Fix middle-mouse-drag speed of ScrollWidget with non-1 zoom level.

CHANGELOG.md

@@ -34,6 +34,7 @@ In this document, Mod is Ctrl on Windows/Linux and Cmd on Mac.
 - Copy cable color when cloning cables with Ctrl+click.
 - Fix key commands on AZERTY, Dvorak, and all other keyboard layouts.
 - Add Mouse device to Computer keyboard/mouse MIDI driver.
+- Make scrollbar mouse interaction similar to modern OS behavior.
 
 - Core
 	- Add Audio-2 module with stereo input/output, a level knob, and VU meters.

src/ui/ScrollWidget.cpp

@@ -109,7 +109,8 @@ void ScrollWidget::onDragMove(const event::DragMove& e) {
 	if (!(horizontalScrollBar->isVisible() || verticalScrollBar->isVisible()))
 		return;
 
-	offset = offset.minus(e.mouseDelta);
+	math::Vec offsetDelta = e.mouseDelta.div(getAbsoluteZoom());
+	offset = offset.minus(offsetDelta);
 }