How to update entire window on change in QProxyStyle?

[CJha]

When the QPushButton has a long text it looks something like this:

and what I wanted it to look like is this:

To achieve this, I subclassed QProxyStyle and reimplemented the sizeFromContents() function. To test this new method I created a new project, with the UI in preview mode:

Where the spinbox name is btnBorder_spin, button with text "Button 1: 0" has an object name btn_1 and button with text "Button 2: 0" has object name btn_2, button with text "Button 3: Demo" has object name btn_3.

the mainwindow.h

inline int minBtnBorder{10};

class ProxyStyle : public QProxyStyle
{
public:
    QSize sizeFromContents(ContentsType ct, const QStyleOption* opt, const QSize& csz, const QWidget* widget = 0) const
    {
        QSize sz = QProxyStyle::sizeFromContents(ct, opt, csz, widget);
	if(ct == CT_PushButton) {
	    const auto optionPtr = qstyleoption_cast<const QStyleOptionButton*>(opt);
	    QStyleOptionButton customOption = *optionPtr;
	    auto btn = qobject_cast<QPushButton*>(customOption.styleObject);
	    if(!btn->text().isEmpty()) {
	        QFontMetrics fm = opt->fontMetrics;
		int strWidth = fm.boundingRect(btn->text()).width();
		int diffBtnWidth = sz.rwidth() - strWidth;
		if(diffBtnWidth < (2 * minBtnBorder))
			sz.rwidth() = strWidth + (2 * minBtnBorder);
		}
	}
	return sz;
    }
};

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = Q_NULLPTR);

private:
    Ui::MainWindowClass UI;
    int btnCount_1{0};
    int btnCount_2{0};

protected:
    void showEvent(QShowEvent* event) override;

private slots:
    void on_btnBorder_spin_valueChanged(int val);
    void on_btn_1_clicked();
    void on_btn_2_clicked();
    void on_btn_3_clicked();
};

and mainwindow.cpp

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    auto proxyStyle = new ProxyStyle;
    proxyStyle->setBaseStyle(QStyleFactory::create("Fusion"));
    qApp->setStyle(proxyStyle);
    qApp->setFont(QFont("Verdana", 10));
    ui.setupUi(this);
}

void MainWindow::showEvent(QShowEvent* event)
{
    setFixedSize(this->layout()->minimumSize());
}

void MainWindow::on_btnBorder_spin_valueChanged(int val)
{
    minBtnBorder = val;
    update();
}

void MainWindow::on_btn_1_clicked()
{
    ++btnCount_1;
    ui.btn_1->setText(QString("Button 1: ").append(QString::number(btnCount_1)));
}

void MainWindow::on_btn_2_clicked()
{
    ++btnCount_2;
    ui.btn_2->setText(QString("Button 2: ").append(QString::number(btnCount_2)));
}

void MainWindow::on_btn_3_clicked()
{
    qDebug() << "Button 3 Clicked";
}

Each time btn_1 is clicked btnCount_1 is incremented and the text on the button is changed, same thing happens with btn_2. When the value of btnBorder_spin is changed the minBtnBorder global variable is set to the new value and a call to update is issued. When btn_3 is clicked only a debug message saying "Button 3 Clicked" is generated.

When I run my code, the window appears normally and I see a border of around 10 px on the sides of the button:

If I change the value in the spinbox to 100 px then nothing changes:

Now if I click on btn_1 then it changes the size of btn_1 accordingly while btn_2 and btn_3 remains fixed at the same previous size:

Only if I click on btn_2 then its size also changes:

Clicking on btn_3 prints the debug output, but its size never changes.

I tried using update() , repaint(), hide() then show() after the value of minBtnBorder is changed but the new value is never visible immediately. It is only visible after I change the text on a button, and the change is only applied to the button whose text has changed. How can I make the changes appear immediately after I change the value of minBtnBorder for all buttons?

[mrjj]

Hi
It might be due being in a layout ?
Did you try calling updateGeometry() on the buttons ?

[CJha]

@mrjj Hi, I did just now but it doesn't work.

void MainWindow::on_btnBorder_spin_valueChanged(int val)
{
    minBtnBorder = val;
    ui.btn_1->updateGeometry();
    ui.btn_2->updateGeometry();
    ui.btn_3->updateGeometry();
    update();
}

[mrjj]

@CJha

Hi
Ok. that is odd since it will resize when clicked. updateGeometry() should make layout recalc.

Is the proxy complete so I can just add 3 buttons to a layout and see myself ?

[CJha]

@mrjj Yes, it is complete. You just have to include the relevant files.

[mrjj]

@CJha

hi
I cannot make it scale/update at all.

What type of layout did you use ?

[CJha]

@mrjj Hi, that is strange. I used a normal layout in Qt Designer. Here is an image:

I didn't change anything about the layout, I just put it there and that is all.

[mrjj]

@CJha
and buttons have default sizePolizy ?

Could you post the UI file content ?

[mrjj]

@mrjj

Ok, got it now.

[CJha]

@mrjj Yes, the sizePolicy, min and max size, etc is all default. All I did was change the text on the buttons.

Here is the UI file content:

/********************************************************************************
** Form generated from reading UI file 'mainwindowggYFGS.ui'
**
** Created by: Qt User Interface Compiler version 5.15.2
**
** WARNING! All changes made in this file will be lost when recompiling UI file!
********************************************************************************/

#ifndef MAINWINDOWGGYFGS_H
#define MAINWINDOWGGYFGS_H

#include <QtCore/QVariant>
#include <QtWidgets/QApplication>
#include <QtWidgets/QHBoxLayout>
#include <QtWidgets/QLabel>
#include <QtWidgets/QMainWindow>
#include <QtWidgets/QPushButton>
#include <QtWidgets/QSpacerItem>
#include <QtWidgets/QSpinBox>
#include <QtWidgets/QVBoxLayout>
#include <QtWidgets/QWidget>

QT_BEGIN_NAMESPACE

class Ui_MainWindowClass
{
public:
    QWidget *centralWidget;
    QVBoxLayout *verticalLayout;
    QHBoxLayout *horizontalLayout;
    QLabel *label;
    QSpinBox *btnBorder_spin;
    QSpacerItem *horizontalSpacer;
    QHBoxLayout *horizontalLayout_2;
    QPushButton *btn_1;
    QSpacerItem *horizontalSpacer_2;
    QPushButton *btn_2;
    QSpacerItem *horizontalSpacer_3;
    QPushButton *btn_3;

    void setupUi(QMainWindow *MainWindowClass)
    {
        if (MainWindowClass->objectName().isEmpty())
            MainWindowClass->setObjectName(QString::fromUtf8("MainWindowClass"));
        MainWindowClass->resize(311, 73);
        centralWidget = new QWidget(MainWindowClass);
        centralWidget->setObjectName(QString::fromUtf8("centralWidget"));
        verticalLayout = new QVBoxLayout(centralWidget);
        verticalLayout->setSpacing(6);
        verticalLayout->setContentsMargins(11, 11, 11, 11);
        verticalLayout->setObjectName(QString::fromUtf8("verticalLayout"));
        horizontalLayout = new QHBoxLayout();
        horizontalLayout->setSpacing(6);
        horizontalLayout->setObjectName(QString::fromUtf8("horizontalLayout"));
        label = new QLabel(centralWidget);
        label->setObjectName(QString::fromUtf8("label"));

        horizontalLayout->addWidget(label);

        btnBorder_spin = new QSpinBox(centralWidget);
        btnBorder_spin->setObjectName(QString::fromUtf8("btnBorder_spin"));
        btnBorder_spin->setMaximum(999);
        btnBorder_spin->setValue(10);

        horizontalLayout->addWidget(btnBorder_spin);

        horizontalSpacer = new QSpacerItem(40, 20, QSizePolicy::Expanding, QSizePolicy::Minimum);

        horizontalLayout->addItem(horizontalSpacer);


        verticalLayout->addLayout(horizontalLayout);

        horizontalLayout_2 = new QHBoxLayout();
        horizontalLayout_2->setSpacing(6);
        horizontalLayout_2->setObjectName(QString::fromUtf8("horizontalLayout_2"));
        btn_1 = new QPushButton(centralWidget);
        btn_1->setObjectName(QString::fromUtf8("btn_1"));

        horizontalLayout_2->addWidget(btn_1);

        horizontalSpacer_2 = new QSpacerItem(40, 20, QSizePolicy::Expanding, QSizePolicy::Minimum);

        horizontalLayout_2->addItem(horizontalSpacer_2);

        btn_2 = new QPushButton(centralWidget);
        btn_2->setObjectName(QString::fromUtf8("btn_2"));

        horizontalLayout_2->addWidget(btn_2);

        horizontalSpacer_3 = new QSpacerItem(40, 20, QSizePolicy::Expanding, QSizePolicy::Minimum);

        horizontalLayout_2->addItem(horizontalSpacer_3);

        btn_3 = new QPushButton(centralWidget);
        btn_3->setObjectName(QString::fromUtf8("btn_3"));

        horizontalLayout_2->addWidget(btn_3);


        verticalLayout->addLayout(horizontalLayout_2);

        MainWindowClass->setCentralWidget(centralWidget);

        retranslateUi(MainWindowClass);

        QMetaObject::connectSlotsByName(MainWindowClass);
    } // setupUi

    void retranslateUi(QMainWindow *MainWindowClass)
    {
        MainWindowClass->setWindowTitle(QCoreApplication::translate("MainWindowClass", "MainWindow", nullptr));
        label->setText(QCoreApplication::translate("MainWindowClass", "Button Side Borders:", nullptr));
        btnBorder_spin->setSuffix(QCoreApplication::translate("MainWindowClass", " px", nullptr));
        btn_1->setText(QCoreApplication::translate("MainWindowClass", "Button 1: 0", nullptr));
        btn_2->setText(QCoreApplication::translate("MainWindowClass", "Button 2: 0", nullptr));
        btn_3->setText(QCoreApplication::translate("MainWindowClass", "Button 3: Demo", nullptr));
    } // retranslateUi

};

namespace Ui {
    class MainWindowClass: public Ui_MainWindowClass {};
} // namespace Ui

QT_END_NAMESPACE

#endif // MAINWINDOWGGYFGS_H

[CJha]

@mrjj I found a way around, by recreating a new ProxyStyle object each time the value of minBtnBorder is changed and then applying this to the qApp.

void MainWindow::on_btnBorder_spin_valueChanged(int val)
{
   minBtnBorder = val;
   auto proxyStyle = new ProxyStyle;
   proxyStyle->setBaseStyle(QStyleFactory::create("Fusion"));
   qApp->setStyle(proxyStyle);
   hide();
   show();
}

It is a workaround at best though.

[mrjj]

@CJha
Good. at least we have a "fix"

The odd thing is that setText

void QAbstractButton::setText(const QString &text)
{
    Q_D(QAbstractButton);
    if (d->text == text)
        return;
    d->text = text;
#ifndef QT_NO_SHORTCUT
    QKeySequence newMnemonic = QKeySequence::mnemonic(text);
    setShortcut(newMnemonic);
#endif
    d->sizeHint = QSize();
    update();
    updateGeometry();
#ifndef QT_NO_ACCESSIBILITY
    QAccessibleEvent event(this, QAccessible::NameChanged);
    QAccessible::updateAccessibility(&event);
#endif
}

just calls
update();
updateGeometry();

[CJha]

@mrjj Yeah, that is very odd. Maybe something else is going on in the background that we are unable to get to!? Although, the code for setText() seems complete.

[mrjj]

@CJha

well i think it might be related to sizeHint() but I have no proof yet :)

[Christian Ehrlicher]

@mrjj said in How to update entire window on change in QProxyStyle?:

d->sizeHint = QSize();

I think this may be the reason. I would guess sizeFromContents() is only called when sizeHint is invalid. Simply set a breakpoint at ProxyStyle ::sizeFromContents() and take a look from where it is called (and why).

[mrjj]

@Christian-Ehrlicher
Hi
Seems to call it from QPushButton::sizeHint() but I failed
to find way to trigger it without altering text.
I guess for full disclosure the source is needed and single step :9
I use wobog for it.