QStackedLayout / QStackedWidget

[jacek]

Is the QStackedWidget class the only way that you can have an application with different pages?

No, there's also QTabWidget and QMdiArea, which provide somewhat similar functionality.

when they say that only one stack is visible at a time does that mean that all stacks are loaded into memory

Yes, you have to create all pages before you can add them to the QStackedWidget.

will it load the code and generate that stack when its requested to be shown and then delete the previous stack and settings for that stack from memory?

No, it will just show different page and hide the current one, but you can implement such mechanism easily on your own. You would need some kind of a factory and a manager which will decide what pages to produce and add to the stack and which ones should be deleted.

does using QStacked Widget impact on performance of the application?

Yes, just like with every widget. The more pages you add to the stack, the more memory you will use.

Can you have multiple Qstacked Widgets as children within a parent QStacked Widget and more children with in them as well? (SAY 3 levels Deep)

The docs don't prohibit adding stacked widgets to stacked widget, so most likely you can have as many levels deep as your system can sustain.

I'm going to build a huge ERP type application which has many different forms and pages for the application and I'm just would like to know if the QStackedLayout - QStackedWidget programing paradigm is the way to go to achieve this produce this application with the best method available in QT.

For a very big system using sole QStackedWidget isn't a good solution, because you will use a lot of memory and your application will start slowly, because you will have to create whole GUI when it starts.

Although you can add pages on the fly, using some additional code just as I wrote earlier. Also take a look at QTabWidget, QTabBar, QMdiArea and QDockWidget.