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Erase QGraphicsRectItem

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  • K Offline
    K Offline
    Kaznachei
    wrote on last edited by
    #1

    I ve got custom GraphicsRectItem which inherits QGraphicsRectItem. I paint on GraphicsRectItem using paint() - function, but sometimes i need erase it. How can i do it not using paint() - function?

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    • mrjjM Offline
      mrjjM Offline
      mrjj
      Lifetime Qt Champion
      wrote on last edited by
      #2

      Hi
      What do yo mean by erase it ? Not delete the item , but remove any "paint"?
      If you mean whatever you draw with QPainter, then you need to alter
      the paint function to draw empty rect to clear it.

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      • K Offline
        K Offline
        Kaznachei
        wrote on last edited by
        #3

        Hello. I had to create bool-value and i called it "IN". I override hoverLeaveEvent and hoverEnterEvent like this

        void hoverLeaveEvent(QGraphicsSceneHoverEvent *event)
        {
        in = false;
        }

        void hoverEnterEvent(QGraphicsSceneHoverEvent *event)
        {
        in = true;
        }

        void paint(QPainter *painter, QStyleoOptionGraphicsItem option, QWidget widget = nullptr)
        {
        if (in)
        {
        // draw something
        }
        }

        it works but , as for me, it is bad way. Or not? Sometimes i ve got trouble. I ve got QGraphicsScene and custom GraphicsRectItem and when my button pressed hoverLeaveEvent and hoverEnterEvent doesnt work because of scene that grabbed mouse.

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        • mrjjM Offline
          mrjjM Offline
          mrjj
          Lifetime Qt Champion
          wrote on last edited by
          #4

          Hi
          Well its not a bad way as such but if enter/leave is the only way its controlled
          then yes, it has issues with buttons as they grab the mouse.

          Im not sure what you use it for but if it should only be shown when you enter and
          "removed" when you leave, then i think you need to grab the mouse to be sure it happens.

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          • K Offline
            K Offline
            Kaznachei
            wrote on last edited by
            #5

            I m not sure that can you understand you. Can you describe your idea by code ?

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            • mrjjM Offline
              mrjjM Offline
              mrjj
              Lifetime Qt Champion
              wrote on last edited by
              #6

              Hi
              I mean try to call
              https://doc.qt.io/qt-5/qwidget.html#grabMouse in hoverEnterEvent
              and https://doc.qt.io/qt-5/qwidget.html#releaseMouse in hoverLeaveEvent
              to try to make sure you get the leave event to have it not draw anything.

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              • K Offline
                K Offline
                Kaznachei
                wrote on last edited by
                #7

                I ve got custom GraphicsItem. Well

                virtual void hoverLeaveEvent(QGraphicsSceneHoverEvent *event)
                {
                ungrabMouse();
                Q_UNUSED(event);
                in = false;
                for(int i = 0; i < 4; ++i)
                update(targets[i]);
                }

                virtual void hoverEnterEvent(QGraphicsSceneHoverEvent *event)
                {
                    grabMouse();
                    Q_UNUSED(event);
                    in = true;
                    for(int i = 0; i < 4; ++i)
                        update(targets[i]);
                }
                
                
                void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = nullptr)
                {
                    if (in)
                    {
                        if (Action::activeAction == Action::Text)
                        {
                            painter->setRenderHint(QPainter::SmoothPixmapTransform);
                
                            for(int  i = 0; i < 4; ++i)
                                painter->drawPixmap(targets[i],arrows.at(i),QRect(0,0,targets[i].width(),targets[i].height()));
                
                            QRectF rectText(indent,indent, proxy->rect().width()*proxy->scale(), proxy->rect().height()*proxy->scale());
                            painter->drawRoundRect(rectText);
                        }
                
                        else if (Action::activeAction == Action::Line)
                        {
                            painter->setPen(Qt::red);
                            painter->drawRect(rect());
                        }
                    }
                
                }
                

                when i my mouse inside of GraphicsItem then it grabs mouse but when i leave GraphicsItem it doesnt ungrabMouse. But if mouse leave window of my application then it ungrabs mouse.

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                • mrjjM Offline
                  mrjjM Offline
                  mrjj
                  Lifetime Qt Champion
                  wrote on last edited by
                  #8

                  Hi
                  So hoverLeaveEvent do not fire for your GraphicsItem, even you grab the mouse?

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                  • K Offline
                    K Offline
                    Kaznachei
                    wrote on last edited by Kaznachei
                    #9

                    When i clicked not on GraphicsItem and moved into GraphicsItem. hoverLeaveEvent and hoverEnterEvent doesnt work, but if i moving into GraphicsItem without pressing hoverLeaveEvent and hoverEnterEvent are working. This my code

                    virtual void hoverLeaveEvent(QGraphicsSceneHoverEvent *event)
                    {
                        Q_UNUSED(event);
                        in = false;
                        for(int i = 0; i < 4; ++i)
                            update(targets[i]);
                    }
                    
                    virtual void hoverEnterEvent(QGraphicsSceneHoverEvent *event)
                    {
                        Q_UNUSED(event);
                        in = true;
                        for(int i = 0; i < 4; ++i)
                            update(targets[i]);
                    }
                    
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                    • mrjjM Offline
                      mrjjM Offline
                      mrjj
                      Lifetime Qt Champion
                      wrote on last edited by
                      #10

                      Hi
                      What do you click on first when it doesn't work ?

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                      • K Offline
                        K Offline
                        Kaznachei
                        wrote on last edited by Kaznachei
                        #11

                        0_1556642662551_Снимок.PNG

                        I clicked on where the point( for example ) and move into Text ( It is GraphicsItem with QTextEdit ) then hoverEnterEvent doesnt work

                        mrjjM 1 Reply Last reply
                        0
                        • K Kaznachei

                          0_1556642662551_Снимок.PNG

                          I clicked on where the point( for example ) and move into Text ( It is GraphicsItem with QTextEdit ) then hoverEnterEvent doesnt work

                          mrjjM Offline
                          mrjjM Offline
                          mrjj
                          Lifetime Qt Champion
                          wrote on last edited by
                          #12

                          @Kaznachei
                          Hmm, i dont know why.
                          The TextEdit has the focus but that would not normally block enterEvent for other
                          Widgets but maybe its a side effect of mixing it with GraphicsItems.

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