1 files changed, 89 insertions, 0 deletions
diff --git a/components/fonts/lib.rs b/components/fonts/lib.rs
new file mode 100644
index 00000000000..305db5e53ef
--- /dev/null
+++ b/components/fonts/lib.rs
@@ -0,0 +1,89 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#![deny(unsafe_code)]
+
+mod font;
+mod font_cache_thread;
+mod font_context;
+mod font_store;
+mod font_template;
+mod glyph;
+#[allow(unsafe_code)]
+pub mod platform;
+mod shaper;
+
+pub use font::*;
+pub use font_cache_thread::*;
+pub use font_context::*;
+pub use font_store::*;
+pub use font_template::*;
+pub use glyph::*;
+pub use shaper::*;
+use unicode_properties::{emoji, EmojiStatus, UnicodeEmoji};
+
+/// Whether or not font fallback selection prefers the emoji or text representation
+/// of a character. If `None` then either presentation is acceptable.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum EmojiPresentationPreference {
+    None,
+    Text,
+    Emoji,
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct FallbackFontSelectionOptions {
+    pub character: char,
+    pub presentation_preference: EmojiPresentationPreference,
+}
+
+impl Default for FallbackFontSelectionOptions {
+    fn default() -> Self {
+        Self {
+            character: ' ',
+            presentation_preference: EmojiPresentationPreference::None,
+        }
+    }
+}
+
+impl FallbackFontSelectionOptions {
+    pub fn new(character: char, next_character: Option<char>) -> Self {
+        let presentation_preference = match next_character {
+            Some(next_character) if emoji::is_emoji_presentation_selector(next_character) => {
+                EmojiPresentationPreference::Emoji
+            },
+            Some(next_character) if emoji::is_text_presentation_selector(next_character) => {
+                EmojiPresentationPreference::Text
+            },
+            // We don't want to select emoji prsentation for any possible character that might be an emoji, because
+            // that includes characters such as '0' that are also used outside of emoji clusters. Instead, only
+            // select the emoji font for characters that explicitly have an emoji presentation (in the absence
+            // of the emoji presentation selectors above).
+            _ if matches!(
+                character.emoji_status(),
+                EmojiStatus::EmojiPresentation |
+                    EmojiStatus::EmojiPresentationAndModifierBase |
+                    EmojiStatus::EmojiPresentationAndEmojiComponent |
+                    EmojiStatus::EmojiPresentationAndModifierAndEmojiComponent
+            ) =>
+            {
+                EmojiPresentationPreference::Emoji
+            },
+            _ if character.is_emoji_char() => EmojiPresentationPreference::Text,
+            _ => EmojiPresentationPreference::None,
+        };
+        Self {
+            character,
+            presentation_preference,
+        }
+    }
+}
+
+pub(crate) fn float_to_fixed(before: usize, f: f64) -> i32 {
+    ((1i32 << before) as f64 * f) as i32
+}
+
+pub(crate) fn fixed_to_float(before: usize, f: i32) -> f64 {
+    f as f64 * 1.0f64 / ((1i32 << before) as f64)
+}