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# diagramscene.cpp Example File
graphicsview/diagramscene/diagramscene.cpp

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     #include <QtGui>

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

     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());
             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;
     }