Issues with sizing when I add widget to Vbox Layout

I'm running to issues with QLayouts.

class welcomeWidget(QWidget):
    def __init__(self):
        super().__init__()
        self.initText()
        self.organize()

    def initText(self):
        self.welcome = QLabel("Welcome to Name!", self)
        self.info = QLabel("This program allows you to....", self)
        self.message = QLabel("First, you must enter some data...", self)
        self.proceed = QLabel("Click on 'Next >>' to proceed.", self)

    def organize(self):
        vbox = QVBoxLayout(self)
        scroll = QScrollArea(self)
        vbox.addWidget(scroll)
        wid = QWidget(self)
        vevobox = QVBoxLayout(wid)

        vv = QVBoxLayout()
        vv.addWidget(self.welcome)
        vv.addWidget(self.info)
        vevobox.addLayout(vv)
        self.show()

It looks like this...

Idk what to do, and whenever I add the other QLabels they all just disappear.

Solution

Before showing the solution you have to explain some things:

There are 3 ways to set a layout in a widget:
1. Create the widget without a parent and then the widget indicates that it uses that layout with setLayout():
```
lay = QVBoxLayout()
foo_widget.setLayout(lay)
```
2. Point to what widget to manage when the layout is built.
```
lay = QVBoxLayout(foo_widget)
```
3. The previous methods are equivalent, but the third method is to establish it as the son of an already established layout.

A widget can only have a layout as a top-level, so if only the last one remains:

lay1 = QVBoxLayout(foo_widget)
lay2 = QVBoxLayout(foo_widget)

# The above is equivalent to:

lay1 = QVBoxLayout()
lay2 = QVBoxLayout(foo_widget)

A widget is the son of another widget when it is set as a parent in the constructor, or it is established as part of a layout that handles the position of the widget:

1.
```
child_1 = Foo_Widget(some_widget)
```
2.
```
lay = Foo_Layout(some_widget)
child_2 = Foo_Widget()
lay.addWidget(child_2)
```

So if you consider the above you can reduce your code:

...
def initText(self):
    self.welcome = QLabel("Welcome to Name!")
    self.info = QLabel("This program allows you to....")
    self.message = QLabel("First, you must enter some data...", self)
    self.proceed = QLabel("Click on 'Next >>' to proceed.", self)

def organize(self):
    vbox = QVBoxLayout(self)
    scroll = QScrollArea()
    vbox.addWidget(scroll)

    wid = QWidget(self)
    vevobox = QVBoxLayout(wid)

    vv = QVBoxLayout()
    vv.addWidget(self.welcome)
    vv.addWidget(self.info)
    vevobox.addLayout(vv)

    self.show()

Using the above, the following tree can be assembled:

welcomeWidget
├── message
├── proceed
├── vbox (QVBoxLayout)
│   └── scroll
└── wid 
    └── vevobox (QVBoxLayout)
        └──vv (QVBoxLayout)
           ├── info
           └── welcome

And as you see is what is expected, for example there are 2 labels that are shown behind everything since they were first established without a layout, then a layout was established where the QScrollArea was placed, so this last one took all the available space , and finally the wid widget without layout was placed so it will be in the top-left position, and within that widget the remaining 2 labels were established.

The idea is to have the following structure:

welcomeWidget
└── vbox (QVBoxLayout)
    └── scroll
        └── wid
            └── vv (QVBoxLayout)
                ├── info
                ├── message
                ├── proceed
                └── welcome

Using the above you get the following:

class welcomeWidget(QWidget):
    def __init__(self):
        super().__init__()
        self.initText()
        self.organize()

    def initText(self):
        self.welcome = QLabel("Welcome to Name!")
        self.info = QLabel("This program allows you to....")
        self.message = QLabel("First, you must enter some data...")
        self.proceed = QLabel("Click on 'Next >>' to proceed.")

    def organize(self):
        vbox = QVBoxLayout(self)
        scroll = QScrollArea()
        scroll.setWidgetResizable(True)

        wid = QWidget()
        scroll.setWidget(wid)

        vv = QVBoxLayout(wid)
        vv.addWidget(self.welcome)
        vv.addWidget(self.info)
        vv.addWidget(self.message)
        vv.addWidget(self.proceed)
        vv.addStretch()

        vbox.addWidget(scroll)
        self.show()