I would like to retain the ability of a user to zoom and drag a QGraphicsScene, thus I cannot simply lock the QGraphicsView.
However a user should not be able to drag a QGraphicsItem out of the scenes viewport. Therefore I am looking for a way to interrupt a MouseDragEvent without ignoring the DragMoveEvent (aka have the QGraphicsItem jump back to its origin point). I have tried to accomplish this behaviour using the releaseMouse()-function but that didn't work at all. Any suggestions?
Thanks!
When dealing with qt graphics scene view frame work and dragging, it is better to re-implement QGraphicsItemand::itemChange than dealing with mouse directly.
This is the function defined in header file:
protected:
virtual QVariant itemChange( GraphicsItemChange change, const QVariant & value );
Then in the function, you detect the position change, and return the new position as needed.
QVariant YourItemItem::itemChange(GraphicsItemChange change, const QVariant & value )
{
if ( change == ItemPositionChange && scene() )
{
QPointF newPos = value.toPointF(); // check if this position is out bound
{
if ( newPos.x() < xmin) newPos.setX(xmin);
if ( newPos.x() > xmax ) newPos.setX(xmax);
if ( newPos.y() < ymin ) newPos.setY(ymin);
if ( newPos.y() > ymax ) newPos.setY(ymax);
return newPos;
}
...
}
Something like this, you get the idea.
Related
I want to draw lines inside column that show possible connections between different signals(Further, I also want to make radiobuttons on them to choose what connections are active).
But now I have trouble that delegates allow me to SetItemDelegate only for all column or all row. So I can't just make different blocks of this lines like vertical line, corner lines, horizontal line and then paint them depending on data in cells. I attached an example image. What should I use to draw something like this?
Something like:
Define a new style, override drawPrimitive method and do custom painting?
Could you show me an example, please?
Lines example
What I have for now
My main code for creating rows with signals(I take them from .txt file for simulation for now):
int IPFilesize = IPfilespl.size();
ui->CompTab->setRowCount(IPFilesize);
for (int i = 0; i<IPFilesize; i++)
{
QWidget *ChBx = new QWidget();
QCheckBox *pCheckBox = new QCheckBox();
QHBoxLayout *pLayout = new QHBoxLayout(ChBx);
pLayout->addWidget(pCheckBox);
pLayout->setAlignment(Qt::AlignCenter);
pLayout->setContentsMargins(0,0,0,0);
ChBx->setLayout(pLayout);
ui->CompTab->setCellWidget(i, 0, ChBx);
//connect(ChBx,SIGNAL(clicked()),this,SLOT(checkboxClicked()));
}
for (int ii = 0; ii<IPFilesize; ii++)
{
ui->CompTab->setItem(ii, 2, new QTableWidgetItem(IPfilespl.at(ii)) );
//connect(ChBx,SIGNAL(clicked()),this,SLOT(checkboxClicked()));
}
ui->CompTab->setItemDelegateForColumn(1, new WireDelegateDown());
Header code
class WireDelegate: public QStyledItemDelegate { protected: void paint(QPainter* painter, const QStyleOptionViewItem& opt, const QModelIndex& index) const {
int x = opt.rect.x();
double y = opt.rect.y();
QPoint c = opt.rect.center();
double centerx = c.x();
double centery = c.y();
double r = opt.rect.right();
double width = opt.rect.width();
double height = opt.rect.height();
QPainterPath path;
path.addRect(centerx, centery-height/2, 5.0, height/2);
path.moveTo(0, 0);
path.addRect(centerx, centery, width/2, 5.0);
path = path.simplified();
painter->drawPath(path);
Your item delegate could be a subclass of QAbstractItemDelegate. Then you can set its type with a property like shapeType (or whatever you name it). Based on the shapeType, you can do internal painting stuff from within the reimplemented paint method.
void MyConnectionDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
const QModelIndex &index) const
{
if (m_shapeType == ShapeType::horizontalLine) {
//..... Your fancy drawings happens here based on shapetype
} else if (m_shapeType == ShapeType::verticalLine) {
.
.
.
As I see in the picture (your desired result) it's not going to be simple and it can get quite complicated to implement such behavior. You will have to calculate the width, height, position of lines, colors, dots, arrows, nodes, etc for each delegate. When you exactly know which entities should be drawn in each cell, painting them using QPainter is a simple task.
You might consider whether QTableView is getting in the way more than it helps you. The built-in widgets are fantastic, but often, I've found that when I need to venture outside the realm of what they were specifically designed to do, I end up spending more time working around them than I get benefit. I don't know the right solution for what you're doing, but if it were me, I'd explore writing my own view based on QAbstractItemView and then just doing my own custom painting for the whole thing.
The downside of doing that is that QTableView provides a lot of interaction support for you, so if the interaction is a big benefit to you, then you have to write your own as well. So it's a trade-off. It's also a possibility that the built-in interaction for QTableView also gets in the way of what you're trying to do. It can go either way.
Hello guys I need your help,
I'm creating a timeline like widget in Qt based on the QGraphics framework. My problem is to handle collisions of items (inherited from QGraphicsRectItem) in my Timeline tracks.
I use the itemChange() function to keep track of the collisions. To keep the items in the parent boundingRect I use the following code wich works like a charm
if (change == ItemPositionChange && scene())
if (thisRect.intersects(parentRect)) {
const QPointF offset(mapFromParent(thisRect.topLeft()));
QPointF newPos(value.toPointF());
if (snapToGrid) {
newPos.setX(floor(qMin(parentRect.right() - offset.x() - thisRect.width(),
qMax(newPos.x(), parentRect.left() / 2 - offset.x())) / (snapValue * pxPerSec(duration))) * snapValue * pxPerSec(duration));
}
else {
newPos.setX(qMin(parentRect.right() - offset.x() - thisRect.width(),
qMax(newPos.x(), parentRect.left() - offset.x())));
}
newPos.setY(parentItem()->boundingRect().height() * 0.1);
return newPos;
}
}
This stops the items immediately if they reach the left or right boundary of my timline tracks, even if I move the mouse outside my view/scene. It's like an invisible wall.
Now I want the same behaviour if one item in a track collides with another.
const QRectF parentRect(parentItem()->sceneBoundingRect());
const QRectF thisRect(sceneBoundingRect());
foreach (QGraphicsItem *qgitem, collidingItems()) {
TimelineItem *item = qgraphicsitem_cast<TimelineItem *>(qgitem);
QPointF newPos(value.toPointF());
if (item) {
const QRectF collideRect = item->sceneBoundingRect();
const QPointF offset(mapFromParent(thisRect.topLeft()));
if (thisRect.intersects(collideRect) && thisRect.x() < collideRect.x()) {
newPos.setX(collideRect.left() - offset.x() - thisRect.width());
}
if (thisRect.intersects(collideRect) && thisRect.x() > collideRect.x()) {
newPos.setX(collideRect.right() + offset.x());
}
}
newPos.setY(parentItem()->boundingRect().height() * 0.1);
return newPos;
}
The problem is that if I move an item via mouse against another item you see them intersecting/overlapping and then the item I moved snaps back to the minimum not intersecting distance. How do I manage to stop the moving item immediately if it hits another (no trembling forth and back movement intersecting thing). Just like the way the items are kept in parents boundingRect (first code block), the invisible wall like behaviour?
I think the problem here is with "thisRect". If you're calling this from an ItemPositionChange, then sceneBoundingRect is returning the bounding rectangle of the item in its previous position, not the new one. What happens is that the current position succeeds even though though there's a collision, but the next one fails because you're always checking the previous results, and then it snaps back to avoid the collision.
After getting the local item's scene rectangle, you'll need to translate it to the new future position of the item:
QPointF new_pos (value.toPointF ());
QRectF thisRect (sceneBoundingRect());
thisRect.translate (new_pos - pos());
I've moved the creation of "new_pos" outside the loop so that it's available for the rectangle translation. It's also faster.
I created my own classes (view and scene) to display image and objects I added to it, even got zoom in/out function implemented to my view, but now I have to add new functionality and I don't even know how to start looking for it.
Whenever I press the scroll button of my mouse and hold it - I wish to move around the scene, to see different parts of it - just like I would with sliders. It is supposed to be similar to any other program allowing to zoom in/out to image and move around zoomed picture to see different parts of it.
Unfortunately - I don't even know how to look for some basic, because "moving" and similar refer to dragging objects around.
EDIT 1
void CustomGraphicView::mouseMoveEvent(QMouseEvent *event)
{
if(event->buttons() == Qt::MidButton)
{
setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
translate(event->x(),event->y());
}
}
Tried this - but it is working in reverse.
I suppose you know how to handle events using Qt.
So, to translate (move) your view use the QGraphicsView::translate() method.
EDIT
How to use it:
void CustomGraphicsView::mousePressEvent(QMouseEvent* event)
{
if (e->button() == Qt::MiddleButton)
{
// Store original position.
m_originX = event->x();
m_originY = event->y();
}
}
void CustomGraphicsView::mouseMoveEvent(QMouseEvent* event)
{
if (e->buttons() & Qt::MidButton)
{
QPointF oldp = mapToScene(m_originX, m_originY);
QPointF newP = mapToScene(event->pos());
QPointF translation = newp - oldp;
translate(translation.x(), translation.y());
m_originX = event->x();
m_originY = event->y();
}
}
I'm building a very simple image editor on Qt creator.I have my image displayed on a QGraphicsView and i want to give the user the ability to zoom in and out by a pushbutton.
I've searched a lot and found how to zoom in and out through the mouse wheel.As i am very new to Qt i can't adjust it to the pushbutton because i don't understand everything clearly.
I' ve tried this(without understanding completely what i'm doing)but the result isn't the wanted.It zooms in only once and quite abruptly.I want a smoother zoom and as many times as i want.
void MainWindow::on_pushButton_clicked(){
QMatrix matrix;
ui->graphicsView->setTransformationAnchor(QGraphicsView::AnchorViewCenter);
matrix.scale(1.0,1.0);
ui->graphicsView->setMatrix(matrix);
ui->graphicsView->scale(1,-1);
}
I would be very grateful if you guys can help
Below is how I implemented zooming in my subclass of QGraphicsView. Note that you'd need to pass in different values of "zoom" to get different magnifications as the zoom factor is an absolute value, not a relative one.
(The optMousePos argument can be set to point to a QPoint indicating the spot that should be the central-point of the zoom transformation, or it can be left NULL if you don't care about that. I use it because I zoom in and out based on the user turning the wheel in his mouse, and when doing that, the user usually wants to zoom in towards the point where his mouse point is currently positioned, rather than in towards the center of the graphics area)
qreal _zoom = 0.0;
[...]
void MyQGraphWidgetSubclass :: SetZoomFactor(qreal zoom, const QPoint * optMousePos)
{
if ((zoom != _zoom)&&(zoom >= 0.02f)&&(zoom <= 1000000.0f))
{
QPointF oldPos;
if (optMousePos) oldPos = mapToScene(*optMousePos);
// Remember what point we were centered on before...
_zoom = zoom;
QMatrix m;
m.scale(_zoom, _zoom);
setMatrix(m);
if (optMousePos)
{
const QPointF newPos = mapFromScene(oldPos);
const QPointF move = newPos-*optMousePos;
horizontalScrollBar()->setValue(move.x() + horizontalScrollBar()->value());
verticalScrollBar()->setValue(move.y() + verticalScrollBar()->value());
}
}
}
void MyQGraphWidgetSubclass :: wheelEvent(QWheelEvent* event)
{
QPoint pos = event->pos();
SetZoomFactor(_zoom*pow(1.2, event->delta() / 240.0), &pos);
event->accept();
}
I have in my UI one QScrollArea with an image, and I want to get some value when I click on the image.
Being more explict, I need to change the brightness of an image, and I will get the value with the mouse. I already see the MouseMoveEvent but I don't know how to use it.
If I get the position of the mouse when I click and drag, I can extract one value to change the bright of my image, that I know. I just don't know how I will get the position.
Does anyone know how I can do this?
Ps.: My QScrollArea was created on Design, so I don't have any code writed by me with the specifications of the QScrollArea.
there is a small correction . when i programmed like this i was getting the movements a liitle jerky . so i tried to modified the code and now working perfect .
heres how i changed
const int deltaX = event->scenePos().x() - m_lastClickPosition.x();
if ( deltaX > 10 )// to the right
{
moveBy(10,0);
m_lastClickPosition = event->scenePos();
}
else if ( deltaX <-10 )
{
moveBy(-10,0);
m_lastClickPosition = event->scenePos();
}
All the information you need is in the QMouseEvent object that is sent to the mouseMoveEvent handler of your widget.
QMouseEvent::buttons()
QMouseEvent::pos()
A simple way to do what you're after is to change the brightness of the image whenever you receive a "mouse movement event" and the QMouseEvent object reports a button down (this means the user is moving the mouse while holding down a button).
void MyWidget::mousePressEvent( QMouseEvent* event )
{
if ( event->button() == Qt::LeftButton )
{
// Keep the clicking position in some private member of type 'QPoint.'
m_lastClickPosition = event->pos();
}
}
void MyWidget::mouseMoveEvent( QMouseEvent* event )
{
// The user is moving the cursor.
// See if the user is pressing down the left mouse button.
if ( event->buttons() & Qt::LeftButton )
{
const int deltaX = event->pos().x() - m_lastClickPosition.x();
if ( deltaX > 0 )
{
// The user is moving the cursor to the RIGHT.
// ...
}
else if ( deltaX < 0 ) // This second IF is necessary in case the movement was all vertical.
{
// The user is moving the cursor to the LEFT.
// ...
}
}
}