The better way to implement weird table or list

[Gourmet]

Up...

Can this be implemented with QML? I do not have much experience with QML - just only some settings for some widgets. Can list be constructed in QML? Can each item in list be constructred in QML? How do this? Is there any example of similar task solved in QML?

[J.Hilk]

@Gourmet yes it can,

My preferred method is,

• create a class that contains all your information you want to show. Each Information has to be a Q_PROPERTY
• create a QList<QObject*> with instances of your class as items
• make that list available to QML
• Set that list as model for a ListView
• design your delegate in QML and access the class data via modelData.propertyName

[Gourmet]

@J.Hilk thanx but for me this looks little weird. I do not know yet how implement steps 3 and 5. Is there any example how do that? Or can anybody explain these steps deeper?

[J.Hilk]

@Gourmet
Just made a quick and dirty one ;)
https://github.com/DeiVadder/ListViewExample

[Gourmet]

@J.Hilk thanx, I have first check if this will work in QGraphicsWidget. I need find the way around this bug.

[J.Hilk]

@Gourmet That I don't know, but it will work with QQuickWidget, if that helps ?

https://doc.qt.io/Qt-5/qquickwidget.html

[Gourmet]

@J.Hilk It must work. But will it or not - I am not sure yet. Unfortunately right now I have make other work. Will test this later.

By the way - for QQuickWidget - will Window{} container in your main.qml needed or just only ListView{} required?

[J.Hilk]

@Gourmet for a qquickwidget it is irrelevant what the root element is, so yes it should work

[Gourmet]

This post is deleted!

[Gourmet]

@J.Hilk Your example works but my attempt does not. Here I include link to temporary zip with my source code.

https://dropmefiles.com/uezkn

Zip will be destroyed after week since this moment.

After setContextProperty() for QQuickWidget with 100 items it's size is 0,0. This tells line 20 in testlist.cpp. If line 14 in mainwindow.cpp is uncommented then one record with person_0 appears. But it does not have checkbox. I do not know how tune QML widget size to make it visible inside graphics scene. Line 12 in testlist.cpp doesn't help.

[J.Hilk]

@Gourmet
ok, couple of points,

1. seems like I was wrong, ListView can't be the root element - so I wrapped it in an Item{}

2. you QML objects needs a size or it won't draw anything. With setResizeMode(QQuickWidget::SizeRootObjectToView); set you have to resize it once from cpp side.
   With setResizeMode(QQuickWidget::SizeViewToRootObject); you define the size with width:xxxx and height:yyyy of your root element in qml

3. set the rootContext property before you set the source, that will remove the not defined error

[Gourmet]

@J.Hilk ok, I changed Window container to Item container and TestList code to follwing:

TestList::TestList(QWidget *p, uint _width) : QQuickWidget(p), width(_width)
{
    qsrand(QTime::currentTime().second());
    connect(this, SIGNAL(statusChanged(QQuickWidget::Status)), SLOT(changedStatus(QQuickWidget::Status)));
   setResizeMode(QQuickWidget::SizeRootObjectToView);
}

void TestList::FillList()
{
    const int num = 100;
    for( int i = 0; i < num; i++ )
        notebook.append( new NoteEntry("person_"+QString::number(i), qrand()%60+20, i%2) );
    rootContext()->setContextProperty("DeathList",QVariant::fromValue(notebook));
    setSource(QUrl("qrc:/main.qml"));
    if( ! rootContext()->isValid() )
    {
        qWarning()<<"QML is not valid";
        QApplication::quit();
    }
    resize( width, num*50 );
}

Where width is ui->graphicsView.geometry().width(). Last resize calculates height as elements number multiplied to delegate height which is set in main.qml line 22. I do not know how extract this value for C++ code. The result is frustrating...

and bunch of error messages in console:
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete, missing attachment.

If I set width and height hard in main.qml and use setResizeMode(QQuickWidget::SizeViewToRootObject); then I see lines of my list. Of course only those who fit to it's size. With height 1000 px it works well and scrolls. Even it works with height 4050 - list has 81 person (from person_0 to person_80).

Checkboxes work, background color changes. But with height 4100 it breaks and looks like on the first picture here. So why this happens?

If this is some kind of memory limitation then I cannot use it. I need create application for possible couple hundreds of items. Each item can take about 100-150 pixels height. That means list can be up to 30000 pixels height. And may be more if the item height will grow.

[J.Hilk]

@Gourmet
this works for me:

//mainWindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}
class TestList;
class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private:
    Ui::MainWindow *ui;
protected:
    void closeEvent(QCloseEvent*)override;
    void resizeEvent(QResizeEvent *)override;

    TestList *tl= nullptr;
};

#endif // MAINWINDOW_H

//mainWindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <testlist.h>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    tl = new TestList(0);
    tl->FillList();
    tl->move(0,0);
    
    QGraphicsView* gv = ui->graphicsView;
    QGraphicsScene* scene;
    gv->setScene( scene = new QGraphicsScene( tl->geometry(), this ) );
    scene->addWidget( tl, Qt::Widget );
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::closeEvent(QCloseEvent *)
{
    QApplication::exit();
}
void MainWindow::resizeEvent(QResizeEvent *)
{
    if(tl){
        tl->resize(ui->graphicsView->size());
    }
}

//main.qml
import QtQuick 2.9
import QtQuick.Controls 2.2

Item{
    id:root

    ListView {
        id:lView
        anchors.fill: parent

        model: DeathList

        orientation: ListView.Vertical

        delegate: Rectangle {
            color: modelData.dead ? "darkred" : "white"

            readonly property int numberOfVisibleItems: 10
            
            width: lView.width
            height: root.height /numberOfVisibleItems

            Text {
                id:nameField
                anchors.left: parent.left
                anchors.verticalCenter: parent.verticalCenter
                text: modelData.name
                color: modelData.dead ? "white" : "black"
                width: contentWidth
            }

            Text {
                anchors.left: nameField.right
                anchors.leftMargin: 20
                anchors.verticalCenter: parent.verticalCenter
                text: modelData.age + qsTr("years old")
                color: modelData.dead ? "white" : "black"
                width: contentWidth
            }

            CheckBox {
                text: qsTr("is dead ?")
                anchors.right: parent.right
                anchors.top:parent.top
                anchors.bottom: parent.bottom
                checked: modelData.dead
                onCheckedChanged: modelData.dead = checked
            }
        }
    }
}

with a resize mode of SizeRootObjectToView

[Gourmet]

@J.Hilk I have found that Item height (and probably width) is limited to 4096 (2^12) pixels. When it grows up to 4097 pixels - the black field appears. Can this be some limitation of OpenGL engine used for QML? If yes then how break this limit? I need at least 2^15 pixels for height.

[J.Hilk]

@Gourmet you don't need to set the width so high!

Only what's in the viewport, actually visible on your screen is rendered.
If you're forcing the width and hight of the component bigger you may only end up costing you performance.

ListView comes with a build in scrollarea/flickable. -> unlimited size, but you only see what's inside the viewport

[Gourmet]

@J.Hilk looks like you did not read all I had wrote and my code. I need mandatory use QGraphicsScene to be able easy scale window content for different Android screen sizes.

I do not use your last code - it does not solve the task. And does not contain anything new for me. I already have got my own working code - almost have got. But rested in size restriction.

I tried use Window container - it gives scrollable list of all 100 items in my TestList. But this window appears outside of main window. I need list inside it. When I use Item container it appears inside main window. That's what I need. And all works fine as needed - long list scrolls inside QGraphicsScene. And it scales as well. But looks like Item's size is limited to 4096x4096 pixels. Is there any way to grow this limit? How can I create Item with size 600x32767?

PS: Ooops... looks like 4096x4096 is not the Item limit. But a limit of something in QGraphiscScene instead. May be QGraphicsItem linit. Or QGraphicsProxyWidget. I now removed Item from code and left only ListView. With setting it's height to 4096 it works well (yes, without root Item). But with settings it's height to 4097 it breaks.

[Gourmet]

I have tested limits of QGraphicsProxyWidget and QGraphicsItem - they work well with huge push button, 32000 pixels height. But large ListView works well too inside Window{}. Perhaps problem is in Item{}'s restriction. Otherwise it is a bug...

[Gourmet]

Found posting with similar problem. Unfortunately no solution there.