Fix ./mach build --release --with-layout-2020

components/canvas/canvas_data.rs

@@ -7,9 +7,10 @@ use crate::raqote_backend::Repetition;
 use canvas_traits::canvas::*;
 use cssparser::RGBA;
 use euclid::default::{Point2D, Rect, Size2D, Transform2D, Vector2D};
-use euclid::point2;
+use euclid::{point2, vec2};
 use font_kit::family_name::FamilyName;
 use font_kit::font::Font;
+use font_kit::metrics::Metrics;
 use font_kit::properties::Properties;
 use font_kit::source::SystemSource;
 use gfx::font::FontHandleMethods;
@@ -281,7 +282,7 @@ pub trait GenericDrawTarget {
         point_size: f32,
         text: &str,
         start: Point2D<f32>,
-        pattern: Pattern,
+        pattern: &Pattern,
         draw_options: &DrawOptions,
     );
     fn fill_rect(&mut self, rect: &Rect<f32>, pattern: Pattern, draw_options: Option<&DrawOptions>);
@@ -499,13 +500,13 @@ impl<'a> CanvasData<'a> {
         text: String,
         x: f64,
         y: f64,
-        _max_width: Option<f64>,
-        _is_rtl: bool,
+        max_width: Option<f64>,
+        is_rtl: bool,
     ) {
-        // Step 2. Replace all ASCII whitespace in text with U+0020 SPACE characters.
+        // Step 2.
         let text = replace_ascii_whitespace(text);
 
-        // Step 3. Let font be the current font of target, as given by that object's font attribute.
+        // Step 3.
         let point_size = self
             .state
             .font_style
@@ -513,12 +514,18 @@ impl<'a> CanvasData<'a> {
             .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),
+            || load_system_font_from_style(None),
             |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_group
+                        .borrow_mut()
+                        .first(font_context)
+                        .expect("couldn't find font");
                     let font = font.borrow_mut();
+                    // Retrieving bytes from font template seems to panic for some core text fonts.
+                    // This check avoids having to obtain bytes from the font template data if they
+                    // are not already in the memory.
                     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)))
@@ -528,15 +535,73 @@ impl<'a> CanvasData<'a> {
                 })
             },
         );
-        let start = point2(x as f32, y as f32);
+        let font_width = font_width(&text, point_size, &font);
 
-        // TODO: Process bidi text
+        // Step 6.
+        let max_width = max_width.map(|width| width as f32);
+        let (width, scale_factor) = match max_width {
+            Some(max_width) if max_width > font_width => (max_width, 1.),
+            Some(max_width) => (font_width, max_width / font_width),
+            None => (font_width, 1.),
+        };
+
+        // Step 7.
+        let start = self.text_origin(x as f32, y as f32, &font.metrics(), width, is_rtl);
+
+        // TODO: Bidi text layout
+
+        let old_transform = self.get_transform();
+        self.set_transform(
+            &old_transform
+                .pre_translate(vec2(start.x, 0.))
+                .pre_scale(scale_factor, 1.)
+                .pre_translate(vec2(-start.x, 0.)),
+        );
 
         // 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);
+        self.drawtarget.fill_text(
+            &font,
+            point_size,
+            &text,
+            start,
+            &self.state.fill_style,
+            &self.state.draw_options,
+        );
+
+        self.set_transform(&old_transform);
+    }
+
+    fn text_origin(
+        &self,
+        x: f32,
+        y: f32,
+        metrics: &Metrics,
+        width: f32,
+        is_rtl: bool,
+    ) -> Point2D<f32> {
+        let text_align = match self.state.text_align {
+            TextAlign::Start if is_rtl => TextAlign::Right,
+            TextAlign::Start => TextAlign::Left,
+            TextAlign::End if is_rtl => TextAlign::Left,
+            TextAlign::End => TextAlign::Right,
+            text_align => text_align,
+        };
+        let anchor_x = match text_align {
+            TextAlign::Center => -width / 2.,
+            TextAlign::Right => -width,
+            _ => 0.,
+        };
+
+        let anchor_y = match self.state.text_baseline {
+            TextBaseline::Top => metrics.ascent,
+            TextBaseline::Hanging => metrics.ascent * HANGING_BASELINE_DEFAULT,
+            TextBaseline::Ideographic => -metrics.descent * IDEOGRAPHIC_BASELINE_DEFAULT,
+            TextBaseline::Middle => (metrics.ascent - metrics.descent) / 2.,
+            TextBaseline::Alphabetic => 0.,
+            TextBaseline::Bottom => -metrics.descent,
+        };
+
+        point2(x + anchor_x, y + anchor_y)
     }
 
     pub fn fill_rect(&mut self, rect: &Rect<f32>) {
@@ -1206,6 +1271,9 @@ impl<'a> Drop for CanvasData<'a> {
     }
 }
 
+const HANGING_BASELINE_DEFAULT: f32 = 0.8;
+const IDEOGRAPHIC_BASELINE_DEFAULT: f32 = 0.5;
+
 #[derive(Clone)]
 pub struct CanvasPaintState<'a> {
     pub draw_options: DrawOptions,
@@ -1321,19 +1389,23 @@ fn load_system_font_from_style(font_style: Option<&FontStyleStruct>) -> Font {
         .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),
+        Err(e) => {
+            error!("error getting font handle for style {:?}: {}", style, e);
+            return load_default_system_fallback_font(&properties);
+        },
     };
-    font_handle
-        .load()
-        .unwrap_or_else(|_| load_default_system_fallback_font(&properties))
+    font_handle.load().unwrap_or_else(|e| {
+        error!("error loading font for style {:?}: {}", style, e);
+        load_default_system_fallback_font(&properties)
+    })
 }
 
 fn load_default_system_fallback_font(properties: &Properties) -> Font {
     SystemSource::new()
         .select_best_match(&[FamilyName::SansSerif], properties)
-        .unwrap()
+        .expect("error getting font handle for default system font")
         .load()
-        .unwrap()
+        .expect("error loading default system font")
 }
 
 fn replace_ascii_whitespace(text: String) -> String {
@@ -1344,3 +1416,18 @@ fn replace_ascii_whitespace(text: String) -> String {
         })
         .collect()
 }
+
+// TODO: This currently calculates the width using just advances and doesn't
+// determine the fallback font in case a character glyph isn't found.
+fn font_width(text: &str, point_size: f32, font: &Font) -> f32 {
+    let metrics = font.metrics();
+    let mut width = 0.;
+    for c in text.chars() {
+        if let Some(glyph_id) = font.glyph_for_char(c) {
+            if let Ok(advance) = font.advance(glyph_id) {
+                width += advance.x() * point_size / metrics.units_per_em as f32;
+            }
+        }
+    }
+    width
+}