From 3c1bdcd20140fcd3d374818b9defb80c12c39163 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Breno=20Rodrigues=20Guimar=C3=A3es?= <brenorg@gmail.com>
Date: Sun, 19 Apr 2020 10:51:01 -0300
Subject: [PATCH] Create a compile-time table for converting color codepoints
 to utf8 (#11349)

For this to be possible, the function to convert a codepoint to urf8 was
moved to the header and made constexpr.

Now it's not necessary to store a std::string just to serve as a buffer
for holding this string. All the computation is done at compile time.
---
 src/openrct2/localisation/Language.h | 31 +++++++++++++++++++++++++++-
 src/openrct2/localisation/UTF8.cpp   | 30 ---------------------------
 src/openrct2/world/Banner.cpp        | 30 ++++++++++++++++++++++-----
 src/openrct2/world/Banner.h          |  1 -
 4 files changed, 55 insertions(+), 37 deletions(-)

diff --git a/src/openrct2/localisation/Language.h b/src/openrct2/localisation/Language.h
index 7bdc8385cd..11ab1e9969 100644
--- a/src/openrct2/localisation/Language.h
+++ b/src/openrct2/localisation/Language.h
@@ -95,7 +95,6 @@ const char* language_get_string(rct_string_id id);
 bool language_open(int32_t id);
 
 uint32_t utf8_get_next(const utf8* char_ptr, const utf8** nextchar_ptr);
-utf8* utf8_write_codepoint(utf8* dst, uint32_t codepoint);
 int32_t utf8_insert_codepoint(utf8* dst, uint32_t codepoint);
 bool utf8_is_codepoint_start(const utf8* text);
 void utf8_remove_format_codes(utf8* text, bool allowcolours);
@@ -109,4 +108,34 @@ void language_free_object_string(rct_string_id stringId);
 rct_string_id language_get_object_override_string_id(const char* identifier, uint8_t index);
 rct_string_id language_allocate_object_string(const std::string& target);
 
+constexpr utf8* utf8_write_codepoint(utf8* dst, uint32_t codepoint)
+{
+    if (codepoint <= 0x7F)
+    {
+        dst[0] = (utf8)codepoint;
+        return dst + 1;
+    }
+    else if (codepoint <= 0x7FF)
+    {
+        dst[0] = 0xC0 | ((codepoint >> 6) & 0x1F);
+        dst[1] = 0x80 | (codepoint & 0x3F);
+        return dst + 2;
+    }
+    else if (codepoint <= 0xFFFF)
+    {
+        dst[0] = 0xE0 | ((codepoint >> 12) & 0x0F);
+        dst[1] = 0x80 | ((codepoint >> 6) & 0x3F);
+        dst[2] = 0x80 | (codepoint & 0x3F);
+        return dst + 3;
+    }
+    else
+    {
+        dst[0] = 0xF0 | ((codepoint >> 18) & 0x07);
+        dst[1] = 0x80 | ((codepoint >> 12) & 0x3F);
+        dst[2] = 0x80 | ((codepoint >> 6) & 0x3F);
+        dst[3] = 0x80 | (codepoint & 0x3F);
+        return dst + 4;
+    }
+}
+
 #endif
diff --git a/src/openrct2/localisation/UTF8.cpp b/src/openrct2/localisation/UTF8.cpp
index a1b3f8b61d..4049e6a372 100644
--- a/src/openrct2/localisation/UTF8.cpp
+++ b/src/openrct2/localisation/UTF8.cpp
@@ -49,36 +49,6 @@ uint32_t utf8_get_next(const utf8* char_ptr, const utf8** nextchar_ptr)
     return result;
 }
 
-utf8* utf8_write_codepoint(utf8* dst, uint32_t codepoint)
-{
-    if (codepoint <= 0x7F)
-    {
-        dst[0] = (utf8)codepoint;
-        return dst + 1;
-    }
-    else if (codepoint <= 0x7FF)
-    {
-        dst[0] = 0xC0 | ((codepoint >> 6) & 0x1F);
-        dst[1] = 0x80 | (codepoint & 0x3F);
-        return dst + 2;
-    }
-    else if (codepoint <= 0xFFFF)
-    {
-        dst[0] = 0xE0 | ((codepoint >> 12) & 0x0F);
-        dst[1] = 0x80 | ((codepoint >> 6) & 0x3F);
-        dst[2] = 0x80 | (codepoint & 0x3F);
-        return dst + 3;
-    }
-    else
-    {
-        dst[0] = 0xF0 | ((codepoint >> 18) & 0x07);
-        dst[1] = 0x80 | ((codepoint >> 12) & 0x3F);
-        dst[2] = 0x80 | ((codepoint >> 6) & 0x3F);
-        dst[3] = 0x80 | (codepoint & 0x3F);
-        return dst + 4;
-    }
-}
-
 /**
  * Inserts the given codepoint at the given address, shifting all characters after along.
  * @returns the size of the inserted codepoint.
diff --git a/src/openrct2/world/Banner.cpp b/src/openrct2/world/Banner.cpp
index 0ba4476616..b495e55b96 100644
--- a/src/openrct2/world/Banner.cpp
+++ b/src/openrct2/world/Banner.cpp
@@ -33,6 +33,30 @@
 
 static Banner _banners[MAX_BANNERS];
 
+namespace
+{
+    template<uint32_t TFrom, uint32_t TTo> struct CodePointToUtf8
+    {
+        constexpr CodePointToUtf8()
+        {
+            for (uint32_t i = TFrom; i <= TTo; ++i)
+            {
+                utf8_write_codepoint(m_colors[i - TFrom], i);
+            }
+        }
+
+        constexpr auto operator()(uint8_t colourId) const
+        {
+            return m_colors[colourId];
+        }
+
+        using Utf8Colour = utf8[5]; // A 32bit codepoint uses at most 4 bytes in utf8
+        Utf8Colour m_colors[TTo - TFrom + 1]{};
+    };
+} // namespace
+
+static constexpr CodePointToUtf8<FORMAT_COLOUR_CODE_START, FORMAT_COLOUR_CODE_END> colourToUtf8;
+
 std::string Banner::GetText() const
 {
     uint8_t args[32]{};
@@ -47,14 +71,10 @@ size_t Banner::FormatTextTo(void* argsV, bool addColour) const
     int numColourArgs = 0;
     if (addColour)
     {
-        textColourUtf8.resize(5); // one code point in utf8 takes at most 4 bytes
-        auto terminator = utf8_write_codepoint(textColourUtf8.data(), FORMAT_COLOUR_CODE_START + text_colour);
-        *terminator = '\0';
-
         set_format_arg_on(args, numColourArgs, rct_string_id, STR_STRING_STRINGID);
         numColourArgs += sizeof(rct_string_id);
 
-        set_format_arg_on(args, numColourArgs, const char*, textColourUtf8.data());
+        set_format_arg_on(args, numColourArgs, const char*, colourToUtf8(text_colour));
         numColourArgs += sizeof(const char*);
 
         args += numColourArgs;
diff --git a/src/openrct2/world/Banner.h b/src/openrct2/world/Banner.h
index af53d3371b..644b038086 100644
--- a/src/openrct2/world/Banner.h
+++ b/src/openrct2/world/Banner.h
@@ -34,7 +34,6 @@ struct Banner
     uint8_t colour{};
     ride_id_t ride_index{};
     uint8_t text_colour{};
-    mutable std::string textColourUtf8;
     TileCoordsXY position;
 
     bool IsNull() const