Proposal #2 to restore how UI/dialogs used to render by prioritizing fallback fonts.

With the emojis support, a new font was added, which not only provides emojis
but also fancy colorful replacements for UTF-8 characters that used to be
supported by our fallback (monochrome) fonts: this causes discrepancies and
unwanted/undesired changes in scripted objects menus (e.g. an empty circle or
square may render as a black, full one, a heart may render red instead of white),
not to mention the larger font size used by the emoji characters...

This patch restores the aspect of such menus/dialogs/UI elements with UTF-8
characters that *are* supported by the usual fallback fonts (fonts which may
also vary from one viewer to another, and from one OS to another), so that
everything keeps working/rendering as it always did so far, while not impairing
the use of new colorful emojis.

This second proposal ensures that:
- "genuine" emojis (in the 0x1f000-0x1ffff range), will *always* be rendered
  using the new emojis font (this solves, for example, the monochrome "yellow
  faces" issue seen with some characters in my first proposal).
- Special UTF-8 characters (in the 0x2000-0x32FF range) which have been used by
  scripters so far, will render as they used to, using the monochrome fallback
  fonts (this repairs scripted dialogs menus).
- Remaining special characters, that do not have a corresponding glyph in the
  monochrome font, but do have one in the emojis font, will use the latter font
  to render.

It also got the nice side-effect of removing the dependency on the ICU4C library.

Note however that the recent commit:
https://github.com/secondlife/viewer/commit/326055ba82c22fedde186c6a56bafd4fe87e613a
will need to be reverted to allow this patch to actually fix scripted dialogs.

Also, some cleanup might be needed in skins/default/xui/*/emoji_characters.xml to
remove from it the special UTF-8 characters that will no longer be rendered with
fanciful colors, but instead with the monochrome font glyphs.

3 files changed, 11 insertions, 35 deletions

diff --git a/indra/llcommon/CMakeLists.txt b/indra/llcommon/CMakeLists.txt
index c947184dc8..5f4ed2fffa 100644
--- a/indra/llcommon/CMakeLists.txt
+++ b/indra/llcommon/CMakeLists.txt
@@ -3,7 +3,6 @@
 project(llcommon)
 
 include(00-Common)
-include(ICU4C)
 include(LLCommon)
 include(bugsplat)
 include(Linking)
@@ -283,7 +282,6 @@ target_link_libraries(
         ll::uriparser
         ll::oslibraries
         ll::tracy
-        ll::icu4c
     )
 
 target_include_directories(llcommon INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})
diff --git a/indra/llcommon/llstring.cpp b/indra/llcommon/llstring.cpp
index 4aa54bb12d..28c2ec5b39 100644
--- a/indra/llcommon/llstring.cpp
+++ b/indra/llcommon/llstring.cpp
@@ -30,7 +30,6 @@
 #include "llerror.h"
 #include "llfasttimer.h"
 #include "llsd.h"
-#include <unicode/uchar.h>
 #include <vector>
 
 #if LL_WINDOWS
@@ -1008,40 +1007,18 @@ std::string LLStringOps::sAM;
 std::string LLStringOps::sPM;
 
 // static
-bool LLStringOps::isEmoji(llwchar wch)
-{
-	int ublock = ublock_getCode(wch);
-	switch (ublock)
-	{
-		case UBLOCK_GENERAL_PUNCTUATION:
-		case UBLOCK_LETTERLIKE_SYMBOLS:
-		case UBLOCK_ARROWS:
-		case UBLOCK_MISCELLANEOUS_TECHNICAL:
-		case UBLOCK_ENCLOSED_ALPHANUMERICS:
-		case UBLOCK_GEOMETRIC_SHAPES:
-		case UBLOCK_MISCELLANEOUS_SYMBOLS:
-		case UBLOCK_DINGBATS:
-		case UBLOCK_CJK_SYMBOLS_AND_PUNCTUATION:
-		case UBLOCK_ENCLOSED_CJK_LETTERS_AND_MONTHS:
-		case UBLOCK_MISCELLANEOUS_SYMBOLS_AND_PICTOGRAPHS:
-		case UBLOCK_EMOTICONS:
-		case UBLOCK_TRANSPORT_AND_MAP_SYMBOLS:
-#if U_ICU_VERSION_MAJOR_NUM > 56
-		// Boost uses ICU so we can't update it independently
-		case UBLOCK_SUPPLEMENTAL_SYMBOLS_AND_PICTOGRAPHS:
-#endif // U_ICU_VERSION_MAJOR_NUM > 56
-			return true;
-		default:
-#if U_ICU_VERSION_MAJOR_NUM > 56
-			return false;
+bool LLStringOps::isEmoji(llwchar a)
+{
+#if 0   // Do not consider special characters that might have a corresponding
+        // glyph in the monochorme fallback fonts as a "genuine" emoji. HB
+    return a == 0xa9 || a == 0xae || (a >= 0x2000 && a < 0x3300) ||
+           (a >= 0x1f000 && a < 0x20000);
 #else
-			// See https://en.wikipedia.org/wiki/Supplemental_Symbols_and_Pictographs
-			return wch >= 0x1F900 && wch <= 0x1F9FF;
-#endif // U_ICU_VERSION_MAJOR_NUM > 56
-	}
+    // These are indeed "genuine" emojis, we *do want* rendered as such. HB
+    return a >= 0x1f000 && a < 0x20000;
+#endif
 }
 
-
 S32	LLStringOps::collate(const llwchar* a, const llwchar* b)
 { 
 	#if LL_WINDOWS
diff --git a/indra/llcommon/llstring.h b/indra/llcommon/llstring.h
index a40359115e..a8d910298c 100644
--- a/indra/llcommon/llstring.h
+++ b/indra/llcommon/llstring.h
@@ -189,7 +189,8 @@ public:
 	static bool isAlnum(char a) { return isalnum((unsigned char)a) != 0; }
 	static bool isAlnum(llwchar a) { return iswalnum(a) != 0; }
 
-	static bool isEmoji(llwchar wch);
+    // Returns true when 'a' corresponds to a "genuine" emoji. HB
+	static bool isEmoji(llwchar a);
 
 	static S32	collate(const char* a, const char* b) { return strcoll(a, b); }
 	static S32	collate(const llwchar* a, const llwchar* b);