Minimizing Vertical Spacing in QGridLayout

[Absurd]

Thank you SGaist.
Setting:

layout->setContentsMargins(0, 0, 0, 0);
layout->setSpacing(0);

Did not remove the margins...

Here's what I have:

PacketHeader::PacketHeader(QWidget* parent, const QString &type) : QWidget(parent) {

    QGridLayout* header = new QGridLayout;

    for (unsigned row = 0; row < 4; row++) {
        for (unsigned column = 0; column < 32; column++) {
            Bit* bit = new Bit;
            header->addWidget(bit, row, column);
        }
    }

    header->setSpacing(0);
    header->setContentsMargins(0, 0, 0, 0);

    headerType = new QLabel(type);

    QVBoxLayout* mainLayout = new QVBoxLayout;
    mainLayout->addWidget(headerType);
    mainLayout->addLayout(header);

    setLayout(mainLayout);
    setWindowTitle("Header");
}

Where Bit (inherits from QLineEdit) has the following in its constructor:

Bit::Bit(QWidget* parent) : QLineEdit(parent) {
    QFont font("Courier New", 10, QFont::Bold);
    setFont(font);
    setMaxLength(1);
    setFrame(false);
    setFixedWidth(16);
    setAlignment(Qt::AlignCenter);
    setText("0");
}

And that's the result:

Are you sure that the margin I see is not a margin that's being claimed by the QLineEdit (rather than the QGridLayout)?

I can upload the full code if needed, although there's not much more than the above...

Thanks.

[SGaist]

What desktop environment are you using ?

[Absurd]

It's a remote server that I am connecting to through ssh, it's running linux.

$ uname -a
Linux 3.10.0-327.el7.x86_64 #1 SMP Thu Oct 29 17:29:29 EDT 2015 x86_64 x86_64 x86_64 GNU/Linux

(Is that what you meant by "desktop environment"?)

[mrjj]

@Absurd
Hi
If there are more room left after all lineEdits are layout, there will still be space.
QLineEdit do not claim any extra space.
I had to insert a spacer to compress them or else the layout would divide extra space
amount the lineedits.

So if you window/layout area is not 100% the size of one row of lineEdits, it might add some space due to you setting fixed size on the lineEdits.

[Absurd]

I did nothing special on the QGridLayout nor on the QLineEdit...
You can see the constructor for the main Widget above (PacketHeader), and even when commenting all size-related lines in the Bit constructor (which is actually a QLineEdit):

Bit::Bit(QWidget* parent) : QLineEdit(parent) {
    QFont font("Courier New", 10, QFont::Bold);
    setFont(font);
    //setMaxLength(1);
    setFrame(false);
    //setFixedWidth(16);
    setAlignment(Qt::AlignCenter);
    setText("0");
}

I am still left with this:

Here's the main entry for the window, in case anyone kindly wants to try running:

int main(int argc, char* argv[]) {
    QApplication app(argc, argv);

    PacketHeader element;
    element.show();

    return app.exec();
}

Thanks.

edit
My goal is to have 4 x 32 one-character boxes such that the boxes will be packed together with no space between them.

edit 2
mrjj, I am guessing that you are using some kind of Designer Tool, can you please share the code that's generated? Maybe I can take a look at it as a reference to understand what I am doing wrong...

[mrjj]

Hi
Yes, it the one build into Creator.
Anyway, i fiddled around with it and came up with

QLineEdit *MainWindow::MakeEdit()
{
    QLineEdit *line = new QLineEdit();
    line->setMaxLength(1);
    line->setFrame(false);
    line->setFixedSize(QSize(16, 16));
    line->setAlignment(Qt::AlignCenter);
    line->setText("0");
    return line;
}

void MainWindow::SetupGrid(QGridLayout *layout )
{
    layout->setContentsMargins(0, 0, 0, 0);
    layout->setSpacing(0);
    int rowCount=4;
    int colCount=32;
    for (int row = 1; row <= rowCount; ++row) {
        for (int col = 1; col <= colCount; ++col) {
            layout->addWidget( MakeEdit(), row, col );
        }
    }

    auto horizontalSpacer = new QSpacerItem(40, 20, QSizePolicy::Expanding, QSizePolicy::Minimum);
    layout->addItem(horizontalSpacer, 0, colCount+1, 1, 1);


    auto verticalSpacer = new QSpacerItem(20, 40, QSizePolicy::Minimum, QSizePolicy::Expanding);
    layout->addItem(verticalSpacer, rowCount+1, 0, 1, 1);
}

void MainWindow::on_pushButton_released()
{
    SetupGrid(ui->gridLayout);
}

Which seems to hold them together, even when window is resized so
layout has far more space to the right.

test project
https://www.dropbox.com/s/la5qrlz48nlwr9p/TonsOfEdit.zip?dl=0

[Absurd]

:(
I changed my Bit imp. to this:

Bit::Bit(QWidget* parent) : QLineEdit(parent) {
    //QFont font("Courier New", 10, QFont::Bold);
    //setFont(font);
    setMaxLength(1);
    setFrame(false);
    //setFixedWidth(16);
    setFixedSize(QSize(16, 16));
    setAlignment(Qt::AlignCenter);
    setText("0");
}

(basically exactly like yours word-for-word - I even ruled out the possibility that it is somehow the QFonts fault), but still the same:

[mrjj]

@Absurd
And you use QSpacerItem too ??
Thats so odd then.

[SGaist]

@Absurd said in Minimizing Vertical Spacing in QGridLayout:

It's a remote server that I am connecting to through ssh, it's running linux.

$ uname -a
Linux 3.10.0-327.el7.x86_64 #1 SMP Thu Oct 29 17:29:29 EDT 2015 x86_64 x86_64 x86_64 GNU/Linux

(Is that what you meant by "desktop environment"?)

No that's not, examples of desktop environments:

• KDE
• Gnome
• LXDE
  etc.

[Absurd]

@mrjj ; no QSpacerItem. I'll try adding that two and will update.
@SGaist ; it's GNOME.

[mrjj]

@Absurd
The spacer item is the key. else it will distribute the remaining space among the lineEdits.
its how layout works.

[Absurd]

But that's the thing; why is there remaining space in the first place, if I used QGridLayout.setSpacing(0)?

[J.Hilk]

@Absurd
because you do set a fixed size to the content of the layout. If the content can not fill the layout, margins ans spacings are added, or what would you expect to happen?

[Absurd]

@J-Hilk see what I wrote above:

@Absurd said in Minimizing Vertical Spacing in QGridLayout:

I did nothing special on the QGridLayout nor on the QLineEdit...
You can see the constructor for the main Widget above (PacketHeader), and even when commenting all size-related lines in the Bit constructor (which is actually a QLineEdit):

Bit::Bit(QWidget* parent) : QLineEdit(parent) {
    QFont font("Courier New", 10, QFont::Bold);
    setFont(font);
    //setMaxLength(1);
    setFrame(false);
    //setFixedWidth(16);
    setAlignment(Qt::AlignCenter);
    setText("0");
}

I am still left with this:

Here's the main entry for the window, in case anyone kindly wants to try running:

int main(int argc, char* argv[]) {
    QApplication app(argc, argv);

    PacketHeader element;
    element.show();

    return app.exec();
}

Thanks.

edit
My goal is to have 4 x 32 one-character boxes such that the boxes will be packed together with no space between them.

edit 2
mrjj, I am guessing that you are using some kind of Designer Tool, can you please share the code that's generated? Maybe I can take a look at it as a reference to understand what I am doing wrong...

Specifically:

and even when commenting all size-related lines in the Bit constructor

[J.Hilk]

@Absurd

#include <QGridLayout>
#include <QLineEdit>
#include <QSpacerItem>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    QGridLayout *gLay = new QGridLayout(this);
    gLay->setSpacing(0);
    gLay->setMargin(0);

    for(int i(0); i < 4; i++){
        for(int j(0); j < 32; j++) {
            if( j == 0 || j == 31){
                gLay->addItem(new QSpacerItem(0,0,QSizePolicy::Expanding, QSizePolicy::Minimum),i,j);
            } else {
                QLineEdit *le = new QLineEdit(this);
                le->setMaxLength(1);
                le->setFixedWidth(16);
                le->setAlignment(Qt::AlignCenter);
                le->setText("0");
                gLay->addWidget(le,i,j,1,1, Qt::AlignCenter);
            }
        }
    }
}

works fine for me:

---

ups, j should run to 34 so that there are 32 QLineEdits.

[Absurd]

Thanks for the help. Appreciate it!

Ok, running the exact same code as yours, I get different results...

main.cpp:

#include <QApplication>
#include "Widget.h"



int main(int argc, char* argv[]) {
    QApplication app(argc, argv);

    Widget widget;
    widget.show();

    return app.exec();
}

Widget.h:

#ifndef WIDGET_H_
#define WIDGET_H_

#include <QWidget>

class Widget : public QWidget {
    Q_OBJECT

public:
    Widget(QWidget* parent = 0);
};

#endif

Widget.cpp:

#include "Widget.h"
#include <QGridLayout>
#include <QLineEdit>
#include <QSpacerItem>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    QGridLayout *gLay = new QGridLayout(this);
    gLay->setSpacing(0);
    gLay->setMargin(0);

    for(int i(0); i < 4; i++){
        for(int j(0); j < 32; j++) {
            if( j == 0 || j == 31){
                gLay->addItem(new QSpacerItem(0,0,QSizePolicy::Expanding, QSizePolicy::Minimum),i,j);
            } else {
                QLineEdit *le = new QLineEdit(this);
                le->setMaxLength(1);
                le->setFixedWidth(16);
                le->setAlignment(Qt::AlignCenter);
                le->setText("0");
                gLay->addWidget(le,i,j,1,1, Qt::AlignCenter);
            }
        }
    }
}

And then:

$> qmake-qt4 -project
$> qmake-qt4 testing.pro
$> make
$> ./testing

and the result:

---

Maybe I am using different qt version?
Maybe it's an environment issue?
What else could it be?

[Absurd]

Important update
I tried to compile & run the same code on another machine, and guess what...

$> uname -a
Linux 4.15.0-42-generic #45-Ubuntu SMP Thu Nov 15 19:32:57 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Does anyone has an idea on why would different machine render the GUI differently?

[mrjj]

@Absurd
Are the both linuxes ? ( with GNOME)

[Absurd]

@mrjj
Yes, they are both Linux-based, but not both are GNOME:

The bad:

$> uname -a 
Linux 3.10.0-327.el7.x86_64 #1 SMP Thu Oct 29 17:29:29 EDT 2015 x86_64 x86_64 x86_64 GNU/Linux
$> ls /usr/bin/*session
/usr/bin/gnome-session*  /usr/bin/gnome-session-custom-session*
$> qmake-qt4 --version
QMake version 2.01a
Using Qt version 4.8.5 in /usr/lib64

The good:

$> uname -a
Linux 4.15.0-42-generic #45-Ubuntu SMP Thu Nov 15 19:32:57 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
$> ls /usr/bin/*session
/usr/bin/byobu-select-session*  /usr/bin/dbus-run-session*
$> qmake-qt4 --version
QMake version 2.01a
Using Qt version 4.8.7 in /usr/lib/x86_64-linux-gnu

[mrjj]

@Absurd
Hi
Could yo try to do

#include <QDebug>
#include <QStyle>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    qDebug() << QApplication::style()->objectName();
...normal code...

and see if they list different styles ?