Creating Style Plugin in QT5

[sandro4912]

I try to create my own style plugin. However i cant get it to work.

Here is the code for it:

QT += widgets
CONFIG += c++17

CONFIG += plugin release
TEMPLATE      = lib

TARGET = $$qtLibraryTarget($$TARGET)

target.path = $$[QT_INSTALL_PLUGINS]/styles
INSTALLS += target

#target.path = /home/sandro/Qt/Tools/QtCreator/bin/plugins/styles
#INSTALLS += target


HEADERS       = ../../bronze/bronze/bronzestyle.h \
                bronzestyleplugin.h \
                bronzestyleplugin.h
SOURCES       = ../../bronze/bronze/bronzestyle.cpp \
                bronzestyleplugin.cpp \
                bronzestyleplugin.cpp
RESOURCES     = ../../bronze/bronze/bronze.qrc

OTHER_FILES += bronzestyleplugin.json

#ifndef BRONZESTYLEPLUGIN_H
#define BRONZESTYLEPLUGIN_H

#include <QStylePlugin>

class BronzeStylePlugin : public QStylePlugin
{
    Q_OBJECT
    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QStyleFactoryInterface" FILE "bronzestyleplugin.json")
public:
    QStyle *create(const QString &key) override;
};

#endif // BRONZESTYLEPLUGIN_H

#include "bronzestyleplugin.h"

#include "../../bronze/bronze/bronzestyle.h"

QStyle *BronzeStylePlugin::create(const QString &key)
{
    if (key.toLower() == "bronze") {
        return new BronzeStyle;
    }
    return nullptr;
}

#ifndef BRONZESTYLE_H
#define BRONZESTYLE_H

#include <QProxyStyle>

class BronzeStyle : public QProxyStyle
{
    Q_OBJECT
public:
    void polish(QPalette &palette) override;
    void polish(QWidget *widget) override;
    void unpolish(QWidget *widget) override;

    int styleHint(StyleHint stylehint, const QStyleOption *opt,
                  const QWidget *widget,
                  QStyleHintReturn *returnData) const override;

    int pixelMetric(PixelMetric metric, const QStyleOption *option,
                    const QWidget *widget = nullptr) const override;

    void drawPrimitive(PrimitiveElement pe, const QStyleOption *opt,
                       QPainter *p, const QWidget *w = nullptr) const override;

    void drawComplexControl(ComplexControl cc,
                            const QStyleOptionComplex *opt,
                            QPainter *p, const
                            QWidget *widget = nullptr) const override;


    QRect subControlRect(ComplexControl cc,
                         const QStyleOptionComplex *opt,
                         SubControl sc,
                         const QWidget *widget = nullptr) const override;

public:
    QIcon standardIcon(StandardPixmap standardIcon, const QStyleOption *option,
                       const QWidget *widget = nullptr) const override;

private:
    void drawBronzeFrame(const QStyleOption *option,
                         QPainter *painter) const;
    void drawBronzeBevel(const QStyleOption *option,
                         QPainter *painter) const;
    void drawBronzeCheckBoxIndicator(const QStyleOption *option,
                                     QPainter *painter) const;
    void drawBronzeSpinBoxButton(SubControl which,
                                 const QStyleOptionComplex *option,
                                 QPainter *painter) const;
};

#endif // BRONZESTYLE_H

#include "bronzestyle.h"

#include <QAbstractButton>
#include <QAbstractSpinBox>
#include <QDialogButtonBox>

#include <QPainter>
#include <QStyleOptionComplex>

void BronzeStyle::polish(QPalette &palette)
{
    QPixmap backgroundImage(":/images/background.png");
    QColor bronze(207, 155, 95);
    QColor veryLightBlue(239, 239, 247);
    QColor lightBlue(223, 223, 239);
    QColor darkBlue(95, 95, 191);

    palette = QPalette(bronze);
    palette.setBrush(QPalette::Window, backgroundImage);
    palette.setBrush(QPalette::BrightText, Qt::white);
    palette.setBrush(QPalette::Base, veryLightBlue);
    palette.setBrush(QPalette::AlternateBase, lightBlue);
    palette.setBrush(QPalette::Highlight, darkBlue);
    palette.setBrush(QPalette::Disabled, QPalette::Highlight,
                     Qt::darkGray);
}

void BronzeStyle::polish(QWidget *widget)
{
    if (qobject_cast<QAbstractButton *>(widget)
            || qobject_cast<QAbstractSpinBox *>(widget)) {
        widget->setAttribute(Qt::WA_Hover, true);
    }
}

void BronzeStyle::unpolish(QWidget *widget)
{
    if (qobject_cast<QAbstractButton *>(widget)
            || qobject_cast<QAbstractSpinBox *>(widget)) {
        widget->setAttribute(Qt::WA_Hover, false);
    }
}

int BronzeStyle::styleHint(QStyle::StyleHint stylehint,
                           const QStyleOption *opt,
                           const QWidget *widget,
                           QStyleHintReturn *returnData) const
{
    switch (stylehint) {
    case SH_DialogButtonLayout:
        return int(QDialogButtonBox::MacLayout);
    case SH_EtchDisabledText:
        return int(true);
    case SH_DialogButtonBox_ButtonsHaveIcons:
        return int(true);
    case SH_UnderlineShortcut:
        return int(false);
    default:
        return QProxyStyle::styleHint(stylehint, opt, widget, returnData);
    }
}

int BronzeStyle::pixelMetric(QStyle::PixelMetric metric,
                             const QStyleOption *option,
                             const QWidget *widget) const
{
    switch (metric) {
    case PM_ButtonDefaultIndicator:
        return 0;
    case PM_IndicatorWidth:
        [[fallthrough]];
    case PM_IndicatorHeight:
        return 16;
    case PM_CheckBoxLabelSpacing:
        return 8;
    case PM_DefaultFrameWidth:
        return 2;
    default:
        return QProxyStyle::pixelMetric(metric, option, widget);
    }
}

void BronzeStyle::drawPrimitive(QStyle::PrimitiveElement pe,
                                const QStyleOption *opt,
                                QPainter *p,
                                const QWidget *w) const
{
    switch (pe) {
    case PE_IndicatorCheckBox:
        drawBronzeCheckBoxIndicator(opt, p);
        break;
    case PE_PanelButtonCommand:
        drawBronzeBevel(opt, p);
        break;
    case PE_Frame:
        drawBronzeFrame(opt, p);
        break;
    case PE_FrameDefaultButton:
        break;
    default:
        QProxyStyle::drawPrimitive(pe, opt, p, w);
    }
}

void BronzeStyle::drawComplexControl(QStyle::ComplexControl cc,
                                     const QStyleOptionComplex *opt,
                                     QPainter *p,
                                     const QWidget *widget) const
{
    if (cc == CC_SpinBox) {
        drawBronzeSpinBoxButton(SC_SpinBoxDown, opt, p);
        drawBronzeSpinBoxButton(SC_SpinBoxUp, opt, p);

        QRect rect = subControlRect(CC_SpinBox, opt,
                                    SC_SpinBoxEditField, widget)
                     .adjusted(-1, 0, +1, 0);
        p->setPen(QPen(opt->palette.mid(), 1.0));
        p->drawLine(rect.topLeft(), rect.bottomLeft());
        p->drawLine(rect.topRight(), rect.bottomRight());
    }
    else {
        return QProxyStyle::drawComplexControl(cc, opt, p, widget);
    }
}

QRect BronzeStyle::subControlRect(QStyle::ComplexControl cc,
                                  const QStyleOptionComplex *opt,
                                  QStyle::SubControl sc,
                                  const QWidget *widget) const
{
    if (cc == CC_SpinBox) {
        int frameWidth = pixelMetric(PM_DefaultFrameWidth, opt, widget);
        int buttonWidth = 16;

        switch (sc) {
        case SC_SpinBoxFrame:
            return opt->rect;
        case SC_SpinBoxEditField:
            return opt->rect.adjusted(+buttonWidth, +frameWidth,
                                         -buttonWidth, -frameWidth);
        case SC_SpinBoxDown:
            return visualRect(opt->direction, opt->rect,
                              QRect(opt->rect.x(), opt->rect.y(),
                                    buttonWidth,
                                    opt->rect.height()));
        case SC_SpinBoxUp:
            return visualRect(opt->direction, opt->rect,
                              QRect(opt->rect.right() - buttonWidth,
                                    opt->rect.y(),
                                    buttonWidth,
                                    opt->rect.height()));
        default:
            return QRect();
        }
    } else {
        return QProxyStyle::subControlRect(cc, opt,
                                             sc, widget);
    }
}

QIcon BronzeStyle::standardIcon(QStyle::StandardPixmap standardIcon,
                                const QStyleOption *option,
                                const QWidget *widget) const
{
    QImage image = QProxyStyle::standardPixmap(standardIcon, option, widget)
                   .toImage();
    if (image.isNull())
        return QIcon();

    QPalette palette;
    if (option) {
        palette = option->palette;
    } else if (widget) {
        palette = widget->palette();
    }

    QPainter painter(&image);
    painter.setOpacity(0.25);
    painter.setCompositionMode(QPainter::CompositionMode_SourceAtop);
    painter.fillRect(image.rect(), palette.highlight());
    painter.end();

    return QIcon(QPixmap::fromImage(image));
}

void BronzeStyle::drawBronzeFrame(const QStyleOption *option,
                                  QPainter *painter) const
{
    painter->save();
    painter->setRenderHint(QPainter::Antialiasing, true);
    painter->setPen(QPen(option->palette.windowText(), 1.0));
    painter->drawRect(option->rect.adjusted(+1, +1, -1, -1));
    painter->restore();
}

void BronzeStyle::drawBronzeBevel(const QStyleOption *option,
                                  QPainter *painter) const
{
    QColor buttonColor = option->palette.button().color();
    int coeff = (option->state & State_MouseOver) ? 115 : 105;

    QLinearGradient gradient(0, 0, 0, option->rect.height());
    gradient.setColorAt(0.0, option->palette.light().color());
    gradient.setColorAt(0.2, buttonColor.lighter(coeff));
    gradient.setColorAt(0.8, buttonColor.darker(coeff));
    gradient.setColorAt(1.0, option->palette.dark().color());

    double penWidth = 1.0;
    if (const QStyleOptionButton *buttonOpt =
            qstyleoption_cast<const QStyleOptionButton *>(option)) {
        if (buttonOpt->features & QStyleOptionButton::DefaultButton) {
            penWidth = 2.0;
        }
    }

    QRect roundRect = option->rect.adjusted(+1, +1, -1, -1);
    if (!roundRect.isValid())
        return;

    int diameter = 12;
    int cx = 100 * diameter / roundRect.width();
    int cy = 100 * diameter / roundRect.height();

    painter->save();
    painter->setPen(Qt::NoPen);
    painter->setBrush(gradient);
    painter->drawRoundedRect(roundRect, cx, cy);

    if (option->state & (State_On | State_Sunken)) {
        QColor slightlyOpaqueBlack(0, 0, 0, 63);
        painter->setBrush(slightlyOpaqueBlack);
        painter->drawRoundedRect(roundRect, cx, cy);
    }

    painter->setRenderHint(QPainter::Antialiasing, true);
    painter->setPen(QPen(option->palette.windowText(), penWidth));
    painter->setBrush(Qt::NoBrush);
    painter->drawRoundedRect(roundRect, cx, cy);
    painter->restore();
}

void BronzeStyle::drawBronzeCheckBoxIndicator(const QStyleOption *option,
                                              QPainter *painter) const
{
    painter->save();
    painter->setRenderHint(QPainter::Antialiasing, true);

    if (option->state & State_MouseOver) {
        painter->setBrush(option->palette.alternateBase());
    }
    else {
        painter->setBrush(option->palette.base());
    }
    painter->drawRoundRect(option->rect.adjusted(+1, +1, -1, -1));

    if (option->state & (State_On | State_NoChange)) {
        QPixmap pixmap;
        if (!(option->state & State_Enabled)) {
            pixmap.load(":/images/checkmark-disabled.png");
        } else if (option->state & State_NoChange) {
            pixmap.load(":/images/checkmark-partial.png");
        } else {
            pixmap.load(":/images/checkmark.png");
        }

        QRect pixmapRect = pixmap.rect()
                                 .translated(option->rect.topLeft())
                                 .translated(+2, -6);
        QRect painterRect = visualRect(option->direction, option->rect,
                                       pixmapRect);
        if (option->direction == Qt::RightToLeft) {
            painter->scale(-1.0, +1.0);
            painterRect.moveLeft(-painterRect.right() - 1);
        }
        painter->drawPixmap(painterRect, pixmap);
    }
    painter->restore();
}

void BronzeStyle::drawBronzeSpinBoxButton(QStyle::SubControl which,
                                          const QStyleOptionComplex *option,
                                          QPainter *painter) const
{
    PrimitiveElement arrow = PE_IndicatorArrowLeft;
    QRect buttonRect = option->rect;
    if ((which == SC_SpinBoxUp)
            != (option->direction == Qt::RightToLeft)) {
        arrow = PE_IndicatorArrowRight;
        buttonRect.translate(buttonRect.width() / 2, 0);
    }
    buttonRect.setWidth((buttonRect.width() + 1) / 2);

    QStyleOption buttonOpt(*option);

    painter->save();
    painter->setClipRect(buttonRect, Qt::IntersectClip);
    if (!(option->activeSubControls & which))
        buttonOpt.state &= ~(State_MouseOver | State_On | State_Sunken);
    drawBronzeBevel(&buttonOpt, painter);

    QStyleOption arrowOpt(buttonOpt);
    arrowOpt.rect = subControlRect(CC_SpinBox, option, which)
                    .adjusted(+3, +3, -3, -3);
    if (arrowOpt.rect.isValid())
        drawPrimitive(arrow, &arrowOpt, painter);
    painter->restore();
}

When i try to compile this i i get this output:

19:05:23: Running steps for project bronzestyleplugin...
19:05:23: Configuration unchanged, skipping qmake step.
19:05:23: Starting: "/usr/bin/make" -j4
Makefile:975: warning: overriding recipe for target 'moc_bronzestyleplugin.cpp'
Makefile:904: warning: ignoring old recipe for target 'moc_bronzestyleplugin.cpp'
Makefile:1321: warning: overriding recipe for target 'bronzestyleplugin.o'
Makefile:1222: warning: ignoring old recipe for target 'bronzestyleplugin.o'
/home/sandro/Qt/5.13.0/gcc_64/bin/qmake -o Makefile ../bronzestyleplugin/bronzestyleplugin.pro -spec linux-g++ CONFIG+=qtquickcompiler
Makefile:978: warning: overriding recipe for target 'moc_bronzestyleplugin.cpp'
Makefile:907: warning: ignoring old recipe for target 'moc_bronzestyleplugin.cpp'
Makefile:1324: warning: overriding recipe for target 'bronzestyleplugin.o'
Makefile:1225: warning: ignoring old recipe for target 'bronzestyleplugin.o'
g++ -c -pipe -O2 -std=gnu++1z -Wall -W -D_REENTRANT -fPIC -DQT_NO_DEBUG -DQT_PLUGIN -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../bronzestyleplugin -I. -I/home/sandro/Qt/5.13.0/gcc_64/include -I/home/sandro/Qt/5.13.0/gcc_64/include/QtWidgets -I/home/sandro/Qt/5.13.0/gcc_64/include/QtGui -I/home/sandro/Qt/5.13.0/gcc_64/include/QtCore -I. -isystem /usr/include/libdrm -I/home/sandro/Qt/5.13.0/gcc_64/mkspecs/linux-g++ -o bronzestyle.o ../../bronze/bronze/bronzestyle.cpp
g++ -c -pipe -O2 -std=gnu++1z -Wall -W -D_REENTRANT -fPIC -DQT_NO_DEBUG -DQT_PLUGIN -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../bronzestyleplugin -I. -I/home/sandro/Qt/5.13.0/gcc_64/include -I/home/sandro/Qt/5.13.0/gcc_64/include/QtWidgets -I/home/sandro/Qt/5.13.0/gcc_64/include/QtGui -I/home/sandro/Qt/5.13.0/gcc_64/include/QtCore -I. -isystem /usr/include/libdrm -I/home/sandro/Qt/5.13.0/gcc_64/mkspecs/linux-g++ -o bronzestyleplugin.o ../bronzestyleplugin/bronzestyleplugin.cpp
/home/sandro/Qt/5.13.0/gcc_64/bin/moc -DQT_NO_DEBUG -DQT_PLUGIN -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB --include /mnt/Programmierung/Cpp/QT/C++_GUI_Programming_with_Qt/CH21_creating_plugins/bronzestyleplugin/build-bronzestyleplugin-Desktop_Qt_5_13_0_GCC_64bit-Release/moc_predefs.h -I/home/sandro/Qt/5.13.0/gcc_64/mkspecs/linux-g++ -I/mnt/Programmierung/Cpp/QT/C++_GUI_Programming_with_Qt/CH21_creating_plugins/bronzestyleplugin/bronzestyleplugin -I/home/sandro/Qt/5.13.0/gcc_64/include -I/home/sandro/Qt/5.13.0/gcc_64/include/QtWidgets -I/home/sandro/Qt/5.13.0/gcc_64/include/QtGui -I/home/sandro/Qt/5.13.0/gcc_64/include/QtCore -I. -I/usr/include/c++/7 -I/usr/include/x86_64-linux-gnu/c++/7 -I/usr/include/c++/7/backward -I/usr/lib/gcc/x86_64-linux-gnu/7/include -I/usr/local/include -I/usr/lib/gcc/x86_64-linux-gnu/7/include-fixed -I/usr/include/x86_64-linux-gnu -I/usr/include ../../bronze/bronze/bronzestyle.h -o moc_bronzestyle.cpp
g++ -c -pipe -O2 -std=gnu++1z -Wall -W -D_REENTRANT -fPIC -DQT_NO_DEBUG -DQT_PLUGIN -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../bronzestyleplugin -I. -I/home/sandro/Qt/5.13.0/gcc_64/include -I/home/sandro/Qt/5.13.0/gcc_64/include/QtWidgets -I/home/sandro/Qt/5.13.0/gcc_64/include/QtGui -I/home/sandro/Qt/5.13.0/gcc_64/include/QtCore -I. -isystem /usr/include/libdrm -I/home/sandro/Qt/5.13.0/gcc_64/mkspecs/linux-g++ -o moc_bronzestyle.o moc_bronzestyle.cpp
../../bronze/bronze/bronzestyle.cpp: In member function ‘void BronzeStyle::drawBronzeCheckBoxIndicator(const QStyleOption*, QPainter*) const’:
../../bronze/bronze/bronzestyle.cpp:254:65: warning: ‘void QPainter::drawRoundRect(const QRect&, int, int)’ is deprecated: Use drawRoundedRect(..., Qt::RelativeSize) instead [-Wdeprecated-declarations]
     painter->drawRoundRect(option->rect.adjusted(+1, +1, -1, -1));
                                                                 ^
In file included from /home/sandro/Qt/5.13.0/gcc_64/include/QtGui/QPainter:1:0,
                 from ../../bronze/bronze/bronzestyle.cpp:7:
/home/sandro/Qt/5.13.0/gcc_64/include/QtGui/qpainter.h:379:10: note: declared here
     void drawRoundRect(const QRect &r, int xround = 25, int yround = 25);
          ^~~~~~~~~~~~~
rm -f libbronzestyleplugin.so
g++ -Wl,-O1 -Wl,-rpath,/home/sandro/Qt/5.13.0/gcc_64/lib -shared -o libbronzestyleplugin.so bronzestyle.o bronzestyleplugin.o bronzestyleplugin.o qrc_bronze.o moc_bronzestyle.o moc_bronzestyleplugin.o  /home/sandro/Qt/5.13.0/gcc_64/lib/libQt5Widgets.so /home/sandro/Qt/5.13.0/gcc_64/lib/libQt5Gui.so /home/sandro/Qt/5.13.0/gcc_64/lib/libQt5Core.so -lGL -lpthread    
bronzestyleplugin.o: In function `BronzeStylePlugin::create(QString const&)':
bronzestyleplugin.cpp:(.text+0x0): multiple definition of `BronzeStylePlugin::create(QString const&)'
bronzestyleplugin.o:bronzestyleplugin.cpp:(.Makefile:277: recipe for target 'libbronzestyleplugin.so' failed
text+0x0): first defined here
collect2: error: ld returned 1 exit status
make: *** [libbronzestyleplugin.so] Error 1
19:05:25: The process "/usr/bin/make" exited with code 2.
Error while building/deploying project bronzestyleplugin (kit: Desktop Qt 5.13.0 GCC 64bit)
When executing step "Make"
19:05:25: Elapsed time: 00:02.

Any idea how to find the issue here?

[SGaist]

Hi,

How many create method do you have ?

[Christian Ehrlicher]

@sandro4912 said in Creating Style Plugin in QT5:

SOURCES = ../../bronze/bronze/bronzestyle.cpp
bronzestyleplugin.cpp
bronzestyleplugin.cpp

You add your sources (and also headers) twice.

[sandro4912]

@Christian-Ehrlicher

removing the double declaration fixed the issue. I could compile the style addon.

However i don't see that the styles plugin gets deployed. I only get:

18:15:49: Running steps for project bronzestyleplugin...
18:15:49: Configuration unchanged, skipping qmake step.
18:15:49: Starting: "/usr/bin/make" -j4
/home/sandro/Qt/5.13.0/gcc_64/bin/qmake -o Makefile ../bronzestyleplugin/bronzestyleplugin.pro -spec linux-g++ CONFIG+=qtquickcompiler
make: Nothing to be done for 'first'.
18:15:50: The process "/usr/bin/make" exited normally.
18:15:50: Elapsed time: 00:01.

To have it available from qt creator do i have to ?

[Christian Ehrlicher]

'make' just compiles a library, 'make install' installs it. But since you did not define an install target there won't be done anything. You have to copy it to the correct folder by yourself.

[sandro4912]

I thought i defined it with

TARGET = $$qtLibraryTarget($$TARGET)

target.path = $$[QT_INSTALL_PLUGINS]/styles
INSTALLS += target

what do i need to add to automatically copy it to the correct folder?

[Christian Ehrlicher]

So did you actually do a 'make install' ?

[sandro4912]

what do you mean with that?

[Christian Ehrlicher]

Just because you define an install target nothing happens - you have to call make with the parameter 'install' as I said above.