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Keyboard Input

Handle keyboard input using the Input framework property (IInputContext) available in every scene.

Quick Start

protected override void OnUpdate(GameTime gameTime)
{
    var deltaTime = (float)gameTime.DeltaTime;

    // Continuous movement (held)
    if (Input.IsKeyDown(Key.W)) _position.Y -= _speed * deltaTime;
    if (Input.IsKeyDown(Key.S)) _position.Y += _speed * deltaTime;
    if (Input.IsKeyDown(Key.A)) _position.X -= _speed * deltaTime;
    if (Input.IsKeyDown(Key.D)) _position.X += _speed * deltaTime;

    // One-shot action (just pressed this frame)
    if (Input.IsKeyPressed(Key.Space)) Jump();

    // Release action
    if (Input.IsKeyReleased(Key.E)) ReleaseChargedAttack();
}

The Three Methods

IsKeyDown -- Key Currently Held

Returns true every frame while the key is held. Use for continuous actions like movement.

if (Input.IsKeyDown(Key.W))
    _position.Y -= _speed * deltaTime;

IsKeyPressed -- Just Pressed This Frame

Returns true only on the first frame the key is pressed. Use for one-shot actions.

if (Input.IsKeyPressed(Key.Space))
    Jump(); // Called once per press, not every frame

IsKeyReleased -- Just Released This Frame

Returns true only on the frame the key is released.

if (Input.IsKeyReleased(Key.E))
    ReleaseChargedAttack();

IsAnyKeyPressed -- Any Key This Frame

Returns true if any key was pressed this frame. Useful for "press any key to continue" screens.

if (Input.IsAnyKeyPressed())
    StartGame();

Common Patterns

WASD + Normalized Diagonal Movement

protected override void OnUpdate(GameTime gameTime)
{
    var direction = Vector2.Zero;
    if (Input.IsKeyDown(Key.W)) direction.Y -= 1;
    if (Input.IsKeyDown(Key.S)) direction.Y += 1;
    if (Input.IsKeyDown(Key.A)) direction.X -= 1;
    if (Input.IsKeyDown(Key.D)) direction.X += 1;

    if (direction != Vector2.Zero)
        direction = Vector2.Normalize(direction);

    _position += direction * _speed * (float)gameTime.DeltaTime;
}

Sprint Modifier

var speed = Input.IsKeyDown(Key.LeftShift) ? _sprintSpeed : _walkSpeed;
_position += direction * speed * deltaTime;

Key Combinations

if (Input.IsKeyDown(Key.LeftControl) && Input.IsKeyPressed(Key.S))
    SaveGame();
if (Input.IsKeyPressed(Key.Up))     _selectedIndex--;
if (Input.IsKeyPressed(Key.Down))   _selectedIndex++;
if (Input.IsKeyPressed(Key.Enter))  SelectMenuItem(_selectedIndex);

The Key Enum

using Brine2D.Input;

Key.A through Key.Z           // Letters
Key.D0 through Key.D9         // Number row
Key.F1 through Key.F24        // Function keys
Key.Space                     // Spacebar
Key.Enter                     // Enter/Return
Key.Escape                    // Escape
Key.LeftShift, Key.RightShift
Key.LeftControl, Key.RightControl
Key.LeftAlt, Key.RightAlt
Key.Up, Key.Down, Key.Left, Key.Right   // Arrow keys
Key.Tab, Key.Backspace, Key.Delete
Key.LeftSuper, Key.RightSuper           // Windows/Command key
Key.CapsLock

Text Input

For text fields and chat boxes, use the dedicated text input API instead of polling individual keys. This correctly handles Unicode, IME, and keyboard layouts:

Input.StartTextInput();

protected override void OnUpdate(GameTime gameTime)
{
    if (!Input.IsTextInputActive) return;

    var text = Input.GetTextInput();
    if (!string.IsNullOrEmpty(text))
        _textBuffer += text;

    if (Input.IsBackspacePressed() && _textBuffer.Length > 0)
        _textBuffer = _textBuffer[..^1];

    if (Input.IsDeletePressed())
        // Handle forward delete

    if (Input.IsReturnPressed())
    {
        SubmitText(_textBuffer);
        Input.StopTextInput();
    }
}

Note

IsBackspacePressed(), IsReturnPressed(), and IsDeletePressed() fire on key-repeat (held key) for expected text-editing behavior. They work regardless of whether text input mode is active.

Troubleshooting

Keys Not Responding

  1. Check you are in OnUpdate, not OnRender
  2. Click the game window -- input only works when focused

Action Repeats Unexpectedly

Use IsKeyPressed, not IsKeyDown:

// Wrong -- fires every frame while held
if (Input.IsKeyDown(Key.Space)) Jump();

// Correct -- fires once per press
if (Input.IsKeyPressed(Key.Space)) Jump();

Diagonal Movement Is Faster

Normalize the direction vector:

if (direction != Vector2.Zero)
    direction = Vector2.Normalize(direction);

Summary

Method Usage
IsKeyDown(key) Key currently held -- movement, sprint
IsKeyPressed(key) Key just pressed -- jump, shoot, toggle
IsKeyReleased(key) Key just released -- charge attacks
IsAnyKeyPressed() Any key pressed -- attract screens

Next Steps