I was looking for any solution for this problem, but nothing found.
I have something like this:
Those rectangles are my objects. I want to make them selectable - when I click on red rectangle I want to see that this one is selected. If I have those objects saved in QList, can I select exactly that rectangle that I clicked on, and i.e edit it's preferencies?
How to refer to rectangle that I selected?
If you are using a QGraphicsScene and QGraphicsItems/Objects, you can call "QGraphicsItem::setFlags(QGraphicsItem::ItemIsSelectable)" on your QGraphicsItem and then in your QGraphicsItem::paint(..) method check if the option->state is set to QStyle::State_Selected, drawing different properties in this case. If you want a good example of how to do it, i recommend you to read third part of the chapter 8 in the "C++ GUI Programming with Qt, second edition" book.
Related
Good day to all!
I would like to learn from the respected community how it is possible using Qt Designer to create a simple GUI that performs what is shown in the attached image. Namely: after a single click of the LMB, a marker is placed at the place of the click, indicating the beginning of the polygon, and a temporary polygon of the desired type (but of different sizes) begins to follow the mouse cursor until we click on the LMB again, after which the final polygon will be built from the point of the first click of the LMB to the point of the second click. Such a ready-made polygon will have to be stored somewhere in memory for further work with it.
As a polygon here, I show a complex sector built on some calculated points, but as a simple example, you can take a straight line - I don't think that the essence of the program changes much.
I have already looked at many examples of different implementations of different things on QGraphicsScene, but I could not figure out exactly how to create an object in the way I needed. That is, I know that we need a separate class describing the polygon and calculating the coordinates of which it consists, but I don't quite understand how to implement the dynamics - with each mousemoveivent, delete the temporary polygon and draw a new one for the new coordinates, or how?
P.S. If it won't be so difficult, could someone also show how to implement what was conceived through the redefined paintScene class, replacing the standard QGraphicsScene class and inheriting from it? I am faced with the fact that when creating a custom class of the scene object, clicking on the objects attached to it is ignored by the program, and instead of, for example, dragging an object on the scene when clicking on it, the mousePressEvent of the scene, not the object, is triggered, and I do not understand what the problem is.
P.P.S. I apologize for my English and thank everyone for any help!
I want to make a menu that will take an undetermined quantity of labels and spread them out horizontally so that 3 are visible on screen at once. When pressing left/right it will go to the next one, the one that is selected is always in the center of the screen horizontally with the other two on the left/right of the screen.
The problem is that I also want a smooth transition not just a replacement. They need to wrap endlessly.
Not sure where to begin, not finding examples on google.
The concept you are talking about was popularized by Apple under the name "Cover Flow".
There is a widget like that available under a permissive license here: https://code.google.com/p/pictureflow/
I take it you want something a bit simpler (only show three labels, less fancy 3D effect), but I assume this is a good starting point.
Another one is the PathView QML element:
http://qt-project.org/doc/qt-5/qml-qtquick-pathview.html#details
It is even closer to what you like to do, feature-wise. It is also available in Qt4 and there is a tutorial here: http://qt-project.org/doc/qt-4.8/declarative-modelviews-pathview.html
I'm making my own UI from scratch using OpenGL that is why I'm asking this and please don't make any discouragement as this is just a hobby project.
Currently, I'm stuck implementing how this scrollbars really work. In my current implementation, the content scrolls at the wrong step value as well as the thumb, meaning, I set the value manually like 1px step for each of them.
The structure of my scrollbar implementation is describe as follows:
I draw scrollbars i.e the main rectangle where the 3 button lies.
Those 3 buttons are, thumb, buttonBack and buttonNext.
All of them do the basic logic of scrollbars i.e when I click each one of them, they moved. But the whole part(scrollbar) don't know how to scroll contents
So what I did is: I make another object and I call it scrollarea
It has two scrollbars, vertical and horizontal scrollbar.
I made a function called scrollToX and scrollToY which
does what I named to them.
But the step values I set to them are
manually set up.
I try to google some scrollbar, scrollarea, scrollview or whatever you call to that scrollable rectangle thing, but all I see are implementation and I cannot find any guides how to build your own. I have no choice but to look at their implementation. I try my best to comprehend what they did but their implementation of how their whole UI structure is very different to mine, and I cannot find anything useful there.
So I ask again here if anybody can explain me well how to make a properly functional scrollbar.
Most specific things I'm really concerned of are:
How do I determine the thumb step value?
How do I determine the content step value?
All of these depend on your content -
Is it just an image ? If so, you only need to change the offset depending on the size of the image.
Is it a list of values like in Windows explorer ? Then you need to create a data structure first that contains all of it, and shows the content that fits within the window as it scrolls.
OpenGL does not fit into this discussion.
I want to create a slider which contain a different slider handle and i want to paint it according to slider handle position in the slider.
You could use QProxyStyle to ovrride drawComplexControl method - you will have to draw entire control on your own, as there is no separate flags in QStyle::ControlElement for parts of QSlider.
maybe you should look at this: http://doc.qt.io/qt-4.8/stylesheet-examples.html#customizing-qslider
If I understand you correctly, you want a slider that changes not only its position but also its appearance as you slide, right? For example, a mix of QDial and QSlider, ie. a slider with a turning knob.
If so, you will need to subclass either QSlider or QAbstractSlider (or QDial) and do the painting in your own paintEvent(). Note, however, that you will loose all style-awareness unless you care about that yourself (and that is an interesting topic in itself, see http://doc.qt.io/qt-4.8/style-reference.html for more info).
The Qt demos and examples, or the QSlider/QDial source code itself may serve as examples on how to overload a paintEvent().
I want to divide the application screen into parts like one part is fixed showing fixed controls & another one is variable which can be changed when user select something. Like in Qt Creator we are having the left side column always fixed & the content of center screen is changing when user is selecting something. I have attached the screen shot. How to do it. if any one is having any idea please help me.
When you speak of the Qt Creator you certainly mean the controls on the left and right. In my opinion, the best thing to implement that are QDockWidgets. Have a look at them in the docs and as Martin said, look at the examples, they are perfect to learn each of the layout and composing issues.
QDockWidgets can be made floatable (undock them from the main window as toolboxes), they can have fixed sides to be docked on and it's easy to use them, because they can be filled with every widget you like. I often use them when I show a file explorer in an application, for example. Just look at the examples and play with it.
If you just want to have QActions visible all the time for the user, you can use a QToolBar.
You normally start with a QMainWindow and then put other toolbars, controls, widgets etc inside that.
Check out the Qt examples that come with the SDK src