Input guide

Table of Contents

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

GLFW provides many kinds of input. While some can only be polled, like time, or only received via callbacks, like scrolling, many provide both callbacks and polling. Callbacks are more work to use than polling but is less CPU intensive and guarantees that you do not miss state changes.

All input callbacks receive a window handle. By using the window user pointer, you can access non-global structures or objects from your callbacks.

To get a better feel for how the various events callbacks behave, run the events test program. It register every callback supported by GLFW and prints out all arguments provided for every event, along with time and sequence information.

Event processing

GLFW needs to poll the window system for events both to provide input to the application and to prove to the window system that the application hasn't locked up. Event processing is normally done each frame after buffer swapping. Even when you have no windows, event polling needs to be done in order to receive monitor and joystick connection events.

There are three functions for processing pending events. glfwPollEvents, processes only those events that have already been received and then returns immediately.

This is the best choice when rendering continuously, like most games do.

If you only need to update the contents of the window when you receive new input, glfwWaitEvents is a better choice.

It puts the thread to sleep until at least one event has been received and then processes all received events. This saves a great deal of CPU cycles and is useful for, for example, editing tools. There must be at least one GLFW window for this function to sleep.

If you want to wait for events but have UI elements or other tasks that need periodic updates, glfwWaitEventsTimeout lets you specify a timeout.

It puts the thread to sleep until at least one event has been received, or until the specified number of seconds have elapsed. It then processes any received events.

If the main thread is sleeping in glfwWaitEvents, you can wake it from another thread by posting an empty event to the event queue with glfwPostEmptyEvent.

Do not assume that callbacks will only be called in response to the above functions. While it is necessary to process events in one or more of the ways above, window systems that require GLFW to register callbacks of its own can pass events to GLFW in response to many window system function calls. GLFW will pass those events on to the application callbacks before returning.

For example, on Windows the system function that glfwSetWindowSize is implemented with will send window size events directly to the event callback that every window has and that GLFW implements for its windows. If you have set a window size callback GLFW will call it in turn with the new size before everything returns back out of the glfwSetWindowSize call.

Keyboard input

GLFW divides keyboard input into two categories; key events and character events. Key events relate to actual physical keyboard keys, whereas character events relate to the Unicode code points generated by pressing some of them.

Keys and characters do not map 1:1. A single key press may produce several characters, and a single character may require several keys to produce. This may not be the case on your machine, but your users are likely not all using the same keyboard layout, input method or even operating system as you.

Key input

If you wish to be notified when a physical key is pressed or released or when it repeats, set a key callback.

glfwSetKeyCallback(window, key_callback);

The callback function receives the keyboard key, platform-specific scancode, key action and modifier bits.

void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if (key == GLFW_KEY_E && action == GLFW_PRESS)
activate_airship();
}

The action is one of GLFW_PRESS, GLFW_REPEAT or GLFW_RELEASE. The key will be GLFW_KEY_UNKNOWN if GLFW lacks a key token for it, for example E-mail and Play keys.

The scancode is unique for every key, regardless of whether it has a key token. Scancodes are platform-specific but consistent over time, so keys will have different scancodes depending on the platform but they are safe to save to disk. You can query the scancode for any named key on the current platform with glfwGetKeyScancode.

const int scancode = glfwGetKeyScancode(GLFW_KEY_X);
set_key_mapping(scancode, swap_weapons);

The last reported state for every named key is also saved in per-window state arrays that can be polled with glfwGetKey.

int state = glfwGetKey(window, GLFW_KEY_E);
if (state == GLFW_PRESS)
{
activate_airship();
}

The returned state is one of GLFW_PRESS or GLFW_RELEASE.

This function only returns cached key event state. It does not poll the system for the current physical state of the key.

Whenever you poll state, you risk missing the state change you are looking for. If a pressed key is released again before you poll its state, you will have missed the key press. The recommended solution for this is to use a key callback, but there is also the GLFW_STICKY_KEYS input mode.

When sticky keys mode is enabled, the pollable state of a key will remain GLFW_PRESS until the state of that key is polled with glfwGetKey. Once it has been polled, if a key release event had been processed in the meantime, the state will reset to GLFW_RELEASE, otherwise it will remain GLFW_PRESS.

The GLFW_KEY_LAST constant holds the highest value of any named key.

Text input

GLFW supports text input in the form of a stream of Unicode code points, as produced by the operating system text input system. Unlike key input, text input obeys keyboard layouts and modifier keys and supports composing characters using dead keys. Once received, you can encode the code points into UTF-8 or any other encoding you prefer.

Because an unsigned int is 32 bits long on all platforms supported by GLFW, you can treat the code point argument as native endian UTF-32.

There are two callbacks for receiving Unicode code points. If you wish to offer regular text input, set a character callback.

glfwSetCharCallback(window, character_callback);

The callback function receives Unicode code points for key events that would have led to regular text input and generally behaves as a standard text field on that platform.

void character_callback(GLFWwindow* window, unsigned int codepoint)
{
}

If you also wish to receive those Unicode code points generated with modifier key combinations that a plain text field would ignore, or want to know exactly what modifier keys were used, set a character with modifiers callback.

glfwSetCharModsCallback(window, charmods_callback);

The callback function receives Unicode code points and modifier bits.

void charmods_callback(GLFWwindow* window, unsigned int codepoint, int mods)
{
}

Key names

If you wish to refer to keys by name, you can query the keyboard layout dependent name of printable keys with glfwGetKeyName.

const char* key_name = glfwGetKeyName(GLFW_KEY_W, 0);
show_tutorial_hint("Press %s to move forward", key_name);

This function can handle both keys and scancodes. If the specified key is GLFW_KEY_UNKNOWN then the scancode is used, otherwise it is ignored. This matches the behavior of the key callback, meaning the callback arguments can always be passed unmodified to this function.

Mouse input

Mouse input comes in many forms, including cursor motion, button presses and scrolling offsets. The cursor appearance can also be changed, either to a custom image or a standard cursor shape from the system theme.

Cursor position

If you wish to be notified when the cursor moves over the window, set a cursor position callback.

glfwSetCursorPosCallback(window, cursor_pos_callback);

The callback functions receives the cursor position, measured in screen coordinates but relative to the top-left corner of the window client area. On platforms that provide it, the full sub-pixel cursor position is passed on.

static void cursor_position_callback(GLFWwindow* window, double xpos, double ypos)
{
}

The cursor position is also saved per-window and can be polled with glfwGetCursorPos.

double xpos, ypos;
glfwGetCursorPos(window, &xpos, &ypos);

Cursor mode

The GLFW_CURSOR input mode provides several cursor modes for special forms of mouse motion input. By default, the cursor mode is GLFW_CURSOR_NORMAL, meaning the regular arrow cursor (or another cursor set with glfwSetCursor) is used and cursor motion is not limited.

If you wish to implement mouse motion based camera controls or other input schemes that require unlimited mouse movement, set the cursor mode to GLFW_CURSOR_DISABLED.

This will hide the cursor and lock it to the specified window. GLFW will then take care of all the details of cursor re-centering and offset calculation and providing the application with a virtual cursor position. This virtual position is provided normally via both the cursor position callback and through polling.

Note
You should not implement your own version of this functionality using other features of GLFW. It is not supported and will not work as robustly as GLFW_CURSOR_DISABLED.

If you only wish the cursor to become hidden when it is over a window but still want it to behave normally, set the cursor mode to GLFW_CURSOR_HIDDEN.

This mode puts no limit on the motion of the cursor.

To exit out of either of these special modes, restore the GLFW_CURSOR_NORMAL cursor mode.

Cursor objects

GLFW supports creating both custom and system theme cursor images, encapsulated as GLFWcursor objects. They are created with glfwCreateCursor or glfwCreateStandardCursor and destroyed with glfwDestroyCursor, or glfwTerminate, if any remain.

Custom cursor creation

A custom cursor is created with glfwCreateCursor, which returns a handle to the created cursor object. For example, this creates a 16x16 white square cursor with the hot-spot in the upper-left corner:

unsigned char pixels[16 * 16 * 4];
memset(pixels, 0xff, sizeof(pixels));
GLFWimage image;
image.width = 16;
image.height = 16;
image.pixels = pixels;
GLFWcursor* cursor = glfwCreateCursor(&image, 0, 0);

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

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.

Standard cursor creation

A cursor with a standard shape from the current system cursor theme can be can be created with glfwCreateStandardCursor.

These cursor objects behave in the exact same way as those created with glfwCreateCursor except that the system cursor theme provides the actual image.

Cursor destruction

When a cursor is no longer needed, destroy it with glfwDestroyCursor.

Cursor destruction always succeeds. If the cursor is current for any window, that window will revert to the default cursor. This does not affect the cursor mode. All remaining cursors remaining are destroyed when glfwTerminate is called.

Cursor setting

A cursor can be set as current for a window with glfwSetCursor.

glfwSetCursor(window, cursor);

Once set, the cursor image will be used as long as the system cursor is over the client area of the window and the cursor mode is set to GLFW_CURSOR_NORMAL.

A single cursor may be set for any number of windows.

To revert to the default cursor, set the cursor of that window to NULL.

glfwSetCursor(window, NULL);

When a cursor is destroyed, any window that has it set will revert to the default cursor. This does not affect the cursor mode.

Cursor enter/leave events

If you wish to be notified when the cursor enters or leaves the client area of a window, set a cursor enter/leave callback.

glfwSetCursorEnterCallback(window, cursor_enter_callback);

The callback function receives the new classification of the cursor.

void cursor_enter_callback(GLFWwindow* window, int entered)
{
if (entered)
{
// The cursor entered the client area of the window
}
else
{
// The cursor left the client area of the window
}
}

Mouse button input

If you wish to be notified when a mouse button is pressed or released, set a mouse button callback.

glfwSetMouseButtonCallback(window, mouse_button_callback);

The callback function receives the mouse button, button action and modifier bits.

void mouse_button_callback(GLFWwindow* window, int button, int action, int mods)
{
if (button == GLFW_MOUSE_BUTTON_RIGHT && action == GLFW_PRESS)
popup_menu();
}

The action is one of GLFW_PRESS or GLFW_RELEASE.

Mouse button states for named buttons are also saved in per-window state arrays that can be polled with glfwGetMouseButton.

if (state == GLFW_PRESS)
{
upgrade_cow();
}

The returned state is one of GLFW_PRESS or GLFW_RELEASE.

This function only returns cached mouse button event state. It does not poll the system for the current state of the mouse button.

Whenever you poll state, you risk missing the state change you are looking for. If a pressed mouse button is released again before you poll its state, you will have missed the button press. The recommended solution for this is to use a mouse button callback, but there is also the GLFW_STICKY_MOUSE_BUTTONS input mode.

When sticky mouse buttons mode is enabled, the pollable state of a mouse button will remain GLFW_PRESS until the state of that button is polled with glfwGetMouseButton. Once it has been polled, if a mouse button release event had been processed in the meantime, the state will reset to GLFW_RELEASE, otherwise it will remain GLFW_PRESS.

The GLFW_MOUSE_BUTTON_LAST constant holds the highest value of any named button.

Scroll input

If you wish to be notified when the user scrolls, whether with a mouse wheel or touchpad gesture, set a scroll callback.

glfwSetScrollCallback(window, scroll_callback);

The callback function receives two-dimensional scroll offsets.

void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
{
}

A normal mouse wheel, being vertical, provides offsets along the Y-axis.

Joystick input

The joystick functions expose connected joysticks and controllers, with both referred to as joysticks. It supports up to sixteen joysticks, ranging from GLFW_JOYSTICK_1, GLFW_JOYSTICK_2 up to and including GLFW_JOYSTICK_16 or GLFW_JOYSTICK_LAST. You can test whether a joystick is present with glfwJoystickPresent.

When GLFW is initialized, detected joysticks are added to to the beginning of the array. Once a joystick is detected, it keeps its assigned ID until it is disconnected or the library is terminated, so as joysticks are connected and disconnected, there may appear gaps in the IDs.

Joystick axis, button and hat state is updated when polled and does not require a window to be created or events to be processed. However, if you want joystick connection and disconnection events reliably delivered to the joystick callback then you must process events.

To see all the properties of all connected joysticks in real-time, run the joysticks test program.

Joystick axis states

The positions of all axes of a joystick are returned by glfwGetJoystickAxes. See the reference documentation for the lifetime of the returned array.

int count;
const float* axes = glfwGetJoystickAxes(GLFW_JOYSTICK_5, &count);

Each element in the returned array is a value between -1.0 and 1.0.

Joystick button states

The states of all buttons of a joystick are returned by glfwGetJoystickButtons. See the reference documentation for the lifetime of the returned array.

int count;
const unsigned char* buttons = glfwGetJoystickButtons(GLFW_JOYSTICK_3, &count);

Each element in the returned array is either GLFW_PRESS or GLFW_RELEASE.

For backward compatibility with earlier versions that did not have glfwGetJoystickHats, the button array by default also includes all hats. See the reference documentation for glfwGetJoystickButtons for details.

Joystick hat states

The states of all hats are returned by glfwGetJoystickHats. See the reference documentation for the lifetime of the returned array.

int count;
const unsigned char* hats = glfwGetJoystickHats(GLFW_JOYSTICK_7, &count);

Each element in the returned array is one of the following:

Name Value
GLFW_HAT_CENTERED 0
GLFW_HAT_UP 1
GLFW_HAT_RIGHT 2
GLFW_HAT_DOWN 4
GLFW_HAT_LEFT 8
GLFW_HAT_RIGHT_UP GLFW_HAT_RIGHT | GLFW_HAT_UP
GLFW_HAT_RIGHT_DOWN GLFW_HAT_RIGHT | GLFW_HAT_DOWN
GLFW_HAT_LEFT_UP GLFW_HAT_LEFT | GLFW_HAT_UP
GLFW_HAT_LEFT_DOWN GLFW_HAT_LEFT | GLFW_HAT_DOWN

The diagonal directions are bitwise combinations of the primary (up, right, down and left) directions and you can test for these individually by ANDing it with the corresponding direction.

if (hats[2] & GLFW_HAT_RIGHT)
{
// State of hat 2 could be right-up, right or right-down
}

For backward compatibility with earlier versions that did not have glfwGetJoystickHats, all hats are by default also included in the button array. See the reference documentation for glfwGetJoystickButtons for details.

Joystick name

The human-readable, UTF-8 encoded name of a joystick is returned by glfwGetJoystickName. See the reference documentation for the lifetime of the returned string.

Joystick names are not guaranteed to be unique. Two joysticks of the same model and make may have the same name. Only the joystick token is guaranteed to be unique, and only until that joystick is disconnected.

Joystick configuration changes

If you wish to be notified when a joystick is connected or disconnected, set a joystick callback.

glfwSetJoystickCallback(joystick_callback);

The callback function receives the ID of the joystick that has been connected and disconnected and the event that occurred.

void joystick_callback(int jid, int event)
{
if (event == GLFW_CONNECTED)
{
// The joystick was connected
}
else if (event == GLFW_DISCONNECTED)
{
// The joystick was disconnected
}
}

For joystick connection and disconnection events to be delivered on all platforms, you need to call one of the event processing functions. Joystick disconnection may also be detected and the callback called by joystick functions. The function will then return whatever it returns for a disconnected joystick.

Gamepad input

The joystick functions provide unlabeled axes, buttons and hats, with no indication of where they are located on the device. Their order may also vary between platforms even with the same device.

To solve this problem the SDL community crowdsourced the SDL_GameControllerDB project, a database of mappings from many different devices to an Xbox-like gamepad.

GLFW supports this mapping format and contains a copy of the mappings available at the time of release. See Gamepad mappings for how to update this at runtime. Mappings will be assigned to joysticks automatically any time a joystick is connected or the mappings are updated.

You can check whether a joystick is both present and has a gamepad mapping with glfwJoystickIsGamepad.

{
// Use as gamepad
}

If you are only interested in gamepad input you can use this function instead of glfwJoystickPresent.

You can query the human-readable name provided by the gamepad mapping with glfwGetGamepadName. This may or may not be the same as the joystick name.

const char* name = glfwGetGamepadName(GLFW_JOYSTICK_7);

To retrieve the gamepad state of a joystick, call glfwGetGamepadState.

{
{
input_jump();
}
}

The GLFWgamepadstate struct has two arrays; one for button states and one for axis states. The values for each button and axis are the same as for the glfwGetJoystickButtons and glfwGetJoystickAxes functions, i.e. GLFW_PRESS or GLFW_RELEASE for buttons and -1.0 to 1.0 inclusive for axes.

The sizes of the arrays and the positions within each array are fixed.

The button indices are GLFW_GAMEPAD_BUTTON_A, GLFW_GAMEPAD_BUTTON_B, GLFW_GAMEPAD_BUTTON_X, GLFW_GAMEPAD_BUTTON_Y, GLFW_GAMEPAD_BUTTON_LEFT_BUMPER, GLFW_GAMEPAD_BUTTON_RIGHT_BUMPER, GLFW_GAMEPAD_BUTTON_BACK, GLFW_GAMEPAD_BUTTON_START, GLFW_GAMEPAD_BUTTON_GUIDE, GLFW_GAMEPAD_BUTTON_LEFT_THUMB, GLFW_GAMEPAD_BUTTON_RIGHT_THUMB, GLFW_GAMEPAD_BUTTON_DPAD_UP, GLFW_GAMEPAD_BUTTON_DPAD_RIGHT, GLFW_GAMEPAD_BUTTON_DPAD_DOWN and GLFW_GAMEPAD_BUTTON_DPAD_LEFT.

For those who prefer, there are also the GLFW_GAMEPAD_BUTTON_CROSS, GLFW_GAMEPAD_BUTTON_CIRCLE, GLFW_GAMEPAD_BUTTON_SQUARE and GLFW_GAMEPAD_BUTTON_TRIANGLE aliases for the A, B, X and Y button indices.

The axis indices are GLFW_GAMEPAD_AXIS_LEFT_X, GLFW_GAMEPAD_AXIS_LEFT_Y, GLFW_GAMEPAD_AXIS_RIGHT_X, GLFW_GAMEPAD_AXIS_RIGHT_Y, GLFW_GAMEPAD_AXIS_LEFT_TRIGGER and GLFW_GAMEPAD_AXIS_RIGHT_TRIGGER.

The GLFW_GAMEPAD_BUTTON_LAST and GLFW_GAMEPAD_AXIS_LAST constants equal the largest available index for each array.

Gamepad mappings

GLFW contains a copy of the mappings available in SDL_GameControllerDB at the time of release. Newer ones can be added at runtime with glfwUpdateGamepadMappings.

const char* mappings = load_file_contents("gamecontrollerdb.txt");

This function supports everything from single lines up to and including the unmodified contents of the whole gamecontrollerdb.txt file.

Below is a description of the mapping format. Please keep in mind that this description is not authoritative. The format is defined by the SDL and SDL_GameControllerDB projects and their documentation and code takes precedence.

Each mapping is a single line of comma-separated values describing the GUID, name and layout of the gamepad. Lines that do not begin with a hexadecimal digit are ignored.

The first value is always the gamepad GUID, a 32 character long hexadecimal string that typically identifies its make, model, revision and the type of connection to the computer. When this information is not available, the GUID is generated using the gamepad name. GLFW uses the SDL 2.0.5+ GUID format but can convert from the older formats.

The second value is always the human-readable name of the gamepad.

All subsequent values are in the form <field>:<value> and describe the layout of the mapping. These fields may not all be present and may occur in any order.

The button fields are a, b, c, d, back, start, guide, dpup, dpright, dpdown, dpleft, leftshoulder, rightshoulder, leftstick and rightstick.

The axis fields are leftx, lefty, rightx, righty, lefttrigger and righttrigger.

The value of an axis or button field can be a joystick button, a joystick axis, a hat bitmask or empty. Joystick buttons are specified as bN, for example b2 for the third button. Joystick axes are specified as aN, for example a7 for the eighth button. Joystick hat bit masks are specified as hN.N, for example h0.8 for left on the first hat. More than one bit may be set in the mask.

The hat bit mask match the hat states in the joystick functions.

There is also the special platform field that specifies which platform the mapping is valid for. Possible values are Windows, Mac OS X and Linux.

Below is an example of what a gamepad mapping might look like. It is the one built into GLFW for Xbox controllers accessed via the XInput API on Windows. This example has been broken into several lines to fit on the page, but real gamepad mappings must be a single line.

78696e70757401000000000000000000,XInput Gamepad (GLFW),platform:Windows,a:b0,
b:b1,x:b2,y:b3,leftshoulder:b4,rightshoulder:b5,back:b6,start:b7,leftstick:b8,
rightstick:b9,leftx:a0,lefty:a1,rightx:a2,righty:a3,lefttrigger:a4,
righttrigger:a5,dpup:h0.1,dpright:h0.2,dpdown:h0.4,dpleft:h0.8,
Note
GLFW does not yet support the range and inversion modifiers +, - and ~ that were recently added to SDL.

Time input

GLFW provides high-resolution time input, in seconds, with glfwGetTime.

double seconds = glfwGetTime();

It returns the number of seconds since the timer was started when the library was initialized with glfwInit. The platform-specific time sources used usually have micro- or nanosecond resolution.

You can modify the reference time with glfwSetTime.

This sets the timer to the specified time, in seconds.

You can also access the raw timer value, measured in 1 / frequency seconds, with glfwGetTimerValue.

uint64_t value = glfwGetTimerValue();

The frequency of the raw timer varies depending on what time sources are available on the machine. You can query its frequency, in Hz, with glfwGetTimerFrequency.

uint64_t freqency = glfwGetTimerFrequency();

Clipboard input and output

If the system clipboard contains a UTF-8 encoded string or if it can be converted to one, you can retrieve it with glfwGetClipboardString. See the reference documentation for the lifetime of the returned string.

const char* text = glfwGetClipboardString(window);
if (text)
{
insert_text(text);
}

If the clipboard is empty or if its contents could not be converted, NULL is returned.

The contents of the system clipboard can be set to a UTF-8 encoded string with glfwSetClipboardString.

glfwSetClipboardString(window, "A string with words in it");

The clipboard functions take a window handle argument because some window systems require a window to communicate with the system clipboard. Any valid window may be used.

Path drop input

If you wish to receive the paths of files and/or directories dropped on a window, set a file drop callback.

glfwSetDropCallback(window, drop_callback);

The callback function receives an array of paths encoded as UTF-8.

void drop_callback(GLFWwindow* window, int count, const char** paths)
{
int i;
for (i = 0; i < count; i++)
handle_dropped_file(paths[i]);
}

The path array and its strings are only valid until the file drop callback returns, as they may have been generated specifically for that event. You need to make a deep copy of the array if you want to keep the paths.