android/graphics/Insets.java

/*
 * Copyright (C) 2006 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.
 */

package android.graphics;

import android.annotation.NonNull;
import android.annotation.Nullable;
import android.os.Parcel;
import android.os.Parcelable;

/**
 * An Insets instance holds four integer offsets which describe changes to the four
 * edges of a Rectangle. By convention, positive values move edges towards the
 * centre of the rectangle.
 * <p>
 * Insets are immutable so may be treated as values.
 *
 */
public final class Insets implements Parcelable {
    public static final @NonNull Insets NONE = new Insets(0, 0, 0, 0);

    public final int left;
    public final int top;
    public final int right;
    public final int bottom;

    private Insets(int left, int top, int right, int bottom) {
        this.left = left;
        this.top = top;
        this.right = right;
        this.bottom = bottom;
    }

    // Factory methods

    /**
     * Return an Insets instance with the appropriate values.
     *
     * @param left the left inset
     * @param top the top inset
     * @param right the right inset
     * @param bottom the bottom inset
     *
     * @return Insets instance with the appropriate values
     */
    public static @NonNull Insets of(int left, int top, int right, int bottom) {
        if (left == 0 && top == 0 && right == 0 && bottom == 0) {
            return NONE;
        }
        return new Insets(left, top, right, bottom);
    }

    /**
     * Return an Insets instance with the appropriate values.
     *
     * @param r the rectangle from which to take the values
     *
     * @return an Insets instance with the appropriate values
     */
    public static @NonNull Insets of(@Nullable Rect r) {
        return (r == null) ? NONE : of(r.left, r.top, r.right, r.bottom);
    }

    /**
     * Returns a Rect instance with the appropriate values.
     *
     * @hide
     */
    public @NonNull Rect toRect() {
        return new Rect(left, top, right, bottom);
    }

    /**
     * Add two Insets.
     *
     * @param a The first Insets to add.
     * @param b The second Insets to add.
     * @return a + b, i. e. all insets on every side are added together.
     */
    public static @NonNull Insets add(@NonNull Insets a, @NonNull Insets b) {
        return Insets.of(a.left + b.left, a.top + b.top, a.right + b.right, a.bottom + b.bottom);
    }

    /**
     * Subtract two Insets.
     *
     * @param a The minuend.
     * @param b The subtrahend.
     * @return a - b, i. e. all insets on every side are subtracted from each other.
     */
    public static @NonNull Insets subtract(@NonNull Insets a, @NonNull Insets b) {
        return Insets.of(a.left - b.left, a.top - b.top, a.right - b.right, a.bottom - b.bottom);
    }

    /**
     * Retrieves the maximum of two Insets.
     *
     * @param a The first Insets.
     * @param b The second Insets.
     * @return max(a, b), i. e. the larger of every inset on every side is taken for the result.
     */
    public static @NonNull Insets max(@NonNull Insets a, @NonNull Insets b) {
        return Insets.of(Math.max(a.left, b.left), Math.max(a.top, b.top),
                Math.max(a.right, b.right), Math.max(a.bottom, b.bottom));
    }

    /**
     * Retrieves the minimum of two Insets.
     *
     * @param a The first Insets.
     * @param b The second Insets.
     * @return min(a, b), i. e. the smaller of every inset on every side is taken for the result.
     */
    public static @NonNull Insets min(@NonNull Insets a, @NonNull Insets b) {
        return Insets.of(Math.min(a.left, b.left), Math.min(a.top, b.top),
                Math.min(a.right, b.right), Math.min(a.bottom, b.bottom));
    }

    /**
     * Two Insets instances are equal iff they belong to the same class and their fields are
     * pairwise equal.
     *
     * @param o the object to compare this instance with.
     *
     * @return true iff this object is equal {@code o}
     */
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Insets insets = (Insets) o;

        if (bottom != insets.bottom) return false;
        if (left != insets.left) return false;
        if (right != insets.right) return false;
        if (top != insets.top) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = left;
        result = 31 * result + top;
        result = 31 * result + right;
        result = 31 * result + bottom;
        return result;
    }

    @Override
    public String toString() {
        return "Insets{" +
                "left=" + left +
                ", top=" + top +
                ", right=" + right +
                ", bottom=" + bottom +
                '}';
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel out, int flags) {
        out.writeInt(left);
        out.writeInt(top);
        out.writeInt(right);
        out.writeInt(bottom);
    }

    public static final @android.annotation.NonNull Parcelable.Creator<Insets> CREATOR = new Parcelable.Creator<Insets>() {
        @Override
        public Insets createFromParcel(Parcel in) {
            return new Insets(in.readInt(), in.readInt(), in.readInt(), in.readInt());
        }

        @Override
        public Insets[] newArray(int size) {
            return new Insets[size];
        }
    };
}