Here I am again worrying about how to Zoom in and out a QGraphicsPixmapItem in a graphics scene. I looked for a direct method for this but could not find any in graphics scene or in pix map. Can someone help me with this. Do I have to extend QGraphicsPixmapItem and implement methods for this.
Thanks again for help and I really do appreciate it.
~Tharanga
setScale() changes the size of the item, not the view scale of the scene. For a one item scene, it's effectively the same. But if you have more than one item in the scene, it changes the relation between items.
QGraphicsView::setTransform() should be used if you want to keep the item's relationship to the scene and other items.
QGraphicsPixmapItem inherits from QGraphicsItem, so it has all of that class's methods.
In particular, there's setScale that will change the item's scale factor (i.e. "zoom" it).
Look at the Transformations Example page for how this is done, and other transformations you can do.
Related
I'm trying to draw a stacked bar graph on Qt, i followed the tutorial on the documentation but when i try to put the graph inside a QGraphicsView i get a lo of unused space and can't manage to make the scene fit the view.
My code is the same as the documentation one plus the following to make the scene show up in the view:
QGraphicsScene *scene = new QGraphicsScene(this);
scene->addWidget(chartView);
ui->view->setScene(scene);
And what i get is this
As you can see there is a lot of unused space and it makes the text disappear, i wanted to make the graph fit the view but i can't seem to find a way to do so.
I tried in many different ways using
ui->view->ensureVisible ( scene->sceneRect() );
ui->view->fitInView( scene->sceneRect(),Qt::KeepAspectRatio);
and
ui->view->setSceneRect(0,0,ui->view->frameSize().width(),ui->view->frameSize().height());
but nothing seems to work (the second solution just moves the graph to the top left)
As per the comment... the real issue is the basic sizing of chartView rather than anything to do with QGraphicsView or QGraphicsScene.
When a QWidget is added to a QGraphicsScene the resulting QGraphicsProxyWidget will generally honour the size hint and policy of that widget.
In addition, though, the QGraphicsScene will set the scene rect to the bounding rectangle of all scene items and the QGraphicsView will then position the scene according to whatever viewport anchor is in force. The end result can be visually misleading if the scene has a complex set of items or has a bounding rectangle smaller than that displayed within the GraphicsView.
So if a widget does look odd when added to a QGraphicsScene it's normally a good idea to test by just showing it as a top level window on the desktop and make sure it behaves as expected before going any further.
I've got a problem with my layout and I can't find any solution. Below are two images. The first one is from the Qt Designer, where everything looks great (but there is no QGraphicsScene, so it's expectable). The second one is real app, where the left bottom scene is too wide. As scene rect I'm taking this->ui->juliaMandelbrot->geometry(), which means geometry of the QGraphicsView. But this returns 640x150 instead of 225x150. What am I doing wrong?
Thank you.
although I don't like it, I set maximum width of graphics view and it solved my problem.
I don't like it, because the grandparent of my graphics view has already set maximum width, so I thought, that children inherit this property :-(.
How do we create a Arrow graphics item which gets displayed on a graphics scene?
My requirement is that I drag and drop a QGraphicsLineItem from one scene to another. Once the Line item is dropped on a scene, a Arrow graphics Item should display perpendicular to the line item dropped on the scene. I should be able to display the Arrow Item on either side of the line. Currently I am able to drop a Line item onto the scene. I need source code for creation of an Arrow item.
Can somebody please help me with this scenario?
There are two possible options here. One is to have an image that you load into a QGraphicsPixmapItem and position and rotate it as desired.
The better method would be to create a class inherited from QGraphicsItem, and draw the arrow in its paint method, with the calls to drawLine.
When you inherit from QGraphicsItem, make sure that you overload the boundingRect() function, as well as the paint() function.
I have a QGraphicsRectItem over a scene. I intend to drag and drop this window over the scene. When the rect item reaches the left boundary end I have to show it appearing from the right end. Currently I am using two objects and hiding and showing them by calculating the boundary of scene which involves lot of calculations.
Is there any better way to achieve the same effect using just a single object?
Thank You
You could use a single item that spans the entire scene, and draw the rectangle (or 2 parts of it) in it's paint method.
But then you would lose the optimization of the BSP tree, your item would redraw even if some unrelated area repaints. If this is just 1 item, I guess it would not have much impact.
You would need to implement your own dragging with mousemove event and the like, though this is not much code, you just need to get it right.
I am creating a component that will be a large plus or a large minus. I don't want to use a bitmap because even I can draw this using the Graphics class, but the component must be clickable (the Shape class is not).
It will be part of an item renderer, so I want it to be as light-weight as possible. UIComponent does not seem to sent CLICK messages.
Thanks for any ideas
I would suggest creating a Sprite object and drawing the minus and plus arrows to its graphics object. You'll then have to addEventListener(MouseEvent.CLICK, someFunction); in its constructor or wherever else you'll need it.
You may also want to set cacheAsBitmap to true at that point, so that it's not redrawn every frame.
EDIT: Per #jeremynealbrown you have to use the SpriteAsset class if you are working in Flex, apparently. Very similar, but another 2 levels of abstraction are added.
If you look here:
UIComponent Docs
You will see that UIComponent has InteractiveObject in its inheritance path. InteractiveObject is the class that adds mouse event functionality.
UIComponent will actually dispatch click events. However, if there is no content drawn to the graphics, the UIComponent will have no area that can be clicked. If the plus or minus icon you draw is too small to reliably catch mouse activities, then draw a fully-transparent rectangle to increase the hit area.