How to refresh QComboBox?

[TomNow99]

Hi,

I have QComboBox ( subclass of QComboBox, but it is really standard QComboBox ) and QTimer with interval = 1 sec. When is timeout in QTimer I add to QComboBox new Item like this:

addItem("randomText");

When the QCombobox's popup is visible and I add new Item in that moment I see that item in comboBox, but I can select it only using scrollBar. Of course when I hide popup and show it everything is ok. Picture:

1. popup was shown when timer add new Item. I see that there are new items, but I can select it only using scrollBar ( there is on the right )

2. here I hide popup ans show it - here I see many items and don't need use scrollbar to select one item.

I tried change timer slot to:

    addItem("randomText");
    showPopup();

It refresh popup, but when I have hide popup I will have visible popup.

So I tried something like ( timer slot ):

    addItem("randomText");
    if(view()->isVisible())
    {
        showPopup();
    }

And here I find two other problems:

1. Sometimes when I have visible popup and change focus on other app ( for example qt creator ) I still see popup ( only popup - no app, no comboBox ). Picture:
   

on the background is my code in QtCreator and in the foreground there is that popup.

2. Sometimes when I click many times on arrow in QComboBox I still see that ScrollBar ( and I don't talk about maxVisibleItems problem ).

Is there better way to showPopup()?

EDIT:
My whole code:

#include "mycombobox.h"
#include <QTimer>
#include <QAbstractItemView>

myComboBox::myComboBox(QWidget *parent): QComboBox(parent)
{
    QTimer *timer = new QTimer;
    connect(timer, &QTimer::timeout, this, &myComboBox::timeoutSlot);
    timer->start(1000);
    setMaxVisibleItems(40);
}

void myComboBox::timeoutSlot()
{
    addItem("randomText");
    if(view()->isVisible())
    {
        showPopup();
    }
}

[Pl45m4]

@TomNow99

Try update or repaint.

[TomNow99]

@Pl45m4 Thank you for answer. I tried, but with not result.

[Pl45m4]

@TomNow99

What if you update the QAbstrctItemView only?

comboBox->view()->update();

What you can also do is looking at Qt source code to see what happens in showPopup (how your popup view is created).

[TomNow99]

@Pl45m4 I tried many things:
view(), view()->viewport(), this: update / repaint in many combinations. And no good result...

EDIT:
I find the same problem here:

https://forum.qt.io/topic/99940/dynamically-fit-qcombobox-popup-height-to-the-dynamically-changing-count-of-items/9

And... with no solution

[Pl45m4]

@TomNow99

Yeah, that's what I also thought ( @J-Hilk 's answer). You have to re-create the popup widget / the view, because as long as it stays open, the comboBox knows, that there are new items, but the view will keep its old size. So the scrollbar appears.

[TomNow99]

@Pl45m4 Do you know any way to check if view() is in state like this:

?

When I check isVisible() I always get true.

[mrjj]

@TomNow99
so
combobox->view()->isVisible()
always returns true ?

[Pl45m4]

@TomNow99 said in How to refresh QComboBox?:

check if view() is in state like this

What state? You mean fully expanded (no scrollbar)?

comboBox->view()->verticalScrollBar()->isVisible()

[TomNow99]

@mrjj @Pl45m4
My plan:

After add new item to comboBox I have to use showPopup() method. But when I have only this one function in my timer slot, popup will be shown when popup is hidden and when is visible. I don't want situation that I click somewhere in button to add new item to comboBox, this comboBox will be hidden and poof... now is visible :D

So I have to check state - view()->isVisible.

And now is ok. When I add new Item and popup is hidden - it will be hidden. When I add new item and popup is visible - I add new item and popup will be visible. Perfect.

But I have 2 other problems:

1. Sometimes when I click many times on arrow in QComboBox I still see that ScrollBar ( and I don't talk about maxVisibleItems problem ). I solve ( I think I solve ) problem override paint() function and in this function I check visibility of verticalScrollBar. When it is visible = showPopup().

2. Sometimes when I have visible popup and change focus on other app ( for example qt creator ) I still see popup ( only popup - no app, no comboBox ) - picture to this situation is above in 2 places.

I think when I click on other app (in this example qtCreator ) ) to hide popup, in my timer slot at the same moment I check visible of popup. It is in state "now I'm in process 'during hide popup' ". So popup is hide in 50%, but the state is still visible :D And popup is shown without my app. So my condition

view()->isVisible() ?

is not good.

EDIT:

My code is something like ( maybe be wrong, because I'm in other computer, so please treat this code like pseudocode ):

#include "mycombobox.h"
#include <QTimer>
#include <QAbstractItemView>
#include <QScrollBar>  

myComboBox::myComboBox(QWidget *parent): QComboBox(parent)
{
    QTimer *timer = new QTimer;
    connect(timer, &QTimer::timeout, this, &myComboBox::timeoutSlot);
    timer->start(1000);
    setMaxVisibleItems(40);
}

void myComboBox::timeoutSlot()
{
    addItem("randomText");
    if(view()->isVisible())
    {
        showPopup();
    }
}

void myComboBox::paint(QPaintEvent *ev)
{
     QComboBox::paint(ev);
     if(view()->verticalScrollBar()->isVisible())
     {
            showPopup();
     }
}

[Christian Ehrlicher]

@TomNow99 said in How to refresh QComboBox?:

When the QCombobox's popup is visible and I add new Item in that moment I see that item in comboBox, but I can select it only using scrollBar.

See https://bugreports.qt.io/browse/QTBUG-39420 - feel free to provide a patch :)