commonMain.androidx.compose.foundation.text.selection.TextSelectionDelegate.kt Maven / Gradle / Ivy

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Higher level abstractions of the Compose UI primitives. This library is design system agnostic, providing the high-level building blocks for both application and design-system developers

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/*
 * 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.foundation.text.selection

import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.text.TextLayoutResult
import kotlin.math.max

/**
 * This method returns the graphical position where the selection handle should be based on the
 * offset and other information.
 *
 * @param textLayoutResult a result of the text layout.
 * @param offset character offset to be calculated
 * @param isStart true if called for selection start handle
 * @param areHandlesCrossed true if the selection handles are crossed
 *
 * @return the graphical position where the selection handle should be.
 */
internal fun getSelectionHandleCoordinates(
    textLayoutResult: TextLayoutResult,
    offset: Int,
    isStart: Boolean,
    areHandlesCrossed: Boolean
): Offset {
    val line = textLayoutResult.getLineForOffset(offset)

    // This happens if maxLines is set but the offset is on a line >= maxLines.
    if (line >= textLayoutResult.lineCount) return Offset.Unspecified

    val x = textLayoutResult.getHorizontalPosition(offset, isStart, areHandlesCrossed)
    val y = textLayoutResult.getLineBottom(line)
    return Offset(x, y)
}

internal fun TextLayoutResult.getHorizontalPosition(
    offset: Int,
    isStart: Boolean,
    areHandlesCrossed: Boolean
): Float {
    val offsetToCheck =
        if (isStart && !areHandlesCrossed || !isStart && areHandlesCrossed) offset
        else max(offset - 1, 0)
    val bidiRunDirection = getBidiRunDirection(offsetToCheck)
    val paragraphDirection = getParagraphDirection(offset)

    return getHorizontalPosition(
        offset = offset,
        usePrimaryDirection = bidiRunDirection == paragraphDirection
    )
}