Reduce hardcoded special case in EmojiModifier

app/src/main/java/org/fcitx/fcitx5/android/input/picker/PickerPagesAdapter.kt

@@ -47,7 +47,7 @@ class PickerPagesAdapter(
             val list = if (textPaint != null) {
                 arr.filter { textPaint.hasGlyph(it) }
             } else {
-                arr.toList()
+                arr.asList()
             }
             val chunks = list.chunked(density.pageSize)
             categories.add(cat to IntRange(pages.size, pages.size + chunks.size - 1))

app/src/main/java/org/fcitx/fcitx5/android/input/popup/EmojiModifier.kt

@@ -5,15 +5,16 @@
 
 package org.fcitx.fcitx5.android.input.popup
 
+import android.annotation.SuppressLint
 import android.icu.lang.UCharacter
 import android.icu.lang.UProperty
+import android.icu.text.UnicodeSet
 import android.os.Build
 import android.text.TextPaint
 import androidx.annotation.RequiresApi
 import org.fcitx.fcitx5.android.R
 import org.fcitx.fcitx5.android.data.prefs.AppPrefs
 import org.fcitx.fcitx5.android.data.prefs.ManagedPreferenceEnum
-import org.fcitx.fcitx5.android.utils.includes
 
 object EmojiModifier {
 
@@ -29,16 +30,12 @@ object EmojiModifier {
     /**
      * **Special Case 1:** Drop `U+FE0F` (Variation Selector-16) when combining with skin tone
      */
-    private val SpecialCase1 = intArrayOf(
+    @RequiresApi(Build.VERSION_CODES.P)
-        0x261D,  // ☝️
+    private fun shouldSkipVariationSelector16(ch: Int): Boolean {
-        0x26F9,  // ⛹️
+        return UCharacter.hasBinaryProperty(ch, UProperty.EMOJI_MODIFIER_BASE)
-        0x270C,  // ✌️
+                && !UCharacter.hasBinaryProperty(ch, UProperty.EMOJI_PRESENTATION)
-        0x1F3CB, // 🏋️
+    }
-        0x1F3CC, // 🏌️
+
-        0x1F574, // 🕴️
-        0x1F575, // 🕵️
-        0x1F590, // 🖐️
-    )
     private const val VariationSelector16 = 0xFE0F
 
     /**
@@ -56,7 +53,7 @@ object EmojiModifier {
     }
 
     private fun isModifiable(modifiable: BooleanArray): Boolean {
-        val sum = modifiable.sumOf { if (it) 1 else 0 }
+        val sum = modifiable.count { it }
         // bail if too crowded
         // eg. https://emojipedia.org/family-man-medium-light-skin-tone-woman-medium-light-skin-tone-girl-medium-light-skin-tone-boy-medium-light-skin-tone
         return sum == 1 || sum == 2
@@ -75,40 +72,59 @@ object EmojiModifier {
         return codePoints to modifiable
     }
 
+    @RequiresApi(Build.VERSION_CODES.P)
     private fun buildEmoji(codePoints: IntArray, modifiable: BooleanArray, tone: SkinTone): String {
         return buildString {
-            for (i in 0..<codePoints.size) {
+            var i = 0
-                // skip U+FE0F if the preceding character is special
+            while (i < codePoints.size) {
-                if (i > 0 && codePoints[i] == VariationSelector16 &&
-                    SpecialCase1.includes(codePoints[i - 1]) &&
-                    tone != SkinTone.Default
-                ) continue
                 appendCodePoint(codePoints[i])
                 if (modifiable[i]) {
                     append(tone.value)
+                    if (tone != SkinTone.Default &&
+                        codePoints.getOrNull(i + 1) == VariationSelector16 &&
+                        shouldSkipVariationSelector16(codePoints[i])
+                    ) i++
                 }
+                i++
             }
         }
     }
 
-    private val DefaultTextPaint = TextPaint()
+    private val DefaultTextPaint by lazy {
+        TextPaint()
+    }
+
+    private val RGIEmojiSet by lazy {
+        @SuppressLint("NewApi")
+        UnicodeSet("[:RGI_Emoji:]").freeze()
+    }
+
+    private fun isValidEmoji(emoji: String): Boolean {
+        // UProperty.RGI_EMOJI is available on 34+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.UPSIDE_DOWN_CAKE) {
+            if (!RGIEmojiSet.contains(emoji)) return false
+        }
+        return DefaultTextPaint.hasGlyph(emoji)
+    }
 
     fun getPreferredTone(emoji: String): String {
         if (!isSupported()) return emoji
         val (codePoints, modifiable) = getCodePoints(emoji)
-        if (!isModifiable(modifiable)) return emoji
+        val tone = defaultSkinTone
-        val candidate = buildEmoji(codePoints, modifiable, defaultSkinTone)
+        if (tone == SkinTone.Default || !isModifiable(modifiable)) return emoji
-        return if (DefaultTextPaint.hasGlyph(candidate)) candidate else emoji
+        val candidate = buildEmoji(codePoints, modifiable, tone)
+        return if (isValidEmoji(candidate)) candidate else emoji
     }
 
     fun produceSkinTones(emoji: String): Array<String>? {
         if (!isSupported()) return null
         val (codePoints, modifiable) = getCodePoints(emoji)
+        val tone = defaultSkinTone
         if (!isModifiable(modifiable)) return null
         val candidates = SkinTone.entries
-            .filter { it != defaultSkinTone }
+            .filter { it != tone }
             .map { buildEmoji(codePoints, modifiable, it) }
-            .filter { DefaultTextPaint.hasGlyph(it) }
+            .filter { isValidEmoji(it) }
         return if (candidates.isEmpty()) null else candidates.toTypedArray()
     }
 }