xref: /frameworks/support/core/ktx/src/main/java/androidx/core/graphics/Path.kt

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

@file:Suppress("NOTHING_TO_INLINE")

package androidx.graphics

import android.graphics.Path
import android.graphics.PointF
import android.support.annotation.RequiresApi

/**
 * A [PathSegment] is a line segment that represents an approximate fraction
 * of a [Path] after [flattening][Path.flatten].
 *
 * @param start The start point of the line segment
 * @param startFraction Fraction along the length of the path that the start point resides
 * @param start The end point of the line segment
 * @param startFraction Fraction along the length of the path that the end point resides
 */
data class PathSegment(
        val start: PointF,
        val startFraction: Float,
        val end: PointF,
        val endFraction: Float)

/**
 * Flattens (or approximate) the [Path] with a series of line segments.
 *
 * @param error The acceptable error for a line on the Path. Typically this would be
 *              0.5 so that the error is less than half a pixel. This value must be
 *              positive and is set to 0.5 by default.
 *
 * @see Path.approximate
 */
@RequiresApi(26)
fun Path.flatten(error: Float = 0.5f): Iterable<PathSegment> {
    val pathData = approximate(error)
    val pointCount = pathData.size / 3
    val segments = ArrayList<PathSegment>(pointCount / 2)
    for (i in 1 until pointCount) {
        val index = i * 3
        val prevIndex = (i - 1) * 3

        val d = pathData[index]
        val x = pathData[index + 1]
        val y = pathData[index + 2]

        val pd = pathData[prevIndex]
        val px = pathData[prevIndex + 1]
        val py = pathData[prevIndex + 2]

        if (d != pd && (x != py || y != py)) {
            segments.add(PathSegment(PointF(px, py), pd, PointF(x, y), d))
        }
    }
    return segments
}

/**
 * Returns the union of two paths as a new [Path].
 */
@RequiresApi(19)
inline operator fun Path.plus(p: Path): Path {
    return Path(this).apply {
        op(p, Path.Op.UNION)
    }
}

/**
 * Returns the difference of two paths as a new [Path].
 */
@RequiresApi(19)
inline operator fun Path.minus(p: Path): Path {
    return Path(this).apply {
        op(p, Path.Op.DIFFERENCE)
    }
}

/**
 * Returns the union of two paths as a new [Path].
 */
@RequiresApi(19)
inline infix fun Path.and(p: Path) = this + p

/**
 * Returns the intersection of two paths as a new [Path].
 * If the paths do not intersect, returns an empty path.
 */
@RequiresApi(19)
inline infix fun Path.or(p: Path): Path {
    return Path().apply {
        op(this@or, p, Path.Op.INTERSECT)
    }
}

/**
 * Returns the union minus the intersection of two paths as a new [Path].
 */
@RequiresApi(19)
inline infix fun Path.xor(p: Path): Path {
    return Path(this).apply {
        op(p, Path.Op.XOR)
    }
}