Diagram Scene Example

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#include "diagramscene.h"
#include "arrow.h"

#include <QTextCursor>
#include <QGraphicsSceneMouseEvent>

DiagramScene::DiagramScene(QMenu *itemMenu, QObject *parent)
    : QGraphicsScene(parent)
{
    myItemMenu = itemMenu;
    myMode = MoveItem;
    myItemType = DiagramItem::Step;
    line = 0;
    textItem = 0;
    myItemColor = Qt::white;
    myTextColor = Qt::black;
    myLineColor = Qt::black;
}

void DiagramScene::setLineColor(const QColor &color)
{
    myLineColor = color;
    if (isItemChange(Arrow::Type)) {
        Arrow *item = qgraphicsitem_cast<Arrow *>(selectedItems().first());
        item->setColor(myLineColor);
        update();
    }
}

void DiagramScene::setTextColor(const QColor &color)
{
    myTextColor = color;
    if (isItemChange(DiagramTextItem::Type)) {
        DiagramTextItem *item = qgraphicsitem_cast<DiagramTextItem *>(selectedItems().first());
        item->setDefaultTextColor(myTextColor);
    }
}

void DiagramScene::setItemColor(const QColor &color)
{
    myItemColor = color;
    if (isItemChange(DiagramItem::Type)) {
        DiagramItem *item = qgraphicsitem_cast<DiagramItem *>(selectedItems().first());
        item->setBrush(myItemColor);
    }
}

void DiagramScene::setFont(const QFont &font)
{
    myFont = font;

    if (isItemChange(DiagramTextItem::Type)) {
        QGraphicsTextItem *item = qgraphicsitem_cast<DiagramTextItem *>(selectedItems().first());
        //At this point the selection can change so the first selected item might not be a DiagramTextItem
        if (item)
            item->setFont(myFont);
    }
}

void DiagramScene::setMode(Mode mode)
{
    myMode = mode;
}

void DiagramScene::setItemType(DiagramItem::DiagramType type)
{
    myItemType = type;
}

void DiagramScene::editorLostFocus(DiagramTextItem *item)
{
    QTextCursor cursor = item->textCursor();
    cursor.clearSelection();
    item->setTextCursor(cursor);

    if (item->toPlainText().isEmpty()) {
        removeItem(item);
        item->deleteLater();
    }
}

void DiagramScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    if (mouseEvent->button() != Qt::LeftButton)
        return;

    DiagramItem *item;
    switch (myMode) {
        case InsertItem:
            item = new DiagramItem(myItemType, myItemMenu);
            item->setBrush(myItemColor);
            addItem(item);
            item->setPos(mouseEvent->scenePos());
            emit itemInserted(item);
            break;
        case InsertLine:
            line = new QGraphicsLineItem(QLineF(mouseEvent->scenePos(),
                                        mouseEvent->scenePos()));
            line->setPen(QPen(myLineColor, 2));
            addItem(line);
            break;
        case InsertText:
            textItem = new DiagramTextItem();
            textItem->setFont(myFont);
            textItem->setTextInteractionFlags(Qt::TextEditorInteraction);
            textItem->setZValue(1000.0);
            connect(textItem, SIGNAL(lostFocus(DiagramTextItem*)),
                    this, SLOT(editorLostFocus(DiagramTextItem*)));
            connect(textItem, SIGNAL(selectedChange(QGraphicsItem*)),
                    this, SIGNAL(itemSelected(QGraphicsItem*)));
            addItem(textItem);
            textItem->setDefaultTextColor(myTextColor);
            textItem->setPos(mouseEvent->scenePos());
            emit textInserted(textItem);
    default:
        ;
    }
    QGraphicsScene::mousePressEvent(mouseEvent);
}

void DiagramScene::mouseMoveEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    if (myMode == InsertLine && line != 0) {
        QLineF newLine(line->line().p1(), mouseEvent->scenePos());
        line->setLine(newLine);
    } else if (myMode == MoveItem) {
        QGraphicsScene::mouseMoveEvent(mouseEvent);
    }
}

void DiagramScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    if (line != 0 && myMode == InsertLine) {
        QList<QGraphicsItem *> startItems = items(line->line().p1());
        if (startItems.count() && startItems.first() == line)
            startItems.removeFirst();
        QList<QGraphicsItem *> endItems = items(line->line().p2());
        if (endItems.count() && endItems.first() == line)
            endItems.removeFirst();

        removeItem(line);
        delete line;

        if (startItems.count() > 0 && endItems.count() > 0 &&
            startItems.first()->type() == DiagramItem::Type &&
            endItems.first()->type() == DiagramItem::Type &&
            startItems.first() != endItems.first()) {
            DiagramItem *startItem = qgraphicsitem_cast<DiagramItem *>(startItems.first());
            DiagramItem *endItem = qgraphicsitem_cast<DiagramItem *>(endItems.first());
            Arrow *arrow = new Arrow(startItem, endItem);
            arrow->setColor(myLineColor);
            startItem->addArrow(arrow);
            endItem->addArrow(arrow);
            arrow->setZValue(-1000.0);
            addItem(arrow);
            arrow->updatePosition();
        }
    }
    line = 0;
    QGraphicsScene::mouseReleaseEvent(mouseEvent);
}

bool DiagramScene::isItemChange(int type)
{
    foreach (QGraphicsItem *item, selectedItems()) {
        if (item->type() == type)
            return true;
    }
    return false;
}