Highlighting selected row to be Bold in QTreeView

[qwasder85]

@sierdzio This. Do this.

[sierdzio]

@qwasder85 said in Highlighting selected row to be Bold in QTreeView:

@sierdzio This. Do this.

Hm?

[sogo]

Hi @sierdzio Oh this is new for me, please give me sometime to check and play with it a little and see how can I implement bold row on double click on any row and if I have any question, I'll ping here. Here is the updated code, were some issues in there:

QVariant FileSystem::data(const QModelIndex &index, int role) const
{
  int row = index.row();
  int col = index.column();
  const bool shouldBeBold = (row == 0 && col == 0);
  if (role == Qt::FontRole && shouldBeBold) {
    QFont boldFont;
    boldFont.setBold(true);
    return boldFont;
  } else {
    return QFileSystemModel::data(index, role); // This will call the original QFileSystem::data method
  }
}

@JonB thanks for your update too

I have one question though, I was reading the QFileSystemModel source code and I didn't see any case of QT::FontRole in qfilesystemmodel.cpp "::data" method. What confuses me is that in this code this statement "if (role == QT::FontRole && shouldBeBold)", how is it checking this.

[sierdzio]

@sogo said in Highlighting selected row to be Bold in QTreeView:

I have one question though, I was reading the QFileSystemModel source code and I didn't see any case of QT::FontRole in qfilesystemmodel.cpp "::data" method.

In general, this flag is rarely used. I think most of the time, delegates just take default font from QPalette / QSS.

What confuses me is that in this code this statement "if (role == QT::FontRole && shouldBeBold)", how is it checking this.

I don't understand your question, sorry. How is what checking this?

[JonB]

@sogo
Every model inherits https://doc.qt.io/qt-5/qabstractitemmodel.html#data. The Qt infrastructure (e.g. QTreeView) calls the model's data() method multiple times (behind the scenes), passing in the various roles listed in https://doc.qt.io/qt-5/qt.html#ItemDataRole-enum, to get all the information it wants from the model to display each item as desired. One of the roles it passes in is FontRole. Your override of data() returns a bold font if and only if you want it to be bold. In the code proposed, that is when row == 0 && col == 0, so that item (only) comes out in bold.

[sogo]

What I mean't is we are not giving "role" as argument to call the function "QFileSystemModel::data", how does the program knows if role is equal to Qt::FontRole. Does the QFileSystemModel:data function goes to check through all the Qt::ItemDataRole?

[JonB]

@sogo
Your post has crossed with my latest. Read that and see if you follow now? Yes, behind the scenes it calls your data() many times, with different values for role. You can put in a qDebug() statement, to see how many times it is called, with which row/column and with various values for role.

[sogo]

Hi @JonB
Yea, now I get it. Thanks a lot for clarification

[sierdzio]

@sogo said in Highlighting selected row to be Bold in QTreeView:

What I mean't is we are not giving "role" as argument to call the function "QFileSystemModel::data", how does the program knows if role is equal to Qt::FontRole. Does the QFileSystemModel:data function goes to check through all the Qt::ItemDataRole?

const QModelIndex &index, int role role is there, it's the second argument.

If you call data() manually and skip the role, it defaults to Qt::DisplayRole. But the view (QTreeView and others) will call data() with other roles, too, don't worry. If you want to force it (as you should in case of your double click thingy), emit dataChanged() for the row which should be bold.

[sogo]

@sierdzio said in Highlighting selected row to be Bold in QTreeView:

If you call data() manually and skip the role, it defaults to Qt::DisplayRole.

I'm not sure but whenever I have to call it manually, I have to give Qt::ItemDataRole as arg.. For now this is what I tried in my TreeView.cpp code:

#include "TreeView.h"
#include "ui_TreeView.h"

TreeView::TreeView(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::TreeView)
{
    ui->setupUi(this);
    myModel = new FileSystem;
    connect( ui->treeView, SIGNAL(doubleClicked(const QModelIndex&)), this, SLOT( onClick(const QModelIndex&) ) );
}

TreeView::~TreeView()
{
    delete ui;
}

void TreeView::openFile(const QString& folderPath)

{
myModel->setRootPath(folderPath);
QModelIndex index = myModel->index(folderPath);
myModel->setFilter(QDir::NoDotAndDotDot | QDir::AllDirs);
ui->treeView->setModel(myModel);
ui->treeView->setRootIndex(index);
ui->treeView -> expand(index);
}

void TreeView::onClick(const QModelIndex &index)
{
    myModel->data(index,Qt::DisplayRole);

}

@sierdzio said in Highlighting selected row to be Bold in QTreeView:

will call data() with other roles, too, don't worry. If you want to force it (as you should in case of your double click thingy), emit dataChanged() for the row which should be bold

I also tried tried creating new signal which will emit dataChanged(const QModelIndex&) and emit when double clicked signal:

void TreeView::onClick(const QModelIndex &index)
{
   emit dataChanged(index);
}

I'm not sure how to catch this signal in my FileSystem class so that I can connect it with data function. Another issue is if I change hard code row and columns in FileSystem::data function, it calls it everytime to populate tree view which causes rows and columns to be bold out when directory is loaded. This part.

int row = index.row();
  int col = index.column();
  const bool shouldBeBold = (row && col);
  if (role == Qt::FontRole && shouldBeBold) {

[sierdzio]

You need to change the way you think about the view and the model a bit, I think.

In Qt model-view framework, there is a clear separation: the model is "the boss". The view is just a dumb "output" for data provided by the model.

So for example, do not do this:

void TreeView::onClick(const QModelIndex &index)
{
    myModel->data(index,Qt::DisplayRole);
}

The data has not changed, so calling data() here is pointless! Instead, tell the model which row was clicked and update the data inside of the model. I mean something like:

// view
void TreeView::onClick(const QModelIndex &index)
{
    myModel->rowClicked(index);
}

// model

void FileModel::rowClicked(const QModelIndex &index)
{
  // m_boldRow is some private member variable you add to your model class
  // Probably better to use QPersistentIndex here!
  m_boldRow = index; 
  emit dataChanged(index, index, Qt::FontRole);
}

QVariant FileSystem::data(const QModelIndex &index, int role) const
{
  const bool shouldBeBold = (index == m_boldRow);
  if (role == Qt::FontRole && shouldBeBold) {
    QFont boldFont;
    boldFont.setBold(true);
    return boldFont;
  } else {
    return QFileSystemModel::data(index, role); // This will call the original QFileSystem::data method
  }
}

[sogo]

I see, I was trying something similar next i.e. catching the QModelIndex in FileSystem class in separate function and changing the condition inside the data function but I wasn't sure how to update the model. If I'm not wrong, the emit dataChanged() signal is doing that. Thanks for this, this is working. Closing this thread

[eyllanesc]

@sogo A simple solution is to override the initStyleOption method of QStyledItemDelegate:

class StyledItemDelegate: public QStyledItemDelegate{
public:
    using QStyledItemDelegate::QStyledItemDelegate;
protected:
    void initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const {
        QStyledItemDelegate::initStyleOption(option, index);
        if(option->state & QStyle::State_Selected){
            option->font.setBold(true);
        }     
    }
};