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, ${w}, var(--scale-round-x))`
+        : `calc(${w})`,
+      heightStr = useRound
+        ? `round(down, ${h}, var(--scale-round-y))`
+        : `calc(${h})`;
 
     if (!mustFlip || viewport.rotation % 180 === 0) {
       style.width = widthStr;

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("", 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;
@@ -1036,11 +1041,27 @@ 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]) {
+      this.div.style.setProperty("--scale-round-x", `${sfx[1]}px`);
+      this.#scaleRoundX = sfx[1];
+    }
+    if (this.#scaleRoundY !== sfy[1]) {
+      this.div.style.setProperty("--scale-round-y", `${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 +862,18 @@ 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 = (function () {
+  if (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 +882,7 @@ export {
   AutoPrintRegExp,
   backtrackBeforeAllVisibleElements, // only exported for testing
   binarySearchFirstItem,
+  calcRound,
   CursorTool,
   DEFAULT_SCALE,
   DEFAULT_SCALE_DELTA,