CustomEmojiHelper: rewrite to Kotlin (#1787)

* CustomEmojiHelper: rewrite to Kotlin

* CustomEmojiHelper: PR fixes

app/src/main/java/com/keylesspalace/tusky/util/CustomEmojiHelper.kt

@@ -0,0 +1,112 @@
+/* Copyright 2020 Tusky Contributors
+ * 
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>. */
+
+@file:JvmName("CustomEmojiHelper")
+package com.keylesspalace.tusky.util
+
+import android.graphics.Bitmap
+import android.graphics.Canvas
+import android.graphics.Paint
+import android.graphics.drawable.BitmapDrawable
+import android.graphics.drawable.Drawable
+import android.text.SpannableStringBuilder
+import android.text.style.ReplacementSpan
+import android.view.View
+
+import com.bumptech.glide.Glide
+import com.bumptech.glide.request.target.CustomTarget
+import com.bumptech.glide.request.target.Target
+import com.bumptech.glide.request.transition.Transition
+import com.keylesspalace.tusky.entity.Emoji
+
+import java.lang.ref.WeakReference
+import java.util.regex.Pattern
+
+/**
+ * replaces emoji shortcodes in a text with EmojiSpans
+ * @param text the text containing custom emojis
+ * @param emojis a list of the custom emojis (nullable for backward compatibility with old mastodon instances)
+ * @param view a reference to the a view the emojis will be shown in (should be the TextView, but parents of the TextView are also acceptable)
+ * @return the text with the shortcodes replaced by EmojiSpans
+*/
+fun CharSequence.emojify(emojis: List<Emoji>?, view: View) : CharSequence {
+    if(emojis.isNullOrEmpty())
+        return this
+
+    val builder = SpannableStringBuilder.valueOf(this)
+
+    emojis.forEach { (shortcode, url) ->
+        val matcher = Pattern.compile(":$shortcode:", Pattern.LITERAL)
+            .matcher(this)
+
+        while(matcher.find()) {
+            val span = EmojiSpan(WeakReference(view))
+
+            builder.setSpan(span, matcher.start(), matcher.end(), 0);
+            Glide.with(view)
+                .asBitmap()
+                .load(url)
+                .into(span.getTarget())
+        }
+    }
+    return builder
+}
+
+class EmojiSpan(val viewWeakReference: WeakReference<View>) : ReplacementSpan() {
+    var imageDrawable: Drawable? = null
+    
+    override fun getSize(paint: Paint, text: CharSequence, start: Int, end: Int, fm: Paint.FontMetricsInt?) : Int {
+        if (fm != null) {
+            /* update FontMetricsInt or otherwise span does not get drawn when
+             * it covers the whole text */
+            val metrics = paint.fontMetricsInt
+            fm.top = metrics.top
+            fm.ascent = metrics.ascent
+            fm.descent = metrics.descent
+            fm.bottom = metrics.bottom
+        }
+        
+        return (paint.textSize * 1.2).toInt()
+    }
+    
+    override fun draw(canvas: Canvas, text: CharSequence, start: Int, end: Int, x: Float, top: Int, y: Int, bottom: Int, paint: Paint) {
+        imageDrawable?.let { drawable ->
+            canvas.save()
+
+            val emojiSize = (paint.textSize * 1.1).toInt()
+            drawable.setBounds(0, 0, emojiSize, emojiSize)
+
+            var transY = bottom - drawable.bounds.bottom
+            transY -= paint.fontMetricsInt.descent / 2;
+
+            canvas.translate(x, transY.toFloat())
+            drawable.draw(canvas)
+            canvas.restore()
+        }
+    }
+    
+    fun getTarget(): Target<Bitmap> {
+        return object : CustomTarget<Bitmap>() {
+            override fun onResourceReady(resource: Bitmap, transition: Transition<in Bitmap>?) {
+                viewWeakReference.get()?.let { view ->
+                    imageDrawable = BitmapDrawable(view.context.resources, resource)
+                    view.invalidate()
+                }
+            }
+            
+            override fun onLoadCleared(placeholder: Drawable?) {}
+        }
+    }
+}