Stable mousewheel scrolling, one wheel up + one wheel down = no change (#1131)

src/client/lazy-app/Compress/Output/custom-els/PinchZoom/index.ts

@@ -300,9 +300,13 @@ export default class PinchZoom extends HTMLElement {
       deltaY *= 15;
     }
 
+    const zoomingOut = deltaY > 0;
+
     // ctrlKey is true when pinch-zooming on a trackpad.
     const divisor = ctrlKey ? 100 : 300;
-    const scaleDiff = 1 - deltaY / divisor;
+    // when zooming out, invert the delta and the ratio to keep zoom stable
+    const ratio = 1 - (zoomingOut ? -deltaY : deltaY) / divisor;
+    const scaleDiff = zoomingOut ? 1 / ratio : ratio;
 
     this._applyChange({
       scaleDiff,