Unify increaseScale/decreaseScale logic as updateScale

`updateScale` receives a `drawingDelay`, a `scaleFactor` and/or a number of `steps`.
If `scaleFactor` is a positive number different from `1` the current scale is multiplied by
that number. Otherwise, if `steps` if a positive integer the current scale is multiplied by
`DEFAULT_SCALE_DELTA` `steps` times. Finally, if `steps` is a negative integer, the
current scale is divided by `DEFAULT_SCALE_DELTA` `abs(steps)` times.

web/app.js

@@ -743,26 +743,23 @@ const PDFViewerApplication = {
     return this._initializedCapability.promise;
   },
 
-  zoomIn(steps, scaleFactor) {
+  updateZoom(steps, scaleFactor) {
     if (this.pdfViewer.isInPresentationMode) {
       return;
     }
-    this.pdfViewer.increaseScale({
+    this.pdfViewer.updateScale({
       drawingDelay: AppOptions.get("defaultZoomDelay"),
       steps,
       scaleFactor,
     });
   },
 
-  zoomOut(steps, scaleFactor) {
+  zoomIn() {
-    if (this.pdfViewer.isInPresentationMode) {
+    this.updateZoom(1);
-      return;
+  },
-    }
+
-    this.pdfViewer.decreaseScale({
+  zoomOut() {
-      drawingDelay: AppOptions.get("defaultZoomDelay"),
+    this.updateZoom(-1);
-      steps,
-      scaleFactor,
-    });
   },
 
   zoomReset() {
@@ -2635,13 +2632,7 @@ function webViewerWheel(evt) {
         scaleFactor,
         "_wheelUnusedFactor"
       );
-      if (scaleFactor < 1) {
+      PDFViewerApplication.updateZoom(null, scaleFactor);
-        PDFViewerApplication.zoomOut(null, scaleFactor);
-      } else if (scaleFactor > 1) {
-        PDFViewerApplication.zoomIn(null, scaleFactor);
-      } else {
-        return;
-      }
     } else {
       const delta = normalizeWheelEventDirection(evt);
 
@@ -2673,13 +2664,7 @@ function webViewerWheel(evt) {
         );
       }
 
-      if (ticks < 0) {
+      PDFViewerApplication.updateZoom(ticks);
-        PDFViewerApplication.zoomOut(-ticks);
-      } else if (ticks > 0) {
-        PDFViewerApplication.zoomIn(ticks);
-      } else {
-        return;
-      }
     }
 
     // After scaling the page via zoomIn/zoomOut, the position of the upper-
@@ -2794,26 +2779,14 @@ function webViewerTouchMove(evt) {
       distance / pDistance,
       "_touchUnusedFactor"
     );
-    if (newScaleFactor < 1) {
+    PDFViewerApplication.updateZoom(null, newScaleFactor);
-      PDFViewerApplication.zoomOut(null, newScaleFactor);
-    } else if (newScaleFactor > 1) {
-      PDFViewerApplication.zoomIn(null, newScaleFactor);
-    } else {
-      return;
-    }
   } else {
     const PIXELS_PER_LINE_SCALE = 30;
     const ticks = PDFViewerApplication._accumulateTicks(
       (distance - pDistance) / PIXELS_PER_LINE_SCALE,
       "_touchUnusedTicks"
     );
-    if (ticks < 0) {
+    PDFViewerApplication.updateZoom(ticks);
-      PDFViewerApplication.zoomOut(-ticks);
-    } else if (ticks > 0) {
-      PDFViewerApplication.zoomIn(ticks);
-    } else {
-      return;
-    }
   }
 
   PDFViewerApplication._centerAtPos(

web/pdf_viewer.js

@@ -2125,51 +2125,47 @@ class PDFViewer {
    */
 
   /**
-   * Increase the current zoom level one, or more, times.
+   * Changes the current zoom level by the specified amount.
    * @param {ChangeScaleOptions} [options]
    */
-  increaseScale({ drawingDelay, scaleFactor, steps } = {}) {
+  updateScale({ drawingDelay, scaleFactor = null, steps = null }) {
+    if (steps === null && scaleFactor === null) {
+      throw new Error(
+        "Invalid updateScale options: either `steps` or `scaleFactor` must be provided."
+      );
+    }
     if (!this.pdfDocument) {
       return;
     }
     let newScale = this._currentScale;
-    if (scaleFactor > 1) {
+    if (scaleFactor > 0 && scaleFactor !== 1) {
       newScale = Math.round(newScale * scaleFactor * 100) / 100;
-    } else {
+    } else if (steps) {
-      steps ??= 1;
+      const delta = steps > 0 ? DEFAULT_SCALE_DELTA : 1 / DEFAULT_SCALE_DELTA;
+      const round = steps > 0 ? Math.ceil : Math.floor;
+      steps = Math.abs(steps);
       do {
-        newScale =
+        newScale = round((newScale * delta).toFixed(2) * 10) / 10;
-          Math.ceil((newScale * DEFAULT_SCALE_DELTA).toFixed(2) * 10) / 10;
+      } while (--steps > 0);
-      } while (--steps > 0 && newScale < MAX_SCALE);
     }
-    this.#setScale(Math.min(MAX_SCALE, newScale), {
+    newScale = Math.max(MIN_SCALE, Math.min(MAX_SCALE, newScale));
-      noScroll: false,
+    this.#setScale(newScale, { noScroll: false, drawingDelay });
-      drawingDelay,
+  }
-    });
+
+  /**
+   * Increase the current zoom level one, or more, times.
+   * @param {ChangeScaleOptions} [options]
+   */
+  increaseScale(options = {}) {
+    this.updateScale({ ...options, steps: options.steps ?? 1 });
   }
 
   /**
    * Decrease the current zoom level one, or more, times.
    * @param {ChangeScaleOptions} [options]
    */
-  decreaseScale({ drawingDelay, scaleFactor, steps } = {}) {
+  decreaseScale(options = {}) {
-    if (!this.pdfDocument) {
+    this.updateScale({ ...options, steps: -(options.steps ?? 1) });
-      return;
-    }
-    let newScale = this._currentScale;
-    if (scaleFactor > 0 && scaleFactor < 1) {
-      newScale = Math.round(newScale * scaleFactor * 100) / 100;
-    } else {
-      steps ??= 1;
-      do {
-        newScale =
-          Math.floor((newScale / DEFAULT_SCALE_DELTA).toFixed(2) * 10) / 10;
-      } while (--steps > 0 && newScale > MIN_SCALE);
-    }
-    this.#setScale(Math.max(MIN_SCALE, newScale), {
-      noScroll: false,
-      drawingDelay,
-    });
   }
 
   #updateContainerHeightCss(height = this.container.clientHeight) {