glfw/docs/window.md

# Window guide {#window_guide}

[TOC]

This guide introduces the window related functions of GLFW.  For details on
a specific function in this category, see the @ref window.  There are also
guides for the other areas of GLFW.

 - @ref intro_guide
 - @ref context_guide
 - @ref vulkan_guide
 - @ref monitor_guide
 - @ref input_guide


## Window objects {#window_object}

The @ref GLFWwindow object encapsulates both a window and a context.  They are
created with @ref glfwCreateWindow and destroyed with @ref glfwDestroyWindow, or
@ref glfwTerminate, if any remain.  As the window and context are inseparably
linked, the object pointer is used as both a context and window handle.

To see the event stream provided to the various window related callbacks, run
the `events` test program.


### Window creation {#window_creation}

A window and its OpenGL or OpenGL ES context are created with @ref
glfwCreateWindow, which returns a handle to the created window object.  For
example, this creates a 640 by 480 windowed mode window:

```c
GLFWwindow* window = glfwCreateWindow(640, 480, "My Title", NULL, NULL);
```

If window creation fails, `NULL` will be returned, so it is necessary to check
the return value.

The window handle is passed to all window related functions and is provided to
along with all input events, so event handlers can tell which window received
the event.


#### Full screen windows {#window_full_screen}

To create a full screen window, you need to specify which monitor the window
should use.  In most cases, the user's primary monitor is a good choice.
For more information about retrieving monitors, see @ref monitor_monitors.

```c
GLFWwindow* window = glfwCreateWindow(640, 480, "My Title", glfwGetPrimaryMonitor(), NULL);
```

Full screen windows cover the entire display area of a monitor, have no border
or decorations.

Windowed mode windows can be made full screen by setting a monitor with @ref
glfwSetWindowMonitor, and full screen ones can be made windowed by unsetting it
with the same function.

Each field of the @ref GLFWvidmode structure corresponds to a function parameter
or window hint and combine to form the _desired video mode_ for that window.
The supported video mode most closely matching the desired video mode will be
set for the chosen monitor as long as the window has input focus.  For more
information about retrieving video modes, see @ref monitor_modes.

Video mode field        | Corresponds to
----------------        | --------------
GLFWvidmode.width       | `width` parameter of @ref glfwCreateWindow
GLFWvidmode.height      | `height` parameter of @ref glfwCreateWindow
GLFWvidmode.redBits     | @ref GLFW_RED_BITS hint
GLFWvidmode.greenBits   | @ref GLFW_GREEN_BITS hint
GLFWvidmode.blueBits    | @ref GLFW_BLUE_BITS hint
GLFWvidmode.refreshRate | @ref GLFW_REFRESH_RATE hint

Once you have a full screen window, you can change its resolution, refresh rate
and monitor with @ref glfwSetWindowMonitor.  If you only need change its
resolution you can also call @ref glfwSetWindowSize.  In all cases, the new
video mode will be selected the same way as the video mode chosen by @ref
glfwCreateWindow.  If the window has an OpenGL or OpenGL ES context, it will be
unaffected.

By default, the original video mode of the monitor will be restored and the
window iconified if it loses input focus, to allow the user to switch back to
the desktop.  This behavior can be disabled with the
[GLFW_AUTO_ICONIFY](@ref GLFW_AUTO_ICONIFY_hint) window hint, for example if you
wish to simultaneously cover multiple monitors with full screen windows.

If a monitor is disconnected, all windows that are full screen on that monitor
will be switched to windowed mode.  See @ref monitor_event for more information.


#### "Windowed full screen" windows {#window_windowed_full_screen}

If the closest match for the desired video mode is the current one, the video
mode will not be changed, making window creation faster and application
switching much smoother.  This is sometimes called _windowed full screen_ or
_borderless full screen_ window and counts as a full screen window.  To create
such a window, request the current video mode.

```c
const GLFWvidmode* mode = glfwGetVideoMode(monitor);

glfwWindowHint(GLFW_RED_BITS, mode->redBits);
glfwWindowHint(GLFW_GREEN_BITS, mode->greenBits);
glfwWindowHint(GLFW_BLUE_BITS, mode->blueBits);
glfwWindowHint(GLFW_REFRESH_RATE, mode->refreshRate);

GLFWwindow* window = glfwCreateWindow(mode->width, mode->height, "My Title", monitor, NULL);
```

This also works for windowed mode windows that are made full screen.

```c
const GLFWvidmode* mode = glfwGetVideoMode(monitor);

glfwSetWindowMonitor(window, monitor, 0, 0, mode->width, mode->height, mode->refreshRate);
```

Note that @ref glfwGetVideoMode returns the _current_ video mode of a monitor,
so if you already have a full screen window on that monitor that you want to
make windowed full screen, you need to have saved the desktop resolution before.


### Window destruction {#window_destruction}

When a window is no longer needed, destroy it with @ref glfwDestroyWindow.

```c
glfwDestroyWindow(window);
```

Window destruction always succeeds.  Before the actual destruction, all
callbacks are removed so no further events will be delivered for the window.
All windows remaining when @ref glfwTerminate is called are destroyed as well.

When a full screen window is destroyed, the original video mode of its monitor
is restored, but the gamma ramp is left untouched.


### Window creation hints {#window_hints}

There are a number of hints that can be set before the creation of a window and
context.  Some affect the window itself, others affect the framebuffer or
context.  These hints are set to their default values each time the library is
initialized with @ref glfwInit.  Integer value hints can be set individually
with @ref glfwWindowHint and string value hints with @ref glfwWindowHintString.
You can reset all at once to their defaults with @ref glfwDefaultWindowHints.

Some hints are platform specific.  These are always valid to set on any
platform but they will only affect their specific platform.  Other platforms
will ignore them.  Setting these hints requires no platform specific headers or
calls.

@note Window hints need to be set before the creation of the window and context
you wish to have the specified attributes.  They function as additional
arguments to @ref glfwCreateWindow.


#### Hard and soft constraints {#window_hints_hard}

Some window hints are hard constraints.  These must match the available
capabilities _exactly_ for window and context creation to succeed.  Hints
that are not hard constraints are matched as closely as possible, but the
resulting context and framebuffer may differ from what these hints requested.

The following hints are always hard constraints:
- @ref GLFW_STEREO
- @ref GLFW_DOUBLEBUFFER
- [GLFW_CLIENT_API](@ref GLFW_CLIENT_API_hint)
- [GLFW_CONTEXT_CREATION_API](@ref GLFW_CONTEXT_CREATION_API_hint)

The following additional hints are hard constraints when requesting an OpenGL
context, but are ignored when requesting an OpenGL ES context:
- [GLFW_OPENGL_FORWARD_COMPAT](@ref GLFW_OPENGL_FORWARD_COMPAT_hint)
- [GLFW_OPENGL_PROFILE](@ref GLFW_OPENGL_PROFILE_hint)


#### Window related hints {#window_hints_wnd}

@anchor GLFW_RESIZABLE_hint
__GLFW_RESIZABLE__ specifies whether the windowed mode window will be resizable
_by the user_.  The window will still be resizable using the @ref
glfwSetWindowSize function.  Possible values are `GLFW_TRUE` and `GLFW_FALSE`.
This hint is ignored for full screen and undecorated windows.

@anchor GLFW_VISIBLE_hint
__GLFW_VISIBLE__ specifies whether the windowed mode window will be initially
visible.  Possible values are `GLFW_TRUE` and `GLFW_FALSE`.  This hint is
ignored for full screen windows.

@anchor GLFW_DECORATED_hint
__GLFW_DECORATED__ specifies whether the windowed mode window will have window
decorations such as a border, a close widget, etc.  An undecorated window will
not be resizable by the user but will still allow the user to generate close
events on some platforms.  Possible values are `GLFW_TRUE` and `GLFW_FALSE`.
This hint is ignored for full screen windows.

@anchor GLFW_FOCUSED_hint
__GLFW_FOCUSED__ specifies whether the windowed mode window will be given input
focus when created.  Possible values are `GLFW_TRUE` and `GLFW_FALSE`.  This
hint is ignored for full screen and initially hidden windows.

@anchor GLFW_AUTO_ICONIFY_hint
__GLFW_AUTO_ICONIFY__ specifies whether the full screen window will
automatically iconify and restore the previous video mode on input focus loss.
Possible values are `GLFW_TRUE` and `GLFW_FALSE`.  This hint is ignored for
windowed mode windows.

@anchor GLFW_FLOATING_hint
__GLFW_FLOATING__ specifies whether the windowed mode window will be floating
above other regular windows, also called topmost or always-on-top.  This is
intended primarily for debugging purposes and cannot be used to implement proper
full screen windows.  Possible values are `GLFW_TRUE` and `GLFW_FALSE`.  This
hint is ignored for full screen windows.

@anchor GLFW_MAXIMIZED_hint
__GLFW_MAXIMIZED__ specifies whether the windowed mode window will be maximized
when created.  Possible values are `GLFW_TRUE` and `GLFW_FALSE`.  This hint is
ignored for full screen windows.

@anchor GLFW_CENTER_CURSOR_hint
__GLFW_CENTER_CURSOR__ specifies whether the cursor should be centered over
newly created full screen windows.  Possible values are `GLFW_TRUE` and
`GLFW_FALSE`.  This hint is ignored for windowed mode windows.

@anchor GLFW_TRANSPARENT_FRAMEBUFFER_hint
__GLFW_TRANSPARENT_FRAMEBUFFER__ specifies whether the window framebuffer will
be transparent.  If enabled and supported by the system, the window framebuffer
alpha channel will be used to combine the framebuffer with the background.  This
does not affect window decorations.  Possible values are `GLFW_TRUE` and
`GLFW_FALSE`.

@anchor GLFW_FOCUS_ON_SHOW_hint
__GLFW_FOCUS_ON_SHOW__ specifies whether the window will be given input
focus when @ref glfwShowWindow is called. Possible values are `GLFW_TRUE` and
`GLFW_FALSE`.

@anchor GLFW_SCALE_TO_MONITOR
__GLFW_SCALE_TO_MONITOR__ specified whether the window content area should be
resized based on [content scale](@ref window_scale) changes.  This can be
because of a global user settings change or because the window was moved to
a monitor with different scale settings.

This hint only has an effect on platforms where screen coordinates and pixels
always map 1:1, such as Windows and X11.  On platforms like macOS the resolution
of the framebuffer can change independently of the window size.

@anchor GLFW_SCALE_FRAMEBUFFER_hint
@anchor GLFW_COCOA_RETINA_FRAMEBUFFER_hint
__GLFW_SCALE_FRAMEBUFFER__ specifies whether the framebuffer should be resized
based on [content scale](@ref window_scale) changes.  This can be
because of a global user settings change or because the window was moved to
a monitor with different scale settings.

This hint only has an effect on platforms where screen coordinates can be scaled
relative to pixel coordinates, such as macOS and Wayland.  On platforms like
Windows and X11 the framebuffer and window content area sizes always map 1:1.

This is the new name, introduced in GLFW 3.4.  The older
`GLFW_COCOA_RETINA_FRAMEBUFFER` name is also available for compatibility.  Both
names modify the same hint value.

@anchor GLFW_MOUSE_PASSTHROUGH_hint
__GLFW_MOUSE_PASSTHROUGH__ specifies whether the window is transparent to mouse
input, letting any mouse events pass through to whatever window is behind it.
This is only supported for undecorated windows.  Decorated windows with this
enabled will behave differently between platforms.  Possible values are
`GLFW_TRUE` and `GLFW_FALSE`.

@anchor GLFW_POSITION_X
@anchor GLFW_POSITION_Y
__GLFW_POSITION_X__ and __GLFW_POSITION_Y__ specify the desired initial position
of the window.  The window manager may modify or ignore these coordinates.  If
either or both of these hints are set to `GLFW_ANY_POSITION` then the window
manager will position the window where it thinks the user will prefer it.
Possible values are any valid screen coordinates and `GLFW_ANY_POSITION`.


#### Framebuffer related hints {#window_hints_fb}

@anchor GLFW_RED_BITS
@anchor GLFW_GREEN_BITS
@anchor GLFW_BLUE_BITS
@anchor GLFW_ALPHA_BITS
@anchor GLFW_DEPTH_BITS
@anchor GLFW_STENCIL_BITS
__GLFW_RED_BITS__, __GLFW_GREEN_BITS__, __GLFW_BLUE_BITS__, __GLFW_ALPHA_BITS__,
__GLFW_DEPTH_BITS__ and __GLFW_STENCIL_BITS__ specify the desired bit depths of
the various components of the default framebuffer.  A value of `GLFW_DONT_CARE`
means the application has no preference.

@anchor GLFW_ACCUM_RED_BITS
@anchor GLFW_ACCUM_GREEN_BITS
@anchor GLFW_ACCUM_BLUE_BITS
@anchor GLFW_ACCUM_ALPHA_BITS
__GLFW_ACCUM_RED_BITS__, __GLFW_ACCUM_GREEN_BITS__, __GLFW_ACCUM_BLUE_BITS__ and
__GLFW_ACCUM_ALPHA_BITS__ specify the desired bit depths of the various
components of the accumulation buffer.  A value of `GLFW_DONT_CARE` means the
application has no preference.

Accumulation buffers are a legacy OpenGL feature and should not be used in new
code.

@anchor GLFW_AUX_BUFFERS
__GLFW_AUX_BUFFERS__ specifies the desired number of auxiliary buffers.  A value
of `GLFW_DONT_CARE` means the application has no preference.

Auxiliary buffers are a legacy OpenGL feature and should not be used in new
code.

@anchor GLFW_STEREO
__GLFW_STEREO__ specifies whether to use OpenGL stereoscopic rendering.
Possible values are `GLFW_TRUE` and `GLFW_FALSE`.  This is a hard constraint.

@anchor GLFW_SAMPLES
__GLFW_SAMPLES__ specifies the desired number of samples to use for
multisampling.  Zero disables multisampling.  A value of `GLFW_DONT_CARE` means
the application has no preference.

@anchor GLFW_SRGB_CAPABLE
__GLFW_SRGB_CAPABLE__ specifies whether the framebuffer should be sRGB capable.
Possible values are `GLFW_TRUE` and `GLFW_FALSE`.

@note __OpenGL:__ If enabled and supported by the system, the
`GL_FRAMEBUFFER_SRGB` enable will control sRGB rendering.  By default, sRGB
rendering will be disabled.

@note __OpenGL ES:__ If enabled and supported by the system, the context will
always have sRGB rendering enabled.

@anchor GLFW_DOUBLEBUFFER
@anchor GLFW_DOUBLEBUFFER_hint
__GLFW_DOUBLEBUFFER__ specifies whether the framebuffer should be double
buffered.  You nearly always want to use double buffering.  This is a hard
constraint.  Possible values are `GLFW_TRUE` and `GLFW_FALSE`.


#### Monitor related hints {#window_hints_mtr}

@anchor GLFW_REFRESH_RATE
__GLFW_REFRESH_RATE__ specifies the desired refresh rate for full screen
windows.  A value of `GLFW_DONT_CARE` means the highest available refresh rate
will be used.  This hint is ignored for windowed mode windows.


#### Context related hints {#window_hints_ctx}

@anchor GLFW_CLIENT_API_hint
__GLFW_CLIENT_API__ specifies which client API to create the context for.
Possible values are `GLFW_OPENGL_API`, `GLFW_OPENGL_ES_API` and `GLFW_NO_API`.
This is a hard constraint.

@anchor GLFW_CONTEXT_CREATION_API_hint
__GLFW_CONTEXT_CREATION_API__ specifies which context creation API to use to
create the context.  Possible values are `GLFW_NATIVE_CONTEXT_API`,
`GLFW_EGL_CONTEXT_API` and `GLFW_OSMESA_CONTEXT_API`.  This is a hard
constraint.  If no client API is requested, this hint is ignored.

An [extension loader library](@ref context_glext_auto) that assumes it knows
which API was used to create the current context may fail if you change this
hint.  This can be resolved by having it load functions via @ref
glfwGetProcAddress.

@note @wayland The EGL API _is_ the native context creation API, so this hint
will have no effect.

@note @x11 On some Linux systems, creating contexts via both the native and EGL
APIs in a single process will cause the application to segfault.  Stick to one
API or the other on Linux for now.

@note __OSMesa:__ As its name implies, an OpenGL context created with OSMesa
does not update the window contents when its buffers are swapped.  Use OpenGL
functions or the OSMesa native access functions @ref glfwGetOSMesaColorBuffer
and @ref glfwGetOSMesaDepthBuffer to retrieve the framebuffer contents.

@anchor GLFW_CONTEXT_VERSION_MAJOR_hint
@anchor GLFW_CONTEXT_VERSION_MINOR_hint
__GLFW_CONTEXT_VERSION_MAJOR__ and __GLFW_CONTEXT_VERSION_MINOR__ specify the
client API version that the created context must be compatible with.  The exact
behavior of these hints depend on the requested client API.

While there is no way to ask the driver for a context of the highest supported
version, GLFW will attempt to provide this when you ask for a version 1.0
context, which is the default for these hints.

Do not confuse these hints with @ref GLFW_VERSION_MAJOR and @ref
GLFW_VERSION_MINOR, which provide the API version of the GLFW header.

@note __OpenGL:__ These hints are not hard constraints, but creation will fail
if the OpenGL version of the created context is less than the one requested.  It
is therefore perfectly safe to use the default of version 1.0 for legacy code
and you will still get backwards-compatible contexts of version 3.0 and above
when available.

@note __OpenGL ES:__ These hints are not hard constraints, but creation will
fail if the OpenGL ES version of the created context is less than the one
requested.  Additionally, OpenGL ES 1.x cannot be returned if 2.0 or later was
requested, and vice versa.  This is because OpenGL ES 3.x is backward compatible
with 2.0, but OpenGL ES 2.0 is not backward compatible with 1.x.

@note @macos The OS only supports core profile contexts for OpenGL versions 3.2
and later.  Before creating an OpenGL context of version 3.2 or later you must
set the [GLFW_OPENGL_PROFILE](@ref GLFW_OPENGL_PROFILE_hint) hint accordingly.
OpenGL 3.0 and 3.1 contexts are not supported at all on macOS.

@anchor GLFW_OPENGL_FORWARD_COMPAT_hint
__GLFW_OPENGL_FORWARD_COMPAT__ specifies whether the OpenGL context should be
forward-compatible, i.e. one where all functionality deprecated in the requested
version of OpenGL is removed.  This must only be used if the requested OpenGL
version is 3.0 or above.  If OpenGL ES is requested, this hint is ignored.

Forward-compatibility is described in detail in the
[OpenGL Reference Manual](https://www.opengl.org/registry/).

@anchor GLFW_CONTEXT_DEBUG_hint
@anchor GLFW_OPENGL_DEBUG_CONTEXT_hint
__GLFW_CONTEXT_DEBUG__ specifies whether the context should be created in debug
mode, which may provide additional error and diagnostic reporting functionality.
Possible values are `GLFW_TRUE` and `GLFW_FALSE`.

Debug contexts for OpenGL and OpenGL ES are described in detail by the
[GL_KHR_debug][] extension.

[GL_KHR_debug]: https://www.khronos.org/registry/OpenGL/extensions/KHR/KHR_debug.txt

@note `GLFW_CONTEXT_DEBUG` is the new name introduced in GLFW 3.4.  The older
`GLFW_OPENGL_DEBUG_CONTEXT` name is also available for compatibility.

@anchor GLFW_OPENGL_PROFILE_hint
__GLFW_OPENGL_PROFILE__ specifies which OpenGL profile to create the context
for.  Possible values are one of `GLFW_OPENGL_CORE_PROFILE` or
`GLFW_OPENGL_COMPAT_PROFILE`, or `GLFW_OPENGL_ANY_PROFILE` to not request
a specific profile.  If requesting an OpenGL version below 3.2,
`GLFW_OPENGL_ANY_PROFILE` must be used.  If OpenGL ES is requested, this hint
is ignored.

OpenGL profiles are described in detail in the
[OpenGL Reference Manual](https://www.opengl.org/registry/).

@anchor GLFW_CONTEXT_ROBUSTNESS_hint
__GLFW_CONTEXT_ROBUSTNESS__ specifies the robustness strategy to be used by the
context.  This can be one of `GLFW_NO_RESET_NOTIFICATION` or
`GLFW_LOSE_CONTEXT_ON_RESET`, or `GLFW_NO_ROBUSTNESS` to not request
a robustness strategy.

@anchor GLFW_CONTEXT_RELEASE_BEHAVIOR_hint
__GLFW_CONTEXT_RELEASE_BEHAVIOR__ specifies the release behavior to be
used by the context.  Possible values are one of `GLFW_ANY_RELEASE_BEHAVIOR`,
`GLFW_RELEASE_BEHAVIOR_FLUSH` or `GLFW_RELEASE_BEHAVIOR_NONE`.  If the
behavior is `GLFW_ANY_RELEASE_BEHAVIOR`, the default behavior of the context
creation API will be used.  If the behavior is `GLFW_RELEASE_BEHAVIOR_FLUSH`,
the pipeline will be flushed whenever the context is released from being the
current one.  If the behavior is `GLFW_RELEASE_BEHAVIOR_NONE`, the pipeline will
not be flushed on release.

Context release behaviors are described in detail by the
[GL_KHR_context_flush_control][] extension.

[GL_KHR_context_flush_control]: https://www.opengl.org/registry/specs/KHR/context_flush_control.txt

@anchor GLFW_CONTEXT_NO_ERROR_hint
__GLFW_CONTEXT_NO_ERROR__ specifies whether errors should be generated by the
context.  Possible values are `GLFW_TRUE` and `GLFW_FALSE`.  If enabled,
situations that would have generated errors instead cause undefined behavior.

The no error mode for OpenGL and OpenGL ES is described in detail by the
[GL_KHR_no_error][] extension.

[GL_KHR_no_error]: https://www.opengl.org/registry/specs/KHR/no_error.txt


#### Win32 specific hints {#window_hints_win32}

@anchor GLFW_WIN32_KEYBOARD_MENU_hint
__GLFW_WIN32_KEYBOARD_MENU__ specifies whether to allow access to the window
menu via the Alt+Space and Alt-and-then-Space keyboard shortcuts.  This is
ignored on other platforms.

@anchor GLFW_WIN32_SHOWDEFAULT_hint
__GLFW_WIN32_SHOWDEFAULT__ specifies whether to show the window the way
specified in the program's `STARTUPINFO` when it is shown for the first time.
This is the same information as the `Run` option in the shortcut properties
window.  If this information was not specified when the program was started,
GLFW behaves as if this hint was set to `GLFW_FALSE`.  Possible values are
`GLFW_TRUE` and `GLFW_FALSE`.  This is ignored on other platforms.


#### macOS specific hints {#window_hints_osx}

@anchor GLFW_COCOA_FRAME_NAME_hint
__GLFW_COCOA_FRAME_NAME__ specifies the UTF-8 encoded name to use for autosaving
the window frame, or if empty disables frame autosaving for the window.  This is
ignored on other platforms.  This is set with @ref glfwWindowHintString.

@anchor GLFW_COCOA_GRAPHICS_SWITCHING_hint
__GLFW_COCOA_GRAPHICS_SWITCHING__ specifies whether to in Automatic Graphics
Switching, i.e. to allow the system to choose the integrated GPU for the OpenGL
context and move it between GPUs if necessary or whether to force it to always
run on the discrete GPU.  This only affects systems with both integrated and
discrete GPUs.  Possible values are `GLFW_TRUE` and `GLFW_FALSE`.  This is
ignored on other platforms.

Simpler programs and tools may want to enable this to save power, while games
and other applications performing advanced rendering will want to leave it
disabled.

A bundled application that wishes to participate in Automatic Graphics Switching
should also declare this in its `Info.plist` by setting the
`NSSupportsAutomaticGraphicsSwitching` key to `true`.


#### Wayland specific window hints {#window_hints_wayland}

@anchor GLFW_WAYLAND_APP_ID_hint
__GLFW_WAYLAND_APP_ID__ specifies the Wayland app_id for a window, used
by window managers to identify types of windows. This is set with
@ref glfwWindowHintString.


#### X11 specific window hints {#window_hints_x11}

@anchor GLFW_X11_CLASS_NAME_hint
@anchor GLFW_X11_INSTANCE_NAME_hint
__GLFW_X11_CLASS_NAME__ and __GLFW_X11_INSTANCE_NAME__ specifies the desired
ASCII encoded class and instance parts of the ICCCM `WM_CLASS` window property.  Both
hints need to be set to something other than an empty string for them to take effect.
These are set with @ref glfwWindowHintString.


#### Supported and default values {#window_hints_values}

Window hint                   | Default value               | Supported values
----------------------------- | --------------------------- | ----------------
GLFW_RESIZABLE                | `GLFW_TRUE`                 | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_VISIBLE                  | `GLFW_TRUE`                 | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_DECORATED                | `GLFW_TRUE`                 | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_FOCUSED                  | `GLFW_TRUE`                 | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_AUTO_ICONIFY             | `GLFW_TRUE`                 | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_FLOATING                 | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_MAXIMIZED                | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_CENTER_CURSOR            | `GLFW_TRUE`                 | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_TRANSPARENT_FRAMEBUFFER  | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_FOCUS_ON_SHOW            | `GLFW_TRUE`                 | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_SCALE_TO_MONITOR         | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_SCALE_FRAMEBUFFER        | `GLFW_TRUE`                 | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_MOUSE_PASSTHROUGH        | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_POSITION_X               | `GLFW_ANY_POSITION`         | Any valid screen x-coordinate or `GLFW_ANY_POSITION`
GLFW_POSITION_Y               | `GLFW_ANY_POSITION`         | Any valid screen y-coordinate or `GLFW_ANY_POSITION`
GLFW_RED_BITS                 | 8                           | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_GREEN_BITS               | 8                           | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_BLUE_BITS                | 8                           | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_ALPHA_BITS               | 8                           | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_DEPTH_BITS               | 24                          | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_STENCIL_BITS             | 8                           | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_ACCUM_RED_BITS           | 0                           | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_ACCUM_GREEN_BITS         | 0                           | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_ACCUM_BLUE_BITS          | 0                           | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_ACCUM_ALPHA_BITS         | 0                           | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_AUX_BUFFERS              | 0                           | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_SAMPLES                  | 0                           | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_REFRESH_RATE             | `GLFW_DONT_CARE`            | 0 to `INT_MAX` or `GLFW_DONT_CARE`
GLFW_STEREO                   | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_SRGB_CAPABLE             | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_DOUBLEBUFFER             | `GLFW_TRUE`                 | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_CLIENT_API               | `GLFW_OPENGL_API`           | `GLFW_OPENGL_API`, `GLFW_OPENGL_ES_API` or `GLFW_NO_API`
GLFW_CONTEXT_CREATION_API     | `GLFW_NATIVE_CONTEXT_API`   | `GLFW_NATIVE_CONTEXT_API`, `GLFW_EGL_CONTEXT_API` or `GLFW_OSMESA_CONTEXT_API`
GLFW_CONTEXT_VERSION_MAJOR    | 1                           | Any valid major version number of the chosen client API
GLFW_CONTEXT_VERSION_MINOR    | 0                           | Any valid minor version number of the chosen client API
GLFW_CONTEXT_ROBUSTNESS       | `GLFW_NO_ROBUSTNESS`        | `GLFW_NO_ROBUSTNESS`, `GLFW_NO_RESET_NOTIFICATION` or `GLFW_LOSE_CONTEXT_ON_RESET`
GLFW_CONTEXT_RELEASE_BEHAVIOR | `GLFW_ANY_RELEASE_BEHAVIOR` | `GLFW_ANY_RELEASE_BEHAVIOR`, `GLFW_RELEASE_BEHAVIOR_FLUSH` or `GLFW_RELEASE_BEHAVIOR_NONE`
GLFW_OPENGL_FORWARD_COMPAT    | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_CONTEXT_DEBUG            | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_OPENGL_PROFILE           | `GLFW_OPENGL_ANY_PROFILE`   | `GLFW_OPENGL_ANY_PROFILE`, `GLFW_OPENGL_COMPAT_PROFILE` or `GLFW_OPENGL_CORE_PROFILE`
GLFW_WIN32_KEYBOARD_MENU      | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_WIN32_SHOWDEFAULT        | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_COCOA_FRAME_NAME         | `""`                        | A UTF-8 encoded frame autosave name
GLFW_COCOA_GRAPHICS_SWITCHING | `GLFW_FALSE`                | `GLFW_TRUE` or `GLFW_FALSE`
GLFW_WAYLAND_APP_ID           | `""`                        | An ASCII encoded Wayland `app_id` name
GLFW_X11_CLASS_NAME           | `""`                        | An ASCII encoded `WM_CLASS` class name
GLFW_X11_INSTANCE_NAME        | `""`                        | An ASCII encoded `WM_CLASS` instance name


## Window event processing {#window_events}

See @ref events.


## Window properties and events {#window_properties}

### User pointer {#window_userptr}

Each window has a user pointer that can be set with @ref
glfwSetWindowUserPointer and queried with @ref glfwGetWindowUserPointer.  This
can be used for any purpose you need and will not be modified by GLFW throughout
the life-time of the window.

The initial value of the pointer is `NULL`.


### Window closing and close flag {#window_close}

When the user attempts to close the window, for example by clicking the close
widget or using a key chord like Alt+F4, the _close flag_ of the window is set.
The window is however not actually destroyed and, unless you watch for this
state change, nothing further happens.

The current state of the close flag is returned by @ref glfwWindowShouldClose
and can be set or cleared directly with @ref glfwSetWindowShouldClose.  A common
pattern is to use the close flag as a main loop condition.

```c
while (!glfwWindowShouldClose(window))
{
    render(window);

    glfwSwapBuffers(window);
    glfwPollEvents();
}
```

If you wish to be notified when the user attempts to close a window, set a close
callback.

```c
glfwSetWindowCloseCallback(window, window_close_callback);
```

The callback function is called directly _after_ the close flag has been set.
It can be used for example to filter close requests and clear the close flag
again unless certain conditions are met.

```c
void window_close_callback(GLFWwindow* window)
{
    if (!time_to_close)
        glfwSetWindowShouldClose(window, GLFW_FALSE);
}
```


### Window size {#window_size}

The size of a window can be changed with @ref glfwSetWindowSize.  For windowed
mode windows, this sets the size, in
[screen coordinates](@ref coordinate_systems) of the _content area_ or _content
area_ of the window.  The window system may impose limits on window size.

```c
glfwSetWindowSize(window, 640, 480);
```

For full screen windows, the specified size becomes the new resolution of the
window's desired video mode.  The video mode most closely matching the new
desired video mode is set immediately.  The window is resized to fit the
resolution of the set video mode.

If you wish to be notified when a window is resized, whether by the user, the
system or your own code, set a size callback.

```c
glfwSetWindowSizeCallback(window, window_size_callback);
```

The callback function receives the new size, in screen coordinates, of the
content area of the window when the window is resized.

```c
void window_size_callback(GLFWwindow* window, int width, int height)
{
}
```

There is also @ref glfwGetWindowSize for directly retrieving the current size of
a window.

```c
int width, height;
glfwGetWindowSize(window, &width, &height);
```

@note Do not pass the window size to `glViewport` or other pixel-based OpenGL
calls.  The window size is in screen coordinates, not pixels.  Use the
[framebuffer size](@ref window_fbsize), which is in pixels, for pixel-based
calls.

The above functions work with the size of the content area, but decorated
windows typically have title bars and window frames around this rectangle.  You
can retrieve the extents of these with @ref glfwGetWindowFrameSize.

```c
int left, top, right, bottom;
glfwGetWindowFrameSize(window, &left, &top, &right, &bottom);
```

The returned values are the distances, in screen coordinates, from the edges of
the content area to the corresponding edges of the full window.  As they are
distances and not coordinates, they are always zero or positive.


### Framebuffer size {#window_fbsize}

While the size of a window is measured in screen coordinates, OpenGL works with
pixels.  The size you pass into `glViewport`, for example, should be in pixels.
On some machines screen coordinates and pixels are the same, but on others they
will not be.  There is a second set of functions to retrieve the size, in
pixels, of the framebuffer of a window.

If you wish to be notified when the framebuffer of a window is resized, whether
by the user or the system, set a size callback.

```c
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
```

The callback function receives the new size of the framebuffer when it is
resized, which can for example be used to update the OpenGL viewport.

```c
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}
```

There is also @ref glfwGetFramebufferSize for directly retrieving the current
size of the framebuffer of a window.

```c
int width, height;
glfwGetFramebufferSize(window, &width, &height);
glViewport(0, 0, width, height);
```

The size of a framebuffer may change independently of the size of a window, for
example if the window is dragged between a regular monitor and a high-DPI one.


### Window content scale {#window_scale}

The content scale for a window can be retrieved with @ref
glfwGetWindowContentScale.

```c
float xscale, yscale;
glfwGetWindowContentScale(window, &xscale, &yscale);
```

The content scale can be thought of as the ratio between the current DPI and the
platform's default DPI.  It is intended to be a scaling factor to apply to the
pixel dimensions of text and other UI elements.  If the dimensions scaled by
this factor looks appropriate on your machine then it should appear at
a reasonable size on other machines with different DPI and scaling settings.

This relies on the DPI and scaling settings on both machines being appropriate.

The content scale may depend on both the monitor resolution and pixel density
and on user settings like DPI or a scaling percentage.  It may be very different
from the raw DPI calculated from the physical size and current resolution.

On systems where each monitors can have its own content scale, the window
content scale will depend on which monitor or monitors the system considers the
window to be "on".

If you wish to be notified when the content scale of a window changes, whether
because of a system setting change or because it was moved to a monitor with
a different scale, set a content scale callback.

```c
glfwSetWindowContentScaleCallback(window, window_content_scale_callback);
```

The callback function receives the new content scale of the window.

```c
void window_content_scale_callback(GLFWwindow* window, float xscale, float yscale)
{
    set_interface_scale(xscale, yscale);
}
```

On platforms where pixels and screen coordinates always map 1:1, the window
will need to be resized to appear the same size when it is moved to a monitor
with a different content scale.  To have this done automatically both when the
window is created and when its content scale later changes, set the @ref
GLFW_SCALE_TO_MONITOR window hint.

On platforms where pixels do not necessarily equal screen coordinates, the
framebuffer will instead need to be sized to provide a full resolution image
for the window.  When the window moves between monitors with different content
scales, the window size will remain the same but the framebuffer size will
change.  This is done automatically by default.  To disable this resizing, set
the @ref GLFW_SCALE_FRAMEBUFFER window hint.

Both of these hints also apply when the window is created.  Every window starts
out with a content scale of one.  A window with one or both of these hints set
will adapt to the appropriate scale in the process of being created, set up and
shown.


### Window size limits {#window_sizelimits}

The minimum and maximum size of the content area of a windowed mode window can
be enforced with @ref glfwSetWindowSizeLimits.  The user may resize the window
to any size and aspect ratio within the specified limits, unless the aspect
ratio is also set.

```c
glfwSetWindowSizeLimits(window, 200, 200, 400, 400);
```

To specify only a minimum size or only a maximum one, set the other pair to
`GLFW_DONT_CARE`.

```c
glfwSetWindowSizeLimits(window, 640, 480, GLFW_DONT_CARE, GLFW_DONT_CARE);
```

To disable size limits for a window, set them all to `GLFW_DONT_CARE`.

The aspect ratio of the content area of a windowed mode window can be enforced
with @ref glfwSetWindowAspectRatio.  The user may resize the window freely
unless size limits are also set, but the size will be constrained to maintain
the aspect ratio.

```c
glfwSetWindowAspectRatio(window, 16, 9);
```

The aspect ratio is specified as a numerator and denominator, corresponding to
the width and height, respectively.  If you want a window to maintain its
current aspect ratio, use its current size as the ratio.

```c
int width, height;
glfwGetWindowSize(window, &width, &height);
glfwSetWindowAspectRatio(window, width, height);
```

To disable the aspect ratio limit for a window, set both terms to
`GLFW_DONT_CARE`.

You can have both size limits and aspect ratio set for a window, but the results
are undefined if they conflict.


### Window position {#window_pos}

By default, the window manager chooses the position of new windowed mode
windows, based on its size and which monitor the user appears to be working on.
This is most often the right choice.  If you need to create a window at
a specific position, you can set the desired position with the @ref
GLFW_POSITION_X and @ref GLFW_POSITION_Y window hints.

```c
glfwWindowHint(GLFW_POSITION_X, 70);
glfwWindowHint(GLFW_POSITION_Y, 83);
```

To restore the previous behavior, set these hints to `GLFW_ANY_POSITION`.

The position of a windowed mode window can be changed with @ref
glfwSetWindowPos.  This moves the window so that the upper-left corner of its
content area has the specified [screen coordinates](@ref coordinate_systems).
The window system may put limitations on window placement.

```c
glfwSetWindowPos(window, 100, 100);
```

If you wish to be notified when a window is moved, whether by the user, the
system or your own code, set a position callback.

```c
glfwSetWindowPosCallback(window, window_pos_callback);
```

The callback function receives the new position, in screen coordinates, of the
upper-left corner of the content area when the window is moved.

```c
void window_pos_callback(GLFWwindow* window, int xpos, int ypos)
{
}
```

There is also @ref glfwGetWindowPos for directly retrieving the current position
of the content area of the window.

```c
int xpos, ypos;
glfwGetWindowPos(window, &xpos, &ypos);
```


### Window title {#window_title}

All GLFW windows have a title, although undecorated or full screen windows may
not display it or only display it in a task bar or similar interface.  You can
set a new UTF-8 encoded window title with @ref glfwSetWindowTitle.

```c
glfwSetWindowTitle(window, "My Window");
```

The specified string is copied before the function returns, so there is no need
to keep it around.

As long as your source file is encoded as UTF-8, you can use any Unicode
characters directly in the source.

```c
glfwSetWindowTitle(window, "ラストエグザイル");
```

If you are using C++11 or C11, you can use a UTF-8 string literal.

```c
glfwSetWindowTitle(window, u8"This is always a UTF-8 string");
```

The current window title can be queried with @ref glfwGetWindowTitle.

```c
const char* title = glfwGetWindowTitle(window);
```

### Window icon {#window_icon}

Decorated windows have icons on some platforms.  You can set this icon by
specifying a list of candidate images with @ref glfwSetWindowIcon.

```c
GLFWimage images[2];
images[0] = load_icon("my_icon.png");
images[1] = load_icon("my_icon_small.png");

glfwSetWindowIcon(window, 2, images);
```

The image data is 32-bit, little-endian, non-premultiplied RGBA, i.e. eight bits
per channel with the red channel first.  The pixels are arranged canonically as
sequential rows, starting from the top-left corner.

To revert to the default window icon, pass in an empty image array.

```c
glfwSetWindowIcon(window, 0, NULL);
```


### Window monitor {#window_monitor}

Full screen windows are associated with a specific monitor.  You can get the
handle for this monitor with @ref glfwGetWindowMonitor.

```c
GLFWmonitor* monitor = glfwGetWindowMonitor(window);
```

This monitor handle is one of those returned by @ref glfwGetMonitors.

For windowed mode windows, this function returns `NULL`.  This is how to tell
full screen windows from windowed mode windows.

You can move windows between monitors or between full screen and windowed mode
with @ref glfwSetWindowMonitor.  When making a window full screen on the same or
on a different monitor, specify the desired monitor, resolution and refresh
rate.  The position arguments are ignored.

```c
const GLFWvidmode* mode = glfwGetVideoMode(monitor);

glfwSetWindowMonitor(window, monitor, 0, 0, mode->width, mode->height, mode->refreshRate);
```

When making the window windowed, specify the desired position and size.  The
refresh rate argument is ignored.

```c
glfwSetWindowMonitor(window, NULL, xpos, ypos, width, height, 0);
```

This restores any previous window settings such as whether it is decorated,
floating, resizable, has size or aspect ratio limits, etc..  To restore a window
that was originally windowed to its original size and position, save these
before making it full screen and then pass them in as above.


### Window iconification {#window_iconify}

Windows can be iconified (i.e. minimized) with @ref glfwIconifyWindow.

```c
glfwIconifyWindow(window);
```

When a full screen window is iconified, the original video mode of its monitor
is restored until the user or application restores the window.

Iconified windows can be restored with @ref glfwRestoreWindow.  This function
also restores windows from maximization.

```c
glfwRestoreWindow(window);
```

When a full screen window is restored, the desired video mode is restored to its
monitor as well.

If you wish to be notified when a window is iconified or restored, whether by
the user, system or your own code, set an iconify callback.

```c
glfwSetWindowIconifyCallback(window, window_iconify_callback);
```

The callback function receives changes in the iconification state of the window.

```c
void window_iconify_callback(GLFWwindow* window, int iconified)
{
    if (iconified)
    {
        // The window was iconified
    }
    else
    {
        // The window was restored
    }
}
```

You can also get the current iconification state with @ref glfwGetWindowAttrib.

```c
int iconified = glfwGetWindowAttrib(window, GLFW_ICONIFIED);
```


### Window maximization {#window_maximize}

Windows can be maximized (i.e. zoomed) with @ref glfwMaximizeWindow.

```c
glfwMaximizeWindow(window);
```

Full screen windows cannot be maximized and passing a full screen window to this
function does nothing.

Maximized windows can be restored with @ref glfwRestoreWindow.  This function
also restores windows from iconification.

```c
glfwRestoreWindow(window);
```

If you wish to be notified when a window is maximized or restored, whether by
the user, system or your own code, set a maximize callback.

```c
glfwSetWindowMaximizeCallback(window, window_maximize_callback);
```

The callback function receives changes in the maximization state of the window.

```c
void window_maximize_callback(GLFWwindow* window, int maximized)
{
    if (maximized)
    {
        // The window was maximized
    }
    else
    {
        // The window was restored
    }
}
```

You can also get the current maximization state with @ref glfwGetWindowAttrib.

```c
int maximized = glfwGetWindowAttrib(window, GLFW_MAXIMIZED);
```

By default, newly created windows are not maximized.  You can change this
behavior by setting the [GLFW_MAXIMIZED](@ref GLFW_MAXIMIZED_hint) window hint
before creating the window.

```c
glfwWindowHint(GLFW_MAXIMIZED, GLFW_TRUE);
```


### Window visibility {#window_hide}

Windowed mode windows can be hidden with @ref glfwHideWindow.

```c
glfwHideWindow(window);
```

This makes the window completely invisible to the user, including removing it
from the task bar, dock or window list.  Full screen windows cannot be hidden
and calling @ref glfwHideWindow on a full screen window does nothing.

Hidden windows can be shown with @ref glfwShowWindow.

```c
glfwShowWindow(window);
```

By default, this function will also set the input focus to that window. Set
the [GLFW_FOCUS_ON_SHOW](@ref GLFW_FOCUS_ON_SHOW_hint) window hint to change
this behavior for all newly created windows, or change the behavior for an
existing window with @ref glfwSetWindowAttrib.

You can also get the current visibility state with @ref glfwGetWindowAttrib.

```c
int visible = glfwGetWindowAttrib(window, GLFW_VISIBLE);
```

By default, newly created windows are visible.  You can change this behavior by
setting the [GLFW_VISIBLE](@ref GLFW_VISIBLE_hint) window hint before creating
the window.

```c
glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE);
```

Windows created hidden are completely invisible to the user until shown.  This
can be useful if you need to set up your window further before showing it, for
example moving it to a specific location.


### Window input focus {#window_focus}

Windows can be given input focus and brought to the front with @ref
glfwFocusWindow.

```c
glfwFocusWindow(window);
```

Keep in mind that it can be very disruptive to the user when a window is forced
to the top.  For a less disruptive way of getting the user's attention, see
[attention requests](@ref window_attention).

If you wish to be notified when a window gains or loses input focus, whether by
the user, system or your own code, set a focus callback.

```c
glfwSetWindowFocusCallback(window, window_focus_callback);
```

The callback function receives changes in the input focus state of the window.

```c
void window_focus_callback(GLFWwindow* window, int focused)
{
    if (focused)
    {
        // The window gained input focus
    }
    else
    {
        // The window lost input focus
    }
}
```

You can also get the current input focus state with @ref glfwGetWindowAttrib.

```c
int focused = glfwGetWindowAttrib(window, GLFW_FOCUSED);
```

By default, newly created windows are given input focus.  You can change this
behavior by setting the [GLFW_FOCUSED](@ref GLFW_FOCUSED_hint) window hint
before creating the window.

```c
glfwWindowHint(GLFW_FOCUSED, GLFW_FALSE);
```


### Window attention request {#window_attention}

If you wish to notify the user of an event without interrupting, you can request
attention with @ref glfwRequestWindowAttention.

```c
glfwRequestWindowAttention(window);
```

The system will highlight the specified window, or on platforms where this is
not supported, the application as a whole.  Once the user has given it
attention, the system will automatically end the request.


### Window damage and refresh {#window_refresh}

If you wish to be notified when the contents of a window is damaged and needs
to be refreshed, set a window refresh callback.

```c
glfwSetWindowRefreshCallback(m_handle, window_refresh_callback);
```

The callback function is called when the contents of the window needs to be
refreshed.

```c
void window_refresh_callback(GLFWwindow* window)
{
    draw_editor_ui(window);
    glfwSwapBuffers(window);
}
```

@note On compositing window systems such as Aero, Compiz or Aqua, where the
window contents are saved off-screen, this callback might only be called when
the window or framebuffer is resized.


### Window transparency {#window_transparency}

GLFW supports two kinds of transparency for windows; framebuffer transparency
and whole window transparency.  A single window may not use both methods.  The
results of doing this are undefined.

Both methods require the platform to support it and not every version of every
platform GLFW supports does this, so there are mechanisms to check whether the
window really is transparent.

Window framebuffers can be made transparent on a per-pixel per-frame basis with
the [GLFW_TRANSPARENT_FRAMEBUFFER](@ref GLFW_TRANSPARENT_FRAMEBUFFER_hint)
window hint.

```c
glfwWindowHint(GLFW_TRANSPARENT_FRAMEBUFFER, GLFW_TRUE);
```

If supported by the system, the window content area will be composited with the
background using the framebuffer per-pixel alpha channel.  This requires desktop
compositing to be enabled on the system.  It does not affect window decorations.

You can check whether the window framebuffer was successfully made transparent
with the
[GLFW_TRANSPARENT_FRAMEBUFFER](@ref GLFW_TRANSPARENT_FRAMEBUFFER_attrib)
window attribute.

```c
if (glfwGetWindowAttrib(window, GLFW_TRANSPARENT_FRAMEBUFFER))
{
    // window framebuffer is currently transparent
}
```

GLFW comes with an example that enabled framebuffer transparency called `gears`.

The opacity of the whole window, including any decorations, can be set with @ref
glfwSetWindowOpacity.

```c
glfwSetWindowOpacity(window, 0.5f);
```

The opacity (or alpha) value is a positive finite number between zero and one,
where 0 (zero) is fully transparent and 1 (one) is fully opaque.  The initial
opacity value for newly created windows is 1.

The current opacity of a window can be queried with @ref glfwGetWindowOpacity.

```c
float opacity = glfwGetWindowOpacity(window);
```

If the system does not support whole window transparency, this function always
returns one.

GLFW comes with a test program that lets you control whole window transparency
at run-time called `window`.

If you want to use either of these transparency methods to display a temporary
overlay like for example a notification, the @ref GLFW_FLOATING and @ref
GLFW_MOUSE_PASSTHROUGH window hints and attributes may be useful.


### Window attributes {#window_attribs}

Windows have a number of attributes that can be returned using @ref
glfwGetWindowAttrib.  Some reflect state that may change as a result of user
interaction, (e.g. whether it has input focus), while others reflect inherent
properties of the window (e.g. what kind of border it has).  Some are related to
the window and others to its OpenGL or OpenGL ES context.

```c
if (glfwGetWindowAttrib(window, GLFW_FOCUSED))
{
    // window has input focus
}
```

The [GLFW_DECORATED](@ref GLFW_DECORATED_attrib),
[GLFW_RESIZABLE](@ref GLFW_RESIZABLE_attrib),
[GLFW_FLOATING](@ref GLFW_FLOATING_attrib),
[GLFW_AUTO_ICONIFY](@ref GLFW_AUTO_ICONIFY_attrib) and
[GLFW_FOCUS_ON_SHOW](@ref GLFW_FOCUS_ON_SHOW_attrib) window attributes can be
changed with @ref glfwSetWindowAttrib.

```c
glfwSetWindowAttrib(window, GLFW_RESIZABLE, GLFW_FALSE);
```



#### Window related attributes {#window_attribs_wnd}

@anchor GLFW_FOCUSED_attrib
__GLFW_FOCUSED__ indicates whether the specified window has input focus.  See
@ref window_focus for details.

@anchor GLFW_ICONIFIED_attrib
__GLFW_ICONIFIED__ indicates whether the specified window is iconified.
See @ref window_iconify for details.

@anchor GLFW_MAXIMIZED_attrib
__GLFW_MAXIMIZED__ indicates whether the specified window is maximized.  See
@ref window_maximize for details.

@anchor GLFW_HOVERED_attrib
__GLFW_HOVERED__ indicates whether the cursor is currently directly over the
content area of the window, with no other windows between.  See @ref
cursor_enter for details.

@anchor GLFW_VISIBLE_attrib
__GLFW_VISIBLE__ indicates whether the specified window is visible.  See @ref
window_hide for details.

@anchor GLFW_RESIZABLE_attrib
__GLFW_RESIZABLE__ indicates whether the specified window is resizable _by the
user_.  This can be set before creation with the
[GLFW_RESIZABLE](@ref GLFW_RESIZABLE_hint) window hint or after with @ref
glfwSetWindowAttrib.

@anchor GLFW_DECORATED_attrib
__GLFW_DECORATED__ indicates whether the specified window has decorations such
as a border, a close widget, etc.  This can be set before creation with the
[GLFW_DECORATED](@ref GLFW_DECORATED_hint) window hint or after with @ref
glfwSetWindowAttrib.

@anchor GLFW_AUTO_ICONIFY_attrib
__GLFW_AUTO_ICONIFY__ indicates whether the specified full screen window is
iconified on focus loss, a close widget, etc.  This can be set before creation
with the [GLFW_AUTO_ICONIFY](@ref GLFW_AUTO_ICONIFY_hint) window hint or after
with @ref glfwSetWindowAttrib.

@anchor GLFW_FLOATING_attrib
__GLFW_FLOATING__ indicates whether the specified window is floating, also
called topmost or always-on-top.  This can be set before creation with the
[GLFW_FLOATING](@ref GLFW_FLOATING_hint) window hint or after with @ref
glfwSetWindowAttrib.

@anchor GLFW_TRANSPARENT_FRAMEBUFFER_attrib
__GLFW_TRANSPARENT_FRAMEBUFFER__ indicates whether the specified window has
a transparent framebuffer, i.e. the window contents is composited with the
background using the window framebuffer alpha channel.  See @ref
window_transparency for details.

@anchor GLFW_FOCUS_ON_SHOW_attrib
__GLFW_FOCUS_ON_SHOW__ specifies whether the window will be given input
focus when @ref glfwShowWindow is called. This can be set before creation
with the [GLFW_FOCUS_ON_SHOW](@ref GLFW_FOCUS_ON_SHOW_hint) window hint or
after with @ref glfwSetWindowAttrib.

@anchor GLFW_MOUSE_PASSTHROUGH_attrib
__GLFW_MOUSE_PASSTHROUGH__ specifies whether the window is transparent to mouse
input, letting any mouse events pass through to whatever window is behind it.
This can be set before creation with the
[GLFW_MOUSE_PASSTHROUGH](@ref GLFW_MOUSE_PASSTHROUGH_hint) window hint or after
with @ref glfwSetWindowAttrib.  This is only supported for undecorated windows.
Decorated windows with this enabled will behave differently between platforms.


#### Context related attributes {#window_attribs_ctx}

@anchor GLFW_CLIENT_API_attrib
__GLFW_CLIENT_API__ indicates the client API provided by the window's context;
either `GLFW_OPENGL_API`, `GLFW_OPENGL_ES_API` or `GLFW_NO_API`.

@anchor GLFW_CONTEXT_CREATION_API_attrib
__GLFW_CONTEXT_CREATION_API__ indicates the context creation API used to create
the window's context; either `GLFW_NATIVE_CONTEXT_API`, `GLFW_EGL_CONTEXT_API`
or `GLFW_OSMESA_CONTEXT_API`.

@anchor GLFW_CONTEXT_VERSION_MAJOR_attrib
@anchor GLFW_CONTEXT_VERSION_MINOR_attrib
@anchor GLFW_CONTEXT_REVISION_attrib
__GLFW_CONTEXT_VERSION_MAJOR__, __GLFW_CONTEXT_VERSION_MINOR__ and
__GLFW_CONTEXT_REVISION__ indicate the client API version of the window's
context.

@note Do not confuse these attributes with `GLFW_VERSION_MAJOR`,
`GLFW_VERSION_MINOR` and `GLFW_VERSION_REVISION` which provide the API version
of the GLFW header.

@anchor GLFW_OPENGL_FORWARD_COMPAT_attrib
__GLFW_OPENGL_FORWARD_COMPAT__ is `GLFW_TRUE` if the window's context is an
OpenGL forward-compatible one, or `GLFW_FALSE` otherwise.

@anchor GLFW_CONTEXT_DEBUG_attrib
@anchor GLFW_OPENGL_DEBUG_CONTEXT_attrib
__GLFW_CONTEXT_DEBUG__ is `GLFW_TRUE` if the window's context is in debug
mode, or `GLFW_FALSE` otherwise.

This is the new name, introduced in GLFW 3.4.  The older
`GLFW_OPENGL_DEBUG_CONTEXT` name is also available for compatibility.

@anchor GLFW_OPENGL_PROFILE_attrib
__GLFW_OPENGL_PROFILE__ indicates the OpenGL profile used by the context.  This
is `GLFW_OPENGL_CORE_PROFILE` or `GLFW_OPENGL_COMPAT_PROFILE` if the context
uses a known profile, or `GLFW_OPENGL_ANY_PROFILE` if the OpenGL profile is
unknown or the context is an OpenGL ES context.  Note that the returned profile
may not match the profile bits of the context flags, as GLFW will try other
means of detecting the profile when no bits are set.

@anchor GLFW_CONTEXT_RELEASE_BEHAVIOR_attrib
__GLFW_CONTEXT_RELEASE_BEHAVIOR__ indicates the release used by the context.
Possible values are one of `GLFW_ANY_RELEASE_BEHAVIOR`,
`GLFW_RELEASE_BEHAVIOR_FLUSH` or `GLFW_RELEASE_BEHAVIOR_NONE`.  If the
behavior is `GLFW_ANY_RELEASE_BEHAVIOR`, the default behavior of the context
creation API will be used.  If the behavior is `GLFW_RELEASE_BEHAVIOR_FLUSH`,
the pipeline will be flushed whenever the context is released from being the
current one.  If the behavior is `GLFW_RELEASE_BEHAVIOR_NONE`, the pipeline will
not be flushed on release.

@anchor GLFW_CONTEXT_NO_ERROR_attrib
__GLFW_CONTEXT_NO_ERROR__ indicates whether errors are generated by the context.
Possible values are `GLFW_TRUE` and `GLFW_FALSE`.  If enabled, situations that
would have generated errors instead cause undefined behavior.

@anchor GLFW_CONTEXT_ROBUSTNESS_attrib
__GLFW_CONTEXT_ROBUSTNESS__ indicates the robustness strategy used by the
context.  This is `GLFW_LOSE_CONTEXT_ON_RESET` or `GLFW_NO_RESET_NOTIFICATION`
if the window's context supports robustness, or `GLFW_NO_ROBUSTNESS` otherwise.


#### Framebuffer related attributes {#window_attribs_fb}

GLFW does not expose most attributes of the default framebuffer (i.e. the
framebuffer attached to the window) as these can be queried directly with either
OpenGL, OpenGL ES or Vulkan.  The one exception is
[GLFW_DOUBLEBUFFER](@ref GLFW_DOUBLEBUFFER_attrib), as this is not provided by
OpenGL ES.

If you are using version 3.0 or later of OpenGL or OpenGL ES, the
`glGetFramebufferAttachmentParameteriv` function can be used to retrieve the
number of bits for the red, green, blue, alpha, depth and stencil buffer
channels.  Otherwise, the `glGetIntegerv` function can be used.

The number of MSAA samples are always retrieved with `glGetIntegerv`.  For
contexts supporting framebuffer objects, the number of samples of the currently
bound framebuffer is returned.

Attribute    | glGetIntegerv     | glGetFramebufferAttachmentParameteriv
------------ | ----------------- | -------------------------------------
Red bits     | `GL_RED_BITS`     | `GL_FRAMEBUFFER_ATTACHMENT_RED_SIZE`
Green bits   | `GL_GREEN_BITS`   | `GL_FRAMEBUFFER_ATTACHMENT_GREEN_SIZE`
Blue bits    | `GL_BLUE_BITS`    | `GL_FRAMEBUFFER_ATTACHMENT_BLUE_SIZE`
Alpha bits   | `GL_ALPHA_BITS`   | `GL_FRAMEBUFFER_ATTACHMENT_ALPHA_SIZE`
Depth bits   | `GL_DEPTH_BITS`   | `GL_FRAMEBUFFER_ATTACHMENT_DEPTH_SIZE`
Stencil bits | `GL_STENCIL_BITS` | `GL_FRAMEBUFFER_ATTACHMENT_STENCIL_SIZE`
MSAA samples | `GL_SAMPLES`      | _Not provided by this function_

When calling `glGetFramebufferAttachmentParameteriv`, the red, green, blue and
alpha sizes are queried from the `GL_BACK_LEFT`, while the depth and stencil
sizes are queried from the `GL_DEPTH` and `GL_STENCIL` attachments,
respectively.

@anchor GLFW_DOUBLEBUFFER_attrib
__GLFW_DOUBLEBUFFER__ indicates whether the specified window is double-buffered
when rendering with OpenGL or OpenGL ES.  This can be set before creation with
the [GLFW_DOUBLEBUFFER](@ref GLFW_DOUBLEBUFFER_hint) window hint.


## Buffer swapping {#buffer_swap}

GLFW windows are by default double buffered.  That means that you have two
rendering buffers; a front buffer and a back buffer.  The front buffer is
the one being displayed and the back buffer the one you render to.

When the entire frame has been rendered, it is time to swap the back and the
front buffers in order to display what has been rendered and begin rendering
a new frame.  This is done with @ref glfwSwapBuffers.

```c
glfwSwapBuffers(window);
```

Sometimes it can be useful to select when the buffer swap will occur.  With the
function @ref glfwSwapInterval it is possible to select the minimum number of
monitor refreshes the driver should wait from the time @ref glfwSwapBuffers was
called before swapping the buffers:

```c
glfwSwapInterval(1);
```

If the interval is zero, the swap will take place immediately when @ref
glfwSwapBuffers is called without waiting for a refresh.  Otherwise at least
interval retraces will pass between each buffer swap.  Using a swap interval of
zero can be useful for benchmarking purposes, when it is not desirable to
measure the time it takes to wait for the vertical retrace.  However, a swap
interval of one lets you avoid tearing.

Note that this may not work on all machines, as some drivers have
user-controlled settings that override any swap interval the application
requests.

A context that supports either the `WGL_EXT_swap_control_tear` or the
`GLX_EXT_swap_control_tear` extension also accepts _negative_ swap intervals,
which allows the driver to swap immediately even if a frame arrives a little bit
late.  This trades the risk of visible tears for greater framerate stability.
You can check for these extensions with @ref glfwExtensionSupported.