I have such program: in my Widget I have qpushbuttons, qslider and qgraphicsview. I place qgraphicsscene in qgraphicsview. The problem is that when I click in QGraphicsscene and want to draw a Point, that was clicked, there is a displacement. When I click in center of QGraphicsScene there is not any problems.
if (mouseEvent->button() == Qt::LeftButton)
{
QPointF pos = mouseEvent->scenePos();
addEllipse(pos.x(), pos.y(), 5, 5, QPen(QColor(Qt::green)), QBrush(QColor(Qt::red)));
}
There is a screen too.
So, the question is how to avoid this moving of scene.
In the screen I have clicked in right bottom, but point was drawn in the center
Try this. In my computer it works without displacement
.*h
#ifndef GRAPHICSSCENE_H
#define GRAPHICSSCENE_H
#include <QGraphicsScene>
#include <QMouseEvent>
class GraphicsScene : public QGraphicsScene
{
Q_OBJECT
public:
explicit GraphicsScene(QObject *parent = 0);
signals:
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent);
public slots:
};
#endif // GRAPHICSSCENE_H
*.cpp
#include "graphicsscene.h"
#include <QDebug>
#include <QGraphicsSceneMouseEvent>
GraphicsScene::GraphicsScene(QObject *parent) :
QGraphicsScene(parent)
{
}
void GraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
qDebug() << "in";
if (mouseEvent->button() == Qt::LeftButton)
{
QPointF pos = mouseEvent->scenePos();
addEllipse(pos.x(), pos.y(), 5, 5, QPen(QColor(Qt::green)), QBrush(QColor(Qt::red)));
}
}
Using
GraphicsScene *scene = new GraphicsScene(this);
ui->graphicsView->setSceneRect(50,50,50,50);//for example
ui->graphicsView->setScene(scene);
ui->graphicsView->show();
view->setSceneRect(0, 0, 640, 480);
has helped me
Related
This Project was going to drag a picture in frameless Widget, and print the coordinates.
create a Pro;
create paintEvent(), mousePressEvent(), mouseMoveEvent() inherited from Event in QWidget.
widget.h
#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
#include <QPainter>
#include <QMouseEvent>
#include <QDebug>
QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE
class Widget : public QWidget
{
Q_OBJECT
public:
Widget(QWidget *parent = nullptr);
~Widget();
private:
Ui::Widget *ui;
protected:
void paintEvent(QPaintEvent*);
void mousePressEvent(QMouseEvent *);
void mouseMoveEvent(QMouseEvent *);
private:
QPixmap pix; // drawing picture
QPoint pt; // globalPos() - this->frameGeometry().topLeft()
};
#endif // WIDGET_H
set Attributes of Widget, and print coordinates;
widget.cpp
#include "widget.h"
#include "ui_widget.h"
Widget::Widget(QWidget *parent)
: QWidget(parent)
, ui(new Ui::Widget)
{
ui->setupUi(this);
pix.load("D:\\sun.png");
this->setWindowFlags(Qt::FramelessWindowHint);
this->setAttribute(Qt::WA_TranslucentBackground);
}
Widget::~Widget()
{
delete ui;
}
void Widget::paintEvent(QPaintEvent* ){
QPainter p(this);
p.drawPixmap(0,0,pix);
}
void Widget::mousePressEvent(QMouseEvent *ev){
if(ev->button()==Qt::LeftButton){
// pt=ev->globalPos() - this->frameGeometry().topLeft(); //it works, and mouse position wouldn't change
}else if(ev->button()==Qt::RightButton){
this->close();
}
}
void Widget::mouseMoveEvent(QMouseEvent *ev){
// this->move(ev->globalPos()-pt);
// qDebug()<<"POS:"<<ev->pos()<<"**GLOBAL:"<<ev->globalPos()<<"-"<<pt<<"**TopLeft: "<<this->geometry().topLeft();
// it works but the mouse's position will change after the mouseMoveEvent triggered.
// the mouse's position changed to geometry().topLeft()
this->move(ev->pos()+this->geometry().topLeft());
}
So, why did the position changed? what happened in the mouseMoveEvent(...)
I'll give you a minimal reproduceable example that was a part of the more complex widget.
Here we just have a custom widget(called MovableItem) with a simple paintEvent. Widget is created, placed onto the central widget and moved to mouse position on MainWindow::mousePressEvent-s.
When moving, it seems like the widget is getting clipped at the side it's moving towards.
mainwindow.h
#include <QMainWindow>
#include <QMouseEvent>
#include <QPropertyAnimation>
#include "movableitem.h"
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
void mousePressEvent(QMouseEvent *event) override;
QWidget* mItem;
};
mainwindow.cpp
#include "mainwindow.h"
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
resize(640, 480);
QWidget* central_widget = new QWidget(this);
mItem = new MovableItem(central_widget);
mItem->move(20, 20);
setCentralWidget(central_widget);
}
void MainWindow::mousePressEvent(QMouseEvent *event) {
QPoint pos = event->pos();
QPropertyAnimation* anim = new QPropertyAnimation(mItem, "geometry");
anim->setDuration(750);
anim->setStartValue(QRect(mItem->x(), mItem->y(), mItem->width(), mItem->height()));
anim->setEndValue(QRect(pos.x(), pos.y(), mItem->width(), mItem->height()));
anim->start();
}
MainWindow::~MainWindow() {}
movableitem.h
#include <QWidget>
#include <QPainter>
#include <QPainterPath>
class MovableItem : public QWidget
{
Q_OBJECT
public:
MovableItem(QWidget *parent = nullptr);
QSize sizeHint() const override;
void paintEvent(QPaintEvent *event) override;
};
movableitem.cpp
#include "movableitem.h"
MovableItem::MovableItem(QWidget *parent) : QWidget(parent)
{
setParent(parent);
}
QSize MovableItem::sizeHint() const {
return QSize(150, 40);
}
void MovableItem::paintEvent(QPaintEvent *event) {
QRect r = rect();
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing);
QPainterPath path;
path.addRoundedRect(r, 5, 5);
QBrush brush(QColor(217, 217, 217));
painter.fillPath(path, brush);
painter.drawPath(path);
}
Example
As you can see, movement is not fluid, but choppy. I have no idea what is happening. Am I doing something completely wrong ? Do I need to implement some additional functions, is double buffering needed, is this because of Qt's automatic clipping ? Should I rewrite it in QGraphicsView ?
Add mItem->repaint(); and mItem->update(); in mousePressEvent function
void MainWindow::mousePressEvent(QMouseEvent *event)
{
QPoint pos = event->pos();
QPropertyAnimation* anim = new QPropertyAnimation(mItem, "geometry");
anim->setDuration(750);
anim->setStartValue(QRect(mItem->x(), mItem->y(), mItem->width(), mItem->height()));
anim->setEndValue(QRect(pos.x(), pos.y(), mItem->width(), mItem->height()));
anim->start();
mItem->repaint();
mItem->update();
}
my out put is here :
I am having issues moving a QGraphicItem in a custom QGraphicView class. What I would like to be able to to do is select the item by a left mouse click and then move it to where I've done a right mouse click.
I stongly suspect that my problem is that QGraphicsItem::setPos() requires the coordinates to be in parent coordinates, and I'm unsure which for of QMouseEvent::*Pos() to use, and how to convert it to parent coordinates.
Screens shots of what is happening, versus what I what follow the code.
main.cpp: (simple main here, standard test harness)
#include "QtTest.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QtTest w;
w.show();
return a.exec();
}
QtTest.h: (This defines the main application window)
#pragma once
#include <QtWidgets/QMainWindow>
class QGraphicsView;
class QGraphicsScene;
class QGraphicsItem;
class QMouseEvent;
class QtTest : public QMainWindow
{
Q_OBJECT
public:
QtTest(QWidget *parent = Q_NULLPTR);
private:
QGraphicsView* m_gv;
QGraphicsScene* m_pScene;
void setupUI();
};
QtTest.cpp: (implementation of the main application window)
#include "QtTest.h"
#include "testGV.h"
#include <QVariant>
#include <QApplication>
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QGraphicsItem>
#include <QMainWindow>
#include <QMouseEvent>
#include <QWidget>
QtTest::QtTest(QWidget *parent): QMainWindow(parent)
{
setupUI();
}
void QtTest::setupUI()
{
QWidget *centralWidget;
if (objectName().isEmpty())
setObjectName("QtTestClass");
resize(600, 400);
centralWidget = new QWidget(this);
centralWidget->setObjectName("centralWidget");
m_gv = new testGV(centralWidget);
m_gv->setObjectName("graphicsView");
m_gv->setGeometry(QRect(100, 10, 441, 331));
setCentralWidget(centralWidget);
}
testGV.h: (definition of custom widget)
#pragma once
#include <QGraphicsView>
#include <QGraphicsItem>
class testGV : public QGraphicsView
{
Q_OBJECT
public:
testGV(QWidget* parent);
protected:
void mousePressEvent(QMouseEvent*);
private:
QGraphicsScene* m_pScene;
QGraphicsItem* m_pItem;
void createScene();
};
testGV.cpp: (implementation of custom widget)
#include "testGV.h"
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QGraphicsItem>
#include <QMouseEvent>
testGV::testGV(QWidget* parent) : QGraphicsView(parent)
{
createScene();
}
void testGV::createScene()
{
m_pScene = new QGraphicsScene();
m_pScene->addRect(QRect(30, 30, 150, 150), QPen(Qt::black), QBrush(Qt::black, Qt::NoBrush));
QGraphicsEllipseItem* pTemp = m_pScene->addEllipse(QRect(0, 0, 15, 15), QPen(Qt::black), QBrush(Qt::red, Qt::SolidPattern));
pTemp->setFlag(QGraphicsItem::ItemIsMovable);
pTemp->setFlag(QGraphicsItem::ItemSendsGeometryChanges);
setScene(m_pScene);
}
void testGV::mousePressEvent(QMouseEvent* pEvent)
{
if (pEvent->button() == 1) // left button click
{
m_pItem = itemAt(pEvent->pos());
}
else if (pEvent->button() == 2) // right button click
{
m_pItem->setPos(pEvent->pos());
m_pScene->update();
}
}
The image on the left is the initial display, when I right click on the red dot and then click in the square at about where the black dot is I get the image on the right. What I'm after is the red dot moving to where I clicked.
The cause of the problem is that the QMouseEvent has the position information in the coordinates of the view but the item uses the coordinates of the scene. The solution in that case is to map the coordinates of the view to the coordinates of the scene:
void testGV::mousePressEvent(QMouseEvent* pEvent)
{
if (pEvent->button() == Qt::LeftButton)
m_pItem = itemAt(pEvent->pos());
else if (pEvent->button() == Qt::RightButton)
if(m_pItem)
m_pItem->setPos(mapToScene(pEvent->pos()));
}
But even so there is a problem, the position for your items is with respect to the topLeft so the displacement will have an error, if you want to avoid that deviation then you must consider the position of the left click:
void testGV::mousePressEvent(QMouseEvent* pEvent)
{
if (pEvent->button() == Qt::LeftButton){
m_pItem = itemAt(pEvent->pos());
m_pItem->setData(0, mapToScene(pEvent->pos()));
}
else if (pEvent->button() == Qt::RightButton)
if(m_pItem){
QPointF p = m_pItem->data(0).toPointF();
QPointF sp = mapToScene(pEvent->pos());
m_pItem->setPos(m_pItem->pos() + sp - p);
m_pItem->setData(0, sp);
}
}
Note: When a pointer is created it points to any memory location so that can cause problems so I recommend initializing it to nullptr and also checking if the pointer is valid:
testGV::testGV(QWidget* parent) : QGraphicsView(parent), m_pItem(nullptr)
{
createScene();
}
I'm trying to create a canvas to draw on with the mouse similar to most digital painting applications that I can also zoom in on (zoom in on the drawn image)
So far I've created a class that uses QWidget and added it to the ui then use the mouse events and QPaintEvent to draw on this widget which works. However the problem I'm not sure how do I zoom on this as well? I tried placing the QWidget inside of a scrollable area but it stops it from registering click events. I also tried extending from QGraphicsViewer instead of QWidget but this stops me from being able to paint as well.
//Class definition
PaintArea::PaintArea(QWidget *parent) : QWidget(parent)
{
this->setMouseTracking(true);
}
I'm mostly looking for a recommendation of how to scrolling and drawing with a mouse on the same widget (Possibly with scroll bar but just wheel scrolling for sure)
Thanks
If you follow the QWidget way, you may want to look carefully to the scribble example that is included with Qt docs. In this example, the drawing is made off-screen on a QImage object, which is then painted by the widget. The problem is to zoom the image.
I prefer your second way: QGraphicsView has a scale() function among many other excellent features. You may do something similar to the scribble example: draw off-screen on a QPixmap image which is set (every time you change the image) into a QGraphicsPixmapItem which belongs to the QGraphicsScene. I've implemented this crude example, borrowing some elements from the scribble example. Use the mouse wheel to zoom the image (it screws the scrolling a bit, sorry).
test.pro
QT += core gui widgets
CONFIG += c++11
DEFINES += QT_DEPRECATED_WARNINGS
SOURCES += \
drawablescene.cpp \
main.cpp \
mainwindow.cpp
HEADERS += \
drawablescene.h \
mainwindow.h
main.cpp
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "drawablescene.h"
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = nullptr);
void wheelEvent(QWheelEvent *event) override;
private:
QGraphicsView *m_view;
DrawableScene *m_scene;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include <QGraphicsView>
#include <QWheelEvent>
#include "mainwindow.h"
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent),
m_view(new QGraphicsView(this)),
m_scene(new DrawableScene(this))
{
setCentralWidget(m_view);
m_scene->setSceneRect(0,0,640,480);
m_view->setScene(m_scene);
}
void MainWindow::wheelEvent(QWheelEvent *event)
{
qreal delta = 1 + (event->delta() > 0 ? 0.1 : -0.1);
m_view->scale(delta, delta);
event->accept();
}
drawablescene.h
#ifndef DRAWABLESCENE_H
#define DRAWABLESCENE_H
#include <QObject>
#include <QGraphicsScene>
#include <QGraphicsPixmapItem>
class DrawableScene : public QGraphicsScene
{
public:
explicit DrawableScene(QObject *parent = nullptr);
private:
void mouseMoveEvent(QGraphicsSceneMouseEvent *mouseEvent) override;
void mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent) override;
void mouseReleaseEvent(QGraphicsSceneMouseEvent *mouseEvent) override;
void drawLineTo(const QPointF &endPoint);
bool m_modified;
bool m_scribbling;
int m_penWidth;
QColor m_penColor;
QPointF m_lastPoint;
QPixmap *m_image;
QGraphicsPixmapItem *m_item;
};
#endif // DRAWABLESCENE_H
drawablescene.cpp
#include <QGraphicsSceneMouseEvent>
#include <QPainter>
#include "drawablescene.h"
DrawableScene::DrawableScene(QObject *parent)
: QGraphicsScene(parent),
m_modified(false),
m_scribbling(false),
m_penWidth(3),
m_penColor(Qt::blue)
{
m_image = new QPixmap(640, 480);
m_image->fill(Qt::white);
m_item = addPixmap(*m_image);
}
void DrawableScene::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
if ((event->buttons() & Qt::LeftButton) && m_scribbling) {
drawLineTo(event->scenePos());
event->accept();
}
else QGraphicsScene::mouseMoveEvent(event);
}
void DrawableScene::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
if (event->button() == Qt::LeftButton) {
m_lastPoint = event->scenePos();
m_scribbling = true;
event->accept();
}
else QGraphicsScene::mousePressEvent(event);
}
void DrawableScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
if (event->button() == Qt::LeftButton && m_scribbling) {
drawLineTo(event->scenePos());
m_scribbling = false;
event->accept();
}
else QGraphicsScene::mouseReleaseEvent(event);
}
void DrawableScene::drawLineTo(const QPointF &endPoint)
{
QPainter painter(m_image);
painter.setPen(QPen(m_penColor, m_penWidth, Qt::SolidLine, Qt::RoundCap,Qt::RoundJoin));
painter.drawLine(m_lastPoint, endPoint);
m_modified = true;
m_lastPoint = endPoint;
m_item->setPixmap(*m_image);
}
I've this problem for several days. I have created QGraphicsItem and I want to stretch/adjust it's size to size of my QGraphicsView. I was using paint() method, but got with it problems with updating. Now I've used boundingRect() but it uses fixed size. When I set too big size it expand my scene and scrollbars are appearing. Is there way to adjust size of item to size of View?
EDIT: I want only adjust height of my object.
Here's some code:
Header of my Item:
#ifndef POINTER_H
#define POINTER_H
#include <QObject>
#include <QColor>
#include <QRect>
#include <QGraphicsLineItem>
#include <QPainter>
#include <QGraphicsSceneMouseEvent>
class Pointer : public QGraphicsLineItem
{
public:
Pointer();
void paint(QPainter * painter, const QStyleOptionGraphicsItem * option, QWidget * widget);
QRectF boundingRect() const;
int position;
void changePosition(int x);
};
#endif // TRACKPOINTER_H
Implementation of my Item:
#include "pointer.h"
Pointer::Pointer()
{
//this->setFlag(QGraphicsLineItem::ItemIsMovable);
//setFlag(QGraphicsLineItem::ItemIsFocusable);
//setFocus();
}
void Pointer::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
QPen pen(Qt::red);
painter->setPen(pen);
painter->setBrush(QColor(77,77,77));
painter->drawLine(0,0,0,2000);
}
QRectF Pointer::boundingRect() const
{
return QRectF(0,0,2,600);
}
void Pointer::changePosition(int x)
{
//position = x;
setPos(x,0);
update();
}
And my Window:
Window::Window(Timers *timer, TrackPointer *tp)
{
Timeline = new QGraphicsScene(this);
TimelineView = new QGraphicsView(Timeline);
TimelineView->setAlignment(Qt::AlignTop|Qt::AlignLeft);
QVBoxLayout *timeLineLayout = new QVBoxLayout;
timeLineLayout->addWidget(TimelineView);
Pointer *pointer = new Pointer;
Timeline->addItem(pointer);
}
I have also problems with my scene: When my object moves somewhere away - it expand scene. Later when I bring my object back to it's starting position scene still is expanded and I have scrollbars to scroll my view around the scene. Is there way to decrease scene size using my object?
The promised example looks something like this:
MainWindow.h
#include <QMainWindow>
class QGraphicsView;
class QGraphicsRectItem;
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = nullptr);
bool eventFilter(QObject *watched, QEvent *event) override;
private:
QGraphicsView *m_view;
QGraphicsRectItem *m_item;
};
MainWindow.cpp
#include "MainWindow.h"
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QGraphicsRectItem>
#include <QEvent>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
m_view(new QGraphicsView(this)),
m_item(new QGraphicsRectItem(0, 0, 1, 1))
{
m_view->setScene(new QGraphicsScene());
m_view->setFrameStyle(QFrame::NoFrame);
m_view->setAlignment(Qt::AlignLeft | Qt::AlignTop);
m_view->setSceneRect(0, 0, 1, 1);
m_view->installEventFilter(this);
m_view->scene()->addItem(m_item);
setCentralWidget(m_view);
resize(600, 400);
}
bool MainWindow::eventFilter(QObject *watched, QEvent *event)
{
if ((watched == m_view) && (event->type() == QEvent::Resize))
m_item->setRect(m_view->viewport()->rect().adjusted(5, 5, -5, -5));
return QMainWindow::eventFilter(watched, event);
}
look into :QGraphicsView::fitInView
http://doc.qt.io/qt-4.8/qgraphicsview.html#fitInView
QPixmap *pixMap= new QPixmap();;
QGraphicsScene *scene=new QGraphicsScene();;
pixMap->loadFromData(jpegData);
scene->clear();
pixMapItem = scene->addPixmap(*pixMap);
ui->graphicsView->fitInView(scene->sceneRect(), Qt::KeepAspectRatio);
ui->graphicsView->show();
ui->graphicsView->viewport()->update();