Keyboard input

pyglet provides multiple types of keyboard input abstraction:

1. Cross-platform key press/release events suitable for game controls

2. Unicode text entry with automatic locale and platform handling

3. Cross-platform detection of common text editing actions

All of them have the following restrictions:

1. There must be at least one pyglet Window instance which can hold keyboard focus

2. Windows created with the following styles cannot hold keyboard focus:

   • WINDOW_STYLE_BORDERLESS

   • WINDOW_STYLE_TOOL

If your project’s requirements fall outside these restrictions, you should consider alternatives. Examples include:

• Python’s built-in input() function

• The Textual terminal UI framework

Keyboard Focus Conventions

Keyboard focus is where the user’s keyboard input is sent.

Desktop operating systems often follow these conventions:

1. Only one window can have focus

2. Clicking a window gives it focus

3. The window with focus is displayed above all others

4. The window with focus has a distinct title bar style

5. Windows can have focus taken away

6. Windows can request focus

However, the items above are not guaranteed to be true.

For example, pyglet allows you to request focus from the OS by calling Window.activate. However, the OS may not support the feature. Even if it does support it, the OS may not only refuse, but do so without notifying the user focus was requested.

Deviations from the conventions can occur for any of the following reasons:

Cause	Example(s)
Modal dialogs	Permission requests and error notifications
User settings	Window focus is set to follow the mouse
Platform quirks	Split screen utilities and Linux window managers with multi-focus modes

Keyboard events

The on_key_press() and on_key_release() events are fired when any key on the keyboard is pressed or released, respectively. These events are not affected by “key repeat” – once a key is pressed there are no more events for that key until it is released.

Both events are parameterised by the same arguments:

def on_key_press(symbol, modifiers):
    pass

def on_key_release(symbol, modifiers):
    pass

Defined key symbols

The symbol argument is an integer that represents a “virtual” key code. It does not correspond to any particular numbering scheme; in particular the symbol is not an ASCII character code.

pyglet has key symbols that are hardware and platform independent for many types of keyboard. These are defined in pyglet.window.key as constants. For example, the Latin-1 alphabet is simply the letter itself:

key.A
key.B
key.C
...

The numeric keys have an underscore to make them valid identifiers:

key._1
key._2
key._3
...

Various control and directional keys are identified by name:

key.ENTER or key.RETURN
key.SPACE
key.BACKSPACE
key.DELETE
key.MINUS
key.EQUAL
key.BACKSLASH

key.LEFT
key.RIGHT
key.UP
key.DOWN
key.HOME
key.END
key.PAGEUP
key.PAGEDOWN

key.F1
key.F2
...

Keys on the number pad have separate symbols:

key.NUM_1
key.NUM_2
...
key.NUM_EQUAL
key.NUM_DIVIDE
key.NUM_MULTIPLY
key.NUM_SUBTRACT
key.NUM_ADD
key.NUM_DECIMAL
key.NUM_ENTER

Some modifier keys have separate symbols for their left and right sides (however they cannot all be distinguished on all platforms, including Mac OSX):

key.LCTRL
key.RCTRL
key.LSHIFT
key.RSHIFT
...

Key symbols are independent of any modifiers being active. For example, lower-case and upper-case letters both generate the A symbol. This is also true of the number keypad.

Modifiers

The modifiers that are active when the event is generated are combined in a bitwise fashion and provided in the modifiers parameter. The modifier constants defined in pyglet.window.key are:

MOD_SHIFT
MOD_CTRL
MOD_ALT         Not available on Mac OS X
MOD_WINDOWS     Available on Windows only
MOD_COMMAND     Available on Mac OS X only
MOD_OPTION      Available on Mac OS X only
MOD_CAPSLOCK
MOD_NUMLOCK
MOD_SCROLLLOCK
MOD_ACCEL       Equivalent to MOD_CTRL, or MOD_COMMAND on Mac OS X.

For example, to test if the shift key is held down:

if modifiers & MOD_SHIFT:
    pass

Unlike the corresponding key symbols, it is not possible to determine whether the left or right modifier is held down (though you could emulate this behaviour by keeping track of the key states yourself).

User-defined key symbols

pyglet does not define key symbols for every keyboard ever made. For example, non-Latin languages will have many keys not recognised by pyglet (however, their Unicode representations will still be valid, see Text Input and Motion Events). Even English keyboards often have additional so-called “OEM” keys added by the manufacturer, which might be labelled “Media”, “Volume” or “Shopping”, for example.

In these cases pyglet will create a key symbol at runtime based on the hardware scancode of the key. This is guaranteed to be unique for that model of keyboard, but may not be consistent across other keyboards with the same labelled key.

The best way to use these keys is to record what the user presses after a prompt, and then check for that same key symbol. Many commercial games have similar functionality in allowing players to set up their own key bindings.

Remembering key state

KeyStateHandler is a convenience class which stores the current keyboard state. Instances can be pushed onto the event handler stack of any window and subsequently queried using key code constants as keys:

from pyglet.window import key

window = pyglet.window.Window()
keys = key.KeyStateHandler()
window.push_handlers(keys)

# Check if the spacebar is currently pressed:
if keys[key.SPACE]:
    pass

Text Input and Motion Events

pyglet offers Unicode text input events in addition to individual key events. There are several benefits to this:

• Automatic and correct mapping of platform-specific modifiers and key symbols to Unicode characters

• Key repeat for held keys is automatically applied to text input according to the user’s operating system preferences.

• Dead keys and compose keys are automatically interpreted to produce diacritic marks or combining characters.

• Keyboard input can be routed via an input palette, for example to input characters from Asian languages.

• Text input can come from other user-defined sources, such as handwriting or voice recognition.

The actual source of input (i.e., which keys were pressed, or what input method was used) should be considered outside of the scope of the application – the operating system provides the necessary services.

When text is entered into a window, the on_text() event is fired:

def on_text(text):
    pass

The only parameter provided is a Unicode string. Although this will usually be one character long for direct keyboard input, more complex input methods such as an input palettes may provide entire words or phrases at once.

How does this differ from on_key_press()?

• Always use the on_text() event when you need a string from a series of keystrokes

• Never use the on_text() event when you need individual presses, such as controlling player movement in a game

Motion events

In addition to key presses and entering new text, pyglet also supports common text editing motions:

• Selecting text

• Moving the caret in response to non-character keys

• Deleting, copying, and pasting text

pyglet automatically detects and translates platform-specific versions of supported motions into cross-platform on_text_motion() events. These events are intended be handled by the Caret of any active IncrementalTextLayout, such as those used in TextEntry fields.

The motion argument to the event handler will be a constant value defined in pyglet.window.key. The table below lists the supported text motions with their keyboard mapping on each supported platform.

Constant	Behaviour	Windows/Linux	Mac OS X
MOTION_UP	Move the cursor up	Up	Up
MOTION_DOWN	Move the cursor down	Down	Down
MOTION_LEFT	Move the cursor left	Left	Left
MOTION_RIGHT	Move the cursor right	Right	Right
MOTION_COPY	Copy the current selection to the clipboard	Ctrl + C	Command + C
MOTION_PASTE	Paste the clipboard contents into the current document	Ctrl + V	Command + V
MOTION_PREVIOUS_WORD	Move the cursor to the previous word	Ctrl + Left	Option + Left
MOTION_NEXT_WORD	Move the cursor to the next word	Ctrl + Right	Option + Right
MOTION_BEGINNING_OF_LINE	Move the cursor to the beginning of the current line	Home	Command + Left
MOTION_END_OF_LINE	Move the cursor to the end of the current line	End	Command + Right
MOTION_PREVIOUS_PAGE	Move to the previous page	Page Up	Page Up
MOTION_NEXT_PAGE	Move to the next page	Page Down	Page Down
MOTION_BEGINNING_OF_FILE	Move to the beginning of the document	Ctrl + Home	Home
MOTION_END_OF_FILE	Move to the end of the document	Ctrl + End	End
MOTION_BACKSPACE	Delete the previous character	Backspace	Backspace
MOTION_DELETE	Delete the next character, or the current character	Delete	Delete

If you believe pyglet needs to add support for a motion which is currently missing, please skip to Adding New Motions.

Customizing this behavior for an individual project is currently difficult due to the way carets and text entry fields are interconnected. However, using on_key_press() to handle motion events should still be avoided for the following reasons:

• Supported platforms can assign a key to different motions. For example the Home key moves the cursor to the start of a line on Windows, but to the beginning of a document on Mac OS.

• Users expect holding down a motion’s keys to repeat it released. For example, holding Backspace deletes multiple characters. However, only one on_key_press() event occurs per keypress.

Adding New Motions

Before adding a new motion, please do the following:

1. Consult the previous section & each platform’s documentation to be sure it is:

   1. A common text operation present on every platform

   2. Not already implemented by pyglet

2. Attempt to find the corresponding functionality in Apple’s NSTextView documentation

3. Discuss the addition and any remaining questions with maintainers by either:

   • Filing a GitHub Issue

   • Discord or the mailing list

Then, once you’re ready:

1. Add the motion constant to pyglet.window.key

2. Add an entry for the constant in the Motion events section

3. Implement shared handling behavior in on_text_motion()

4. Implement Mac support (usually the most confusing step)

   1. Open pyglet/window/cocoa/pyglet_textview.py

   2. Implement a corresponding handler method on PygletTextView_Implementation (pyglet’s subclass of NSTextView)

5. Add the Windows keyboard shortcut

   1. Open pyglet/window/win32/__init__.py

   2. Add the keyboard shortcut to the _motion_map dictionary

6. Add the Linux keyboard shortcut

   1. Open pyglet/window/xlib/__init__.py

   2. Add the keyboard shortcut to the _motion_map dictionary

Be sure to test your changes before making a PR if possible!

If you do not have access to a specific platform above, include this in your PR’s notes.

Keyboard exclusivity

Some keystrokes or key combinations normally bypass applications and are handled by the operating system. Some examples are Alt+Tab (Command+Tab on Mac OS X) to switch applications and the keys mapped to Expose on Mac OS X.

You can disable these hot keys and have them behave as ordinary keystrokes for your application. This can be useful if you are developing a kiosk application which should not be closed, or a game in which it is possible for a user to accidentally press one of these keys.

To enable this mode, call Window.set_exclusive_keyboard on the window it should apply to. On Mac OS X, the dock and menu bar will slide out of view while exclusive keyboard is activated.

The following restrictions apply on Windows:

• Only Alt+Tab can be disabled

• Users will still be able to switch applications through:

  • Ctrl+Escape

  • Alt+Escape

  • the Windows key

  • Ctrl+Alt+Delete

The following restrictions apply on Mac OS X:

• The power key is not disabled.

Use of this function is not recommended for general release applications or games as it violates user-interface conventions.