Here are the classes, structs, unions and interfaces with brief descriptions:

[detail level 123]

Nfcn
Nopengl
CGraphics	OpenGL-specific implementation of the Graphics interface
CImage	OpenGL-specific implementation of Image
CImageLoader	OpenGL ImageLoader that loads images with SDL
Nsdl2	Unified header for the SDL backend
CGraphics	SDL2 renderer-specific implementation of the Graphics interface
CImage	SDL2-specific implementation of Image
CImageLoader	SDL2-specific implementation of ImageLoader
CInput	SDL2-specific implementation of Input
CTrueTypeFont	SDL2/FreeType implementation for rendering TrueType fonts
CActionEvent	Represents an action trigger (e.g., button click)
CActionListener	Interface for listening to action events from widgets
CAdjustingContainer	Self-adjusting Container class
CBarGraph	Displays data as a rectangular bar graph
CButton	A standard clickable button widget
CCheckBox	An implementation of a check box where a user can select or deselect the check box and where the status of the check box is displayed to the user
CClipRectangle	A rectangle specifically used for clipping rendering regions
CColor	Color
CContainer	A composite widget capable of holding and managing child widgets
CContainerEvent	Represents changes within a container (e.g., widget added/removed)
CContainerListener	Interface for listening to container modification events
CCurveGraph	Displays data as a smooth curve based on a vector of points
CDeathListener	Interface for listening to widget destruction events
CDefaultFont	A basic font implementation capable only of drawing rectangles (placeholder)
CDropDown	A dropdown list widget allowing single item selection from a list
CEvent	Base class for all GUI event objects
CException	An exception class containing a message, a file, and a line number where the exception occurred
Cfloat_traits	Generic template for floating-point type traits
Cfloat_traits< double >	Specialization of float traits for double
Cfloat_traits< float >	Specialization of float traits for float
CFlowContainer	An implementation of a flow container that can contain other widgets
CFocusHandler	Manages focus navigation and assignment among widgets within a Gui instance
CFocusListener	Interface for listening to focus gain/loss events
CFont	Abstract interface for font rendering
CGenericInput	A generic input implementation usable with various backends
CGraphics	Abstract interface providing primitive drawing functions (lines, rectangles, etc.)
CGui	The central GUI manager
CGuiDeathListener	Internal listener that forwards death notifications from widgets to the owning Gui so it can clean up references
CIcon	Displays a static image icon
CIconProgressBar	Displays progress using a sequence of icons
CImage	Abstract holder for image data
CImageButton	An implementation of a regular clickable button
CImageFont	A font implementation using an image atlas containing glyph data
CImageLoader	Abstract interface for loading image assets
CImageProgressBar	Displays progress using images
CInput	Abstract interface for polling user input devices
CInputEvent	Base class for all input-related events (keyboard, mouse)
CKey	Represents a keyboard key or character code
CKeyEvent	Represents a key event
CKeyInput	Internal class representing raw keyboard input data
CKeyListener	Interface for listening to keyboard events
CLabel	Displays a text caption
CLineGraph	Displays data as a line graph connecting a vector of points
CListBox	A scrollable list box allowing item selection
CListModel	Interface for a data model representing a list (used by ListBox/DropDown)
CMath	Template utility providing math functions and constants for numeric type T
CMouseEvent	Represents a mouse event
CMouseInput	Internal class representing raw mouse input data
CMouseListener	Interface for listening to mouse events
CPasswordField	Password input widget
CPieGraph	Displays data as a circular pie chart
CPieGraphSegment	Represents a single segment of a pie graph (angles and color)
CPoint	Represents a 2D coordinate (X, Y)
CPointGraph	Draws a scatter graph of individual points
CRadioButton	An implementation of a radio button where a user can select or deselect the radio button and where the status of the radio button is displayed to the user
CRectangle	Represents a rectangular area (X, Y, Width, Height)
CScrollArea	A scrollable viewport for viewing widgets larger than the visible area
CSelectionEvent	Represents a change in selection state (e.g., list item selected)
CSelectionListener	Interface for listening to selection change events
CSize	Represents dimensions defined by width and height
CSlider	A control for selecting a numeric value by sliding along a scale
CSpacer	Provides empty space to assist with layout management
CTab	A single tab label used within a TabbedArea
CTabbedArea	A container organizing content into selectable tabs
CText	Helper class for text manipulation within widgets
CTextBox	A multi-line text input field
CTextField	A single-line text input field
CToggleButton	An implementation of a toggleable button
CUTF8StringEditor	Utility for editing and handling UTF-8 encoded strings
CVisibilityEventHandler	Handles changes in widget visibility states
CWidget	Abstract base class defining the common behavior, properties, and lifecycle of all GUI elements
CWidgetListener	Interface for receiving generic events from widgets
CWindow	A movable container window that can hold other widgets
Nutf8
Nunchecked
Citerator
Cexception
Cinvalid_code_point
Cinvalid_utf16
Cinvalid_utf8
Citerator
Cnot_enough_room