commonMain.androidx.compose.foundation.text.input.OutputTransformation.kt Maven / Gradle / Ivy

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/*
 * Copyright 2024 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.input

import androidx.compose.foundation.text.BasicTextField
import androidx.compose.runtime.Stable

/**
 * A function ([transformOutput]) that transforms the text presented to a user by a
 * [BasicTextField].
 */
@Stable
fun interface OutputTransformation {

    /**
     * Given a [TextFieldBuffer] that contains the contents of a [TextFieldState], modifies the
     * text. After this function returns, the contents of the buffer will be presented to the user
     * as the contents of the text field instead of the raw contents of the [TextFieldState].
     *
     * Use this function to change the visual and semantics representation of the text. For example,
     * a phone number field can format the raw input by adding parentheses and white spaces in
     * between characters.
     *
     * The result of this transformation is purely representational and does not affect the contents
     * of [TextFieldState].
     *
     * Selection and cursor positions are managed internally by [BasicTextField]. If there's a range
     * of inserted characters via this [OutputTransformation], selection or cursor never goes in
     * between these inserted characters.
     *
     * Note that this transformation is called every time a new text needs to be displayed. This
     * implies that the contents of [TextFieldBuffer] will always be what the [TextFieldState] holds
     * currently. All the changes made here are discarded after text is presented to the user.
     *
     * @sample androidx.compose.foundation.samples.BasicTextFieldOutputTransformationSample
     */
    fun TextFieldBuffer.transformOutput()
}