Enable textAlign, textBaseline and direction attributes for canvas

4 files changed, 165 insertions, 50 deletions

diff --git a/components/canvas/Cargo.toml b/components/canvas/Cargo.toml
index 3d7fa7f38e0..7285776ddec 100644
--- a/components/canvas/Cargo.toml
+++ b/components/canvas/Cargo.toml
@@ -24,6 +24,7 @@ cssparser = "0.27"
 euclid = "0.20"
 font-kit = "0.7"
 fnv = "1.0"
+gfx = { path = "../gfx" }
 gleam = "0.11"
 half = "1"
 ipc-channel = "0.14"
@@ -32,6 +33,7 @@ lyon_geom = "0.14"
 num-traits = "0.2"
 pixels = { path = "../pixels" }
 raqote = { version = "0.8", features = ["text"] }
+servo_arc = { path = "../servo_arc" }
 servo_config = { path = "../config" }
 sparkle = "0.1.24"
 style = { path = "../style" }
diff --git a/components/canvas/canvas_data.rs b/components/canvas/canvas_data.rs
index c90fca964f7..a1617be42dc 100644
--- a/components/canvas/canvas_data.rs
+++ b/components/canvas/canvas_data.rs
@@ -7,12 +7,22 @@ use crate::raqote_backend::Repetition;
 use canvas_traits::canvas::*;
 use cssparser::RGBA;
 use euclid::default::{Point2D, Rect, Size2D, Transform2D, Vector2D};
+use euclid::point2;
+use font_kit::family_name::FamilyName;
+use font_kit::font::Font;
+use font_kit::properties::Properties;
+use font_kit::source::SystemSource;
+use gfx::font::FontHandleMethods;
+use gfx::font_cache_thread::FontCacheThread;
+use gfx::font_context::FontContext;
 use ipc_channel::ipc::{IpcSender, IpcSharedMemory};
 use num_traits::ToPrimitive;
+use servo_arc::Arc as ServoArc;
+use std::cell::RefCell;
 #[allow(unused_imports)]
 use std::marker::PhantomData;
 use std::mem;
-use std::sync::Arc;
+use std::sync::{Arc, Mutex};
 use style::properties::style_structs::Font as FontStyleStruct;
 use webrender_api::units::RectExt as RectExt_;
 
@@ -267,10 +277,10 @@ pub trait GenericDrawTarget {
     fn fill(&mut self, path: &Path, pattern: Pattern, draw_options: &DrawOptions);
     fn fill_text(
         &mut self,
-        text: String,
-        x: f64,
-        y: f64,
-        max_width: Option<f64>,
+        font: &Font,
+        point_size: f32,
+        text: &str,
+        start: Point2D<f32>,
         pattern: Pattern,
         draw_options: &DrawOptions,
     );
@@ -370,6 +380,21 @@ pub enum Filter {
     Point,
 }
 
+pub(crate) type CanvasFontContext = FontContext<FontCacheThread>;
+
+thread_local!(static FONT_CONTEXT: RefCell<Option<CanvasFontContext>> = RefCell::new(None));
+
+pub(crate) fn with_thread_local_font_context<F, R>(canvas_data: &CanvasData, f: F) -> R
+where
+    F: FnOnce(&mut CanvasFontContext) -> R,
+{
+    FONT_CONTEXT.with(|font_context| {
+        f(font_context.borrow_mut().get_or_insert_with(|| {
+            FontContext::new(canvas_data.font_cache_thread.lock().unwrap().clone())
+        }))
+    })
+}
+
 pub struct CanvasData<'a> {
     backend: Box<dyn Backend>,
     drawtarget: Box<dyn GenericDrawTarget>,
@@ -382,6 +407,7 @@ pub struct CanvasData<'a> {
     old_image_key: Option<webrender_api::ImageKey>,
     /// An old webrender image key that can be deleted when the current epoch ends.
     very_old_image_key: Option<webrender_api::ImageKey>,
+    font_cache_thread: Mutex<FontCacheThread>,
     _canvas_id: CanvasId,
 }
 
@@ -395,6 +421,7 @@ impl<'a> CanvasData<'a> {
         webrender_api: Box<dyn WebrenderApi>,
         antialias: AntialiasMode,
         canvas_id: CanvasId,
+        font_cache_thread: FontCacheThread,
     ) -> CanvasData<'a> {
         let backend = create_backend();
         let draw_target = backend.create_drawtarget(size);
@@ -408,6 +435,7 @@ impl<'a> CanvasData<'a> {
             image_key: None,
             old_image_key: None,
             very_old_image_key: None,
+            font_cache_thread: Mutex::new(font_cache_thread),
             _canvas_id: canvas_id,
         }
     }
@@ -466,30 +494,49 @@ impl<'a> CanvasData<'a> {
         }
     }
 
-    pub fn fill_text(&mut self, text: String, x: f64, y: f64, max_width: Option<f64>) {
-        // 1. If maxWidth was provided but is less than or equal to zero or equal to NaN,
-        //    then return an empty array.
-        if max_width.map_or(false, |max_width| max_width <= 0.) {
-            return;
-        }
+    pub fn fill_text(
+        &mut self,
+        text: String,
+        x: f64,
+        y: f64,
+        _max_width: Option<f64>,
+        _is_rtl: bool,
+    ) {
+        // Step 2. Replace all ASCII whitespace in text with U+0020 SPACE characters.
+        let text = replace_ascii_whitespace(text);
 
-        // 2. Replace all ASCII whitespace in text with U+0020 SPACE characters.
-        let text = text
-            .chars()
-            .map(|c| match c {
-                ' ' | '\t' | '\n' | '\r' | '\x0C' => '\x20',
-                _ => c,
-            })
-            .collect();
-
-        self.drawtarget.fill_text(
-            text,
-            x,
-            y,
-            max_width,
-            self.state.fill_style.clone(),
-            &self.state.draw_options,
+        // Step 3. Let font be the current font of target, as given by that object's font attribute.
+        let point_size = self
+            .state
+            .font_style
+            .as_ref()
+            .map_or(10., |style| style.font_size.size().px());
+        let font_style = self.state.font_style.as_ref();
+        let font = font_style.map_or_else(
+            || load_system_font_from_style(font_style),
+            |style| {
+                with_thread_local_font_context(&self, |font_context| {
+                    let font_group = font_context.font_group(ServoArc::new(style.clone()));
+                    let font = font_group.borrow_mut().first(font_context).expect("");
+                    let font = font.borrow_mut();
+                    if let Some(bytes) = font.handle.template().bytes_if_in_memory() {
+                        Font::from_bytes(Arc::new(bytes), 0)
+                            .unwrap_or_else(|_| load_system_font_from_style(Some(style)))
+                    } else {
+                        load_system_font_from_style(Some(style))
+                    }
+                })
+            },
         );
+        let start = point2(x as f32, y as f32);
+
+        // TODO: Process bidi text
+
+        // Step 8.
+        let fill_style = self.state.fill_style.clone();
+        let draw_options = &self.state.draw_options;
+        self.drawtarget
+            .fill_text(&font, point_size, &text, start, fill_style, draw_options);
     }
 
     pub fn fill_rect(&mut self, rect: &Rect<f32>) {
@@ -1072,6 +1119,14 @@ impl<'a> CanvasData<'a> {
         self.state.font_style = Some(font_style)
     }
 
+    pub fn set_text_align(&mut self, text_align: TextAlign) {
+        self.state.text_align = text_align;
+    }
+
+    pub fn set_text_baseline(&mut self, text_baseline: TextBaseline) {
+        self.state.text_baseline = text_baseline;
+    }
+
     // https://html.spec.whatwg.org/multipage/#when-shadows-are-drawn
     fn need_to_draw_shadow(&self) -> bool {
         self.backend.need_to_draw_shadow(&self.state.shadow_color) &&
@@ -1164,6 +1219,8 @@ pub struct CanvasPaintState<'a> {
     pub shadow_blur: f64,
     pub shadow_color: Color,
     pub font_style: Option<FontStyleStruct>,
+    pub text_align: TextAlign,
+    pub text_baseline: TextBaseline,
 }
 
 /// It writes an image to the destination target
@@ -1245,3 +1302,45 @@ impl RectExt for Rect<u32> {
         self.cast()
     }
 }
+
+fn load_system_font_from_style(font_style: Option<&FontStyleStruct>) -> Font {
+    let mut properties = Properties::new();
+    let style = match font_style {
+        Some(style) => style,
+        None => return load_default_system_fallback_font(&properties),
+    };
+    let family_names = style
+        .font_family
+        .families
+        .iter()
+        .map(|family_name| family_name.into())
+        .collect::<Vec<FamilyName>>();
+    let properties = properties
+        .style(style.font_style.into())
+        .weight(style.font_weight.into())
+        .stretch(style.font_stretch.into());
+    let font_handle = match SystemSource::new().select_best_match(&family_names, &properties) {
+        Ok(handle) => handle,
+        Err(_) => return load_default_system_fallback_font(&properties),
+    };
+    font_handle
+        .load()
+        .unwrap_or_else(|_| load_default_system_fallback_font(&properties))
+}
+
+fn load_default_system_fallback_font(properties: &Properties) -> Font {
+    SystemSource::new()
+        .select_best_match(&[FamilyName::SansSerif], properties)
+        .unwrap()
+        .load()
+        .unwrap()
+}
+
+fn replace_ascii_whitespace(text: String) -> String {
+    text.chars()
+        .map(|c| match c {
+            ' ' | '\t' | '\n' | '\r' | '\x0C' => '\x20',
+            _ => c,
+        })
+        .collect()
+}
diff --git a/components/canvas/canvas_paint_thread.rs b/components/canvas/canvas_paint_thread.rs
index 9d9f8350e1d..763e7d04a18 100644
--- a/components/canvas/canvas_paint_thread.rs
+++ b/components/canvas/canvas_paint_thread.rs
@@ -7,6 +7,7 @@ use canvas_traits::canvas::*;
 use canvas_traits::ConstellationCanvasMsg;
 use crossbeam_channel::{select, unbounded, Sender};
 use euclid::default::Size2D;
+use gfx::font_cache_thread::FontCacheThread;
 use ipc_channel::ipc::{self, IpcSender};
 use ipc_channel::router::ROUTER;
 use std::borrow::ToOwned;
@@ -35,14 +36,19 @@ pub struct CanvasPaintThread<'a> {
     canvases: HashMap<CanvasId, CanvasData<'a>>,
     next_canvas_id: CanvasId,
     webrender_api: Box<dyn WebrenderApi>,
+    font_cache_thread: FontCacheThread,
 }
 
 impl<'a> CanvasPaintThread<'a> {
-    fn new(webrender_api: Box<dyn WebrenderApi>) -> CanvasPaintThread<'a> {
+    fn new(
+        webrender_api: Box<dyn WebrenderApi>,
+        font_cache_thread: FontCacheThread,
+    ) -> CanvasPaintThread<'a> {
         CanvasPaintThread {
             canvases: HashMap::new(),
             next_canvas_id: CanvasId(0),
             webrender_api,
+            font_cache_thread,
         }
     }
 
@@ -50,6 +56,7 @@ impl<'a> CanvasPaintThread<'a> {
     /// communicate with it.
     pub fn start(
         webrender_api: Box<dyn WebrenderApi + Send>,
+        font_cache_thread: FontCacheThread,
     ) -> (Sender<ConstellationCanvasMsg>, IpcSender<CanvasMsg>) {
         let (ipc_sender, ipc_receiver) = ipc::channel::<CanvasMsg>().unwrap();
         let msg_receiver = ROUTER.route_ipc_receiver_to_new_crossbeam_receiver(ipc_receiver);
@@ -57,7 +64,7 @@ impl<'a> CanvasPaintThread<'a> {
         thread::Builder::new()
             .name("CanvasThread".to_owned())
             .spawn(move || {
-                let mut canvas_paint_thread = CanvasPaintThread::new(webrender_api);
+                let mut canvas_paint_thread = CanvasPaintThread::new(webrender_api, font_cache_thread);
                 loop {
                     select! {
                         recv(msg_receiver) -> msg => {
@@ -118,6 +125,8 @@ impl<'a> CanvasPaintThread<'a> {
             AntialiasMode::None
         };
 
+        let font_cache_thread = self.font_cache_thread.clone();
+
         let canvas_id = self.next_canvas_id.clone();
         self.next_canvas_id.0 += 1;
 
@@ -126,6 +135,7 @@ impl<'a> CanvasPaintThread<'a> {
             self.webrender_api.clone(),
             antialias,
             canvas_id.clone(),
+            font_cache_thread,
         );
         self.canvases.insert(canvas_id.clone(), canvas_data);
 
@@ -134,9 +144,10 @@ impl<'a> CanvasPaintThread<'a> {
 
     fn process_canvas_2d_message(&mut self, message: Canvas2dMsg, canvas_id: CanvasId) {
         match message {
-            Canvas2dMsg::FillText(text, x, y, max_width, style) => {
+            Canvas2dMsg::FillText(text, x, y, max_width, style, is_rtl) => {
                 self.canvas(canvas_id).set_fill_style(style);
-                self.canvas(canvas_id).fill_text(text, x, y, max_width);
+                self.canvas(canvas_id)
+                    .fill_text(text, x, y, max_width, is_rtl);
             },
             Canvas2dMsg::FillRect(rect, style) => {
                 self.canvas(canvas_id).set_fill_style(style);
@@ -248,6 +259,12 @@ impl<'a> CanvasPaintThread<'a> {
             Canvas2dMsg::SetShadowBlur(value) => self.canvas(canvas_id).set_shadow_blur(value),
             Canvas2dMsg::SetShadowColor(color) => self.canvas(canvas_id).set_shadow_color(color),
             Canvas2dMsg::SetFont(font_style) => self.canvas(canvas_id).set_font(font_style),
+            Canvas2dMsg::SetTextAlign(text_align) => {
+                self.canvas(canvas_id).set_text_align(text_align)
+            },
+            Canvas2dMsg::SetTextBaseline(text_baseline) => {
+                self.canvas(canvas_id).set_text_baseline(text_baseline)
+            },
         }
     }
 
diff --git a/components/canvas/raqote_backend.rs b/components/canvas/raqote_backend.rs
index 3c30c0f1a19..5bab459b326 100644
--- a/components/canvas/raqote_backend.rs
+++ b/components/canvas/raqote_backend.rs
@@ -13,9 +13,7 @@ use canvas_traits::canvas::*;
 use cssparser::RGBA;
 use euclid::default::{Point2D, Rect, Size2D, Transform2D, Vector2D};
 use euclid::Angle;
-use font_kit::family_name::FamilyName;
-use font_kit::properties::Properties;
-use font_kit::source::SystemSource;
+use font_kit::font::Font;
 use lyon_geom::Arc;
 use raqote::PathOp;
 use std::marker::PhantomData;
@@ -78,6 +76,9 @@ impl Backend for RaqoteBackend {
 }
 
 impl<'a> CanvasPaintState<'a> {
+    pub const HANGING_BASELINE_DEFAULT: f32 = 0.8; // fraction of ascent
+    pub const IDEOGRAPHIC_BASELINE_DEFAULT: f32 = 0.5; // fraction descent
+
     pub fn new(_antialias: AntialiasMode) -> CanvasPaintState<'a> {
         let pattern = Pattern::Color(255, 0, 0, 0);
         CanvasPaintState {
@@ -91,6 +92,8 @@ impl<'a> CanvasPaintState<'a> {
             shadow_blur: 0.0,
             shadow_color: Color::Raqote(raqote::SolidSource::from_unpremultiplied_argb(0, 0, 0, 0)),
             font_style: None,
+            text_align: Default::default(),
+            text_baseline: Default::default(),
         }
     }
 }
@@ -520,26 +523,20 @@ impl GenericDrawTarget for raqote::DrawTarget {
 
     fn fill_text(
         &mut self,
-        text: String,
-        x: f64,
-        y: f64,
-        _max_width: Option<f64>,
+        font: &Font,
+        point_size: f32,
+        text: &str,
+        start: Point2D<f32>,
         pattern: canvas_data::Pattern,
-        draw_options: &DrawOptions,
+        options: &DrawOptions,
     ) {
-        let font = SystemSource::new()
-            .select_best_match(&[FamilyName::SansSerif], &Properties::new())
-            .unwrap()
-            .load()
-            .unwrap();
-
         self.draw_text(
-            &font,
-            24.,
-            &text,
-            Point2D::new(x as f32, y as f32),
+            font,
+            point_size,
+            text,
+            start,
             &pattern.source(),
-            draw_options.as_raqote(),
+            options.as_raqote(),
         );
     }