I have do some research about QMouseEvents but I am stuck about passing a QMouseEvent to child widgets. I have a program with a structure like this :
MainWindow > DockWidget > WidgetList > WidgetTarget
MainWindow is parent of DockWidget etc... My primary goal is to know when I clicked in MainWindow and pass this QMouseEvent to WidgetTarget.
I read the doc about QMouseEvent and see the useful functions ignore() of QEvent but it does the contrary of what I want. The QMouseEvent is passed to the parent, so If I clik in WidgetTarget, the QMousseEvent will be pass to WidgetList.
So is there a way to pass a QMousseEvent to a child widget instead of its parent widget ?
I have see some trick with the flag Qt::WA_TransparentForMouseEvents but I don't know if this is a correct way
EDIT :
I will put some detail about the work in WidgetTarget with mousePressEvent(QMouseEvent *event). It basicaly to make a eyedropper. Here the code I have in mind :
void WidgetTarget::mousePressEvent(QMouseEvent *event)
{
if(eyeDropperActivated) //true when clicked on button eyedropper
{
QLabel *label = (QLabel*)MainWindow->childAt(event->x(),event->y());
QColor color; //Get the pixel value at x,y event from the QLabel pixmap
setColor(color) //Set the color parameter of WidgetTarget
}
}
I read your useful comments and yes I think It will be easy If I implement this code on MainWindow, but the eyedropper function is in WidgetTarget, so basically I have to find way to activate the eyedropper in WidgetTarget, check in the MainWindow if the eyedropper is activated, and send after to the WidgetTarget a signal with a QColor for example ?
Best Regards
Related
I am creating a drawing application with Qt and want to include undo and redo commands for whatever is drawn on a QImage. For this, I want to at least try and incorporate the Qt undo framework, since manually doing it will probably be above my skill level.
I have a MainWindow class where the main work is done and where I have the menu with undo and redo QActions.
The painting is done in a QWidget class called DrawingArea like this (PenShape is an enum of shapes):
void DrawingArea::drawLine(const QPoint &endPoint) {
QPainter painter(&image);
//some pen config code
switch (currentShape){
case PenShape::Polygon:
painter.drawPolygon(&endPoint, 5, Qt::OddEvenFill);
break;
case PenShape::Line:
painter.drawLine(lastPoint, endPoint);
break;
//other shapes and their draw methods..
}
update()
}
So as can be seen, the painter can draw in multiple shapes. I know I would have to somehow transfer this to a QUndoCommand class, but how? The drawline method is called only in DrawingArea's mouse event methods like this:
void DrawingArea::mousePressEvent(QMouseEvent *event){
if (event->button() == Qt::LeftButton) {
lastPoint = event->pos();
}
}
The QtUndoStack is located in MainWindow and the QActions are also there, but somehow I would have to connect the drawLine QtUndoCommand class and the mousePressEvent and mainWindow QAction with its connected slot method all together. This is what I don't know how to do.
Any help is appreciated!
Edit, here's the menu button actions:
m_undo = undoStack->createUndoAction(this, tr("&Undo"));
m_undo->setShortcuts(QKeySequence::Undo);
m_redo = undoStack->createRedoAction(this, tr("&Redo"));
m_redo->setShortcuts(QKeySequence::Redo);
I have no QUndoCommand classes because I'm unsure of how to create them yet.
In my MainWindow, I have a undoStack declared like this:
undoStack = new QUndoStack(this);
I have one QWidget which contains a multiple sliders. All sliders resized to main QWidget size. As result all sliders share same draw rectangle. For sliders I overload paintEvent method, so it draw only required stuff. Here is an example code:
class MySlider : public QSlider
{
void paintEvent(QPaintEvent *event) {
...
}
}
class MyWidget : public QWidget
{
MyWidget() : QWidget() {
slider1 = new MySlider(this);
slider2 = new MySlider(this);
slider1->resize(rect().width(), rect().height());
slider2->resize(rect().width(), rect().height());
}
MySlider * slider1;
MySlider * slider2;
}
adsf
Groove is not seen with this solution (because we don't call QSlider::paintEvent), but it still exist. For this widget it is possible to use only the last created slider (slider2). The rest are visible, but they are not available.
Is it possible to overlay multiple widgets on each other and still be able to access all of them with mouse event?
Overlapping widgets isn't a good idea, expect only one is visible at the same time. What is the purpose for that overlapping?
You can set QWidget::setAttribute(Qt::WA_TransparentForMouseEvents) to not generate any mouse events for that particular widget so that only one slider will get that events. Then you are able to redirect that messages to your other sliders.
EDIT and Some Self Critisicm
I tried both given solutions, which both solved my problem, and thus I thank you both! I marked the transparent solution as accepted because I thought it is was the easiest implementation when I only had one child widget, but I wish to share some insight for other beginners:
I first used QLabel, which apperently has enabled Qt::WA_TransparentForMouseEvents by default and thus obviously worked, but I also wanted the text to be selectable, by using QPlainTextEdit instead. Laughably, this is not possible in any way, because if you try to select the text (by clicking) you will close the window! I ended up keeping the transparancy, and neglecting the select-text-feature.
I'm guessing my following question has been answered somewhere before, but after an hour of searching I now post the question myself. I'm grateful if someone can point me to an already answered question that solves my problem.
Anyhow, I'm creating a popup window, using C++ and Qt. I've created the following PopupDialog class which works well and fine for all its purposes. However, I've removed its frame (including the bar containing the close button and window title) to make it look minimalistic, and now I want it to close if the user presses/releases the mouse button anywhere inside the popup window (dialog).
The below code works, however in such a way that I have to click and release the mouse exactly at the QDialog-window itself. It will not close when i click if the mouse hovers over the child widget(s) inside the QDialog, e.g. a QPlainTextEdit, which is displaying text.
Hence, I'm in need of a solution for QDialog to recognize QMouseEvents inside its child widgets. Please, don't hesitate to ask if something is unclear. I have not included my mainwindow.h/.cpp files, or popupdialog.ui file since I believe it would be a little too much to post here, but the .ui extremely simple: Just the QDialog window holding a QBoxLayout, containing a single widget, a QPlainTextEdit. I may posts these on request if it helps.
// popupdialog.h
#ifndef POPUPDIALOG_H
#define POPUPDIALOG_H
#include <QDialog>
#include <QString>
namespace Ui {class PopupDialog;}
class PopupDialog : public QDialog
{
Q_OBJECT
public:
explicit PopupDialog(QWidget *parent = 0, QString msgTxt="");
~PopupDialog();
private:
Ui::PopupDialog *ui;
QString messageText;
void mouseReleaseEvent(QMouseEvent*);
};
#endif //POPUPDIALOG_H
...
// popupdialog.cpp
#include "popupdialog.h"
#include "ui_popupdialog.h"
PopupDialog::PopupDialog(QWidget *parent, QString msgTxt) :
QDialog(parent),
ui(new Ui::PopupDialog),
messageText(msgTxt)
{
ui->setupUi(this);
setWindowFlags(Qt::Window | Qt::FramelessWindowHint);
setModal(true);
ui->message_text_display->setText(messageText);
// The message_text_display is an instance of the class,
// "PlainTextEdit". Using "QLabel" partly solves my
// problem, but does not allow text selection.
}
PopupDialog::~PopupDialog()
{
delete ui;
}
void PopupDialog::mouseReleaseEvent(QMouseEvent *e)
{
this->close();
}
As you already noticed mouse events are handled from child widgets and propagated to parents if not accepted. You can read more about it here
To close your popup window when the click is done inside a child widget you can do two things. You could try looking into installEventFilter and set it up on each child widget to call close().
Another option would require you to have a kind of centralWidget (like the MainWindow usually has) - just to group all your child widgets. This way you could call setAttribute() on it to set Qt::WA_TransparentForMouseEvents property to simply skip handling mouse events on the widget and all of its children.
groupWidget->setAttribute(Qt::WA_TransparentForMouseEvents);
According to Qt docs:
When enabled, this attribute disables the delivery of mouse events to
the widget and its children. Mouse events are delivered to other
widgets as if the widget and its children were not present in the
widget hierarchy; mouse clicks and other events effectively "pass
through" them. This attribute is disabled by default.
Which basically means the event would be passed up the chain to the first widget which can handle the event. In your case it would be the PopupDialog and the already overriden mouseReleaseEvent slot.
in header file
class PopupDialog : public QDialog
{
Q_OBJECT
public:
explicit PopupDialog(QWidget *parent = 0, QString msgTxt="");
~PopupDialog();
//////////////////////////////////
protected:
bool eventFilter(QObject *obj, QEvent *event);
//////////////////////////////////////
private:
Ui::PopupDialog *ui;
QString messageText;
void mouseReleaseEvent(QMouseEvent*);
};
in cpp
PopupDialog::PopupDialog(QWidget *parent, QString msgTxt) :
QDialog(parent),
ui(new Ui::PopupDialog),
messageText(msgTxt)
{
ui->setupUi(this);
setWindowFlags(Qt::Window | Qt::FramelessWindowHint);
setModal(true);
ui->message_text_display->setText(messageText);
// The message_text_display is an instance of the class,
// "PlainTextEdit". Using "QLabel" partly solves my
// problem, but does not allow text selection.
///////////////////////////////////////
foreach (QObject *child, children())
{
child->installEventFilter(this);
}
///////////////////////////////////////
}
///////////////////////////////////////
bool PopupDialog::eventFilter(QObject *obj, QEvent *event)
{
if(event->type() == QEvent::MouseButtonRelease)
{
this->close();
}
}
I am using Qt 5.7 (the latest version). I can't get the mouse events to work in QGraphicsScene, but they work in window outside of my scene. I have followed this question.
So I have overwritten QWidget::mouseMoveEvent() in my main widget's subclass like this:
// header:
class MyWidget {
...
void mouseMoveEvent( QMouseEvent * event );
};
// source:
MyWidget::MyWidget() {
setMouseTracking();
}
void MyWidget::mouseMoveEvent( QMouseEvent * event ) {
}
It doesn't work for: mouseMoveEvent, mouseGrabber, mousePressEvent, mouseReleaseEvent, or mouseDoubleClickEvent. But somehow it only works for mousePressEvent.
Could this be a bug in Qt?
SOURCE CODE:
In objectloader.cpp
ObjectLoader::ObjectLoader(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::ObjectLoader)
{
ui->setupUi(this);
scene=new QGraphicsScene(this);
ui->graphicsView->setScene(scene);
ui->graphicsView->setMouseTracking(true);
setMouseTracking(true);
}
Thats were i set mouse tracking twice
In objectloader.h
Then i define that method in objectloader.h
class ObjectLoader : public QMainWindow
{
Q_OBJECT
public:
explicit ObjectLoader(QWidget *parent = 0);
~ObjectLoader();
private slots:
void mouseMoveEvent(QMouseEvent *event);
protected:
private:
};
#endif // OBJECTLOADER_H
And implementation of that method in objectloader.cpp
void ObjectLoader::mouseMoveEvent(QMouseEvent *event){
qDebug()<<"Mouse moved";
}
When a mouse event is generated by Qt it is generally passed initially to the QWidget that was under the mouse pointer when the event was generated. If that QWidget accepts the event then no further processing will take place. If the event isn't accepted then Qt may propogate the event to that QWidget's parent and so on.
In your particular case the mouse move events you are interested in are being sent to the QGraphicsView/QGraphicsScene conponents where they are being accepted and, hence, no further processing takes place. In a case like that you generally need to install an event filter to intercept and process the events of interest.
Mouse move events will occur only when a mouse button is pressed down, unless mouse tracking has been enabled with QWidget::setMouseTracking().
So, I think you should check whether mouseTracking is really enabled or not, by using `bool hasMouseTracking() const'.
I have derived from both QGraphicsView and QGraphicsRectItem. I overloaded the contextMenuEvent on both classes to provide popup menus. I want the QGraphicsView context menu when you click on white space the the QGraphicsItem popup menu when you click on an item.
At first implementation, I got the QGraphicsView popup no matter where I clicked. So I modified the contextMenuEvent as follows:
void CustomGraphicsView::contextMenuEvent(QContextMenuEvent* event)
{
if (QGraphicsItem *item = itemAt(event->pos())) {
MyRect* rect = dynamic_cast<MyRect*>(item);
QGraphicsSceneContextMenuEvent* context_event = dynamic_cast<QGraphicsSceneContextMenuEvent*>(event);
if (rect && context_event)
rect->contextMenuEvent(context_event);
}
else {
QMenu menu;
... create the QGraphicsView popup menu
}
}
The dynamic_cast for the QGraphicsSceneContextMenuEvent fails so I never call the contextMenuEvent for the rect. It won't compile if I just try to pass the event to the rect->contextMenu(), so I tried the cast.
What is the right way to do this?
This is a learning project to just create/move/rotate/delete 2D shapes using Qt. If someone wants to look at the whole thing, let me know.
OK, so I figured it out. Just make sure to pass the event through the base class method. Simple! This also works for the mousePressEvent(), mouseMoveEvent(), and mouseReleaseEvent functions.
void CustomGraphicsView::contextMenuEvent(QContextMenuEvent* event)
{
// if the event is on a GGraphicsItem just pass the event along
if (itemAt(event->pos())) {
QGraphicsView::contextMenuEvent(event);
}
else
{
QMenu menu;
... create popup for the CustomGraphicsView