QStackedWidget and adding new QGraphicsView to its pages

[newToQt26]

Hey everyone !
This is my first post here.. I am fairly new to Qt. I have been trying to develop a paint like application. All the basic features and user interface is pretty much ready. I am stuck with the functionality of layers.

Basically , I have to create layers like the one in photoshop. I should be able to add , remove layers on clicking buttons/menu. I should be able to draw rectItems on each layer and apply different properties on each layer .
For the same purpose I need stacked Widget, mapped to a Tree view , and with every new page added , I need a new View and Scene to be displayed. I am able to add new pages to StackedWidget , and add the view to it. But the problem is every new page is not showing its own view. Its like they are sharing the same view. I want the view of 1st page to hold its own contents and view of 2nd page to have its own contents.

I have derived custom View and Scene classes from QGRaphicsView and QGraphicsScene respectively. Also by clicking the item in QTreeView, the corresponding stackedPage should be displayed .
I am attaching screenshot of my application for better understanding. !

Can anyone help me build the idea? Or help me with implementing this?
Sorry for such a long description. Just a newbie trying to explain the problem.

Thank you for reading :)

[mrjj]

Hi
we like long good descriptions here :)
I'm not 100% sure how layers would work with a QStackedWidget as then each layer would be like its own
document and not draw on top of each other.

Did you see QGraphicsItemGroup ?
You could use that for layers as you can then hide/show all items that is on a layer.
https://stackoverflow.com/questions/18074798/layers-on-qgraphicsview

In any case, if you want like separate documents, then show how you add the new
QGraphicsView and QGraphicsScene to a new page.
It should work fine but something must be up if that is not what you are getting.

[newToQt26]

Hey !
Thanks for replying . I was thinking to make the stackedWidget transparent , that way I can see the items on every layer .. I am not sure about QGraphicsItemGroup , but I'll check that out !

As of now, I added another Qt designer Form class (DrawingBoard) , in which I set up my GraphicsView and Scene , and then in mainWindow.cpp in the Add layer fucntion:

ui->stackedWidget->addWidget(new DrawingBoard);

which works fine ! I get a new fresh view & scene everytime I add a layer . But the new problem is , all my Menu and actions and functionalities are in mainwindow.cpp ! They dont seem to work with the selections in subsequent pages added via above code.

pen properties,brush properties, zoom , backgroundcolor , undo/redo , everything works just with the 1st view , which has been set up in mainWindow.cpp:

scene = new Scene(this);
    scene->setSceneRect(-800,-400,1600,800);
view = new View(this);
    view->setScene(scene);

So , now I dont know how to make all the new Views & scenes accessible to mainWindow tools.

For example, I have pasted the part of the mainwindow.cpp code here:

void MainWindow::on_penWidthSpinBox_valueChanged(int arg1)
{
    scene->setPenWidth(arg1);

}

void MainWindow::on_fillColorButton_clicked()
{

    QColor color = QColorDialog::getColor(Qt::cyan,this);
    if(color.isValid()){
        QString fillcolorQss= QString("Background-color : %1").arg(color.name());
        ui->fillColorButton->setStyleSheet(fillcolorQss);
        scene->setFillColor(color);
    }
}

void MainWindow::on_showGridCheckbox_toggled(bool checked)
{
    view->setDrawGridLines(checked);
}

void MainWindow::on_centreSceneButton_clicked()
{
    view->centerOn(QPoint(0,0));
}

Thank you for helping me out !

[mrjj]

Hi
QStackWidget will hide/show the other pages so not sure even if transparent, it will work
as we would like.

But lets talk about MainWindow functions

void MainWindow::on_penWidthSpinBox_valueChanged(int arg1)
{
    scene->setPenWidth(arg1);

}
here we use the scene we have in main window but we want to affect the currents pages
scene or view 
so i would add to DrawingBoard, some access function to allow gettings its scene and view.
like getScene() and getView() that just returns its variables.

Then i would hook up
https://doc.qt.io/qt-5/qstackedwidget.html#currentChanged
to a slot
and use getScene() and getView() from DrawingBoard to get the current view/scene
You could use 2 member variables in MainWindow
curSecne and curView
and from start set to the ones MainWidnow has
but when you then switch page, we set to others.

void MainWindow::on_penWidthSpinBox_valueChanged(int arg1)
{
    curScene->setPenWidth(arg1);

}

so we use 2 variables to point to the scene or view that is active.

I hope this makes sense :)

[newToQt26]

@mrjj Hey ! Sorry for the late reply ! It was a long weekend !

This surely makes much more sense . I'll try this one out and let you know ! Thank you so much for helping me out

About stackedWidget , I'll look into it as well .. I think there might be some problems with transparency , because I did try it earlier and I didn't get desired results .

And I'll mark this solved as soon as I get this right ( in case I have any doubts while implementing it!)
Thanks again :)

[newToQt26]

@mrjj Hey ! I tried it. It worked like charm. along with it , I used QMap too.
Thank you so much for helping :)

[mrjj]

@newToQt26
Hi
Good to hear. :)

If the user can add or delete layers, it's pretty important you make sure
curScene/curView always points to something valid as else you get a nasty crash.