Set background color to a cell of a tableView

[poporacer]

Ok, as I am new to all this, I am not sure how to use a proxy model, derived from QSortFilterProxyModel. Could you give me some code to get me started? I will research this as well, but from reading the docs, I am not sure how to do what you recommend. Thanks

[giesbert]

You could start reading the "docs":http://doc.qt.nokia.com/4.7/model-view-programming.html#proxy-models , they are really good.

[poporacer]

Ok so I re read the docs, and searched, but couldn't get it to work. Here is what I have....where did I go wrong? In setting up the table I use
@QAbstractItemModel myModel;
QSortFilterProxyModel *printModel = new QSortFilterProxyModel(parent);
printModel->setSourceModel(myModel);
ui->printView->setModel(printModel);@
and I get an error: cannot declare variable 'myModel' to be of abstract type 'QAbstractItemModel' because the following virtual functions are pure within 'QAbstractItemModel': virtual QModelIndex QAbstractItemModel::index(int, int, const QModelIndex&) const .(and many more)
I think I have to add something else...how and what do I need to do? I copied the code almost exactly.

[giesbert]

It tells you what is wrong, QAbstractItemModel is not creatable. It is the abstract base class of all Models, and it is ABSTRACT. you normally go this way:

@
printModel= new QSqlRelationalTableModel (this);
printModel-> setEditStrategy(QSqlTableModel::OnRowChange);
printModel-> setTable (mTableName);

printModel-> setRelation (2, QSqlRelation("customer", "id", "Name"));
printModel->select();

MyQSFPM* proxy = new MyQSFPM(this);
proxy->setSourceModel(printModel);
ui->printView->setModel(proxy);
@

now you have to create MyQSFPM as derived class of QSortFilterProxyModel abd reimplement data.

@
class MyQSFPM : public QSortFilterProxyModel
{
...
}
@

[poporacer]

I feel stupid. I have read several docs and searched and still do not understand how to reimplement the data in the derived class. Do I simply copy the implementation of the functions I need to use and put them in the derived class? I am going to continue reading and trying things. Sorry for not understanding.

[giesbert]

Hi poporacer.

Overwriting methods is standard C++ knowledge.
For more information about model / view, look here:

"Qt documentation - Model/View Programming":http://doc.qt.nokia.com/4.7/model-view-programming.html

[andre]

[quote author="poporacer" date="1301546336"]I feel stupid. I have read several docs and searched and still do not understand how to reimplement the data in the derived class. Do I simply copy the implementation of the functions I need to use and put them in the derived class? I am going to continue reading and trying things. Sorry for not understanding.[/quote]

As Gerolf points out, overriding virtual methods is a key feature of object oriented programming in C++. It is an essential part of subclassing.

What you need to do in this case, is to handle the cases you want to handle in your reimplementation of data() in your subclass, and use the base implementation for all other cases. Note that it is often a good idea to call the base class implementation of an overridden method in the reimplementation.

In your case, your data method might look something like this*:

@
QVariant myProxyModel::data ( const QModelIndex & index, int role ) const
{
if (!index.isValid())
return QVariant();

QModelIndex sourceIndex = mapToSource( index );
if ( role == Qt::BackgroundRole ) {
if (sourceIndex.data( Qt::DisplayRole ).toDouble == m_theValueIWant ) {
return Qt::red;
} else {
return QVariant();
}
} else {
return sourceIndex.data( role );
}
}
@

Perhaps that can help you get started.

*) That means: typed in the forum editor, don't expect this to compile or be complete

Edit: changed sample to return a color, not a checkbox state. I was confused with another question

[ZapB]

[quote author="Andre" date="1301558057"]
In your case, your data method might look something like this*:
[/quote]

I think you got two threads mixed up, this one is about the background role ;-)

So in this case you reimplementation may look something like:

@
QVariant myProxyModel::data ( const QModelIndex & index, int role ) const
{
if (!index.isValid())
return QVariant();

if ( sourceIndex.row() == m_maxRow && role == Qt::BackgroundRole ) {
QModelIndex sourceIndex = mapToSource( index );
return QVariant( Qt::red );
} else {
return QSortFilterProxyModel::data( index, role );
}
}
@

where m_maxRow is a member variable that you need to set.

[andre]

[quote author="ZapB" date="1301558444"][quote author="Andre" date="1301558057"]
In your case, your data method might look something like this*:
[/quote]

I think you got two threads mixed up, this one is about the background role ;-)
[/quote]

Yeah, that's what I just realized. There is another running question on putting checkboxes from an SQL model in a QTableView, and I confused the two. I was already editing my response.

[ZapB]

Yeah, I thought so. I'm following that thread too. Easily done ;-)

[poporacer]

I have read the code, read the docs you suggested and yet have not been able to get it to work. I am not sure if I am reading too much into this. So let me explain what I understand that I shoul do so far. I need to create a new class (MyProxyModel) and inherit QSortFilterProxyModel. Then in my class reimplement the data function ( I think that in ZapB's code the declaration
@QModelIndex sourceIndex = mapToSource( index ); @
should go at the top of the function?) I am not sure what is meant by having to set m_maxRow is this to the total number of rows or the row number that I want to set the background color? Then in my main class I set up the table following Gerolf's suggestion. Here is what I have:
myproxymodel.h
@
#ifndef MYPROXYMODEL_H
#define MYPROXYMODEL_H

#include <QSortFilterProxyModel>

class MyProxyModel : QSortFilterProxyModel
{
Q_OBJECT

public:
MyProxyModel();
~MyProxyModel();
QVariant data ( const QModelIndex & index, int role );
void setSourceModel ( QAbstractItemModel * sourceModel );

};
#endif //MYPROXYMODEL_H@

myproxymmodel.cpp:
@
#include "myproxymodel.h"

MyProxyModel::MyProxyModel (QObject *parent) :
QSortFilterProxyModel(parent)
{

}

QVariant MyProxyModel::data ( const QModelIndex & index, int role ) const
{
QModelIndex sourceIndex = mapToSource( index );
if (!index.isValid())
return QVariant();
if ( sourceIndex.row() == m_maxRow && role == Qt::BackgroundRole )
{

return QVariant( Qt::red ); 
} 
else 
{ 
return QSortFilterProxyModel::data( index, role ); 
} 

}@
And in my main class I have
@#include "myproxymodel.h"
.
.
.
void MainClass::createReportTable(QStringList stringList)
{
printModel= new QSqlRelationalTableModel (this);
printModel-> setEditStrategy(QSqlTableModel::OnRowChange);
printModel-> setTable (mTableName);
printModel-> setRelation (2, QSqlRelation("customer", "id", "Name"));
printModel->select();
MyProxyModel* proxy = new MyProxyModel(this);
proxy->setSourceModel(printModel);
ui->printView->setModel(proxy);
@

I get several compile errors and I have tried to figure out why, but can't figure it out.
Line 12 in the main class gives me the error
no matching function for call to 'MyProxyModel::MyProxyModel(MainClass* const)

Line 14 in the main class gives me the error
'QAbstractItemModel' is an inaccessible base of 'MyProxyModel'

Am I going about this correctly? I am trying to figure it out on my own by "reading the docs" but the docs I have trouble understanding. Where am I going wrong?

In reading, I see this function:
bool QAbstractItemModel::setData ( const QModelIndex & index, const QVariant & value, int role = Qt::EditRole ) [virtual] Is this of any use?

[andre]

In your myproxymodel.h code, you declare setSourceModel on line 14. You don't need that; QSortFilterProxyModel already has a good implementation of that method. You can reimplement it if you want to do something special when the source model is set, but it doesn't seem to be the case.

m_maxRow is supposed to indicate the row you want to highlight. Of course, this is only one way to do that; you can also invent something more flexible that allows you to highlight different rows with different colors.

Note that you need to publicly inherit from QSortFilterProxyModel. That is: change the first line of your myproxymodel.h to:

@
class MyProxyModel : public QSortFilterProxyModel
@

That should get rid of your error on line 14 of your main: ‘QAbstractItemModel’ is an inaccessible base of ‘MyProxyModel’. Remember, C++ uses private as the default, not public.

bool QAbstractItemModel::setData is used to modify data through the QAbstractItemModel interface, so, mostly through the views themselves. In your case, you don't need to reimplement this method. You do, of course, need to have some other method to determine or set the row number to highlight.

[giesbert]

Hi,

there is one more bug in your code. This error:

bq. no matching function for call to ‘MyProxyModel::MyProxyModel(MainClass* const)

is issued due to this code:

@
class MyProxyModel : QSortFilterProxyModel
{
Q_OBJECT
public:
MyProxyModel(); // <-- !!!
};
@

It should be like this;

@
class MyProxyModel : QSortFilterProxyModel
{
Q_OBJECT
public:
MyProxyModel(QObject* parent); // <-- !!!
};
@

[poporacer]

Thanks for your help. What would be the best way to pass the m_maxRow variable to the MyProxyModel class? The two options I can think are, create a global variable (usually considered bad) or create a signal/slot to pass the variable? I tried to pass it via a signal/slot and my class declaration is not working correctly. In my mainclass.h I have:
@#include "myproxymodel.h"
class MyProxyModel;@

in my mainclass.cpp I have:
@void MainClass::colorCells()
{
float lowSales=99999999;
float highSales=0;
int rowLow=0;
int rowHigh=0;
int totalRows = 0;

MyProxyModel myProxyModel; //error here

connect(this,SIGNAL(sendRows(int, int)),
&myProxyModel, SLOT(getRows(int, int))); //to pass the high and low sales

int numRows =ui->printView->model()->rowCount();

for (int r=0; r<numRows; r++ )
{
if (ui->printView->isRowHidden(r))
continue;
float currentSales = ui->printView->model()->index(r,32).data(Qt::DisplayRole).toFloat();
if (currentSales <lowSales)
{
lowSales = currentRunTime;
rowLow = r;
}
if (currentSales > highSales)
{
highSales = currentSales;
rowhigh = r;
}
totalRows++;
totalTime += currentRunTime;
}

emit sendRows (rowSlow, rowFast);
QModelIndex modelIdx = printModel->index(rowFast,32, QModelIndex());
printModel->data(modelIdx, Qt::BackgroundRole);//Is this correct implementation?
@
where I try to declare the MyProxyModel variable I get the error:
no matching function for call to 'MyProxyModel::MyProxyModel()'
candidates are: MyProxyModel::MyProxyModel(QObject*)
MyProxyModel::MyProxyModel(const MyProxyModel&)
I don't see why it thinks I am trying to declare a function.
I keep reading, trying to keep from asking questions here but I keep coming back!
Again, I appreciate your patience with my questions.

[andre]

Don't create your proxy model on the stack, create it on the heap with a proper parent. Otherwise, it will be deleted as soon as the method finishes (so before a result is even drawn). What's more, the code as you wrote it now can only be run once. Otherwise, you'll keep creating more proxy models. That can't be what you want. You also don't set the proxy model as the model for your view, nor do you give the proxy model a source model.

I think, you should calculate the row to highlight in the proxy model itself. That nicely encapsulates the functionality you're after in a single class. Or, make a more flexible API on the proxy model to add highlights to selected rows at will, so you can re-use it later on. Your mid-way solution doesn't look very nice to me. Also: what happens if two rows share the same maximum or minimum value?

I don't quite get your implementation. Especially the last two lines are quite mystifying. Why to you request data from your model, and then don't use it? Also, I would not initialize to 0 and 99999999. Those are rather arbitrairy. Instead, initialize to the maximum and minimum values of float. You can find those by including <float.h>.

First, however, try to get the proxy model working with a fixed (set of) row(s) of to highlight. If that works ok, take the next step and determine the rows dymanically. I would do that by responding to changes in the (source) model, so you can update the source model and be sure that the highlights will be properly updated as well.

[poporacer]

Ok I created
@MyProxyModel* proxy = new MyProxyModel;@
And put it before the constructor as it looks like I need it in more than one spot. I still get the error:
no matching function for call to 'MyProxyModel::MyProxyModel()'
candidates are: MyProxyModel::MyProxyModel(QObject*)
MyProxyModel::MyProxyModel(const MyProxyModel&)

In my MainClass I have a function that creates the table and there I set the model. I use:
@void MainClass::createReportTable(QStringList stringList)
{
mReportOptions=stringList;

printModel= new QSqlRelationalTableModel (this);
printModel-> setEditStrategy(QSqlTableModel::OnRowChange);
printModel-> setTable (mTableName);
printModel-> setRelation (2, QSqlRelation("customer", "id", "Name"));
printModel->select();
proxy->setSourceModel(printModel);
ui->printView->setModel(proxy);

@
So my implementation is wrong? How do I properly call the function to color the row?
The table will be getting rows added or deleted. After each change, I iterate through the table to get the high and low sales. This will identify the row to color. The table will need to be continually updated. It will only highlight the highest and lowest row. Am I close or am I in right field?

[andre]

The error on the first line of code you show, is quite clear. You have no constructor for MyProxyModel without arguments. So, I suggest you add an argument to your heap allocation of MyProxyModel. Just put the constructor of your proxy model in the same piece of code as the one you show below, and create a pointer member variable in your class declaration just like you have for printModel.

How you properly call the method to color the rows, depends on how you implemented it. Could you tell us what route you choose?

[poporacer]

Here is what I have/need. I have a QSqlRelationalTableModel that will display a table. Some of the columns will be hidden based on criteria selected by the user. The highest sales will be highlighted in yellow and the lowest sales highlighted in red. Rows will be added and removed. After each change to the table, the table needs to be evaluated and the appropriate cells or rows highlighted.
[quote author="Andre" date="1302069303"]
How you properly call the method to color the rows, depends on how you implemented it. Could you tell us what route you choose?[/quote]
I was following the advice here on how to implement it. I think I have posted all the relevant code in the past posts. But to make it easier to read I will re-post in this post.
myproxymodel.h
@#ifndef MYPROXYMODEL_H
#define MYPROXYMODEL_H

#include <QSortFilterProxyModel>

class MyProxyModel : public QSortFilterProxyModel
{
Q_OBJECT

public:
MyProxyModel(QObject* parent);
~MyProxyModel();
QVariant data ( const QModelIndex & index, int role );

private:
int m_lowRow; //to store the row number of the lowest row
int m_highRow; //to store the row number of the highest row

signals:

private slots:
void getRows(int, int); // to get the row numbers that need to be highlighted

};

#endif //MYPROXYMODEL_H@

myproxymodel.cpp
@#include "myproxymodel.h"

MyProxyModel::MyProxyModel (QObject *parent) :
QSortFilterProxyModel(parent)
{

}

QVariant MyProxyModel::data ( const QModelIndex & index, int role ) //const ** I had to remove this because of a compiler error
{
QModelIndex sourceIndex = mapToSource( index );
if (!index.isValid())
return QVariant();
if ( sourceIndex.row() == m_highRow && role == Qt::BackgroundRole )
{

return QVariant( Qt::yellow );
} 
else 
{ 
return QSortFilterProxyModel::data( index, role ); 
} 

}
void MyProxyModel::getRows( int rowLow,int rowHigh)
{
m_highRow=rowHigh;
m_lowRow=rowLow;
}
@
mainclass.h
@#ifndef MAINCLASS_H
#define MAINCLASS_H

#include <QDialog>
#include <QSqlRelationalTableModel>
#include<QSortFilterProxyModel>
#include "myproxymodel.h"

class MyProxyModel;

namespace Ui {
class MainClass;
}

class MainClass : public QDialog
{
Q_OBJECT

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

private:
Ui::MainClass *ui;
QString mTableName;
QString mFilterString;
QStringList mReportOptions;
void highlightCells();
QSqlRelationalTableModel *printModel;

signals:
void sendRows(int, int);

private slots:
void on_btnPrint_clicked();
void on_pushButton_2_clicked();
void createReportTable(QStringList);
void getTableName(QString);
void getFilterData(QString);

};

#endif // MAINCLASS_H
@

mainclass.cpp
@#include "mainclass.h"
#include "ui_mainclass.h"
#include <QtSql>
#include <QSqlRecord>
#include "myproxymodel.h"
#include <float.h>

MyProxyModel* proxy = new MyProxyModel;

MainClass::MainClass(QWidget *parent) :
QDialog(parent),
ui(new Ui::MainClass)
{
ui->setupUi(this);
mNumTables=0;

}

MainClass::~MainClass()
{
delete ui;
delete proxy;
}

//get table name from user selection

void MainClass::getTableName(QString tString)
{
mTableName=tString;
}

//get user filter string

void MainClass::getFilterData(QString fString)
{
mFilterString=fString;
}

//Create report table based on user info stringList holds criteria

void MainClass::createReportTable(QStringList stringList)
{
mReportOptions=stringList;

printModel= new QSqlRelationalTableModel (this);
printModel-> setEditStrategy(QSqlTableModel::OnRowChange);
printModel-> setTable (mTableName);
printModel-> setRelation (2, QSqlRelation("rider", "id", "LName"));
printModel-> setRelation (3, QSqlRelation("track", "id", "TrackName"));
printModel-> setRelation (4, QSqlRelation("bike", "id", "BikeName"));

proxy->setSourceModel(printModel);
ui->printView->setModel(proxy);
ui->printView->setSelectionMode(QAbstractItemView::SingleSelection);
ui->printView->setSelectionBehavior(QAbstractItemView::SelectRows);
ui->printView->setColumnHidden(0,true);//id
    

printModel->select();
//routine here to hide additional columns based on user selection

printModel->setFilter(mFilterString);
ui->printView->setSortingEnabled(true);
ui->printView->resizeColumnsToContents () ;
ui->printView->horizontalHeader()->setStretchLastSection(true);
highlightCells();
printModel->select();

}

//here we should iterate the table to get the rows that need to be highlighted

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

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 =ui->printView->model()->rowCount();

for (int r=0; r<numRows; r++ )
{
if (ui->printView->isRowHidden(r))
continue;
currentSales= ui->printView->model()->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);

//here is where I need to call proxy to highlight the appropriate cell or column

}@

Did this clear things up? Where do I go from here?

[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.