Add fontconfig support to locate fonts

Also restructure things a little bit to facilitate more robust
fallback implementation.

.gitignore

@@ -1,3 +1,4 @@
 /Cargo.lock
 /target/
 **/*.rs.bk
+.*.sw*

Cargo.toml

@@ -6,7 +6,7 @@ version = "0.1.0"
 [dependencies]
 failure = "0.1.1"
 hexdump = "0.1.0"
-sdl2 = {version="0.31.0", features=["bundled"]}
+sdl2 = {version="0.31.0", features=["bundled", "static-link"]}
 vte = "0.3.2"
 
 [dependencies.font]

font/src/ft/fcwrap.rs

@@ -0,0 +1,266 @@
+//! Slightly higher level helper for fontconfig
+use failure::{self, Error};
+pub use fontconfig::fontconfig::*;
+use std::ffi::{CStr, CString};
+use std::mem;
+use std::ptr;
+
+static FC_MONO: i32 = 100;
+
+pub struct FontSet {
+    fonts: *mut FcFontSet,
+}
+
+impl Drop for FontSet {
+    fn drop(&mut self) {
+        unsafe {
+            FcFontSetDestroy(self.fonts);
+        }
+    }
+}
+
+pub struct FontSetIter<'a> {
+    set: &'a FontSet,
+    position: isize,
+}
+
+impl<'a> Iterator for FontSetIter<'a> {
+    type Item = Pattern;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        unsafe {
+            if self.position == (*self.set.fonts).nfont as isize {
+                None
+            } else {
+                let pat = *(*self.set.fonts)
+                    .fonts
+                    .offset(self.position)
+                    .as_mut()
+                    .unwrap();
+                FcPatternReference(pat);
+                self.position += 1;
+                Some(Pattern { pat })
+            }
+        }
+    }
+}
+
+impl FontSet {
+    pub fn iter(&self) -> FontSetIter {
+        FontSetIter {
+            set: &self,
+            position: 0,
+        }
+    }
+
+    pub fn add(&mut self, pat: &Pattern) {
+        unsafe {
+            FcFontSetAdd(self.fonts, pat.pat);
+        }
+    }
+}
+
+#[repr(C)]
+pub enum MatchKind {
+    Pattern = FcMatchPattern as isize,
+    Font = FcMatchFont as isize,
+    Scan = FcMatchScan as isize,
+}
+
+pub struct FcResultWrap(FcResult);
+
+impl FcResultWrap {
+    pub fn succeeded(&self) -> bool {
+        self.0 == FcResultMatch
+    }
+
+    pub fn as_err(&self) -> Error {
+        // the compiler thinks we defined these globals, when all
+        // we did was import them from elsewhere
+        #[allow(non_upper_case_globals)]
+        match self.0 {
+            FcResultMatch => failure::err_msg("FcResultMatch"),
+            FcResultNoMatch => failure::err_msg("FcResultNoMatch"),
+            FcResultTypeMismatch => failure::err_msg("FcResultTypeMismatch"),
+            FcResultNoId => failure::err_msg("FcResultNoId"),
+            FcResultOutOfMemory => failure::err_msg("FcResultOutOfMemory"),
+            _ => format_err!("FcResult holds invalid value {}", self.0),
+        }
+    }
+
+    pub fn result<T>(&self, t: T) -> Result<T, Error> {
+        match self.0 {
+            FcResultMatch => Ok(t),
+            _ => Err(self.as_err()),
+        }
+    }
+}
+
+pub struct Pattern {
+    pat: *mut FcPattern,
+}
+
+impl Pattern {
+    pub fn new() -> Result<Pattern, Error> {
+        unsafe {
+            let p = FcPatternCreate();
+            ensure!(!p.is_null(), "FcPatternCreate failed");
+            Ok(Pattern { pat: p })
+        }
+    }
+
+    pub fn add_string(&mut self, key: &str, value: &str) -> Result<(), Error> {
+        let key = CString::new(key)?;
+        let value = CString::new(value)?;
+        unsafe {
+            ensure!(
+                FcPatternAddString(
+                    self.pat,
+                    key.as_ptr(),
+                    value.as_ptr() as *const u8,
+                ) != 0,
+                "failed to add string property {:?} -> {:?}",
+                key,
+                value
+            );
+            Ok(())
+        }
+    }
+
+    pub fn add_integer(&mut self, key: &str, value: i32) -> Result<(), Error> {
+        let key = CString::new(key)?;
+        unsafe {
+            ensure!(
+                FcPatternAddInteger(self.pat, key.as_ptr(), value) != 0,
+                "failed to set integer property {:?} -> {}",
+                key,
+                value
+            );
+            Ok(())
+        }
+    }
+
+
+    pub fn family(&mut self, family: &str) -> Result<(), Error> {
+        self.add_string("family", family)
+    }
+
+    pub fn monospace(&mut self) -> Result<(), Error> {
+        self.add_integer("spacing", FC_MONO)
+    }
+
+    pub fn print(&self) {
+        unsafe {
+            FcPatternPrint(self.pat);
+        }
+    }
+
+    pub fn format(&self, fmt: &str) -> Result<String, Error> {
+        let fmt = CString::new(fmt)?;
+        unsafe {
+            let s = FcPatternFormat(self.pat, fmt.as_ptr() as *const u8);
+            ensure!(!s.is_null(), "failed to format pattern");
+
+            let res = CStr::from_ptr(s as *const i8).to_string_lossy().into_owned();
+            FcStrFree(s);
+            Ok(res)
+        }
+    }
+
+    pub fn render_prepare(&self, pat: &Pattern) -> Result<Pattern, Error> {
+        unsafe {
+            let pat = FcFontRenderPrepare(ptr::null_mut(), self.pat, pat.pat);
+            ensure!(!pat.is_null(), "failed to prepare pattern");
+            Ok(Pattern { pat })
+        }
+    }
+
+    pub fn parse(pattern: &str) -> Result<Pattern, Error> {
+        let pattern = CString::new(pattern)?;
+        unsafe {
+            let p = FcNameParse(pattern.as_ptr() as *const u8);
+            ensure!(!p.is_null(), "failed to parse {:?}", pattern);
+            Ok(Pattern { pat: p })
+        }
+    }
+
+    pub fn config_substitute(
+        &mut self,
+        match_kind: MatchKind,
+    ) -> Result<(), Error> {
+        unsafe {
+            ensure!(
+                FcConfigSubstitute(
+                    ptr::null_mut(),
+                    self.pat,
+                    mem::transmute(match_kind),
+                ) != 0,
+                "FcConfigSubstitute failed"
+            );
+            Ok(())
+        }
+    }
+
+    pub fn default_substitute(&mut self) {
+        unsafe {
+            FcDefaultSubstitute(self.pat);
+        }
+    }
+
+    pub fn find_match(&self) -> Result<Pattern, Error> {
+        unsafe {
+            let mut res = FcResultWrap(0);
+            let pat = FcFontMatch(
+                ptr::null_mut(),
+                self.pat,
+                &mut res.0 as *mut _,
+            );
+            res.result(Pattern{pat})
+        }
+    }
+
+    pub fn sort(&self, trim: bool) -> Result<FontSet, Error> {
+        unsafe {
+            let mut res = FcResultWrap(0);
+            let fonts = FcFontSort(
+                ptr::null_mut(),
+                self.pat,
+                if trim { 1 } else { 0 },
+                ptr::null_mut(),
+                &mut res.0 as *mut _,
+            );
+
+            res.result(FontSet{fonts})
+        }
+    }
+
+    pub fn get_file(&self) -> Result<String, Error> {
+        self.get_string("file")
+    }
+
+    pub fn get_string(&self, key: &str) -> Result<String, Error> {
+        unsafe {
+            let key = CString::new(key)?;
+            let mut ptr: *mut u8 = ptr::null_mut();
+            let res = FcResultWrap(FcPatternGetString(
+                self.pat,
+                key.as_ptr(),
+                0,
+                &mut ptr as *mut *mut u8,
+            ));
+            if !res.succeeded() {
+                Err(res.as_err())
+            } else {
+                Ok(CStr::from_ptr(ptr as *const i8).to_string_lossy().into_owned())
+            }
+        }
+    }
+}
+
+impl Drop for Pattern {
+    fn drop(&mut self) {
+        unsafe {
+            FcPatternDestroy(self.pat);
+        }
+    }
+}

font/src/ft/ftwrap.rs

@@ -47,6 +47,12 @@ impl Face {
         )
     }
 
+    pub fn has_codepoint(&self, cp: char) -> bool {
+        unsafe {
+            FT_Get_Char_Index(self.face, cp as u64) != 0
+        }
+    }
+
     pub fn load_and_render_glyph(
         &mut self,
         glyph_index: FT_UInt,

font/src/ft/mod.rs

@@ -1,6 +1,7 @@
 use failure::Error;
 pub mod ftwrap;
 pub mod hbwrap;
+pub mod fcwrap;
 use self::ftwrap::Library;
 
 pub struct FTEngine {

src/main.rs

@@ -11,19 +11,44 @@ use sdl2::pixels::{Color, PixelFormatEnum};
 use sdl2::rect::Rect;
 use sdl2::render::{BlendMode, Texture, TextureCreator};
 
+use font::ft::fcwrap;
 use font::ft::ftwrap;
 use font::ft::hbwrap;
 use std::mem;
 use std::slice;
 
-struct Glyph<'a> {
-    tex: Texture<'a>,
-    width: u32,
-    height: u32,
+#[derive(Copy, Clone, Debug)]
+struct GlyphInfo {
+    glyph_pos: u32,
+    cluster: u32,
     x_advance: i32,
     y_advance: i32,
     x_offset: i32,
     y_offset: i32,
+}
+
+impl GlyphInfo {
+    pub fn new(
+        info: &hbwrap::hb_glyph_info_t,
+        pos: &hbwrap::hb_glyph_position_t,
+    ) -> GlyphInfo {
+        GlyphInfo {
+            glyph_pos: info.codepoint,
+            cluster: info.cluster,
+            x_advance: pos.x_advance / 64,
+            y_advance: pos.y_advance / 64,
+            x_offset: pos.x_offset / 64,
+            y_offset: pos.y_offset / 64,
+        }
+    }
+}
+
+
+struct Glyph<'a> {
+    tex: Texture<'a>,
+    width: u32,
+    height: u32,
+    info: GlyphInfo,
     bearing_x: i32,
     bearing_y: i32,
 }
@@ -32,7 +57,7 @@ impl<'a> Glyph<'a> {
     fn new<T>(
         texture_creator: &'a TextureCreator<T>,
         glyph: &ftwrap::FT_GlyphSlotRec_,
-        pos: &hbwrap::hb_glyph_position_t,
+        info: &GlyphInfo,
     ) -> Result<Glyph<'a>, Error> {
         let mode: ftwrap::FT_Pixel_Mode =
             unsafe { mem::transmute(glyph.bitmap.pixel_mode as u32) };
@@ -60,10 +85,7 @@ impl<'a> Glyph<'a> {
                     tex,
                     width: width as u32,
                     height: height as u32,
-                    x_advance: pos.x_advance / 64,
-                    y_advance: pos.y_advance / 64,
-                    x_offset: pos.x_offset / 64,
-                    y_offset: pos.y_offset / 64,
+                    info: *info,
                     bearing_x: glyph.bitmap_left,
                     bearing_y: glyph.bitmap_top,
                 })
@@ -73,24 +95,88 @@ impl<'a> Glyph<'a> {
     }
 }
 
-fn glyphs_for_text<'a, T>(
-    texture_creator: &'a TextureCreator<T>,
-    s: &str,
-) -> Result<Vec<Glyph<'a>>, Error> {
+struct FontInfo {
+    face: ftwrap::Face,
+    font: hbwrap::Font,
+}
+
+struct FontHolder {
+    lib: ftwrap::Library,
+    size: i64,
+    pattern: fcwrap::Pattern,
+    font_list: fcwrap::FontSet,
+    fonts: Vec<FontInfo>,
+}
+
+#[derive(Debug)]
+struct ShapedCluster {
+    /// index into FontHolder.fonts
+    font_idx: usize,
+    /// holds shaped results
+    info: Vec<GlyphInfo>,
+}
+
+impl Drop for FontHolder {
+    fn drop(&mut self) {
+        // Ensure that we drop the fonts before we drop the
+        // library, otherwise we will end up faulting
+        self.fonts.clear();
+    }
+}
+
+impl FontHolder {
+    fn new(size: i64) -> Result<FontHolder, Error> {
         let mut lib = ftwrap::Library::new()?;
         lib.set_lcd_filter(
             ftwrap::FT_LcdFilter::FT_LCD_FILTER_DEFAULT,
         )?;
-    let mut face =
-        lib.new_face("/home/wez/.fonts/OperatorMonoLig-Book.otf", 0)?;
-    face.set_char_size(0, 36 * 64, 96, 96)?;
-    let mut font = hbwrap::Font::new(&face);
-    let lang = hbwrap::language_from_string("en")?;
-    let mut buf = hbwrap::Buffer::new()?;
-    buf.set_script(hbwrap::HB_SCRIPT_LATIN);
-    buf.set_direction(hbwrap::HB_DIRECTION_LTR);
-    buf.set_language(lang);
-    buf.add_str(s);
+
+        let mut pattern = fcwrap::Pattern::new()?;
+        pattern.family("Operator Mono SSm Lig")?;
+        pattern.family("Emoji One")?;
+        pattern.monospace()?;
+        pattern.config_substitute(fcwrap::MatchKind::Pattern)?;
+        pattern.default_substitute();
+        let font_list = pattern.sort(true)?;
+
+        Ok(FontHolder {
+            lib,
+            size,
+            font_list,
+            pattern,
+            fonts: Vec::new(),
+        })
+    }
+
+    fn load_next_fallback(&mut self) -> Result<(), Error> {
+        let idx = self.fonts.len();
+        let pat = self.font_list.iter().nth(idx).ok_or(failure::err_msg(
+            "no more fallbacks",
+        ))?;
+        let pat = self.pattern.render_prepare(&pat)?;
+        let file = pat.get_file()?;
+
+        let mut face = self.lib.new_face(file, 0)?;
+        face.set_char_size(0, self.size * 64, 96, 96)?;
+        let font = hbwrap::Font::new(&face);
+
+        self.fonts.push(FontInfo { face, font });
+        Ok(())
+    }
+
+    fn get_font(&mut self, idx: usize) -> Result<&mut FontInfo, Error> {
+        if idx >= self.fonts.len() {
+            self.load_next_fallback()?;
+            ensure!(
+                idx < self.fonts.len(),
+                "should not ask for a font later than the next prepared font"
+            );
+        }
+
+        Ok(&mut self.fonts[idx])
+    }
+
+    fn shape(&mut self, s: &str) -> Result<Vec<ShapedCluster>, Error> {
         let features = vec![
             // kerning
             hbwrap::feature_from_string("kern")?,
@@ -99,53 +185,95 @@ fn glyphs_for_text<'a, T>(
             // contextual ligatures
             hbwrap::feature_from_string("clig")?,
         ];
-    font.shape(&mut buf, Some(features.as_slice()));
 
+        let mut buf = hbwrap::Buffer::new()?;
+        buf.set_script(hbwrap::HB_SCRIPT_LATIN);
+        buf.set_direction(hbwrap::HB_DIRECTION_LTR);
+        buf.set_language(hbwrap::language_from_string("en")?);
+        buf.add_str(s);
+
+        let font_idx = 0;
+
+        self.shape_with_font(font_idx, &mut buf, &features)?;
         let infos = buf.glyph_infos();
         let positions = buf.glyph_positions();
-    let mut result = Vec::new();
+
+        let mut cluster = Vec::new();
 
         for (i, info) in infos.iter().enumerate() {
             let pos = &positions[i];
-        println!(
-            "info {} glyph_pos={}, cluster={} x_adv={} y_adv={} x_off={} y_off={}",
-            i,
-            info.codepoint,
-            info.cluster,
-            pos.x_advance,
-            pos.y_advance,
-            pos.x_offset,
-            pos.y_offset
-        );
-
-        let glyph = face.load_and_render_glyph(
-            info.codepoint,
-            (ftwrap::FT_LOAD_COLOR) as i32,
-            ftwrap::FT_Render_Mode::FT_RENDER_MODE_LCD,
-        )?;
-
-
-        let g = Glyph::new(texture_creator, glyph, pos)?;
-
-        /*
-        println!(
-            "width={} height={} advx={} advy={} bearing={},{}",
-            g.width,
-            g.height,
-            g.x_advance,
-            g.y_advance,
-            g.bearing_x,
-            g.bearing_y
-        ); */
-
-        result.push(g);
+            // TODO: if info.codepoint == 0 here then we should
+            // rebuild that portion of the string and reshape it
+            // with the next fallback font
+            cluster.push(GlyphInfo::new(info, pos));
         }
 
+        println!("shaped: {:?}", cluster);
+
+        Ok(vec![
+            ShapedCluster {
+                font_idx,
+                info: cluster,
+            },
+        ])
+    }
+
+    fn shape_with_font(
+        &mut self,
+        idx: usize,
+        buf: &mut hbwrap::Buffer,
+        features: &Vec<hbwrap::hb_feature_t>,
+    ) -> Result<(), Error> {
+        let info = self.get_font(idx)?;
+        info.font.shape(buf, Some(features.as_slice()));
+        Ok(())
+    }
+
+    fn load_glyph(
+        &mut self,
+        font_idx: usize,
+        glyph_pos: u32,
+    ) -> Result<&ftwrap::FT_GlyphSlotRec_, Error> {
+        let info = &mut self.fonts[font_idx];
+        info.face.load_and_render_glyph(
+            glyph_pos,
+            (ftwrap::FT_LOAD_COLOR) as i32,
+            ftwrap::FT_Render_Mode::FT_RENDER_MODE_LCD,
+        )
+    }
+}
+
+fn glyphs_for_text<'a, T>(
+    texture_creator: &'a TextureCreator<T>,
+    s: &str,
+) -> Result<Vec<Glyph<'a>>, Error> {
+
+    let mut font_holder = FontHolder::new(36)?;
+
+    let mut result = Vec::new();
+    for cluster in font_holder.shape(s)? {
+        for info in cluster.info.iter() {
+            if info.glyph_pos == 0 {
+                println!("skip: no codepoint for this one");
+                continue;
+            }
+
+            let glyph =
+                font_holder.load_glyph(cluster.font_idx, info.glyph_pos)?;
+
+            if glyph.bitmap.width == 0 || glyph.bitmap.rows == 0 {
+                println!("skip: bitmap for this has 0 dimensions {:?}", glyph);
+                continue;
+            }
+
+            let g = Glyph::new(texture_creator, glyph, info)?;
+            result.push(g);
+        }
+    }
     Ok(result)
 }
 
 fn run() -> Result<(), Error> {
-
     let sdl_context = sdl2::init().map_err(failure::err_msg)?;
     let video_subsys = sdl_context.video().map_err(failure::err_msg)?;
     let window = video_subsys
@@ -155,7 +283,7 @@ fn run() -> Result<(), Error> {
         .build()?;
     let mut canvas = window.into_canvas().build()?;
     let texture_creator = canvas.texture_creator();
-    let glyphs = glyphs_for_text(&texture_creator, "foo->bar();")?;
+    let mut glyphs = glyphs_for_text(&texture_creator, "foo->bar(); ❤")?;
 
     for event in sdl_context
         .event_pump()
@@ -176,21 +304,22 @@ fn run() -> Result<(), Error> {
 
                 let mut x = 10i32;
                 let mut y = 100i32;
-                for g in glyphs.iter() {
+                for g in glyphs.iter_mut() {
+                    g.tex.set_color_mod(0xb3, 0xb3, 0xb3);
                     canvas
                         .copy(
                             &g.tex,
                             Some(Rect::new(0, 0, g.width, g.height)),
                             Some(Rect::new(
-                                x + g.x_offset - g.bearing_x,
-                                y - (g.y_offset + g.bearing_y as i32) as i32,
+                                x + g.info.x_offset - g.bearing_x,
+                                y - (g.info.y_offset + g.bearing_y as i32) as i32,
                                 g.width,
                                 g.height,
                             )),
                         )
                         .map_err(failure::err_msg)?;
-                    x += g.x_advance;
-                    y += g.y_advance;
+                    x += g.info.x_advance;
+                    y += g.info.y_advance;
                 }
 
                 canvas.present();