Bug 1392361 - Fix zooming sensitivity on macOS

web/app.js

@@ -26,7 +26,7 @@ import {
  MAX_SCALE,
  MIN_SCALE,
  noContextMenuHandler,
- normalizeWheelEventDelta,
+ normalizeWheelEventDirection,
  parseQueryString,
  PresentationModeState,
  ProgressBar,
@@ -237,6 +237,7 @@ const PDFViewerApplication = {
  contentDispositionFilename: null,
  triggerDelayedFallback: null,
  _saveInProgress: false,
+ _wheelUnusedTicks: 0,
 
  // Called once when the document is loaded.
  async initialize(appConfig) {
@@ -1835,6 +1836,22 @@ const PDFViewerApplication = {
  _boundEvents.windowBeforePrint = null;
  _boundEvents.windowAfterPrint = null;
  },
+
+ accumulateWheelTicks(ticks) {
+ // If the scroll direction changed, reset the accumulated wheel ticks.
+ if (
+ (this._wheelUnusedTicks > 0 && ticks < 0) ||
+ (this._wheelUnusedTicks < 0 && ticks > 0)
+ ) {
+ this._wheelUnusedTicks = 0;
+ }
+ this._wheelUnusedTicks += ticks;
+ const wholeTicks =
+ Math.sign(this._wheelUnusedTicks) *
+ Math.floor(Math.abs(this._wheelUnusedTicks));
+ this._wheelUnusedTicks -= wholeTicks;
+ return wholeTicks;
+ },
 };
 
 let validateFileURL;
@@ -2492,13 +2509,34 @@ function webViewerWheel(evt) {
 
  const previousScale = pdfViewer.currentScale;
 
- const delta = normalizeWheelEventDelta(evt);
+ const delta = normalizeWheelEventDirection(evt);
+ let ticks = 0;
+ if (
+ evt.deltaMode === WheelEvent.DOM_DELTA_LINE ||
+ evt.deltaMode === WheelEvent.DOM_DELTA_PAGE
+ ) {
+ // For line-based devices, use one tick per event, because different
+ // OSs have different defaults for the number lines. But we generally
+ // want one "clicky" roll of the wheel (which produces one event) to
+ // adjust the zoom by one step.
+ if (Math.abs(delta) >= 1) {
+ ticks = Math.sign(delta);
+ } else {
+ // If we're getting fractional lines (I can't think of a scenario
+ // this might actually happen), be safe and use the accumulator.
+ ticks = PDFViewerApplication.accumulateWheelTicks(delta);
+ }
+ } else {
+ // pixel-based devices
+ const PIXELS_PER_LINE_SCALE = 30;
+ ticks = PDFViewerApplication.accumulateWheelTicks(
+ delta / PIXELS_PER_LINE_SCALE
+ );
+ }
 
- const MOUSE_WHEEL_DELTA_PER_PAGE_SCALE = 3.0;
- const ticks = delta * MOUSE_WHEEL_DELTA_PER_PAGE_SCALE;
  if (ticks < 0) {
  PDFViewerApplication.zoomOut(-ticks);
- } else {
+ } else if (ticks > 0) {
  PDFViewerApplication.zoomIn(ticks);
  }
 

web/ui_utils.js

@@ -636,13 +636,18 @@ function getPDFFileNameFromURL(url, defaultFilename = "document.pdf") {
  return suggestedFilename || defaultFilename;
 }
 
-function normalizeWheelEventDelta(evt) {
+function normalizeWheelEventDirection(evt) {
  let delta = Math.sqrt(evt.deltaX * evt.deltaX + evt.deltaY * evt.deltaY);
  const angle = Math.atan2(evt.deltaY, evt.deltaX);
  if (-0.25 * Math.PI < angle && angle < 0.75 * Math.PI) {
  // All that is left-up oriented has to change the sign.
  delta = -delta;
  }
+ return delta;
+}
+
+function normalizeWheelEventDelta(evt) {
+ let delta = normalizeWheelEventDirection(evt);
 
  const MOUSE_DOM_DELTA_PIXEL_MODE = 0;
  const MOUSE_DOM_DELTA_LINE_MODE = 1;
@@ -1017,6 +1022,7 @@ export {
  scrollIntoView,
  watchScroll,
  binarySearchFirstItem,
+ normalizeWheelEventDirection,
  normalizeWheelEventDelta,
  animationStarted,
  WaitOnType,