TextLayoutHelper.kt

/*
 * Copyright 2019 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 androidx.compose.ui.text

import androidx.compose.ui.text.font.Font
import androidx.compose.ui.text.style.TextOverflow
import androidx.compose.ui.unit.Constraints
import androidx.compose.ui.unit.Density
import androidx.compose.ui.unit.LayoutDirection

/**
 * Returns true if the this TextLayoutResult can be reused for given parameters.
 *
 * @param text a text to be used for computing text layout.
 * @param style a text style to be used for computing text layout.
 * @param maxLines a maximum number of lines to be used for computing text layout.
 * @param softWrap whether doing softwrap or not to be used for computing text layout.
 * @param overflow an overflow type to be used for computing text layout.
 * @param density a density to be used for computing text layout.
 * @param layoutDirection a layout direction to be used for computing text layout.
 * @param resourceLoader a resource loader to be used for computing text layout.
 * @param constraints a constraint to be used for computing text layout.
 */
internal fun TextLayoutResult.canReuse(
    text: AnnotatedString,
    style: TextStyle,
    maxLines: Int,
    softWrap: Boolean,
    overflow: TextOverflow,
    density: Density,
    layoutDirection: LayoutDirection,
    resourceLoader: Font.ResourceLoader,
    constraints: Constraints
): Boolean {

    // Check if this is created from the same parameter.
    val layoutInput = this.layoutInput
    if (!(layoutInput.text == text &&
                layoutInput.style.canReuseLayout(style) &&
                layoutInput.maxLines == maxLines &&
                layoutInput.softWrap == softWrap &&
                layoutInput.overflow == overflow &&
                layoutInput.density == density &&
                layoutInput.layoutDirection == layoutDirection &&
                layoutInput.resourceLoader == resourceLoader)) {
        return false
    }

    // Check the given constraints can produces the same result.
    if (constraints.minWidth != layoutInput.constraints.minWidth) return false

    if (!(softWrap || overflow == TextOverflow.Ellipsis)) {
        // If width does not mattter, we can result the same layout.
        return true
    }
    return constraints.maxWidth == layoutInput.constraints.maxWidth
}

/**
 * Returns true if text layout created with this TextStyle can be reused for the [other] TextStyle.
 */
internal fun TextStyle.canReuseLayout(other: TextStyle): Boolean {
    return fontSize == other.fontSize &&
            fontWeight == other.fontWeight &&
            fontStyle == other.fontStyle &&
            fontSynthesis == other.fontSynthesis &&
            fontFamily == other.fontFamily &&
            fontFeatureSettings == other.fontFeatureSettings &&
            letterSpacing == other.letterSpacing &&
            baselineShift == other.baselineShift &&
            textGeometricTransform == other.textGeometricTransform &&
            localeList == other.localeList &&
            background == other.background &&
            textAlign == other.textAlign &&
            textDirection == other.textDirection &&
            lineHeight == other.lineHeight &&
            textIndent == other.textIndent
}