noctalia-shell/Modules/MainScreen/Backgrounds/ShapeCornerHelper.qml

pragma Singleton

import QtQuick
import QtQuick.Shapes
import Quickshell

/**
* ShapeCornerHelper - Utility singleton for shape corner calculations
*
* Uses 4-state per-corner system for flexible corner rendering:
* - State -1: No radius (flat/square corner)
* - State 0: Normal (inner curve)
* - State 1: Horizontal inversion (outer curve on X-axis)
* - State 2: Vertical inversion (outer curve on Y-axis)
*
* The key technique: Using PathArc direction control (Clockwise vs Counterclockwise)
* combined with multipliers to create both inner and outer corner curves.
*/
Singleton {
  id: root

  /**
  * Get X-axis multiplier for a corner state
  * State 1 (horizontal invert) returns -1, others return 1
  */
  function getMultX(cornerState) {
    return cornerState === 1 ? -1 : 1;
  }

  /**
  * Get Y-axis multiplier for a corner state
  * State 2 (vertical invert) returns -1, others return 1
  */
  function getMultY(cornerState) {
    return cornerState === 2 ? -1 : 1;
  }

  /**
  * Get PathArc direction for a corner based on its multipliers
  * Uses XOR logic: if X inverted differs from Y inverted, use Counterclockwise
  * This creates the outer curve effect for inverted corners
  */
  function getArcDirection(multX, multY) {
    return ((multX < 0) !== (multY < 0)) ? PathArc.Counterclockwise : PathArc.Clockwise;
  }

  /**
  * Convenience function to get arc direction directly from corner state
  */
  function getArcDirectionFromState(cornerState) {
    const multX = getMultX(cornerState);
    const multY = getMultY(cornerState);
    return getArcDirection(multX, multY);
  }

  /**
  * Get the "flattening" radius when shape dimensions are too small
  * Prevents visual artifacts when radius exceeds dimensions
  */
  function getFlattenedRadius(dimension, requestedRadius) {
    if (dimension < requestedRadius * 2) {
      return dimension / 2;
    }
    return requestedRadius;
  }

  /**
  * Check if a shape should use flattened corners
  * Returns true if width or height is too small for the requested radius
  */
  function shouldFlatten(width, height, radius) {
    return width < radius * 2 || height < radius * 2;
  }
}