suggestions for repeating display views

SGaist

Hi,

The most minimal I can think of a QListView and a QLabel for displaying the information.

Can you give more details about your setup ?

JonB

@mzimmers
You could, but it doesn't sound like it scales, what if there were 10,000 of these devices? Eventually there's a memory price to pay.

But are you going to create a separate widget for each device? Won't the displays be similar? So you'll want to write code which lets user pick which device and then show a "shared" widget for the information?

mzimmers

More information: the main window will contain a list/table of active devices on the network. Some very summary information (MAC address, device ID, last communication time) will appear in this table. When the user wants to get more information or to configure a particular device, he'll select it from this list.

At this point, the display will change to a details view. There will be more information and several controls, but everything will pertain to just one device. JonB's point is valid about this probably using resources unnecessarily.

I'll have to store a fair amount of data (some time period for each device) but I guess there's no reason the details UI needs to be replicated.

SGaist: the list/label will be fine for the overview display (I'll use a table instead of a view), but I'll need another display for the details view.

SGaist

Keep all your device information in a model so you can easily and quickly get them.

Then when your user selects a device, Load the corresponding data from your model and show it in the QLabel.

mzimmers

I'm not sure I understand what you're recommending -- are you proposing that I use a single QLabel object for the entirety of my details display?

SGaist

If you are only showing one device details at a time, yes. Just update the content of the label with what corresponds to the selected device.

mzimmers

The details view as I intend it will contain quite a bit of information. There will be ~10-15 fields, all of which can be modified by the user. There will also be a few push buttons to send other commands to the target device.

SGaist

Makes me thinking about the QtSQL module Book example.

mzimmers

Thanks for the reference. I've taken some of that example and adapted it.

So, to summarize, I have a QTableView that is associated with a QAbstractItemModel. The table reveals a few details about all the devices (rows) found. Now I'd like to display some additional detail about any device that the user selects.

A very simple start would be to display the MAC address in a QLineEdit when the user selects a row. I can envision a way to do this, but it's cumbersome and indirect (signalling the model to extract the information and signal it back to the widget). Can someone inform me of a preferred method to do this?

Thanks...

JonB

@mzimmers

but it's cumbersome and indirect (signalling the model to extract the information and signal it back to the widget)

Why? What do you have in mind by "indirect" & "signalling"? You haven't mentioned threads anywhere, so assuming your UI, view & model are all in the same thread where is there any "signalling" involved (unless you mean the row selected signal, but that does not matter)?

You just retrieve the data via QAbstractItemModel::data() and plonk it into your widget(s), explicitly.

Depending, you can already have retrieved the "additional detail" into your model without having to display it in the QTableView, so you can access it without having to do work at that instant if you prefer (perhaps not relevant for your device-model, but often the case when it's a database-model).

kshegunov

Well, I'd just fill the model data as it comes. And it'd come as the selection of the selection model changes ... I think just subscribing to the QItemSelectionModel::selectionChanged signal should be enough, no?

mzimmers

Here's what I'm trying to do in my display:

// in my c'tor.
    QObject::connect(ui->tableView->selectionModel(), QItemSelectionModel::currentRowChanged, this, &Widget::updateDetails);
}

void Widget::updateDetails(QModelIndex i)
{
    int row = i.row();
    QVariant qv;
    QString s;
    QModelIndex qmi;
    qmi = m_model->getModel()->index(row, DEV_MACADDR, QModelIndex());
    qv = m_model->getModel()->data(qmi, DEV_MACADDR);
    s = qv.toString();
    ui->macAddr->setText(s);

    qmi = m_model->getModel()->index(row, DEV_DEVNAME, QModelIndex());
    qv = m_model->getModel()->data(qmi, DEV_DEVNAME);
    s = qv.toString();
    ui->devName->setText(s);

    qmi = m_model->getModel()->index(row, DEV_LATEST_HB, QModelIndex());
    qv = m_model->getModel()->data(qmi, DEV_LATEST_HB);
    s = qv.toString();
    ui->heartbeat->setText(s);

I'm sure this isn't the best way to do this (particularly since it doesn't work), but in any event, the first assignment of qv works, but the others give qv an invalid value. What am I doing wrong?

EDIT: OK, I just realized I shouldn't be using the 2nd argument to the data() call. It's working now. Not ready to mark this solved yet, though, as I'm going to have other questions in a bit.

Thanks...

mzimmers

So far, I've been experimenting entirely with QStrings as elements in my model, like this:

struct DeviceDetails
{
    uint8_t macAddr[6];
    char devName[25];
...
} d;
QAbstractItemModel *m_model;
...   
 m_model->setData(m_model->index(row, DEV_DEVNAME), d.devName); /

I'm now trying to work with other data types, such as the macAddr, but I can't figure out how to do this. This is what I'm trying to do (but doesn't compile):

    m_model->setData(m_model->index(row, DEV_MACADDR), d.macAddr);

How do I do this? Thanks...

kshegunov

@mzimmers said in suggestions for repeating display views:

but doesn't compile

With what error?
I could imagine QVariant isn't aware of how to serialize that type, but that's just a speculation at this point.

mzimmers

C:\Qt\5.10.1\mingw53_32\include\QtCore\qvariant.h:471: error: 'QVariant::QVariant(void*)' is private
     inline QVariant(void *) Q_DECL_EQ_DELETE;
            ^

and:

C:\Users\MZimmers\CD desktop apps\Qt projects\wb_utility\model.cpp:36: error: use of deleted function 'QVariant::QVariant(void*)'

kshegunov

Well, I suggest you convert d.macAddr to QString before you pass it to setData ...

mzimmers

This post is deleted!

VRonin

@mzimmers said in suggestions for repeating display views:

'QVariant::QVariant(void*)' is private

That is a "safeguard" operator to avoid people using pointers to non-QObjects into a QVariant.
Basically macAddr is of type unsigned char* the d will still own the data into d.macAddr and will delete it when it goes out of scope. QVariant needs to own the data and know how to delete it. you should be able to hack your way around it by using a smart pointer but it's probably much easier to store it in a Qt container like QByteArray
m_model->setData(m_model->index(row, DEV_MACADDR), QByteArray(d.macAddr,sizeof(d.macAddr));

P.S.
If the compiler complains about signed/unsigned you can use:
QByteArray(static_cast<char*>(d.macAddr),sizeof(d.macAddr))

mzimmers

@VRonin ah that explains it (in fact, that's exactly what I was trying to do).

I like your idea of changing my char array into QByteArray, but there's a snag - I'm attempting to use the same C struct for my target device as my host app, which restricts me to C++11 types.

JonB

@mzimmers
But @VRonin is only asking you to make a copy into a QByteArray for passing to m_model->setData(); you're not changing what is actually in your struct d. So how does that affect your use of the struct in the two apps?