commonMain.androidx.compose.foundation.text.HeightInLinesModifier.kt Maven / Gradle / Ivy

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/*
 * Copyright 2020 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.foundation.text

import androidx.compose.foundation.internal.requirePrecondition
import androidx.compose.foundation.layout.heightIn
import androidx.compose.runtime.getValue
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.composed
import androidx.compose.ui.platform.LocalDensity
import androidx.compose.ui.platform.LocalFontFamilyResolver
import androidx.compose.ui.platform.LocalLayoutDirection
import androidx.compose.ui.platform.debugInspectorInfo
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.text.font.FontStyle
import androidx.compose.ui.text.font.FontSynthesis
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.resolveDefaults
import androidx.compose.ui.unit.Dp

/**
 * The default minimum height in terms of minimum number of visible lines.
 *
 * Should not be used in public API and samples unless it's public, too.
 */
internal const val DefaultMinLines = 1

/**
 * Constraint the height of the TextField or BasicText so that it vertically occupies at least
 * [minLines] number of lines and at most [maxLines] number of lines. BasicText should not use this
 * function for calculating maxLines constraints since MultiParagraph computation already handles
 * that.
 */
internal fun Modifier.heightInLines(
    textStyle: TextStyle,
    minLines: Int = DefaultMinLines,
    maxLines: Int = Int.MAX_VALUE
) =
    composed(
        inspectorInfo =
            debugInspectorInfo {
                name = "heightInLines"
                properties["minLines"] = minLines
                properties["maxLines"] = maxLines
                properties["textStyle"] = textStyle
            }
    ) {
        validateMinMaxLines(minLines, maxLines)
        if (minLines == DefaultMinLines && maxLines == Int.MAX_VALUE) return@composed Modifier

        val density = LocalDensity.current
        val fontFamilyResolver = LocalFontFamilyResolver.current
        val layoutDirection = LocalLayoutDirection.current

        // Difference between the height of two lines paragraph and one line paragraph gives us
        // an approximation of height of one line
        val resolvedStyle =
            remember(textStyle, layoutDirection) { resolveDefaults(textStyle, layoutDirection) }
        val typeface by
            remember(fontFamilyResolver, resolvedStyle) {
                fontFamilyResolver.resolve(
                    resolvedStyle.fontFamily,
                    resolvedStyle.fontWeight ?: FontWeight.Normal,
                    resolvedStyle.fontStyle ?: FontStyle.Normal,
                    resolvedStyle.fontSynthesis ?: FontSynthesis.All
                )
            }

        val firstLineHeight =
            remember(density, fontFamilyResolver, textStyle, layoutDirection, typeface) {
                computeSizeForDefaultText(
                        style = resolvedStyle,
                        density = density,
                        fontFamilyResolver = fontFamilyResolver,
                        text = EmptyTextReplacement,
                        maxLines = 1
                    )
                    .height
            }

        val firstTwoLinesHeight =
            remember(density, fontFamilyResolver, textStyle, layoutDirection, typeface) {
                val twoLines = EmptyTextReplacement + "\n" + EmptyTextReplacement
                computeSizeForDefaultText(
                        style = resolvedStyle,
                        density = density,
                        fontFamilyResolver = fontFamilyResolver,
                        text = twoLines,
                        maxLines = 2
                    )
                    .height
            }
        val lineHeight = firstTwoLinesHeight - firstLineHeight
        val precomputedMinLinesHeight =
            if (minLines == DefaultMinLines) null else firstLineHeight + lineHeight * (minLines - 1)
        val precomputedMaxLinesHeight =
            if (maxLines == Int.MAX_VALUE) null else firstLineHeight + lineHeight * (maxLines - 1)

        with(density) {
            Modifier.heightIn(
                min = precomputedMinLinesHeight?.toDp() ?: Dp.Unspecified,
                max = precomputedMaxLinesHeight?.toDp() ?: Dp.Unspecified
            )
        }
    }

internal fun validateMinMaxLines(minLines: Int, maxLines: Int) {
    requirePrecondition(minLines > 0 && maxLines > 0) {
        "both minLines $minLines and maxLines $maxLines must be greater than zero"
    }
    requirePrecondition(minLines <= maxLines) {
        "minLines $minLines must be less than or equal to maxLines $maxLines"
    }
}