From 78355c6a15487c8dd42643412b1aa227cd71b02e Mon Sep 17 00:00:00 2001
From: Erin <sylphofelectricity@gmail.com>
Date: Fri, 18 Aug 2017 22:51:10 -0500
Subject: [PATCH] textium: add face cache

---
 textium/src/cache.rs | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 textium/src/lib.rs   | 29 +++++++++++++++++-
 2 files changed, 111 insertions(+), 1 deletion(-)
 create mode 100644 textium/src/cache.rs

diff --git a/textium/src/cache.rs b/textium/src/cache.rs
new file mode 100644
index 0000000..a043740
--- /dev/null
+++ b/textium/src/cache.rs
@@ -0,0 +1,83 @@
+use std::rc::Rc;
+use std::error::Error;
+use std::collections::HashMap;
+
+use ::rasterizer::Font;
+use ::{FontAtlas, Scale};
+use ::texture::{Buffer2d, Bitmap};
+
+#[derive(PartialEq, Eq, Hash)]
+struct FaceKey {
+    name: String,
+    scale: Scale,
+}
+
+pub struct CachedFaceData<B> where B: Buffer2d {
+    buffer: B,
+    atlas: FontAtlas,
+    line_height: f32,
+}
+
+#[derive(Debug)]
+pub enum CacheError {
+    NoSuchFont(String)
+}
+
+pub struct Cache<'a, B> where B: Buffer2d {
+    fonts: HashMap<String, Font<'a>>,
+    faces: HashMap<FaceKey, CachedFaceData<B>>,
+    upload_queue: Vec<FaceKey>,
+}
+
+impl<'a, B> Cache<'a, B> where B: Buffer2d {
+    pub fn new() -> Cache<'a, B> {
+        Cache {
+            fonts: HashMap::new(),
+            faces: HashMap::new(),
+            upload_queue: Vec::new(),
+        }
+    }
+
+    pub fn add_font<S>(&mut self, name: S, font: Font<'a>) where S: Into<String> {
+        self.fonts.insert(name.into(), font);
+    }
+
+    pub fn build_face<I, F>(&mut self, name: &str, scale: f32,
+            chars: I, buffer_transform: F) -> Result<(), CacheError>
+        where I: Iterator<Item=char>,
+              F: Fn(Bitmap<u8>) -> Result<B, CacheError>
+    {
+        let key = FaceKey {name: String::from(name), scale: Scale(scale)};
+        if self.faces.contains_key(&key) {
+            return Ok(());
+        }
+
+        match self.fonts.get(name) {
+            Some(font) => {
+                let face_data = CachedFaceData::new(font, scale, chars, buffer_transform)?;
+                self.faces.insert(key, face_data);
+
+                Ok(())
+            },
+            None => Err(CacheError::NoSuchFont(name.into())),
+        }
+    }
+}
+
+impl<B> CachedFaceData<B> where B: Buffer2d {
+    pub fn new<I, F>(font: &Font, scale: f32, chars: I, buffer_transform: F)
+            -> Result<CachedFaceData<B>, CacheError>
+        where I: Iterator<Item=char>,
+              F: Fn(Bitmap<u8>) -> Result<B, CacheError>
+    {
+        let (atlas, bitmap, line_height): (FontAtlas, Bitmap<u8>, f32) = font.make_atlas(chars, scale, 1, 256, 256);
+
+        let bitmap = buffer_transform(bitmap)?;
+
+        Ok(CachedFaceData {
+            buffer: bitmap,
+            atlas: atlas,
+            line_height: line_height,
+        })
+    }
+}
diff --git a/textium/src/lib.rs b/textium/src/lib.rs
index 090887b..83b9740 100644
--- a/textium/src/lib.rs
+++ b/textium/src/lib.rs
@@ -14,8 +14,10 @@ pub mod texture;
 pub mod geometry;
 pub mod rasterizer;
 pub mod packer;
+pub mod cache;
 
 use std::collections::HashMap;
+use std::hash::{Hash, Hasher};
 use glium::texture::Texture2d;
 
 pub use error::Error;
@@ -23,7 +25,7 @@ pub use geometry::Rect;
 pub use rasterizer::Font;
 
 /// Information used to render a glyph in a font.
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct GlyphMetadata {
     /// Bounding box in the packed texture
     bounding_box: Rect<usize>,
@@ -41,10 +43,17 @@ pub struct GlyphMetadata {
 }
 
 /// Maps glyphs to their size, location, and rendering properties in a glyph atlas.
+#[derive(Debug)]
 pub struct FontAtlas {
     pub glyph_metadata: HashMap<char, GlyphMetadata>
 }
 
+impl FontAtlas {
+    pub fn info(&self, chr: char) -> Option<GlyphMetadata> {
+        self.glyph_metadata.get(&chr).cloned()
+    }
+}
+
 /// A GPU-backed font texture, plus a [`FontAtlas`].
 ///
 /// [`FontAtlas`]: struct.FontAtlas.html
@@ -56,3 +65,21 @@ pub struct FontTexture {
     pub atlas: FontAtlas,
 }
 
+#[derive(Debug, Clone, Copy)]
+struct Scale(f32);
+impl Scale {
+    fn canonicalize(&self) -> i64 {
+        (self.0 * 1024.0 * 1024.0).round() as i64
+    }
+}
+impl PartialEq for Scale {
+    fn eq(&self, other: &Self) -> bool {
+        self.canonicalize() == other.canonicalize()
+    }
+}
+impl Eq for Scale {}
+impl Hash for Scale {
+    fn hash<H>(&self, state: &mut H) where H: Hasher {
+        self.canonicalize().hash(state);
+    }
+}