Introduce a viewer constant for document.documentElement.style

Over time, as we've been introducing JavaScript code to modify CSS variables, we've been adding shorthand properties to various classes to reduce unnecessary repetition when accessing the document-styles.
Rather than repeating this in multiple places, it seems overall simpler to just introduce a constant and re-use that throughout the viewer instead.

web/base_viewer.js

@@ -40,6 +40,7 @@ import {
   DEFAULT_SCALE,
   DEFAULT_SCALE_DELTA,
   DEFAULT_SCALE_VALUE,
+  docStyle,
   getVisibleElements,
   isPortraitOrientation,
   isValidRotation,
@@ -290,7 +291,6 @@ class BaseViewer {
     } else {
       this.renderingQueue = options.renderingQueue;
     }
-    this._doc = document.documentElement;
 
     this.scroll = watchScroll(this.container, this._scrollUpdate.bind(this));
     this.presentationModeState = PresentationModeState.UNKNOWN;
@@ -1016,7 +1016,7 @@ class BaseViewer {
       return;
     }
 
-    this._doc.style.setProperty("--zoom-factor", newScale);
+    docStyle.setProperty("--zoom-factor", newScale);
 
     const updateArgs = { scale: newScale };
     for (const pageView of this._pages) {
@@ -2067,7 +2067,7 @@ class BaseViewer {
     if (height !== this.#previousContainerHeight) {
       this.#previousContainerHeight = height;
 
-      this._doc.style.setProperty("--viewer-container-height", `${height}px`);
+      docStyle.setProperty("--viewer-container-height", `${height}px`);
     }
   }
 }

web/pdf_page_view.js

@@ -40,6 +40,7 @@ import {
 import {
   approximateFraction,
   DEFAULT_SCALE,
+  docStyle,
   OutputScale,
   RendererType,
   RenderingStates,
@@ -339,8 +340,7 @@ class PDFPageView {
     });
 
     if (this._isStandalone) {
-      const { style } = document.documentElement;
-      style.setProperty("--zoom-factor", this.scale);
+      docStyle.setProperty("--zoom-factor", this.scale);
     }
 
     if (this.svg) {

web/pdf_sidebar_resizer.js

@@ -13,6 +13,8 @@
  * limitations under the License.
  */
 
+import { docStyle } from "./ui_utils.js";
+
 const SIDEBAR_WIDTH_VAR = "--sidebar-width";
 const SIDEBAR_MIN_WIDTH = 200; // pixels
 const SIDEBAR_RESIZING_CLASS = "sidebarResizing";
@@ -34,7 +36,6 @@ class PDFSidebarResizer {
   constructor(options, eventBus, l10n) {
     this.isRTL = false;
     this.sidebarOpen = false;
-    this.doc = document.documentElement;
     this._width = null;
     this._outerContainerWidth = null;
     this._boundEvents = Object.create(null);
@@ -75,7 +76,8 @@ class PDFSidebarResizer {
       return false;
     }
     this._width = width;
-    this.doc.style.setProperty(SIDEBAR_WIDTH_VAR, `${width}px`);
+
+    docStyle.setProperty(SIDEBAR_WIDTH_VAR, `${width}px`);
     return true;
   }
 

web/toolbar.js

@@ -17,6 +17,7 @@ import {
   animationStarted,
   DEFAULT_SCALE,
   DEFAULT_SCALE_VALUE,
+  docStyle,
   MAX_SCALE,
   MIN_SCALE,
   noContextMenuHandler,
@@ -274,8 +275,7 @@ class Toolbar {
     maxWidth += 2 * scaleSelectOverflow;
 
     if (maxWidth > scaleSelectContainerWidth) {
-      const doc = document.documentElement;
-      doc.style.setProperty("--scale-select-container-width", `${maxWidth}px`);
+      docStyle.setProperty("--scale-select-container-width", `${maxWidth}px`);
     }
     // Zeroing the width and height cause Firefox to release graphics resources
     // immediately, which can greatly reduce memory consumption.

web/ui_utils.js

@@ -677,6 +677,13 @@ const animationStarted = new Promise(function (resolve) {
   window.requestAnimationFrame(resolve);
 });
 
+const docStyle =
+  typeof PDFJSDev !== "undefined" &&
+  PDFJSDev.test("LIB") &&
+  typeof document === "undefined"
+    ? null
+    : document.documentElement.style;
+
 function clamp(v, min, max) {
   return Math.min(Math.max(v, min), max);
 }
@@ -709,8 +716,7 @@ class ProgressBar {
     }
     this.div.classList.remove("indeterminate");
 
-    const doc = document.documentElement;
-    doc.style.setProperty("--progressBar-percent", `${this._percent}%`);
+    docStyle.setProperty("--progressBar-percent", `${this._percent}%`);
   }
 
   get percent() {
@@ -730,8 +736,7 @@ class ProgressBar {
     const container = viewer.parentNode;
     const scrollbarWidth = container.offsetWidth - viewer.offsetWidth;
     if (scrollbarWidth > 0) {
-      const doc = document.documentElement;
-      doc.style.setProperty("--progressBar-end-offset", `${scrollbarWidth}px`);
+      docStyle.setProperty("--progressBar-end-offset", `${scrollbarWidth}px`);
     }
   }
 
@@ -843,6 +848,7 @@ export {
   DEFAULT_SCALE,
   DEFAULT_SCALE_DELTA,
   DEFAULT_SCALE_VALUE,
+  docStyle,
   getActiveOrFocusedElement,
   getPageSizeInches,
   getVisibleElements,