Is possible to have a widget that doesnt scroll in a QScrollArea? - c++

Question

Given this example:
Suppose A and B are QWidgets
Is it possible to keep everything starting from B static when the QScrollArea widget is scrolled?
The QScrollArea occupies the entire GUI, B is inside it to let the vertical ScrollBar closer to the right border of the GUI, or it would look like this:
What I can do in this case?

Answer 1

It is possible. You have to make use of the scrollbar being a widget of its own.
Here is the method:
Change your window in Qt Designer to be: spacer, QScrollArea (that will contain widget A), spacer, widget B, spacer; everything is in a QGridLayout (or QHBoxLayout but please read until the end).It is because widget B is outside the scroll area that it will not move during scrolling.
In your widget constructor, after ui->setupUi(); reparent and move the vertical scrollbar of your QScrollArea with these lines of code:
scrollArea->verticalScrollBar()->setParent(w);
layout->addWidget(sa->verticalScrollBar()); //Adds the scrollbar to the right of the layout.
Note about the margins:Obviously, you can easily push the scrollbar to the very right of your window by setting the layout right margin to 0.
If you also want it to cover the entire height of your window, while keeping some space between the other widgets and the window's border, that is where a QHBoxLayout will not suffice and you need a QGridLayout instead, set its top and bottom margin to 0 and add spacers (fixed size) to obtain the same visual result.
The C++ code for such a window would be:
QWidget* widget = new QWidget();
QGridLayout* layout = new QGridLayout(widget);
layout->setSpacing(0);
layout->setContentsMargins(9, 0, 0, 0);
widget->setLayout(layout);
QScrollArea* scrollArea = new QScrollArea(widget);
scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
QWidget* widgetB = new QLabel("Widget B", widget);
//Creates the spacer that will "simulate" the top and bottom margins
QSpacerItem* topSpacer = new QSpacerItem(0, 9, QSizePolicy::Minimum, QSizePolicy::Fixed),
* bottomSpacer = new QSpacerItem(0, 9, QSizePolicy::Minimum, QSizePolicy::Fixed);
layout->addItem(topSpacer, 0, 0);
layout->addWidget(scrollArea, 1, 0);
layout->addItem(bottomSpacer, 2, 0);
layout->addWidget(widgetB, 1, 1);
//Moves the scrollbar outside the scroll area
scrollArea->verticalScrollBar()->setParent(widget);
layout->addWidget(scrollArea->verticalScrollBar(), 0, 2, 3, 1);
QLabel* innerLabel = new QLabel("Some big label to force the scrolling");
scrollArea->setWidget(innerLabel);
innerLabel->setMinimumHeight(500);
widget->show();