QSplitter Stretching Factors behave differnt from normal ones

Question

I want to create a flexible layout, where the User can resize Widgets, but still give a good default layout. I'm using the Qt Designer for everything.

As a minimal example I used a simple Windows with a Widget and a plainTextEdit. The later one seems to cause the problems, which is why I choose it. At first I built it without the Splitter which worked just fine. The Stretching factors are 1:1 by the way.

Now I put both widgets in a Splitter (by breaking the main layout, putting both widgets in a Splitter and setting a new layout to the main widget). Resizing still works but the stretching factors behave weird:

The PlainTextEdit seems to take up far to much space. The Stretching Factors are still at 1:1. I found a workaournd, by changing the stretching of the upper widget to a much higher value (in this case 9:1), which looks good again:

So my question is: Why do the stretching factors begin to behave weird when I put the images in a Splitter? And how can I solve this without using arbitrary guessed stretching factors?

Answer 1

QSplitter::setSizes() can be used to set relative sizes. According to the documentation, "any additional/missing space is distributed amongst the widgets according to the relative weight of the sizes".

In this case, it is a bit ugly, since you have to add this in your code rather than editing your layout in QDesigner (normally, you would want to define your layout only at one place), but still it is quick and works:

MyWindow::MyWindow(QWidget* parent):
QWidget(parent)
{
    m_Ui.setupUi(this);
    m_Ui.splitter->setSizes({2000, 1000, 1000});

However, I had to use big numbers (instead of {2, 1, 1}), maybe because at this point, the window is not completely set up yet (apparently, Qt is not a big fan of RAII...). Also, this kind of notation works probably only with a recent C++ version, otherwise you can also define the QList in some extra lines.