Mouse Input¶

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

Quick Start¶

protected override void OnUpdate(GameTime gameTime)
{
    var mousePos = Input.MousePosition;

    if (Input.IsMouseButtonPressed(MouseButton.Left))
        SpawnAt(mousePos);

    if (Input.ScrollWheelDelta != 0)
        _zoom += Input.ScrollWheelDelta * 0.1f;
}

Mouse Position¶

// Absolute position in screen coordinates (top-left origin)
var pos = Input.MousePosition; // Vector2

// Movement delta since last frame (useful for camera/look control)
var delta = Input.MouseDelta; // Vector2
_cameraAngle += delta.X * _sensitivity;

Mouse Buttons¶

// Button held down
if (Input.IsMouseButtonDown(MouseButton.Left))
    DrawBrush(Input.MousePosition);

// Button just clicked this frame
if (Input.IsMouseButtonPressed(MouseButton.Left))
    SelectUnit(Input.MousePosition);

// Button just released
if (Input.IsMouseButtonReleased(MouseButton.Left))
    DropItem();

// Any mouse button pressed (attract/lobby screens)
if (Input.IsAnyMouseButtonPressed())
    StartGame();

Available buttons: Left, Right, Middle, X1, X2

Scroll Wheel¶

// Vertical scroll (positive = up, negative = down)
var scroll = Input.ScrollWheelDelta; // float
if (scroll > 0) ZoomIn();
if (scroll < 0) ZoomOut();

// Horizontal scroll (trackpads, horizontal scroll wheels)
var hScroll = Input.ScrollWheelDeltaX; // float

Cursor Visibility¶

// Hide the cursor (e.g. custom cursor or in-game reticle)
Input.IsCursorVisible = false;

// Show it again
Input.IsCursorVisible = true;

Relative Mouse Mode¶

When enabled the cursor is hidden, captured to the window, and MouseDelta reports frame-to-frame motion. MousePosition is not updated in this mode. Use it for first-person cameras and drag operations where you want unlimited movement range.

// Enable for FPS-style look
Input.IsRelativeMouseMode = true;

protected override void OnUpdate(GameTime gameTime)
{
    if (Input.IsRelativeMouseMode)
    {
        _cameraYaw   += Input.MouseDelta.X * _sensitivity;
        _cameraPitch += Input.MouseDelta.Y * _sensitivity;
    }
}

// Disable when returning to a menu
Input.IsRelativeMouseMode = false;

Common Patterns¶

Click Detection with Bounds¶

if (Input.IsMouseButtonPressed(MouseButton.Left))
{
    var pos = Input.MousePosition;
    if (pos.X >= _buttonX && pos.X <= _buttonX + _buttonWidth &&
        pos.Y >= _buttonY && pos.Y <= _buttonY + _buttonHeight)
    {
        OnButtonClicked();
    }
}

Drag and Drop¶

if (Input.IsMouseButtonPressed(MouseButton.Left))
{
    _dragStart = Input.MousePosition;
    _isDragging = true;
}

if (_isDragging)
    _dragOffset = Input.MousePosition - _dragStart;

if (Input.IsMouseButtonReleased(MouseButton.Left))
    _isDragging = false;

Camera Pan with Middle Mouse¶

if (Input.IsMouseButtonDown(MouseButton.Middle))
    _cameraPosition -= Input.MouseDelta;

Zoom with Scroll Wheel¶

var scroll = Input.ScrollWheelDelta;
if (scroll != 0)
    _zoom = Math.Clamp(_zoom + scroll * 0.1f, 0.5f, 3.0f);

Troubleshooting¶

Mouse Position Seems Wrong¶

MousePosition is in screen coordinates (top-left origin).
If using a camera, convert with camera.ScreenToWorld(pos).

Scroll Wheel Not Working¶

ScrollWheelDelta is a float, check != 0.
Poll in OnUpdate, not OnRender.
The value resets each frame -- do not accumulate it.

`MouseDelta` Always Zero¶

The mouse must actually be moving over the window.
In relative mode, MouseDelta reports the captured motion even when the cursor is at the window edge.

Summary¶

Property / Method	Returns	Usage
`MousePosition`	`Vector2`	Absolute screen position
`MouseDelta`	`Vector2`	Frame-to-frame movement
`ScrollWheelDelta`	`float`	Vertical scroll (positive = up)
`ScrollWheelDeltaX`	`float`	Horizontal scroll
`IsMouseButtonDown()`	`bool`	Button held
`IsMouseButtonPressed()`	`bool`	Button just clicked
`IsMouseButtonReleased()`	`bool`	Button just released
`IsAnyMouseButtonPressed()`	`bool`	Any button pressed this frame
`IsCursorVisible`	`bool`	Show / hide OS cursor
`IsRelativeMouseMode`	`bool`	Capture mouse for unlimited movement