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How can I center QCheckBox in QTableView?

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  • C CuriousPan
    12 Nov 2021, 13:28

    @Christian-Ehrlicher, hey, this is a really nice example, but I don't understand what 'role' should I use in the model to center the checkbox, because now it's in the left top corner.

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    JonB
    wrote on 12 Nov 2021, 13:47 last edited by JonB 11 Dec 2021, 13:47
    #7

    @CuriousPan
    The code at @Christian-Ehrlicher's https://wiki.qt.io/Center_a_QCheckBox_or_Decoration_in_an_Itemview tells you what role it is using

    As alignment indicator the Qt::TextAlignmentRole is 'misused' since no text is drawn for the cell.

    and you can see it in the code you are copying:

    opt.rect = QStyle::alignedRect(opt.direction, index.data(Qt::TextAlignmentRole).value<Qt::Alignment>(), rect.size(), opt.rect);

    Or use your own role if you don't want to use that.

    C 1 Reply Last reply 12 Nov 2021, 13:55
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    • J JonB
      12 Nov 2021, 13:47

      @CuriousPan
      The code at @Christian-Ehrlicher's https://wiki.qt.io/Center_a_QCheckBox_or_Decoration_in_an_Itemview tells you what role it is using

      As alignment indicator the Qt::TextAlignmentRole is 'misused' since no text is drawn for the cell.

      and you can see it in the code you are copying:

      opt.rect = QStyle::alignedRect(opt.direction, index.data(Qt::TextAlignmentRole).value<Qt::Alignment>(), rect.size(), opt.rect);

      Or use your own role if you don't want to use that.

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      CuriousPan
      wrote on 12 Nov 2021, 13:55 last edited by CuriousPan 11 Dec 2021, 13:55
      #8

      @JonB, yeees, I understood this and I was using Qt::TextAlignmentRole and returning Qt::AlignCenter, but for some reason it's not aligned :(
      21cc5073-d844-4a87-ac13-f40a60c0cea3-image.png

      3076c24a-05b5-476e-9154-09e658caebab-image.png

      J C 2 Replies Last reply 12 Nov 2021, 13:57
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      • C CuriousPan
        12 Nov 2021, 13:55

        @JonB, yeees, I understood this and I was using Qt::TextAlignmentRole and returning Qt::AlignCenter, but for some reason it's not aligned :(
        21cc5073-d844-4a87-ac13-f40a60c0cea3-image.png

        3076c24a-05b5-476e-9154-09e658caebab-image.png

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        JonB
        wrote on 12 Nov 2021, 13:57 last edited by JonB 11 Dec 2021, 13:58
        #9

        @CuriousPan
        I do not know about the behaviour of the delegate. But if you want to know to know whether it is being "triggered" and recognises the role in question put in a qDebug() statement (in the delegate) to find out.

        C 1 Reply Last reply 12 Nov 2021, 13:58
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        • C CuriousPan
          12 Nov 2021, 13:55

          @JonB, yeees, I understood this and I was using Qt::TextAlignmentRole and returning Qt::AlignCenter, but for some reason it's not aligned :(
          21cc5073-d844-4a87-ac13-f40a60c0cea3-image.png

          3076c24a-05b5-476e-9154-09e658caebab-image.png

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          CuriousPan
          wrote on 12 Nov 2021, 13:57 last edited by
          #10
          This post is deleted!
          1 Reply Last reply
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          • J JonB
            12 Nov 2021, 13:57

            @CuriousPan
            I do not know about the behaviour of the delegate. But if you want to know to know whether it is being "triggered" and recognises the role in question put in a qDebug() statement (in the delegate) to find out.

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            CuriousPan
            wrote on 12 Nov 2021, 13:58 last edited by
            #11

            @JonB, yes, it's defenitely triggered.

            J 1 Reply Last reply 12 Nov 2021, 14:04
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            • C CuriousPan
              12 Nov 2021, 13:58

              @JonB, yes, it's defenitely triggered.

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              JonB
              wrote on 12 Nov 2021, 14:04 last edited by
              #12

              @CuriousPan
              Find all your occurrences of

              QStyle::alignedRect(opt.direction, index.data(Qt::TextAlignmentRole).value<Qt::Alignment>(), rect.size(), opt.rect)
              

              and qDebug() << index.data(Qt::TextAlignmentRole).value<Qt::Alignment>().

              C 1 Reply Last reply 12 Nov 2021, 14:07
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              • J JonB
                12 Nov 2021, 14:04

                @CuriousPan
                Find all your occurrences of

                QStyle::alignedRect(opt.direction, index.data(Qt::TextAlignmentRole).value<Qt::Alignment>(), rect.size(), opt.rect)
                

                and qDebug() << index.data(Qt::TextAlignmentRole).value<Qt::Alignment>().

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                CuriousPan
                wrote on 12 Nov 2021, 14:07 last edited by
                #13

                @JonB, it always retruns QFlags<Qt::AlignmentFlag>() 1 which is Qt::DecorationRole, right?

                R J 2 Replies Last reply 12 Nov 2021, 14:12
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                • C CuriousPan
                  12 Nov 2021, 14:07

                  @JonB, it always retruns QFlags<Qt::AlignmentFlag>() 1 which is Qt::DecorationRole, right?

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                  raven-worx
                  Moderators
                  wrote on 12 Nov 2021, 14:12 last edited by
                  #14

                  @CuriousPan said in How can I center QCheckBox in QTableView?:

                  it always retruns QFlagsQt::AlignmentFlag() 1 which is Qt::DecorationRole, right

                  the Qt::AlignmentFlag flags/enum doesnt contain Qt::DecorationRole, so no
                  https://doc.qt.io/qt-5/qt.html#AlignmentFlag-enum

                  --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
                  If you have a question please use the forum so others can benefit from the solution in the future

                  C 2 Replies Last reply 12 Nov 2021, 14:15
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                  • R raven-worx
                    12 Nov 2021, 14:12

                    @CuriousPan said in How can I center QCheckBox in QTableView?:

                    it always retruns QFlagsQt::AlignmentFlag() 1 which is Qt::DecorationRole, right

                    the Qt::AlignmentFlag flags/enum doesnt contain Qt::DecorationRole, so no
                    https://doc.qt.io/qt-5/qt.html#AlignmentFlag-enum

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                    CuriousPan
                    wrote on 12 Nov 2021, 14:15 last edited by
                    #15

                    @raven-worx, oh, I see. You're right. Anyway, why is that so?

                    1 Reply Last reply
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                    • R raven-worx
                      12 Nov 2021, 14:12

                      @CuriousPan said in How can I center QCheckBox in QTableView?:

                      it always retruns QFlagsQt::AlignmentFlag() 1 which is Qt::DecorationRole, right

                      the Qt::AlignmentFlag flags/enum doesnt contain Qt::DecorationRole, so no
                      https://doc.qt.io/qt-5/qt.html#AlignmentFlag-enum

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                      CuriousPan
                      wrote on 12 Nov 2021, 14:20 last edited by
                      #16

                      @raven-worx, wait! I confused you and me. This '1' is my custom printout. So what you suggested printing just gives following output: QFlags<Qt::AlignmentFlag>()

                      J 1 Reply Last reply 12 Nov 2021, 14:26
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                      • C CuriousPan
                        12 Nov 2021, 14:20

                        @raven-worx, wait! I confused you and me. This '1' is my custom printout. So what you suggested printing just gives following output: QFlags<Qt::AlignmentFlag>()

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                        JonB
                        wrote on 12 Nov 2021, 14:26 last edited by JonB 11 Dec 2021, 14:26
                        #17

                        @CuriousPan
                        Qt::AlignLeft 0x0001 Aligns with the left edge.

                        So this value 1 is left alignment, just as per your picture, and no kind of centering specified, which would have value 4.

                        C 1 Reply Last reply 12 Nov 2021, 14:28
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                        • J JonB
                          12 Nov 2021, 14:26

                          @CuriousPan
                          Qt::AlignLeft 0x0001 Aligns with the left edge.

                          So this value 1 is left alignment, just as per your picture, and no kind of centering specified, which would have value 4.

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                          CuriousPan
                          wrote on 12 Nov 2021, 14:28 last edited by
                          #18

                          @JonB, yeah, it is, but as I said, no numbers are printed.
                          f3a89a98-7f28-4581-955b-721b64fbfc0e-image.png

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                          • C CuriousPan
                            12 Nov 2021, 14:07

                            @JonB, it always retruns QFlags<Qt::AlignmentFlag>() 1 which is Qt::DecorationRole, right?

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                            JonB
                            wrote on 12 Nov 2021, 14:29 last edited by JonB 11 Dec 2021, 14:30
                            #19

                            @CuriousPan said in How can I center QCheckBox in QTableView?:

                            @JonB, it always retruns QFlagsQt::AlignmentFlag() 1 which is Qt::DecorationRole, right?

                            That's what you wrote. See that 1? Can you please concentrate on one thing at a time.

                            C 1 Reply Last reply 12 Nov 2021, 14:30
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                            • J JonB
                              12 Nov 2021, 14:29

                              @CuriousPan said in How can I center QCheckBox in QTableView?:

                              @JonB, it always retruns QFlagsQt::AlignmentFlag() 1 which is Qt::DecorationRole, right?

                              That's what you wrote. See that 1? Can you please concentrate on one thing at a time.

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                              CuriousPan
                              wrote on 12 Nov 2021, 14:30 last edited by
                              #20

                              @JonB, yep, I can. I'm really sorry for confusing you. No 1 is printed, it's just my mistake.

                              J 1 Reply Last reply 12 Nov 2021, 14:34
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                              • C CuriousPan
                                12 Nov 2021, 14:30

                                @JonB, yep, I can. I'm really sorry for confusing you. No 1 is printed, it's just my mistake.

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                                JonB
                                wrote on 12 Nov 2021, 14:34 last edited by
                                #21

                                @CuriousPan
                                So that would be the value for left-align. Either you are not setting or returning the desired "center" flag on your item for the Qt::TextAlignmentRole --- you have to do that if you want it centered, that's what the code does --- or you are not looking at the right item/index.

                                C 1 Reply Last reply 12 Nov 2021, 14:41
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                                • J JonB
                                  12 Nov 2021, 14:34

                                  @CuriousPan
                                  So that would be the value for left-align. Either you are not setting or returning the desired "center" flag on your item for the Qt::TextAlignmentRole --- you have to do that if you want it centered, that's what the code does --- or you are not looking at the right item/index.

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                                  CuriousPan
                                  wrote on 12 Nov 2021, 14:41 last edited by CuriousPan 11 Dec 2021, 14:42
                                  #22

                                  @JonB, I guess you're right, but, as I showed on this screenshot: fb7e083f-38ea-4de7-8c55-b8b77b24f946-image.png
                                  I'm using the correct role and column is defenitely correct (checked usingqDebug()).

                                  J 1 Reply Last reply 12 Nov 2021, 14:46
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                                  • C CuriousPan
                                    12 Nov 2021, 14:41

                                    @JonB, I guess you're right, but, as I showed on this screenshot: fb7e083f-38ea-4de7-8c55-b8b77b24f946-image.png
                                    I'm using the correct role and column is defenitely correct (checked usingqDebug()).

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                                    JonB
                                    wrote on 12 Nov 2021, 14:46 last edited by JonB 11 Dec 2021, 14:46
                                    #23

                                    @CuriousPan

                                    • Print out index.column() in the delegate.
                                    • Print out RecurrentColumn.
                                    • Put a qDebug() just above return Qt::AlignCenter in your "screenshot" to make sure it's being hit.
                                    • Please don't paste code as screenshots, paste it as code. Show where you have that code and what is above the extract you show.
                                    C 1 Reply Last reply 12 Nov 2021, 15:01
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                                    • J JonB
                                      12 Nov 2021, 14:46

                                      @CuriousPan

                                      • Print out index.column() in the delegate.
                                      • Print out RecurrentColumn.
                                      • Put a qDebug() just above return Qt::AlignCenter in your "screenshot" to make sure it's being hit.
                                      • Please don't paste code as screenshots, paste it as code. Show where you have that code and what is above the extract you show.
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                                      CuriousPan
                                      wrote on 12 Nov 2021, 15:01 last edited by CuriousPan 11 Dec 2021, 15:05
                                      #24

                                      @JonB

                                      • index.column() in the delegate has the proper number. 4 in my case as long as it is 4th (starting from 0) column in the table view.
                                      • What do you mean by printing RecurrentColumn?
                                      //checking other roles
                                      } else if (index.isValid() && role == Qt::TextAlignmentRole) { 
                                               switch (index.column()) { 
                                               case RecurrentColumn: 
                                                    qDebug() << "Hit"; 
                                                    return Qt::AlignCenter; 
                                               case TotalColumn: 
                                                    return {Qt::AlignRight | Qt::AlignVCenter}; 
                                               case PlnTotalColumn: 
                                                    return {Qt::AlignRight | Qt::AlignVCenter}; 
                                               return Qt::AlignCenter; 
                                               }
                                      }
                                      // "Hit" is getting printed.
                                      
                                      • Okay, will try to value your time and effort :)
                                      C 1 Reply Last reply 12 Nov 2021, 15:50
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                                      • C CuriousPan
                                        12 Nov 2021, 15:01

                                        @JonB

                                        • index.column() in the delegate has the proper number. 4 in my case as long as it is 4th (starting from 0) column in the table view.
                                        • What do you mean by printing RecurrentColumn?
                                        //checking other roles
                                        } else if (index.isValid() && role == Qt::TextAlignmentRole) { 
                                                 switch (index.column()) { 
                                                 case RecurrentColumn: 
                                                      qDebug() << "Hit"; 
                                                      return Qt::AlignCenter; 
                                                 case TotalColumn: 
                                                      return {Qt::AlignRight | Qt::AlignVCenter}; 
                                                 case PlnTotalColumn: 
                                                      return {Qt::AlignRight | Qt::AlignVCenter}; 
                                                 return Qt::AlignCenter; 
                                                 }
                                        }
                                        // "Hit" is getting printed.
                                        
                                        • Okay, will try to value your time and effort :)
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                                        CuriousPan
                                        wrote on 12 Nov 2021, 15:50 last edited by CuriousPan 11 Dec 2021, 15:51
                                        #25

                                        @CuriousPan I have fixed the issue.
                                        I used pretty dirty, but working trick: set Qt::AlignedCenter right in the delegate:

                                        void CenteredCheckBoxDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
                                        {
                                            QStyleOptionViewItem opt = option;
                                            const QWidget *widget = option.widget;
                                            initStyleOption(&opt, index);
                                            QStyle *style = opt.widget ? opt.widget->style() : QApplication::style();
                                            style->drawPrimitive(QStyle::PE_PanelItemViewItem, &opt, painter, widget);
                                            if (opt.features & QStyleOptionViewItem::HasCheckIndicator) {
                                                switch (opt.checkState) {
                                                case Qt::Unchecked:
                                                    opt.state |= QStyle::State_Off;
                                                    break;
                                                case Qt::PartiallyChecked:
                                                    opt.state |= QStyle::State_NoChange;
                                                    break;
                                                case Qt::Checked:
                                                    opt.state |= QStyle::State_On;
                                                    break;
                                                }
                                                auto rect = style->subElementRect(QStyle::SE_ItemViewItemCheckIndicator, &opt, widget);
                                                opt.rect = QStyle::alignedRect(opt.direction, Qt::AlignCenter/*index.data(Qt::TextAlignmentRole).value<Qt::Alignment>()*/, rect.size(), opt.rect);
                                                opt.state = opt.state & ~QStyle::State_HasFocus;
                                                style->drawPrimitive(QStyle::PE_IndicatorItemViewItemCheck, &opt, painter, widget);
                                            } else if (!opt.icon.isNull()) {
                                                // draw the icon
                                                QRect iconRect = style->subElementRect(QStyle::SE_ItemViewItemDecoration, &opt, widget);
                                                iconRect = QStyle::alignedRect(opt.direction, Qt::AlignCenter/*index.data(Qt::TextAlignmentRole).value<Qt::Alignment>()*/, iconRect.size(), opt.rect);
                                                QIcon::Mode mode = QIcon::Normal;
                                                if (!(opt.state & QStyle::State_Enabled))
                                                    mode = QIcon::Disabled;
                                                else if (opt.state & QStyle::State_Selected)
                                                    mode = QIcon::Selected;
                                                QIcon::State state = opt.state & QStyle::State_Open ? QIcon::On : QIcon::Off;
                                                opt.icon.paint(painter, iconRect, opt.decorationAlignment, mode, state);
                                            } else {
                                                QStyledItemDelegate::paint(painter, option, index);
                                            }
                                        }
                                        
                                        bool CenteredCheckBoxDelegate::editorEvent(QEvent *event, QAbstractItemModel *model, const QStyleOptionViewItem &option, const QModelIndex &index)
                                        {
                                            Q_ASSERT(event);
                                            Q_ASSERT(model);
                                            // make sure that the item is checkable
                                            Qt::ItemFlags flags = model->flags(index);
                                            if (!(flags & Qt::ItemIsUserCheckable) || !(option.state & QStyle::State_Enabled) || !(flags & Qt::ItemIsEnabled))
                                                return false;
                                            // make sure that we have a check state
                                            QVariant value = index.data(Qt::CheckStateRole);
                                            if (!value.isValid())
                                                return false;
                                            const QWidget *widget = option.widget;
                                            QStyle *style = option.widget ? widget->style() : QApplication::style();
                                            // make sure that we have the right event type
                                            if ((event->type() == QEvent::MouseButtonRelease) || (event->type() == QEvent::MouseButtonDblClick) || (event->type() == QEvent::MouseButtonPress)) {
                                                QStyleOptionViewItem viewOpt(option);
                                                initStyleOption(&viewOpt, index);
                                                QRect checkRect = style->subElementRect(QStyle::SE_ItemViewItemCheckIndicator, &viewOpt, widget);
                                                checkRect = QStyle::alignedRect(viewOpt.direction, Qt::AlignCenter/*index.data(Qt::TextAlignmentRole).value<Qt::Alignment>()*/, checkRect.size(), viewOpt.rect);
                                                QMouseEvent *me = static_cast<QMouseEvent *>(event);
                                                if (me->button() != Qt::LeftButton || !checkRect.contains(me->pos()))
                                                    return false;
                                                if ((event->type() == QEvent::MouseButtonPress) || (event->type() == QEvent::MouseButtonDblClick))
                                                    return true;
                                            } else if (event->type() == QEvent::KeyPress) {
                                                if (static_cast<QKeyEvent *>(event)->key() != Qt::Key_Space && static_cast<QKeyEvent *>(event)->key() != Qt::Key_Select)
                                                    return false;
                                            } else {
                                                return false;
                                            }
                                            Qt::CheckState state = static_cast<Qt::CheckState>(value.toInt());
                                            if (flags & Qt::ItemIsUserTristate)
                                                state = ((Qt::CheckState)((state + 1) % 3));
                                            else
                                                state = (state == Qt::Checked) ? Qt::Unchecked : Qt::Checked;
                                            return model->setData(index, state, Qt::CheckStateRole);
                                        }
                                        
                                        

                                        Thanks everyone who took part in the discussion.

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