Auto merge of #25782 - kaiakz:master, r=jdm

Add a simple implementation of CanvasRenderingContext2d.fillText

<!-- Please describe your changes on the following line: -->
I added a simple implementation of CanvasRenderingContext2d.fillText.
Some code are merged from @mikrut, and I fixed a bug about text scaling.
Also, the bug of text rotation should be fixed after `raqote` merged my other PR.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix (part of) #11681 (GitHub issue number if applicable)

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- [X] There are tests for these changes

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3 files changed, 104 insertions, 4 deletions

diff --git a/components/canvas/Cargo.toml b/components/canvas/Cargo.toml
index 0917ad981a0..21f5a055cd3 100644
--- a/components/canvas/Cargo.toml
+++ b/components/canvas/Cargo.toml
@@ -44,3 +44,4 @@ webxr-api = {git = "https://github.com/servo/webxr", features = ["ipc"]}
 surfman = { version = "0.1", features = ["sm-angle", "sm-osmesa"] }
 surfman-chains = "0.3"
 surfman-chains-api = "0.2"
+font-kit = "0.5.0"
diff --git a/components/canvas/canvas_data.rs b/components/canvas/canvas_data.rs
index f291ce416e9..fa77b016dd0 100644
--- a/components/canvas/canvas_data.rs
+++ b/components/canvas/canvas_data.rs
@@ -266,6 +266,15 @@ pub trait GenericDrawTarget {
     );
     fn fill(&mut self, path: &Path, pattern: Pattern, draw_options: &DrawOptions);
     fn fill_rect(&mut self, rect: &Rect<f32>, pattern: Pattern, draw_options: Option<&DrawOptions>);
+    fn fill_text(
+        &mut self,
+        text: String,
+        x: f32,
+        y: f32,
+        max_width: Option<f64>,
+        pattern: Pattern,
+        draw_options: &DrawOptions,
+    );
     fn get_format(&self) -> SurfaceFormat;
     fn get_size(&self) -> Size2D<i32>;
     fn get_transform(&self) -> Transform2D<f32>;
@@ -458,10 +467,19 @@ impl<'a> CanvasData<'a> {
         }
     }
 
-    pub fn fill_text(&self, text: String, x: f64, y: f64, max_width: Option<f64>) {
-        error!(
-            "Unimplemented canvas2d.fillText. Values received: {}, {}, {}, {:?}.",
-            text, x, y, max_width
+    pub fn fill_text(&mut self, text: String, x: f64, y: f64, max_width: Option<f64>) {
+        // If any of the arguments are infinite or NaN, then return.
+        if !x.is_finite() || !y.is_finite() {
+            return;
+        }
+
+        self.drawtarget.fill_text(
+            text,
+            x as f32,
+            y as f32,
+            max_width,
+            self.state.fill_style.clone(),
+            &self.state.draw_options,
         );
     }
 
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(())
     }