custom gfx text item

CMakeLists.txt

cmake_minimum_required(VERSION 3.10)
project(examples LANGUAGES CXX)

set(CMAKE_CXX_STANDART 14)
set(CMAKE_CXX_STANDART_REQUIRED ON)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_AUTOMOC ON)

set(CMAKE_INCLUDE_CURRENT_DIR ON)

find_package(Qt5 COMPONENTS Widgets REQUIRED)

add_executable(gfxext WIN32)

target_sources(gfxext
    PRIVATE
        gfx_main.cxx
        gfxtextitem.cxx gfxtextitem.hxx
)

target_link_libraries(gfxext PRIVATE Qt5::Widgets)

gfx_main.cxx

#include <QtWidgets>

#include "gfxtextitem.hxx"

void build_ui(QWidget& view)
{
    auto box = new QVBoxLayout;
    auto gc = new QGraphicsScene{&view};
    auto gfx = new QGraphicsView{gc};
    auto txt = new QPlainTextEdit{};
    auto btn = new QPushButton("Add text");
    gfx->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::MinimumExpanding);
    txt->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Maximum);

    QObject::connect(btn, &QPushButton::clicked, [gc, txt](){
        auto item = new GfxTextItem;
        item->text = txt->toPlainText();
        bool ok;
        auto font = QFontDialog::getFont(&ok);
        if (ok) {
            item->font = font;
        }
        gc->addItem(item);
    });

    box->addWidget(gfx);
    box->addWidget(txt);
    box->addWidget(btn);

    view.setLayout(box);
    view.resize(600, 600);
}

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

    QWidget view;

    build_ui(view);
    view.show();

    return app.exec();
}

gfxtextitem.cxx

#include "gfxtextitem.hxx"

GfxTextItem::GfxTextItem(QGraphicsItem* parent)
    : QGraphicsItem(parent)
{
    auto half = size / 2.0;
    rect.setRect(-half, -half, size, size);
    font.setFamily("Monospace");
    font.setPointSize(10);

    setFlag(ItemIsMovable, true);
}

GfxTextItem::~GfxTextItem() = default;


QRectF GfxTextItem::boundingRect() const
{
    return rect;
}

QPainterPath GfxTextItem::shape() const
{
    QPainterPath p;
    p.addRect(rect);
    return p;
}

void GfxTextItem::paint(QPainter *painter, const QStyleOptionGraphicsItem */*option*/, QWidget */*widget*/)
{
    painter->save();

    painter->setRenderHint(QPainter::Antialiasing, true);
    painter->setRenderHint(QPainter::TextAntialiasing, true);
    painter->setFont(font);
    painter->drawRect(rect);
    painter->drawText(rect, Qt::AlignCenter | Qt::TextSingleLine, text);

    painter->restore();
}

gfxtextitem.hxx

#pragma once

#include <QGraphicsItem>

#include <QtCore>
#include <QtGui>

class GfxTextItem: public QGraphicsItem
{
public:
    explicit GfxTextItem(QGraphicsItem* parent = nullptr);
    ~GfxTextItem() override;

    // QGraphicsItem interface
public:
    QRectF boundingRect() const override;
    QPainterPath shape() const override;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;

    QRectF rect;
    QFont font;
    QString text;

    double size = 100.0;
};