From 85221b5e4e2c767c40fa15ea841a04ff49614533 Mon Sep 17 00:00:00 2001
From: Erin <sylphofelectricity@gmail.com>
Date: Tue, 15 Aug 2017 12:24:06 -0500
Subject: [PATCH] Start work on rasterizer

---
 textium/src/error.rs |  14 +++++++
 textium/src/lib.rs   | 111 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 125 insertions(+)
 create mode 100644 textium/src/error.rs
 create mode 100644 textium/src/lib.rs

diff --git a/textium/src/error.rs b/textium/src/error.rs
new file mode 100644
index 0000000..e32c0d7
--- /dev/null
+++ b/textium/src/error.rs
@@ -0,0 +1,14 @@
+use glium;
+
+#[derive(Debug)]
+pub enum Error {
+    TextureCreationError(glium::texture::TextureCreationError),
+    PackingError,
+    NotAGlyph(char),
+}
+
+impl From<glium::texture::TextureCreationError> for Error {
+    fn from(err: glium::texture::TextureCreationError) -> Error {
+        Error::TextureCreationError(err)
+    }
+}
diff --git a/textium/src/lib.rs b/textium/src/lib.rs
new file mode 100644
index 0000000..bfc69a5
--- /dev/null
+++ b/textium/src/lib.rs
@@ -0,0 +1,111 @@
+//! Textium is a small library that wires Rusttype up to Glium.
+
+extern crate rusttype;
+#[macro_use]
+extern crate glium;
+
+mod texture;
+mod geometry;
+mod error;
+
+use std::iter::Iterator;
+use std::collections::HashMap;
+use glium::backend::Facade;
+use glium::texture::Texture2d;
+use rusttype::Font;
+
+use texture::{Texture2dData, get_nearest_pow2};
+pub use error::Error;
+pub use geometry::Rect;
+
+/// Information used to render a glyph in a font.
+#[derive(Debug)]
+pub struct GlyphMetadata {
+    /// Coordinates of the top left of this glyph in the font's texture
+    texture_coord: (f32, f32),
+
+    /// Width and height of the glyph's texture.
+    texture_size: (f32, f32),
+
+    /// Size of the glyph, in ems.
+    em_size: (f32, f32),
+
+    /// Distance between the bottom of the glyph and the baseline, in ems.
+    baseline_distance: f32,
+
+    /// Left padding on the glyph, in ems.
+    left_padding: f32,
+
+    /// Left padding on the glyph, in ems.
+    right_padding: f32,
+}
+
+pub struct FontAtlas {
+    glyph_data: HashMap<char, GlyphMetadata>
+}
+
+pub struct FontTexture {
+    /// The GPU texture of packed glyphs.
+    texture: Texture2d,
+
+    /// Atlas describing where glyphs are.
+    atlas: FontAtlas,
+}
+
+pub trait FontPacker {
+    fn pack<C>(&self, font: Font, characters: C, font_size: u32) -> Result<(Texture2dData<f32>, HashMap<char, GlyphMetadata>), Error>
+        where C: Iterator<Item=char>;
+}
+
+pub struct NaiveFontPacker;
+impl FontPacker for NaiveFontPacker {
+    fn pack<C>(&self, font: Font, characters: C, font_size: u32) -> Result<(Texture2dData<f32>, HashMap<char, GlyphMetadata>), Error>
+        where C: Iterator<Item=char>
+    {
+        // Margin around each character in the texture
+        const MARGIN: u32 = 2;
+
+        let invalid_char_width = font_size / 2;
+
+        let estimated_glyphs = characters.size_hint().1.unwrap_or(0);
+
+        let mut texture_data: Vec<f32> = Vec::with_capacity(
+            estimated_glyphs * (font_size as usize).pow(2));
+
+        let texture_width = get_nearest_pow2(std::cmp::max(font_size * 2,
+            (((estimated_glyphs as u32) * font_size.pow(2)) as f32).sqrt() as u32));
+
+        let mut cursor = (0u32, 0u32);
+        let mut skip_rows = 0u32;
+
+        // let glyph_metadata = characters.map(|character| {
+        //     let scaled_glyph = font.glyph(character)
+        //         .ok_or_else(|| Error::NotAGlyph(character))?
+        //         .scaled(rusttype::Scale::uniform(font_size as f32));
+
+        //     // let h_metrics =
+        // }).collect::<Result<Vec<_>, Error>>()?;
+
+
+        Err(Error::PackingError)
+    }
+}
+
+// TODO: make this an actual From once TryFrom is stabilized.
+impl FontTexture {
+    /// Load a font from a Rusttype font into a Textium font texture, and upload it to Glium.
+    pub fn from_font<T>(font: Font, font_size: u32, facade: &Facade, packer: T) -> Result<FontTexture, Error>
+        where T: FontPacker
+    {
+        let characters: Vec<char> = (0..255).filter_map(|c| ::std::char::from_u32(c)).collect();
+
+        let (texture_data, meta) = packer.pack(font, characters.into_iter(), font_size)?;
+
+        let texture = Texture2d::new(facade, &texture_data)?;
+
+        Ok(FontTexture {
+            texture: texture,
+            glyph_metadata: meta,
+        })
+    }
+}