LibDraw: Add emoji support to the Font class

https://github.com/SerenityOS/serenity/issues/490

Libraries/LibC/Makefile

@@ -12,7 +12,8 @@ AK_OBJS = \
     ../../AK/JsonObject.o \
     ../../AK/JsonParser.o \
     ../../AK/LogStream.o \
-    ../../AK/MappedFile.o
+    ../../AK/MappedFile.o \
+    ../../AK/Utf8View.o
 
 LIBC_OBJS = \
        SharedBuffer.o \

Libraries/LibDraw/Font.cpp

@@ -8,6 +8,9 @@
 #include <LibC/mman.h>
 #include <LibC/stdio.h>
 #include <LibC/unistd.h>
+#include <AK/Utf8View.h>
+#include "Emoji.h"
+#include "GraphicsBitmap.h"
 
 struct [[gnu::packed]] FontFileHeader
 {
@@ -170,17 +173,37 @@ bool Font::write_to_file(const StringView& path)
     return true;
 }
 
-int Font::width(const StringView& string) const
+int Font::glyph_or_emoji_width(u32 codepoint) const
 {
-    if (!string.length())
-        return 0;
+    if (codepoint < 256)
+        return glyph_width((char)codepoint);
 
     if (m_fixed_width)
-        return string.length() * m_glyph_width;
+        return m_glyph_width;
+
+    auto emoji = Emoji::emoji_for_codepoint(codepoint);
+    if (emoji == nullptr)
+        return glyph_width('?');
+    return emoji->bitmap().size().width();
+}
+
+int Font::width(const StringView& string) const
+{
+    Utf8View utf8 { string };
+    return width(utf8);
+}
 
+int Font::width(const Utf8View& utf8) const
+{
+    bool first = true;
     int width = 0;
-    for (int i = 0; i < string.length(); ++i)
-        width += glyph_width(string.characters_without_null_termination()[i]) + 1;
 
-    return width - 1;
+    for (u32 codepoint : utf8) {
+        if (!first)
+            width += glyph_spacing();
+        first = false;
+        width += glyph_or_emoji_width(codepoint);
+    }
+
+    return width;
 }

Libraries/LibDraw/Font.h

@@ -6,6 +6,7 @@
 #include <AK/RefCounted.h>
 #include <AK/Types.h>
 #include <LibDraw/Rect.h>
+#include <AK/Utf8View.h>
 
 // FIXME: Make a MutableGlyphBitmap buddy class for FontEditor instead?
 class GlyphBitmap {
@@ -58,11 +59,13 @@ public:
     GlyphBitmap glyph_bitmap(char ch) const { return GlyphBitmap(&m_rows[(u8)ch * m_glyph_height], { glyph_width(ch), m_glyph_height }); }
 
     u8 glyph_width(char ch) const { return m_fixed_width ? m_glyph_width : m_glyph_widths[(u8)ch]; }
+    int glyph_or_emoji_width(u32 codepoint) const;
     u8 glyph_height() const { return m_glyph_height; }
     u8 min_glyph_width() const { return m_min_glyph_width; }
     u8 max_glyph_width() const { return m_max_glyph_width; }
     u8 glyph_spacing() const { return m_fixed_width ? 0 : 1; }
-    int width(const StringView& string) const;
+    int width(const StringView&) const;
+    int width(const Utf8View&) const;
 
     String name() const { return m_name; }
     void set_name(const StringView& name) { m_name = name; }