How to simply change the background colour of a cell inside a TableView

[G4bandit]

I need to change the coulor of some certain cell dependent on value "0" or "1" to the colours "red" or "green" how can I do this?

[VRonin]

What model are you using?

P.S.
Just for future reference, once QTBUG-63766 is solved (and I'm planning to work on it during the xmas period) the solution with QStandardItemModel is trivial

[G4bandit]

@VRonin said in How to simply change the background colour of a cell inside a TableView:

once QTBUG-63766 is solved

Can I help you with solving the issue? Although I do not have any clue :D

Mainly I work with QSqlTableModel or QSqlQueryModel it depends. But in this case QSqlQueryModel makes more sense.

[VRonin]

1. Add this proxy between your model and your view
2. create a slot

Q_SLOT void updateBackground(const QModelIndex& srcTopLeft, const QModelIndex& srcBottomRight){
if(!srcTopLeft.isValid() || !srcBottomRight.isValid())
return;
if(srcTopLeft.parent().isValid() || srcBottomRight.parent().isValid())
return;
for(int rowIter = srcTopLeft.row();rowIter !=srcBottomRight.row();++rowIter){
for(int colIter = srcTopLeft.column();colIter !=srcBottomRight.column();++colIter ){
const QVariant currIdxData = model->index(rowIter,colIter).data(Qt::DisplayRole);
if(!currIdxData .isValid()){
proxyModel->setData(proxyModel->index(rowIter,colIter),QVariant(),Qt::BackgroundRole);
continue;
}
if(!currIdxData.canConvert(QMetaType::Int)){
proxyModel->setData(proxyModel->index(rowIter,colIter),QVariant(),Qt::BackgroundRole);
continue;
}
switch(currIdxData.toInt()){
case 1:
proxyModel->setData(proxyModel->index(rowIter,colIter),QBrush(Qt::green),Qt::BackgroundRole);
break;
case 0:
proxyModel->setData(proxyModel->index(rowIter,colIter),QBrush(Qt::red),Qt::BackgroundRole);
break;
default:
proxyModel->setData(proxyModel->index(rowIter,colIter),QVariant(),Qt::BackgroundRole);
}
}
}
}

3. connect the dataChanged signal from your original model to the newly created slot
4. optional: if you are working with an editable QSqlTableModel you probably want to change line 29 of the proxy to:
   if(role == Qt::EditRole || index.parent().isValid()) return QIdentityProxyModel::setData(index,value,role);

Notes

• The above applies only to flat models (no trees)
• This will apply the colour to all columns, it's easy to change the slot to ignore columns you don't want to consider

[G4bandit]

@VRonin

Hi,

first thks so far for your expanded code example.

I am trying to understand with small steps so I wrote this code and hoped see something inside the QTableView. But unfortunatelly nothing happens.

   QSortFilterProxyModel* proxyModel = new QSortFilterProxyModel(this);
   proxyModel->setSourceModel(TblModel);

      TblModel->setData(proxyModel->index(0,0),QBrush(Qt::red),Qt::BackgroundRole);

TblModel is a QSqlTableModel Object which I generate dircetly inside the constructor.

[VRonin]

@G4bandit said in How to simply change the background colour of a cell inside a TableView:

TblModel is a QTableModel

• There's no such thing as QTableModel in Qt, you have to be a little more specific. If you are talking about QSqlTableModel then the problem is here. It will reject everything other than Qt::EditRole. That's the reason I suggested using ExtraRolesProxyModel in between
• Are you setting the model on the view? view->setModel(proxyModel);

P.S.
It's not a bad idea to wrap setData, insert*, remove* and move* calls in a Q_ASSUME to make sure they actually did what you think they should do

[G4bandit]

@VRonin said in How to simply change the background colour of a cell inside a TableView:

Are you setting the model on the view? view->setModel(proxyModel);

I have changed the code to this:

   QSortFilterProxyModel* proxyModel = new QSortFilterProxyModel(this);
   proxyModel->setSourceModel(TblModel);
   ui->TV_DBOut->setModel(proxyModel);

      TblModel->setData(proxyModel->index(0,0),QBrush(Qt::red),Qt::BackgroundRole);

But I guess strongly that it is not what you have meant or at all that it is more complex.

Like you said in your post before:

1. Add this proxy between your model and your view
   I can not follow you, - I am a bloody newbie.

[VRonin]

The main question is: what type is TblModel?

[G4bandit]

@VRonin said in How to simply change the background colour of a cell inside a TableView:

The main question is: what type is TblModel?

Sry, yes it is of QSqlTableModel.

[VRonin]

Then TblModel->setData will return false for every role except Qt::EditRole so basically TblModel->setData(proxyModel->index(0,0),QBrush(Qt::red),Qt::BackgroundRole); will do absolutely nothing.

You need something that handles the other roles that QSqlTableModel ignores. Enter https://pastebin.com/gmNCuUFk

[G4bandit]

@VRonin

I agree with you TblModel->setData returns false.

But my main issue still that I am not able to combine all your information/hints/code parts to one working unit.

1:
I have created a header file with the content of "https://pastebin.com/gmNCuUFk"
Do not know what to do with it.

2:
and I also tried to run your code posted on
VRonin 15. Dez. 2017, 10:31

3:
And this point
VRonin: 1.Add this proxy between your model and your view
Do not know how to

[VRonin]

@G4bandit said in How to simply change the background colour of a cell inside a TableView:

Do not know how to

It's the same as

QSortFilterProxyModel* proxyModel = new QSortFilterProxyModel(this);
   proxyModel->setSourceModel(TblModel);
   ui->TV_DBOut->setModel(proxyModel);

but instead of QSortFilterProxyModel use ExtraRolesProxyModel

[G4bandit]

I got it!!!

SUCESS :D

Thanks a lot

[G4bandit]

If someone ask how to change the color of headers,- here is a helpful link:

https://stackoverflow.com/questions/32147213/how-to-change-the-background-color-from-the-headerhorizontal-vertical-qtable#32147945

tview->model()->setHeaderData(0,Qt::Horizontal,QBrush(QColor("red")),Qt::BackgroundRole);
tview->show();

QApplication::setStyle(QStyleFactory::create("Fusion"));

The last line was on my PC (Win) necessary to get the effect.

[paul_espinosa]

@G4banditi need to do somo simililar can help me please , i cant understand

[VRonin]

I now implemented a generic proxy for this, I called it Role Mask Proxy Model. I have an example that changes the background, it uses QStringListModel but it's exactly the same with other base models

[paul_espinosa]

@VRonin so mucth thanks , wonderfull library, i can do

[paul_espinosa]

if i use a QSqlRelationalTableModel, Role Mask Proxy Model works????

[VRonin]

Yes, works on any model

[paul_espinosa]

@VRonin thanks for your help, now i have a problem, i can not save the data of my QSqlTableModel , i used the example exem_rolemaskeditablesql.cpp i can edit the data but i can not save,