| CFl | The Fl is the FLTK global (static) class containing state information and global methods for the current application | 
| CFl_Adjuster | Was stolen from Prisms, and has proven to be very useful for values that need a large dynamic range | 
| CFl_Bitmap | Supports caching and drawing of mono-color (bitmap) images | 
| CFl_BMP_Image | Supports loading, caching, and drawing of Windows Bitmap (BMP) image files | 
| CFl_Box | This widget simply draws its box, and possibly its label | 
| CFl_Browser | Displays a scrolling list of text lines, and manages all the storage for the text | 
| CFl_Browser_ | This is the base class for browsers | 
| CFl_Button | Buttons generate callbacks when they are clicked by the user | 
| CFl_Cairo_State | Contains all the necessary info on the current cairo context | 
| CFl_Cairo_Window | This defines a pre-configured cairo fltk window | 
| CFl_Chart | Fl_Chart displays simple charts | 
| CFL_CHART_ENTRY | For internal use only | 
| CFl_Check_Browser | Displays a scrolling list of text lines that may be selected and/or checked by the user | 
| CFl_Check_Button | A button with a "checkmark" to show its status | 
| CFl_Choice | A button that is used to pop up a menu | 
| CFl_Clock | This widget provides a round analog clock display | 
| CFl_Clock_Output | This widget can be used to display a program-supplied time | 
| CFl_Color_Chooser | Standard RGB color chooser | 
| CFl_Copy_Surface | Supports copying of graphical data to the clipboard | 
| CFl_Counter | Controls a single floating point value with button (or keyboard) arrows | 
| CFl_Device | All graphical output devices and all graphics systems | 
| CFl_Device_Plugin | This plugin socket allows the integration of new device drivers for special window or screen types | 
| CFl_Dial | Circular dial to control a single floating point value | 
| CFl_Display_Device | A display to which the computer can draw | 
| CFl_Double_Window | The Fl_Double_Window provides a double-buffered window | 
| CFl_End | This is a dummy class that allows you to end a Fl_Group in a constructor list of a class: | 
| CFl_File_Browser | Displays a list of filenames, optionally with file-specific icons | 
| CFl_File_Chooser | Displays a standard file selection dialog that supports various selection modes | 
| CFl_File_Icon | Manages icon images that can be used as labels in other widgets and as icons in the FileBrowser widget | 
| CFl_File_Input | This widget displays a pathname in a text input field | 
| CFl_Fill_Dial | Draws a dial with a filled arc | 
| CFl_Fill_Slider | Widget that draws a filled horizontal slider, useful as a progress or value meter | 
| CFl_Float_Input | Subclass of Fl_Input that only allows the user to type floating point numbers (sign, digits, decimal point, more digits, 'E' or 'e', sign, digits) | 
| CFl_FLTK_File_Chooser |  | 
| CFl_Font_Descriptor | This a structure for an actual system font, with junk to help choose it and info on character sizes | 
| CFl_Fontdesc |  | 
| CFl_FormsBitmap | Forms compatibility Bitmap Image Widget | 
| CFl_FormsPixmap | Forms pixmap drawing routines | 
| CFl_FormsText |  | 
| CFl_Free | Emulation of the Forms "free" widget | 
| CFl_GDI_Graphics_Driver | The MSWindows-specific graphics class | 
| CFl_GDI_Printer_Graphics_Driver | The graphics driver used when printing on MSWindows | 
| CFl_GIF_Image | Supports loading, caching, and drawing of Compuserve GIFSM images | 
| CFl_Gl_Choice |  | 
| CFl_Gl_Window | Sets things up so OpenGL works | 
| CFl_Glut_Bitmap_Font | Fltk glut font/size attributes used in the glutXXX functions | 
| CFl_Glut_StrokeChar |  | 
| CFl_Glut_StrokeFont |  | 
| CFl_Glut_StrokeStrip |  | 
| CFl_Glut_StrokeVertex |  | 
| CFl_Glut_Window | GLUT is emulated using this window class and these static variables (plus several more static variables hidden in glut_compatability.cxx): | 
| ►CFl_Graphics_Driver | A virtual class subclassed for each graphics driver FLTK uses | 
| Cmatrix | A 2D coordinate transformation matrix | 
| CFl_Group | FLTK container widget | 
| CFl_GTK_File_Chooser |  | 
| CFl_Help_Block |  | 
| CFl_Help_Dialog | Displays a standard help dialog window using the Fl_Help_View widget | 
| CFl_Help_Font_Stack |  | 
| CFl_Help_Font_Style | Fl_Help_View font stack element definition | 
| CFl_Help_Link | Definition of a link for the html viewer | 
| CFl_Help_Target | Fl_Help_Target structure | 
| CFl_Help_View | Displays HTML text | 
| CFl_Hold_Browser | The Fl_Hold_Browser is a subclass of Fl_Browser which lets the user select a single item, or no items by clicking on the empty space | 
| CFl_Hor_Fill_Slider |  | 
| CFl_Hor_Nice_Slider |  | 
| CFl_Hor_Slider | Horizontal Slider class | 
| CFl_Hor_Value_Slider |  | 
| CFl_Image | Base class for image caching and drawing | 
| CFl_Image_Surface | Directs all graphics requests to an Fl_Image | 
| CFl_Input | This is the FLTK text input widget | 
| CFl_Input_ | This class provides a low-overhead text input field | 
| CFl_Input_Choice | A combination of the input widget and a menu button | 
| CFl_Int_Input | Subclass of Fl_Input that only allows the user to type decimal digits (or hex numbers of the form 0xaef) | 
| CFl_JPEG_Image | Supports loading, caching, and drawing of Joint Photographic Experts Group (JPEG) File Interchange Format (JFIF) images | 
| CFl_Label | This struct stores all information for a text or mixed graphics label | 
| CFl_Light_Button | This subclass displays the "on" state by turning on a light, rather than drawing pushed in | 
| CFl_Line_Dial |  | 
| CFl_Mac_App_Menu | Mac OS-specific class allowing to customize and localize the application menu | 
| CFl_Menu_ | Base class of all widgets that have a menu in FLTK | 
| CFl_Menu_Bar | This widget provides a standard menubar interface | 
| CFl_Menu_Button | This is a button that when pushed pops up a menu (or hierarchy of menus) defined by an array of Fl_Menu_Item objects | 
| CFl_Menu_Item | The Fl_Menu_Item structure defines a single menu item that is used by the Fl_Menu_ class | 
| CFl_Menu_Window | Window type used for menus | 
| CFl_Multi_Browser | Subclass of Fl_Browser which lets the user select any set of the lines | 
| CFl_Multi_Label | This struct allows multiple labels to be added to objects that might normally have only one label | 
| CFl_Multiline_Input | This input field displays '\n' characters as new lines rather than ^J, and accepts the Return, Tab, and up and down arrow keys | 
| CFl_Multiline_Output | This widget is a subclass of Fl_Output that displays multiple lines of text | 
| CFl_Native_File_Chooser | This class lets an FLTK application easily and consistently access the operating system's native file chooser | 
| CFl_Nice_Slider |  | 
| CFl_Output | This widget displays a piece of text | 
| CFl_Overlay_Window | This window provides double buffering and also the ability to draw the "overlay" which is another picture placed on top of the main image | 
| CFl_Pack | This widget was designed to add the functionality of compressing and aligning widgets | 
| ►CFl_Paged_Device | Represents page-structured drawing surfaces | 
| Cpage_format | Width, height and name of a page format | 
| CFl_Pixmap | Supports caching and drawing of colormap (pixmap) images, including transparency | 
| CFl_Plugin | Fl_Plugin allows link-time and run-time integration of binary modules | 
| CFl_Plugin_Manager | Fl_Plugin_Manager manages link-time and run-time plugin binaries | 
| CFl_PNG_Image | Supports loading, caching, and drawing of Portable Network Graphics (PNG) image files | 
| CFl_PNM_Image | Supports loading, caching, and drawing of Portable Anymap (PNM, PBM, PGM, PPM) image files | 
| CFl_Positioner | This class is provided for Forms compatibility | 
| CFl_PostScript_File_Device | To send graphical output to a PostScript file | 
| CFl_PostScript_Graphics_Driver | PostScript graphical backend | 
| CFl_PostScript_Printer | Print support under Unix/Linux | 
| ►CFl_Preferences | Fl_Preferences provides methods to store user settings between application starts | 
| CEntry |  | 
| CName | 'Name' provides a simple method to create numerical or more complex procedural names for entries and groups on the fly | 
| CNode |  | 
| CRootNode |  | 
| CFl_Printer | OS-independent print support | 
| CFl_Progress | Displays a progress bar for the user | 
| CFl_Quartz_Graphics_Driver | The Mac OS X-specific graphics class | 
| CFl_Radio_Button |  | 
| CFl_Radio_Light_Button |  | 
| CFl_Radio_Round_Button |  | 
| CFl_Repeat_Button | The Fl_Repeat_Button is a subclass of Fl_Button that generates a callback when it is pressed and then repeatedly generates callbacks as long as it is held down | 
| CFl_Return_Button | The Fl_Return_Button is a subclass of Fl_Button that generates a callback when it is pressed or when the user presses the Enter key | 
| CFl_RGB_Image | Supports caching and drawing of full-color images with 1 to 4 channels of color information | 
| CFl_Roller | "dolly" control commonly used to move 3D objects | 
| CFl_Round_Button | Buttons generate callbacks when they are clicked by the user | 
| CFl_Round_Clock | A clock widget of type FL_ROUND_CLOCK | 
| ►CFl_Scroll | This container widget lets you maneuver around a set of widgets much larger than your window | 
| CFl_Region_LRTB | A local struct to manage a region defined by left/right/top/bottom | 
| CFl_Region_XYWH | A local struct to manage a region defined by xywh | 
| CFl_Scrollbar_Data | A local struct to manage a scrollbar's xywh region and tab values | 
| CScrollInfo | Structure to manage scrollbar and widget interior sizes | 
| CFl_Scrollbar | Displays a slider with arrow buttons at the ends of the scrollbar | 
| CFl_Secret_Input | Subclass of Fl_Input that displays its input as a string of placeholders | 
| CFl_Select_Browser | The class is a subclass of Fl_Browser which lets the user select a single item, or no items by clicking on the empty space | 
| CFl_Shared_Image | This class supports caching, loading, scaling, and drawing of image files | 
| CFl_Simple_Counter | This widget creates a counter with only 2 arrow buttons | 
| CFl_Single_Window | This is the same as Fl_Window | 
| CFl_Slider | Sliding knob inside a box | 
| CFl_Spinner | This widget is a combination of the input widget and repeat buttons | 
| CFl_Surface_Device | A drawing surface that's susceptible to receive graphical output | 
| CFl_Sys_Menu_Bar | A class to create, modify and delete menus that appear on Mac OS X in the menu bar at the top of the screen | 
| CFl_System_Printer | Print support under MSWindows and Mac OS | 
| CFl_Table | A table of widgets or other content | 
| CFl_Table_Row | A table with row selection capabilities | 
| CFl_Tabs | "file card tabs" interface that allows you to put lots and lots of buttons and switches in a panel, as popularized by many toolkits | 
| CFl_Text_Buffer | This class manages Unicode text displayed in one or more Fl_Text_Display widgets | 
| ►CFl_Text_Display | Rich text display widget | 
| CStyle_Table_Entry | This structure associates the color, font, and font size of a string to draw with an attribute mask matching attr | 
| ►CFl_Text_Editor | This is the FLTK text editor widget | 
| CKey_Binding | Simple linked list item associating a key/state to a function | 
| CFl_Text_Selection | This is an internal class for Fl_Text_Buffer to manage text selections | 
| CFl_Tile | Lets you resize its children by dragging the border between them | 
| CFl_Tiled_Image | This class supports tiling of images over a specified area | 
| CFl_Timer | This is provided only to emulate the Forms Timer widget | 
| CFl_Toggle_Button | The toggle button is a push button that needs to be clicked once to toggle on, and one more time to toggle off | 
| CFl_Tooltip | Tooltip support for all FLTK widgets | 
| CFl_Tree | Tree widget | 
| CFl_Tree_Item | Tree widget item | 
| CFl_Tree_Item_Array | Manages an array of Fl_Tree_Item pointers | 
| CFl_Tree_Prefs | Tree widget's preferences | 
| CFl_Valuator | Controls a single floating-point value and provides a consistent interface to set the value, range, and step, and insures that callbacks are done the same for every object | 
| CFl_Value_Input | Displays a numeric value | 
| CFl_Value_Output | Displays a floating point value | 
| CFl_Value_Slider | Fl_Slider widget with a box displaying the current value | 
| CFl_Widget | Fl_Widget is the base class for all widgets in FLTK | 
| CFl_Widget_Tracker | This class should be used to control safe widget deletion | 
| ►CFl_Window | This widget produces an actual window | 
| Cshape_data_type | Data supporting a non-rectangular window shape | 
| CFl_Wizard | This widget is based off the Fl_Tabs widget, but instead of displaying tabs it only changes "tabs" under program control | 
| CFl_XBM_Image | Supports loading, caching, and drawing of X Bitmap (XBM) bitmap files | 
| CFl_XColor |  | 
| CFl_Xlib_Graphics_Driver | The Xlib-specific graphics class | 
| CFl_XPM_Image | Supports loading, caching, and drawing of X Pixmap (XPM) images, including transparency |