Return the ratio between pixel and device coordinates (e.g. >= 2 on Mac Retina displays)

Create a ``nullptr``-valued reference

Cause all widgets to re-synchronize with the underlying variable state

Window resize event handler

Return a pointer to the underlying nanoVG draw context

The current index this dropdownbox has selected.

Set the anchor height; this determines the vertical shift relative to the anchor position

Set the screen's background color

Set the button group (for radio buttons)

Sets the callback to execute for this widget.

* Sets the callable objects which is invoked when a tab button is pressed. * The argument provided to the callback is the index of the tab.

* Sets the callable objects which is invoked when a tab is changed. * The argument provided to the callback is the index of the new active tab.