Set background color to a cell of a tableView

giesbert

Hi,

I see one problem in your code:
you calculate highest / lowest value based on the proxy row,but in data ypou comparte to source row.

@
MyProxyModel* proxy = new MyProxyModel;
@

proxy should be a member of MainClass and mainClass should be the parent. so like this:

@
class MainClass : public QDialog
{
Q_OBJECT
...
private:
MyProxyModel* proxy
};
@

@
void MainClass::createReportTable(QStringList stringList)
{
...
printModel= new QSqlRelationalTableModel (this);
...

proxy = new MyProxyModel(this);
proxy->setSourceModel(printModel);
ui->printView->setModel(proxy);
ui->printView->setSelectionMode(QAbstractItemView::SingleSelection);

}
@

where do you call createReportTable????

andre

Yes, but you did not take previous advice. Why is proxy a global variable?

First things first: does the code work so far? Do you get it to compile, and can you set rows to highlight (even if they are not actually the low and the high yet)?

There are different ways to determine what the highest and the lowest values are:

Use your SQL backend to calculate the data for you with a clever query

Determine from inside your proxy model. Upside: nicely encapsulated; Downside: less re-usable

Determine from outside your proxy model.

You seem to have chosen the last option for now. No matter if you choose option 2 or 3, you will need to iterate over the model to find the highest and lowest values, and you need to repeat that each time your model changes (rows added, values changed in the relevant column). You can use the model's signals to trigger that iteration, but beware of ending up in an endless loop (you changing your data, triggering a dataChanged() signal, tiggering a recalculation of the highlight, triggering an update of the data, etc...)

I would not prefer setting row numbers, but setting the actual values to highlight. This makes sure that you can highlight two rows if they share the same lowest or highest value.

poporacer

Well, it compiles ok now, thanks Gerolf and Andre. I call createReportTable from a Signal/Slot in a different dialog. None of the rows are highlighted. I don't see where the information gets passed to the proxy and in debug it never gets there. I think putting the highlightCell code in the proxy model will be a good thing, but I want to figure it out first before I start changing a bunch of the code. Do I need to call the data function in my proxy?

giesbert

Hi poporacer,

this MyProxyModel::data function MUST be const. It's not an option. You created a second function which will never be called, as the const one is called.

andre

That is an easily made mistake, by the way. Always check the signature of the function if you think it doesn't get called.

Then, in the slot in the proxy where you receive the rows to highlight, what you are actually doing is changing data in the model. You need to tell the world about such a change, by emitting the void dataChanged ( const QModelIndex & topLeft, const QModelIndex & bottomRight ) signal (defined in QAbstractItemModel). This way, the connected views know they need to update themselves.

When you just hardcode the rows to highlight (for now), do you get a highlight then?

poporacer

Ok, I changed the const reference. Now I get a row highlighted, but it is not the row with the lowest number.
Gerolf, I am pretty sure this is because of the problem you identified
" I see one problem in your code:
you calculate highest / lowest value based on the proxy row,but in data ypou comparte to source row."
I can't figure out how to use the proxy role in the MainClass or the source Role in the data function.
I did get the following error:
QSortFilterProxyModel: index from wrong model passed to mapToSource
I just got home so I will take a look at these two errors. Does anything stick out to you?
What triggers this proxy to be called?
I think it would be a cleaner method to have the high and low highlighted in the proxy class. How might start this?

giesbert

As you calculate high and low value based on the proxy index, you just should compare to the index without mapping it, like in the below code snippet.

@
QVariant MyProxyModel::data ( const QModelIndex & index, int role ) const
{
if (!index.isValid())
return QVariant();
if ( index.row() == m_highRow && role == Qt::BackgroundRole )
{
return QVariant( Qt::yellow );
}
else
{
return QSortFilterProxyModel::data( index, role );
}
}
@

you never need to call data directly for displaying data, that is done by the views.

please step through your code to check, where the mapToSource throws the problem.

I've also rewritten your sales calculation a bit, just to show a bit some things:
ui->printView->model() ==> proxy

@
void MainClass::highlightCells()
{
float lowSales=FLT_MAX;
float highSales=FLT_MIN;
int rowHigh=0;
int rowLow=0;
int totalRows = 0;
float currentSales;

// this should be done only once! --&gt; move it to the place where you create the proxy
connect(this, SIGNAL(sendRows(int, int)), proxy, SLOT(getRows(int, int))); //to pass the rows to be highlighted to the proxy

//get fastest and slowest sales and save row
int numRows = proxy->rowCount();

for (int r = 0; r < numRows; r++ )
{
    if (ui->printView->isRowHidden(r)) // you hide rows from the view ???
        continue;
        
    currentSales = proxy->index(r,5).data(Qt::DisplayRole).toFloat();
    if (currentSales < lowSales)
    {
        lowSales = currentSales;
        rowLow = r;
    }
    
    if (currentSales > highSales)
    {
        highSales = currentSales;
        rowHigh = r;
    }
}

emit sendRows (rowSlow, rowFast);

}
@

poporacer

THANKS! I think I am starting to understand the model/view/delegate concept (very slightly!!!) I will continue to read about it so I can understand it better. I haven't been real successful in my search to get the answers on my own. I have just a couple of questions that I hope you would be so kind to answer. From the information I have gathered (and your insights) This is how I think this works. The Model is an interface between the data and "attaches" roles (background, foreground, font, etc) to the raw data. This will keep the roles persistent within the model so that any view will display the data appropriately? The view merely displays that data from the model with a few options available to the view (sort, column/row hidden, etc) Any changes to either the model or view will generate a signal to the other item so that they can update their data accordingly. You can have more than one model between the data and view for additional functionality.
In my case the code that we have works like this? (I could be totally off course here) When the Model (in my case the sub-classed QSortFilterProxyModel) is getting the data from the base model (it steps through each item as it is added) and it checks the state of several items (valid Index, current role) then sets the role requested and returns the role variable back the the view so that it could be set appropriately? So with this, you can set any of the roles in ItemDataRole through this method? The index passed to the data function of the QSFPM is the index of the base model? And the MaptoSource function gets the index of the proxymodel? That is why you shouldn't use the model index as a persistent item as it is fluid and can change if any changes to the models or view have been made? (this might help other people to understand the concept as well)

giesbert

[quote author="poporacer" date="1302473664"]THANKS! I think I am starting to understand the model/view/delegate concept (very slightly!!!) I will continue to read about it so I can understand it better. I haven't been real successful in my search to get the answers on my own. I have just a couple of questions that I hope you would be so kind to answer. From the information I have gathered (and your insights) This is how I think this works. The Model is an interface between the data and "attaches" roles (background, foreground, font, etc) to the raw data. This will keep the roles persistent within the model so that any view will display the data appropriately? [/quote]

This is correct.

[quote author="poporacer" date="1302473664"]The view merely displays that data from the model with a few options available to the view (sort, column/row hidden, etc) Any changes to either the model or view will generate a signal to the other item so that they can update their data accordingly.[/quote]

This needs a bit correction:

Data changes in the model will be signaled, so all connected views update themselves.
Data changes done in a view are handled by a delegate which usually calls setData in the model (custommodels and custom delegates might differ here). The model then signals all connected views about the changes.

[quote author="poporacer" date="1302473664"]You can have more than one model between the data and view for additional functionality.[/quote]

I would rephrase this:

A view is connected to one model
A model can be a proxy model to add functionality, filtering etc.
Proxy models may contain models or proxy models, which means it is possible to cascade proxy models.

[quote author="poporacer" date="1302473664"]In my case the code that we have works like this? (I could be totally off course here) When the Model (in my case the sub-classed QSortFilterProxyModel) is getting the data from the base model (it steps through each item as it is added) and it checks the state of several items (valid Index, current role) then sets the role requested and returns the role variable back the the view so that it could be set appropriately? [/quote]

I'm not sure, whether I did not understand what you wrote or you had some misunderstanding. I try to say how it is normally:

The view requests data based on a role and an index. If you have a proxy model, it converts the index to the source index and requests the data in the source model and returns it. In your case, you have some additional data in the proxy model. If the view requests this data, it is directly returned from the proxy model.

With setData it is the same. The view directly writes to your proxy model and the proxy decides, whether the data is needed inside your proxy model (only if you have a derived proxy model) otherwise the index is converted and the source model setData is called.

[quote author="poporacer" date="1302473664"]So with this, you can set any of the roles in ItemDataRole through this method? The index passed to the data function of the QSFPM is the index of the base model?[/quote]

No, this is wrong. The view does not handle the source model indexes. From views point of view, there is only one model. It never checks, whether it is a proxy or not. You always get QSFPM indexes. If you then call the source model from QSFPM you have to call mapToSource yourself.

[quote author="poporacer" date="1302473664"]And the MaptoSource function gets the index of the proxymodel? [/quote]

Yes.

[quote author="poporacer" date="1302473664"]That is why you shouldn't use the model index as a persistent item as it is fluid and can change if any changes to the models or view have been made? (this might help other people to understand the concept as well)[/quote]

Incorrect. You can use QPersistentModelIndex for storing model indexes. The proxy models (and also source models) catch a list of persitant indexes and update them due to changes. A persitant index might become invalid later on, if a QSFPM filters out the element.

Only QPersistentModelIndex may be stored inside your class for later usage.

poporacer

Well, I thought I had it figured out...then I sorted the table and the row that was highlighted in the view was still the same row that was highlighted before the sort. Not the correct row. Is there some signal I should be emitting or somehow capturing the sort routine? I looked at the QSortFilterProxyModel class and I didn't see any slots that would work. I thought the model retained the info for the data roles and the view would signal the changes and update the view. What am I missing?

andre

My guess is, that you are now trying to let your proxy model do both the highlighting and the sorting, right? While that is possible, it complicates things a bit. You are now probably highlighting based on the row number for the requested index your proxy's data method, right? Well, sorting obviously changes the order of the rows, so those row numbers are not going to be valid anymore. You might, instead of triggering your highlight based on the requested row number, trigger it based on the row number of the source model that the row in the proxy model represents. For instance.

However, what I would do, is just keep the proxy doing one thing. Simply don't use the sorting facilities of your proxy model (or better yet, disable them), and use a separate proxy for the sorting and the filtering. So you end up with:

[Source model] -> [Highlight proxy] -> [Sort/filter proxy] -> [View]

Downside is that a highlighted row might be filtered out this way. I guess if you want to filter too, you might even have to go for:

[Source model] -> [Filter proxy] -> [Highlight proxy] -> [Sort proxy] -> [View]

giesbert

Hi,

I would go ab it another way:

[Source model] -> [Filter proxy] -> [Sort proxy] -> [Highlight proxy] -> [View]

if you sort the base model of the highlight model, the row indexes also change. This way it does not. :-)

andre

But the problem with this order is, that the view by default will change the sort property on the model that it is displaying. In this case, that would be the Highlight proxy, while you want it to be the sort proxy. If you are going to have the filter and the sort proxies consecutive, you might as well use a single proxy to do the filtering and the sorting.

If the base model of the highlight proxy changes, it needs to re-query for the correct rows to highlight anyway. It would be the same if the base SQL model would be refreshed, for instance.

ihtzudismqa

Hello,
I want to color a cell on a SqlRelationalTableModel.
The condition is, if the value of the cell is 1, I want it blue otherwise it should be red.
After reading the whole topic, I'm very confused. Could someone please help me out?
For example, how to start etc.
Is it the same way like poporacer did? "Just" inherit from QSortFilterProxyModel ?

Thanks in advice

ZapB

Yes. The same method is applicable. Sub-class QSFPM and set it as a proxy between your source model and the view.

andre

Indeed, same idea, thought the implementation is obviously simpler. It is easier to determine value == 1 than it is to determine value == maximumValue, of course.

poporacer

[quote author="Andre" date="1302589505"]My guess is, that you are now trying to let your proxy model do both the highlighting and the sorting, right? While that is possible, it complicates things a bit. You are now probably highlighting based on the row number for the requested index your proxy's data method, right? [/quote]

I guess that is correct because I am using the proxy model. I don't implement anything else in the proxy except for the highlight part (data function)

[quote author="Andre" date="1302589505"]Well, sorting obviously changes the order of the rows, so those row numbers are not going to be valid anymore. You might, instead of triggering your highlight based on the requested row number, trigger it based on the row number of the source model that the row in the proxy model represents. [/quote]

This seems like a clean method that would probably work. How would I do that?

[quote author="Andre" date="1302589505"] Simply don't use the sorting facilities of your proxy model (or better yet, disable them), and use a separate proxy for the sorting and the filtering. [/quote]

Since I only implement the data function in my proxy, I am not sure how to disable the sorting function in one proxy and implement it in another.

[quote author="Andre" date="1302589505"] So you end up with: [Source model] -> [Highlight proxy] -> [Sort/filter proxy] -> [View] Downside is that a highlighted row might be filtered out this way. I guess if you want to filter too, you might even have to go for: [Source model] -> [Filter proxy] -> [Highlight proxy] -> [Sort proxy] -> [View] [/quote]

So to implement this it would be something like this?
@printModel= new QSqlRelationalTableModel (this);
printModel-> setTable (mTableName); //or should this be called from sortProxy?
printModel->setFilter(mFilterString);//or should this be called from sortProxy?

filterproxy->setSourceModel(printModel);
proxy->setSourceModel(filterProxy);
sortProxy->setSourceModel(proxy);

ui->printView->setModel(sortProxy);

@

If the highlighted row is part of the view, can you identify the row and highlight the correct row via a setData function in the view and then capture the sort routine and then re-iterate through the view and make the appropriate color change? It seems like this is more difficult than it should be just to highlight an identified row. but if that is the way to do it, then I want to learn and understand how.

ihtzudismqa

How can I link the query result which is placed in another class, with the variable(which is neccessary for the evaluating), from derived proxymodel class?

ZapB

Can you explain that a little more fully please or even post some code? I think I understand but I could be off the mark.

Are you saying that you need some result from your query to be known in your prxoy for comparison? If so just add a member variable and a slot that sets it to your proxy and emit a signal from your query object that emits the needed value. Then connect the signal to the slot. In your slot you should also be sure to invalidate() the proxy.

ihtzudismqa

Well,
I have a SqlRelationalTableModel and one column which holds either 1 or 2, shown is the corresponding name. (From Sqlite Database)

Like it's descripted in this thread, I have to inherit from QSortFilterProxyModel and override data().

How do I implement it, that the "real" value behind the cell is going to be evaluated and not the name? Which way could be the best?

It may sound confused, sorry for that. Can you understand my matter?