Fix chart direction

Widget-Tests/ChartView/ChartView.swift

@@ -39,7 +39,7 @@ private struct _ChartView: View {
                 let normalizedData = (dataPoint - provider.minValue) / ( provider.maxValue - provider.minValue)
                 let normalizedTime = CGFloat(time) / CGFloat(provider.maxEntries)
                 
-                let targetPoint = CGPoint( x: width * normalizedTime, y: height * CGFloat(normalizedData))
+                let targetPoint = CGPoint( x: width * normalizedTime, y: height * CGFloat(1 - normalizedData))
                 
                 if drawingOptions.contains(.line) {
                     path.addLine(to: targetPoint)
@@ -92,14 +92,18 @@ struct ChartView: View {
 
 struct ChartView_Previews: PreviewProvider {
     static var previews: some View {
-        let provider = DataProvider(entries: 20, delay: 0.1, startValues: [1, 2, 3, 4, 0, 5])
-        return VStack(spacing: 10) {
+        let provider = DataProvider(entries: 20, delay: 0.1, startValues: [1, 2, 3, 4, -20, 30])
+        let stack = VStack(spacing: 10) {
             ChartView(provider: provider, options: [.line, .point])
             ChartView(provider: provider, options: .line)
             ChartView(provider: provider, options: .point)
         }
             .accentColor(.green)
             .padding()
-            .previewLayout(.sizeThatFits)
+        
+        return Group {
+            stack.environment(\.colorScheme, .light)
+            stack.environment(\.colorScheme, .dark)
+        }
     }
 }