fix(web): measure canvas text with draw style

crates/op-host-web/src/canvaskit.rs

@@ -212,6 +212,8 @@ extern "C" {
     );
     #[wasm_bindgen(method, js_name = measureText)]
     fn measure_text(this: &OpCk, t: &str, sz: f32) -> f32;
+    #[wasm_bindgen(method, js_name = measureTextStyled)]
+    fn measure_text_styled(this: &OpCk, t: &str, sz: f32, weight: i32, italic: bool) -> f32;
     #[wasm_bindgen(method, js_name = registerSystemFont)]
     fn register_system_font(this: &OpCk, family: &str, bytes: &[u8]) -> bool;
     #[wasm_bindgen(method, js_name = clipRect)]
@@ -541,10 +543,21 @@ impl RenderBackend for CanvasKitBackend {
         }
     }
     fn measure_text(&mut self, text: &str, font_size: f32) -> f32 {
-        self.ck.measure_text(text, font_size)
+        self.ck.measure_text_styled(text, font_size, 400, false)
     }
-    fn measure_text_weighted(&mut self, text: &str, font_size: f32, _weight: u16) -> f32 {
-        self.ck.measure_text(text, font_size)
+    fn measure_text_weighted(&mut self, text: &str, font_size: f32, weight: u16) -> f32 {
+        self.ck
+            .measure_text_styled(text, font_size, i32::from(weight), false)
+    }
+    fn measure_text_styled(
+        &mut self,
+        text: &str,
+        font_size: f32,
+        weight: u16,
+        italic: bool,
+    ) -> f32 {
+        self.ck
+            .measure_text_styled(text, font_size, weight as i32, italic)
     }
 
     fn clip_rect(&mut self, rect: Rect) {

crates/op-host-web/src/op_ck_bridge.js

@@ -396,13 +396,17 @@ export async function opCkInit(canvasId) {
       p.delete();
     },
     measureText(t, sz) {
+      return this.measureTextStyled(t, sz, 400, false);
+    },
+    measureTextStyled(t, sz, weight, italic) {
       let w = 0;
       for (const seg of segments(t)) {
         if (shouldUseBrowserTextFallback(seg.text, seg.emoji)) {
-          w += browserTextMeasure(seg.text, sz);
+          w += browserTextMeasure(seg.text, sz, weight, italic);
           continue;
         }
         const f = new CK.Font(tfFor(seg.text, seg.emoji), sz);
+        if (italic && !seg.emoji) f.setSkewX(-0.25);
         w += runWidth(f, seg.text);
         f.delete();
       }

crates/op-host-web/tests/paint_order.rs

@@ -131,7 +131,7 @@ fn canvaskit_text_defaults_to_browser_system_font_fallback() {
         "const segments = (t)",
         "const shouldUseBrowserTextFallback = (_t, _emojiRun) => Boolean(browserTextCtx);",
         "drawBrowserText(seg.text, cx, y, sz, weight, italic, r, g, b, a)",
-        "browserTextMeasure(seg.text, sz)",
+        "browserTextMeasure(seg.text, sz, weight, italic)",
         "CK.Typeface.GetDefault()",
     ] {
         assert!(
@@ -177,6 +177,40 @@ fn canvaskit_browser_text_fallback_does_not_require_canvas_paint() {
     );
 }
 
+#[test]
+fn canvaskit_text_measurement_uses_draw_text_style() {
+    let bridge = std::fs::read_to_string(format!(
+        "{}/src/op_ck_bridge.js",
+        env!("CARGO_MANIFEST_DIR")
+    ))
+    .expect("CanvasKit bridge source is readable");
+    let backend =
+        std::fs::read_to_string(format!("{}/src/canvaskit.rs", env!("CARGO_MANIFEST_DIR")))
+            .expect("CanvasKit backend source is readable");
+
+    for marker in [
+        "measureTextStyled(t, sz, weight, italic)",
+        "browserTextMeasure(seg.text, sz, weight, italic)",
+    ] {
+        assert!(
+            bridge.contains(marker),
+            "CanvasKit bridge must preserve `{marker}` so measured text matches drawn text"
+        );
+    }
+
+    for marker in [
+        "fn measure_text_styled(",
+        "weight: u16,",
+        "italic: bool,",
+        ".measure_text_styled(text, font_size, weight as i32, italic)",
+    ] {
+        assert!(
+            backend.contains(marker),
+            "CanvasKit backend must preserve `{marker}` so web layout measures with draw-time text style"
+        );
+    }
+}
+
 #[test]
 fn canvaskit_paint_style_is_guarded_before_set_style() {
     let source = std::fs::read_to_string(format!(
@@ -243,7 +277,7 @@ fn canvaskit_bridge_uses_browser_text_fallback_when_local_font_api_is_unavailabl
         "const shouldUseBrowserTextFallback",
         "const drawBrowserText",
         "CK.MakeImageFromCanvasImageSource",
-        "browserTextMeasure(seg.text, sz)",
+        "browserTextMeasure(seg.text, sz, weight, italic)",
     ] {
         assert!(
             source.contains(marker),