azul_layout/managers/

gesture.rs

//! Gesture and drag manager for multi-frame gestures and drag operations.
//!
//! Collects input samples, detects drags, double-clicks, long presses, swipes,
//! pinch/rotate gestures, and manages drag state for nodes, windows, and file drops.
//!
//! ## Unified Drag System
//!
//! This module uses the `DragContext` from `azul_core::drag` to provide a unified
//! interface for all drag operations:
//! - Text selection drag
//! - Scrollbar thumb drag
//! - Node drag-and-drop
//! - Window drag/resize
//! - File drop from OS

use alloc::{collections::btree_map::BTreeMap, vec::Vec};
#[cfg(feature = "std")]
use std::sync::atomic::{AtomicU64, Ordering};

use azul_core::{
    dom::{DomId, NodeId, OptionDomNodeId},
    drag::{
        ActiveDragType, AutoScrollDirection, DragContext, DragData, DragEffect, DropEffect,
        FileDropDrag, NodeDrag, ScrollbarAxis, ScrollbarThumbDrag, TextSelectionDrag,
        WindowMoveDrag, WindowResizeDrag, WindowResizeEdge,
    },
    geom::{LogicalPosition, PhysicalPositionI32},
    hit_test::HitTest,
    selection::TextCursor,
    task::{Duration as CoreDuration, Instant as CoreInstant},
    window::WindowPosition,
};
use azul_css::AzString;
use azul_css::{impl_option, impl_option_inner, StringVec};

// Re-export drag types for convenience
pub use azul_core::drag::{
    ActiveDragType as DragType, AutoScrollDirection as AutoScroll, DragContext as UnifiedDragContext,
    DragData as UnifiedDragData, DragEffect as UnifiedDragEffect, DropEffect as UnifiedDropEffect,
    ScrollbarAxis as ScrollAxis, ScrollbarThumbDrag as ScrollbarDrag,
};

#[cfg(feature = "std")]
static NEXT_EVENT_ID: AtomicU64 = AtomicU64::new(1);

/// Allocate a new unique event ID
#[cfg(feature = "std")]
pub fn allocate_event_id() -> u64 {
    NEXT_EVENT_ID.fetch_add(1, Ordering::Relaxed)
}

/// Allocate a new unique event ID (no_std fallback: returns 0)
#[cfg(not(feature = "std"))]
pub fn allocate_event_id() -> u64 {
    0
}

/// Helper function to convert CoreDuration to milliseconds
///
/// CoreDuration is an enum with System (std::time::Duration) and Tick variants.
/// We need to handle both cases for proper time calculations.
fn duration_to_millis(duration: CoreDuration) -> u64 {
    match duration {
        #[cfg(feature = "std")]
        CoreDuration::System(system_diff) => {
            let std_duration: std::time::Duration = system_diff.into();
            std_duration.as_millis() as u64
        }
        #[cfg(not(feature = "std"))]
        CoreDuration::System(system_diff) => {
            // Manual calculation: secs * 1000 + nanos / 1_000_000
            system_diff.secs * 1000 + (system_diff.nanos / 1_000_000) as u64
        }
        CoreDuration::Tick(tick_diff) => {
            // Assume tick = 1ms for simplicity (platform-specific)
            tick_diff.tick_diff
        }
    }
}

/// Maximum number of input samples to keep in memory
///
/// This prevents unbounded memory growth during long drags.
/// Older samples beyond this limit are automatically discarded.
pub const MAX_SAMPLES_PER_SESSION: usize = 1000;

/// Default timeout for clearing old gesture samples (milliseconds)
///
/// Samples older than this are automatically removed to prevent
/// memory leaks and stale gesture detection.
pub const DEFAULT_SAMPLE_TIMEOUT_MS: u64 = 2000;

/// Configuration for gesture detection thresholds
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct GestureDetectionConfig {
    /// Minimum distance (pixels) to consider movement a drag, not a click
    pub drag_distance_threshold: f32,
    /// Maximum time between clicks for double-click detection (milliseconds)
    pub double_click_time_threshold_ms: u64,
    /// Maximum distance between clicks for double-click detection (pixels)
    pub double_click_distance_threshold: f32,
    /// Minimum time to hold button for long-press detection (milliseconds)
    pub long_press_time_threshold_ms: u64,
    /// Maximum distance to move while holding for long-press (pixels)
    pub long_press_distance_threshold: f32,
    /// Minimum samples needed to detect a gesture
    pub min_samples_for_gesture: usize,
    /// Minimum velocity for swipe detection (pixels per second)
    pub swipe_velocity_threshold: f32,
    /// Minimum scale change for pinch detection (e.g., 0.1 = 10% change)
    pub pinch_scale_threshold: f32,
    /// Minimum rotation angle for rotation detection (radians)
    pub rotation_angle_threshold: f32,
    /// How often to clear old samples (milliseconds)
    pub sample_cleanup_interval_ms: u64,
}

impl Default for GestureDetectionConfig {
    fn default() -> Self {
        Self {
            drag_distance_threshold: 5.0,
            double_click_time_threshold_ms: 500,
            double_click_distance_threshold: 5.0,
            long_press_time_threshold_ms: 500,
            long_press_distance_threshold: 10.0,
            min_samples_for_gesture: 2,
            swipe_velocity_threshold: 500.0, // 500 px/s
            pinch_scale_threshold: 0.1,      // 10% scale change
            rotation_angle_threshold: 0.1,   // ~5.7 degrees in radians
            sample_cleanup_interval_ms: DEFAULT_SAMPLE_TIMEOUT_MS,
        }
    }
}

/// Single input sample with position and timestamp
#[derive(Debug, Clone, PartialEq)]
pub struct InputSample {
    /// Position in logical coordinates (window-local, Y=0 at top of window)
    pub position: LogicalPosition,
    /// Position in virtual screen coordinates (Y=0 at top of primary monitor).
    ///
    /// Computed as `window_position + position` at the time the sample is recorded.
    /// This is stable during window drags because `window_pos + cursor_local`
    /// always equals the true screen position, even when the window moves.
    ///
    /// All coordinates are in logical pixels (HiDPI-independent).
    /// On Wayland, this is an estimate (compositor does not expose global position).
    pub screen_position: LogicalPosition,
    /// Timestamp when this sample was recorded (from ExternalSystemCallbacks)
    pub timestamp: CoreInstant,
    /// Mouse button state (bitfield: 0x01 = left, 0x02 = right, 0x04 = middle)
    pub button_state: u8,
    /// Unique, monotonic event ID for ordering (atomic counter)
    pub event_id: u64,
    /// Pen/stylus pressure (0.0 to 1.0, 0.5 = default for mouse)
    pub pressure: f32,
    /// Pen/stylus tilt angles in degrees (x_tilt, y_tilt)
    /// Range: typically -90.0 to 90.0, (0.0, 0.0) = perpendicular
    pub tilt: (f32, f32),
    /// Touch contact radius in logical pixels (width, height)
    /// For mouse input, this is (0.0, 0.0)
    pub touch_radius: (f32, f32),
}

impl_option!(
    InputSample,
    OptionInputSample,
    copy = false,
    [Debug, Clone, PartialEq]
);

/// A sequence of input samples forming one button press session
#[derive(Debug, Clone, PartialEq)]
pub struct InputSession {
    /// All recorded samples for this session
    pub samples: Vec<InputSample>,
    /// Whether this session has ended (button released)
    pub ended: bool,
    /// Session ID for tracking (incremental counter)
    pub session_id: u64,
    /// Window position at the time this session started (mouse-down).
    /// Used by titlebar drag callbacks to compute new window position.
    pub window_position_at_start: azul_core::window::WindowPosition,
}

impl InputSession {
    /// Create a new input session
    fn new(session_id: u64, first_sample: InputSample, window_position: azul_core::window::WindowPosition) -> Self {
        Self {
            samples: vec![first_sample],
            ended: false,
            session_id,
            window_position_at_start: window_position,
        }
    }

    /// Get the first sample in this session
    pub fn first_sample(&self) -> Option<&InputSample> {
        self.samples.first()
    }

    /// Get the last sample in this session
    pub fn last_sample(&self) -> Option<&InputSample> {
        self.samples.last()
    }

    /// Get the duration of this session (first to last sample)
    pub fn duration_ms(&self) -> Option<u64> {
        let first = self.first_sample()?;
        let last = self.last_sample()?;
        let duration = last.timestamp.duration_since(&first.timestamp);
        Some(duration_to_millis(duration))
    }

    /// Get the total distance traveled in this session
    pub fn total_distance(&self) -> f32 {
        if self.samples.len() < 2 {
            return 0.0;
        }

        let mut total = 0.0;
        for i in 1..self.samples.len() {
            let prev = &self.samples[i - 1];
            let curr = &self.samples[i];
            let dx = curr.position.x - prev.position.x;
            let dy = curr.position.y - prev.position.y;
            total += (dx * dx + dy * dy).sqrt();
        }
        total
    }

    /// Get the straight-line distance from first to last sample
    pub fn direct_distance(&self) -> Option<f32> {
        let first = self.first_sample()?;
        let last = self.last_sample()?;
        let dx = last.position.x - first.position.x;
        let dy = last.position.y - first.position.y;
        Some((dx * dx + dy * dy).sqrt())
    }
}

/// Result of drag detection analysis
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct DetectedDrag {
    /// Position where drag started
    pub start_position: LogicalPosition,
    /// Current/end position of drag
    pub current_position: LogicalPosition,
    /// Direct distance dragged (straight line, pixels)
    pub direct_distance: f32,
    /// Total distance dragged (following path, pixels)
    pub total_distance: f32,
    /// Duration of the drag (milliseconds)
    pub duration_ms: u64,
    /// Number of position samples recorded
    pub sample_count: usize,
    /// Session ID this drag belongs to
    pub session_id: u64,
}

/// Result of long-press detection
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct DetectedLongPress {
    /// Position where long press is happening
    pub position: LogicalPosition,
    /// How long the button has been held (milliseconds)
    pub duration_ms: u64,
    /// Whether the callback has already been invoked for this long press
    pub callback_invoked: bool,
    /// Session ID this long press belongs to
    pub session_id: u64,
}

/// Primary direction of a gesture
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum GestureDirection {
    Up,
    Down,
    Left,
    Right,
}

/// Result of pinch gesture detection
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct DetectedPinch {
    /// Scale factor (< 1.0 for pinch in, > 1.0 for pinch out)
    pub scale: f32,
    /// Center point of the pinch gesture
    pub center: LogicalPosition,
    /// Initial distance between touch points
    pub initial_distance: f32,
    /// Current distance between touch points
    pub current_distance: f32,
    /// Duration of pinch (milliseconds)
    pub duration_ms: u64,
}

/// Result of rotation gesture detection
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct DetectedRotation {
    /// Rotation angle in radians (positive = clockwise)
    pub angle_radians: f32,
    /// Center point of rotation
    pub center: LogicalPosition,
    /// Duration of rotation (milliseconds)
    pub duration_ms: u64,
}

// NOTE: NodeDragState, WindowDragState, FileDropState, DropEffect, DragData, DragEffect
// are now defined in azul_core::drag and imported above.
// The old types are kept as type aliases for backwards compatibility.

/// State of an active node drag (after detection)
/// DEPRECATED: Use `DragContext` with `ActiveDragType::Node` instead.
pub type NodeDragState = NodeDrag;

/// State of window being dragged (titlebar drag)
/// DEPRECATED: Use `DragContext` with `ActiveDragType::WindowMove` instead.
pub type WindowDragState = WindowMoveDrag;

/// State of file(s) being dragged from OS over the window
/// DEPRECATED: Use `DragContext` with `ActiveDragType::FileDrop` instead.
pub type FileDropState = FileDropDrag;

/// State of pen/stylus input
#[derive(Debug, Clone, Copy, PartialEq)]
#[repr(C)]
pub struct PenState {
    /// Current pen position
    pub position: LogicalPosition,
    /// Current pressure (0.0 to 1.0)
    pub pressure: f32,
    /// Current tilt angles (x_tilt, y_tilt) in degrees
    pub tilt: crate::callbacks::PenTilt,
    /// Whether pen is in contact with surface
    pub in_contact: bool,
    /// Whether pen is inverted (eraser mode)
    pub is_eraser: bool,
    /// Whether barrel button is pressed
    pub barrel_button_pressed: bool,
    /// Unique identifier for this pen device
    pub device_id: u64,
}

impl_option!(PenState, OptionPenState, [Debug, Clone, Copy, PartialEq]);

impl Default for PenState {
    fn default() -> Self {
        Self {
            position: LogicalPosition::zero(),
            pressure: 0.0,
            tilt: crate::callbacks::PenTilt {
                x_tilt: 0.0,
                y_tilt: 0.0,
            },
            in_contact: false,
            is_eraser: false,
            barrel_button_pressed: false,
            device_id: 0,
        }
    }
}

/// Manager for multi-frame gestures and drag operations
///
/// This collects raw input samples and analyzes them to detect gestures.
/// Designed for testability and clear separation of input collection
/// vs. detection.
///
/// ## Unified Drag System
///
/// The manager now uses `DragContext` to unify all drag types:
/// - `active_drag`: The unified drag context (replaces individual drag states)
///
/// For backwards compatibility, the old `node_drag`, `window_drag`, `file_drop`
/// fields are still accessible but deprecated.
#[derive(Debug, Clone, PartialEq)]
pub struct GestureAndDragManager {
    /// Configuration for gesture detection
    pub config: GestureDetectionConfig,
    /// All recorded input sessions (multiple button press sequences)
    pub input_sessions: Vec<InputSession>,
    /// **NEW**: Unified drag context for all drag types
    pub active_drag: Option<DragContext>,
    /// Current pen/stylus state
    pub pen_state: Option<PenState>,
    /// Session IDs where long press callback has been invoked
    long_press_callbacks_invoked: Vec<u64>,
    /// Counter for generating unique session IDs
    next_session_id: u64,
}

/// Type alias for backwards compatibility
pub type GestureManager = GestureAndDragManager;

impl Default for GestureAndDragManager {
    fn default() -> Self {
        Self::new()
    }
}

impl GestureAndDragManager {
    /// Create a new gesture and drag manager
    pub fn new() -> Self {
        Self {
            config: GestureDetectionConfig::default(),
            input_sessions: Vec::new(),
            next_session_id: 1,
            active_drag: None,
            pen_state: None,
            long_press_callbacks_invoked: Vec::new(),
        }
    }

    /// Create with custom configuration
    pub fn with_config(config: GestureDetectionConfig) -> Self {
        Self {
            config,
            ..Self::new()
        }
    }

    // Input Recording Methods (called from event loop / system timer)

    /// Start a new input session (mouse button pressed down)
    ///
    /// This begins recording samples for gesture detection.
    /// Call this when receiving mouse button down event.
    ///
    /// `window_position` is the current OS window position at the time of mouse-down.
    /// It is stored so that drag callbacks can compute the new window position.
    ///
    /// Returns the session ID for this new session.
    pub fn start_input_session(
        &mut self,
        position: LogicalPosition,
        timestamp: CoreInstant,
        button_state: u8,
        window_position: azul_core::window::WindowPosition,
        screen_position: LogicalPosition,
    ) -> u64 {
        self.start_input_session_with_pen(
            position,
            timestamp,
            button_state,
            allocate_event_id(),
            0.5,        // default pressure for mouse
            (0.0, 0.0), // no tilt for mouse
            (0.0, 0.0), // no touch radius for mouse
            window_position,
            screen_position,
        )
    }

    /// Start a new input session with pen/touch data
    pub fn start_input_session_with_pen(
        &mut self,
        position: LogicalPosition,
        timestamp: CoreInstant,
        button_state: u8,
        event_id: u64,
        pressure: f32,
        tilt: (f32, f32),
        touch_radius: (f32, f32),
        window_position: azul_core::window::WindowPosition,
        screen_position: LogicalPosition,
    ) -> u64 {
        // Clear old ended sessions, but keep the most recent ended session
        // for double-click detection. detect_double_click() needs two ended
        // sessions to compare timing and distance.
        let last_ended_idx = self.input_sessions.iter().rposition(|s| s.ended);
        let mut idx = 0usize;
        self.input_sessions.retain(|session| {
            let keep = !session.ended || Some(idx) == last_ended_idx;
            idx += 1;
            keep
        });

        let session_id = self.next_session_id;
        self.next_session_id += 1;

        let sample = InputSample {
            position,
            screen_position,
            timestamp,
            button_state,
            event_id,
            pressure,
            tilt,
            touch_radius,
        };

        let session = InputSession::new(session_id, sample, window_position);
        self.input_sessions.push(session);

        session_id
    }

    /// Record an input sample to the current session
    ///
    /// Call this on every mouse move event while button is pressed,
    /// and also periodically from a system timer to track long presses.
    ///
    /// Returns true if sample was recorded, false if no active session.
    pub fn record_input_sample(
        &mut self,
        position: LogicalPosition,
        timestamp: CoreInstant,
        button_state: u8,
        screen_position: LogicalPosition,
    ) -> bool {
        self.record_input_sample_with_pen(
            position,
            timestamp,
            button_state,
            allocate_event_id(),
            0.5,        // default pressure for mouse
            (0.0, 0.0), // no tilt for mouse
            (0.0, 0.0), // no touch radius for mouse
            screen_position,
        )
    }

    /// Record an input sample with pen/touch data
    pub fn record_input_sample_with_pen(
        &mut self,
        position: LogicalPosition,
        timestamp: CoreInstant,
        button_state: u8,
        event_id: u64,
        pressure: f32,
        tilt: (f32, f32),
        touch_radius: (f32, f32),
        screen_position: LogicalPosition,
    ) -> bool {
        let session = match self.input_sessions.last_mut() {
            Some(s) => s,
            None => return false,
        };

        if session.ended {
            return false;
        }

        // Enforce max samples limit
        if session.samples.len() >= MAX_SAMPLES_PER_SESSION {
            // Remove oldest samples, keeping the most recent ones
            let remove_count = session.samples.len() - MAX_SAMPLES_PER_SESSION + 100;
            session.samples.drain(0..remove_count);
        }

        session.samples.push(InputSample {
            position,
            screen_position,
            timestamp,
            button_state,
            event_id,
            pressure,
            tilt,
            touch_radius,
        });

        true
    }

    /// End the current input session (mouse button released)
    ///
    /// Call this when receiving mouse button up event.
    /// The session is kept for analysis but marked as ended.
    pub fn end_current_session(&mut self) {
        if let Some(session) = self.input_sessions.last_mut() {
            session.ended = true;
        }
    }

    /// Clear old input sessions that have timed out
    ///
    /// Call this periodically (e.g., every frame) to prevent memory leaks.
    /// Sessions older than `config.sample_cleanup_interval_ms` are removed.
    pub fn clear_old_sessions(&mut self, current_time: CoreInstant) {
        self.input_sessions.retain(|session| {
            if let Some(last_sample) = session.last_sample() {
                let duration = current_time.duration_since(&last_sample.timestamp);
                let age_ms = duration_to_millis(duration);
                age_ms < self.config.sample_cleanup_interval_ms
            } else {
                false
            }
        });

        // Also clear long press callback tracking for removed sessions
        let valid_session_ids: Vec<u64> =
            self.input_sessions.iter().map(|s| s.session_id).collect();

        self.long_press_callbacks_invoked
            .retain(|id| valid_session_ids.contains(id));
    }

    /// Clear all input sessions
    ///
    /// Call this when you want to reset all gesture detection state.
    pub fn clear_all_sessions(&mut self) {
        self.input_sessions.clear();
        self.long_press_callbacks_invoked.clear();
    }

    /// Update pen/stylus state
    ///
    /// Call this when receiving pen events from the platform.
    pub fn update_pen_state(
        &mut self,
        position: LogicalPosition,
        pressure: f32,
        tilt: (f32, f32),
        in_contact: bool,
        is_eraser: bool,
        barrel_button_pressed: bool,
        device_id: u64,
    ) {
        self.pen_state = Some(PenState {
            position,
            pressure,
            tilt: crate::callbacks::PenTilt {
                x_tilt: tilt.0,
                y_tilt: tilt.1,
            },
            in_contact,
            is_eraser,
            barrel_button_pressed,
            device_id,
        });
    }

    /// Clear pen state (when pen leaves proximity)
    pub fn clear_pen_state(&mut self) {
        self.pen_state = None;
    }

    /// Get current pen state (read-only)
    pub fn get_pen_state(&self) -> Option<&PenState> {
        self.pen_state.as_ref()
    }

    // Gesture Detection Methods (query state without mutation)

    /// Detect if current input represents a drag gesture
    ///
    /// Returns Some(DetectedDrag) if a drag is detected based on distance threshold.
    pub fn detect_drag(&self) -> Option<DetectedDrag> {
        let session = self.get_current_session()?;

        if session.samples.len() < self.config.min_samples_for_gesture {
            return None;
        }

        let direct_distance = session.direct_distance()?;

        if direct_distance >= self.config.drag_distance_threshold {
            let first = session.first_sample()?;
            let last = session.last_sample()?;

            Some(DetectedDrag {
                start_position: first.position,
                current_position: last.position,
                direct_distance,
                total_distance: session.total_distance(),
                duration_ms: session.duration_ms()?,
                sample_count: session.samples.len(),
                session_id: session.session_id,
            })
        } else {
            None
        }
    }

    /// Detect if current input represents a long press
    ///
    /// Returns Some(DetectedLongPress) if button has been held long enough
    /// without moving much.
    pub fn detect_long_press(&self) -> Option<DetectedLongPress> {
        let session = self.get_current_session()?;

        if session.ended {
            return None; // Can't be long press if button already released
        }

        let duration_ms = session.duration_ms()?;

        if duration_ms < self.config.long_press_time_threshold_ms {
            return None;
        }

        let distance = session.direct_distance()?;

        if distance <= self.config.long_press_distance_threshold {
            let first = session.first_sample()?;
            let callback_invoked = self
                .long_press_callbacks_invoked
                .contains(&session.session_id);

            Some(DetectedLongPress {
                position: first.position,
                duration_ms,
                callback_invoked,
                session_id: session.session_id,
            })
        } else {
            None
        }
    }

    /// Mark long press callback as invoked for a session
    ///
    /// Call this after invoking the long press callback to prevent
    /// repeated invocations.
    pub fn mark_long_press_callback_invoked(&mut self, session_id: u64) {
        if !self.long_press_callbacks_invoked.contains(&session_id) {
            self.long_press_callbacks_invoked.push(session_id);
        }
    }

    /// Detect if last two sessions form a double-click.
    ///
    /// Returns true if timing and distance match double-click criteria.
    pub fn detect_double_click(&self) -> bool {
        let sessions = &self.input_sessions;
        if sessions.len() < 2 {
            return false;
        }

        let prev_session = &sessions[sessions.len() - 2];
        let last_session = &sessions[sessions.len() - 1];

        // Both sessions must have ended (button released)
        if !prev_session.ended || !last_session.ended {
            return false;
        }

        let prev_first = prev_session.first_sample();
        let last_first = last_session.first_sample();
        let (prev_first, last_first) = match (prev_first, last_first) {
            (Some(p), Some(l)) => (p, l),
            _ => return false,
        };

        let duration = last_first.timestamp.duration_since(&prev_first.timestamp);
        let time_delta_ms = duration_to_millis(duration);
        if time_delta_ms > self.config.double_click_time_threshold_ms {
            return false;
        }

        let dx = last_first.position.x - prev_first.position.x;
        let dy = last_first.position.y - prev_first.position.y;
        let distance = (dx * dx + dy * dy).sqrt();

        distance < self.config.double_click_distance_threshold
    }

    /// Get the primary direction of current drag.
    pub fn get_drag_direction(&self) -> Option<GestureDirection> {
        let session = self.get_current_session()?;
        let first = session.first_sample()?;
        let last = session.last_sample()?;

        let dx = last.position.x - first.position.x;
        let dy = last.position.y - first.position.y;

        let direction = if dx.abs() > dy.abs() {
            if dx > 0.0 {
                GestureDirection::Right
            } else {
                GestureDirection::Left
            }
        } else {
            if dy > 0.0 {
                GestureDirection::Down
            } else {
                GestureDirection::Up
            }
        };
        Some(direction)
    }

    /// Get average velocity of current gesture (pixels per second)
    pub fn get_gesture_velocity(&self) -> Option<f32> {
        let session = self.get_current_session()?;

        if session.samples.len() < 2 {
            return None;
        }

        let total_distance = session.total_distance();
        let duration_ms = session.duration_ms()?;

        if duration_ms == 0 {
            return None;
        }

        let duration_secs = duration_ms as f32 / 1000.0;
        Some(total_distance / duration_secs)
    }

    /// Check if current gesture is a swipe (fast directional movement).
    pub fn is_swipe(&self) -> bool {
        self.get_gesture_velocity()
            .map(|v| v >= self.config.swipe_velocity_threshold)
            .unwrap_or(false)
    }

    /// Detect swipe with specific direction
    ///
    /// Returns Some(dir) if gesture is a fast swipe in a clear direction
    pub fn detect_swipe_direction(&self) -> Option<GestureDirection> {
        // Must be a fast swipe first
        if !self.is_swipe() {
            return None;
        }

        // Get direction
        self.get_drag_direction()
    }

    /// Detect pinch gesture (two-touch zoom in/out)
    ///
    /// Returns Some if two touch points are active and distance is changing
    /// significantly. Scale < 1.0 = pinch in, scale > 1.0 = pinch out.
    pub fn detect_pinch(&self) -> Option<DetectedPinch> {
        // Need at least two active sessions for pinch
        if self.input_sessions.len() < 2 {
            return None;
        }

        // Get last two sessions (most recent touches)
        let session1 = &self.input_sessions[self.input_sessions.len() - 2];
        let session2 = &self.input_sessions[self.input_sessions.len() - 1];

        // Both must have samples
        let first1 = session1.first_sample()?;
        let first2 = session2.first_sample()?;
        let last1 = session1.last_sample()?;
        let last2 = session2.last_sample()?;

        // Calculate initial distance between touches
        let dx_initial = first2.position.x - first1.position.x;
        let dy_initial = first2.position.y - first1.position.y;
        let initial_distance = (dx_initial * dx_initial + dy_initial * dy_initial).sqrt();

        // Calculate current distance
        let dx_current = last2.position.x - last1.position.x;
        let dy_current = last2.position.y - last1.position.y;
        let current_distance = (dx_current * dx_current + dy_current * dy_current).sqrt();

        // Avoid division by zero
        if initial_distance < 1.0 {
            return None;
        }

        // Calculate scale factor
        let scale = current_distance / initial_distance;

        // Check if scale change is significant (threshold from config)
        let scale_threshold = 1.0 + self.config.pinch_scale_threshold;
        if scale > 1.0 / scale_threshold && scale < scale_threshold {
            return None; // Change too small
        }

        // Calculate center point
        let center = LogicalPosition {
            x: (last1.position.x + last2.position.x) / 2.0,
            y: (last1.position.y + last2.position.y) / 2.0,
        };

        // Calculate duration
        let duration = last1.timestamp.duration_since(&first1.timestamp);
        let duration_ms = duration_to_millis(duration);

        Some(DetectedPinch {
            scale,
            center,
            initial_distance,
            current_distance,
            duration_ms,
        })
    }

    /// Detect rotation gesture (two-touch rotate)
    ///
    /// Returns Some if two touch points are rotating around center.
    /// Positive angle = clockwise, negative = counterclockwise.
    pub fn detect_rotation(&self) -> Option<DetectedRotation> {
        // Need at least two active sessions
        if self.input_sessions.len() < 2 {
            return None;
        }

        // Get last two sessions
        let session1 = &self.input_sessions[self.input_sessions.len() - 2];
        let session2 = &self.input_sessions[self.input_sessions.len() - 1];

        // Both must have samples
        let first1 = session1.first_sample()?;
        let first2 = session2.first_sample()?;
        let last1 = session1.last_sample()?;
        let last2 = session2.last_sample()?;

        // Calculate center (average of both touches)
        let center = LogicalPosition {
            x: (last1.position.x + last2.position.x) / 2.0,
            y: (last1.position.y + last2.position.y) / 2.0,
        };

        // Calculate initial angle between touches
        let dx_initial = first2.position.x - first1.position.x;
        let dy_initial = first2.position.y - first1.position.y;
        let initial_angle = dy_initial.atan2(dx_initial);

        // Calculate current angle
        let dx_current = last2.position.x - last1.position.x;
        let dy_current = last2.position.y - last1.position.y;
        let current_angle = dy_current.atan2(dx_current);

        // Calculate angle difference (normalized to -π to π)
        let mut angle_diff = current_angle - initial_angle;

        // Normalize angle to -π to π range
        const PI: f32 = core::f32::consts::PI;
        while angle_diff > PI {
            angle_diff -= 2.0 * PI;
        }
        while angle_diff < -PI {
            angle_diff += 2.0 * PI;
        }

        // Check if rotation is significant (threshold from config)
        if angle_diff.abs() < self.config.rotation_angle_threshold {
            return None;
        }

        // Calculate duration
        let duration = last1.timestamp.duration_since(&first1.timestamp);
        let duration_ms = duration_to_millis(duration);

        Some(DetectedRotation {
            angle_radians: angle_diff,
            center,
            duration_ms,
        })
    }

    /// Get the current active input session (if any)
    pub fn get_current_session(&self) -> Option<&InputSession> {
        self.input_sessions.last()
    }

    /// Get current mouse position from latest sample
    pub fn get_current_mouse_position(&self) -> Option<LogicalPosition> {
        self.get_current_session()
            .and_then(|s| s.last_sample())
            .map(|sample| sample.position)
    }

    /// Get the drag delta (current mouse position minus mouse-down position)
    /// from the current input session.
    ///
    /// Returns `None` if there is no active session or not enough samples.
    pub fn get_drag_delta(&self) -> Option<(f32, f32)> {
        let session = self.get_current_session()?;
        let first = session.first_sample()?;
        let last = session.last_sample()?;
        Some((
            last.position.x - first.position.x,
            last.position.y - first.position.y,
        ))
    }

    /// Get the drag delta in **screen-absolute** coordinates.
    ///
    /// Unlike `get_drag_delta()` which uses window-local coordinates (and therefore
    /// oscillates during window drags due to the window moving under the cursor),
    /// this method uses screen-absolute positions that are stable regardless of
    /// window movement.
    ///
    /// **Use this for window dragging (titlebar drag).**
    /// Use `get_drag_delta()` for in-window operations (node drag-and-drop, etc.).
    ///
    /// Returns `None` if there is no active session or not enough samples.
    pub fn get_drag_delta_screen(&self) -> Option<(f32, f32)> {
        let session = self.get_current_session()?;
        let first = session.first_sample()?;
        let last = session.last_sample()?;
        Some((
            last.screen_position.x - first.screen_position.x,
            last.screen_position.y - first.screen_position.y,
        ))
    }

    /// Get the **incremental** (frame-to-frame) drag delta in screen coordinates.
    ///
    /// Returns `(dx, dy)` where `dx = last_screen.x - previous_screen.x` and
    /// `dy = last_screen.y - previous_screen.y`.
    ///
    /// Unlike `get_drag_delta_screen()` which returns the *total* delta since drag
    /// start, this returns only the delta since the previous sample. This is used
    /// by `titlebar_drag` to apply position changes incrementally:
    ///
    /// ```text
    /// new_pos = current_window_pos + incremental_delta
    /// ```
    ///
    /// This approach is more robust than `initial_pos + total_delta` because it
    /// automatically handles external window position changes (DPI change, OS
    /// clamping, compositor resize) that would make `initial_pos` stale.
    ///
    /// Returns `None` if there is no active session or fewer than 2 samples.
    pub fn get_drag_delta_screen_incremental(&self) -> Option<(f32, f32)> {
        let session = self.get_current_session()?;
        let len = session.samples.len();
        if len < 2 {
            return None;
        }
        let prev = &session.samples[len - 2];
        let last = &session.samples[len - 1];
        Some((
            last.screen_position.x - prev.screen_position.x,
            last.screen_position.y - prev.screen_position.y,
        ))
    }

    /// Get the window position that was stored when the current input session
    /// started (i.e. on mouse-down).  Titlebar drag callbacks use this
    /// together with `get_drag_delta_screen()` to compute the new window position.
    pub fn get_window_position_at_session_start(&self) -> Option<azul_core::window::WindowPosition> {
        let session = self.get_current_session()?;
        Some(session.window_position_at_start)
    }

    // ========================================================================
    // UNIFIED DRAG CONTEXT API (NEW)
    // ========================================================================

    /// Get the active drag context (if any)
    pub fn get_drag_context(&self) -> Option<&DragContext> {
        self.active_drag.as_ref()
    }

    /// Get the active drag context mutably (if any)
    pub fn get_drag_context_mut(&mut self) -> Option<&mut DragContext> {
        self.active_drag.as_mut()
    }

    /// Activate a text selection drag
    pub fn activate_text_selection_drag(
        &mut self,
        dom_id: DomId,
        anchor_ifc_node: NodeId,
        start_mouse_position: LogicalPosition,
    ) {
        let session_id = self.current_session_id().unwrap_or(0);
        self.active_drag = Some(DragContext::text_selection(
            dom_id,
            anchor_ifc_node,
            start_mouse_position,
            session_id,
        ));
    }

    /// Activate a scrollbar thumb drag
    pub fn activate_scrollbar_drag(
        &mut self,
        scroll_container_node: NodeId,
        axis: ScrollbarAxis,
        start_mouse_position: LogicalPosition,
        start_scroll_offset: f32,
        track_length_px: f32,
        content_length_px: f32,
        viewport_length_px: f32,
    ) {
        let session_id = self.current_session_id().unwrap_or(0);
        self.active_drag = Some(DragContext::scrollbar_thumb(
            scroll_container_node,
            axis,
            start_mouse_position,
            start_scroll_offset,
            track_length_px,
            content_length_px,
            viewport_length_px,
            session_id,
        ));
    }

    /// Activate a node drag-and-drop
    pub fn activate_node_drag(
        &mut self,
        dom_id: DomId,
        node_id: NodeId,
        drag_data: DragData,
        _start_hit_test: Option<HitTest>,
    ) {
        if let Some(detected) = self.detect_drag() {
            self.active_drag = Some(DragContext::node_drag(
                dom_id,
                node_id,
                detected.start_position,
                drag_data,
                detected.session_id,
            ));
        }
    }

    /// Activate a window move drag (titlebar)
    pub fn activate_window_drag(
        &mut self,
        initial_window_position: WindowPosition,
        _start_hit_test: Option<HitTest>,
    ) {
        if let Some(detected) = self.detect_drag() {
            self.active_drag = Some(DragContext::window_move(
                detected.start_position,
                initial_window_position,
                detected.session_id,
            ));
        }
    }

    /// Start file drop from OS
    pub fn start_file_drop(&mut self, files: Vec<AzString>, position: LogicalPosition) {
        let session_id = self.current_session_id().unwrap_or(0);
        self.active_drag = Some(DragContext::file_drop(files, position, session_id));
    }

    /// Update positions for active drag (call on mouse move)
    pub fn update_active_drag_positions(&mut self, position: LogicalPosition) {
        if let Some(ref mut drag) = self.active_drag {
            drag.update_position(position);
        }
    }

    /// Update drop target for node or file drag
    pub fn update_drop_target(&mut self, target: Option<azul_core::dom::DomNodeId>) {
        if let Some(ref mut drag) = self.active_drag {
            match &mut drag.drag_type {
                ActiveDragType::Node(ref mut node_drag) => {
                    node_drag.current_drop_target = target.into();
                }
                ActiveDragType::FileDrop(ref mut file_drop) => {
                    file_drop.drop_target = target.into();
                }
                _ => {}
            }
        }
    }

    /// Update auto-scroll direction for text selection drag
    pub fn update_auto_scroll_direction(&mut self, direction: AutoScrollDirection) {
        if let Some(ref mut drag) = self.active_drag {
            if let Some(text_drag) = drag.as_text_selection_mut() {
                text_drag.auto_scroll_direction = direction;
            }
        }
    }

    /// End the current drag and return the context
    pub fn end_drag(&mut self) -> Option<DragContext> {
        self.active_drag.take()
    }

    /// Cancel the current drag
    pub fn cancel_drag(&mut self) {
        if let Some(ref mut drag) = self.active_drag {
            drag.cancelled = true;
        }
        self.active_drag = None;
    }

    // ========================================================================
    // QUERY METHODS
    // ========================================================================

    /// Check if any drag operation is in progress
    pub fn is_dragging(&self) -> bool {
        self.active_drag.is_some()
    }

    /// Check if a text selection drag is active
    pub fn is_text_selection_dragging(&self) -> bool {
        self.active_drag.as_ref().is_some_and(|d| d.is_text_selection())
    }

    /// Check if a scrollbar thumb drag is active
    pub fn is_scrollbar_dragging(&self) -> bool {
        self.active_drag.as_ref().is_some_and(|d| d.is_scrollbar_thumb())
    }

    /// Check if a node drag is active
    pub fn is_node_dragging_any(&self) -> bool {
        self.active_drag.as_ref().is_some_and(|d| d.is_node_drag())
    }

    /// Check if a node drag is active (alias for event determination)
    pub fn is_node_drag_active(&self) -> bool {
        self.is_node_dragging_any()
    }

    /// Check if a specific node is being dragged
    pub fn is_node_dragging(&self, dom_id: DomId, node_id: NodeId) -> bool {
        self.active_drag.as_ref().is_some_and(|d| {
            if let Some(node_drag) = d.as_node_drag() {
                node_drag.dom_id == dom_id && node_drag.node_id == node_id
            } else {
                false
            }
        })
    }

    /// Check if window drag is active
    pub fn is_window_dragging(&self) -> bool {
        self.active_drag.as_ref().is_some_and(|d| d.is_window_move())
    }

    /// Check if file drop is active
    pub fn is_file_dropping(&self) -> bool {
        self.active_drag.as_ref().is_some_and(|d| d.is_file_drop())
    }

    /// Get number of active input sessions
    pub fn session_count(&self) -> usize {
        self.input_sessions.len()
    }

    /// Get current session ID (if any)
    pub fn current_session_id(&self) -> Option<u64> {
        self.get_current_session().map(|s| s.session_id)
    }

    // ========================================================================
    // BACKWARDS COMPATIBILITY (DEPRECATED)
    // ========================================================================

    /// Get current node drag state (if any)
    /// DEPRECATED: Use `get_drag_context()` and check for `ActiveDragType::Node`
    pub fn get_node_drag(&self) -> Option<&NodeDrag> {
        self.active_drag.as_ref().and_then(|d| d.as_node_drag())
    }

    /// Get current window drag state (if any)
    /// DEPRECATED: Use `get_drag_context()` and check for `ActiveDragType::WindowMove`
    pub fn get_window_drag(&self) -> Option<&WindowMoveDrag> {
        self.active_drag.as_ref().and_then(|d| d.as_window_move())
    }

    /// Get current file drop state (if any)
    /// DEPRECATED: Use `get_drag_context()` and check for `ActiveDragType::FileDrop`
    pub fn get_file_drop(&self) -> Option<&FileDropDrag> {
        self.active_drag.as_ref().and_then(|d| d.as_file_drop())
    }

    /// End node drag (returns None - use end_drag() instead)
    /// DEPRECATED: Use `end_drag()` instead
    pub fn end_node_drag(&mut self) -> Option<DragContext> {
        if self.active_drag.as_ref().is_some_and(|d| d.is_node_drag()) {
            self.end_drag()
        } else {
            None
        }
    }

    /// End window drag (returns None - use end_drag() instead)
    /// DEPRECATED: Use `end_drag()` instead
    pub fn end_window_drag(&mut self) -> Option<DragContext> {
        if self.active_drag.as_ref().is_some_and(|d| d.is_window_move()) {
            self.end_drag()
        } else {
            None
        }
    }

    /// End file drop (returns None - use end_drag() instead)
    /// DEPRECATED: Use `end_drag()` instead
    pub fn end_file_drop(&mut self) -> Option<DragContext> {
        if self.active_drag.as_ref().is_some_and(|d| d.is_file_drop()) {
            self.end_drag()
        } else {
            None
        }
    }

    /// Cancel file drop
    /// DEPRECATED: Use `cancel_drag()` instead
    pub fn cancel_file_drop(&mut self) {
        if self.active_drag.as_ref().is_some_and(|d| d.is_file_drop()) {
            self.cancel_drag();
        }
    }

    // ========================================================================
    // WINDOW DRAG HELPER METHODS
    // ========================================================================

    /// Calculate window position delta from current drag state
    ///
    /// Returns (delta_x, delta_y) to apply to window position.
    /// Returns None if no window drag is active or drag hasn't moved.
    pub fn get_window_drag_delta(&self) -> Option<(i32, i32)> {
        let drag = self.active_drag.as_ref()?.as_window_move()?;

        let delta_x = drag.current_position.x - drag.start_position.x;
        let delta_y = drag.current_position.y - drag.start_position.y;

        match drag.initial_window_position {
            WindowPosition::Initialized(_initial_pos) => Some((delta_x as i32, delta_y as i32)),
            _ => None,
        }
    }

    /// Get the new window position based on current drag
    ///
    /// Returns the absolute window position to set.
    pub fn get_window_position_from_drag(&self) -> Option<WindowPosition> {
        let drag = self.active_drag.as_ref()?.as_window_move()?;

        let delta_x = drag.current_position.x - drag.start_position.x;
        let delta_y = drag.current_position.y - drag.start_position.y;

        match drag.initial_window_position {
            WindowPosition::Initialized(initial_pos) => {
                Some(WindowPosition::Initialized(PhysicalPositionI32::new(
                    initial_pos.x + delta_x as i32,
                    initial_pos.y + delta_y as i32,
                )))
            }
            _ => None,
        }
    }

    /// Calculate the new scroll offset for scrollbar thumb drag
    pub fn get_scrollbar_scroll_offset(&self) -> Option<f32> {
        self.active_drag.as_ref()?.calculate_scrollbar_scroll_offset()
    }

    /// Remap NodeIds in active drag context after DOM reconciliation.
    ///
    /// When the DOM is regenerated during an active drag, NodeIds can change.
    /// If a critical NodeId was removed, the drag is cancelled.
    pub fn remap_node_ids(
        &mut self,
        dom_id: azul_core::dom::DomId,
        node_id_map: &std::collections::BTreeMap<azul_core::id::NodeId, azul_core::id::NodeId>,
    ) {
        if let Some(ref mut drag) = self.active_drag {
            if !drag.remap_node_ids(dom_id, node_id_map) {
                // Critical node removed — cancel the drag
                drag.cancelled = true;
                self.active_drag = None;
            }
        }
    }
}