112 lines
4.6 KiB
Kotlin
112 lines
4.6 KiB
Kotlin
/* Copyright 2019 Tusky contributors
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*
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* This file is a part of Tusky.
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*
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* This program is free software; you can redistribute it and/or modify it under the terms of the
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* GNU General Public License as published by the Free Software Foundation; either version 3 of the
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* License, or (at your option) any later version.
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*
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* Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
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* the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
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* Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along with Tusky; if not,
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* see <http://www.gnu.org/licenses>. */
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package com.keylesspalace.tusky.util
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import android.text.InputFilter
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import android.text.SpannableStringBuilder
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import android.text.Spanned
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/**
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* Defines how many characters to extend beyond the limit to cut at the end of the word on the
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* boundary of it rather than cutting at the word preceding that one.
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*/
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private const val RUNWAY = 10
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/**
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* Default for maximum status length on Mastodon and default collapsing length on Pleroma.
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*/
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private const val LENGTH_DEFAULT = 500
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/**
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* Calculates if it's worth trimming the message at a specific limit or if the content that will
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* be hidden will not be enough to justify the operation.
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*
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* @param message The message to trim.
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* @return Whether the message should be trimmed or not.
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*/
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fun shouldTrimStatus(message: Spanned): Boolean {
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return message.isNotEmpty() && LENGTH_DEFAULT.toFloat() / message.length < 0.75
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}
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/**
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* A customized version of {@link android.text.InputFilter.LengthFilter} which allows smarter
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* constraints and adds better visuals such as:
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* <ul>
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* <li>Ellipsis at the end of the constrained text to show continuation.</li>
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* <li>Trimming of invisible characters (new lines, spaces, etc.) from the constrained text.</li>
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* <li>Constraints end at the end of the last "word", before a whitespace.</li>
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* <li>Expansion of the limit by up to 10 characters to facilitate the previous constraint.</li>
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* <li>Constraints are not applied if the percentage of hidden content is too small.</li>
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* </ul>
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*/
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object SmartLengthInputFilter : InputFilter {
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/** {@inheritDoc} */
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override fun filter(source: CharSequence, start: Int, end: Int, dest: Spanned, dstart: Int, dend: Int): CharSequence? {
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// Code originally imported from InputFilter.LengthFilter but heavily customized and converted to Kotlin.
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// https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/text/InputFilter.java#175
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val sourceLength = source.length
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var keep = LENGTH_DEFAULT - (dest.length - (dend - dstart))
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if (keep <= 0) return ""
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if (keep >= end - start) return null // Keep original
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keep += start
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// Skip trimming if the ratio doesn't warrant it
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if (keep.toDouble() / sourceLength > 0.75) return null
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// Enable trimming at the end of the closest word if possible
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if (source[keep].isLetterOrDigit()) {
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var boundary: Int
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// Android N+ offer a clone of the ICU APIs in Java for better internationalization and
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// unicode support. Using the ICU version of BreakIterator grants better support for
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// those without having to add the ICU4J library at a minimum Api trade-off.
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if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.N) {
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val iterator = android.icu.text.BreakIterator.getWordInstance()
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iterator.setText(source.toString())
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boundary = iterator.following(keep)
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if (keep - boundary > RUNWAY) boundary = iterator.preceding(keep)
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} else {
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val iterator = java.text.BreakIterator.getWordInstance()
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iterator.setText(source.toString())
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boundary = iterator.following(keep)
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if (keep - boundary > RUNWAY) boundary = iterator.preceding(keep)
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}
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keep = boundary
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} else {
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// If no runway is allowed simply remove whitespace if present
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while (source[keep - 1].isWhitespace()) {
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--keep
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if (keep == start) return ""
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}
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}
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if (source[keep - 1].isHighSurrogate()) {
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--keep
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if (keep == start) return ""
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}
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return if (source is Spanned) {
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SpannableStringBuilder(source, start, keep).append("…")
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} else {
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"${source.subSequence(start, keep)}…"
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}
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}
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}
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