qgraphicsscene

问题 I have a little problem with the Qt class QGraphicsScene : To detect the current mouse coordinates I made a new class QGraphicsScenePlus with QGraphicsScene as the base class. I have already redefined the slot function mouseMoveEvent(QGraphicsSceneMouseEvent* event) and the received coordinates seem to be correct. Now I want to notify the parent QMainWindow class, where the QGraphicsScenePlus object is stored, whenever the mouse coordinates change. What is the best way to do this? I already

问题 It's simple to draw line or ellipse just by using scene.addellipse(), etc. QGraphicsScene scene(0,0,800,600); QGraphicsView view(&scene); scene.addText("Hello, world!"); QPen pen(Qt::green); scene.addLine(0,0,200,200,pen); scene.addEllipse(400,300,100,100,pen); view.show(); now what should i do to set some pixel color? may i use a widget like qimage? by the way performance is an issue for me.thanks 回答1: I think that performing pixel manipulation on a QImage would slow down your application

问题 I am creating some images rendering the contents of a QGraphicsScene . My project requirement is that it should handle a canvas size of 10 ft by 8 inches. On screen, and scene size, that is 8640 x 576 pixels. I can render it fine. The thing is, the output images need to have 300 resolution. That means, the rendered image will have a width of 36000, which is over 2^15 - 1 = 32767 pixels..... The output is clipped - in the code below, I would get a QImage of correct expected size (36000) but

问题 I want to stop labels colliding within my Scene and as a result used this code to check for a collision:- QGraphicsTextItem *textLabel = new QGraphicsTextItem; .... addItem(textLabel); //check for collision QList<QGraphicsItem*> items = this->items(textLabel>boundingRect(),Qt::IntersectsItemBoundingRect); I never get any items in the list, yet on screen I can see the collisions. Am I reading the documentation incorrectly? 回答1: You're checking if any items are colliding with the label's

问题 I use a QPainter to draw my widget with this code: QPen pen(Qt::black, 0.6, Qt::SolidLine); QPainter painter(this); painter.setPen(pen); // vertical painter.drawLine(startX,0,startX,50); painter.drawLine((startX += grid),0,startX,50); painter.drawLine((startX += grid),0,startX,50); painter.drawLine((startX += grid),0,startX,50); painter.drawLine((startX += grid),0,startX,50); painter.drawLine((startX += grid),0,startX,50); // horizontal pen.setWidth(0.7); painter.setPen(pen); painter.drawLine

问题 I have subclassed a qgraphicsscene and trying to get the mouse coords inside a "normal" function. I only get it working on "mouse involved" function. Sorry I'm amateur programmer. For exmample here scenePos() works: void mousePressEvent(QGraphicsSceneMouseEvent *event) { // qDebug() << "Custom scene clicked."; if(event->modifiers() == Qt::ControlModifier) { if(event->button() == Qt::LeftButton) { QPointF pos = {event->scenePos().x(), 70}; addChordnueve(pos); // crea 1 item at mouse x e y = 70

问题 I am trying to add some custom QGraphicsItems in a QGraphicsScene on mouse click and at mouse cursor coordinates. But the items are not added at the same coordinates as the mouse cursor's. renderArea::renderArea(QWidget *parent): QGraphicsView(parent) { scene = new QGraphicsScene(this); scene->setItemIndexMethod(QGraphicsScene::NoIndex); scene->setSceneRect(0, 0, 850, 480); setScene(scene); setCacheMode(CacheBackground); setViewportUpdateMode(BoundingRectViewportUpdate); setRenderHint

问题 I have a QGraphicsScene and many selectable items. But when I click the right mouse button - deselects all objects. I want show menu and edit selected objects but have automatic deselect any time when right click at mouse... Perhaps the problem is that I have included an rubber selection. selection of objects in the end is how the right and the left mouse button when I pull the frame and therefore is reset at single time you press the right button... How to leave objects highlighted when you

问题 I'm using Qt (Mac, version 4.7) to rendering a rather large scene (map data from Open Street Maps) with QGraphicsView and QGraphicsScene. Everything works great until I try to set the Z value for the items in the scene. I've tried two separate approaches to do this. In one, I just do: QGraphicsPathItem *item = scene->addPath(path, pen); item->setZValue(z); and the other I create my own QGraphicsItem subclass, but get the exact same problem. The cause of the slow down appears to be on the Qt

问题 I have a QGraphicsScene and its associated QGraphicsView . I let the user create some shapes in the form of derived QGraphicsItem s into that scene. I also want them to be movable by mouse. Clicking one or more items select them, and moving them around while the mouse button is pressed works. I inherited QGraphicsView to do this, and overrided mousePressedEvent , mouseReleasedEvent & mouseMoveEvent to achieve this. When the user clicks, I am basically testing if an item (accessed through