android/graphics/text/Primitive.java

/*
 * 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.
 */

package android.graphics.text;

import android.annotation.NonNull;

// Based on the native implementation of Primitive in
// frameworks/base/core/jni/android_text_StaticLayout.cpp revision b808260
public class Primitive {
    public final @NonNull PrimitiveType type;
    public final int location;
    // The following fields don't make sense for all types.
    // Box and Glue have width only.
    // Penalty has both width and penalty.
    // Word_break has penalty only.
    public final float width;
    public final float penalty;

    /**
     * Use {@code PrimitiveType#getNewPrimitive()}
     */
    private Primitive(@NonNull PrimitiveType type, int location, float width, float penalty) {
        this.type = type;
        this.location = location;
        this.width = width;
        this.penalty = penalty;
    }

    public static enum PrimitiveType {
        /**
         * Something with a constant width that is to be typeset - like a character.
         */
        BOX,
        /**
         * Blank space with fixed width.
         */
        GLUE,
        /**
         * Aesthetic cost indicating how desirable breaking at this point will be. A penalty of
         * {@link #PENALTY_INFINITY} means a forced non-break, whereas a penalty of negative
         * {@code #PENALTY_INFINITY} means a forced break.
         * <p/>
         * Currently, it only stores penalty with values 0 or -infinity.
         */
        PENALTY,
        /**
         * For tabs - variable width space.
         */
        VARIABLE,
        /**
         * Possible breakpoints within a word. Think of this as a high cost {@link #PENALTY}.
         */
        WORD_BREAK;

        public Primitive getNewPrimitive(int location) {
            assert this == VARIABLE;
            return new Primitive(this, location, 0f, 0f);
        }

        public Primitive getNewPrimitive(int location, float value) {
            assert this == BOX || this == GLUE || this == WORD_BREAK;
            if (this == BOX || this == GLUE) {
                return new Primitive(this, location, value, 0f);
            } else {
                return new Primitive(this, location, 0f, value);
            }
        }

        public Primitive getNewPrimitive(int location, float width, float penalty) {
            assert this == PENALTY;
            return new Primitive(this, location, width, penalty);
        }

        // forced non-break, negative infinity is forced break.
        public static final float PENALTY_INFINITY = 1e7f;
    }
}