feat: snap zoom to 1.0x (#1211)

lib/components/canvas/canvas_gesture_detector.dart

@@ -328,6 +328,8 @@ class CanvasGestureDetectorState extends State<CanvasGestureDetector> {
     }
   }
 
+  Timer? _snapZoomTimer;
+
   /// Corrects the transform if it's out of bounds.
   /// If the scale is less than 1, centers the pages horizontally.
   /// Otherwise, prevents the user from scrolling past the edges.
@@ -338,14 +340,19 @@ class CanvasGestureDetectorState extends State<CanvasGestureDetector> {
     double adjustmentX = 0;
     double adjustmentY = 0;
 
-    // horizontally center pages if zoomed out
+    // snap to 1.0x zoom
+    _snapZoomTimer?.cancel();
+    final diffFrom1 = (scale - 1).abs();
+    // allow 0.001 leeway for floating point error
+    if (diffFrom1 < 0.05 && diffFrom1 > 0.001)
+      _snapZoomTimer = Timer(const Duration(milliseconds: 200), resetZoom);
+
     if (scale < 1) {
+      // horizontally center pages if zoomed out
       final center = containerBounds.maxWidth * (1 - scale) / 2;
       adjustmentX = center - translation.x;
-    }
-
-    // if zoomed in, don't allow scrolling past the edges
-    else {
+    } else {
+      // if zoomed in, don't allow scrolling past the edges
       late final minX = containerBounds.maxWidth * (1 - scale);
       if (translation.x > 0) {
         adjustmentX = -translation.x;