Avoid to have a white line around the canvas

The canvas must have the same dims as the page in order to avoid to see the page
background.

src/display/display_utils.js

@@ -1103,8 +1103,12 @@ function setLayerDimensions(
 
     const w = `var(--scale-factor) * ${pageWidth}px`,
       h = `var(--scale-factor) * ${pageHeight}px`;
-    const widthStr = useRound ? `round(${w}, 1px)` : `calc(${w})`,
-      heightStr = useRound ? `round(${h}, 1px)` : `calc(${h})`;
+    const widthStr = useRound
+        ? `round(down, ${w}, var(--scale-round-x, 1px))`
+        : `calc(${w})`,
+      heightStr = useRound
+        ? `round(down, ${h}, var(--scale-round-y, 1px))`
+        : `calc(${h})`;
 
     if (!mustFlip || viewport.rotation % 180 === 0) {
       style.width = widthStr;

test/integration/viewer_spec.mjs

@@ -19,7 +19,10 @@ import {
   createPromise,
   getSpanRectFromText,
   loadAndWait,
+  scrollIntoView,
+  waitForPageRendered,
 } from "./test_utils.mjs";
+import { PNG } from "pngjs";
 
 describe("PDF viewer", () => {
   describe("Zoom origin", () => {
@@ -365,4 +368,75 @@ describe("PDF viewer", () => {
       });
     });
   });
+
+  describe("Canvas fits the page", () => {
+    let pages;
+
+    beforeAll(async () => {
+      pages = await loadAndWait(
+        "issue18694.pdf",
+        ".textLayer .endOfContent",
+        "page-width"
+      );
+    });
+
+    afterAll(async () => {
+      await closePages(pages);
+    });
+
+    it("must check that canvas perfectly fits the page whatever the zoom level is", async () => {
+      await Promise.all(
+        pages.map(async ([browserName, page]) => {
+          const debug = false;
+
+          // The pdf has a single page with a red background.
+          // We set the viewer background to red, because when screenshoting
+          // some part of the viewer background can be visible.
+          // But here we don't care about the viewer background: we only
+          // care about the page background and the canvas default color.
+
+          await page.evaluate(() => {
+            document.body.style.background = "#ff0000";
+            const toolbar = document.querySelector(".toolbar");
+            toolbar.style.display = "none";
+          });
+          await page.waitForSelector(".toolbar", { visible: false });
+          await page.evaluate(() => {
+            const p = document.querySelector(`.page[data-page-number="1"]`);
+            p.style.border = "none";
+          });
+
+          for (let i = 0; ; i++) {
+            const handle = await waitForPageRendered(page);
+            await page.evaluate(() => window.PDFViewerApplication.zoomOut());
+            await awaitPromise(handle);
+            await scrollIntoView(page, `.page[data-page-number="1"]`);
+
+            const element = await page.$(`.page[data-page-number="1"]`);
+            const png = await element.screenshot({
+              type: "png",
+              path: debug ? `foo${i}.png` : "",
+            });
+            const pageImage = PNG.sync.read(Buffer.from(png));
+            let buffer = new Uint32Array(pageImage.data.buffer);
+
+            // Search for the first red pixel.
+            const j = buffer.indexOf(0xff0000ff);
+            buffer = buffer.slice(j);
+
+            expect(buffer.every(x => x === 0xff0000ff))
+              .withContext(`In ${browserName}, in the ${i}th zoom in`)
+              .toBe(true);
+
+            const currentScale = await page.evaluate(
+              () => window.PDFViewerApplication.pdfViewer.currentScale
+            );
+            if (currentScale <= 0.1) {
+              break;
+            }
+          }
+        })
+      );
+    });
+  });
 });

test/pdfs/.gitignore

@@ -665,3 +665,4 @@
 !highlights.pdf
 !highlight.pdf
 !bug1708040.pdf
+!issue18694.pdf

test/unit/ui_utils_spec.js

@@ -16,6 +16,7 @@
 import {
   backtrackBeforeAllVisibleElements,
   binarySearchFirstItem,
+  calcRound,
   getPageSizeInches,
   getVisibleElements,
   isPortraitOrientation,
@@ -627,4 +628,17 @@ describe("ui_utils", function () {
       });
     });
   });
+
+  describe("calcRound", function () {
+    it("should handle different browsers/environments correctly", function () {
+      if (
+        typeof window !== "undefined" &&
+        window.navigator?.userAgent?.includes("Firefox")
+      ) {
+        expect(calcRound(1.6)).not.toEqual(1.6);
+      } else {
+        expect(calcRound(1.6)).toEqual(1.6);
+      }
+    });
+  });
 });

web/pdf_page_view.js

@@ -33,6 +33,7 @@ import {
 } from "pdfjs-lib";
 import {
   approximateFraction,
+  calcRound,
   DEFAULT_SCALE,
   floorToDivide,
   OutputScale,
@@ -127,6 +128,10 @@ class PDFPageView {
 
   #previousRotation = null;
 
+  #scaleRoundX = 1;
+
+  #scaleRoundY = 1;
+
   #renderError = null;
 
   #renderingState = RenderingStates.INITIAL;
@@ -1039,11 +1044,27 @@ class PDFPageView {
     const sfx = approximateFraction(outputScale.sx);
     const sfy = approximateFraction(outputScale.sy);
 
-    canvas.width = floorToDivide(width * outputScale.sx, sfx[0]);
-    canvas.height = floorToDivide(height * outputScale.sy, sfy[0]);
-    const { style } = canvas;
-    style.width = floorToDivide(width, sfx[1]) + "px";
-    style.height = floorToDivide(height, sfy[1]) + "px";
+    const canvasWidth = (canvas.width = floorToDivide(
+      calcRound(width * outputScale.sx),
+      sfx[0]
+    ));
+    const canvasHeight = (canvas.height = floorToDivide(
+      calcRound(height * outputScale.sy),
+      sfy[0]
+    ));
+    const pageWidth = floorToDivide(calcRound(width), sfx[1]);
+    const pageHeight = floorToDivide(calcRound(height), sfy[1]);
+    outputScale.sx = canvasWidth / pageWidth;
+    outputScale.sy = canvasHeight / pageHeight;
+
+    if (this.#scaleRoundX !== sfx[1]) {
+      div.style.setProperty("--scale-round-x", `${sfx[1]}px`);
+      this.#scaleRoundX = sfx[1];
+    }
+    if (this.#scaleRoundY !== sfy[1]) {
+      div.style.setProperty("--scale-round-y", `${sfy[1]}px`);
+      this.#scaleRoundY = sfy[1];
+    }
 
     // Add the viewport so it's known what it was originally drawn with.
     this.#viewportMap.set(canvas, viewport);

web/pdf_viewer.css

@@ -83,6 +83,8 @@
     canvas {
       margin: 0;
       display: block;
+      width: 100%;
+      height: 100%;
 
       &[hidden] {
         display: none;
@@ -101,6 +103,9 @@
 }
 
 .pdfViewer .page {
+  --scale-round-x: 1px;
+  --scale-round-y: 1px;
+
   direction: ltr;
   width: 816px;
   height: 1056px;

web/ui_utils.js

@@ -862,6 +862,25 @@ function toggleExpandedBtn(button, toggle, view = null) {
   view?.classList.toggle("hidden", !toggle);
 }
 
+// In Firefox, the css calc function uses f32 precision but the Chrome or Safari
+// are using f64 one. So in order to have the same rendering in all browsers, we
+// need to use the right precision in order to have correct dimensions.
+const calcRound =
+  typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")
+    ? Math.fround
+    : (function () {
+        if (
+          typeof PDFJSDev !== "undefined" &&
+          PDFJSDev.test("LIB") &&
+          typeof document === "undefined"
+        ) {
+          return x => x;
+        }
+        const e = document.createElement("div");
+        e.style.width = "round(down, calc(1.6666666666666665 * 792px), 1px)";
+        return e.style.width === "calc(1320px)" ? Math.fround : x => x;
+      })();
+
 export {
   animationStarted,
   apiPageLayoutToViewerModes,
@@ -870,6 +889,7 @@ export {
   AutoPrintRegExp,
   backtrackBeforeAllVisibleElements, // only exported for testing
   binarySearchFirstItem,
+  calcRound,
   CursorTool,
   DEFAULT_SCALE,
   DEFAULT_SCALE_DELTA,