From 0c19010ca279da1685e1d442bf7567082780cb43 Mon Sep 17 00:00:00 2001
From: Gordon Williams <gw@pur3.co.uk>
Date: Mon, 3 Jun 2024 15:58:05 +0100
Subject: [PATCH] Bangle.js: when converting text to bitmaps, try and split up
 emoji so we can render just those in color. Rendering text as well uses more
 memory but means text is rendered white, which doesn't work on some
 backgrounds

---
 .../banglejs/BangleJSDeviceSupport.java       | 43 +++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/banglejs/BangleJSDeviceSupport.java b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/banglejs/BangleJSDeviceSupport.java
index 6ef224d0f..530477e89 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/banglejs/BangleJSDeviceSupport.java
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/banglejs/BangleJSDeviceSupport.java
@@ -1236,6 +1236,21 @@ public class BangleJSDeviceSupport extends AbstractBTLEDeviceSupport {
         return renderUnicodeWordPartAsImage(word);
     }
 
+    /* is the given character code an emoji? Note that `char` is only 0..65535, so many emoji will
+      actually be made of 2 surrogate chars. To work around this, we just assume that anything with a surrogate
+      is an emoji, which will be true in most cases */
+    public boolean isCharCodeEmoji(char ch) {
+        if (ch>=0x2190 && ch<=0x21FF) return true;
+        if (ch>=0x2600 && ch<=0x26FF) return true;
+        if (ch>=0x2700 && ch<=0x27BF) return true;
+        if (ch>=0x3000 && ch<=0x303F) return true;
+        if (ch>=0xD800 && ch<=0xDFFF) return true; // high/low surrogate
+        if (ch>=0xFE00 && ch<=0xFE0F) return true; // variation selector 1 (2 is U+E0100 so is in a surrogate)
+        //if (ch>=0x1F300 && ch<=0x1F64F) return true; // needs a surrogate
+        //if (ch>=0x1F680 && ch<=0x1F6FF) return true; // needs a surrogate
+        return false;
+    }
+
     public String renderUnicodeAsImage(String txt) {
         // FIXME: it looks like we could implement this as customStringFilter now so it happens automatically
         if (txt==null) return null;
@@ -1250,6 +1265,7 @@ public class BangleJSDeviceSupport extends AbstractBTLEDeviceSupport {
         String word = "";
         StringBuilder result = new StringBuilder();
         boolean needsTranslate = false;
+        boolean wordIsAllEmoji = true;
         for (int i=0;i<txt.length();i++) {
             char ch = txt.charAt(i);
             // Special cases where we can just use a built-in character...
@@ -1261,6 +1277,32 @@ public class BangleJSDeviceSupport extends AbstractBTLEDeviceSupport {
             else if (ch =='】') ch=']';
             else if (ch=='‘' || ch=='’' || ch=='‛' || ch=='′' || ch=='ʹ') ch='\'';
             else if (ch=='“' || ch=='”' || ch =='„' || ch=='‟' || ch=='″') ch='"';
+            else if (ch == 0xFEFF) continue; // nonbreaking space - ignore
+            boolean isCharEmoji = isCharCodeEmoji(ch);
+            if (isCharEmoji) {
+                if (!wordIsAllEmoji) {
+                    // if the word is all emoji we are fine, just fall through.
+                    // but here we have characters already and we want to translate those
+                    // separately, so we can have a color emoji on its own.
+                    if (needsTranslate) { // convert word
+                        LOG.info("renderUnicodeAsImage converting " + word);
+                        result.append(renderUnicodeWordAsImage(word));
+                    } else { // or just copy across
+                        result.append(word);
+                    }
+                    word = "";
+                    wordIsAllEmoji = true;
+                }
+                needsTranslate = true;
+            } else {
+                if (!word.isEmpty() && wordIsAllEmoji) {
+                    // this isn't am emoji, but it follows one - render that separately!
+                    result.append(renderUnicodeWordAsImage(word));
+                    word = "";
+                    needsTranslate = false;
+                }
+                wordIsAllEmoji = ch>=0xFE00;
+            }
             // chars which break words up
             if (" -_/:.,?!'\"&*()[]".indexOf(ch)>=0) {
                 // word split
@@ -1272,6 +1314,7 @@ public class BangleJSDeviceSupport extends AbstractBTLEDeviceSupport {
                 }
                 word = "";
                 needsTranslate = false;
+                wordIsAllEmoji = true;
             } else {
                 // TODO: better check?
                 if (ch>255) needsTranslate = true;