abruptly)
+                delete ec->_delayed_snap_event;
+                ec->_delayed_snap_event = new DelayedSnapEvent(ec, dse_item, dse_item2, event, origin); // watchdog is reset, i.e. pushed forward in time
+                // If the watchdog expires before a new motion event is received, we will snap (as explained
+                // above). This means however that when the timer is too short, we will always snap and that the
+                // speed threshold is ineffective. In the extreme case the delay is set to zero, and snapping will
+                // be immediate, as it used to be in the old days ;-).
+            } else { // Speed is very low, so we're virtually at stand still
+                // But if we're really standing still, then we should snap now. We could use some low-pass filtering,
+                // otherwise snapping occurs for each jitter movement. For this filtering we'll leave the watchdog to expire,
+                // snap, and set a new watchdog again.
+                if (ec->_delayed_snap_event == nullptr) { // no watchdog has been set
+                    // it might have already expired, so we'll set a new one; the snapping frequency will be limited this way
+                    ec->_delayed_snap_event = new DelayedSnapEvent(ec, dse_item, dse_item2, event, origin);
+                } // else: watchdog has been set before and we'll wait for it to expire
+            }
+        } else {
+            // This is the first GDK_MOTION_NOTIFY event, so postpone snapping and set the watchdog
+            g_assert(ec->_delayed_snap_event == nullptr);
+            ec->_delayed_snap_event = new DelayedSnapEvent(ec, dse_item, dse_item2, event, origin);
+        }
+
+        prev_pos = event_pos;
+        prev_time = event_t;
+    }
+}
+
+/**
+ * When the snap delay watchdog timer barks, this method will be called and will re-inject the last motion
+ * event in an appropriate place, with snapping being turned on again.
+ */
+gboolean sp_event_context_snap_watchdog_callback(gpointer data) {
+    // Snap NOW! For this the "postponed" flag will be reset and the last motion event will be repeated
+    DelayedSnapEvent *dse = reinterpret_cast<DelayedSnapEvent*> (data);
+
+    if (dse == nullptr) {
+        // This might occur when this method is called directly, i.e. not through the timer
+        // E.g. on GDK_BUTTON_RELEASE in start_root_handler()
+        return FALSE;
+    }
+
+    ToolBase *ec = dse->getEventContext();
+    if (ec == nullptr) {
+        delete dse;
+        return false;
+    }
+
+    const SPDesktop *dt = ec->getDesktop();
+    if (dt == nullptr) {
+        ec->_delayed_snap_event = nullptr;
+        delete dse;
+        return false;
+    }
+
+    ec->_dse_callback_in_process = true;
+
+    dt->namedview->snap_manager.snapprefs.setSnapPostponedGlobally(false);
+
+    // Depending on where the delayed snap event originated from, we will inject it back at it's origin
+    // The switch below takes care of that and prepares the relevant parameters
+    switch (dse->getOrigin()) {
+    case DelayedSnapEvent::EVENTCONTEXT_ROOT_HANDLER:
+        ec->tool_root_handler(dse->getEvent());
+        break;
+    case DelayedSnapEvent::EVENTCONTEXT_ITEM_HANDLER: {
+        auto item = static_cast<SPItem *>(dse->getItem());
+        if (item) {
+            ec->virtual_item_handler(item, dse->getEvent());
+        }
+    }
+        break;
+    case DelayedSnapEvent::KNOT_HANDLER: {
+        gpointer knot = dse->getItem2();
+        check_if_knot_deleted(knot);
+        if (knot && SP_IS_KNOT(knot)) {
+            bool was_grabbed = SP_KNOT(knot)->is_grabbed();
+            SP_KNOT(knot)->setFlag(SP_KNOT_GRABBED, true); // Must be grabbed for Inkscape::SelTrans::handleRequest() to pass
+            sp_knot_handler_request_position(dse->getEvent(), SP_KNOT(knot));
+            SP_KNOT(knot)->setFlag(SP_KNOT_GRABBED, was_grabbed);
+        }
+    }
+        break;
+    case DelayedSnapEvent::CONTROL_POINT_HANDLER: {
+        using Inkscape::UI::ControlPoint;
+        gpointer pitem2 = dse->getItem2();
+        if (!pitem2)
+        {
+            ec->_delayed_snap_event = nullptr;
+            delete dse;
+            return false;
+        }
+        ControlPoint *point = reinterpret_cast<ControlPoint*> (pitem2);
+        if (point) {
+            if (point->position().isFinite() && (dt == point->_desktop)) {
+                point->_eventHandler(ec, dse->getEvent());
+            }
+            else {
+                //workaround:
+                //[Bug 781893] Crash after moving a Bezier node after Knot path effect?
+                // --> at some time, some point with X = 0 and Y = nan (not a number) is created ...
+                //     even so, the desktop pointer is invalid and equal to 0xff
+                g_warning ("encountered non finite point when evaluating snapping callback");
+            }
+        }
+    }
+        break;
+    case DelayedSnapEvent::GUIDE_HANDLER: {
+        auto item  = static_cast<CanvasItemGuideLine *>(dse->getItem());
+        auto item2 = static_cast<SPGuide *>(dse->getItem2());
+        if (item && item2) {
+            sp_dt_guide_event(dse->getEvent(), item, item2);
+        }
+    }
+        break;
+    case DelayedSnapEvent::GUIDE_HRULER:
+    case DelayedSnapEvent::GUIDE_VRULER: {
+        gpointer item = dse->getItem();
+        auto item2 = static_cast<Gtk::Widget *>(dse->getItem2());
+        if (item && item2) {
+            g_assert(GTK_IS_WIDGET(item));
+            if (dse->getOrigin() == DelayedSnapEvent::GUIDE_HRULER) {
+                SPDesktopWidget::ruler_event(GTK_WIDGET(item), dse->getEvent(), SP_DESKTOP_WIDGET(item2), true);
+            } else {
+                SPDesktopWidget::ruler_event(GTK_WIDGET(item), dse->getEvent(), SP_DESKTOP_WIDGET(item2), false);
+            }
+        }
+    }
+        break;
+    default:
+        g_warning("Origin of snap-delay event has not been defined!;");
+        break;
+    }
+
+    ec->_delayed_snap_event = nullptr;
+    delete dse;
+
+    ec->_dse_callback_in_process = false;
+
+    return FALSE; //Kills the timer and stops it from executing this callback over and over again.
+}
+
+void ToolBase::discard_delayed_snap_event()
+{
+    delete _delayed_snap_event;
+    _delayed_snap_event = nullptr;
+    _desktop->namedview->snap_manager.snapprefs.setSnapPostponedGlobally(false);
+}
+}
+}
+}
+
+/*
+ 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 :