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Avalonia provides a unified pointer event system that handles mouse input along with other pointer types (touch, pen). The mouse device processes raw pointer events and dispatches them to controls.

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PointerEventArgs

Base class for pointer-related events, including mouse events.

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Properties

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Pointer
IPointer
Gets the specific pointer generated by the input device. Each mouse, touch contact, or pen has its own pointer ID.
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Timestamp
ulong
Gets the time when the input occurred, in milliseconds.
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KeyModifiers
KeyModifiers
Gets a value that indicates which key modifiers (Ctrl, Shift, Alt) were active when the pointer event was initiated.
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Properties
PointerPointProperties
Gets the state of the pointer device when this event occurred, including which buttons are pressed.

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Methods

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GetPosition
Point
Gets the pointer position relative to a control.
Point position = e.GetPosition(myControl);
Pass null to get the position in toplevel coordinates.
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GetCurrentPoint
PointerPoint
Returns the PointerPoint associated with the current event, relative to the specified visual.
PointerPoint point = e.GetCurrentPoint(this);
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GetIntermediatePoints
IReadOnlyList<PointerPoint>
Returns intermediate pointer points that occurred between the last event and this one. Useful for smooth drawing or gesture recognition.
var points = e.GetIntermediatePoints(canvas);
foreach (var point in points)
{
    DrawPoint(point.Position);
}
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PreventGestureRecognition
void
Prevents this event from being handled by gesture recognizers in the route.
e.PreventGestureRecognition();

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PointerPressedEventArgs

Provides information for pointer pressed (mouse down) events.

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Properties

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ClickCount
int
Gets the number of clicks (1 for single click, 2 for double click, etc.).

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PointerReleasedEventArgs

Provides information for pointer released (mouse up) events.

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Properties

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InitialPressMouseButton
MouseButton
Gets the mouse button that triggered the corresponding PointerPressed event.

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PointerWheelEventArgs

Provides information for mouse wheel events.

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Properties

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Delta
Vector
Gets the mouse wheel delta.
  • Delta.Y represents vertical scrolling (positive = scroll up, negative = scroll down)
  • Delta.X represents horizontal scrolling (if supported)

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MouseButton Enumeration

Defines mouse buttons:
  • None - No button
  • Left - Left mouse button
  • Right - Right mouse button
  • Middle - Middle mouse button (wheel click)
  • XButton1 - First extended button
  • XButton2 - Second extended button

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PointerPointProperties

Describes the state of a pointer device.

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Properties

  • IsLeftButtonPressed - Gets whether the left button is pressed
  • IsRightButtonPressed - Gets whether the right button is pressed
  • IsMiddleButtonPressed - Gets whether the middle button is pressed
  • IsXButton1Pressed - Gets whether the first extended button is pressed
  • IsXButton2Pressed - Gets whether the second extended button is pressed
  • PointerUpdateKind - Gets the type of pointer update (left/right/middle button down/up, etc.)

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Usage Examples

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Handling Mouse Click Events

public class MyControl : Control
{
    protected override void OnPointerPressed(PointerPressedEventArgs e)
    {
        var point = e.GetCurrentPoint(this);
        
        if (point.Properties.IsLeftButtonPressed)
        {
            // Handle left click
            if (e.ClickCount == 2)
            {
                // Double click
                OnDoubleClick();
            }
            else
            {
                // Single click
                OnSingleClick();
            }
            e.Handled = true;
        }
        else if (point.Properties.IsRightButtonPressed)
        {
            // Show context menu
            ShowContextMenu(e.GetPosition(this));
            e.Handled = true;
        }
        
        base.OnPointerPressed(e);
    }
}

​
Tracking Mouse Movement

private bool _isDragging;
private Point _startPoint;

protected override void OnPointerPressed(PointerPressedEventArgs e)
{
    var point = e.GetCurrentPoint(this);
    if (point.Properties.IsLeftButtonPressed)
    {
        _isDragging = true;
        _startPoint = e.GetPosition(this);
        e.Pointer.Capture(this);
        e.Handled = true;
    }
}

protected override void OnPointerMoved(PointerEventArgs e)
{
    if (_isDragging)
    {
        var currentPoint = e.GetPosition(this);
        var delta = currentPoint - _startPoint;
        
        // Update position or perform drag operation
        UpdateDragPosition(delta);
        e.Handled = true;
    }
}

protected override void OnPointerReleased(PointerReleasedEventArgs e)
{
    if (_isDragging)
    {
        _isDragging = false;
        e.Pointer.Capture(null);
        e.Handled = true;
    }
}

​
Handling Mouse Wheel

protected override void OnPointerWheelChanged(PointerWheelEventArgs e)
{
    // Zoom with Ctrl + Wheel
    if (e.KeyModifiers.HasFlag(KeyModifiers.Control))
    {
        var zoomDelta = e.Delta.Y;
        if (zoomDelta > 0)
        {
            ZoomIn();
        }
        else if (zoomDelta < 0)
        {
            ZoomOut();
        }
        e.Handled = true;
    }
    else
    {
        // Normal scrolling
        Scroll(e.Delta.Y * ScrollSpeed);
    }
    
    base.OnPointerWheelChanged(e);
}

​
Drawing with Mouse

private readonly List<Point> _points = new();

protected override void OnPointerPressed(PointerPressedEventArgs e)
{
    var point = e.GetCurrentPoint(this);
    if (point.Properties.IsLeftButtonPressed)
    {
        _points.Clear();
        _points.Add(e.GetPosition(this));
        e.Pointer.Capture(this);
    }
}

protected override void OnPointerMoved(PointerEventArgs e)
{
    if (e.Pointer.Captured == this)
    {
        // Get all intermediate points for smooth drawing
        var intermediatePoints = e.GetIntermediatePoints(this);
        foreach (var point in intermediatePoints)
        {
            _points.Add(point.Position);
        }
        InvalidateVisual();
    }
}

public override void Render(DrawingContext context)
{
    if (_points.Count > 1)
    {
        var pen = new Pen(Brushes.Black, 2);
        for (int i = 0; i < _points.Count - 1; i++)
        {
            context.DrawLine(pen, _points[i], _points[i + 1]);
        }
    }
}

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Checking Modifier Keys

protected override void OnPointerPressed(PointerPressedEventArgs e)
{
    var point = e.GetCurrentPoint(this);
    
    if (point.Properties.IsLeftButtonPressed)
    {
        if (e.KeyModifiers.HasFlag(KeyModifiers.Control))
        {
            // Ctrl+Click: Add to selection
            AddToSelection();
        }
        else if (e.KeyModifiers.HasFlag(KeyModifiers.Shift))
        {
            // Shift+Click: Extend selection
            ExtendSelection();
        }
        else
        {
            // Normal click: Replace selection
            ReplaceSelection();
        }
    }
}

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Best Practices

  1. Use Pointer Events: Prefer PointerPressed, PointerMoved, PointerReleased over legacy mouse events for better cross-platform support
  2. Capture the Pointer: Use e.Pointer.Capture(this) during drag operations to ensure you receive all events
  3. Release Capture: Always release capture with e.Pointer.Capture(null) when done
  4. Mark Events as Handled: Set e.Handled = true to prevent event bubbling
  5. Check PointerType: Use e.Pointer.Type to distinguish between mouse, touch, and pen input
  6. Use Intermediate Points: For drawing or gesture recognition, use GetIntermediatePoints() to avoid missing events

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