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();
}
}
Related
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'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();
}
Disclaimer: I am pretty much a beginner with QT.
I've been struggling for some time to rotate a QGraphicsView (no 3D rotation) but, despite what i do, it doesn't work. I have tried:
QTransform transform;
transform.rotate(45);
ui->graphicsView->setTransform(transform);
or more simply:
ui->graphicsView->rotate(45);
These seem like very straightforward ways to do it that should work, but for some reason, whenever i run it, the QGraphicsView doesn't rotate at all. If possible, i'd like some direct and easy to understand code snippets, and/or what i'm doing wrong.
EDIT: This is the code in the widget cpp file i have problems with. It should be a simple timer with an animated hourglass icon. It gets repeated every .5 seconds.
void Widget::timerEvent(QTimerEvent *event)
{
++timeFlag;
++timerFlag;
if (timerFlag < 115){
animateTimer = QString("\":/new/100/timerFrames/timerIconFrame%1.png\"").arg(timerFlag);
QPixmap pix(animateTimer);
pixmapitem.setPixmap(pix);
scene.addItem(&pixmapitem);
ui->graphicsView_2->setScene(&scene);
}
if (timerFlag >= 115 && timerFlag < 119){
//
}
if(timerFlag == 119){
ui->graphicsView_2->setStyleSheet("border-image:url(:/new/100/timerIconPix.PNG);border:0px;}");
}
if(timerFlag == 120){
timerFlag = 0;
}
if (timeFlag==2){
timeFlag = 0;
if(sec>=10){
ui->label_2->setText(QString("%1:%2").arg(min).arg(sec));
} else {
ui->label_2->setText(QString("%1:0%2").arg(min).arg(sec));
}
++sec;
if (sec == 60) {
sec = 0;
++min;
}
}
}
You're merely decorating the QGraphicsView using the style mechanism. You could have used a plain QWidget instead, since you don't use any graphics view functionality. None of the images in the stylesheet are what the view actually displays. The image must be on the scene displayed by the view.
Set the image on a QGraphicsPixmapItem, add that item to a scene, set the scene on the view, and then the transformations will work. You can then keep replacing the pixmap in the timer handler.
Finally, you must also check the timer id in the timerEvent. I assume that you're using a QBasicTimer, say called m_timer, you'd then check as follows:
void Widget::timerEvent(QTimerEvent * ev) {
if (ev->timerId() != m_timer.timerId()) return;
... // rest of the code
}
As you can see, the code that you've not included in the original question was absolutely essential! Without it, the question was wholly off-topic.
You need to implement a QGraphicsView, a QGraphicsScene and then add something that inherits from QGraphicsItem to that scene to rotate.
Here is an example that rotates a QWidget in a QGraphicsView:
QGraphicsView* view = new QGraphicsView(parent);
QGraphicsScene* scene = new QGraphicsScene(view);
view->setScene(scene);
// Widget to rotate - important to not parent it
QWidget* widget = new QWidget();
QProxyWidget proxy_widget = scene_->addWidget(widget);
QPropertyAnimation* animation = new QPropertyAnimation(proxy_widget, "rotation");
animation->setDuration(5000);
animation->setStartValue(0);
animation->setEndValue(360);
animation->setEasingCurve(QEasingCurve::Linear);
animation->start(QAbstractAnimation::DeleteWhenStopped);
I have a custom class derived from QGraphicsView that implements a slot call scrollHorizontal(int dx), inside the code is simply
void CustomView::scrollHorizontal(int dx){
scrollContentsBy(dx, 0);
}
My problem is, scrolling like this works but doesn't update the scene properly, instead any pixels found on the edge of the view are repeated instead of having a fresh call to the item's paint() method.
I've attempted calling update() after, but nothing happens. I tried enabling scrolling by dragging and updates work fine! But I need it done programmatically, and since I have the scroll bars hidden things like horizontalScrollBar()->setValue() do not scroll the view.
I also tried :
scrollContentsBy(dx, 0);
this->scene()->invalidate(sceneRect());
this->update();
update:
QPointF center = mapToScene(viewport()->rect().center());
centerOn(center.x() - dx, center.y());
update();
is working, but now my top view is scrolling slower than my bottom view, which is a new problem. They are linked with signals and slots, in the bottom view i have scrollContentsBy(int dx, int dy) overrided to emit horizontalScroll(dx); which is caught by the above slot in the top view.
Any ideas why the scrolls happen at different rates? Might it have something to do with the scroll bars being a part of the bottom view effectively making it a "smaller" window?
update 2:
The different scroll rates seems to stem from some rounding happening to give me an integer based "center" using mapToScene(viewport()->rect().center()); , as you scroll and the slower you scroll the more this error adds up, the faster you scroll the less total error.
Is there a way for me to get around this? I don't see any way to get a floating point center point.
update 3:
So I have this mostly solved, turns out the mapToScene was needed(code I found elsewhere on the web).
I fixed this by storing QPointF of FP calculated center of the viewport, now the amount of error when scrolling the two views is unnoticeable.
The final issue is, the views no longer line up when you scroll ANY amount to the right, and then resize the window then scroll again. I assume this has something to do with the logical ordering of when the center point is calculated and when the centering happens.
Right now I use the following code snippet in QGraphicsScene::ResizeEvent() and elsewhere that updates the center as needed
QRectF viewPort(viewport()->rect());
QPointF rectCenter((viewPort.x() + viewPort.x() + viewPort.width())/2.0, (viewPort.y() + viewPort.y() + viewPort.height())/2.0);
viewCenter = rectCenter;
and my horizontalScroll(int dx) slot
void CustomView::horizontalScroll(int dx)
{
viewCenter.setX(viewCenter.x() - dx);
centerOn(viewCenter.x(), viewCenter.y());
update();
}
How can I fix the issue when re-sizing the window breaking the alignment of the two views? If any more clarification is needed please just ask, I can try to give skeletons of what I'm referring to if need be.
Update 4:
Rough code Skeleton
Class HeaderView:
class HeaderView View : public QGraphicsView
{
Q_OBJECT
public:
HeaderView(QWidget * parent = 0);
HeaderView(QGraphicsScene * scene, QWidget * parent = 0);
private:
QPointF viewCenter;
protected:
void resizeEvent ( QResizeEvent * event );
public slots:
void horizontalScroll(int);
void addModel(qreal, qreal, const QString&);
};
HeaderView.cpp
void HeaderView::resizeEvent(QResizeEvent *event)
{
QGraphicsView::resizeEvent(event);
QRectF viewPort(viewport()->rect());
QPointF rectCenter((viewPort.x() + viewPort.x() + viewPort.width())/2.0, (viewPort.y() + viewPort.y() + viewPort.height())/2.0);
viewCenter = rectCenter;
}
void HeaderView::horizontalScroll(int dx)
{
viewCenter.setX(viewCenter.x() - dx);
centerOn(viewCenter.x(), viewCenter.y());
update();
}
Class EventView:
class EventView : public QGraphicsView
{
Q_OBJECT
public:
EventView(QWidget * parent = 0);
EventView(QGraphicsScene * scene, QWidget * parent = 0);
QRectF visibleRect();
protected:
void scrollContentsBy ( int dx, int dy );
signals:
void horizontalScroll(int);
};
EventView.cpp
void EventView::scrollContentsBy(int dx, int dy)
{
QGraphicsView::scrollContentsBy(dx, dy);
if(dx != 0){
emit horizontalScroll(dx);
}
}
Somwhere in Class MainWindow:
connect(eventView, SIGNAL(horizontalScroll(int)), headerView, SLOT(horizontalScroll(int));
I've worked with QGraphicsView in Qt 4.6.3 - 4.7.2 and have to argue that you can use the respective QScrollBar in the following way:
//graphics view initialization
QGraphicsView *graphicsView = new QGraphicsView(parent);
QGraphicsScene *scene = new QGraphicsScene(0,0,widthOfScene,heightOfScene,parent);
graphicsView->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
graphicsView->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
graphicsView->setScene(scene);
//in another method
QScrollBar* yPos=graphicsView->verticalScrollBar();
yPos->setValue((int) newValue);
It does not matter if they are hidden or not. They will still respond to setValue(int) as long as you have a graphics scene that is larger than the graphics view.
The QGraphicsView will also respond to ensureVisible, which moves the scrollbars to the appropriate location.
You are not supposed to call scrollContentsBy as explained here: http://qt-project.org/doc/qt-4.8/qabstractscrollarea.html#scrollContentsBy
I don't know if you can still call the hidden scrollbar to scroll it. If not, translate is an option.
Did you try to use the scroll bars? Hiding them doesn't make them non-existent, and the documentation says you should use QScrollBar::setValue to scroll to a given position.
Another option would be to use QGraphicsView::centerOn(QPointF) in conjunction with the current center point -- as you've also tried -- but directly calculating the center point within your method (do not precalculate and store the center point), by using QGraphicsView::mapToScene(int,int):
void CustomView::horizontalScroll(int dx)
{
QPointF viewCenter = mapToScene(width() / 2, height() / 2);
viewCenter += QPointF(dx, 0); // Why did you subtract instead of add dx?
centerOn(viewCenter); // BTW, you don't need to do .x(), .y()
// You can remove update(); as this is already called in centerOn().
}
Please note that if you have, as you said, "scrollContentsBy(int dx, int dy) overrided to emit horizontalScroll(dx)", you also have to call the super class method so that the view can scroll itself:
void CustomView::scrollContentsBy(int dx, int dy)
{
emit horizontalScrolled(dx); // (You should call it different than the slot!)
QGraphicsView::scrollContentsBy(dx, dy); // <-- This is what I mean!
}
I have one question when infinite background scrolling is done, is the object remain fixed(like doodle in doodle jump, papy in papi jump) or these object really moves.Is only background move or both (background and object )move.plz someone help me.I am searching for this solution for 4/5 days,but can't get the solution.So plz someone help me. And if object does not move how to create such a illusion of object moving.
If you add the object to the same layer as the scrolling background, then it will scroll as the background scrolls.
If your looking for an effect like the hero in doodle jump, you may want to look at having two or more layers in a scene.
Layer 1: Scrolling Background Layer
Layer 2: Sprite layer
SomeScene.m
CCLayer *backgroundLayer = [[CCLayer alloc] init];
CCLayer *spriteLayer= [[CCLayer alloc] init];
[self addChild:backgroundLayer z:0];
[self addChild:spriteLayer z:1];
//Hero stays in one spot regardless of background scrolling.
CCSprite *squidHero = [[CCSprite alloc] initWithFile:#"squid.png"];
[spriteLayer addChild:squidHero];
If you want objects to scroll with the background add it to the background layer:
//Platform moves with background.
CCSprite *bouncePlatform= [[CCSprite alloc] initWithFile:#"bouncePlatform.png"];
[backgroundLayer addChild:bouncePlatform];
Another alternative is to use a CCFollow action. You would code as if the background is static (which it will be) and the player is moving (which it will be), but add a CCFollow action to the player. This essentially moves the camera so that it tracks your player.
You can also modify the classes so that you can get the CCFollow action to follow with an offset (i.e., so the player is not in the middle of the screen) as well as to have a smoothing effect to it, so that when the player moves, the follow action is not jerky. See the below code:
*NOTE I am using cocos2d-x, the c++ port. The methods are similar in cocos2d, and you should be able to modify these to fit the cocos2d syntax. Or search around -- I found these for cocos2d and then ported to c++.
//defines the action to constantly follow the player (in my case, "runner.p_sprite is the sprite pointing to the player)
FollowWithOffset* followAction = FollowWithOffset::create(runner.p_sprite, CCRectZero);
runAction(followAction);
And separately, I have copied the class definition for CCFollow to create my own class, CCFollowWithAction. This also has a smoothing effect (you can look this up more online) so that when the player moves, the actions are not jerky. I modified "initWithTarget," to take into account an offset, and "step," to add a smoothing action. You can see the modifications in the comments below.
bool FollowWithOffset::initWithTarget(CCNode *pFollowedNode, const CCRect& rect/* = CCRectZero*/)
{
CCAssert(pFollowedNode != NULL, "");
pFollowedNode->retain();
m_pobFollowedNode = pFollowedNode;
if (rect.equals(CCRectZero))
{
m_bBoundarySet = false;
}
else
{
m_bBoundarySet = true;
}
m_bBoundaryFullyCovered = false;
CCSize winSize = CCDirector::sharedDirector()->getWinSize();
m_obFullScreenSize = CCPointMake(winSize.width, winSize.height);
//m_obHalfScreenSize = ccpMult(m_obFullScreenSize, 0.5f);
m_obHalfScreenSize = CCPointMake(m_obFullScreenSize.x/2 + RUNNER_FOLLOW_OFFSET_X,
m_obFullScreenSize.y/2 + RUNNER_FOLLOW_OFFSET_Y);
if (m_bBoundarySet)
{
m_fLeftBoundary = -((rect.origin.x+rect.size.width) - m_obFullScreenSize.x);
m_fRightBoundary = -rect.origin.x ;
m_fTopBoundary = -rect.origin.y;
m_fBottomBoundary = -((rect.origin.y+rect.size.height) - m_obFullScreenSize.y);
if(m_fRightBoundary < m_fLeftBoundary)
{
// screen width is larger than world's boundary width
//set both in the middle of the world
m_fRightBoundary = m_fLeftBoundary = (m_fLeftBoundary + m_fRightBoundary) / 2;
}
if(m_fTopBoundary < m_fBottomBoundary)
{
// screen width is larger than world's boundary width
//set both in the middle of the world
m_fTopBoundary = m_fBottomBoundary = (m_fTopBoundary + m_fBottomBoundary) / 2;
}
if( (m_fTopBoundary == m_fBottomBoundary) && (m_fLeftBoundary == m_fRightBoundary) )
{
m_bBoundaryFullyCovered = true;
}
}
return true;
}
void FollowWithOffset::step(float dt)
{
CC_UNUSED_PARAM(dt);
if(m_bBoundarySet){
// whole map fits inside a single screen, no need to modify the position - unless map boundaries are increased
if(m_bBoundaryFullyCovered)
return;
CCPoint tempPos = ccpSub( m_obHalfScreenSize, m_pobFollowedNode->getPosition());
m_pTarget->setPosition(ccp(clampf(tempPos.x, m_fLeftBoundary, m_fRightBoundary),
clampf(tempPos.y, m_fBottomBoundary, m_fTopBoundary)));
}
else{
//custom written code to add in support for a smooth ccfollow action
CCPoint tempPos = ccpSub( m_obHalfScreenSize, m_pobFollowedNode->getPosition());
CCPoint moveVect = ccpMult(ccpSub(tempPos,m_pTarget->getPosition()),0.25); //0.25 is the smooth constant.
CCPoint newPos = ccpAdd(m_pTarget->getPosition(), moveVect);
m_pTarget->setPosition(newPos);
}
}