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

[detail level 123]

►NGdk
CAppLaunchContext	This is an implementation of Gio::AppLaunchContext that handles launching an application in a graphical context
CColor	Gdk::Color is used to describe an allocated or unallocated color
CCursor	This represents a cursor
CDevice	A Gdk::Device instance contains a detailed description of an extended input device
CDeviceManager	Functions for handling input devices
CDisplay	Gdk::Display object's purpose is two fold: To grab/ungrab keyboard focus and mouse pointer To manage and provide information about the Gdk::Screen(s) available for this Gdk::Display
CDisplayManager	The purpose of the GdkDisplayManager singleton object is to offer notification when displays appear or disappear or the default display changes
CDragContext	A Gdk::DragContext holds information about a drag in progress
CDrawingContext	Drawing context for GDK windows
CEvent
CGLContext	A Gdk::GLContext is an OpenGL context abstraction
CGLError
CMonitor	Object representing an output
CPixbuf
CPixbufAnimation	The gdk-pixbuf library provides a simple mechanism to load and represent animations
CPixbufAnimationIter	An iterator which points to a certain position in a PixbufAnimation
CPixbufError	Exception class for Gdk::Pixbuf errors
CPixbufFormat
CPixbufLoader
CPoint	This is a simple structure containing an x and y coordinate of a point
CRectangle	Gdk::Rectangle is a structure holding the position and size of a rectangle
CRGBA	An RGBA Color
CScreen	Object representing a physical screen Gdk::Screen objects are the GDK representation of a physical screen
CSeat	A Gdk::Seat object represents a collection of input devices that belong to a user
CTimeCoord	A Gdk::TimeCoord instance contains a single event of motion history
CVisual	A Gdk::Visual describes a particular video hardware display format
CWindow	A Gdk::Window is a rectangular region on the screen
►NGlib
CValue< Glib::RefPtr< Gtk::RecentInfo > >
CValue< Glib::RefPtr< Gtk::TargetList > >
►NGtk	Copyright (C) 2012 The gtkmm Development Team
CAboutDialog	The AboutDialog offers a simple way to display information about a program like its logo, name, copyright, website and license
CAccelGroup	A Gtk::AccelGroup represents a group of keyboard accelerators, typically attached to a toplevel Gtk::Window (with Gtk::Window::add_accel_group())
CAccelKey	Defines accelerator key combinations
CAccelLabel	A label which displays an accelerator key on the right of the text
CAction	A deprecated action which can be triggered by a menu or toolbar item
CActionable	This interface provides a convenient way of associating widgets with actions on a ApplicationWindow or Application
CActionBar	A full width bar for presenting contextual actions
CActionGroup	A deprecated action group
CActivatable	Activatable widgets can be connected to a Gtk::Action and reflect the state of the action
CAdjustment	A class representing an adjustable bounded value
CAlignment	A widget which controls the alignment and size of its child
CAppChooser	Interface implemented by widgets for choosing an application
CAppChooserButton	A button to launch an application chooser dialog
CAppChooserDialog	An application chooser dialog
CAppChooserWidget	An application chooser widget that can be embedded in other widgets
CApplication	The Gtk::Application class handles many important aspects of a GTK+ application in a convenient fashion, without enforcing a one-size-fits-all application model
CApplicationWindow	A Gtk::Window subclass with Gtk::Application support
CArrow	Produces an arrow pointing in one of the four cardinal directions
CAspectFrame	A frame that constrains its child to a particular aspect ratio
CAssistant	A widget used to guide users through multi-step operations
CBin	A container with just one child
CBorder	This specifies a border around a rectangular area that can be of a different width on each side
CBox	Organizes child widgets into a rectangular area
CBuildable	A base class for objects that can be built by Gtk::Builder
CBuilder	Build an interface from an XML UI definition description
CBuilderError	Exception class for Gdk::Builder errors
CBuiltinStockID	See the list of pre-defined stock items, in the Stock namespace
CButton	A widget that creates a signal when clicked on
CButtonBox	A container for arranging buttons
CCalendar	Display a calendar and/or allow the user to select a date
CCellArea	An abstract base class for laying out CellRenderers
CCellAreaBox	A cell area that renders CellRenderers into a row or a colum, depending on its orientation
CCellAreaContext	This stores geometrical information for a series of rows in a CellArea
CCellEditable	Interface for widgets which are used for editing cells
CCellLayout	An interface for packing cells
CCellRenderer	CellRenderers are used by Gtk::TreeView columns to render the Gtk::TreeModel column data appropriately
CCellRendererAccel	Renders a keyboard accelerator in a cell
CCellRendererCombo	Renders a combobox in a cell
CCellRendererPixbuf	Renders a pixbuf in a cell
CCellRendererProgress	Renders numbers as progress bars
CCellRendererSpin	Renders a spin button in a cell
CCellRendererSpinner	Renders a spinning animation in a cell
CCellRendererText	Renders text in a cell
CCellRendererToggle	Renders a toggle button in a cell
CCellView	A widget displaying a single row of a TreeModel
CCheckButton	Create widgets with a discrete toggle button
CCheckMenuItem	A menu item that maintains the state of a boolean value in addition to a Gtk::MenuItem's usual role in activating application code
CChildPropertyProxy	A ChildPropertyProxy can be used to get and set the value of a GtkContainer's child property
CChildPropertyProxy_Base
CChildPropertyProxy_ReadOnly	See ChildPropertyProxy()
CChildPropertyProxy_WriteOnly	See ChildPropertyProxy()
CClipboard	The Clipboard object represents a clipboard of data shared between different processes or between different widgets in the same process
CColorButton	A button to launch a color selection dialog
CColorChooser	This interface can be implemented by widgets which allow the user to choose a color
CColorChooserDialog	This dialog is for choosing a color
CColorSelection	A widget used to select a color
CColorSelectionDialog	This dialog allows the user to select a color
CComboBox	A widget used to choose from a list of items
CComboBoxText	This is a simple variant of ComboBox that hides the model-view complexity for simple text-only use cases
CContainer	Abstract container class
CCssProvider	CSS-like styling for widgets, implementing the StyleProvider base class
CCssProviderError	Exception class for Gtk::CssProvider errors
CCssSection	Defines a part of a CSS document
CDialog	Create popup windows
CDrawingArea	A widget for custom user interface elements
CEditable	Base class for text-editing widgets
CEntry	A single line text entry field
CEntryBuffer	A Text buffer for the Entry widget
CEntryCompletion	Completion functionality for Gtk::Entry
CEventBox	Event capturing box
CEventController	Self-contained handler of series of events
CExpander	A container which can hide its child
CFileChooser	Gtk::FileChooser is an interface that can be implemented by file selection widgets
CFileChooserButton	A button to launch a file chooser dialog
CFileChooserDialog	Convenient file chooser window
CFileChooserError	Exception class for Gdk::FileChooser errors
CFileChooserWidget	File chooser widget that can be embedded in other widgets
►CFileFilter	A filter for selecting a file subset
CInfo
CFixed	A container which allows you to position widgets at fixed coordinates
CFlowBox	A container that allows reflowing its children
CFlowBoxChild	See the description of FlowBox
CFontButton	A button to launch a font selection dialog
CFontChooser	An interface implemented by widgets displaying fonts
CFontChooserDialog	A dialog box for selecting fonts
CFontChooserWidget	A dialog box for selecting fonts
CFontSelection	A widget for selecting fonts
CFontSelectionDialog	A dialog box for selecting fonts
CFrame	A Gtk::Bin with a decorative frame and optional label
CGesture	Abstract base class for gestures
CGestureDrag	Drag gesture
CGestureLongPress	"Press and Hold" gesture
CGestureMultiPress	Multipress gesture
CGesturePan	Pan gesture
CGestureRotate	Rotate gesture
CGestureSingle	Abstract base class for mouse/single-touch gestures
CGestureSwipe	Swipe gesture
CGestureZoom	Zoom gesture
CGLArea	A widget used for drawing with OpenGL
CGrid	A container which arranges its child widgets in rows and columns
CHandleBox	A widget for detachable window portions
CHBox	Horizontal Box for laying widgets in a horizontal row
CHButtonBox	A container for arranging buttons horizontally
CHeaderBar	A box with a centered child
CHPaned	The Gtk::HPaned widget is a container widget with two children arranged horizontally
CHScale	A horizontal slider for selecting values
CHScrollbar	A horizontal scrollbar
CHSeparator	Horizontal line widget
CIconFactory
CIconInfo
CIconSet	This manages a set of variants of a particular icon An IconSet contains variants for different sizes and widget states
CIconSize	Represents registered icon sizes
CIconSource
CIconTheme
CIconThemeError	Exception class for Gtk::IconTheme errors
CIconView	The IconView provides an alternative view of a list model
CImage	A widget displaying an image
CImageMenuItem	A menu item with an icon
CInfoBar	This widget that can be used to show messages to the user without showing a dialog
CInvisible	This widget is used internally in GTK+, and is probably not useful for application developers
CLabel	A widget that displays a small to medium amount of text
CLayout	Infinite scrollable area containing child widgets and/or custom drawing
CLevelBar	A bar that can used as a level indicator
CLinkButton	Create buttons bound to a URL
CListBox	A ListBox is a vertical container that contains ListBoxRow children
CListBoxRow	See the description of ListBox
CListStore	Thist is a list model for use with a Gtk::TreeView widget
►CListViewText	A simple listbox which presents some lines of information in columns and lets the user select some of them
CTextModelColumns
CLockButton	A widget to unlock or lock privileged operations
CMain	Main application class
CMenu	A drop-down menu consisting of Gtk::MenuItem objects which can be navigated and activated by the user to perform application functions
CMenuBar	A standard menu bar which usually holds Gtk::Menu submenu items
CMenuButton	A widget that shows a menu when clicked on
CMenuItem	Child item for menus
CMenuShell	The abstract base class for Gtk::Menu and Gtk::MenuBar
CMenuToolButton	A Gtk::ToolItem containing a toggle button
CMessageDialog	Convenient message window
CMisc	A base class for widgets with alignments and padding
CModelButton	A button that uses a Gio::Action as model
CNotebook	Container which shows one of its children at a time, in tabbed windows
CNumerableIcon	A Gio::Icon that allows numbered emblems
CObject	Gtk::Object is the base class for all widgets, and for a few non-widget objects such as Gtk::Adjustment
COffscreenWindow	A top-level container widget used to manage offscreen rendering of child widgets
COrientable	This interface is implemented by all widgets that can be oriented horizontally or vertically
COverlay	A container which overlays widgets on top of each other
CPageSetup	A PageSetup object stores the page size, orientation and margins
CPageSetupUnixDialog	PageSetupUnixDialog implements a page setup dialog for platforms which don't provide a native page setup dialog, like Unix
CPaned	A widget with two adjustable panes
CPaperSize	PaperSize handles paper sizes
CPlacesSidebar	Sidebar that displays frequently-used places in the file system
CPlug	Toplevel for embedding into other processes
CPopover	Context dependent bubbles
CPopoverMenu	A Popover to use as a menu
CPrintContext	A PrintContext encapsulates context information that is required when drawing pages for printing, such as the cairo context and important parameters like page size and resolution
CPrinter	A Printer object represents a printer
CPrintError
CPrintJob	A PrintJob object represents a job that is sent to a printer
CPrintOperation	PrintOperation is the high-level, portable printing API
CPrintOperationPreview
►CPrintSettings	A PrintSettings object represents the settings of a print dialog in a system-independent way
CKeys	Print settings keys
CPageRange
CPrintUnixDialog	PrintUnixDialog implements a print dialog for platforms which don't provide a native print dialog, like Unix
CProgressBar	A widget which indicates progress visually
CRadioAction	A deprecated action of which only one in a group can be active
CRadioButton	A choice from multiple check buttons
CRadioButtonGroup	RadioButtonGroup, identifier for RadioButtons
CRadioMenuItem	A CheckMenuItem that belongs to a group
CRadioToolButton	A toolbar item that contains a radio button
CRange	Base class for widgets which visualize an adjustment
CRecentAction	A deprecated action of which represents a list of recently used files
CRecentChooser	RecentChooser is an interface that can be implemented by widgets displaying the list of recently used files
CRecentChooserDialog	RecentChooserDialog is a dialog box suitable for displaying the recently used documents
CRecentChooserError	Exception class for Gtk::RecentChooser errors
CRecentChooserMenu	RecentChooserMenu is a widget suitable for displaying recently used files inside a menu
CRecentChooserWidget	RecentChooserWidget is a widget suitable for selecting recently used files
►CRecentFilter	RecentFilter can be used to restrict the files being shown in a RecentChooser
CInfo	A RecentFilter::Info class is used to pass information about the tested file to filter()
CRecentInfo	Contains information found when looking up an entry of the recently used files list
►CRecentManager	RecentManager provides a facility for adding, removing and looking up recently used files
CData	Meta-data passed to add_item()
CRecentManagerError	Exception class for Gtk::RecentManager errors
CRevealer	Hide and show with animation
CScale	A slider widget for selecting a value from a range
CScaleButton	A button which pops up a scale widget
CScrollable	This interface is implemented by widgets with native scrolling ability
CScrollbar	A Scrollbar
CScrolledWindow	Adds scrollbars to its child widget
CSearchBar	A toolbar to integrate a search entry with
CSearchEntry	This is a subclass of Gtk::Entry that has been tailored for use as a search entry
CSelectionData
CSeparator	A separator widget
CSeparatorMenuItem	A separator used to group items within a menu
CSeparatorToolItem	A toolbar item that separates groups of other toolbar items
CSettings	Sharing settings between applications
CShortcutLabel	Displays a keyboard shortcut
CShortcutsGroup	Represents a group of shortcuts in a ShortcutsWindow
CShortcutsSection	Represents an application mode in a ShortcutsWindow
CShortcutsShortcut	Represents a keyboard shortcut in a ShortcutsWindow
CShortcutsWindow	Toplevel which shows help for shortcuts
CSignalProxyChildProperty
CSizeGroup	Gtk::SizeGroup provides a mechanism for grouping a number of widgets together so they all request the same amount of space
CSocket	Container for widgets from other processes
CSpinButton	Numeric Entry with up/down buttons Slightly misnamed, this should be called a SpinEntry
CSpinner	A widget that displays a spinner animation
CStack	A container that shows only one child at a time
CStackSidebar	Sidebar widget that shows the pages of a Stack
CStackSwitcher	A controller for a Gtk::Stack
CStatusbar	Text status indicator This widget is used to display status information
CStatusIcon	The "system tray" or notification area is normally used for transient icons that indicate some special state
CStockID	See also Gtk::BuiltinStockID
CStockItem
CStyleContext	This object stores styling information affecting a widget defined by WidgetPath
CStyleProperty	Represents a widget style property
CStylePropertyBase	Base class for widget style properties
CStyleProvider	This is a base class used to provide style information to a StyleContext
CSwitch	A "light switch"-style toggle
CTable	Pack widgets in regular patterns
CTargetEntry
CTargetList
CTearoffMenuItem	A special Gtk::MenuItem which is used to tear off and reattach its menu
CTextAttributes
CTextBuffer	Multi-line attributed text that can be displayed by one or more Gtk::TextView widgets
CTextChildAnchor	A TextChildAnchor is a spot in the buffer where child widgets can be "anchored" (inserted inline, as if they were characters)
CTextIter	Typefed as Gtk::TextBuffer::iterator
CTextMark	Typedefed as Gtk::TextBuffer::Mark
CTextTag	Typedefed as Gtk::TextBuffer::Tag
CTextTagTable	Typedefed as Gtk::TextBuffer::TagTable
CTextView	Multi-line text editing widget
CToggleAction	A deprecated action which can be toggled between two states
CToggleButton	A Gtk::ToggleButton will remain 'pressed-in' when clicked
CToggleToolButton	A Gtk::ToolItem containing a toggle button
CToolbar	Bars of buttons and other widgets
CToolButton	A Gtk::ToolItem subclass that displays buttons
CToolItem	The base class of widgets that can be added to ToolShell
CToolItemGroup	A ToolItemGroup is used together with ToolPalette to add ToolItems to a palette-like container with different categories and drag and drop support
CToolPalette	A ToolPalette allows you to add ToolItems to a palette-like container with various categories and drag and drop support
CToolShell	A base class for containers containing ToolItem widgets
CTooltip	Add tips to your widgets
CTreeDragDest
CTreeDragSource
CTreeIter	A Gtk::TreeModel::iterator is a reference to a specific node on a specific model
CTreeIterBase
CTreeModel	This class defines a generic tree interface for use by the Gtk::TreeView widget
CTreeModelColumn	A Gtk::TreeModelColumn describes the C++ type of the data in a model column, and identifies that column in the model
CTreeModelColumnBase	Base class of TreeModelColumn templates
CTreeModelColumnRecord	Typedefed as TreeModel::ColumnRecord
CTreeModelFilter
CTreeModelSort	A wrapper which makes an underlying Gtk::TreeModel sortable
CTreeNodeChildren	Typedefed as TreeModel::Children
CTreePath	A path is essentially a potential node
CTreeRow	Typedefed as TreeModel::Row
CTreeRowReference	Typedefed as Gtk::TreeModel::RowReference
CTreeSelection	Typedefed as Gtk::TreeView::Selection
CTreeSortable
CTreeStore
CTreeValueProxy
CTreeView	Displays the model (Gtk::TreeModel) data and allows the user to interact with it
CTreeViewColumn	Typedefed as Gtk::TreeView::Column
CUIManager	Constructing menus and toolbars from an XML description
CVBox	Vertical Box for laying widgets in a vertical row
CVButtonBox	A container for arranging buttons vertically
CViewport	An adapter which makes widgets scrollable
CVolumeButton	A button which pops up a volume control
CVPaned	The Gtk::VPaned widget is a container widget with two children arranged vertically
CVScale	A vertical slider for selecting values
CVScrollbar	A vertical scrollbar
CVSeparator	Vertical line widget
CWidget	Abstract Widget (Base class for all widgets)
CWidgetPath	This represents a widget hierarchy from the topmost widget, typically a toplevel, to any child
CWindow	Toplevel Window
CWindowGroup	Limit the effect of grabs