Qt: How to make translucent, windowless, chromeless window draggable? - c++

Question

I have a window based on a semitransparent image:
import QtQuick 1.1
import QtWebKit 1.1
Image {
source: "qrc:/assets/bg.png"
}
And something like this in main window
#include "mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent)
{
setAttribute(Qt::WA_TranslucentBackground);
setStyleSheet("background:transparent;");
/* turn off window decorations */
setWindowFlags(Qt::FramelessWindowHint);
ui = new QDeclarativeView;
ui->setSource(QUrl("qrc:/assets/ui.qml"));\
setCentralWidget(ui);
}
MainWindow::~MainWindow()
{
delete ui;
}
and
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QtDeclarative/QDeclarativeView>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
QDeclarativeView *ui;
};
#endif // MAINWINDOW_H
I wonder how to make my window draggable across the screen (user presses on an image and drugs window around..)?

Answer 1

Reimplement mousePressEvent() and mouseReleaseEvent() to know when the user is holding the mouse down, then reimplement mouseMoveEvent() and if the user is holding the mouse down, move the widget.
// **Untested code**
protected:
virtual void mousePressEvent(QMouseEvent *event) { _mouseIsDown = true; }
virtual void mouseReleaseEvent(QMouseEvent *event) { _mouseIsDown = false; }
virtual void mouseMoveEvent(QMouseEvent *event) { if(_mouseIsDown) { move(event->pos() + globalPos()); } }

Answer 2

#include <QMouseEvent>
#include <Qpoint>
class MainWindow : public QMainWindow{
...
void mousePressEvent(QMouseEvent *event);
void mouseMoveEvent(QMouseEvent *event);
QPoint LastPoint;
QPoint LastTopLeft;
void mousePressEvent(QMouseEvent *event)
{
if (event->button() == Qt::LeftButton) {
QPoint Point=event->globalPos();
LastTopLeft=this->frameGeometry().topLeft();
LastPoint=Point;
}
}
void mouseMoveEvent(QMouseEvent *event)
{
if ((event->buttons() & Qt::LeftButton)) {
const QPoint Point=event->globalPos();
QPoint offset=Point-LastPoint;
this->move(LastTopLeft+offset);
}
}
...
}

Answer 3

It worked for me after I removed the first two declarations.