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Thread: QAbstractProxyModel for 'Group By' -- works but arrow keys don't !?

  1. 4th August 2010, 18:31 #1
    liversedge
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    Question QAbstractProxyModel for 'Group By' -- works but arrow keys don't !?

    I've worked on a QAbstractProxyModel to group source model data into a tree, based upon specifying a column to group by.

    It works a charm, and all in all I'm happy.

    BUT...

    Arrow keys no longer work and I really cannot work out why?

    Any hints?

    Qt Code: 
    1. // Proxy model for doing groupBy
    2. class GroupByModel : public QAbstractProxyModel
    3. {
    4.     Q_OBJECT
    5.  
    6. private:
    7.     int groupBy;
    8.  
    9.     QList<QString> groups;
    10.     QList<QModelIndex> groupIndexes;
    11.     QMap<QString, QVector<int>*> groupToSourceRow;
    12.     QVector<int> sourceRowToGroupRow;
    13.  
    14. public:
    15.  
    16.     GroupByModel(QObject *parent = NULL) : QAbstractProxyModel(parent), groupBy(-1) {
    17.         setParent(parent);
    18.     }
    19.     ~GroupByModel() {}
    20.  
    21.     void setSourceModel(QAbstractItemModel *model) {
    22.         QAbstractProxyModel::setSourceModel(model);
    23.         setGroupBy(groupBy);
    24.     }
    25.  
    26.     QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const {
    27.         if (parent.isValid()) {
    28.             return createIndex(row,column, (void*)&groupIndexes[parent.row()]);
    29.         } else {
    30.             if (column == 0)
    31.                 return groupIndexes[row];
    32.             else {
    33.                 return createIndex(row,column,NULL);
    34.             }
    35.         }
    36.     }
    37.  
    38.     QModelIndex parent(const QModelIndex &index) const {
    39.         // parent should be encoded in the index if we supplied it, if
    40.         // we didn't then return a duffer
    41.         if (index == QModelIndex() || index.internalPointer() == NULL) {
    42.             return QModelIndex();
    43.         } else if (index.column()) {
    44.             return QModelIndex();
    45.         }  else {
    46.             return *static_cast<QModelIndex*>(index.internalPointer());
    47.         }
    48.     }
    49.  
    50.     QModelIndex mapToSource(const QModelIndex &proxyIndex) const {
    51.  
    52.         if (proxyIndex.internalPointer() != NULL) {
    53.  
    54.             int groupNo = ((QModelIndex*)proxyIndex.internalPointer())->row();
    55.             if (groupNo < 0 || groupNo >= groups.count() || proxyIndex.column() == 0) {
    56.                 return QModelIndex();
    57.             }
    58.  
    59.             return sourceModel()->index(groupToSourceRow.value(groups[groupNo])->at(proxyIndex.row()),
    60.                                         proxyIndex.column()-1, // accomodate virtual column
    62.         } 
    63.         return QModelIndex();
    64.     }
    65.  
    66.     QModelIndex mapFromSource(const QModelIndex &sourceIndex) const {
    67.  
    68.         // which group did we put this row into?
    69.         QString group = whichGroup(sourceIndex.row());
    70.         int groupNo = groups.indexOf(group);
    71.  
    72.         if (groupNo < 0) {
    73.             return QModelIndex();
    74.         } else {
    75.             QModelIndex *p = new QModelIndex(createIndex(groupNo, 0, NULL));
    76.             return createIndex(sourceRowToGroupRow[sourceIndex.row()], sourceIndex.column()+1, &p); // accomodate virtual column
    77.         } 
    78.     }
    79.  
    80.     QVariant data(const QModelIndex &proxyIndex, int role = Qt::DisplayRole) const {
    81.  
    82.         if (!proxyIndex.isValid()) return QVariant();
    83.  
    84.         QVariant returning;
    85.  
    86.         // if we are not at column 0 or we have a parent
    87.         //if (proxyIndex.internalPointer() != NULL || proxyIndex.column() > 0) {
    88.         if (proxyIndex.column() > 0) {
    89.  
    90.             returning = sourceModel()->data(mapToSource(proxyIndex), role);
    91.  
    92.         } else if (proxyIndex.internalPointer() == NULL) {
    93.  
    94.             // its our group by!
    95.             if (proxyIndex.row() < groups.count()) {
    96.  
    97.                 // blank values become "(blank)"
    98.                 QString group = groups[proxyIndex.row()];
    99.                 if (group == "") group = QString("(blank)");
    100.  
    101.                 // format the group by with ride count etc
    102.                 if (groupBy != -1) {
    103.                     QString returnString = QString("%1: %2 (%3 rides)")
    104.                                            .arg(sourceModel()->headerData(groupBy, Qt::Horizontal).toString())
    105.                                            .arg(group)
    106.                                            .arg(groupToSourceRow.value(groups[proxyIndex.row()])->count());
    107.                     returning = QVariant(returnString);
    108.                 } else {
    109.                     QString returnString = QString("All %1 rides")
    110.                                            .arg(groupToSourceRow.value(groups[proxyIndex.row()])->count());
    111.                     returning = QVariant(returnString);
    112.                 }
    113.             }
    114.         }
    115.  
    116.         return returning;
    117.  
    118.     }
    119.  
    120.     QVariant headerData (int section, Qt::Orientation orientation, int role = Qt::DisplayRole ) const {
    121.         if (section)
    122.             return sourceModel()->headerData(section-1, orientation, role);
    123.         else
    124.             return QVariant("*");
    125.     }
    126.  
    127.     bool setHeaderData (int section, Qt::Orientation orientation, const QVariant & value, int role = Qt::EditRole) {
    128.         if (section)
    129.             return sourceModel()->setHeaderData(section-1, orientation, value, role);
    130.         else
    131.             return true;
    132.     }
    133.  
    134.     int columnCount(const QModelIndex &/*parent*/ = QModelIndex()) const {
    135.         return sourceModel()->columnCount(QModelIndex())+1; // accomodate virtual group column
    136.     }
    137.  
    138.     int rowCount(const QModelIndex &parent = QModelIndex()) const {
    139.         if (parent == QModelIndex()) {
    140.  
    141.             // top level return count of groups
    142.             return groups.count();
    143.  
    144.         } else if (parent.column() == 0 && parent.internalPointer() == NULL) {
    145.  
    146.             // second level return count of rows for group
    147.             return groupToSourceRow.value(groups[parent.row()])->count();
    148.  
    149.         } else {
    150.  
    151.             // no children any lower
    152.             return 0;
    153.         }
    154.     }
    155.  
    156.     // does this index have children?
    157.     bool hasChildren(const QModelIndex &index) const {
    158.  
    159.         if (index == QModelIndex()) {
    160.  
    161.             // at top
    162.             return (groups.count() > 0);
    163.  
    164.         } else if (index.column() == 0 && index.internalPointer() == NULL) {
    165.  
    166.             // first column - the group bys
    167.             return (groupToSourceRow.value(groups[index.row()])->count() > 0);
    168.  
    169.         } else {
    170.  
    171.             return false;
    172.  
    173.         }
    174.     }
    175.  
    176.     //
    177.     // GroupBy features
    178.     //
    179.     void setGroupBy(int column) {
    180.  
    181.         // shift down
    182.         if (column >= 0) column -= 1;
    183.  
    184.         groupBy = column; // accomodate virtual column
    185.         setGroups();
    186.     }
    187.  
    188.     QString whichGroup(int row) const {
    189.  
    190.         if (groupBy == -1) return tr("All Rides");
    191.         else return groupFromValue(headerData(groupBy+1, Qt::Horizontal).toString(),
    192.                                     sourceModel()->data(sourceModel()->index(row,groupBy)).toString());
    193.  
    194.     }
    195.  
    196.     // implemented in RideNavigator.cpp, to avoid developers
    197.     // from working out how this QAbstractProxy works, or
    198.     // perhaps breaking it by accident ;-)
    199.     QString groupFromValue(QString, QString) const;
    200.  
    201.     void clearGroups() {
    202.         // Wipe current
    203.         QMapIterator<QString, QVector<int>*> i(groupToSourceRow);
    204.         while (i.hasNext()) {
    205.             i.next();
    206.             delete i.value();
    207.         }
    208.         groups.clear();
    209.         groupIndexes.clear();
    210.         groupToSourceRow.clear();
    211.         sourceRowToGroupRow.clear();
    212.     }
    213.  
    214.     int groupCount() {
    215.         return groups.count();
    216.     }
    217.  
    218.     void setGroups() {
    219.  
    220.         // let the views know we're doing this
    221.         beginResetModel();
    222.  
    223.         // wipe whatever is there first
    224.         clearGroups();
    225.  
    226.         if (groupBy >= 0) {
    227.  
    228.             // create a QMap from 'group' string to list of rows in that group
    229.             for (int i=0; i<sourceModel()->rowCount(QModelIndex()); i++) {
    230.                 QString value = whichGroup(i);
    231.  
    232.                 QVector<int> *rows;
    233.                 if ((rows=groupToSourceRow.value(value,NULL)) == NULL) {
    234.                     // add to list of groups
    235.                     rows = new QVector<int>;
    236.                     groupToSourceRow.insert(value, rows);
    237.                 }
    238.  
    239.                 // rowmap is an array corresponding to each row in the
    240.                 // source model, and maps to its row # within the group
    241.                 sourceRowToGroupRow.append(rows->count());
    242.  
    243.                 // add to this groups rows
    244.                 rows->append(i);
    245.             }
    246.  
    247.         } else {
    248.  
    249.             // Just one group by 'All Rides'
    250.             QVector<int> *rows = new QVector<int>;
    251.             for (int i=0; i<sourceModel()->rowCount(QModelIndex()); i++) {
    252.                 rows->append(i);
    253.                 sourceRowToGroupRow.append(i);
    254.             }
    255.             groupToSourceRow.insert("All Rides", rows);
    256.  
    257.         }
    258.  
    259.         // Update list of groups
    260.         int group=0;
    261.         QMapIterator<QString, QVector<int>*> j(groupToSourceRow);
    262.         while (j.hasNext()) {
    263.             j.next();
    264.             groups << j.key();
    265.             groupIndexes << createIndex(group++,0,NULL);
    266.         }
    267.  
    268.         // all done. let the views know everything changed
    269.         endResetModel();
    270.     }
    271. };
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    Many thanks for taking time to look at this! it really is appreciated.

    Cheers,
    Mark
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  2. 4th August 2010, 18:36 #2
    liversedge
    liversedge is offline Novice
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    Default Re: QAbstractProxyModel for 'Group By' -- works but arrow keys don't !?

    I should have mentioned that the arrow keys don't move up and down in a QTreeView when this proxymodel is between the view and the source sqltable.

    Cheers,
    Mark
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  3. 4th August 2010, 20:10 #3
    liversedge
    liversedge is offline Novice
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    Default Re: QAbstractProxyModel for 'Group By' -- works but arrow keys don't !?

    Fixed it ha!

    Because I have a virtual column in column zero, but mapToSource returns an invalid QModelIndex for column zero (because it doesn't exist in the source) then the flags for column zero are empty -- and makes it non-selectable.

    If I provide my own version of ::flags() and make it selectable the arrow keys spring into life. yay!

    here is the bit of code I needed to add, I make the groupby's unselectable since they are just 'headings' not data (if that makes any sense).

    Qt Code: 
    1. Qt::ItemFlags flags ( const QModelIndex & index ) const {
    2.         if (index.internalPointer() == NULL) {
    3.             return Qt::ItemIsEnabled;
    4.         } else {
    5.             return Qt::ItemIsSelectable | Qt::ItemIsEnabled;
    6.         }   
    7.     }
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