Insert fill circle into cell of QTableWidget

[juaniyoalm]

Hi,

Is posible insert circle into cell of QTableWidget? I need the size of the circle can be changed dynamically.

[SGaist]

Hi,

Use a custom QStyledItemDelegate and do the drawing yourself in there.

[juaniyoalm]

@SGaist Thank you for your answer.

Sorry but I'm starting to use QT, could you give me an example? How would you insert it in the table?

[SGaist]

See the Star Item Delegate Example.

[juaniyoalm]

There are too many classes to just paint a circle in a cell. There is no other way?

[mrjj]

@juaniyoalm
Well you can also add the circle as an icon to the cell.
If you add blank text, the effect is similar.

However, how big do u need the circle to be ?
It cannot be bigger than the cell height in any case.

Update: this was just to answer if there was alternatives.
However, a delegate is far better for it.

[SGaist]

You need one class: the delegate.

In this example they have two if you take the custom editor that you likely don't need.

[mrjj]

Hi
Adding to SGaist . Its not as bad as it looks.
For a paint circle only delegate, you need very little code.

#include <QStyledItemDelegate>
#include <QPainter>

class CircleDelegate: public QStyledItemDelegate {
 protected:
  void paint(QPainter* painter, const QStyleOptionViewItem& opt, const QModelIndex& index) const {

    // set brush to green if selected else blue ( not needed just for fun)
    if (opt.state & QStyle::State_Selected) {
      painter->setBrush(Qt::green);
    } else {
      painter->setBrush(Qt::blue);
    }

    // paint a circle
    int CircleSize=10;
    painter->drawEllipse(opt.rect.center(), CircleSize, CircleSize);
  }
};

and you set it to the table by
ui->tableWidget->setItemDelegateForColumn(1, new CircleDelegate());
the 1 is the col where u want it

You will need to read over
http://doc.qt.io/qt-5/model-view-programming.html
mostly section Item roles
as to make circle dynamic in size, you can use
a Qt::UserRole and setData.
so the size comes from the model.

[VRonin]

Just a couple of small addition to @mrjj 's code:

• you'll probably also need to reimplement sizeHint() to return a size appropriate to contain the circle.
• blindly modifying the painter argument is risky. You should call painter->save(); before setting the brush and painter->restore(); after you finished the painting

[juaniyoalm]

Thank you, the solution is good for me!!! but I would like that the background of cells is fill too. This colour have to change too.
I thought about inserting a rectangle but I would need the circle to be located on top...

[mrjj]

@juaniyoalm
Hi
Just use other paint methods like
painter->drawRect(opt.rect);

[juaniyoalm]

@mrjj Thank you so much!!

Okay, I have that solved.

Another question is that the size of each circle depends on a value that my mushroom class has. In my class I created a paint method but I do not know how to link that method with the delegate or what is the way to write the method.

[mrjj]

@juaniyoalm
Hi, is the value in the model ?
The delegate can use values from model.
so the color and size of circle could come from model.

[juaniyoalm]

@mrjj

No, that value is in a c++class. I have to create a custom model... It's ok?? Or I can use a default model??

[mrjj]

@juaniyoalm
You can use http://doc.qt.io/qt-5/qstandarditemmodel.html
if it is. dont have to be custom.
I though you already had a model ?
Also is this with a QTableWidget ?
(it uses a model already )

[juaniyoalm]

@mrjj

No, I use QTableView.

I used a model to try but I don't know how to implement it

[mrjj]

@juaniyoalm
Super. With view its much easier.
so you have to construct a model with the data
that comes from the class.
Did you make a qstandarditemmodel before ?

[juaniyoalm]

@mrjj
Yes, I did but without data class

[juaniyoalm]

@mrjj
Do you show me how to make??

[mrjj]

@juaniyoalm
Hi
Please read about userRoles and setData

http://doc.qt.io/qt-5/model-view-programming.html
section Item roles

you can simply put the color / size in user role, or you can have
it directly as an item in your model.
Both ways are fine.
Then delegate read the user role and use the data.