QTreeView, how to get the scrollbars when resizing if we don't use ElideMode?

mbruel

ok I've done a simple example of my code:

Here is tree.h

#ifndef TREE_H
#define TREE_H

#include <QStandardItemModel>
#include <QStyledItemDelegate>


enum class TreeItemType {
    TreeElementItem  = 0x1,
    TreeTypeItem     = 0x10
};

class TreeItem : public QStandardItem
{
public:
    TreeItem(const QString &txt, TreeItemType type = TreeItemType::TreeElementItem)
        : QStandardItem(), _type(type), _txt(txt) {}
    virtual ~TreeItem() = default;

    QVariant data( int role = Qt::UserRole ) const override;
    TreeItemType getType() const {return _type;}
private:
    const TreeItemType _type;
    const QString      _txt;
};



class TreeItemDelegate : public QStyledItemDelegate
{
public:
    TreeItemDelegate()  = default;
    ~TreeItemDelegate() = default;

    void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const override;
    QSize sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const override;
};


class TreeModel : public QStandardItemModel
{
    Q_OBJECT

public:
    TreeModel()  = default;
    ~TreeModel() = default;

    Qt::ItemFlags flags(const QModelIndex& index) const override;

    void load();
};

#endif // TREE_H

Tree.cpp

#include "tree.h"

QVariant TreeItem::data(int role) const
{
    switch (role) {
    case Qt::DisplayRole:
    {
        QString msg(_txt);
        if (_type == TreeItemType::TreeTypeItem)
            msg += QString(" (%1)").arg(rowCount());
        return msg;
    }
    default:
        return QStandardItem::data(role);
    }
}

void TreeItemDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    QStandardItem *item = static_cast<const TreeModel*>(index.model())->itemFromIndex(index);
    if (!item)
        return;

    QStyleOptionViewItem myOption = option;
    myOption.textElideMode = Qt::ElideNone;

    if (static_cast<TreeItem*>(item)->getType() == TreeItemType::TreeTypeItem)
    {
        myOption.font.setBold(true);
        myOption.decorationSize = QSize(24,24);
    }

    QStyledItemDelegate::paint(painter, myOption, index);
}

QSize TreeItemDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    QSize size = QStyledItemDelegate::sizeHint(option, index);

    QStandardItem *item = static_cast<const TreeModel*>(index.model())->itemFromIndex(index);
    if (item)
    {
        if (static_cast<TreeItem*>(item)->getType() == TreeItemType::TreeTypeItem)
            size.setHeight(26);
        else
            size.setHeight(18);
    }

    return size;
}



Qt::ItemFlags TreeModel::flags(const QModelIndex& index) const
{
    QStandardItem *item = itemFromIndex(index);
    if (!item)
        return 0;

    TreeItemType itemType = static_cast<TreeItemType>(item->data(Qt::UserRole).toInt());
    if (itemType == TreeItemType::TreeTypeItem)
        return Qt::ItemIsEnabled|Qt::ItemIsSelectable;
    else
        return Qt::ItemIsEnabled|Qt::ItemIsSelectable|Qt::ItemIsEditable;
}

void TreeModel::load()
{
    TreeItem *project = new TreeItem("Project");
    invisibleRootItem()->appendRow(project);

    TreeItem *firstType = new TreeItem("First Type", TreeItemType::TreeTypeItem);
    project->appendRow(firstType);

    for (ushort i=0 ; i < 5 ; ++i)
    {
        TreeItem *someItem = new TreeItem(QString("Some Items number #%1").arg(i));
        firstType->appendRow(someItem);
    }

    TreeItem *secondType = new TreeItem("Second Type a bit longer", TreeItemType::TreeTypeItem);
    project->appendRow(secondType);

}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class TreeModel;
class QAbstractItemDelegate;
class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    Ui::MainWindow        *_ui;
    TreeModel             *_treeModel;
    QAbstractItemDelegate *_treeItemDelegate;
};

#endif // MAINWINDOW_H

and mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QLabel>
#include "tree.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    _ui(new Ui::MainWindow), _treeModel(new TreeModel()), _treeItemDelegate(new TreeItemDelegate())
{
    _ui->setupUi(this);

    QLabel *editor = new QLabel("<h3>Editor</h3>", this);
    _ui->splitter->addWidget(editor);

    _ui->splitter->setCollapsible(0, false);
    _ui->splitter->setCollapsible(1, false);
    _ui->splitter->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);


    _ui->treeView->setModel(_treeModel);
    if (_treeItemDelegate)
        _ui->treeView->setItemDelegate(_treeItemDelegate);

    _treeModel->load();
}

MainWindow::~MainWindow()
{
    delete _ui;
}

and the mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>756</width>
    <height>565</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralWidget">
   <widget class="QSplitter" name="splitter">
    <property name="geometry">
     <rect>
      <x>10</x>
      <y>10</y>
      <width>661</width>
      <height>491</height>
     </rect>
    </property>
    <property name="orientation">
     <enum>Qt::Horizontal</enum>
    </property>
    <widget class="QTreeView" name="treeView"/>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menuBar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>756</width>
     <height>19</height>
    </rect>
   </property>
   <widget class="QMenu" name="menuFile">
    <property name="title">
     <string>File</string>
    </property>
   </widget>
   <widget class="QMenu" name="menuUndoStack">
    <property name="title">
     <string>UndoStack</string>
    </property>
    <addaction name="actionUndo"/>
    <addaction name="actionRedo"/>
   </widget>
   <addaction name="menuFile"/>
   <addaction name="menuUndoStack"/>
  </widget>
  <widget class="QToolBar" name="mainToolBar">
   <attribute name="toolBarArea">
    <enum>TopToolBarArea</enum>
   </attribute>
   <attribute name="toolBarBreak">
    <bool>false</bool>
   </attribute>
  </widget>
  <widget class="QStatusBar" name="statusBar"/>
  <action name="actionUndo">
   <property name="text">
    <string>Undo</string>
   </property>
  </action>
  <action name="actionRedo">
   <property name="text">
    <string>Redo</string>
   </property>
  </action>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources/>
 <connections/>
</ui>

My problem is that I don't know how I could make the horizontal scrollbar kicks in as soon as one Item of the TreeView is not fully visible.
alt text

Any idea how I could achieve it? I guess it is something that should be simple...

PS: another problem I have is that my QSlider is not taking the full area of my window. If I go fullscreen, the TreeView is not resizing.

jsulm

@mbruel said in QTreeView, how to get the scrollbars when resizing if we don't use ElideMode?:

QSlider is not taking the full area of my window

Is your QSlider in a layout?

mbruel

Well I'm not sure...
I'm using Qt Creator designer. In the Central Widget I've added my TreeView and another Widget then I've selected both and click on "Layout Horizontally in a Splitter".
I was thinking the Splitter would be the layout of the MainWindow but I guess not...

You can find the Qt Project here

jsulm

@mbruel No, the splitter is the "layout" of the two widgets. Press somewhere in your central widget and press "Lay Out in a Grid".

mbruel

@jsulm
ok thanks, yes, it solves this global size issue.
Any idea on the original issue: how to make the horizontal scrollbar of the TreeView kicks in when some of its items are not fully visible?

mbruel

@SGaist
Any ideas for this issue?
I've posted the code and a zip of the project.

mpergand

@mbruel said in QTreeView, how to get the scrollbars when resizing if we don't use ElideMode?:

In Designer, uncheck "headerStretchLastSection"

mbruel

@mpergand
Well this make it worst. My items are all the time truncated even when there is space in the QTreeView.
alt text

It seems the size of the viewport is the one of the header? how could the size of the longest row? and set it to be this? I found it strange that there is not an option to do this automatically...

mbruel

It seems that it is the header DefaultSectionSize that defines when the scrollbar will kicks in.
I've tried to use the visualRect of my items but I'm getting a invalid one for all the items except the first one...

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    _ui(new Ui::MainWindow), _treeModel(new TreeModel()), _treeItemDelegate(new TreeItemDelegate())
{
    _ui->setupUi(this);
....

    int maxWidth = 0;
    _setTreeViewMaxWith(maxWidth);

    _ui->treeView->header()->setDefaultSectionSize(maxWidth);
}

#include <QDebug>
void MainWindow::_setTreeViewMaxWith(int &maxWidth, QModelIndex parent)
{
    for(int r = 0; r < _treeModel->rowCount(parent); ++r)
    {
        QModelIndex index = _treeModel->index(r, 0, parent);
        int width = _ui->treeView->visualRect(index).width();
qDebug() << "width row " << r << " : "   << width;
        if (width > maxWidth)
            maxWidth = width;

        if( _treeModel->hasChildren(index) )
            _setTreeViewMaxWith(maxWidth, index);
    }
}

Here is the output:
width row 0 : 180
width row 0 : 0
width row 0 : 0
width row 1 : 0
width row 2 : 0
width row 3 : 0
width row 4 : 0
width row 1 : 0

mpergand

_ui->treeView->header()->setSectionResizeMode(QHeaderView::ResizeToContents);

Work well with elideMode ...
Infinite loop detected :)

Well, the only solution seems to resize the column yourself, you can memorize the larger item in TreeItemDelegate::sizeHint
and set the column width accordingly.

mbruel

@mpergand
Cool, thanks, good advise :)
You're right, instead of resizing the header, I can just resize the first column.
What I've done is that my Delegate emit a signal in SizeHint when the size max increase. My MainWindow catch the signal and resize the column accordingly taking the indent of the index in consideration...
This works but I'm quite surprised that we've to do it manually and that the functionality is not offered by the QTreeView directly.

Here is my code for the people interested

QSize TreeItemDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    QStyleOptionViewItem myOption = option;
    myOption.textElideMode = Qt::ElideNone;

    QStandardItem *item = static_cast<const TreeModel*>(index.model())->itemFromIndex(index);
    if (static_cast<TreeItem*>(item)->getType() == TreeItemType::TreeTypeItem)
    {
        myOption.font.setBold(true);
        myOption.decorationSize = QSize(24,24);
    }

    QSize size = QStyledItemDelegate::sizeHint(myOption, index);
    if (size.width() > _maxWidth)
    {
        _maxWidth = size.width();
        emit maxWidthIncreased(_maxWidth, index);
    }

    if (item)
    {
        if (static_cast<TreeItem*>(item)->getType() == TreeItemType::TreeTypeItem)
            size.setHeight(26);
        else
            size.setHeight(18);
    }

    return size;
}

and in MainWindow:

void MainWindow::handleTreeViewMaxWidthChanged(int maxWidth, QModelIndex index)
{
    int indent = _ui->treeView->indentation();
    while (index.parent().isValid())
    {
        indent += _ui->treeView->indentation();
        index = index.parent();
    }

    qDebug() << "Max width from Delegate: " << maxWidth << ", indent: " << indent;
    _ui->treeView->setColumnWidth(0, maxWidth+indent);
}

PS: for this to work, TreeItemDelegate::_maxWidth is mutable and the signal is const

class TreeItemDelegate : public QStyledItemDelegate
{
    Q_OBJECT
...
signals:
    void maxWidthIncreased(int maxSize, QModelIndex index) const;

private:
    mutable int _maxWidth;
};

mbruel

@mpergand said in QTreeView, how to get the scrollbars when resizing if we don't use ElideMode?:

Infinite loop detected :)

where would you see an infinite loop?

mbruel

Following another this other thread about customizing delegates with the display of the icons, here is a more efficient version of this one:

QSize TreeItemDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    QSize size = QStyledItemDelegate::sizeHint(option, index);
    if (size.width() > _maxWidth)
    {
        _maxWidth = size.width();
        emit maxWidthIncreased(_maxWidth, index);
    }
    return size;
}

void TreeItemDelegate::initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const
{
    QStyledItemDelegate::initStyleOption(option, index);
    option->textElideMode = Qt::ElideNone;

    TreeItem *item = nullptr;
    if (_useProxy)
        item = static_cast<const TreeProxyModel*>(index.model())->itemFromIndex(index);
    else
        item = static_cast<const TreeModel*>(index.model())->itemFromIndex(index);

    if (item && static_cast<TreeItem*>(item)->isRootItem())
    {
//        option->palette.setColor(QPalette::Normal, QPalette::Text,Qt::blue);
        option->font.setBold(true);
        option->decorationSize = QSize(24,24);
    }
}

No need to override the paint method but instead the protected initStyleOption

SGaist

Thanks for the feedback !