which already has a layout?

Box layout managers take the space they get from their parent layout or widget, divide it up into a number of boxes, or cells, and make each widget in the layout fill one box.

QHBoxLayout is one of the two available box layouts in PyQt. This layout manager allows you to arrange widgets horizontally, one next to the other. The widgets are added to the layout from left to right. This means that the widget that you add first in your code will be the left-most widget in the layout.

To add widgets to a QHBoxLayout object, you call .addWidget(widget, stretch, alignment) on the layout object. This method takes one required argument and two optional arguments:

Here’s a small application that shows how to create a horizontal layout using QHBoxLayout. In this example, you’ll use QPushButton objects to better visualize where each widget will be placed in the layout according to the order in which you add the widgets to your code:

On line 15, you create a QHBoxLayout object called layout. On lines 17 to 19, you add three buttons to layout using .addWidget(). Note that you pass 1 and 2 to the stretch parameter in the Center and Right-Most buttons, respectively. On line 21, you set layout as your window’s top-level layout using .setLayout().

If you run this application, then you’ll get the following window on your screen:

This window contains three buttons arranged in a horizontal fashion. Note that the Left-Most button corresponds to the first button that you add in your code. So, buttons are shown in the same order (from left to right) that you add them in your code (from top to bottom).

PedanticHacker

Firstly, delete the line self.setLayout(layVer)

then fix

to be

Martin Fitzpatrick

This error occurs because you're trying to set a layout on a QMainWindow. The QMainWindow is a special widget which has a built-in layout, to handle things link menus, toolbars and dock widgets.

For windows based on QMainWindow you can only set a central widget -- that is, the widget that appears in the center of the window. But if you remember from the PyQt5 layouts tutorial you can set a layout on an empty QWidget and add anything you want to it that way.

So the trick is: for controlling the layout of a mainwindow we first create a QWidget to act as a "container", use that widget as our central widget and apply the layout to it to add other widgets.

_Ali Sanawi Garrousi__

If you ever started Krita 3.x in your command line, and had a look at the console output, you may noticed the following warning.

Krita recently announced the release of 3.1.3-alpha-2, and while testing I saw this warning and decided to investigate why this warning happens.

There was already a similar question posted on StackOverflow. And the best answer’s initial paragraph gave me a hint of what to look for.

So, somewhere in Krita code, there was a a QWidget being created, and layouts were being added to it more than once. To find where the issue was happening was quite easy. A breakpoint at main.cc where the application is initialized, then step through a few times, until the message appeared in the console.

Further investigation led me to the History docker (the one that shows undo steps) constructor.

Here the QWidget created receives both QHBoxLayout and QVBoxLayout. Again, searching the Internet a little bit, then came across this post with a good example of a QWidget with QHBoxLayout and QVBoxLayout. Here’s what the constructor looks after the patch has been applied.