I would like to do certain updates when the text contents change or font or alignment change on QGraphicsTextItem.
So I connected QTextDocument::contentsChanged() to a slot that does the update.
This signal is emitted whenever the document's content changes; for
example, when text is inserted or deleted, or when formatting is
applied.
The signal gets hit when I change the text - but setting text formatting or alignment doesn't seem to affect it.
.h
class MyTextItem : public QGraphicsTextItem
{
Q_OBJECT
public:
MyTextItem();
~MyTextItem() {}
void setItemFont(QFont f);
void setItemAlign(Qt::Alignment a);
private slots:
void updateItemOnContentsChanged();
private:
void updateTextOnPropertyChanges();
};
.cpp
MyTextItem::MyTextItem()
{
setTextInteractionFlags(Qt::TextEditorInteraction);
connect(document(), SIGNAL(contentsChanged()), this, SLOT(updateItemOnContentsChanged()));
}
void MyTextItem::setItemFont(QFont f)
{
setFont(f);
}
void MyTextItem::setItemAlign(Qt::Alignment a)
{
QTextDocument *_document = document();
QTextOption _option = _document->defaultTextOption();
_option.setAlignment(a);
_document->setDefaultTextOption(_option);
setDocument(_document);
}
void MyTextItem::updateItemOnContentsChanged()
{
updateTextOnPropertyChanges();
}
void MyTextItem::updateTextOnPropertyChanges()
{
qDebug("changing something");
}
main.cpp
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QGraphicsScene s;
QGraphicsView view(&s);
s.setSceneRect(-50, -50, 500, 500);
view.show();
MyTextItem* t = new MyTextItem();
t->setPlainText("Hello World !"); // Note this triggers update
s.addItem(t);
qDebug("1");
qDebug() << t->font().family();
t->setItemFont(QFont("Arial")); // or t->setFont(QFont("Arial"));
qDebug() << t->font().family();
qDebug("2");
t->setItemAlign(Qt::AlignRight);
qDebug("3");
return app.exec();
}
My debug output:
changing something
1
"MS Shell Dlg 2" // so the font is changing - yet no signal
"Arial"
2
3
(and if I type in the item on the scene I get changing something as well)
But no changing something after the setItemFont() or setItemAlign().
So changing text affects it - but changing font or alignment doesn't...
Do I understand wrong the part I set bold in the signal description ?
Why do I not see changing something after changing font or alignment...
I also wonder - does my changing the document() when I set alignment or wrap or other document properties affect the connect ? (it doesn't seem to...)
(Note I wrote the setItem* functions to be able to call the updateTextOnPropertyChanges() function - so I can make things work the way I need - but would be great if I didn't need them and just use the Qt ones, if the signal worked as I thought it would)
It seems that what falls under formatting is loosely defined.
As you said, setItemFont() or setItemAlign() do not trigger the signal, but calling _document->setDocumentMargin(4.3); within your void MyTextItem::setItemAlign(Qt::Alignment a) method does.
Also, contentsChanged() is a signal emitted by the QTextDocument class, so I'm not sure if calling methods on the QGraphicsTextItem object that change its appearance classifies as modifying the formatting of the QTextDocument.
Related
Essentially I want to trigger some code after the my QFileDiag has 1 or more files selected and is accepted ("open" button clicked), the problem is that I can't seem to actually trigger my code in the slot.
Here is the code in my main widget
file_select_diag = new QFileDiag(this)
connect(file_select_diag, &QFileDialog::fileSelected, this,
&MainWidget::connect_test);
auto files = file_select_diag->getOpenFileName(
this,
tr("test"),
QDir::homePath(),
tr("text (*.txt)");
void MainWidget::connect_test(QString str)
{
cout << str.toStdString();
}
And here is the header declaration
{
Q_OBJECT
public:
explicit MainWidget(QWidget *parent = 0); //Constructor
~MainWidget(); // Destructor
private slots:
void connect_test(QString str);
void connect_test2(); //like above but cout << "HIT" << end;
private:
QFileDialog *file_select_diag;
I've tried connecting to both connect_test and connect_test2, when I run my app and select files, hit open, nothing happens.
Solution (copied from G.M.'s comment below)
Note that QFileDialog::getOpenFileName is a static member of
QFileDialog so the call file_select_diag->getOpenFileName(...)
effectively creates a QFileDialog instance independent of
file_select_diagand calls getOpenFileName against that.
So effectively the two approaches here are either go entirely with the static method getOpenFileName and do not initialize file_select_diag or go entirely for the instance approach, configure the file_select_diag then use file_select_diag->show(), in which case the signal will work.
I am developing a Qt application with multiple windows and want to implement cross-window drag&drop functionality for some elements in my program.
To do so, I attach an event filter to the to-be-dragged QML elements and listen for the MousePress/MouseMove events to start the drag procedure as follows:
QDrag *drag = new QDrag(quickItem);
QMimeData* mimeData = new QMimeData();
mimeData->setText("Test");
drag->setHotSpot(QPoint(0, 0));
drag->setMimeData(mimeData);
drag->exec();
This works fine, but now I would like to show a little tooltip (being a QWidget) while dragging, following the mouse cursor and displaying a short text depending on the element the mouse is currently over (similar to the "Copy to ..." or "Move to..." labels appearing when you drag files around in Windows Explorer).
However, while dragging the element, I don't receive any MouseMove events neither on the QDrag object nor on the quickItem itself, which makes it impossible to track the mouse position. Since the mouse is grabbed during dragging, there should be some event in Qt that frequently reports the mouse position, no matter where on the screen the mouse is.
I am aware of the QDrag::setPixmap method, however this won't allow me to change my tooltip text during dragging and has some other limitations I would like to avoid.
Is there some way to listen to mouse move events while QDrag is running, without using platform-specific system APIs?
Update:
I don't think that there is way of doing this without using OS libraries nor getting the mouse position every X miliseconds. It looks like a really specific problem that Qt framework does not contemplate. You will need to write your own class to control this using win32 for windows, x11 for linux and the equivalent of Mac.
If you want to get the mouse position when your window is active and you are dragging something, check this:
Searching a bit I've found a solution for getting it when your window has the focus using QObject::eventFilter.
Create a class (for example EventListener) that inherits from QObject and overrides eventFilter and a method to set this as your qml window (which inherits from QObject) event filter with installEventFilter.
eventslistener.h:
#include <QEvent>
#include <QObject>
#include <QDebug>
#include <QDropEvent>
class EventsListener : public QObject
{
Q_OBJECT
public:
EventsListener(QObject * ptr) : QObject (ptr) {
}
Q_INVOKABLE void handleEventsOf(QObject *object) {
if (object)
object->installEventFilter(this);
}
bool eventFilter(QObject *object, QEvent *event) override {
if(event->type() == QEvent::DragMove) {
QDragMoveEvent *mouseEvent = static_cast<QDragMoveEvent*>(event);
qDebug() << "Mouse position dragging (x, y): (" << mouseEvent->pos().x() << ", " << mouseEvent->pos().y() << ")";
return false; //this is must return false or drop event will be handled by this method and drag&drop won't work correctly
}
return false;
}
};
Now we need to access to an instance (singleton in this case) of this class with qmlRegisterSingletonType. You may wish to use qmlRegisterType instead to register this eventlistener as a type (instead of a singleton) and use signals to notify directly qml the mouse position.
main.cpp:
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include "eventlistener.h"
static QObject *eventsListenerInstance(QQmlEngine *qmlEngine, QJSEngine *engine)
{
return new EventsListener(engine);
}
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
qmlRegisterSingletonType<EventsListener>("AppEventListener", 1, 0, "EventsListener", eventsListenerInstance);
QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
return -1;
return app.exec();
}
main.qml:
import ...
import AppEventListener 1.0
ApplicationWindow {
visible: true
width: 640
height: 480
id: item
property string display
property alias dropEnabled: acceptDropCB.checked
color: dropArea.containsDrag ? "#CFC" : "#EEE"
Component.onCompleted: EventsListener.handleEventsOf(item)
...
}
i'm using QT for the first time and got some problems with refreshing the GUI while adding elements.
The Code looks like:
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
PObj obj;
MainWindow mw;
qRegisterMetaType<std::string>();
QObject::connect(&obj, SIGNAL(setText(std::string const&)),
&mw, SLOT(appendText(std::string const&)));
QFuture<void> f1 = QtConcurrent::run(&obj, &PObj::process);
mw.show();
f1.waitForFinished();
return a.exec();
}
With the PObj::process definition:
void PObj::process()
{
for(; ;)
{
sleep(1);
//do work and set text
std::string text = "bla";
emit setText( text );
}
}
And the MainWindow::appendText slot:
void MainWindow::appendText(std::string const& str )
{
ui->listWidget->addItem(QString::fromStdString(str));
}
I've tried placing qApp->processEvents() ,QCoreApplication::processEvents(); ... running wit future in the ThreadPool.
I thought running them with Concurrent::run is enough ?
UPDATE:
The question is, why the GUI isnt refreshed every second a new item is added ?
The f1.waitForFinished(); calls blocks until f1 is finished, as the name implies. This will never happen because you have the infinite loop. So your code will never get to main loop. You can't block the main thread like that! In general, avoid any WaitForXxxx() methods, especially the GUI thread.
Also, you have no way of stopping the process(); anyway, so waiting for it to finish doesn't make any sense... You might want to add a way to tell it to stop (such as atomic variable) but anyway, to fix your problem, simply remove the f1.waitForFinished(); line.
To terminate the task nicely, try adding QAtomicInt flag (not volatile boolean, it won't do), and then change the code like this:
Add member variable to PObj (should make it private and add setter):
QAtomicInt termianteFlag;
Change main like this:
int main(int argc, char *argv[])
{
///snip
QFuture<void> f1 = QtConcurrent::run(&obj, &PObj::process);
mw.show();
int ret = a.exec();
f1.terminateFlag = 1; // change this to setter method
f1.waitForFinished(); // this is not ideal, will wait for up to a second before exit
}
and
void PObj::process()
{
while(!terminateFlag)
{
sleep(1);
//do work and set text
std::string text = "bla";
emit setText( text );
}
}
I'm working with Qt (v 5.3) again after sometime away. As a learning exercise I am prototyping a module using QGraphicView in order to understand better how to use it.
The functionality is simple: I have several QGraphicObjects which function like buttons with states and behaviors:
OFF - image panel hidden; default button art
ON - image panel
displayed; highlight button art
At startup all buttons are in an OFF state
A clicked button will toggle it's state (non-Exclusive)
If a different button is already in an ON state, it must be turned off (Exclusive)
Everything is data driven and created dynamically at runtime.
So that is my little learning exercise. What I am trying to sort out is an efficient messaging mechanism to handle the "radio button sometimes" exclusive behavior and sending a message to a group of objects without strongly coupling them.
I've looked at signals and slots but that gets tedious if there are many connections to make.
QSignalMapper which seems somewhat better
QEvent is probably the most solid approach but I've had trouble finding good learning examples.
I am making this more complicated than need be but as I say, it's a learning exercise to get used to Qt again.
So my question (finally): is there an approach I am overlooking or one of these mentioned which would be better (e.g most flexible, maintainable, scalable). Not looking for code per se, but an understanding of how to go about coding something like this using the Qt framework.
Here's an image of the thing:
Signal and slots is the method I would use here. However, rather than connect each button to every other button, you can create an intermediate, Controller class.
The Controller class can either aggregate, or be a parent to all of the buttons.
When a button is created, it connects signals to the controller to inform it of being pressed. The receiving slot in the Controller class is then responsible for turning off any other buttons.
Skeleton code: -
class ButtonController : public QGraphicsObject
{
public slots:
void ButtonPressed();
private:
QList<MyButton*> m_buttonList;
};
void ButtonController::ButtonPressed()
{
foreach(MyButton* pButton, m_buttonList)
{
if(pButton != sender())
{
pButton->Off();
}
}
}
In the constructor of MyButton, assuming the controller is the parent: -
MyButton::MyButton(ButtonController* parent)
: QGraphicsObject(parent);
{
connect(this, &MyButton::pressed(), parent, &ButtonController::ButtonPressed());
...
}
Alternatively, the controller may just hold a list of the buttons, in which case you can do this: -
MyButton::MyButton(QObject* parent, ButtonController* pButtonController)
: QGraphicsObject(parent);
{
connect(this, &MyButton::pressed(), pButtonController, &ButtonController::ButtonPressed());
...
}
In the case of not being able to change the constructor of the buttons, the controller may simply have an AddButton function, in which it creates the connection when the button is added under its control.
Subclass QGraphicsScene
Reimplement mousePressEvent and check is left mouse button pressed.
If so, then get position of mouse by pos() method and get current graphics object under arrow by itemAt() method.
Try to cast it into your needed object, if it was successfully, then change background and other.
Store your graphics objects in vector, in this case you can check every object and decide which object should be turned off.
Fully working example:
header:
#ifndef GRAPHICSSCENE_H
#define GRAPHICSSCENE_H
#include <QGraphicsScene>
#include <QPoint>
#include <QMouseEvent>
class GraphicsScene : public QGraphicsScene
{
Q_OBJECT
public:
explicit GraphicsScene(QObject *parent = 0);
signals:
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent);
public slots:
private:
QVector<QGraphicsEllipseItem * > vec;
};
#endif // GRAPHICSSCENE_H
cpp:
#include "graphicsscene.h"
#include <QDebug>
#include <QGraphicsSceneMouseEvent>
#include <QGraphicsItem>
GraphicsScene::GraphicsScene(QObject *parent) :
QGraphicsScene(parent)
{
//set circles in different positions.
vec.push_back(addEllipse(0,0,50,50,QPen(Qt::red),QBrush(Qt::blue)));
vec.push_back(addEllipse(0+100,0+100,50,50,QPen(Qt::red),QBrush(Qt::blue)));
vec.push_back(addEllipse(0+150,0+150,50,50,QPen(Qt::red),QBrush(Qt::blue)));
}
void GraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
//qDebug() << "in";
if (mouseEvent->button() == Qt::LeftButton)
{
QGraphicsItem *item = itemAt(mouseEvent->scenePos(), QTransform());
QGraphicsEllipseItem *ell = qgraphicsitem_cast<QGraphicsEllipseItem *>(item);
if(ell)
{
for(int i = 0; i < vec.size(); i++)
{
if(vec.at(i) != ell)
{
vec.at(i)->setBrush(QBrush(Qt::blue));//disable all other bettons
}
}
ell->setBrush(QBrush(Qt::black));//to chosen circle
qDebug() << "good";
}
else
qDebug() << "not ell" << mouseEvent->scenePos();
}
}
Usage:
GraphicsScene *scene = new GraphicsScene(this);
ui->graphicsView->setScene(scene);
With this case, your circles will be similar to radioButtons. If you want save state of all buttons you can use:
for(int i = 0; i < vec.size(); i++)
vec.at(i)->setData(0,false);
And get state with
if(!ell->data(0).toBool())
//do
This was my original question:
I just want to take a screenshot (using the Print key) of my fullscreen QtQuick 2 application. But all I get is a black or sometimes white screenshot. When the application is not started in fullscreen it works.
SOLUTION
I thought I post a really nice solution here,
even though it does not solve the original problem of taking the screenshot with an external tool.
Starting with the suggestion from the accepted answer I did the following:
First I added a signal to my QML main class (in main.qml)
signal takeScreenShot()
This signal is emmited by pressing a certain button.
Then I wrote a C++ / QT class autside the QML code to handle this signal:
class QMLSupplement : public QObject
{
Q_OBJECT
public:
QQuickView* view;
public:
QMLSupplement(QObject* parent = 0);
public slots:
void takeScreenShot();
};
The reference to QQuickView is used to take the screenshot.
void QMLSupplement::takeScreenShot()
{
QString file;
file = QDateTime::currentDateTime().toString("yyyy-MM-dd_hhmmss");
file += ".png";
qDebug() << "taking screenshot, saving here:" << file;
view->grabWindow().save(file);
}
Finally I connect the signal and the slot in main.cpp:
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QQuickView view;
view.setSource(QUrl::fromLocalFile("./qml/main.qml"));
view.setResizeMode(QQuickView::SizeRootObjectToView);
QObject* rootObject = (QObject*) view.rootObject();
QMLSupplement supplement;
supplement.view = &view;
QObject::connect(rootObject, SIGNAL(takeScreenShot()),
&supplement, SLOT(takeScreenShot()));
view.show();
// view.showFullScreen();
return app.exec();
}
That's a limitation of the platform where you're running. If you care about this working, you need to implement the functionality yourself. Qt provides you with enough to get the contents of the Qt Quick 2 window and post it to the clipboard as an image.
In your print key handler, if you detect that the window is full-screen, you need to pass the QQuickWindow instance to a helper function:
void grabAndCopy(QQuickWindow * window) {
QApplication::clipboard()->setImage(window->grabWindow());
}
...
if (window->windowState() == Qt::WindowFullScreen) grabAndCopy(window);