File indexing completed on 2024-04-21 15:23:39

 /********************************************************************************
  * Copyright (C) 2011-2015 by Stephen Allewell                                  *
  * steve.allewell@gmail.com                                                     *
  *                                                                              *
  * This program is free software; you can redistribute it and/or modify         *
  * it under the terms of the GNU General Public License as published by         *
  * the Free Software Foundation; either version 2 of the License, or            *
  * (at your option) any later version.                                          *
  ********************************************************************************/
 
 
 /**
  * @file
  * Implement the Editor class.
  */
 
 
 /**
  * @page editor_window Editor
  * The editor allows the user to create or modify the current symbol. It consists of a fixed size square grid
  * with several tools to create QPainterPath objects which will then be used to render the symbol. The QPainterPath
  * consists of one or more subpaths. Each subpath has a start point, which defaults to (0,0), but can be moved as
  * required. The various tools require one or more additional points to define the subpath. For each of the
  * tools used,the last point of the last tool becomes the first point of the next. Consequently all the individual
  * tools are joined together to create a single subpath. A new subpath can be started by using the move to option
  * to specify a new start point. Additionally the use of the rectangle and ellipse tools will create stand alone subpaths.
  *
  * The editor shows a green square which is the largest preferred size of the symbol. This allows some white space
  * around the symbol when it will be rendered in a pattern.
  *
  * When placing points, guide lines will be shown when the cursor is at a position that aligns with other
  * points either horizontally, vertically or at a range of predefined angles. The circle guides are created if the cursor
  * is at a position that aligns with another point on a circle where the center is at the center of the grid.
  * When a symbol shape is made up of a large number of points, the number of guide lines generated can be significant.
  * If these become a problem then the generation of the guide lines can be turned off completely or an option is
  * available in the configuration dialog to simplify the range of angles tested.
  *
  * @section editor_tools Editor Tools
  *
  * @subsection move_to Move To
  * Allows moving the start point of the current subpath. If the current subpath already has elements in
  * it, this effectively closes the current subpath and creates a new one.
  *
  * @subsection line_to Line To
  * Draws a line from the last point to the next selected point.
  *
  * @subsection cubic_to Cubic To
  * Draws a cubic spline consisting of a start point which will be the last point of the last command, two
  * control points and a finish point. The control points define the path of the curve between the start and end points.
  *
  * @subsection rectangle Rectangle
  * Draw a rectangle between two points. The points define the opposite corners of the rectangle. These can either
  * entered by clicking two points or clicking and dragging. When dragging, a rubber band rectangle will be shown
  * indicating the rectangle.
  *
  * @subsection ellipse Ellipse
  * Draw an ellipse between two points. The points define the opposite corners of a rectangle encompassing the
  * ellipse. As with the rectangle the points can be selected by clicking two points or clicking and dragging.
  * When dragging, a rubber band ellipse will be shown indicating the ellipse.
  *
  * @subsection character Insert Character
  * This will display a character selection dialog allowing selection of a character from any font to be inserted as a
  * symbol. Double click the required character which will then be converted to a symbol format in the editor. Further changes
  * can then be made to it as needed. This selection will replace any current symbol definition in the editor. The dialog
  * will remain open, allowing a select, save, repeat work flow rapidly building up a library of symbols.
  *
  * @subsection rotate_left Rotate Left
  * Rotate the symbol counter clockwise 90 degrees.
  *
  * @subsection rotate_right Rotate Right
  * Rotate the symbol clockwise 90 degrees.
  *
  * @subsection flip_horizontal Flip Horizontally
  * Flip the symbol horizontally about an axis passing vertically through the center of the grid.
  *
  * @subsection flip_vertical Flip Vertically
  * Flip the symbol vertically about an axis passing horizontally through the center of the grid.
  *
  * @subsection scale_preferred Scale to Preferred Size
  * Scale the existing symbol so that it fits within the preferred size square.
  *
  * @subsection snap_grid Snap to Grid
  * The selection of points can either be snapped to the grid or can be freely placed depending on if
  * the snap option is toggled on or off.
  *
  * @subsection guide_lines Enable Guide Lines
  * The generation of guide lines can be toggled on or off. As the number of points in a symbol increases
  * the number of guide lines that can be created can become significant at which point they become less
  * useful.
  *
  * @section path_rendering Path Rendering
  *
  * @subsection fill_mode Fill Mode
  * The defined path can either be set to filled or outline depending on if the fill mode is toggled
  * on or off.
  *
  * @subsection fill_rule Fill Rule
  * When filling is enabled the path will be filled. The rule defining the fill will be either Winding  of
  * Odd-Even.
  *
  * @par Winding
  * The winding rule will completely fill the objects boundary.
  *
  * @par Odd Even
  * The odd even rule will fill produce a checker board style fill where adjacent areas will be different
  * to each other.
  *
  * @subsection line_cap Line End Cap Style
  * The start and end of a path line can have different visual appearance depending on the following
  * attributes.
  *
  * @par Flat Cap
  * The line is stopped at the end point and the line end is cut square to the direction.
  *
  * @par Square Cap
  * The line is projected beyond the end point by half the line width and the line end is cut square to
  * the direction.
  *
  * @par Round Cap
  * The line is projected beyond the end point by half the line width and the line end is rounded.
  *
  * @subsection line_join Line Join Style
  * Where two lines join, the way the join is shown is determined by the join style as follows.
  *
  * @par Bevel Join
  * The lines are beveled at the intersection.
  *
  * @par Miter Join
  * The lines are extended and mitered to provide a corner.
  *
  * @par Round Join
  * The lines are joined with a rounded corner.
  *
  * @subsection line_width Line Width
  * The line width can be increased and decreased. The width is rendered equally about the line between
  * the two points. This attribute is mostly relevant to unfilled shapes.
  *
  * @section points Points
  * The points can either be snapped to the grid intersections or placed freely depending on the snap option.
  * All points can be moved by hovering over them until the cursor changes to a move cursor, then hold down
  * the left mouse button and drag the point to its new location.
  *
  * @section editing_symbols Editing Symbols
  * Editing a symbol in the library can be done by clicking the symbol in the library view. This will
  * transfer the symbol into the editor allowing it to be changed and saved. In this scenario there is a link
  * between the symbol being edited and the library, so saving does update the correct symbol. If you wish to
  * use this symbol as a basis for other symbols using rotation and flipping, use the File->Save Symbol as New
  * command which will save the symbol to the library as a new one. Further changes to the symbol which are
  * saved will also become new symbols.
  */
 
 
 #include "Editor.h"
 
 #include <QAction>
 #include <QMouseEvent>
 #include <QPainter>
 #include <QString>
 
 #include <KCharSelect>
 #include <KLocalizedString>
 
 #include <math.h>
 
 #include "SymbolEditor.h"
 
 
 const int pointsRequired[] = {1, 1, 3, 2, 2};   /**< The number of points required for commands from Editor::ToolMode */
 
 const QString statusMessages[][3] = {
     {
         I18N_NOOP("Select a new starting position."),
         "",
         ""
     },
     {
         I18N_NOOP("Select the line end point."),
         "",
         ""
     },
     {
         I18N_NOOP("Select the first control point."),
         I18N_NOOP("Select the second control point."),
         I18N_NOOP("Select the end point"),
     },
     {
         I18N_NOOP("Select the first corner."),
         I18N_NOOP("Select the second corner."),
         ""
     },
     {
         I18N_NOOP("Select the first corner of the bounding rectangle."),
         I18N_NOOP("Select the second corner of the bounding rectangle."),
         ""
     },
     {
         I18N_NOOP("Double click a character to insert into the editor."),
         "",
         ""
     }
 };
 
 
 /**
  * Construct the Editor.
  * The editor is a sub class of a QWidget and is added to a layout widget.
  * The boundary edges of the symbol editor are defined in the range 0..1. These are used to intersect
  * the guidelines which are shown at the m_angles relative to existing points
  *
  * @param parent a pointer to the parent widget, this is passed to the base class object
  */
 Editor::Editor(QWidget *parent)
     :   QWidget(parent),
         m_index(0),
         m_charSelect(0)
 {
     readSettings();
 
     setMouseTracking(true);
     setFocusPolicy(Qt::StrongFocus);
 
     m_topEdge = QLineF(0.0, 0.0, 1.0, 0.0);
     m_bottomEdge = QLineF(0.0, 1.0, 1.0, 1.0);
     m_leftEdge = QLineF(0.0, 0.0, 0.0, 1.0);
     m_rightEdge = QLineF(1.0, 0, 1.0, 1.0);
 }
 
 
 /**
  * Destructor for the Editor.
  * No additional destruction is required here.
  */
 Editor::~Editor()
 {
     delete m_charSelect;
 }
 
 
 /**
  * Get the index and Symbol.
  * Update the Symbol with the path being edited.
  *
  * @return the edited Symbol and it's index in a QPair
  */
 QPair<qint16, Symbol> Editor::symbol()
 {
     m_symbol.setPath(m_painterPath);
     return QPair<qint16, Symbol>(m_index, m_symbol);
 }
 
 
 /**
  * Set the symbol and index to be edited.
  * The undo stack will be cleared.
  *
  * @param pair a QPair consisting of the index and the Symbol
  */
 void Editor::setSymbol(const QPair<qint16, Symbol> &pair)
 {
     m_undoStack.clear();
     m_index = pair.first;
     m_symbol = pair.second;
     m_painterPath = m_symbol.path();
     deconstructPainterPath();
     update();
 }
 
 
 /**
  * Move the start of the sub path.
  * The point is in symbol coordinates.
  * Returns the current painterPath for later undo.
  *
  * @param to a const reference to a QPointF representing the new start position
  *
  * @return a QPainterPath representing the original path
  */
 QPainterPath Editor::moveTo(const QPointF &to)
 {
     QPainterPath path = m_painterPath;
     m_painterPath.moveTo(to);
     deconstructPainterPath();
     update();
     return path;
 }
 
 
 /**
  * Add a line to the sub path.
  * The point is in symbol coordinates.
  * Returns the current painterPath for later undo.
  *
  * @param to a const reference to a QPointF representing the end point of the line
  *
  * @return a QPainterPath representing the original path
  */
 QPainterPath Editor::lineTo(const QPointF &to)
 {
     QPainterPath path = m_painterPath;
     m_painterPath.lineTo(to);
     deconstructPainterPath();
     update();
     return path;
 }
 
 
 /**
  * Add a cubic spline to the sub path.
  * The points are in symbol coordinates.
  * Returns the current painterPath for later undo.
  *
  * @param control1 a const reference to a QPointF representing the first control point
  * @param control2 a const reference to a QPointF representing the second control point
  * @param to a const reference to a QPointF representing the end point of the curve
  *
  * @return a QPainterPath representing the original path
  */
 QPainterPath Editor::cubicTo(const QPointF &control1, const QPointF &control2, const QPointF &to)
 {
     QPainterPath path = m_painterPath;
     m_painterPath.cubicTo(control1, control2, to);
     deconstructPainterPath();
     update();
     return path;
 }
 
 
 /**
  * Add a rectangle as a new sub path.
  * The points are in symbol coordinates.
  * Returns the current painterPath for later undo.
  *
  * @param from a const reference to a QPointF representing the first corner
  * @param to a const reference to a QPointF representing the second corner
  *
  * @return a QPainterPath representing the original path
  */
 QPainterPath Editor::addRectangle(const QPointF &from, const QPointF &to)
 {
     QPainterPath path = m_painterPath;
     m_painterPath.addRect(QRectF(from, to));
     deconstructPainterPath();
     update();
     return path;
 }
 
 
 /**
  * Add an ellipse as a new sub path.
  * The points are in symbol coordinates.
  * Returns the current painterPath for later undo.
  *
  * @param from a const reference to a QPointF representing the first corner
  * @param to a const reference to a QPointF representing the second corner
  *
  * @return a QPainterPath representing the original path
  */
 QPainterPath Editor::addEllipse(const QPointF &from, const QPointF &to)
 {
     QPainterPath path = m_painterPath;
     m_painterPath.addEllipse(QRectF(from, to));
     deconstructPainterPath();
     update();
     return path;
 }
 
 
 /**
  * Remove the last added element by restoring the path that existed before the last command.
  *
  * @param path a const reference to a QPainterPath being restored
  */
 void Editor::removeLast(const QPainterPath& path)
 {
     m_painterPath = path;
     deconstructPainterPath();
     update();
 }
 
 
 /**
  * Move a point node to a new position.
  *
  * @param index the index of the point to move
  * @param to a const reference to a QPointF representing the new position
  */
 void Editor::movePoint(int index, const QPointF &to)
 {
     m_points[index] = to;
     constructPainterPath();
     update();
 }
 
 
 /**
  * Rotate all the points around the center of the symbol 90 degrees counter clockwise.
  */
 void Editor::rotatePointsLeft()
 {
     for (int i = 0 ; i < m_points.count() ; ++i) {
         QPointF p = m_points[i];
         m_points[i] = QPointF(p.y(), 1.0 - p.x());
     }
 
     for (int i = 0 ; i < m_activePoints.count() ; ++i) {
         QPointF p = m_activePoints[i];
         m_activePoints[i] = QPointF(p.y(), 1.0 - p.x());
     }
 
     constructPainterPath();
     update();
 }
 
 
 /**
  * Rotate all the points around the center of the symbol 90 degrees clockwise
  */
 void Editor::rotatePointsRight()
 {
     for (int i = 0 ; i < m_points.count() ; ++i) {
         QPointF p = m_points[i];
         m_points[i] = QPointF(1.0 - p.y(), p.x());
     }
 
     for (int i = 0 ; i < m_activePoints.count() ; ++i) {
         QPointF p = m_activePoints[i];
         m_activePoints[i] = QPointF(1.0 - p.y(), p.x());
     }
 
     constructPainterPath();
     update();
 }
 
 
 /**
  * Flip all the points about a vertical axis passing through the symbol center.
  */
 void Editor::flipPointsHorizontal()
 {
     for (int i = 0 ; i < m_points.count() ; ++i) {
         QPointF p = m_points[i];
         p.setX(1.0 - p.x());
         m_points[i] = p;
     }
 
     for (int i = 0 ; i < m_activePoints.count() ; ++i) {
         QPointF p = m_activePoints[i];
         p.setX(1.0 - p.x());
         m_activePoints[i] = p;
     }
 
     constructPainterPath();
     update();
 }
 
 
 /**
  * Flip all the points about a horizontal axis passing through the symbol center.
  */
 void Editor::flipPointsVertical()
 {
     for (int i = 0 ; i < m_points.count() ; ++i) {
         QPointF p = m_points[i];
         p.setY(1.0 - p.y());
         m_points[i] = p;
     }
 
     for (int i = 0 ; i < m_activePoints.count() ; ++i) {
         QPointF p = m_activePoints[i];
         p.setY(1.0 - p.y());
         m_activePoints[i] = p;
     }
 
     constructPainterPath();
     update();
 }
 
 
 /**
  * Set the fill state of the symbols path.
  *
  * @param filled @c true if the path is to be filled, @c false for outline paths
  */
 void Editor::setFilled(bool filled)
 {
     m_symbol.setFilled(filled);
     update();
 }
 
 
 /**
  * Set the fill rule of the symbols path.
  *
  * @param rule a Qt::FillRule value, see the QPainterPath documentation for details
  */
 void Editor::setFillRule(Qt::FillRule rule)
 {
     m_painterPath.setFillRule(rule);
     update();
 }
 
 
 /**
  * Set the pen cap style, see the QPen documentation for details on the styles.
  *
  * @param capStyle a Qt::PenCapStyle value
  */
 void Editor::setCapStyle(Qt::PenCapStyle capStyle)
 {
     m_symbol.setCapStyle(capStyle);
     update();
 }
 
 
 /**
  * Set the pen join style, see the QPen documentation for details on the styles.
  *
  * @param joinStyle a Qt::PenJoinStyle value
  */
 void Editor::setJoinStyle(Qt::PenJoinStyle joinStyle)
 {
     m_symbol.setJoinStyle(joinStyle);
     update();
 }
 
 
 /**
  * Set the line width.
  * The width parameter is rounded to 2 decimal places to avoid errors in the comparisons.
  * Signals are emitted to enable or disable the relevant actions depending on the values.
  *
  * @param width the new line width
  */
 void Editor::setLineWidth(double width)
 {
     width = round(width * 100) / 100;
     m_symbol.setLineWidth(width);
     emit minLineWidth(width == 0.01);
     emit maxLineWidth(width == 1.00);
     update();
 }
 
 
 /**
  * Set the painter path to the requested path updating the points lists and the view.
  *
  * @param path contains the new path
  *
  * @return the old path
  */
 QPainterPath Editor::setPath(const QPainterPath &path)
 {
     QPainterPath originalPath = m_painterPath;
     m_painterPath = path;
     deconstructPainterPath();
     update();
 
     return originalPath;
 }
 
 
 /**
  * Clear the editor to represent a blank symbol.
  * Delete the existing data and update the display.
  */
 void Editor::clear()
 {
     m_undoStack.clear();
     m_points.clear();
     m_activePoints.clear();
     m_elements.clear();
     m_index = 0;
     m_symbol = Symbol();
     m_painterPath = m_symbol.path();
     update();
 }
 
 
 /**
  * Get a pointer to the undo stack.
  *
  * @return a pointer to the QUndoStack
  */
 QUndoStack *Editor::undoStack()
 {
     return &m_undoStack;
 }
 
 
 /**
  * Select the next tool.
  * Remove any points that may have been used in the last tool command but not yet committed.
  * Set the tool mode from the sending actions data.
  * If the character selector tool is selected, display a KCharSelect widget to get a character to be
  * inserted otherwise hide the KCharSelect widget.
  *
  * @param action a pointer to the action triggering the selection
  */
 void Editor::selectTool(QAction *action)
 {
     m_activePoints.clear();
     m_toolMode = static_cast<Editor::ToolMode>(action->data().toInt());
 
     if (m_toolMode == Editor::Character) {
         if (m_charSelect == 0) {
             m_charSelect = new KCharSelect(0, 0);
             connect(m_charSelect, SIGNAL(charSelected(QChar)), this, SLOT(charSelected(QChar)));
         }
 
         m_charSelect->show();
     } else if (m_charSelect) {
         m_charSelect->hide();
     }
 
     updateStatusMessage();
 }
 
 
 /**
  * Called when a character is selected from the KCharSelect widget. Create a QPainterPath object and
  * make it available to the editor for insertion.
  *
  * @param char a QChar containing the character selected.
  */
 void Editor::charSelected(const QChar &character)
 {
     QPainterPath path;
     QFont font = m_charSelect->currentFont();
     path.addText(0.0, 0.0, font, QString(character));
 
     // scale the path to fit the bounding rectangle to fit in a rectangle 0,0-1,1  maintaining
     // aspect ratio.
     QRectF boundingRect = path.boundingRect();
 
     double scale = double(m_gridElements - m_borderSize - m_borderSize) / double(std::max(boundingRect.width(), boundingRect.height()) * m_gridElements);
     QTransform transform = QTransform::fromTranslate(-boundingRect.center().x(), -boundingRect.center().y()) * QTransform::fromScale(scale, scale) * QTransform::fromTranslate(0.5, 0.5);
     path = transform.map(path);
 
     m_undoStack.push(new AddCharacterCommand(this, path));
 }
 
 
 /**
  * Switch the snap mode on or off.
  *
  * @param enabled true if on, false otherwise
  */
 void Editor::enableSnap(bool enabled)
 {
     m_snap = enabled;
 }
 
 
 /**
  * Switch the generation of guides on or off.
  *
  * @param enabled true if on, false otherwise
  */
 void Editor::enableGuides(bool enabled)
 {
     m_guides = enabled;
 }
 
 
 /**
  * Switch the fill mode on or off.
  *
  * @param filled true if on, false otherwise
  */
 void Editor::selectFilled(bool filled)
 {
     m_undoStack.push(new ChangeFilledCommand(this, m_symbol.filled(), filled));
 }
 
 
 /**
  * Select the fill rule to be used when filling is enabled.
  * The specified rule is taken from the sending actions data.
  *
  * @param action a pointer to the action triggering the selection
  */
 void Editor::selectFillRule(QAction *action)
 {
     Qt::FillRule fillRule = static_cast<Qt::FillRule>(action->data().toInt());
     m_undoStack.push(new ChangeFillRuleCommand(this, m_symbol.path().fillRule(), fillRule));
 }
 
 
 /**
  * Select the pen cap style.
  * The specified value is taken from the sending actions data.
  *
  * @param action a pointer to the action that triggered the selection
  */
 void Editor::selectCapStyle(QAction *action)
 {
     Qt::PenCapStyle capStyle = static_cast<Qt::PenCapStyle>(action->data().toInt());
     m_undoStack.push(new ChangeCapStyleCommand(this, m_symbol.capStyle(), capStyle));
 }
 
 
 /**
  * Select the pen join style.
  * The specified value is taken from the sending actions data.
  *
  * @param action a pointer to the action that triggered the selection
  */
 void Editor::selectJoinStyle(QAction *action)
 {
     Qt::PenJoinStyle joinStyle = static_cast<Qt::PenJoinStyle>(action->data().toInt());
     m_undoStack.push(new ChangeJoinStyleCommand(this, m_symbol.joinStyle(), joinStyle));
 }
 
 
 /**
  * Increase the thickness of the path.
  */
 void Editor::increaseLineWidth()
 {
     m_undoStack.push(new IncreaseLineWidthCommand(this, m_symbol.lineWidth(), m_symbol.lineWidth() + 0.01));
 }
 
 
 /**
  * Decrease the thickness of the path.
  */
 void Editor::decreaseLineWidth()
 {
     m_undoStack.push(new DecreaseLineWidthCommand(this, m_symbol.lineWidth(), m_symbol.lineWidth() - 0.01));
 }
 
 
 /**
  * Rotate the symbol left (counter clock wise)
  */
 void Editor::rotateLeft()
 {
     m_undoStack.push(new RotateLeftCommand(this));
 }
 
 
 /**
  * Rotate the symbol right (clock wise)
  */
 void Editor::rotateRight()
 {
     m_undoStack.push(new RotateRightCommand(this));
 }
 
 
 /**
  * Flip the symbol horizontally about the vertical center line.
  */
 void Editor::flipHorizontal()
 {
     m_undoStack.push(new FlipHorizontalCommand(this));
 }
 
 
 /**
  * Flip the symbol vertically about the horizontal center line.
  */
 void Editor::flipVertical()
 {
     m_undoStack.push(new FlipVerticalCommand(this));
 }
 
 
 /**
  * Scale the symbol to fit within the preferred size.
  */
 void Editor::scalePreferred()
 {
     m_undoStack.push(new ScalePreferredCommand(this, m_painterPath, m_gridElements, m_borderSize));
 }
 
 
 /**
  * Read the settings from the configuration file and apply them.
  * The widget is resized to accommodate a gridElements number of cells of width elementSize. An
  * additional 1 is added to allow for a right and bottom edge to be drawn.
  */
 void Editor::readSettings()
 {
     m_gridElements       = Configuration::editor_GridElements();
     m_elementSize        = Configuration::editor_ElementSize();
     m_elementGrouping    = Configuration::editor_ElementGrouping();
     m_pointSize          = static_cast<double>(Configuration::editor_PointSize()) / 500;
     m_snapThreshold      = 1.0 / m_gridElements * Configuration::editor_SnapThreshold();
     m_borderSize         = Configuration::editor_BorderSize();
     m_preferredSizeColor = Configuration::editor_PreferredSizeColor();
     m_guideLineColor     = Configuration::editor_GuideLineColor();
 
     m_angles.clear();
 
     if (Configuration::editor_SimplifiedGuideLines()) {
         m_angles << 0 << 45 << 90 << 135;
     } else {
         m_angles << 0 << 15 << 30 << 45 << 60 << 75 << 90 << 105 << 120 << 135 << 150 << 165;
     }
 
     int minimumSize = m_elementSize * m_gridElements + 1;
     setMinimumSize(minimumSize, minimumSize);
 }
 
 
 /**
  * Process the mouse press event. Effective for the left mouse button pressed.
  * Test if the cursor is over an existing point in which case dragging of the
  * point is enabled. Otherwise a point is added to the active points.
  *
  * @param event a pointer to a QMouseEvent
  */
 void Editor::mousePressEvent(QMouseEvent *event)
 {
     QPoint p = event->pos();
     m_dragging = false;
 
     if (event->buttons() & Qt::LeftButton) {
         m_start = m_tracking = snapPoint(p);
         m_rubberBand = QRectF();
 
         if (node(toSymbol(p))) {
             m_dragging = true;
             m_dragPointIndex = nodeUnderCursor(toSymbol(p));
         } else {
             addPoint(m_start);
         }
     }
 
     update();
 }
 
 
 /**
  * Process the mouse move event. Effective for the left mouse button pressed.
  * Clear any currently defined guides.
  * If dragging a point, update the points position and update the view, otherwise
  * if the toolmode is for a rectangle or an ellipse initialize the rubber band
  * rectangle and update the view.
  * If the left button is not pressed, test if the cursor is over an existing point
  * and if it is change the cursor to a SizeAllCursor to indicate it can be moved,
  * otherwise reset it to an ArrowCursor.
  * Guide lines are constructed for each of the existing points to show if the new
  * position lies in line with or at a specific angle to or on a circular path to
  * that point.
  *
  * @param event a pointer to a QMouseEvent
  */
 void Editor::mouseMoveEvent(QMouseEvent *event)
 {
     QPoint p = event->pos();
 
     if (event->buttons() & Qt::LeftButton) {
         if (m_tracking != snapPoint(p)) {
             m_tracking = snapPoint(p);
 
             if (m_dragging) {
                 if (m_dragPointIndex.first) {
                     m_points[m_dragPointIndex.second] = m_tracking;
                     constructPainterPath();
                 } else {
                     m_activePoints[m_dragPointIndex.second] = m_tracking;
                 }
             } else if (m_toolMode == Rectangle || m_toolMode == Ellipse) {
                 m_rubberBand = QRectF(m_start, m_tracking).normalized();
             }
 
             update();
         }
     } else {
         if (node(toSymbol(p))) {
             setCursor(Qt::SizeAllCursor);
         } else {
             setCursor(Qt::ArrowCursor);
         }
     }
 
     constructGuides(toSymbol(p));
 
     update();
 }
 
 
 /**
  * Process the mouse release event.
  * If dragging a point that is in the m_points list and it hasn't been dragged back to
  * its start position create a MovePointCommand and push it onto the editor undo stack.
  * Pushing commands onto the stack will execute it, although the point is already in its
  * new position, this will have no adverse effects, but will record the move for possible
  * undo/redo later.
  * If not dragging a point, clear the rubber band rectangle and add a point if the new
  * point is not the same as the starting point.
  *
  * @param event a pointer to a QMouseEvent
  */
 void Editor::mouseReleaseEvent(QMouseEvent *event)
 {
     QPointF p = snapPoint(event->pos());
 
     if (m_dragging) {
         if ((p != m_start) && (m_dragPointIndex.first)) {
             m_undoStack.push(new MovePointCommand(this, m_dragPointIndex.second, m_start, p));
         }
 
         m_dragging = false;
     } else if (m_toolMode == Rectangle || m_toolMode == Ellipse) {
         m_rubberBand = QRectF();
 
         if (p != m_start) {
             addPoint(p);
         }
     }
 
     update();
 }
 
 
 /**
  * Add a point for the current tool.
  * Each tool requires a number of points to be defined to fully describe the shape the
  * tool represents. This function adds the points and keeps track of the number of points
  * required.  When the number of points required have been selected, the tool command can
  * be implemented and added to the symbol undo stack.
  * The points are in symbol coordinates in the range 0..1
  *
  * @param point a const reference to a QPointF
  */
 void Editor::addPoint(const QPointF &point)
 {
     m_activePoints.append(point);
 
     if (m_activePoints.count() == pointsRequired[m_toolMode]) {
         switch (m_toolMode) {
         case MoveTo:
             m_undoStack.push(new MoveToCommand(this, m_activePoints.at(0)));
             break;
 
         case LineTo:
             m_undoStack.push(new LineToCommand(this, m_activePoints.at(0)));
             break;
 
         case CubicTo:
             m_undoStack.push(new CubicToCommand(this, m_activePoints.at(0), m_activePoints.at(1), m_activePoints.at(2)));
             break;
 
         case Rectangle:
             m_undoStack.push(new RectangleCommand(this, m_activePoints.at(0), m_activePoints.at(1)));
             break;
 
         case Ellipse:
             m_undoStack.push(new EllipseCommand(this, m_activePoints.at(0), m_activePoints.at(1)));
             break;
 
         case Character: // Insertion of characters does not require points
             break;
         }
 
         m_activePoints.clear();
     }
 
     update();
     updateStatusMessage();
 }
 
 
 /**
  * Update the status message dependent on the command in use and the number of active points
  * in the list.
  */
 void Editor::updateStatusMessage()
 {
     emit message(statusMessages[m_toolMode][m_activePoints.count()]);
 }
 
 
 /**
  * Read settings and set the element size based on the size of the editor window
  *
  * @param event a pointer to the QResizeEvent
  */
 void Editor::resizeEvent(QResizeEvent *event)
 {
     QSize requestedSize = event->size();
 
     int requestedWidth = requestedSize.width();
     int requestedHeight = requestedSize.height();
     int side = std::min(requestedWidth, requestedHeight);
 
     m_elementSize = side / m_gridElements;
     m_size = m_elementSize * m_gridElements;
 
     resize(m_size, m_size);
     move((requestedWidth - m_size) / 2, (requestedHeight - m_size) / 2);
 }
 
 
 /**
  * Paint the contents of the editor.
  * This will fill the background and draw a grid based on the elementSize and elementGroup.
  * For each element of the current path the control points are drawn with suitable lines
  * joining them, for example for a cubic curve, a curve is drawn, but the control points
  * are joined with dashed lines.
  * A complete path is constructed and painted in a light color with transparency to show
  * the current symbol shape.
  *
  * @param event a pointer to a QPaintEvent
  */
 void Editor::paintEvent(QPaintEvent *event)
 {
     // initialise the painter
     QPainter p(this);
     p.setRenderHint(QPainter::Antialiasing, true);
     p.fillRect(event->rect(), Qt::white);
 
     QPen lightGray(Qt::lightGray);
     lightGray.setCosmetic(true);
 
     QPen darkGray(Qt::darkGray);
     darkGray.setCosmetic(true);
 
     // scale the painter to suit the number of elements in the grid
     p.setWindow(0, 0, m_gridElements, m_gridElements);
 
     // draw vertical grid
     for (int x = 0 ; x <= m_gridElements ; ++x) {
         if (x % m_elementGrouping) {
             p.setPen(lightGray);
         } else {
             p.setPen(darkGray);
         }
 
         p.drawLine(x, 0, x, m_gridElements);
     }
 
     // draw horizontal grid
     for (int y = 0 ; y <= m_gridElements ; ++y) {
         if (y % m_elementGrouping) {
             p.setPen(lightGray);
         } else {
             p.setPen(darkGray);
         }
 
         p.drawLine(0, y, m_gridElements, y);
     }
 
     // draw a rectangle representing the preferred symbol size allowing for some white space
     QRectF preferredSizeRect = QRectF(0, 0, m_gridElements, m_gridElements).adjusted(m_borderSize, m_borderSize, -m_borderSize, -m_borderSize);
 
     QColor preferredSizeColor(m_preferredSizeColor);
     preferredSizeColor.setAlpha(128);
 
     QPen preferredSizeColorPen(preferredSizeColor);
     preferredSizeColorPen.setCosmetic(true);
 
     p.setPen(preferredSizeColorPen);
     p.setBrush(Qt::NoBrush);
     p.drawRect(preferredSizeRect);
 
     // define a rectangle for the points
     QRectF dot(0, 0, m_pointSize, m_pointSize);
 
     // create a dashed pen for use with curve references and a wide pen for the shape
     QPen dashedPen(Qt::DashLine);
     dashedPen.setCosmetic(true);
 
     // draw all the points as a circle
     p.setBrush(Qt::SolidPattern);
 
     // scale the painter to draw the points and symbols
     p.setWindow(0, 0, 1, 1);
 
     for (int i = 0 ; i < m_points.count() ; ++i) {
         QPointF s = m_points.at(i);
         dot.moveCenter(s);
         p.drawEllipse(dot);
     }
 
     for (int i = 0 ; i < m_activePoints.count() ; ++i) {
         QPointF s = m_activePoints.at(i);
         dot.moveCenter(s);
         p.drawEllipse(dot);
     }
 
     // iterate through the elements and for each curve element draw the reference lines with a dashed pen
     for (int i = 0, j = 0 ; i < m_elements.count() ; ++i) {
         QPainterPath::ElementType element = m_elements[i];
         QPointF s;
         QPointF e;
         QPointF c1;
         QPointF c2;
 
         switch (element) {
         case QPainterPath::MoveToElement:
             // increment to next pointer
             ++j;
             break;
 
         case QPainterPath::LineToElement:
             // increment to next pointer
             j++;
             break;
 
         case QPainterPath::CurveToElement:
             p.setPen(dashedPen);
             s = m_points.at(j - 1);
             c1 = m_points.at(j++);
             c2 = m_points.at(j++);
             e = m_points.at(j++);
             p.drawLine(s, c1);
             p.drawLine(c1, c2);
             p.drawLine(c2, e);
             break;
 
         case QPainterPath::CurveToDataElement: // this is only used within the constructed QPainterPath
             break;
         }
     }
 
 
     // draw the rubber band rectangle or the active points for the current command
     if (m_rubberBand.isValid()) {
         QPen blackPen(Qt::black);
         blackPen.setCosmetic(true);
         p.setPen(blackPen);
         p.setBrush(Qt::NoBrush);
 
         if (m_toolMode == Rectangle) {
             p.drawRect(m_rubberBand);
         } else {
             p.drawEllipse(m_rubberBand);
         }
     } else if (m_activePoints.count() && m_toolMode != Rectangle && m_toolMode != Ellipse) {
         p.setPen(dashedPen);
         QPointF s;
 
         if (m_points.count()) {
             s = m_points.last();
         }
 
         for (int i = 0 ; i < m_activePoints.count() ; ++i) {
             QPointF e = m_activePoints[i];
             p.drawLine(s, e);
             s = e;
         }
     }
 
     // scale the painter and draw the path
     QColor c(Qt::black);
     c.setAlpha(128);
     QPen pathPen(m_symbol.pen());
     pathPen.setColor(c);
     p.setPen(pathPen);
 
     QBrush pathFill(m_symbol.brush());
     pathFill.setColor(c);
     p.setBrush(pathFill);
 
     p.drawPath(m_painterPath);
 
     // draw the guidelines
     QColor guideLineColor(m_guideLineColor);
     guideLineColor.setAlpha(128);
 
     QPen guideLinePen(guideLineColor);
     guideLinePen.setCosmetic(true);
 
     p.setPen(guideLinePen);
     p.setBrush(Qt::NoBrush);
     QRectF snapRect(0, 0, 0.03, 0.03);
 
     foreach (const QPointF & snapPoint, m_snapPoints) {
         snapRect.moveCenter(snapPoint);
         p.drawRect(snapRect);
     }
 
     foreach (const QLineF & guideLine, m_guideLines) {
         p.drawLine(guideLine);
     }
 
     foreach (qreal guideCircle, m_guideCircles) {
         p.drawEllipse(QPointF(0.5, 0.5), guideCircle, guideCircle);
     }
 }
 
 
 /**
  * Process key presses to check for Escape to clear the current points being entered.
  *
  * @param event a pointer to a QKeyEvent
  */
 void Editor::keyPressEvent(QKeyEvent *event)
 {
     switch (event->key()) {
     case Qt::Key_Escape:
         m_activePoints.clear();
         update();
         break;
 
     default:
         QWidget::keyPressEvent(event);
         break;
     }
 }
 
 
 /**
  * Convert a point to a symbol point.
  *
  * The point will have come from the mouse events pos() value and will be converted to
  * a value representing a point in the symbol, not necessarily at a snap position.
  *
  * @param point a const reference to a QPoint
  *
  * @return a QPointF representing the point in symbol coordinates between 0..1
  */
 QPointF Editor::toSymbol(const QPoint &point) const
 {
     double sx = static_cast<double>(point.x()) / m_size;
     double sy = static_cast<double>(point.y()) / m_size;
     return QPointF(sx, sy);
 }
 
 
 /**
  * Convert a point to a snap point.
  *
  * The point comes from the mouse events pos() value and will be converted to a value
  * in symbol coordinates. If snapping is enabled, the point will be snapped to a guide
  * or to a grid intersection. If snapping is disabled, the point is returned converted
  * to the symbol coordinates.
  *
  * @param point a const reference to a QPoint
  *
  * @return a QPointF representing the symbol coordinates either snapped or not.
  */
 QPointF Editor::snapPoint(const QPoint &point) const
 {
     QPair<bool, QPointF> snap = snapToGuide(toSymbol(point));
 
     if (!snap.first) {
         snap = snapToGrid(point);
     }
 
     return snap.second;
 }
 
 
 /**
  * Convert a point to a symbol snap point.
  * The point will have come from the mouse events pos() value and will be converted to
  * a value that represents an intersection of the grid lines. This will happen only if
  * snapping is enabled.
  *
  * @param point a const reference to a QPoint
  *
  * @return a QPair<bool, QPointF> the bool element determines if a snap point was found represented by the QPointF element
  */
 QPair<bool, QPointF> Editor::snapToGrid(const QPoint &point) const
 {
     QPair<bool, QPointF> snap(false, toSymbol(point));
 
     if (m_snap) {
         double sx = round(static_cast<double>(point.x()) * m_gridElements / (m_size)) / m_gridElements;
         double sy = round(static_cast<double>(point.y()) * m_gridElements / (m_size)) / m_gridElements;
         snap.first = true;
         snap.second = QPointF(sx, sy);
     }
 
     return snap;
 }
 
 
 /**
  * Convert a point to a guide snap point.
  * The point will have come from the mouse events pos() value and will be converted to
  * a value that is within the threshold of a calculated guide intersection. This will
  * happen only if the snapping is enabled.
  *
  * @param point a const reference to a QPointF
  *
  * @return a QPair<bool, QPointF> the bool element determines if a snap point was found represented by the QPointF element
  */
 QPair<bool, QPointF> Editor::snapToGuide(const QPointF &point) const
 {
     QPair<bool, QPointF> snap(false, point);
 
     if (m_snap) {
         foreach (const QPointF & p, m_snapPoints) {
             if ((point - p).manhattanLength() < m_snapThreshold) {
                 snap.first = true;
                 snap.second = p;
                 break;
             }
         }
     }
 
     return snap;
 }
 
 
 /**
  * Test if a control point is at the point specified.
  * This will test both the committed m_points and the uncommitted m_activePoints
  *
  * @param point a const reference to a QPointF representing the symbol coordinate
  *
  * @return true if a node exists here, false otherwise
  */
 bool Editor::node(const QPointF &point) const
 {
     bool found = false;
 
     for (int i = 0 ; i < m_points.count() ; ++i) {
         QPointF distance = point - m_points[i];
 
         if (distance.manhattanLength() < m_snapThreshold) {
             found = true;
         }
     }
 
     for (int i = 0 ; i < m_activePoints.count() ; ++i) {
         QPointF distance = point - m_activePoints[i];
 
         if (distance.manhattanLength() < m_snapThreshold) {
             found = true;
         }
     }
 
     return found;
 }
 
 
 /**
  * Find the index of the node that is at the point specified.
  * This will test both the committed m_points and the uncommitted m_activePoints
  *
  * @param point a const reference to a QPointF representing the point to find
  *
  * @return a QPair<bool, int> representing the list and the index of the node, true if committed, false otherwise
  * -1 is returned as the index if the node was not found
  */
 QPair<bool, int> Editor::nodeUnderCursor(const QPointF &point) const
 {
     for (int i = 0 ; i < m_points.count() ; ++i) {
         QPointF distance = point - m_points[i];
 
         if (distance.manhattanLength() < m_snapThreshold) {
             return QPair<bool, int>(true, i);
         }
     }
 
     for (int i = 0 ; i < m_activePoints.count() ; ++i) {
         QPointF distance = point - m_activePoints[i];
 
         if (distance.manhattanLength() < m_snapThreshold) {
             return QPair<bool, int>(false, i);
         }
     }
 
     return QPair<bool, int>(false, -1);
 }
 
 
 /**
  * Convert a QPainterPath to commands and points.
  * Clear the current lists of points.
  * Iterate all the elements of the QPainterPath adding commands and points as necessary.
  */
 void Editor::deconstructPainterPath()
 {
     m_points.clear();
     m_activePoints.clear();
     m_elements.clear();
 
     for (int i = 0 ; i < m_painterPath.elementCount() ; ++i) {
         QPainterPath::Element e = m_painterPath.elementAt(i);
 
         switch (e.type) {
         case QPainterPath::MoveToElement:
             m_elements.append(e.type);
             m_points.append(QPointF(e));
             break;
 
         case QPainterPath::LineToElement:
             m_elements.append(e.type);
             m_points.append(QPointF(e));
             break;
 
         case QPainterPath::CurveToElement:
             m_elements.append(e.type);
             m_points.append(QPointF(e));
             break;
 
         case QPainterPath::CurveToDataElement:
             m_points.append(QPointF(e));
             break;
         }
     }
 }
 
 
 /**
  * Construct a QPainterPath from the commands and points.
  * Initialize an empty QPainterPath.
  * Iterate all elements stored in m_elements and add them to the path.
  */
 void Editor::constructPainterPath()
 {
     QPainterPath path;;
 
     for (int i = 0, j = 0 ; i < m_elements.count() ; ++i) {
         QPainterPath::ElementType e = m_elements[i];
 
         switch (e) {
         case QPainterPath::MoveToElement:
             path.moveTo(m_points[j++]);
             break;
 
         case QPainterPath::LineToElement:
             path.lineTo(m_points[j++]);
             break;
 
         case QPainterPath::CurveToElement:
             path.cubicTo(m_points[j], m_points[j + 1], m_points[j + 2]);
             j += 3;
             break;
 
         case QPainterPath::CurveToDataElement: // this only appears within the QPainterPath
             break;
         }
     }
 
     path.setFillRule(m_painterPath.fillRule());
     m_painterPath = path;
 }
 
 
 /**
  * Construct guides for the cursor position point being tested relative to the other points.
  * Iterate through points in m_points and m_active points projecting them out in the directions
  * being tested to determine if they intersect any existing guide lines at a point near to the
  * cursor position. If found they are added to the list of relevant lines and the snap point of the
  * intersection is added to snap points.
  * A list of circles is created where the radius to the point is similar to the test point. Intersection
  * points are calculated for the projected lines and if these are close to the cursor position they
  * are added to the snap points along with the circles and lines.
  * If the generation of guide lines is turned off, the existing guides are cleared on no more are created.
  *
  * @param to a const reference to a QPointF representing the cursor position
  */
 void Editor::constructGuides(const QPointF &to)
 {
     m_guideLines.clear();
     m_guideCircles.clear();
     m_snapPoints.clear();
 
     if (!m_guides) {
         return;
     }
 
     QList<QPointF> points;
     points << m_points << m_activePoints;   // construct list of all points on screen
 
     QList<double> guideCircles;             // local list of circles, used for filtering
     QList<QLineF> guideLines;               // local list of lines, used for filtering
 
     double radiusTo = sqrt(pow(0.5 - to.x(), 2) + pow(0.5 - to.y(), 2));
 
     foreach (const QPointF &from, points) {
         if ((from - to).manhattanLength() < m_snapThreshold * 2) {
             continue;    // cursor close to existing point so ignore it
         }
 
         double radiusFrom = sqrt(pow(0.5 - from.x(), 2) + pow(0.5 - from.y(), 2));
 
         if (fabs(radiusTo - radiusFrom) < m_snapThreshold) {
             guideCircles.append(radiusFrom);
         }
 
         // construct line guides
         QLineF guideLine(from, from + QPointF(1.0, 0.0));
 
         foreach (double angle, m_angles) {
             guideLine.setAngle(angle);
             QLineF projectedGuideLine = projected(guideLine);
 
             QPointF intersection;
 
             foreach (const QLineF &line, guideLines) {
                 if (projectedGuideLine.intersect(line, &intersection)) {
                     if (((to - intersection).manhattanLength() < m_snapThreshold)) {
                         addGuideLine(line);
                         addGuideLine(projectedGuideLine);
                         addSnapPoint(intersection);
                     }
                 }
             }
 
             guideLines.append(projectedGuideLine);
         }
 
         // construct circle guides
         foreach (double radius, guideCircles) {
             foreach (const QLineF &line, guideLines) {
                 double ax = line.x1();
                 double ay = line.y1();
                 double bx = line.x2();
                 double by = line.y2();
                 double cx = 0.5;
                 double cy = 0.5;
 
                 double lab = sqrt(pow(bx - ax, 2.0) + pow(by - ay, 2.0));
                 double dx = (bx - ax) / lab;
                 double dy = (by - ay) / lab;
 
                 double t = dx * (cx - ax) + dy * (cy - ay);
 
                 double ex = t * dx + ax;
                 double ey = t * dy + ay;
 
                 double lec = sqrt(pow(ex - cx, 2.0) + pow(ey - cy, 2.0));
 
                 if (lec < radius) {
                     double dt = sqrt(pow(radius, 2.0) - pow(lec, 2.0));
 
                     // first intersection
                     double fx = (t - dt) * dx + ax;
                     double fy = (t - dt) * dy + ay;
 
                     if ((QPointF(fx, fy) - to).manhattanLength() < m_snapThreshold) {
                         addGuideCircle(radius);
                         addGuideLine(line);
                         addSnapPoint(QPointF(fx, fy));
                     }
 
                     // second intersection
                     double gx = (t + dt) * dx + ax;
                     double gy = (t + dt) * dy + ay;
 
                     if ((QPointF(gx, gy) - to).manhattanLength() < m_snapThreshold) {
                         addGuideCircle(radius);
                         addGuideLine(line);
                         addSnapPoint(QPointF(gx, gy));
                     }
                 } else if (lec == radius) {
                     // intersection is ex, ey
                     if ((QPointF(ex, ey) - to).manhattanLength() < m_snapThreshold) {
                         addGuideCircle(radius);
                         addGuideLine(line);
                         addSnapPoint(QPointF(ex, ey));
                     }
                 }
             }
         }
     }
 }
 
 
 /**
  * Add a guide line to m_guideLines after checking it doesn't exist yet
  *
  * @param line a const reference to a QLineF representing the reference line
  */
 void Editor::addGuideLine(const QLineF &line)
 {
     if (!m_guideLines.contains(line)) {
         m_guideLines.append(line);
     }
 }
 
 
 /**
  * Add a guide circle to m_guideCircles after checking it doesn't exist yet
  *
  * @param radius a double representing the circle at center (0.5, 0.5)
  */
 void Editor::addGuideCircle(double radius)
 {
     if (!m_guideCircles.contains(radius)) {
         m_guideCircles.append(radius);
     }
 }
 
 
 /**
  * Add a snap point to m_snapPoints after checking it doesn't exist yet
  *
  * @param point a const reference to a QPointF representing the snap position
  */
 void Editor::addSnapPoint(const QPointF &point)
 {
     if (!m_snapPoints.contains(point)) {
         m_snapPoints.append(point);
     }
 }
 
 
 /**
  * Project the line to the edges of the grid.
  * Calculate the points where the projected line would intersect the edges.
  * Check which edges get intersected within the coordinate 0..1 which will determine
  * which points are required to construct the projected line.
  *
  * @param line a const reference to a QLineF
  *
  * @return a QLineF representing the projected line
  */
 QLineF Editor::projected(const QLineF &line) const
 {
     QPointF intersectTop;
     QPointF intersectBottom;
     QPointF intersectLeft;
     QPointF intersectRight;
 
     QLineF::IntersectType t = line.intersect(m_topEdge, &intersectTop);;
     line.intersect(m_bottomEdge, &intersectBottom);
     line.intersect(m_leftEdge, &intersectLeft);
     line.intersect(m_rightEdge, &intersectRight);
 
     if (t == QLineF::NoIntersection) {      // horizontal line
         return QLineF(intersectLeft, intersectRight);
     }
 
     return QLineF(intersectTop, intersectBottom);
 }