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How to invoke QBrush.setTexture() with QPixmap on QGraphicsRectItem?

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  • K Offline
    K Offline
    Kevin Zhong
    wrote on last edited by
    #10

    Thanks for all of you kindly support.

    It really works.

    One more questions, How can I update the png after the item status changed?
    I mean if the item changed status from shutdown to startup, the png should changed into ":/images/h_startup.png".

    mrjjM 1 Reply Last reply
    0
    • K Kevin Zhong

      Thanks for all of you kindly support.

      It really works.

      One more questions, How can I update the png after the item status changed?
      I mean if the item changed status from shutdown to startup, the png should changed into ":/images/h_startup.png".

      mrjjM Offline
      mrjjM Offline
      mrjj
      Lifetime Qt Champion
      wrote on last edited by mrjj
      #11

      @Kevin-Zhong

      • One more questions, How can I update the png after the item status changed?

      You make the class know which image to draw via variable

      
      **NEW** 
      const int StartImage=1; ( or use enum)
      const int StopImage=2;
      
      class MyItem :public QGraphicsRectItem  ( OR QGraphicsItem ) {
      int Status=StartImage; // some flag to tell if start or stop  **NEW**
      public:
      void SetStatus(int newStatus) {  Status=newStatus;  update(); /* this makes it redraw ( i hope) */ } **NEW**
      ...
          // overriding paint()
      void paint(QPainter * painter,   const QStyleOptionGraphicsItem * option,   QWidget * widget) 
      {
        // draw pixmap
        QPixmap pixStart(":/images/h_startdown.png"); // could be loaded in constructor so we dont do each draw
        QPixmap pixStop(":/images/h_shutdown.png");
      // draw one or the other   
      if (Status == StartImage )
        painter->drawPixmap(pixStart);
        else
        painter->drawPixmap(pixStop);
      
        // draw normally
        QGraphicsRectItem::paint(painter, option, widget); ( or QGraphicsItem::paint)
       }
      };
      
      

      Then from outside, you can do

      myitem->SetStatus(StartImage);
      or
      myitem->SetStatus(StopImage);

      K 1 Reply Last reply
      0
      • K Offline
        K Offline
        Kevin Zhong
        wrote on last edited by
        #12

        Thank you very MUCH!!!
        It's very helpful.

        You are so nice!

        BRs
        Kevin

        1 Reply Last reply
        1
        • mrjjM mrjj

          @Kevin-Zhong

          • One more questions, How can I update the png after the item status changed?

          You make the class know which image to draw via variable

          
          **NEW** 
          const int StartImage=1; ( or use enum)
          const int StopImage=2;
          
          class MyItem :public QGraphicsRectItem  ( OR QGraphicsItem ) {
          int Status=StartImage; // some flag to tell if start or stop  **NEW**
          public:
          void SetStatus(int newStatus) {  Status=newStatus;  update(); /* this makes it redraw ( i hope) */ } **NEW**
          ...
              // overriding paint()
          void paint(QPainter * painter,   const QStyleOptionGraphicsItem * option,   QWidget * widget) 
          {
            // draw pixmap
            QPixmap pixStart(":/images/h_startdown.png"); // could be loaded in constructor so we dont do each draw
            QPixmap pixStop(":/images/h_shutdown.png");
          // draw one or the other   
          if (Status == StartImage )
            painter->drawPixmap(pixStart);
            else
            painter->drawPixmap(pixStop);
          
            // draw normally
            QGraphicsRectItem::paint(painter, option, widget); ( or QGraphicsItem::paint)
           }
          };
          
          

          Then from outside, you can do

          myitem->SetStatus(StartImage);
          or
          myitem->SetStatus(StopImage);

          K Offline
          K Offline
          Kevin Zhong
          wrote on last edited by
          #13

          @mrjj

          I try to update the png for the item when some status changed.

          But every time I need to trigger the ui to repaint, it seems that it never repaint the ui unless there are some change in the UI, such as move cursor or focus on the UI.

          Is there any way to update the UI automatically?

          BRs
          Kevin

          mrjjM 1 Reply Last reply
          0
          • A Offline
            A Offline
            Asperamanca
            wrote on last edited by
            #14

            Calling update() on the item should do the trick.

            1 Reply Last reply
            1
            • K Kevin Zhong

              @mrjj

              I try to update the png for the item when some status changed.

              But every time I need to trigger the ui to repaint, it seems that it never repaint the ui unless there are some change in the UI, such as move cursor or focus on the UI.

              Is there any way to update the UI automatically?

              BRs
              Kevin

              mrjjM Offline
              mrjjM Offline
              mrjj
              Lifetime Qt Champion
              wrote on last edited by
              #15

              @Kevin-Zhong
              Hi
              Did you call the
              void SetStatus(int newStatus) {
              Status=newStatus;
              update(); /* this makes it redraw ( i hope) */ << this should make it draw the other bitmap?
              }

              K 1 Reply Last reply
              0
              • mrjjM mrjj

                @Kevin-Zhong
                Hi
                Did you call the
                void SetStatus(int newStatus) {
                Status=newStatus;
                update(); /* this makes it redraw ( i hope) */ << this should make it draw the other bitmap?
                }

                K Offline
                K Offline
                Kevin Zhong
                wrote on last edited by
                #16

                @mrjj

                The behavior is the same as I mentioned before whatever I use update or repaint. Actually, I prefer to use repaint because I need to refresh the item secondly.

                BRs
                Kevin

                mrjjM 1 Reply Last reply
                0
                • K Kevin Zhong

                  @mrjj

                  The behavior is the same as I mentioned before whatever I use update or repaint. Actually, I prefer to use repaint because I need to refresh the item secondly.

                  BRs
                  Kevin

                  mrjjM Offline
                  mrjjM Offline
                  mrjj
                  Lifetime Qt Champion
                  wrote on last edited by
                  #17

                  @Kevin-Zhong
                  Ok, im not sure why.
                  maybe update() dont trigger painter.
                  Would need to debug to know.
                  Normally it just works.

                  K 1 Reply Last reply
                  0
                  • mrjjM mrjj

                    @Kevin-Zhong
                    Ok, im not sure why.
                    maybe update() dont trigger painter.
                    Would need to debug to know.
                    Normally it just works.

                    K Offline
                    K Offline
                    Kevin Zhong
                    wrote on last edited by
                    #18

                    @mrjj

                    I try to overload the paintEvent in my own code.
                    But after I call item.repaint() the paintEvent was not invoked.

                    But this is the interface description for Qt 5.6.

                    [slot] void QWidget::repaint()
                    Repaints the widget directly by calling paintEvent() immediately, unless updates are disabled or the widget is hidden.
                    We suggest only using repaint() if you need an immediate repaint, for example during animation. In almost all circumstances update() is better, as it permits Qt to optimize for speed and minimize flicker.
                    Warning: If you call repaint() in a function which may itself be called from paintEvent(), you may get infinite recursion. The update() function never causes recursion.
                    See also update(), paintEvent(), and setUpdatesEnabled().

                    1 Reply Last reply
                    0
                    • mrjjM Offline
                      mrjjM Offline
                      mrjj
                      Lifetime Qt Champion
                      wrote on last edited by mrjj
                      #19

                      Hi
                      are we still talking about the QGraphicsItem ?
                      As far as I know they do not have paintEvent only
                      void paint(QPainter * painter,xx)

                      So item.update() should trigger it ?

                      Maybe show full code of what you are doing ?

                      K 1 Reply Last reply
                      0
                      • mrjjM mrjj

                        Hi
                        are we still talking about the QGraphicsItem ?
                        As far as I know they do not have paintEvent only
                        void paint(QPainter * painter,xx)

                        So item.update() should trigger it ?

                        Maybe show full code of what you are doing ?

                        K Offline
                        K Offline
                        Kevin Zhong
                        wrote on last edited by
                        #20

                        @mrjj

                        My code is a little bit complex.
                        Let's recap my original purpose.
                        At the beginning, I just want to use a png as background at the GraphicsRectItem.
                        I tried to use code below:

                        QImage mage = (QImage(":/images/h_" + filename + ".png"));                        
                        brush.setTextureImage(image.scaled(70,30,Qt::KeepAspectRatio, Qt::FastTransformation));
                        

                        The result is not what I want.
                        So, I try to follow your guys' suggestion.

                        map = QPixmap(":/images/h_" + statusStr + ".png");
                        painter->drawPixmap((int)x, (int)y, 40, 50, map);
                        

                        It's really works, the png can be shown correctly, not collage.
                        But the png cannot be redraw immediately only I move the cursor or focus the window.
                        So, is it possible to show the png in the GraphicsRectItem? Because I need to show lots of triangle, rectangle and cricle on the QGraphsicsView with hoverEvent and click Event.

                        BRs
                        Kevin

                        1 Reply Last reply
                        0
                        • mrjjM Offline
                          mrjjM Offline
                          mrjj
                          Lifetime Qt Champion
                          wrote on last edited by
                          #21
                          • But the png cannot be redraw immediately only I move the cursor or focus the window.

                          That is the part i dont understand.
                          It should trigger paint()!?!

                          • So, is it possible to show the png in the GraphicsRectItem?
                            Yes , same as with QGraphicsItem , but i be surprised if that alters anything.

                          When calling update() it should draw the png. Else there is a bug in the code. or something im not aware of.
                          You should looking to this. Using break points. etc.

                          item->update() should trigger paint() , else i have no idea what is going on.

                          1 Reply Last reply
                          0
                          • A Offline
                            A Offline
                            Asperamanca
                            wrote on last edited by
                            #22

                            Do not confuse paintEvent with paint.
                            paintEvent is for Widgets
                            paint is for GraphicsItems

                            1 Reply Last reply
                            0
                            • K Offline
                              K Offline
                              Kevin Zhong
                              wrote on last edited by Kevin Zhong
                              #23

                              Hi all,

                              Finally, I solved this problems.
                              @mrjj, as you mentioned that use

                              item->update()
                              

                              WORKs.

                              My code is a little bit complex, all the item were originated from a template:

                              template <typename T, typename Event>
                              class DeviceEventHandler : public Event, public QObject
                              

                              At the beginning, I try to update the from the template, it doesn't work.
                              Then I move the

                              update()
                              

                              method in the all the subclass, then the pixmap can be updated automatically.

                              So, really thanks for your patience and kindly support.

                              Have a nice weekend.

                              PS: Be honest, I am newbie in Qt area and I got so kindly support. I really appreciate your kindness. :)

                              BRs
                              Kevin

                              mrjjM 1 Reply Last reply
                              2
                              • K Kevin Zhong

                                Hi all,

                                Finally, I solved this problems.
                                @mrjj, as you mentioned that use

                                item->update()
                                

                                WORKs.

                                My code is a little bit complex, all the item were originated from a template:

                                template <typename T, typename Event>
                                class DeviceEventHandler : public Event, public QObject
                                

                                At the beginning, I try to update the from the template, it doesn't work.
                                Then I move the

                                update()
                                

                                method in the all the subclass, then the pixmap can be updated automatically.

                                So, really thanks for your patience and kindly support.

                                Have a nice weekend.

                                PS: Be honest, I am newbie in Qt area and I got so kindly support. I really appreciate your kindness. :)

                                BRs
                                Kevin

                                mrjjM Offline
                                mrjjM Offline
                                mrjj
                                Lifetime Qt Champion
                                wrote on last edited by
                                #24

                                @Kevin-Zhong

                                Hi
                                You are most welcome. we do like Qt newbies here :)

                                It was a bit odd with update() but good you found the solution.
                                Still not sure why it didn't trigger inside SetStatus :)
                                Good weekend to you too

                                1 Reply Last reply
                                1

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