Im implementing the zooming of my QGraphicsView using wheelEvent
void View::wheelEvent(QWheelEvent *e)
{
if (e->modifiers().testFlag(Qt::ControlModifier)){ // zoom only when CTRL key pressed
int numSteps = e->delta() / 15 / 8;
if (numSteps == 0) {
e->ignore();
return;
}
qreal sc = pow(1.25, numSteps); // I use scale factor 1.25
this->zoom(sc);
e->accept();
}
}
and the zoom item
void View::zoom(qreal scaleFactor)
{
scale(scaleFactor, scaleFactor);
}
here i don’t want to zoom out too deeper, all i need it to restrict the scaling to certain point , i have to limit the zoom out so i tried to find the transform point
qreal
View::zoomScale() const
{
return transform().m11();
}
but with this i cant able to restrict the zooming .
please help me find the solution.
You can calculate the zoom factor relative to the "normal zoom" and decide if you can zoom or not.
For example, you can take a QRect for reference and check its size after the zoom :
void ClassA::scale(qreal scaleFactor) {
QRectF(0, 0, 1, 1); // A reference
qreal factor = transform().scale(scaleFactor, scaleFactor).mapRect(r).width(); // absolute zoom factor
if ( factor > 20 ) { // Don't zoom more than 20x
return;
}
this->scale(scaleFactor, scaleFactor);
}
Related
I want to make an implementation of chart selection based on QChart and QChartView.
The family of the classes have a big advantage - easy use of openGL and animations, for example:
QLineSeries *series = new QLineSeries();
series->setUseOpenGL(true); // <==
QChart *chart = new QChart();
chart->addSeries(series);
chart->setAnimationOptions(QChart::AllAnimations); // <==
QChartView *chartView = new QChartView(chart);
chartView->setRenderHint(QPainter::Antialiasing);
The QChartView class provides the useful zoom feature - QChartView::setRubberBand():
chartView->setRubberBand(QChartView::RectangleRubberBand);
The main problem is that the rubber band can be used only for zoom, but I need to implement it for horizontal selection without zoom, as the feature usually implemented in audio editors:
Now, when I have inherit QChartView, I can disable zoom after selection:
class ChartView : public QChartView
...
bool m_drawRubberBand;
QRubberBand m_rubberBand;
...
ChartView::ChartView(QChart *chart, QWidget *parent)
: QChartView(chart, parent)
{
setRubberBand(QChartView::HorizontalRubberBand);
}
...
// Just copy-paste from the Qt 5 sources - file \Src\qtcharts\src\charts\qchartview.cpp:
/*!
If the rubber band rectangle is displayed in the press event specified by
\a event, the event data is used to update the rubber band geometry.
Otherwise, the default QGraphicsView::mouseMoveEvent() implementation is called.
*/
void ChartView::mouseMoveEvent(QMouseEvent *event)
{
if (m_drawRubberBand && m_rubberBand.isVisible())
{
QRect rect = chart()->plotArea().toRect();
int width = event->pos().x() - m_rubberBandOrigin.x();
int height = event->pos().y() - m_rubberBandOrigin.y();
if (!rubberBand().testFlag(VerticalRubberBand))
{
m_rubberBandOrigin.setY(rect.top());
height = rect.height();
}
if (!rubberBand().testFlag(HorizontalRubberBand))
{
m_rubberBandOrigin.setX(rect.left());
width = rect.width();
}
m_rubberBand.setGeometry(QRect(m_rubberBandOrigin.x(), m_rubberBandOrigin.y(), width, height).normalized());
}
else
{
QGraphicsView::mouseMoveEvent(event);
}
}
Then I can just don't implement the zoom action on the mouse key release event:
void ChartView::mouseReleaseEvent(QMouseEvent *event)
{
if (m_rubberBand.isVisible())
{
if (event->button() == Qt::LeftButton)
{
m_drawRubberBand = false;
do_nothing(); // <==
}
}
}
So, my questions now:
How borders of the the visual rubber band can be mapped to real chart's coordinates. I.e., how can the selection be mapped into a line series on the chart? Now I receive same wrong coordinates:
void MyView::resizeEvent(QResizeEvent *event)
{
QChartView::resizeEvent(event);
QRect rct(QPoint(10, 10), QPoint(20, 20));
qDebug() << mapToScene(rct); <==
}
Output:
QPolygonF(QPointF(10,10)QPointF(21,10)QPointF(21,21)QPointF(10,21))
QPolygonF(QPointF(10,10)QPointF(21,10)QPointF(21,21)QPointF(10,21))
QPolygonF(QPointF(10,10)QPointF(21,10)QPointF(21,21)QPointF(10,21))
QPolygonF(QPointF(10,10)QPointF(21,10)QPointF(21,21)QPointF(10,21))
...
How can an existing rubber selection be proportionally resized together with the view?
Edit: May be it is a useful keyword - QGraphicsScene::setSelectionArea().
The Qt 5 chip example which provides nice rubber band selection, but the example based on QGraphicsView, not on QChartView.
The question is resolved thanks to the reply to this answer: Get mouse coordinates in QChartView's axis system
The key moment: it was necessary to invoke QChart::mapToValue() for a correct coordinates transform:
QPointF ChartView::point_to_chart(const QPoint &pnt)
{
QPointF scene_point = mapToScene(pnt);
QPointF chart_point = chart()->mapToValue(scene_point);
return chart_point;
}
And the inverse transformation:
QPoint ChartView::chart_to_view_point(QPointF char_coord)
{
QPointF scene_point = chart()->mapToPosition(char_coord);
QPoint view_point = mapFromScene(scene_point);
return view_point;
}
That's how I have implemented resize of the rubber band on the resizeEvent.
Firstly, I save the current rubber band on mouse release event:
void ChartView::mouseReleaseEvent(QMouseEvent *event)
{
if (m_rubberBand.isVisible())
{
update_rubber_band(event);
m_drawRubberBand = false;
save_current_rubber_band(); <==
}
}
Where:
void ChartView::update_rubber_band(QMouseEvent * event)
{
QRect rect = chart()->plotArea().toRect();
int width = event->pos().x() - m_rubberBandOrigin.x();
int height = event->pos().y() - m_rubberBandOrigin.y();
if (!rubberBand().testFlag(VerticalRubberBand))
{
m_rubberBandOrigin.setY(rect.top());
height = rect.height();
}
if (!rubberBand().testFlag(HorizontalRubberBand))
{
m_rubberBandOrigin.setX(rect.left());
width = rect.width();
}
m_rubberBand.setGeometry(QRect(m_rubberBandOrigin.x(), m_rubberBandOrigin.y(), width, height).normalized());
}
And:
void ChartView::save_current_rubber_band()
{
QRect rect = m_rubberBand.geometry();
QPointF chart_top_left = point_to_chart(rect.topLeft());
m_chartRectF.setTopLeft(chart_top_left);
QPointF chart_bottom_right = point_to_chart(rect.bottomRight());
m_chartRectF.setBottomRight(chart_bottom_right);
}
And how I repaint the rubber on the resize event:
void ChartView::resizeEvent(QResizeEvent *event)
{
QChartView::resizeEvent(event);
if (m_rubberBand.isVisible())
{
restore_rubber_band();
}
apply_nice_numbers();
}
Where:
void ChartView::restore_rubber_band()
{
QPoint view_top_left = chart_to_view_point(m_chartRectF.topLeft());
QPoint view_bottom_right = chart_to_view_point(m_chartRectF.bottomRight());
m_rubberBandOrigin = view_top_left;
m_rubberBand.setGeometry(QRect(view_top_left, view_bottom_right));
}
And don't forget about the "nice numbers":
void ChartView::apply_nice_numbers()
{
QList<QAbstractAxis*> axes_list = chart()->axes();
for each(QAbstractAxis* abstract_axis in axes_list)
{
QValueAxis* value_axis = qobject_cast<QValueAxis*>(abstract_axis);
if (value_axis)
{
value_axis->applyNiceNumbers();
}
}
}
This logic in action.
Before resize:
After resize:
I make my own class from QWidget with redefine of paintEvent(), mousePressEvent(), mouseReleaseEvent() and mouseMoveEvent(). All that methods for move widgets over other widget (yellow).
When i create my widgets in a layout, it looks like this:
But when I move black widget to the bottom and red to the top like this:
and resize window, all widgets refresh to their align positions:
But i want, when i move one widget higher then another, the widgets should align in layout in new places, like this:
Which function i should redefine to do it?
P.S.
There is a piece of code, that can move widgets positions inside layout (change their indexes), but i don't know how find out their (x,y) position to calculate new indexes in layout. I think, that i can do it in resizeEvent().
But it when it event was emitted, positions already changed to old. (like before moveing on 1 picture), and i need positions after moveing (like on secon picture). How can i get position of widget before it will be aligned?
or How can i change order of widget in layout by drag and drop with the mouse?
I write my own widget, then redefine following methods: mouseReleaseEvent(), paintEvent(), mousePressEvent(), mouseMoveEvent(). In mousePressEvent() I hold old X and Y positions and mouse position on figure. Then in mouseMoveEvent() i calculate if minimum distance of mouse move is riched and move widget to new position (it not moves widget index in layout). After it, if emitted mouseReleaseEvent() i just calculate new index of moving widget and change and update parent layout. If widget moves less then it height, then layout just updates without changing widget index.
void SimpleWidget::mouseMoveEvent(QMouseEvent *event)
{
if (!(event->buttons() & Qt::LeftButton))
return;
if (!IsMinimumDistanceRiched(event))
{
return;
}
int y = event->globalY() - mouseClickY + oldY;
int BottomBorder = parentWidget->geometry().height() - this->geometry().height();
if(y < 0) y = 0;
else if(y > BottomBorder) y = BottomBorder;
move(oldX, y);
}
void SimpleWidget::mousePressEvent(QMouseEvent *event)
{
if (event->buttons() & Qt::LeftButton)
dragStartPosition = event->pos();
oldX = this->geometry().x();
oldY = this->geometry().y();
mouseClickX = event->globalX();
mouseClickY = event->globalY();
}
bool SimpleWidget::IsMinimumDistanceRiched(QMouseEvent *event)
{
return (event->pos() - dragStartPosition).manhattanLength() >= QApplication::startDragDistance();
}
bool SimpleWidget::moveInLayout(QWidget *widget, MoveDirection direction)
{
QVBoxLayout* myLayout = qobject_cast<QVBoxLayout*>(widget->parentWidget()->layout());
const int index = myLayout->indexOf(widget);
if (direction == MoveUp && index == 0)
{
return false;
}
if (direction == MoveDown && index == myLayout->count()-1 )
{
return false;
}
const int newIndex = direction == MoveUp ? index - 1 : index + 1;
myLayout->removeWidget(widget);
myLayout->insertWidget(newIndex , widget);
return true;
}
void SimpleWidget::paintEvent(QPaintEvent *)
{
QStyleOption o;
o.initFrom(this);
QPainter p(this);
style()->drawPrimitive(QStyle::PE_Widget, &o, &p, this);
}
void SimpleWidget::mouseReleaseEvent(QMouseEvent *)
{
int y = geometry().y();
MoveDirection direct;
int offset;
if(oldY > y)
{
offset = oldY - y;
direct = MoveUp;
}
else if(oldY < y)
{
offset = y - oldY;
direct = MoveDown;
}
int count = offset/height();
for(int i = 0; i < count; i++)
{
moveInLayout(this, direct);
}
update();
QVBoxLayout* myLayout = qobject_cast<QVBoxLayout*>(this->parentWidget->layout());
myLayout->update();
this->saveGeometry();
}
I am zooming an image on a label using QGraphicsView. But when I zoom out I want to set a specific limit for the zoom out. I am using the following code
scene = new QGraphicsScene(this);
view = new QGraphicsView(label);
QPixmap pix("/root/Image);
Scene->addPixmap(pixmap);
view->setScene(scene);
view->setDragMode(QGraphicsView::scrollHandDrag);
In the slot of wheel event
void MainWindow::wheelEvent(QWheelEvent *ZoomEvent)
{
view->setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
double scaleFactor = 1.15;
if(ZoomEvent->delta() >0)
{
view->scale(scaleFactor,scaleFactor);
}
else
{
view->scale(1/scaleFactor,1/scaleFactor);
}
}
I want that the image should not zoom out after a certain extent. What should I do?
I tried setting the minimum size for QGraphicsView but that didn't help.
Thank You :)
Maybe something like this would help:
void MainWindow::wheelEvent(QWheelEvent *ZoomEvent)
{
view->setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
static const double scaleFactor = 1.15;
static double currentScale = 1.0; // stores the current scale value.
static const double scaleMin = .1; // defines the min scale limit.
if(ZoomEvent->delta() > 0) {
view->scale(scaleFactor, scaleFactor);
currentScale *= scaleFactor;
} else if (currentScale > scaleMin) {
view->scale(1 / scaleFactor, 1 / scaleFactor);
currentScale /= scaleFactor;
}
}
The idea, as you can see, is caching the current scale factor and do not zoom out in case of it smaller than some limit.
Here is one more implementation idea in which the current zoom factor is obtained from the transformation matrix for the view:
void View::wheelEvent(QWheelEvent *event) {
const qreal detail = QStyleOptionGraphicsItem::levelOfDetailFromTransform(transform());
const qreal factor = 1.1;
if ((detail < 10) && (event->angleDelta().y() > 0)) scale(factor, factor);
if ((detail > 0.1) && (event->angleDelta().y() < 0)) scale((1 / factor), (1 / factor));
}
Another way to solve the problem:
void GraphWidget::wheelEvent(QWheelEvent *event)
{
int scaleFactor = pow((double)2, - event->delta() / 240.0);
qreal factor = transform().scale(scaleFactor, scaleFactor).mapRect(QRectF(0, 0, 1, 1)).width();
if (factor < 0.5 || factor > 20)
return;
scale(scaleFactor, scaleFactor);
}
I try to lock mouse cursor movements to the left half of the screen. I have following screen setup:
On the left side is a Qt window of size 1120x1080, on the right side a GL window of size 800x1080.
I use Openbox window manager under Ubuntu 12.10. The window layout stays fixed.
I need to restrict mouse movement to the Qt window.
To get the mouse to stay in the window, enable mouse movement with:
setMouseTracking(true);
and override void QWidget::mouseMovement( QMouseEvent * event )
void TheWindow::mouseMoveEvent ( QMouseEvent * event )
{
// get window size without frame
QRect s = geometry();
// get current cursor position
int x = event->globalX();
int y = event->globalY();
bool reset = false;
// Check cursor position relative to window
if (event->x() < 0)
{
x -= event->x();
reset = true;
}
else if (event->x() >= s.width())
{
x += s.width() - event->x() - 1;
reset = true;
}
if (event->y() < 0)
{
y -= event->y();
reset = true;
}
else if (event->y() >= s.height())
{
y += s.height() - event->y() - 1;
reset = true;
}
// if reset needed move cursor
if (reset) QCursor::setPos(x,y);
}
this involving QGraphicsItem::itemChange(). If you have an item which you want to restrict to a certain area then reimplement itemChange() for that item and monitor QGraphicsItem::ItemPositionHasChanged changes to see whether the items wants to be placed outside your area of interest and prevent that by returning a position from inside that area. for example:
QVariant QGraphicsItem::itemChange(GraphicsItemChange change, const QVariant &value)
{
switch (change) {
case ItemPositionHasChanged:
if(x() < -200 || y() < -200 || x() > 200 || y() > 200)
setPos(0, 0);
graph->itemMoved();
break;
default:
break;
};
return QGraphicsItem::itemChange(change, value);
}
I have a scene which has fixed dimensions from (0;0) to (481;270):
scene->setSceneRect(0, 0, 481, 270);
Inside of it, I have a custom GraphicsItem and I can move it thanks to the flag ItemisMovable, but I would like it to stay within the Scene; I actually mean I don't want it to have coordinates neither under (0;0) nor over (481;270).
I tried several solutions like overriding QGraphicsItem::itemChange() or even QGraphicsItem::mouseMoveEvent() but I still cannot manage to reach what I want to do.
What is the suitable solution for my needs? Do I use QGraphicsItem::itemChange() badly?
Thanks in advance.
You can override QGraphicsItem::mouseMoveEvent() like this:
YourItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
QGraphicsItem::mouseMoveEvent(event); // move the item...
// ...then check the bounds
if (x() < 0)
setPos(0, y());
else if (x() > 481)
setPos(481, y());
if (y() < 0)
setPos(x(), 0);
else if (y() > 270)
setPos(x(), 270);
}
This code keeps your complete item in scene. Not only the upper left pixel of your item.
void YourItem::mouseMoveEvent( QGraphicsSceneMouseEvent *event )
{
QGraphicsItem::mouseMoveEvent(event);
if (x() < 0)
{
setPos(0, y());
}
else if (x() + boundingRect().right() > scene()->width())
{
setPos(scene()->width() - boundingRect().width(), y());
}
if (y() < 0)
{
setPos(x(), 0);
}
else if ( y()+ boundingRect().bottom() > scene()->height())
{
setPos(x(), scene()->height() - boundingRect().height());
}
}
Warning: The suggested solutions won't work for multiply selected items. The problem is, only one of the items receives a mouse move event in that case.
Actually, the Qt Documentation on QGraphicsItem provides an example which exactly solves the problem of limiting the movement of items to the scene rect:
QVariant Component::itemChange(GraphicsItemChange change, const QVariant &value)
{
if (change == ItemPositionChange && scene()) {
// value is the new position.
QPointF newPos = value.toPointF();
QRectF rect = scene()->sceneRect();
if (!rect.contains(newPos)) {
// Keep the item inside the scene rect.
newPos.setX(qMin(rect.right(), qMax(newPos.x(), rect.left())));
newPos.setY(qMin(rect.bottom(), qMax(newPos.y(), rect.top())));
return newPos;
}
}
return QGraphicsItem::itemChange(change, value);
}
Note I: You'd have to enable the QGraphicsItem::ItemSendsScenePositionChanges flag:
item->setFlags(QGraphicsItem::ItemIsMovable
| QGraphicsItem::ItemIsSelectable
| QGraphicsItem::ItemSendsScenePositionChanges);
Note II: If you only want to react on finished movement, consider using the GraphicsItemChange flag ItemPositionHasChanged