For text widgets, get the text from the AP stream instead of from the format callback (bug 1825002)

When fixing bug 1766987, I thought the field formatted value came from
the result of the format callback: I was wrong. The format callback is ran
but the value is unused (maybe it's useful to set some global vars... or
it's just a bug in Acrobat). Anyway the value to display is the one rendered
in the AP stream.
The field value setter has been simplified and that fixes issue #16409.

test/integration/scripting_spec.js

@@ -1897,4 +1897,70 @@ describe("Interaction", () => {
       );
     });
   });
+
+  describe("in bug1825002.pdf", () => {
+    let pages;
+
+    beforeAll(async () => {
+      pages = await loadAndWait("bug1825002.pdf", getSelector("23R"));
+    });
+
+    afterAll(async () => {
+      await closePages(pages);
+    });
+
+    it("must check that a field has the correct formatted value", async () => {
+      await Promise.all(
+        pages.map(async ([browserName, page]) => {
+          await page.waitForFunction(
+            "window.PDFViewerApplication.scriptingReady === true"
+          );
+
+          let text = await page.$eval(getSelector("23R"), el => el.value);
+          expect(text)
+            .withContext(`In ${browserName}`)
+            .toEqual("ABCDEFGHIJKLMN");
+
+          await page.click(getSelector("23R"));
+          await page.waitForFunction(
+            `${getQuerySelector("23R")}.value !== "ABCDEFGHIJKLMN"`
+          );
+
+          text = await page.$eval(getSelector("23R"), el => el.value);
+          expect(text).withContext(`In ${browserName}`).toEqual("123,45.7A");
+        })
+      );
+    });
+
+    it("must check that a field is empty", async () => {
+      await Promise.all(
+        pages.map(async ([browserName, page]) => {
+          await page.waitForFunction(
+            "window.PDFViewerApplication.scriptingReady === true"
+          );
+
+          let text = await page.$eval(getSelector("26R"), el => el.value);
+          expect(text).withContext(`In ${browserName}`).toEqual("");
+
+          await page.click(getSelector("26R"));
+          await page.type(getSelector("26R"), "abcde", { delay: 10 });
+
+          await page.click(getSelector("23R"));
+          await page.waitForTimeout(10);
+          await page.click(getSelector("26R"));
+
+          await page.keyboard.down("Control");
+          await page.keyboard.press("A");
+          await page.keyboard.up("Control");
+          await page.keyboard.press("Backspace");
+
+          await page.click(getSelector("23R"));
+          await page.waitForTimeout(10);
+
+          text = await page.$eval(getSelector("26R"), el => el.value);
+          expect(text).withContext(`In ${browserName}`).toEqual("");
+        })
+      );
+    });
+  });
 });

test/pdfs/.gitignore

@@ -591,3 +591,4 @@
 !issue16316.pdf
 !issue14565.pdf
 !multiline.pdf
+!bug1825002.pdf