Still need help: Best way to have application "skins"?

[jpn]

Any chance I could create some for(int i=0; i<childWidgets().length(); i++) loop? Note that childWidgets() may not be an actual property, but for the sake of this question...

Do you mean something like:

QPushButton* button = findChild<QPushButton*>("myButtonWithCertainObjectName");
if (button) // just to assure it was found
   button->doSomething();
 
// or
 
QList<QPushButton*> allButtons = findChildren<QPushButton*>();
foreach (QPushButton* button, allButtons)
   button->doSomething();

QPushButton* button = findChild<QPushButton*>("myButtonWithCertainObjectName");
if (button) // just to assure it was found
   button->doSomething();

// or

QList<QPushButton*> allButtons = findChildren<QPushButton*>();
foreach (QPushButton* button, allButtons)
   button->doSomething();

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Also, where would I put the connect()'s? In each of the plainUi and fancyUi functions, or in the constructor?

The whole GUI, including all widgets, gets re-created when you call respective setupUi(). So you must re-establish all signal-slot connections every time the "mode" is changed.