calligraphic-tool.cpp

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Handwriting-like drawing mode
 *
 * Authors:
 *   Mitsuru Oka <oka326@parkcity.ne.jp>
 *   Lauris Kaplinski <lauris@kaplinski.com>
 *   bulia byak <buliabyak@users.sf.net>
 *   MenTaLguY <mental@rydia.net>
 *   Abhishek Sharma
 *   Jon A. Cruz <jon@joncruz.org>
 *
 * The original dynadraw code:
 *   Paul Haeberli <paul@sgi.com>
 *
 * Copyright (C) 1998 The Free Software Foundation
 * Copyright (C) 1999-2005 authors
 * Copyright (C) 2001-2002 Ximian, Inc.
 * Copyright (C) 2005-2007 bulia byak
 * Copyright (C) 2006 MenTaLguY
 *
 * Released under GNU GPL v2+, read the file 'COPYING' for more information.
 */
 
#include "ui/tools/calligraphic-tool.h"
 
#include <cstring>
#include <numeric>
#include <string>
#include <random>
 
#include <gdk/gdkkeysyms.h>
#include <glibmm/i18n.h>
#include <gtk/gtk.h>
 
#include <2geom/bezier-utils.h>
#include <2geom/circle.h>
#include <2geom/pathvector.h>
 
#include "context-fns.h"
#include "desktop-events.h"
#include "desktop-style.h"
#include "desktop.h"
#include "document-undo.h"
#include "document.h"
#include "message-context.h"
#include "selection.h"
 
#include "display/control/canvas-item-bpath.h"
#include "display/control/canvas-item-drawing.h" // ctx
#include "display/curve.h"
#include "display/drawing.h"
 
#include "livarot/Path.h"
 
#include "object/sp-shape.h"
#include "object/sp-text.h"
 
#include "path/path-util.h"
 
#include "svg/svg.h"
 
#include "ui/icon-names.h"
#include "ui/tools/freehand-base.h"
#include "ui/widget/canvas.h"
#include "ui/widget/events/canvas-event.h"
 
#include "util/units.h"
 
using Inkscape::DocumentUndo;
using Inkscape::Util::Quantity;
using Inkscape::Util::Unit;
 
static constexpr double DDC_MIN_PRESSURE     = 0.0;
static constexpr double DDC_MAX_PRESSURE     = 1.0;
static constexpr double DDC_DEFAULT_PRESSURE = 1.0;
 
static constexpr double DDC_MIN_TILT     = -1.0;
static constexpr double DDC_MAX_TILT     =  1.0;
static constexpr double DDC_DEFAULT_TILT =  0.0;
 
static constexpr uint32_t DDC_RED_RGBA = 0xff0000ff;
 
static constexpr double TOLERANCE_CALLIGRAPHIC = 0.1;
 
static constexpr double DYNA_EPSILON = 0.5e-6;
static constexpr double DYNA_EPSILON_START = 0.5e-2;
static constexpr double DYNA_VEL_START = 1e-5;
 
static constexpr bool DYNA_DRAW_VERBOSE = false;
 
namespace Inkscape::UI::Tools {
 
CalligraphicTool::CalligraphicTool(SPDesktop *desktop)
    : DynamicBase(desktop, "/tools/calligraphic", "calligraphy.svg")
{
    currentshape = make_canvasitem<CanvasItemBpath>(desktop->getCanvasSketch());
    currentshape->set_stroke(0x0);
    currentshape->set_fill(DDC_RED_RGBA, SP_WIND_RULE_EVENODD);
 
    // Fixme: Can't we cascade it to root more clearly?
    currentshape->connect_event(sigc::bind(sigc::ptr_fun(sp_desktop_root_handler), desktop));
 
    hatch_area = make_canvasitem<CanvasItemBpath>(desktop->getCanvasControls());
    hatch_area->set_fill(0x0, SP_WIND_RULE_EVENODD);
    hatch_area->set_stroke(0x0000007f);
    hatch_area->set_pickable(false);
    hatch_area->set_visible(false);
 
    sp_event_context_read(this, "mass");
    sp_event_context_read(this, "wiggle");
    sp_event_context_read(this, "angle");
    sp_event_context_read(this, "width");
    sp_event_context_read(this, "thinning");
    sp_event_context_read(this, "tremor");
    sp_event_context_read(this, "flatness");
    sp_event_context_read(this, "tracebackground");
    sp_event_context_read(this, "usepressure");
    sp_event_context_read(this, "usetilt");
    sp_event_context_read(this, "abs_width");
    sp_event_context_read(this, "keep_selected");
    sp_event_context_read(this, "cap_rounding");
 
    auto prefs = Preferences::get();
    if (prefs->getBool("/tools/calligraphic/selcue")) {
        enableSelectionCue();
    }
}
 
void CalligraphicTool::set(Preferences::Entry const &val)
{
    auto const path = val.getEntryName();
 
    if (path == "tracebackground") {
        trace_bg = val.getBool();
    } else if (path == "keep_selected") {
        keep_selected = val.getBool();
    } else {
        // Pass on up to parent class to handle common attributes.
        DynamicBase::set(val);
    }
}
 
void CalligraphicTool::reset(Geom::Point const &p)
{
    last = cur = getNormalizedPoint(p);
 
    vel = {};
    vel_max = 0.0;
    acc = {};
    ang = {};
    del = {};
}
 
void CalligraphicTool::extinput(ExtendedInput const &ext)
{
    if (ext.pressure) {
        pressure = std::clamp(*ext.pressure, DDC_MIN_PRESSURE, DDC_MAX_PRESSURE);
    } else {
        pressure = DDC_DEFAULT_PRESSURE;
    }
 
    if (ext.xtilt) {
        xtilt = std::clamp(*ext.xtilt, DDC_MIN_TILT, DDC_MAX_TILT);
    } else {
        xtilt = DDC_DEFAULT_TILT;
    }
 
    if (ext.ytilt) {
        ytilt = std::clamp(*ext.ytilt, DDC_MIN_TILT, DDC_MAX_TILT);
    } else {
        ytilt = DDC_DEFAULT_TILT;
    }
}
 
static Geom::Point unsnapped_polar(double angle)
{
    Geom::Point v;
    Geom::sincos(angle, v.y(), v.x());
    return v;
}
 
bool CalligraphicTool::apply(Geom::Point const &p)
{
    auto const n = getNormalizedPoint(p);
 
    // Calculate mass and drag.
    double const mass_scaled = Geom::lerp(mass, 1.0, 160.0);
    double const drag_scaled = Geom::lerp(drag * drag, 0.0, 0.5);
 
    // Calculate force and acceleration.
    auto const force = n - cur;
 
    // If force is below the absolute threshold DYNA_EPSILON,
    // or we haven't yet reached DYNA_VEL_START (i.e. at the beginning of stroke)
    // _and_ the force is below the (higher) DYNA_EPSILON_START threshold,
    // discard this move.
    // This prevents flips, blobs, and jerks caused by microscopic tremor of the tablet pen,
    // especially bothersome at the start of the stroke where we don't yet have the inertia to
    // smooth them out.
    if (Geom::L2(force) < DYNA_EPSILON || (vel_max < DYNA_VEL_START && Geom::L2(force) < DYNA_EPSILON_START)) {
        return false;
    }
 
    acc = force / mass_scaled;
 
    // Calculate new velocity.
    vel += acc;
 
    vel_max = std::max(vel_max, Geom::L2(vel));
 
    // Calculate angle of drawing tool.
 
    double a1;
    if (usetilt) {
        // 1a. calculate nib angle from input device tilt:
        if (xtilt == 0 && ytilt == 0) {
            // to be sure that atan2 in the computation below
            // would not crash or return NaN.
            a1 = 0;
        } else {
            auto dir = Geom::Point(-xtilt, ytilt);
            a1 = atan2(dir);
        }
    } else {
        // 1b. fixed dc->angle (absolutely flat nib):
        a1 = Geom::rad_from_deg(angle);
    }
    a1 *= -_desktop->yaxisdir();
    if (flatness < 0.0) {
        // flips direction. Useful when this->usetilt
        // allows simulating both pen and calligraphic brush
        a1 *= -1;
    }
    a1 = std::fmod(a1, M_PI);
    if (a1 > 0.5 * M_PI) {
        a1 -= M_PI;
    } else if (a1 <= -0.5 * M_PI) {
        a1 += M_PI;
    }
 
    // 2. perpendicular to dc->vel (absolutely non-flat nib):
    double const mag_vel = Geom::L2(vel);
    if (mag_vel < DYNA_EPSILON) {
        return false;
    }
    auto const ang2 = Geom::rot90(vel) / mag_vel;
 
    // 3. Average them using flatness parameter:
    // calculate angles
    double a2 = atan2(ang2);
    // flip a2 to force it to be in the same half-circle as a1
    bool flipped = false;
    if (std::abs(a2 - a1) > 0.5 * M_PI) {
        a2 += M_PI;
        flipped = true;
    }
    // normalize a2
    if (a2 > M_PI) {
        a2 -= 2 * M_PI;
    } else if (a2 < -M_PI) {
        a2 += 2 * M_PI;
    }
    // find the flatness-weighted bisector angle, unflip if a2 was flipped
    // FIXME: when dc->vel is oscillating around the fixed angle, the new_ang flips back and forth. How to avoid this?
    double new_ang = a1 + (1 - std::abs(flatness)) * (a2 - a1) - (flipped ? M_PI : 0);
    // Try to detect a sudden flip when the new angle differs too much from the previous for the
    // current velocity; in that case discard this move
    auto const new_ang_vec = unsnapped_polar(new_ang);
    double angle_delta = Geom::L2(new_ang_vec - ang);
    if (angle_delta / Geom::L2(vel) > 4000) {
        return false;
    }
 
    // convert to point
    ang = new_ang_vec;
 
    if constexpr (false) g_print("force %g  acc %g  vel_max %g  vel %g  a1 %g  a2 %g  new_ang %g\n", Geom::L2(force), Geom::L2(acc), vel_max, Geom::L2(vel), a1, a2, new_ang);
 
    // Apply drag
    vel *= 1.0 - drag_scaled;
 
    // Update position
    last = cur;
    cur += vel;
 
    return true;
}
 
void CalligraphicTool::brush()
{
    g_assert(npoints >= 0 && npoints < SAMPLING_SIZE);
 
    // How much velocity thins strokestyle
    double const vel_thin_scaled = Geom::lerp(vel_thin, 0, 160);
 
    // Influence of pressure on thickness
    double const pressure_thick = usepressure ? pressure : 1.0;
 
    // get the real brush point, not the same as pointer (affected by hatch tracking and/or mass drag)
    auto const brush = getViewPoint(cur);
    auto const brush_w = _desktop->d2w(brush);
 
    double trace_thick = 1;
    if (trace_bg) {
        // Trace background, use single pixel under brush.
        auto const area = Geom::IntRect::from_xywh(brush_w.floor(), Geom::IntPoint(1, 1));
 
        auto const canvas_item_drawing = _desktop->getCanvasDrawing();
        auto const drawing = canvas_item_drawing->get_drawing();
 
        // Get average color.
        auto avg = drawing->averageColor(area);
        auto A = avg.stealOpacity();
 
        // Convert to thickness.
        std::vector<double> vals = avg.getValues();
        double max = std::max({vals[0], vals[1], vals[2]});
        double min = std::min({vals[0], vals[1], vals[2]});
        double const L = A * (max + min) / 2 + (1 - A); // blend with white bg
        trace_thick = 1 - L;
        if constexpr(false) g_print("L %g thick %g\n", L, trace_thick);
    }
 
    double width_adjusted = (pressure_thick * trace_thick - vel_thin_scaled * vel.length()) * width;
 
    double tremble_left = 0, tremble_right = 0;
    if (tremor > 0) {
        auto gen = std::default_random_engine(g_random_int());
        auto nrm = std::normal_distribution();
 
        // deflect both left and right edges randomly and independently, so that:
        // (1) dc->tremor=1 corresponds to sigma=1, decreasing dc->tremor narrows the bell curve;
        // (2) deflection depends on width, but is upped for small widths for better visual uniformity across widths;
        // (3) deflection somewhat depends on speed, to prevent fast strokes looking
        // comparatively smooth and slow ones excessively jittery
        auto const sigma = tremor * (0.15 + 0.8 * width_adjusted) * (0.35 + 14 * vel.length());
        tremble_left  = nrm(gen) * sigma;
        tremble_right = nrm(gen) * sigma;
    }
 
    width_adjusted = std::max(width_adjusted, 0.02 * width);
 
    double dezoomify_factor = 0.05 * 1000;
    if (!abs_width) {
        dezoomify_factor /= _desktop->current_zoom();
    }
 
    auto const del_left = dezoomify_factor * (width_adjusted + tremble_left) * ang;
    auto const del_right = dezoomify_factor * (width_adjusted + tremble_right) * ang;
 
    point1[npoints] = brush + del_left;
    point2[npoints] = brush - del_right;
 
    del = 0.5 * (del_left + del_right);
 
    npoints++;
}
 
void CalligraphicTool::cancel()
{
    dragging = false;
    is_drawing = false;
 
    ungrabCanvasEvents();
 
    // Remove all temporary line segments.
    segments.clear();
 
    // Reset accumulated curve.
    accumulated.reset();
    clear_current();
 
    repr = nullptr;
}
 
bool CalligraphicTool::root_handler(CanvasEvent const &event)
{
    bool ret = false;
 
    auto prefs = Preferences::get();
    auto unit = Util::UnitTable::get().getUnit(prefs->getString("/tools/calligraphic/unit"));
 
    inspect_event(event,
        [&] (ButtonPressEvent const &event) {
            if (event.num_press == 1 && event.button == 1) {
                if (!have_viable_layer(_desktop, defaultMessageContext())) {
                    ret = true;
                    return;
                }
 
                accumulated.reset();
 
                repr = nullptr;
 
                // initialize first point
                npoints = 0;
 
                grabCanvasEvents();
 
                ret = true;
 
                set_high_motion_precision();
                is_drawing = true;
                just_started_drawing = true;
            }
        },
 
        [&] (MotionEvent const &event) {
            auto motion_dt = _desktop->w2d(event.pos);
            extinput(event.extinput);
 
            message_context->clear();
 
            // for hatching:
            double hatch_dist = 0;
            Geom::Point hatch_unit_vector;
            Geom::Point nearest;
            Geom::Point pointer;
            Geom::Affine motion_to_curve;
 
            if (event.modifiers & GDK_CONTROL_MASK) { // hatching - sense the item
 
                auto const selected = _desktop->getSelection()->singleItem();
                if (selected && (is<SPShape>(selected) || is<SPText>(selected))) {
                    // One item selected, and it's a path;
                    // let's try to track it as a guide
 
                    if (selected != hatch_item) {
                        hatch_item = selected;
                        hatch_livarot_path = Path_for_item(hatch_item, true, true);
                        if (hatch_livarot_path) {
                            hatch_livarot_path->ConvertWithBackData(0.01);
                        }
                    }
 
                    // calculate pointer point in the guide item's coords
                    motion_to_curve = selected->dt2i_affine() * selected->i2doc_affine();
                    pointer = motion_dt * motion_to_curve;
 
                    // calculate the nearest point on the guide path
                    std::optional<Path::cut_position> position = get_nearest_position_on_Path(hatch_livarot_path.get(), pointer);
                    if (position) {
                        nearest = get_point_on_Path(hatch_livarot_path.get(), position->piece, position->t);
 
                        // distance from pointer to nearest
                        hatch_dist = Geom::L2(pointer - nearest);
                        // unit-length vector
                        hatch_unit_vector = (pointer - nearest) / hatch_dist;
 
                        message_context->set(Inkscape::NORMAL_MESSAGE, _("<b>Guide path selected</b>; start drawing along the guide with <b>Ctrl</b>"));
                    }
                } else {
                    message_context->set(Inkscape::NORMAL_MESSAGE, _("<b>Select a guide path</b> to track with <b>Ctrl</b>"));
                }
            }
 
            if (is_drawing && (event.modifiers & GDK_BUTTON1_MASK)) {
                dragging = true;
 
                if (event.modifiers & GDK_CONTROL_MASK && hatch_item) { // hatching
 
                    constexpr auto HATCH_VECTOR_ELEMENTS = 12;
                    constexpr auto INERTIA_ELEMENTS = 24;
                    constexpr auto SPEED_ELEMENTS = 12;
                    constexpr auto SPEED_MIN = 0.3;
                    constexpr auto SPEED_NORMAL = 0.35;
                    constexpr auto INERTIA_FORCE = 0.5;
 
                    // speed is the movement of the nearest point along the guide path, divided by
                    // the movement of the pointer at the same period; it is averaged for the last
                    // SPEED_ELEMENTS motion events.  Normally, as you track the guide path, speed
                    // is about 1, i.e. the nearest point on the path is moved by about the same
                    // distance as the pointer. If the speed starts to decrease, we are losing
                    // contact with the guide; if it drops below SPEED_MIN, we are on our own and
                    // not attracted to guide anymore. Most often this happens when you have
                    // tracked to the end of a guide calligraphic stroke and keep moving
                    // further. We try to handle this situation gracefully: not stick with the
                    // guide forever but let go of it smoothly and without sharp jerks (non-zero
                    // mass recommended; with zero mass, jerks are still quite noticeable).
 
                    double speed = 1;
                    if (Geom::L2(hatch_last_nearest) != 0) {
                        // the distance nearest moved since the last motion event
                        double nearest_moved = Geom::L2(nearest - hatch_last_nearest);
                        // the distance pointer moved since the last motion event
                        double pointer_moved = Geom::L2(pointer - hatch_last_pointer);
 
                        // store them in stacks limited to SPEED_ELEMENTS
                        hatch_nearest_past.push_front(nearest_moved);
                        if (hatch_nearest_past.size() > SPEED_ELEMENTS) {
                            hatch_nearest_past.pop_back();
                        }
                        hatch_pointer_past.push_front(pointer_moved);
                        if (hatch_pointer_past.size() > SPEED_ELEMENTS) {
                            hatch_pointer_past.pop_back();
                        }
 
                        // If the stacks are full,
                        if (hatch_nearest_past.size() == SPEED_ELEMENTS) {
                            // calculate the sums of all stored movements
                            double nearest_sum = std::accumulate(hatch_nearest_past.begin(), hatch_nearest_past.end(), 0.0);
                            double pointer_sum = std::accumulate(hatch_pointer_past.begin(), hatch_pointer_past.end(), 0.0);
                            // and divide to get the speed
                            speed = nearest_sum/pointer_sum;
                            if constexpr (false) g_print("nearest sum %g  pointer_sum %g  speed %g\n", nearest_sum, pointer_sum, speed);
                        }
                    }
 
                    if (   hatch_escaped  // already escaped, do not reattach
                        || speed < SPEED_MIN // stuck; most likely reached end of traced stroke
                        || (hatch_spacing > 0 && hatch_dist > 50 * hatch_spacing) // went too far from the guide
                        )
                    {
                        // We are NOT attracted to the guide!
 
                        // Remember hatch_escaped so we don't get
                        // attracted again until the end of this stroke
                        hatch_escaped = true;
 
                        if (inertia_vectors.size() >= INERTIA_ELEMENTS / 2) { // move by inertia
                            auto const moved_past_escape = motion_dt - inertia_vectors.front();
                            auto const inertia =  inertia_vectors.front() - inertia_vectors.back();
 
                            double dot = Geom::dot(moved_past_escape, inertia);
                            dot /= moved_past_escape.length() * inertia.length();
 
                            if (dot > 0) { // mouse is still moving in approx the same direction
                                auto const should_have_moved = inertia.normalized() * moved_past_escape.length();
                                motion_dt = inertia_vectors.front() + Geom::lerp(INERTIA_FORCE, moved_past_escape, should_have_moved);
                            }
                        }
 
                    } else {
 
                        // Calculate angle cosine of this vector-to-guide and all past vectors
                        // summed, to detect if we accidentally flipped to the other side of the guide
                        auto const hatch_vector_accumulated = std::accumulate(hatch_vectors.begin(), hatch_vectors.end(), Geom::Point());
                        double dot = Geom::dot(pointer - nearest, hatch_vector_accumulated);
                        dot /= Geom::L2(pointer - nearest) * Geom::L2(hatch_vector_accumulated);
 
                        if (hatch_spacing != 0) { // spacing was already set
                            double target;
                            if (speed > SPEED_NORMAL) {
                                // all ok, strictly obey the spacing
                                target = hatch_spacing;
                            } else {
                                // looks like we're starting to lose speed,
                                // so _gradually_ let go attraction to prevent jerks
                                target = (hatch_spacing * speed + hatch_dist * (SPEED_NORMAL - speed)) / SPEED_NORMAL;
                            }
                            if (!std::isnan(dot) && dot < -0.5) { // flip
                                target = -target;
                            }
 
                            // This is the track pointer that we will use instead of the real one
                            auto const new_pointer = nearest + target * hatch_unit_vector;
 
                            // some limited feedback: allow persistent pulling to slightly change
                            // the spacing
                            hatch_spacing += (hatch_dist - hatch_spacing) / 3500;
 
                            // return it to the desktop coords
                            motion_dt = new_pointer * motion_to_curve.inverse();
 
                            if (speed >= SPEED_NORMAL) {
                                inertia_vectors.push_front(motion_dt);
                                if (inertia_vectors.size() > INERTIA_ELEMENTS) {
                                    inertia_vectors.pop_back();
                                }
                            }
 
                        } else {
                            // this is the first motion event, set the dist
                            hatch_spacing = hatch_dist;
                        }
 
                        // remember last points
                        hatch_last_pointer = pointer;
                        hatch_last_nearest = nearest;
 
                        hatch_vectors.push_front(pointer - nearest);
                        if (hatch_vectors.size() > HATCH_VECTOR_ELEMENTS) {
                            hatch_vectors.pop_back();
                        }
                    }
 
                    message_context->set(Inkscape::NORMAL_MESSAGE, hatch_escaped? _("Tracking: <b>connection to guide path lost!</b>") : _("<b>Tracking</b> a guide path"));
 
                } else {
                    message_context->set(Inkscape::NORMAL_MESSAGE, _("<b>Drawing</b> a calligraphic stroke"));
                }
 
                if (just_started_drawing) {
                    just_started_drawing = false;
                    reset(motion_dt);
                }
 
                if (!apply(motion_dt)) {
                    ret = true;
                    return;
                }
 
                if (cur != last) {
                    brush();
                    g_assert(npoints > 0);
                    fit_and_split(false);
                }
                ret = true;
            }
 
            Geom::PathVector path = Geom::Path(Geom::Circle(0,0,1)); // Unit circle centered at origin.
 
            // Draw the hatching circle if necessary
            if (event.modifiers & GDK_CONTROL_MASK) {
                if (hatch_spacing == 0 && hatch_dist != 0) {
                    // Haven't set spacing yet: gray, center free, update radius live
 
                    auto const c = _desktop->w2d(event.pos);
                    path *= Geom::Scale(hatch_dist) * Geom::Translate(c);
 
                    hatch_area->set_bpath(std::move(path), true);
                    hatch_area->set_stroke(0x7f7f7fff);
                    hatch_area->set_visible(true);
 
                } else if (dragging && !hatch_escaped && hatch_dist != 0) {
                    // Tracking: green, center snapped, fixed radius
 
                    auto const c = motion_dt;
                    path *= Geom::Scale(hatch_spacing) * Geom::Translate(c);
 
                    hatch_area->set_bpath(std::move(path), true);
                    hatch_area->set_stroke(0x00ff00ff);
                    hatch_area->set_visible(true);
 
                } else if (dragging && hatch_escaped && hatch_dist != 0) {
                    // Tracking escaped: red, center free, fixed radius
 
                    auto const c = motion_dt;
                    path *= Geom::Scale(hatch_spacing) * Geom::Translate(c);
 
                    hatch_area->set_bpath(std::move(path), true);
                    hatch_area->set_stroke(0xff0000ff);
                    hatch_area->set_visible(true);
 
                } else {
                    // Not drawing but spacing set: gray, center snapped, fixed radius
 
                    auto const c = (nearest + hatch_spacing * hatch_unit_vector) * motion_to_curve.inverse();
                    if (!std::isnan(c.x()) && !std::isnan(c.y()) && hatch_spacing != 0) {
                        path *= Geom::Scale(hatch_spacing) * Geom::Translate(c);
 
                        hatch_area->set_bpath(std::move(path), true);
                        hatch_area->set_stroke(0x7f7f7fff);
                        hatch_area->set_visible(true);
                    }
                }
            } else {
                hatch_area->set_visible(false);
            }
        },
 
    [&] (ButtonReleaseEvent const &event) {
        auto const motion_dt = _desktop->w2d(event.pos);
 
        ungrabCanvasEvents();
 
        set_high_motion_precision(false);
        is_drawing = false;
 
        if (dragging && event.button == 1) {
            dragging = false;
 
            apply(motion_dt);
 
            // Remove all temporary line segments.
            segments.clear();
 
            // Create object
            fit_and_split(true);
            if (accumulate()) {
                set_to_accumulated(event.modifiers & GDK_SHIFT_MASK, event.modifiers & GDK_ALT_MASK); // performs document_done
            } else {
                g_warning("Failed to create path: invalid data in dc->cal1 or dc->cal2");
            }
 
            // Reset accumulated curve.
            accumulated.reset();
 
            clear_current();
            repr = nullptr;
 
            hatch_pointer_past.clear();
            hatch_nearest_past.clear();
            inertia_vectors.clear();
            hatch_vectors.clear();
            hatch_last_nearest = {};
            hatch_last_pointer = {};
            hatch_escaped = false;
            hatch_item = nullptr;
            hatch_livarot_path.reset();
            just_started_drawing = false;
 
            if (hatch_spacing != 0 && !keep_selected) {
                // we do not select the newly drawn path, so increase spacing by step
                if (hatch_spacing_step == 0) {
                    hatch_spacing_step = hatch_spacing;
                }
                hatch_spacing += hatch_spacing_step;
            }
 
            message_context->clear();
            ret = true;
        } else if (!dragging
                   && event.button == 1
                   && have_viable_layer(_desktop, defaultMessageContext()))
        {
            spdc_create_single_dot(this, _desktop->w2d(event.pos), "/tools/calligraphic", event.modifiers);
            ret = true;
        }
    },
 
    [&] (KeyPressEvent const &event) {
        switch (get_latin_keyval(event)) {
        case GDK_KEY_Up:
        case GDK_KEY_KP_Up:
            if (!mod_ctrl_only(event)) {
                angle = std::min(angle + 5.0, 90.0);
                _desktop->setToolboxAdjustmentValue("calligraphy-angle", angle);
                ret = true;
            }
            break;
        case GDK_KEY_Down:
        case GDK_KEY_KP_Down:
            if (!mod_ctrl_only(event)) {
                angle = std::max(angle - 5.0, -90.0);
                _desktop->setToolboxAdjustmentValue("calligraphy-angle", angle);
                ret = true;
            }
            break;
        case GDK_KEY_Right:
        case GDK_KEY_KP_Right:
            if (!mod_ctrl_only(event)) {
                width = Quantity::convert(width, "px", unit);
                width = std::min(width + 0.01, 1.0);
                _desktop->setToolboxAdjustmentValue("calligraphy-width", width * 100); // the same spinbutton is for alt+x
                ret = true;
            }
            break;
        case GDK_KEY_Left:
        case GDK_KEY_KP_Left:
            if (!mod_ctrl_only(event)) {
                width = Quantity::convert(width, "px", unit);
                width = std::max(width - 0.01, 0.00001);
                _desktop->setToolboxAdjustmentValue("calligraphy-width", width * 100);
                ret = true;
            }
            break;
        case GDK_KEY_Home:
        case GDK_KEY_KP_Home:
            width = 0.00001;
            _desktop->setToolboxAdjustmentValue("calligraphy-width", width * 100);
            ret = true;
            break;
        case GDK_KEY_End:
        case GDK_KEY_KP_End:
            width = 1.0;
            _desktop->setToolboxAdjustmentValue("calligraphy-width", width * 100);
            ret = true;
            break;
        case GDK_KEY_x:
        case GDK_KEY_X:
            if (mod_alt_only(event)) {
                _desktop->setToolboxFocusTo("calligraphy-width");
                ret = true;
            }
            break;
        case GDK_KEY_Escape:
            if (is_drawing) {
                // if drawing, cancel, otherwise pass it up for deselecting
                cancel();
                ret = true;
            }
            break;
        case GDK_KEY_z:
        case GDK_KEY_Z:
            if (mod_ctrl_only(event) && is_drawing) {
                // if drawing, cancel, otherwise pass it up for undo
                cancel();
                ret = true;
            }
            break;
        default:
            break;
        }
    },
 
    [&] (KeyReleaseEvent const &event) {
        switch (get_latin_keyval(event)) {
            case GDK_KEY_Control_L:
            case GDK_KEY_Control_R:
                message_context->clear();
                hatch_spacing = 0;
                hatch_spacing_step = 0;
                break;
            default:
                break;
        }
    },
 
    [&] (CanvasEvent const &event) {}
    );
 
    return ret || DynamicBase::root_handler(event);
}
 
void CalligraphicTool::clear_current()
{
    // reset bpath
    currentshape->set_bpath(nullptr);
 
    // reset curve
    currentcurve.reset();
    cal1.reset();
    cal2.reset();
 
    // reset points
    npoints = 0;
}
 
void CalligraphicTool::set_to_accumulated(bool unionize, bool subtract) {
    if (!accumulated.is_empty()) {
        if (!repr) {
            /* Create object */
            Inkscape::XML::Document *xml_doc = _desktop->doc()->getReprDoc();
            Inkscape::XML::Node *repr = xml_doc->createElement("svg:path");
 
            /* Set style */
            sp_desktop_apply_style_tool(_desktop, repr, "/tools/calligraphic", false);
 
            this->repr = repr;
 
            auto layer = currentLayer();
            auto item = cast<SPItem>(layer->appendChildRepr(this->repr));
            Inkscape::GC::release(this->repr);
            item->transform = layer->i2doc_affine().inverse();
            item->updateRepr();
        }
 
        Geom::PathVector pathv = accumulated.get_pathvector() * _desktop->dt2doc();
        repr->setAttribute("d", sp_svg_write_path(pathv));
 
        if (unionize) {
            _desktop->getSelection()->add(this->repr);
            _desktop->getSelection()->pathUnion(true);
        } else if (subtract) {
            _desktop->getSelection()->add(this->repr);
            _desktop->getSelection()->pathDiff(true);
        } else {
            if (this->keep_selected) {
                _desktop->getSelection()->set(this->repr);
            }
        }
 
        // Now we need to write the transform information.
        // First, find out whether our repr is still linked to a valid object. In this case,
        // we need to write the transform data only for this element.
        // Either there was no boolean op or it failed.
        auto result = cast<SPItem>(_desktop->doc()->getObjectByRepr(this->repr));
 
        if (result == nullptr) {
            // The boolean operation succeeded.
            // Now we fetch the single item, that has been set as selected by the boolean op.
            // This is its result.
            result = _desktop->getSelection()->singleItem();
        }
        result->doWriteTransform(result->transform, nullptr, true);
    } else {
        if (this->repr) {
            sp_repr_unparent(this->repr);
        }
 
        this->repr = nullptr;
    }
 
    DocumentUndo::done(_desktop->getDocument(), _("Draw calligraphic stroke"), INKSCAPE_ICON("draw-calligraphic"));
}
 
static void
add_cap(SPCurve &curve,
        Geom::Point const &from,
        Geom::Point const &to,
        double rounding)
{
    if (Geom::L2( to - from ) > DYNA_EPSILON) {
        Geom::Point vel = rounding * Geom::rot90( to - from ) / sqrt(2.0);
        double mag = Geom::L2(vel);
 
        Geom::Point v = mag * Geom::rot90( to - from ) / Geom::L2( to - from );
        curve.curveto(from + v, to + v, to);
    }
}
 
bool CalligraphicTool::accumulate() {
    if (
        cal1.is_empty() ||
        cal2.is_empty() ||
        (cal1.get_segment_count() <= 0) ||
        cal1.first_path()->closed()
        ) {
 
        cal1.reset();
        cal2.reset();
 
        return false; // failure
    }
 
        auto rev_cal2 = cal2.reversed();
 
    if ((rev_cal2.get_segment_count() <= 0) || rev_cal2.first_path()->closed()) {
        cal1.reset();
        cal2.reset();
 
        return false; // failure
    }
 
    Geom::Curve const * dc_cal1_firstseg  = cal1.first_segment();
    Geom::Curve const * rev_cal2_firstseg = rev_cal2.first_segment();
    Geom::Curve const * dc_cal1_lastseg   = cal1.last_segment();
    Geom::Curve const * rev_cal2_lastseg  = rev_cal2.last_segment();
 
    accumulated.reset(); /*  Is this required ?? */
 
    accumulated.append(cal1);
 
    add_cap(accumulated, dc_cal1_lastseg->finalPoint(), rev_cal2_firstseg->initialPoint(), cap_rounding);
 
    accumulated.append(rev_cal2, true);
 
    add_cap(accumulated, rev_cal2_lastseg->finalPoint(), dc_cal1_firstseg->initialPoint(), cap_rounding);
 
    accumulated.closepath();
 
    cal1.reset();
    cal2.reset();
 
    return true; // success
}
 
void CalligraphicTool::fit_and_split(bool release)
{
    double const tolerance_sq = Geom::sqr(_desktop->w2d().descrim() * TOLERANCE_CALLIGRAPHIC);
 
    if constexpr (DYNA_DRAW_VERBOSE) {
        g_print("[F&S:R=%c]", release?'T':'F');
    }
 
    if (!( this->npoints > 0 && this->npoints < SAMPLING_SIZE )) {
        return; // just clicked
    }
 
    if ( this->npoints == SAMPLING_SIZE - 1 || release ) {
#define BEZIER_SIZE       4
#define BEZIER_MAX_BEZIERS  8
#define BEZIER_MAX_LENGTH ( BEZIER_SIZE * BEZIER_MAX_BEZIERS )
 
        if constexpr (DYNA_DRAW_VERBOSE) {
            g_print("[F&S:#] dc->npoints:%d, release:%s\n",
                    this->npoints, release ? "TRUE" : "FALSE");
        }
 
        /* Current calligraphic */
        if ( cal1.is_empty() || cal2.is_empty() ) {
            /* dc->npoints > 0 */
            /* g_print("calligraphics(1|2) reset\n"); */
            cal1.reset();
            cal2.reset();
 
            cal1.moveto(this->point1[0]);
            cal2.moveto(this->point2[0]);
        }
 
        Geom::Point b1[BEZIER_MAX_LENGTH];
        gint const nb1 = Geom::bezier_fit_cubic_r(b1, this->point1, this->npoints,
                                               tolerance_sq, BEZIER_MAX_BEZIERS);
        g_assert( nb1 * BEZIER_SIZE <= gint(G_N_ELEMENTS(b1)) );
 
        Geom::Point b2[BEZIER_MAX_LENGTH];
        gint const nb2 = Geom::bezier_fit_cubic_r(b2, this->point2, this->npoints,
                                               tolerance_sq, BEZIER_MAX_BEZIERS);
        g_assert( nb2 * BEZIER_SIZE <= gint(G_N_ELEMENTS(b2)) );
 
        if ( nb1 != -1 && nb2 != -1 ) {
            /* Fit and draw and reset state */
            if constexpr (DYNA_DRAW_VERBOSE) {
                g_print("nb1:%d nb2:%d\n", nb1, nb2);
            }
            /* CanvasShape */
            if (! release) {
                currentcurve.reset();
                currentcurve.moveto(b1[0]);
                for (Geom::Point *bp1 = b1; bp1 < b1 + BEZIER_SIZE * nb1; bp1 += BEZIER_SIZE) {
                    currentcurve.curveto(bp1[1], bp1[2], bp1[3]);
                }
                currentcurve.lineto(b2[BEZIER_SIZE*(nb2-1) + 3]);
                for (Geom::Point *bp2 = b2 + BEZIER_SIZE * ( nb2 - 1 ); bp2 >= b2; bp2 -= BEZIER_SIZE) {
                    currentcurve.curveto(bp2[2], bp2[1], bp2[0]);
                }
                // FIXME: dc->segments is always NULL at this point??
                if (this->segments.empty()) { // first segment
                    add_cap(currentcurve, b2[0], b1[0], cap_rounding);
                }
                currentcurve.closepath();
                currentshape->set_bpath(&currentcurve, true);
            }
 
            /* Current calligraphic */
            for (Geom::Point *bp1 = b1; bp1 < b1 + BEZIER_SIZE * nb1; bp1 += BEZIER_SIZE) {
                cal1.curveto(bp1[1], bp1[2], bp1[3]);
            }
            for (Geom::Point *bp2 = b2; bp2 < b2 + BEZIER_SIZE * nb2; bp2 += BEZIER_SIZE) {
                cal2.curveto(bp2[1], bp2[2], bp2[3]);
            }
        } else {
            /* fixme: ??? */
            if constexpr (DYNA_DRAW_VERBOSE) {
                g_print("[fit_and_split] failed to fit-cubic.\n");
            }
            this->draw_temporary_box();
 
            for (gint i = 1; i < this->npoints; i++) {
                cal1.lineto(this->point1[i]);
            }
            for (gint i = 1; i < this->npoints; i++) {
                cal2.lineto(this->point2[i]);
            }
        }
 
        /* Fit and draw and copy last point */
        if constexpr (DYNA_DRAW_VERBOSE) {
            g_print("[%d]Yup\n", this->npoints);
        }
        if (!release) {
            g_assert(!currentcurve.is_empty());
 
            auto fillColor = sp_desktop_get_color_tool(_desktop, "/tools/calligraphic", true);
            double opacity = sp_desktop_get_master_opacity_tool(_desktop, "/tools/calligraphic");
            double fillOpacity = sp_desktop_get_opacity_tool(_desktop, "/tools/calligraphic", true);
 
            // TODO: This removes color space information.
            auto cbp = new Inkscape::CanvasItemBpath(_desktop->getCanvasSketch(), currentcurve.get_pathvector(), true);
            cbp->set_fill(fillColor ? fillColor->toRGBA(opacity * fillOpacity) : 0x0, SP_WIND_RULE_EVENODD);
            cbp->set_stroke(0x0);
 
            /* fixme: Cannot we cascade it to root more clearly? */
            cbp->connect_event(sigc::bind(sigc::ptr_fun(sp_desktop_root_handler), _desktop));
 
            segments.emplace_back(cbp);
        }
 
        this->point1[0] = this->point1[this->npoints - 1];
        this->point2[0] = this->point2[this->npoints - 1];
        this->npoints = 1;
    } else {
        this->draw_temporary_box();
    }
}
 
void CalligraphicTool::draw_temporary_box() {
    currentcurve.reset();
 
    currentcurve.moveto(this->point2[this->npoints-1]);
 
    for (gint i = this->npoints-2; i >= 0; i--) {
        currentcurve.lineto(this->point2[i]);
    }
 
    for (gint i = 0; i < this->npoints; i++) {
        currentcurve.lineto(this->point1[i]);
    }
 
    if (this->npoints >= 2) {
        add_cap(currentcurve, point1[npoints - 1], point2[npoints - 1], cap_rounding);
    }
 
    currentcurve.closepath();
    currentshape->set_bpath(&currentcurve, true);
}
 
} // namespace Inkscape::UI::Tools
 
/*
  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 :