Wt

This class can be set manually again, but creates a Design mismatch that has to be looked for and found.

Creating Panel Header manually:

auto panel = std::make_unique<Wt::WPanel>();
panel->setTitleBar(true);
auto txt_Title = panel->titleBarWidget()->addNew<Wt::WText>();
auto btn_TitleButton = panel->titleBarWidget()->addNew<Wt::WPushButton>("Click me!");

// needs style class setting
panel->titleBarWidget()->setStyleClass("panel-heading");

Without setting the style class, the panel is just as high as the Text.
It seems there is no margin top and bottom anymore.

Did only check in Bootstrap3Theme