Timeline Zoom Functionality

lib/ui/screens/timeline/timeline_screen.dart

@@ -1,7 +1,9 @@
 import 'dart:async';
+import 'dart:math' as Math;
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';
+import 'package:flutter/gestures.dart';
 import 'package:wonders/common_libs.dart';
 import 'package:wonders/logic/common/animate_utils.dart';
 import 'package:wonders/logic/common/debouncer.dart';

lib/ui/screens/timeline/widgets/_scrolling_viewport.dart

@@ -57,28 +57,35 @@ class _ScalingViewportState extends State<_ScrollingViewport> {
       scheduleMicrotask(controller._handleResize);
     }
     _prevSize = context.mq.size;
-    return GestureDetector(
-      // Handle pinch to zoom
-      onScaleUpdate: controller._handleScaleUpdate,
-      onScaleStart: controller._handleScaleStart,
-      behavior: HitTestBehavior.translucent,
-      // Fade in entire view when first shown
-      child: Stack(
-        children: [
-          // Main content area
-          _buildScrollingArea(context).maybeAnimate().fadeIn(),
+    return Listener(
+      onPointerSignal: (PointerSignalEvent e) {
+        if (HardwareKeyboard.instance.isControlPressed) {
+          controller._handleScaleUpdateMouse(((e as PointerScaleEvent).scale - 1) * 0.25);
+        }
+      },
+      child: GestureDetector(
+        // Handle pinch to zoom
+        onScaleUpdate: controller._handleScaleUpdate,
+        onScaleStart: controller._handleScaleStart,
+        behavior: HitTestBehavior.translucent,
+        // Fade in entire view when first shown
+        child: Stack(
+          children: [
+            // Main content area
+            _buildScrollingArea(context).maybeAnimate().fadeIn(),
 
-          // Dashed line with a year that changes as we scroll
-          IgnorePointerKeepSemantics(
-            child: AnimatedBuilder(
-              animation: controller.scroller,
-              builder: (_, __) {
-                return _DashedDividerWithYear(controller.calculateYearFromScrollPos());
-              },
+            // Dashed line with a year that changes as we scroll
+            IgnorePointerKeepSemantics(
+              child: AnimatedBuilder(
+                animation: controller.scroller,
+                builder: (_, __) {
+                  return _DashedDividerWithYear(controller.calculateYearFromScrollPos());
+                },
+              ),
             ),
-          ),
-        ],
-      ),
+          ],
+        ),
+      )
     );
   }
 

lib/ui/screens/timeline/widgets/_scrolling_viewport_controller.dart

@@ -91,6 +91,10 @@ class _ScrollingViewportController extends ChangeNotifier {
     setZoom(details.scale * _zoomOnScaleStart);
   }
 
+  void _handleScaleUpdateMouse(double scale) {
+    setZoom( Math.max(0, Math.min(1, _zoom + scale)) );
+  }
+
   /// Maintain current yr when the app changes size
   void _handleResize() => jumpToYear(_currentYr.value);
 }