MaxLengthFilter.kt
/*
* Copyright 2023 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.text2.input
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.runtime.Stable
/**
* Returns [TextEditFilter] that rejects input which causes the total length of the text field to be
* more than [maxLength] characters.
*
* @see maxLengthInCodepoints
*/
@ExperimentalFoundationApi
@Stable
fun TextEditFilter.Companion.maxLengthInChars(maxLength: Int): TextEditFilter =
MaxLengthFilter(maxLength, inCodepoints = false)
/**
* Returns a [TextEditFilter] that rejects input which causes the total length of the text field to
* be more than [maxLength] codepoints.
*
* @see maxLengthInChars
*/
@ExperimentalFoundationApi
@Stable
fun TextEditFilter.Companion.maxLengthInCodepoints(maxLength: Int): TextEditFilter =
MaxLengthFilter(maxLength, inCodepoints = true)
// This is a very naive implementation for now, not intended to be production-ready.
@OptIn(ExperimentalFoundationApi::class)
private data class MaxLengthFilter(
private val maxLength: Int,
private val inCodepoints: Boolean
) : TextEditFilter {
init {
require(maxLength >= 0) { "maxLength must be at least zero, was $maxLength" }
}
override fun filter(
originalValue: TextFieldCharSequence,
valueWithChanges: TextFieldBufferWithSelection
) {
val newLength =
if (inCodepoints) valueWithChanges.codepointLength else valueWithChanges.length
if (newLength > maxLength) {
valueWithChanges.revertAllChanges()
}
}
override fun toString(): String {
val name = if (inCodepoints) "maxLengthInCodepoints" else "maxLengthInChars"
return "TextEditFilter.$name(maxLength=$maxLength)"
}
}