# Displays

These functions are declared in the main Allegro header file:

~~~~c
 #include <allegro5/allegro.h>
~~~~

## Display creation

### API: ALLEGRO_DISPLAY

An opaque type representing an open display or window.

### API: al_create_display

Create a display, or window, with the specified dimensions.
The parameters of the display are determined by the last calls to
al_set_new_display\_\*. Default parameters are used if none are set
explicitly.
Creating a new display will automatically make it the active one, with the
backbuffer selected for drawing. 

Returns NULL on error.

Each display has a distinct OpenGL rendering context associated with it. See
[al_set_target_bitmap] for the discussion about rendering contexts.

See also: [al_set_new_display_flags], [al_set_new_display_option],
[al_set_new_display_refresh_rate], [al_set_new_display_adapter],
[al_set_window_position]

### API: al_destroy_display

Destroy a display.

If the target bitmap of the calling thread is tied to the display, then it
implies a call to "al_set_target_bitmap(NULL);" before the display is
destroyed.

That special case notwithstanding, you should make sure no threads are
currently targeting a bitmap which is tied to the display before you destroy
it.

See also: [al_set_target_bitmap]

### API: al_get_new_display_flags

Get the display flags to be used when creating new displays on the calling
thread.

See also: [al_set_new_display_flags], [al_set_display_flag]

### API: al_set_new_display_flags

Sets various flags to be used when creating new displays on the calling thread.
flags is a bitfield containing any reasonable combination of the following:

ALLEGRO_WINDOWED
:   Prefer a windowed mode.

    Under multi-head X (not XRandR/TwinView), the use of more than one adapter is
    impossible due to bugs in X and GLX. [al_create_display] will fail if more than one
    adapter is attempted to be used.

ALLEGRO_FULLSCREEN
:   Prefer a fullscreen mode.

    Under X the use of more than one FULLSCREEN display when using multi-head X,
    or true Xinerama is not possible due to bugs in X and GLX,
    display creation will fail if more than one adapter is attempted to be used.

ALLEGRO_FULLSCREEN_WINDOW
:   Make the window span the entire screen. Unlike ALLEGRO_FULLSCREEN this
    will never attempt to modify the screen resolution. Instead the pixel
    dimensions of the created display will be the same as the desktop.

    The passed width and height are only used if the window is switched
    out of fullscreen mode later but will be ignored initially.

    Under Windows and X11 a fullscreen display created with this flag
    will behave differently from one created with the ALLEGRO_FULLSCREEN
    flag - even if the ALLEGRO_FULLSCREEN display is passed the desktop
    dimensions. The exact difference is platform dependent, but some
    things which may be different is how alt-tab works, how fast you can
    toggle between fullscreen/windowed mode or how additional monitors
    behave while your display is in fullscreen mode.

    Additionally under X, the use of more than one adapter in multi-head mode
    or with true Xinerama enabled is impossible due to bugs in X/GLX,
    creation will fail if more than one adapter is attempted to be used.

ALLEGRO_RESIZABLE
:   The display is resizable (only applicable if combined with
    ALLEGRO_WINDOWED).

ALLEGRO_OPENGL
:   Require the driver to provide an initialized OpenGL context after returning
    successfully.

ALLEGRO_OPENGL_3_0
:   Require the driver to provide an initialized OpenGL
    context compatible with OpenGL version 3.0.

ALLEGRO_OPENGL_FORWARD_COMPATIBLE
:   If this flag is set, the OpenGL
    context created with ALLEGRO_OPENGL_3_0 will be forward compatible *only*,
    meaning that all of the OpenGL API declared deprecated in OpenGL 3.0 will not
    be supported. Currently, a display created with this flag will *not* be
    compatible with Allegro drawing routines; the display option
    ALLEGRO_COMPATIBLE_DISPLAY will be set to false.

ALLEGRO_DIRECT3D
:   Require the driver to do rendering with Direct3D and
    provide a Direct3D device.

ALLEGRO_FRAMELESS
:   Try to create a window without a frame (i.e. no border or titlebar).
    This usually does nothing for fullscreen modes, and even in windowed modes
    it depends on the underlying platform whether it is supported or not.
    Since: 5.0.7, 5.1.2

ALLEGRO_NOFRAME
:   Original name for ALLEGRO_FRAMELESS.
    This works with older versions of Allegro.

ALLEGRO_GENERATE_EXPOSE_EVENTS
:   Let the display generate expose events.

0 can be used for default values.

See also: [al_set_new_display_option], [al_get_display_option], [al_change_display_option]

### API: al_get_new_display_option

Retrieve an extra display setting which was previously set with
[al_set_new_display_option].

### API: al_set_new_display_option

Set an extra display option, to be used when creating new displays on the
calling thread.  Display options differ from display flags, and specify some
details of the context to be created within the window itself.
These mainly have no effect on Allegro itself, but you may want to specify
them, for example if you want to use multisampling.

The 'importance' parameter can be either:

* ALLEGRO_REQUIRE - The display will not be created if the setting can
    not be met.
* ALLEGRO_SUGGEST - If the setting is not available, the display will
    be created anyway.
    FIXME: We need a way to query the settings back from a created display.
* ALLEGRO_DONTCARE - If you added a display option with one of the above
    two settings before, it will be removed again. Else this does
    nothing.

The supported options are:

ALLEGRO_COLOR_SIZE
:   This can be used to ask for a specific bit depth. For example to
    force a 16-bit framebuffer set this to 16.

ALLEGRO_RED_SIZE, ALLEGRO_GREEN_SIZE, ALLEGRO_BLUE_SIZE, ALLEGRO_ALPHA_SIZE
:   Individual color component size in bits.

ALLEGRO_RED_SHIFT, ALLEGRO_GREEN_SHIFT, ALLEGRO_BLUE_SHIFT, ALLEGRO_ALPHA_SHIFT
:   Together with the previous settings these can be used to specify the
    exact pixel layout the display should use. Normally there is no reason to use these.

ALLEGRO_ACC_RED_SIZE, ALLEGRO_ACC_GREEN_SIZE, ALLEGRO_ACC_BLUE_SIZE, ALLEGRO_ACC_ALPHA_SIZE
:   This can be used to define the required accumulation buffer size.
    
ALLEGRO_STEREO
:   Whether the display is a stereo display.

ALLEGRO_AUX_BUFFERS
:   Number of auxiliary buffers the display should
    have.

ALLEGRO_DEPTH_SIZE
:   How many depth buffer (z-buffer) bits to use.

ALLEGRO_STENCIL_SIZE
:   How many bits to use for the stencil buffer.

ALLEGRO_SAMPLE_BUFFERS
:   Whether to use multisampling (1) or not (0).

ALLEGRO_SAMPLES
:   If the above is 1, the number of samples to use
    per pixel. Else 0.

ALLEGRO_RENDER_METHOD:
:   0 if hardware acceleration is not used with this display.

ALLEGRO_FLOAT_COLOR
:   Whether to use floating point color components.

ALLEGRO_FLOAT_DEPTH
:   Whether to use a floating point depth buffer.

ALLEGRO_SINGLE_BUFFER
:   Whether the display uses a single buffer (1)
    or another update method (0).

ALLEGRO_SWAP_METHOD
:   If the above is 0, this is set to 1 to indicate
    the display is using a copying method to make the next buffer in
    the flip chain available, or to 2 to indicate a flipping or other
    method.

ALLEGRO_COMPATIBLE_DISPLAY
:   Indicates if Allegro's graphics
    functions can use this display. If you request a display not
    useable by Allegro, you can still use for example OpenGL to draw
    graphics.

ALLEGRO_UPDATE_DISPLAY_REGION
:   Set to 1 if the display is
    capable of updating just a region, and 0 if calling
    [al_update_display_region] is equivalent to [al_flip_display].

ALLEGRO_VSYNC
:   Set to 1 to tell the driver to wait for vsync
    in [al_flip_display], or to 2 to force vsync off. The default of
    0 means that Allegro does not try to modify the vsync behavior so
    it may be on or off.
    Note that even in the case of 1 or 2 it is possible to override
    the vsync behavior in the graphics driver so you should not rely
    on it.

ALLEGRO_MAX_BITMAP_SIZE
:   When queried this returns the maximum
    size (width as well as height) a bitmap can have for this
    display. Calls to [al_create_bitmap] or [al_load_bitmap] for
    bitmaps larger than this size will fail. It does not apply to memory
    bitmaps which always can have arbitrary size (but are slow for
    drawing).

ALLEGRO_SUPPORT_NPOT_BITMAP
:   Set to 1 if textures used for bitmaps
    on this display can have a size which is not a power of two. This
    is mostly useful if you use Allegro to load textures as otherwise
    only power-of-two textures will be used internally as bitmap
    storage.

ALLEGRO_CAN_DRAW_INTO_BITMAP
:   Set to 1 if you can use
    [al_set_target_bitmap] on bitmaps of this display to draw into them.
    If this is not the case software emulation will be used when drawing
    into display bitmaps (which can be very slow).

ALLEGRO_SUPPORT_SEPARATE_ALPHA
:   This is set to 1 if the
    [al_set_separate_blender] function is supported. Otherwise the
    alpha parameters will be ignored.

See also: [al_set_new_display_flags]

### API: al_reset_new_display_options

This undoes any previous call to [al_set_new_display_option]
on the calling thread.

### API: al_get_new_window_position

Get the position where new non-fullscreen displays created by the calling
thread will be placed.

See also: [al_set_new_window_position]

### API: al_set_new_window_position

Sets where the top left pixel of the client area of newly
created windows (non-fullscreen) will be on screen,
for displays created by the calling thread.
Negative values allowed on some multihead systems.

To reset to the default behaviour, pass (INT_MAX, INT_MAX).

See also: [al_get_new_window_position]

### API: al_get_new_display_refresh_rate

Get the requested refresh rate to be used when creating new displays on the
calling thread.

See also: [al_set_new_display_refresh_rate]

### API: al_set_new_display_refresh_rate

Sets the refresh rate to use when creating new displays on the calling thread.
If the refresh rate is not available, [al_create_display] will fail.
A list of modes with refresh rates can be found with [al_get_num_display_modes]
and [al_get_display_mode].

The default setting is zero (don't care).

See also: [al_get_new_display_refresh_rate]



## Display operations

### API: al_get_display_event_source

Retrieve the associated event source.

### API: al_get_backbuffer

Return a special bitmap representing the back-buffer of the
display.

Care should be taken when using the backbuffer bitmap (and its
sub-bitmaps) as the source bitmap (e.g as the bitmap argument to
[al_draw_bitmap]). Only untransformed operations are hardware
accelerated. This consists of [al_draw_bitmap] and
[al_draw_bitmap_region] when the current transformation is the identity.
If the tranformation is not the identity, or some other drawing
operation is used, the call will be routed through the memory bitmap
routines, which are slow. If you need those operations to be accelerated,
then first copy a region of the backbuffer into a temporary bitmap (via
the [al_draw_bitmap] and [al_draw_bitmap_region]), and then use that
temporary bitmap as the source bitmap.

### API: al_flip_display

Copies or updates the front and back buffers so that what has
been drawn previously on the currently selected display becomes
visible on screen. Pointers to the special back buffer
bitmap remain valid and retain their semantics as the back buffer,
although the contents may have changed.

Several display options change how this function behaves:

- With ALLEGRO_SINGLE_BUFFER, no flipping is done. You still have to
call this function to display graphics, depending on how the used
graphics system works.

- The ALLEGRO_SWAP_METHOD option may have additional information about what
kind of operation is used internally to flip the front and back buffers.

- If ALLEGRO_VSYNC is 1, this function will force waiting for vsync. If
ALLEGRO_VSYNC is 2, this function will not wait for vsync. With many
drivers the vsync behavior is controlled by the user and not the
application, and ALLEGRO_VSYNC will not be set; in this case
[al_flip_display] will wait for vsync depending on the settings set
in the system's graphics preferences.

See also: [al_set_new_display_flags], [al_set_new_display_option]

### API: al_update_display_region

Does the same as [al_flip_display], but tries to update only the
specified region. With many drivers this is not possible, but for
some it can improve performance. If this is not supported, this function falls
back to the behavior of [al_flip_display]. You can query the support for this
function using `al_get_display_option(display, ALLEGRO_UPDATE_DISPLAY_REGION)`.

See also: [al_flip_display], [al_get_display_option]

### API: al_wait_for_vsync

Wait for the beginning of a vertical retrace. Some
driver/card/monitor combinations may not be capable
of this.

Note how [al_flip_display] usually already waits for the vertical
retrace, so unless you are doing something special, there is no reason
to call this function.

Returns false if not possible, true if successful.

See also: [al_flip_display]



## Display size and position

### API: al_get_display_width

Gets the width of the display. This is like SCREEN_W in Allegro 4.x.

See also: [al_get_display_height]

### API: al_get_display_height

Gets the height of the display. This is like SCREEN_H in Allegro 4.x.

See also: [al_get_display_width]

### API: al_resize_display

Resize the display. Returns true on success, or false on error.
This works on both fullscreen and windowed displays, regardless of the
ALLEGRO_RESIZABLE flag.

Adjusts the clipping rectangle to the full size of the backbuffer.

See also: [al_acknowledge_resize]

### API: al_acknowledge_resize

When the user receives a resize event from a resizable display,
if they wish the display to be resized they must call this
function to let the graphics driver know that it can now resize
the display. Returns true on success.

Adjusts the clipping rectangle to the full size of the backbuffer.

Note that a resize event may be outdated by the time you acknowledge it;
there could be further resize events generated in the meantime.

See also: [al_resize_display], [ALLEGRO_EVENT]

### API: al_get_window_position

Gets the position of a non-fullscreen display.

See also: [al_set_window_position]

### API: al_set_window_position

Sets the position on screen of a non-fullscreen display.

See also: [al_get_window_position]



## Display settings

### API: al_get_display_flags

Gets the flags of the display.

In addition to the flags set for the display at creation time with
[al_set_new_display_flags] it can also have the ALLEGRO_MINIMIZED flag
set, indicating that the window is currently minimized. This flag
is very platform-dependent as even a minimized application may still
render a preview version so normally you should not care whether it
is minimized or not.

See also: [al_set_new_display_flags], [al_set_display_flag]

### API: al_set_display_flag

Enable or disable one of the display flags. The flags are the same
as for [al_set_new_display_flags]. The only flags that can be changed
after creation are:

- ALLEGRO_FULLSCREEN_WINDOW
- ALLEGRO_FRAMELESS

Returns true if the driver supports toggling the specified flag else
false. You can use [al_get_display_flags] to query whether the given
display property actually changed.

Since: 5.0.7, 5.1.2

See also: [al_set_new_display_flags], [al_get_display_flags]

### API: al_toggle_display_flag

Deprecated synonym for [al_set_display_flag].

### API: al_get_display_option

Return an extra display setting of the display.

See also: [al_set_new_display_option]

### API: al_get_display_format

Gets the pixel format of the display.

See also: [ALLEGRO_PIXEL_FORMAT]

### API: al_get_display_refresh_rate

Gets the refresh rate of the display.

See also: [al_set_new_display_refresh_rate]

### API: al_set_window_title

Set the title on a display.

See also: [al_set_display_icon], [al_set_display_icons]

### API: al_set_display_icon

Changes the icon associated with the display (window).
Same as [al_set_display_icons] with one icon.

See also: [al_set_display_icons], [al_set_window_title]

### API: al_set_display_icons

Changes the icons associated with the display (window).
Multiple icons can be provided for use in different contexts, e.g. window
frame, taskbar, alt-tab popup.  The number of icons must be at least one.

> *Note:* If the underlying OS requires an icon of a size not provided
then one of the bitmaps will be scaled up or down to the required size.
The choice of bitmap is implementation dependent.

Since: 5.0.9, 5.1.5

See also: [al_set_display_icon], [al_set_window_title]



## Screensaver

### API: al_inhibit_screensaver

This function allows the user to stop the system
screensaver from starting up if true is passed,
or resets the system back to the default state
(the state at program start) if false is passed.
It returns true if the state was set successfully,
otherwise false.
