[FIXED] Set minimal reasonable width for a QScrollArea

Issue

I am relatively new to Qt, which I access through PySide.

I have a longish list of content that I want to make vertically scrollable. The horizontal size is not an issue. I tried using QScrollArea for that. Here is a minimal example:

import sys

import PySide.QtGui as gui

application = gui.QApplication(sys.argv)

window = gui.QScrollArea()
list = gui.QWidget()
layout = gui.QVBoxLayout(list)

for i in range(100):
    layout.addWidget(gui.QLabel(
        "A something longish, slightly convoluted example text."))

window.setWidget(list)

window.show()

sys.exit(application.exec_())

What happens:

1. The scroll-area sets its horizontal size to the size needed for the labels

2. It notices that the vertical space is insufficient, so it adds a vertical scrollbar.

3. Due to the vertical scrollbar, the horizontal space is now insufficient as well, and so the horizontal scrollbar is also shown.

I can make the horizontal scrollbar go away with setHorizontalScrollBarPolicy, but the main problem persists: the vertical scrollbar obscures part of the labels.

How can I set the width of the scroll-area to the minimal value which does not need a horizontal scrollbar?

Solution

Your example is somewhat unrealistic, because the scroll-area is made the top-level window. More typically, it would be a child widget, and its initial size would be determined by a layout, and would be indirectly constrained by the sizes of other widgets and/or layouts. As a top-level window, the constraints are different, and partly under the influence of the window-manager (the exact behaviour of which can vary between platforms).

To ensure that the scroll-area has the correct size, you must set a minimum width for it, based on its contents, and also allowing for the vertical scrollbar and the frame. It is also probably best to set the widgetResizable property to True and add an expandable spacer to the end of the contents layout.

In the example below, I have changed the background colour of the labels to make it easier to see what is going on. I have also allowed resizing the window smaller than its initial size, by resetting the minimum width after it is shown - but that is optional.

import sys

import PySide.QtGui as gui

application = gui.QApplication(sys.argv)

window = gui.QScrollArea()
window.setWidgetResizable(True)
list = gui.QWidget()
layout = gui.QVBoxLayout(list)

# just for testing
window.setStyleSheet('QLabel {background-color: red}')

for i in range(30):
    layout.addWidget(gui.QLabel(
        "A something longish, slightly convoluted example text."))

layout.addStretch()

window.setWidget(list)

window.setMinimumWidth(
    list.sizeHint().width() +
    2 * window.frameWidth() +
    window.verticalScrollBar().sizeHint().width())

window.show()

# allow resizing smaller
window.setMinimumWidth(1)

sys.exit(application.exec_())

Answered By - ekhumoro