Calculate polyline visibility based on strokeWidth

Author: braindamagedman

lib/src/layer/polyline_layer/painter.dart

@@ -48,14 +48,16 @@ class _PolylinePainter<R extends Object> extends CustomPainter
         points: projectedPolyline.points,
         shift: shift,
       );
-      if (!areOffsetsVisible(offsets)) return WorldWorkControl.invisible;
 
       final strokeWidth = polyline.useStrokeWidthInMeter
           ? metersToScreenPixels(
-              projectedPolyline.polyline.points.first,
-              polyline.strokeWidth,
-            )
+        projectedPolyline.polyline.points.first,
+        polyline.strokeWidth,
+      )
           : polyline.strokeWidth;
+
+      if (!areOffsetsVisible(offsets, strokeWidth)) return WorldWorkControl.invisible;
+
       final hittableDistance = math.max(
         strokeWidth / 2 + polyline.borderStrokeWidth / 2,
         minimumHitbox,
@@ -133,18 +135,6 @@ class _PolylinePainter<R extends Object> extends CustomPainter
           points: projectedPolyline.points,
           shift: shift,
         );
-        if (!areOffsetsVisible(offsets)) return WorldWorkControl.invisible;
-
-        final hash = polyline.renderHashCode;
-        if (needsLayerSaving || (lastHash != null && lastHash != hash)) {
-          drawPaths();
-        }
-        lastHash = hash;
-        needsLayerSaving = polyline.color.a < 1 ||
-            (polyline.gradientColors?.any((c) => c.a < 1) ?? false);
-
-        // strokeWidth, or strokeWidth + borderWidth if relevant.
-        late double largestStrokeWidth;
 
         late final double strokeWidth;
         if (polyline.useStrokeWidthInMeter) {
@@ -155,7 +145,19 @@ class _PolylinePainter<R extends Object> extends CustomPainter
         } else {
           strokeWidth = polyline.strokeWidth;
         }
-        largestStrokeWidth = strokeWidth;
+
+        if (!areOffsetsVisible(offsets, strokeWidth)) return WorldWorkControl.invisible;
+
+        final hash = polyline.renderHashCode;
+        if (needsLayerSaving || (lastHash != null && lastHash != hash)) {
+          drawPaths();
+        }
+        lastHash = hash;
+        needsLayerSaving = polyline.color.a < 1 ||
+            (polyline.gradientColors?.any((c) => c.a < 1) ?? false);
+
+        // strokeWidth, or strokeWidth + borderWidth if relevant.
+        double largestStrokeWidth = strokeWidth;
 
         final isSolid = polyline.pattern == const StrokePattern.solid();
         final isDashed = polyline.pattern.segments != null;

lib/src/layer/shared/feature_layer_utils.dart

@@ -26,7 +26,7 @@ mixin FeatureLayerUtils on CustomPainter {
   /// Determine whether the specified offsets are visible within the viewport
   ///
   /// Always returns `false` if the specified list is empty.
-  bool areOffsetsVisible(Iterable<Offset> offsets) {
+  bool areOffsetsVisible(Iterable<Offset> offsets, [double margin = 0]) {
     if (offsets.isEmpty) {
       return false;
     }
@@ -43,7 +43,12 @@ mixin FeatureLayerUtils on CustomPainter {
       if (maxX < offset.dx) maxX = offset.dx;
       if (maxY < offset.dy) maxY = offset.dy;
     }
-    return viewportRect.overlaps(Rect.fromLTRB(minX, minY, maxX, maxY));
+    return viewportRect.overlaps(Rect.fromLTRB(
+      minX - margin,
+      minY - margin,
+      maxX + margin,
+      maxY + margin,
+    ));
   }
 
   /// Perform the callback in all world copies (until stopped)