Fix left offset when scrolling to search result

When computing the left offset of the highlighted text, we cannot use
.offsetLeft because the text might have been scaled through CSS, and it
needs to be taken into account.

Use `.getClientRects()`/`.getBoundingClientRect()` instead, which will
return measurements scaled appropriately.

test/integration/find_spec.mjs

@@ -126,4 +126,31 @@ describe("find bar", () => {
       );
     });
   });
+
+  describe("issue19207.pdf", () => {
+    let pages;
+
+    beforeAll(async () => {
+      pages = await loadAndWait("issue19207.pdf", ".textLayer", 200);
+    });
+
+    afterAll(async () => {
+      await closePages(pages);
+    });
+
+    it("must scroll to the search result text", async () => {
+      await Promise.all(
+        pages.map(async ([browserName, page]) => {
+          // Search for "40"
+          await page.click("#viewFindButton");
+          await page.waitForSelector("#viewFindButton", { hidden: false });
+          await page.type("#findInput", "40");
+
+          const highlight = await page.waitForSelector(".textLayer .highlight");
+
+          expect(await highlight.isIntersectingViewport()).toBeTrue();
+        })
+      );
+    });
+  });
 });

test/pdfs/.gitignore

@@ -690,3 +690,4 @@
 !inks_basic.pdf
 !issue19182.pdf
 !issue18911.pdf
+!issue19207.pdf

web/text_highlighter.js

@@ -193,8 +193,15 @@ class TextHighlighter {
         span.className = `${className} appended`;
         span.append(node);
         div.append(span);
-        return className.includes("selected") ? span.offsetLeft : 0;
+
+        if (className.includes("selected")) {
+          const { left } = span.getClientRects()[0];
+          const parentLeft = div.getBoundingClientRect().left;
+          return left - parentLeft;
+        }
+        return 0;
       }
+
       div.append(node);
       return 0;
     }