(C++) QtExample25

 

 

Qt example 25: a transparent widget shows a transparent sketch widget.

Technical facts

 

Application type(s)

• Desktop application

Operating system(s) or programming environment(s)

• Lubuntu 15.04 (vivid)

IDE(s):

• Qt Creator 3.1.1

Project type:

• GUI application

C++ standard:

• C++11

Compiler(s):

• G++ 4.9.2

Libraries used:

• Qt: version 5.4.1 (32 bit)
• STL: GNU ISO C++ Library, version 4.9.2

 

 

 

 

 

Qt project file: ./CppQtExample25/CppQtExample25.pro

 

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exists(../../DesktopApplication.pri) {   include(../../DesktopApplication.pri) } !exists(../../DesktopApplication.pri) {   QT += core gui   greaterThan(QT_MAJOR_VERSION, 4): QT += widgets   TEMPLATE = app   CONFIG(debug, debug|release) {     message(Debug mode)   }   CONFIG(release, debug|release) {     message(Release mode)     DEFINES += NDEBUG NTRACE_BILDERBIKKEL   }   QMAKE_CXXFLAGS += -std=c++11 -Wall -Wextra   unix {     QMAKE_CXXFLAGS += -Werror   } } exists(../../Libraries/Boost.pri) {   include(../../Libraries/Boost.pri) } !exists(../../Libraries/Boost.pri) {   win32 {     INCLUDEPATH += \       ../../../Projects/Libraries/boost_1_55_0   } } SOURCES += \   main.cpp \   sketchwidget.cpp \   transparentsketchdialog.cpp HEADERS  += \   sketchwidget.h \   transparentsketchdialog.h FORMS    += \   transparentsketchdialog.ui #CONFIG += mobility #MOBILITY = #symbian { #    TARGET.UID3 = 0xeaa0000d #    # TARGET.CAPABILITY += #    TARGET.EPOCSTACKSIZE = 0x14000 #    TARGET.EPOCHEAPSIZE = 0x020000 0x800000 #}

 

 

 

 

 

./CppQtExample25/main.cpp

 

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#pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QApplication> #include "transparentsketchdialog.h" #pragma GCC diagnostic pop int main(int argc, char *argv[]) {   QApplication a(argc, argv);   TransparentSketchDialog w;   w.show();   return a.exec(); }

 

 

 

 

 

./CppQtExample25/sketchwidget.h

 

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#ifndef SKETCHWIDGET_H #define SKETCHWIDGET_H #include <vector> #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QWidget> #pragma GCC diagnostic pop class SketchWidget : public QWidget {   Q_OBJECT public:   explicit SketchWidget(QWidget *parent = 0);   void clear();   virtual ~SketchWidget() {} protected:   virtual void mouseMoveEvent(QMouseEvent *);   virtual void mousePressEvent(QMouseEvent *);   virtual void paintEvent(QPaintEvent *); private:   std::vector<std::vector<QPoint> > m_points; signals: public slots: }; #endif // SKETCHWIDGET_H

 

 

 

 

 

./CppQtExample25/sketchwidget.cpp

 

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#include "sketchwidget.h" #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <cassert> #include <QMouseEvent> #include <QPainter> #pragma GCC diagnostic pop SketchWidget::SketchWidget(QWidget *parent)   : QWidget(parent),     m_points{} {   this->setMouseTracking(true); } void SketchWidget::clear() {   m_points.clear();   this->repaint(); } void SketchWidget::mouseMoveEvent(QMouseEvent * e) {   if (e->buttons() & Qt::LeftButton)   {     m_points.back().push_back(e->pos());     this->repaint();   } } void SketchWidget::mousePressEvent(QMouseEvent * e) {   if (e->buttons() & Qt::LeftButton)   {     m_points.push_back(std::vector<QPoint>());     m_points.back().push_back(e->pos());   } } void SketchWidget::paintEvent(QPaintEvent *) {   QPainter painter(this);   {     QPen pen = painter.pen();     pen.setCapStyle(Qt::RoundCap);     pen.setWidth(10);     painter.setPen(pen);   }   const int n_lines = static_cast<int>(m_points.size());   for (int line=0; line!=n_lines; ++line)   {     const std::vector<QPoint>& points = m_points[line];     const int n_points = static_cast<int>(points.size());     for (int point=1; point!=n_points; ++point)     {       painter.drawLine(points[point-1],points[point]);     }   } }

 

 

 

 

 

./CppQtExample25/transparentsketchdialog.h

 

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#ifndef TRANSPARENTSKETCHDIALOG_H #define TRANSPARENTSKETCHDIALOG_H #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QDialog> #pragma GCC diagnostic pop namespace Ui {   class TransparentSketchDialog; } class TransparentSketchDialog : public QDialog {   Q_OBJECT public:   explicit TransparentSketchDialog(QWidget *parent = 0);   TransparentSketchDialog(const TransparentSketchDialog&) = delete;   TransparentSketchDialog& operator=(const TransparentSketchDialog&) = delete;   ~TransparentSketchDialog(); protected:   void paintEvent(QPaintEvent *); private:   Ui::TransparentSketchDialog *ui;   QPixmap m_pixmap; }; #endif // TRANSPARENTSKETCHDIALOG_H

 

 

 

 

 

./CppQtExample25/transparentsketchdialog.cpp

 

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#pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QDesktopWidget> #include <QPainter> #include <QPixmap> #include "transparentsketchdialog.h" #include "ui_transparentsketchdialog.h" #pragma GCC diagnostic pop TransparentSketchDialog::TransparentSketchDialog(QWidget *parent)   : QDialog(parent),     ui(new Ui::TransparentSketchDialog),     m_pixmap(QPixmap::grabWindow(QApplication::desktop()->winId())) {   ui->setupUi(this); } TransparentSketchDialog::~TransparentSketchDialog() {   delete ui; } void TransparentSketchDialog::paintEvent(QPaintEvent *) {   QPainter painter(this);   painter.drawPixmap(     this->rect(),     m_pixmap,     this->geometry()   ); }