QScrollBar vertical scrollbar set width

[SPlatten]

I and working to a specification where the requirement is to have a vertical scrollbar that is only something like 4 pixels wide, is this achievable with the QScrollBar widget?

I've added:

QScrollBar* pScrollBar(new QScrollBar(this));
mpui->pgrdloContent(pScrollBar, 1, 3);
QRect rctGeom(pScrollBar->geometry());
rctGeom.setWidth(rctGeom.width() / 2));
pScrollBar->serGeometry(rctGeom);

The above adds the scrollbar to a QGridLayout in row 1, column 3, however the width doesn't seem to be effected at all.

[hskoglund]

Hi, try:

pScrollBar->setStyleSheet("QScrollBar:vertical { width: 4px; }");

note: using setStyleSheet can shortcircuit other custom settings you apply on the scrollbar

[SPlatten]

@hskoglund , excellent, that worked!, now is there anyway to hide the up and down buttons as they are now quite wrong and not required ?

[hskoglund]

To hide the up/down buttons, perhaps try setting their height to 0, with two more setStyleSheet() invocations, say "QScrollBar:up-arrow { height: 0px; }" and "QScrollBar:down-arrow {height: 0px; }"

You're sure you don't want a vertical QSlider instead? might be better suited

[SPlatten]

@hskoglund , tried that, didn't work, also found this:
https://stackoverflow.com/questions/49890692/how-to-remove-qscrollbar-scroll-buttons

Tried that too, didn't work. I need a scrollbar because it needs to shot the proportion of the image on view.

Also tried:
https://doc.qt.io/archives/qt-4.8/stylesheet-examples.html#customizing-qscrollbar

None of those work either, the only thing that does work is changing the width using the style. I'm using Qt 5.9.2.

So far this is what I've tried:

mpScrollBar->setStyleSheet("QScrollBar::vertical{width: 4px;}"
                           "QScrollBar::handle:vertical,"
                           "QScrollBar::add-line:vertical,"
                           "QScrollBar::sub-line:vertical,"
                           "QScrollBar::up-arrow:vertical,"
                           "QScrollBar::down-arrow:vertical"
                           "{height: 0px;display:none;}");

Only the width is set, everything else isn't working.

[hskoglund]

Hmm, if you're anyway off into setStyleSheet() land, if the only thing keeping you from using a QSlider is the proportional stuff, then you could try applying setStyleSheet() on QSlider instead, say:

mpSlider->setStyleSheet(QString(
        ".QSlider::groove { background: transparent; height: %1px; } "
        ".QSlider::handle { height: %2px;}").arg(scrollbarHeight).arg(thumbHeight));

you'll have to calculate the thumbHeight (i.e. the movable part of the slider) from the proportion of the image compared to the view, but this approach might be more fruitful :-)

[SPlatten]

@hskoglund , thank you, I will give it a go.

[SPlatten]

@hskoglund , one thing that comes to mind....the slider value is normally at the center point of the handle? Can this be offset? If the handle is adjusted to show a proportional representation then the value would have to be at the very top of the handle.

[SPlatten]

@hskoglund , I'm not sure this is going to work, for starters using the StyleSheet to set the handle width and height doesn't seem to work and there is the other issue where the origin / value seems to be central to the orientation of the handle.

[hskoglund]

Hi, dug up some old code that assumes you have a vertical QSlider with a height of say 400 pixels, minimum = 0, maximum = 400, singleStep = 1 and pageStep = 25:

mpSlider->setStyleSheet(
    "QSlider::groove { background: transparent; width: 4px; } "
    "QSlider::handle { background: blue; border-radius: 5px; border: 1px solid gray; height:200px;}");

then moving the slider will give you values between 0 and 400 :-)

Edit:
here's the simplified test program, create a vanilla QWidget app, in mainwindow.cpp and #include "qslider.h" and insert this code in MainWindow::MainWindow() after ui->setupUi(this):

auto mpSlider = new QSlider(Qt::Vertical,this);
mpSlider->setGeometry(QRect(100,100,100,400));
mpSlider->setRange(0,400);
mpSlider->setStyleSheet(
"QSlider::groove { background: transparent; width: 4px; } "
"QSlider::handle { background: blue; border-radius: 5px; border: 1px solid gray; height:200px;}");
connect(mpSlider,&QSlider::valueChanged,[this](int value) { setWindowTitle("Slider value: " + QString::number(value));});

should give you this:

[SPlatten]

@hskoglund, thank you, where on the slider is the value indicated?

[mrjj]

@SPlatten

QSlider don't show the current value as far as i know.

there is a handy subclass here to get text the handle.
https://stackoverflow.com/questions/18383885/qslider-show-min-max-and-current-value

Also do note that a 4 pixel slider will drive people nuts on a hi res screen.

[SPlatten]

@mrjj , the application itself is being written for a specific target in mind, its for training software.

[mrjj]

@SPlatten

Hi
Ok. Well so its purpose with such a tiny scrollbar.
I guess that makes better sense then.

[SPlatten]

@mrjj , its not really my decision, I'm working to a specification which includes mock images.

[SPlatten]

@hskoglund , sorry for the delay, been busy with other stuff.

    QRect rctGeom(rect());
    int intHeight(rctGeom.height()),
    //Using the maximum and minimum actual values calculate percentage visible
        intSpan(truth::msintMaximum - truth::msintMinimum);
    double dblPercent = (double)intHeight / (double)intSpan,
    //Now work out how much of the scale the percentage into the visible area
           dblVisible = dblPercent * intHeight;
    QString strStyle(QString("QSlider::handle {"
                             "background:blue;"
                             "border-radius: 0px;"
                             "border: 1px solid gray;"
                             "height: %1px;}").arg((int)dblVisible));
    truth::mspSlider->setStyleSheet(strStyle);

intHeight contains 486
intSpan contains 2000
dblPercent contains 0.243
dblVisible contains 118.098
strStyle contains:

QSlider::handle {background:blue;border-radius: 0px;border: 1px solid gray;height: 118px;}

However what I'm seeing on the screen is:

So clearly the handle is not 118 px, what haven't I done?

[hskoglund]

Hi, I also stumbled on this (QSlider refusing to cooperate). What's odd here is to make that height of 118px work, you also have to mess with QSlider's groove in your setStyleShee() call. And the easiest way was to make it invisible, like this:

QString strStyle(QString(
"QSlider::groove { background: transparent; } "
"QSlider::handle {"
"background:blue;"
"border-radius: 0px;"
"border: 1px solid gray;"
"height: %1px;}").arg((int)dblVisible));

Ok problem solved, but now you got another problem: no groove.
If you need one, you can draw your own, I used a QFrame say like this:

auto pFrame = new QFrame(mpSlider->parentWidget());
pFrame->setGeometry(mpSlider->geometry());
pFrame->setFrameStyle(QFrame::VLine | QFrame::Sunken);
pFrame->stackUnder(mpSlider);   // z-order (important!)

note: maybe some more settings are needed on that QFrame for grey color etc. to make it look more like a QSlider's groove :-)

[SPlatten]

@hskoglund , thank you, that works.