Skip missing glyphs when drawing 2d canvas text.

Cargo.lock

@@ -544,6 +544,7 @@ dependencies = [
  "log",
  "lyon_geom 0.14.1",
  "num-traits",
+ "pathfinder_geometry",
  "pixels",
  "raqote",
  "servo_arc",

components/canvas/Cargo.toml

@@ -31,6 +31,7 @@ ipc-channel = "0.14"
 log = "0.4"
 lyon_geom = "0.14"
 num-traits = "0.2"
+pathfinder_geometry = "0.5"
 pixels = { path = "../pixels" }
 raqote = { version = "0.8", features = ["text"] }
 servo_arc = { path = "../servo_arc" }

components/canvas/raqote_backend.rs

@@ -527,11 +527,33 @@ impl GenericDrawTarget for raqote::DrawTarget {
         pattern: &canvas_data::Pattern,
         options: &DrawOptions,
     ) {
-        self.draw_text(
+        let mut start = pathfinder_geometry::vector::vec2f(start.x, start.y);
+        let mut ids = Vec::new();
+        let mut positions = Vec::new();
+        for c in text.chars() {
+            let id = match font.glyph_for_char(c) {
+                Some(id) => id,
+                None => {
+                    warn!("Skipping non-existent glyph {}", c);
+                    continue;
+                },
+            };
+            ids.push(id);
+            positions.push(Point2D::new(start.x(), start.y()));
+            let advance = match font.advance(id) {
+                Ok(advance) => advance,
+                Err(e) => {
+                    warn!("Skipping glyph {} with missing advance: {:?}", c, e);
+                    continue;
+                },
+            };
+            start += advance * point_size / 24. / 96.;
+        }
+        self.draw_glyphs(
             font,
             point_size,
-            text,
-            start,
+            &ids,
+            &positions,
             &pattern.source(),
             options.as_raqote(),
         );