Add a simple implementation of CanvasRenderingContext2d.fillText

1 files changed, 81 insertions, 0 deletions

diff --git a/components/canvas/raqote_backend.rs b/components/canvas/raqote_backend.rs
index 72eae8b40c8..6daa8712421 100644
--- a/components/canvas/raqote_backend.rs
+++ b/components/canvas/raqote_backend.rs
@@ -13,6 +13,9 @@ 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 lyon_geom::Arc;
 use raqote::PathOp;
 use std::marker::PhantomData;
@@ -539,6 +542,84 @@ impl GenericDrawTarget for raqote::DrawTarget {
             &DrawOptions::Raqote(draw_options),
         );
     }
+    // TODO
+    // This should eventually use the same infrastructure as layout
+    // (i.e. layout should be updated to use font-kit as well).
+    // Need to implement .font .
+    fn fill_text(
+        &mut self,
+        text: String,
+        x: f32,
+        y: f32,
+        max_width: Option<f64>,
+        pattern: canvas_data::Pattern,
+        draw_options: &DrawOptions,
+    ) {
+        // Replace all ASCII whitespace in text with U+0020 SPACE characters.
+        fn replace_whitespace(text: String) -> String {
+            text.chars()
+                .map(|c| match c {
+                    '\x09'..='\x0D' => '\x20',
+                    _ => c,
+                })
+                .collect()
+        }
+
+        // Compute the width of the text
+        fn get_text_width(text: &str, font: &font_kit::font::Font) -> f64 {
+            let point_size = 24.;
+            let mut length = 0.;
+            for c in text.chars() {
+                let id = font.glyph_for_char(c).unwrap();
+                length += (font.advance(id).unwrap() * point_size / 24. / 96.).x;
+            }
+            length as f64
+        }
+
+        let font = SystemSource::new()
+            .select_best_match(&[FamilyName::SansSerif], &Properties::new())
+            .unwrap()
+            .load()
+            .unwrap();
+
+        // text preparation algorithm
+        let (scale_factor, replaced_text) = match max_width {
+            Some(value) => {
+                if value <= 0. || !value.is_finite() {
+                    return;
+                } else {
+                    let replaced_text = replace_whitespace(text);
+                    let text_width = get_text_width(&replaced_text, &font);
+                    if value > text_width {
+                        (1., replaced_text)
+                    } else {
+                        (value / text_width, replaced_text)
+                    }
+                }
+            },
+            _ => (1., replace_whitespace(text)),
+        };
+
+        // Text scaling
+        let old_transform = self.get_transform().clone();
+        let new_transform = old_transform
+            .pre_translate(Vector2D::new(x as f32, 0.))
+            .pre_scale(scale_factor as f32, 1.)
+            .pre_translate(Vector2D::new(-x as f32, 0.));
+        self.set_transform(&new_transform);
+
+        self.draw_text(
+            &font,
+            24.,
+            &replaced_text,
+            Point2D::new(x, y),
+            &pattern.source(),
+            draw_options.as_raqote(),
+        );
+
+        // Restore the transform
+        self.set_transform(&old_transform);
+    }
     fn get_format(&self) -> SurfaceFormat {
         SurfaceFormat::Raqote(())
     }