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

Go to download

Show more of this group Show more artifacts with this name
Show all versions of foundation-desktop Show documentation

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

The newest version!

/*
 * Copyright 2021 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.runtime.Immutable
import androidx.compose.ui.text.TextRange
import androidx.compose.ui.text.style.ResolvedTextDirection

/** Information about the current Selection. */
@Immutable
internal data class Selection(
    /** Information about the start of the selection. */
    val start: AnchorInfo,

    /** Information about the end of the selection. */
    val end: AnchorInfo,
    /**
     * The flag to show that the selection handles are dragged across each other. After selection is
     * initialized, if user drags one handle to cross the other handle, this is true, otherwise it's
     * false.
     */
    // If selection happens in single widget, checking [TextRange.start] > [TextRange.end] is
    // enough.
    // But when selection happens across multiple widgets, this value needs more complicated
    // calculation. To avoid repeated calculation, making it as a flag is cheaper.
    val handlesCrossed: Boolean = false
) {
    /** Contains information about an anchor (start/end) of selection. */
    @Immutable
    internal data class AnchorInfo(
        /** Text direction of the character in selection edge. */
        val direction: ResolvedTextDirection,

        /**
         * Character offset for the selection edge. This offset is within individual child text
         * composable.
         */
        val offset: Int,

        /** The id of the [Selectable] which contains this [Selection] Anchor. */
        val selectableId: Long
    )

    fun merge(other: Selection?): Selection {
        if (other == null) return this

        val selection = this

        return if (handlesCrossed || other.handlesCrossed) {
            Selection(
                start = if (other.handlesCrossed) other.start else other.end,
                end = if (handlesCrossed) end else start,
                handlesCrossed = true
            )
        } else {
            selection.copy(end = other.end)
        }
    }

    /** Returns the selection offset information as a [TextRange] */
    fun toTextRange(): TextRange {
        return TextRange(start.offset, end.offset)
    }
}