Fl_Window

Window class for creating top-level windows and subwindows

Fl_Window produces an actual window that can be a main window with borders and title bar, or a subwindow inside another window. Once created, add child widgets using window->add(child).

The window’s callback is called when the user tries to close the window. The default callback calls hide().

Constructors

Fl_Window(int w, int h, const char *title = 0);
Fl_Window(int x, int y, int w, int h, const char *title = 0);

w, h · int · required

Width and height of the window in pixels

x, y · int

Position of the window (for positioned constructor)

title · const char*

Window title bar text (optional)

Description:

• The (w, h) form creates a top-level window and asks the window manager to position it.
• The (x, y, w, h) form creates a window at the specified location.

Example:

// Let window manager position it
Fl_Window *win1 = new Fl_Window(400, 300, "My Window");

// Position at (100, 100)
Fl_Window *win2 = new Fl_Window(100, 100, 400, 300, "Positioned");

Display Methods

show()

Displays the window on screen.

virtual void show();
void show(int argc, char **argv);

argc · int

Command-line argument count

argv · char**

Command-line argument vector

Description:

• show() displays the window. If already shown, it is restored and raised to top.
• show(argc, argv) is used for top-level windows and parses command-line arguments.

Example:

window->show();
return Fl::run();

hide()

Removes the window from the screen.

virtual void hide() override;

Description: If the window is already hidden or not shown, this does nothing.

shown()

Checks if window has been shown.

int shown() const;

Returns: Non-zero if show() has been called (but not hide())

Note: You can tell if a window is iconified with (w->shown() && !w->visible()).

iconize()

Iconifies the window.

void iconize();

Description: Minimizes the window. Call show() to restore it.

Size and Position

resize()

Changes window size and/or position.

void resize(int X, int Y, int W, int H) override;

X, Y · int · required

New position

W, H · int · required

New size

Description: For shown windows, changes are communicated to the window server. Window managers may refuse the size/position.

position()

Sets window position.

void position(int X, int Y);

X, Y · int · required

New window position

Description: Inherited from Fl_Widget, shortcut for resize(X, Y, w(), h()).

hotspot()

Positions window with mouse at specified point.

void hotspot(int x, int y, int offscreen = 0);
void hotspot(const Fl_Widget* widget, int offscreen = 0);

x, y · int · required

Position where mouse should point

widget · const Fl_Widget*

Widget to center mouse on

offscreen · int

Allow window to extend offscreen if non-zero

size_range()

Sets minimum and maximum window size.

void size_range(int minw, int minh, int maxw=0, int maxh=0, 
                int dw=0, int dh=0, int aspect=0);

minw, minh · int · required

Minimum width and height

maxw, maxh · int

Maximum width and height (0 = unlimited)

dw, dh · int

Width and height step increments

aspect · int

Flag to keep aspect ratio

Example:

window->size_range(300, 200, 800, 600);  // Min 300x200, max 800x600

Fullscreen

fullscreen()

Makes window fullscreen.

void fullscreen();

Description: Makes the window fill one or more screens without window manager borders.

fullscreen_off()

Returns from fullscreen mode.

void fullscreen_off();
void fullscreen_off(int X, int Y, int W, int H);

X, Y, W, H · int

Window dimensions to restore to (optional)

fullscreen_active()

Checks if fullscreen is active.

unsigned int fullscreen_active() const;

Returns: Non-zero if window is fullscreen

fullscreen_screens()

Sets which screens to use in fullscreen.

void fullscreen_screens(int top, int bottom, int left, int right);

top, bottom, left, right · int · required

Screen indices for each edge

Maximize

maximize()

Maximizes the window.

void maximize();

Description: Maximizes the window to fill available screen space.

un_maximize()

Restores window from maximized state.

void un_maximize();

maximize_active()

Checks if window is maximized.

unsigned int maximize_active() const;

Returns: Non-zero if window is maximized

Window Properties

label()

Gets or sets window title.

const char* label() const;
void label(const char* title);
void label(const char* label, const char* iconlabel);

title · const char* · required

Window title bar text

iconlabel · const char*

Text for iconified window

iconlabel()

Gets or sets icon label.

const char* iconlabel() const;
void iconlabel(const char* label);

label · const char* · required

Label for iconified window

xclass()

Gets or sets X11 class hint.

const char* xclass() const;
void xclass(const char* c);

c · const char* · required

X11 window class name

Window Icons

icon()

Sets the window icon.

void icon(const Fl_RGB_Image* img);

img · const Fl_RGB_Image* · required

Image to use as window icon

icons()

Sets multiple window icons.

void icons(const Fl_RGB_Image*[] images, int count);

images · const Fl_RGB_Image*[] · required

Array of icon images at different sizes

count · int · required

Number of images in array

Window Borders

border()

Gets or sets window border.

unsigned int border() const;
void border(int b);

b · int · required

1 to show border, 0 to hide

Description: Controls whether window manager border is shown. Must be called before show().

clear_border()

Turns off window border.

void clear_border();

Description: Fast inline function. Only works before show() is called.

set_override()

Activates override redirect.

void set_override();

Description: Sets NOBORDER and OVERRIDE flags for popup windows.

Modal Windows

modal()

Checks if window is modal.

unsigned int modal() const;

Returns: Non-zero if window is modal

set_modal()

Makes window modal.

void set_modal();

Description: Modal windows prevent events to other windows and remain on top.

non_modal()

Checks if window is non-modal.

unsigned int non_modal() const;

Returns: Non-zero if window is modal or non-modal

set_non_modal()

Makes window non-modal.

void set_non_modal();

Description: Non-modal windows stay on top but don’t block events to other windows.

clear_modal_states()

Clears modal and non-modal flags.

void clear_modal_states();

Description: Converts modal or non-modal window back to normal. Call hide() first, then change state, then show().

Special Window Types

set_menu_window()

Marks window as a menu window.

void set_menu_window();

Description: For internal use. Must be called before show().

menu_window()

Checks if window is a menu window.

unsigned int menu_window() const;

Returns: Non-zero if window is a menu window

set_tooltip_window()

Marks window as a tooltip window.

void set_tooltip_window();

Description: For internal use. Must be called before show().

tooltip_window()

Checks if window is a tooltip window.

unsigned int tooltip_window() const;

Returns: Non-zero if window is a tooltip window

Rendering

make_current()

Sets this window as the current drawing context.

void make_current();

Description: Sets up drawing functions to draw into this window. Useful for incremental updates.

current()

Gets the current window.

static Fl_Window *current();

Returns: Pointer to window that was last made current

flush()

Forces window to redraw.

virtual void flush();

Description: Forces the window to be drawn and makes it current.

Screen Information

screen_num()

Gets or sets which screen the window is on.

int screen_num() const;
void screen_num(int screen_num);

screen_num · int · required

Screen number to use

decorated_w(), decorated_h()

Gets window size including decorations.

int decorated_w() const;
int decorated_h() const;

Returns: Window width/height including title bar and borders

Description: Returns same as w() or h() if window is not yet mapped.

Position Helper

x_root(), y_root()

Gets absolute screen position.

int x_root() const;
int y_root() const;

Returns: X or Y coordinate relative to screen origin

Cursor

cursor()

Sets the cursor for this window.

void cursor(Fl_Cursor cursor);
void cursor(const Fl_RGB_Image* img, int hotx, int hoty);

cursor · Fl_Cursor · required

Standard cursor type (FL_CURSOR_ARROW, FL_CURSOR_WAIT, etc.)

img · const Fl_RGB_Image*

Custom cursor image

hotx, hoty · int

Hot spot coordinates for custom cursor

default_cursor()

Sets the default cursor.

void default_cursor(Fl_Cursor cursor);

cursor · Fl_Cursor · required

Default cursor to use

Window Callbacks

default_callback()

Default callback for windows.

static void default_callback(Fl_Window* window, void* v);

window · Fl_Window* · required

Window receiving callback

v · void*

User data

Description: Default callback calls hide() on the window.

Type Checking

as_window()

Returns this as an Fl_Window pointer.

Fl_Window* as_window() override;

Returns: Pointer to this window

Example

#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/Fl_Button.H>

void button_callback(Fl_Widget*, void*) {
  printf("Button clicked!\n");
}

int main() {
  Fl_Window *window = new Fl_Window(400, 300, "My Application");
  window->begin();
  
  Fl_Button *button = new Fl_Button(150, 125, 100, 50, "Click Me");
  button->callback(button_callback);
  
  window->end();
  window->show();
  
  return Fl::run();
}

Related

• Fl (Global Namespace) - Event loop and global functions
• Fl_Widget - Base widget class
• Fl_Group - Container base class